JP4887266B2 - Flattening method - Google Patents

Description

The present invention relates to a planarization how, in particular and simple substrate made of SiC or GaN, bonded substrate (epitaxial substrate) carrying the SiC or GaN, the workpiece such as a substrate used for MEMS (micro electro mechanical system) about the flattening how to process flat remove the processing surface (surface) of the object.

  In recent years, as semiconductor devices are highly integrated, circuit wiring is becoming finer and the distance between wirings is becoming narrower. In particular, in the case of photolithography having a line width of 0.5 μm or less, the depth of focus becomes shallow, so that the flatness of the imaging surface of the stepper is required. As one means for flattening the surface of such a semiconductor substrate, a CMP apparatus that performs chemical mechanical polishing (CMP) is known.

On the other hand, the importance of SiC, GaN, etc. is increasing as a semiconductor device material. As a new processing method that removes the surface of SiC and GaN with high accuracy and flatness, catalyst-based etching (catalyst referred to) that removes the surface of the workpiece by etching using a catalytic action capable of chemical reaction. Etching: CARE) method has been proposed. In this CARE method, for example, a workpiece is placed in a treatment liquid made of hydrohalic acid such as hydrofluoric acid, and a catalyst made of platinum, gold, or a ceramic solid catalyst is placed on the surface of the workpiece (work surface). ) In contact with or in close proximity to the surface of the catalyst, and eluting halogen compounds generated by chemical reaction between halogen radicals generated by molecular dissociation of hydrogen halide on the surface of the catalyst and surface atoms of the workpiece. Thus, the surface of the workpiece is removed (etched) (see, for example, Patent Document 1).
JP 2006-114632 A

  The CARE method, which performs surface removal processing (etching) of a workpiece such as SiC or GaN, removes the surface of the workpiece (processing surface) with higher accuracy than conventional processing methods such as CMP. Thus, a processed surface having excellent flatness can be obtained, and the processed surface has excellent characteristics such that no damage is left on the processed surface. However, in the CARE method, for example, a halogen compound generated by a chemical reaction between a halogen radical and a surface atom of the workpiece is eluted in the treatment liquid, and the workpiece surface is removed (etched). The processing speed is considerably slower than grinding, CMP and the like widely used in the manufacture of semiconductor devices, and it is therefore difficult to improve the throughput.

The present invention has been made in view of the above circumstances. By extending the advantages of the CARE method and complementing the disadvantages of the CARE method, the processing surface of the workpiece after processing is secured while ensuring a sufficient processing speed. and to provide a flattened how you can perform the surface removal processing with enhanced flatness of the processed surface without leaving damage.

The invention according to claim 1 is a flattening method for flatly removing a workpiece surface made of SiC or GaN of a workpiece, and the workpiece surface of the workpiece by grinding, lapping or CMP. An initial surface removal step is performed to improve the flatness of the processed surface by processing the surface of the workpiece, and the processed surface of the workpiece after the initial surface removal step is cleaned with hydrofluoric acid cleaning or pure water cleaning. hydrohalic acids, arranged workpiece hydrogen peroxide or ozone water or Ranaru processing liquid, at least the surface of platinum, gold, ceramic-based solid catalyst, transition metals, and glass-based metal oxide A final surface removal step is performed by catalyst-based etching in which the surface of the catalyst platen made of only one is brought into contact with or in close proximity to the work surface of the work piece and the work surface is processed to be flat without damage, After the final surface removal process The treated surface of the polished, SPM cleaning, aqua regia cleaning, and a planarization method characterized by washing with at least one of hydrofluoric acid cleaning.

  Here, the surface removal step is a step of removing the surface portion of the substrate, which is a workpiece, and the cleaning step is particulate contamination, organic matter contamination, This is a process for removing metal contamination. The step of removing the oxide film on the surface of the work piece remaining after the surface removal step is also included in the cleaning step.

  Thereby, after improving the flatness of the work surface (surface) of the work piece through one or more surface removal processes, the surface of the work piece (work surface) is highly accurate in the final surface removal process. By performing CARE that can be removed evenly, the final processed surface with excellent flatness and no damage is created at a sufficient processing speed while gradually increasing the flatness of the processed surface of the workpiece. be able to.

The invention according to claim 2 is the planarization method according to claim 1, wherein a wettability improving agent for improving the wettability of the catalyst surface plate is further added to the treatment liquid. .
The invention according to claim 3 is the planarization method according to claim 2, wherein the wettability improver is nitric acid or ethanol.

  When hydrofluoric acid is used as the treatment liquid and platinum is used as the catalyst, the platinum surface has poor wettability to hydrofluoric acid, so the treatment liquid (hydrofluoric acid) is efficiently used on the catalyst surface, which is the processing reference surface. Supply becomes difficult. In such a case, the treatment liquid can be efficiently supplied to the catalyst surface by mixing the wettability improver with hydrofluoric acid as the treatment liquid. Examples of the wettability improver preferably used include nitric acid and ethanol.

  A fourth aspect of the present invention is the flattening method according to any one of the first to third aspects, wherein a pH adjusting buffer is further added to the treatment liquid.

The invention according to claim 5 is the planarization method according to any one of claims 1 to 4, wherein an organic alcohol or an inorganic acid is further added to the treatment liquid.
Examples of the organic alcohol include methanol and ethanol, and examples of the inorganic acid include sulfuric acid and nitric acid.

According to the sixth aspect of the present invention, a change in the current value of a drive motor that rotationally drives the catalyst surface plate, a change in the concentration of the processing liquid, a measurement result when the processing surface is measured by an optical monitor, and a processing target 6. The flattening method according to claim 1 , wherein an end point of the final surface removal step is detected by any of mass changes before and after processing of the object .
Be added a small amount of acid or base treatment solution may be added pH of the treatment solution is not to change the buffer to the processing solution. In particular, when processing GaN, Ga ₂ O _3, which is an oxide of GaN, has solubility in acids or bases, so that the pH of the treatment liquid is set to around 7, and dissolution of Ga ₂ O _{3 in} the treatment liquid is performed. Need to prevent. The pH of the treatment liquid can be adjusted by adding a buffer adjusted in pH to the treatment liquid. Further, buffering agents, it generated H ⁺ ions and OH ^- for having the property that consumes ions, H ⁺ ions and OH in a solid acidic catalyst and a basic catalyst near ^- it is possible to shorten the active length of the ion. As a result, the workpiece can be processed more flatly by allowing H ⁺ ions or OH ⁻ ions to exist only in the immediate vicinity of the solid catalyst.

In the present invention, although the processing accuracy is not so high, the processing speed is relatively fast, surface removal processing is performed by grinding or lapping, and light irradiation catalyst that involves light irradiation in CMP or catalyst-based etching as necessary After performing the reference etching, by performing the catalyst reference etching as the final surface removal step, for example, the processing surface (surface) of the workpiece having relatively large initial unevenness can be obtained in a desired flatness in a shorter time. It can be flattened. Examples of the grinding include electrolytic in-process dressing (ELID) mirror grinding.

  Light irradiation catalyst reference etching accompanied by light irradiation in CMP or catalyst reference etching can perform surface removal processing with an increased processing speed, although the flatness of the processed surface after processing is inferior to catalyst reference etching. Therefore, the overall processing speed can be increased by performing the catalyst reference etching after the light irradiation catalyst reference etching accompanied by light irradiation in the CMP or the catalyst reference etching.

  For example, when platinum contamination occurs on the processed surface of the workpiece, aqua regia cleaning is performed. When metal contamination other than noble metal occurs on the processed surface of the workpiece or organic contamination occurs, SPM cleaning is performed. When an oxide film is generated on the surface of the workpiece, the processing surface of the workpiece can be cleaned by cleaning with hydrofluoric acid.

  According to the present invention, after improving the flatness of the work surface (surface) of the work piece, CARE that can remove the work surface (work surface) with high accuracy and flatness in the final surface removal step. (Catalyst-based etching) to create a final processed surface with excellent flatness and no damage at a sufficient processing speed while gradually increasing the flatness of the processed surface of the workpiece. Can do. As a result, the throughput can be improved while fully utilizing the advantages of the CARE method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following example, hydrofluoric acid (HF) is used as a treatment liquid, and platinum is used as a catalyst to remove and process the surface (surface to be processed) of a substrate such as a SiC wafer to a desired flatness. An example will be described.

FIG. 1 is a plan view showing the overall configuration of a planarization apparatus used in the present invention. As shown in FIG. 1, flattening device this comprises a substantially rectangular housing 1, the interior of the housing 1, the partition walls 1a, 1b, by 1c, load / unload unit 2 and the surface removal processing It is divided into a section 3 and a cleaning section 4. The load / unload unit 2, the surface removal processing unit 3, and the cleaning unit 4 are independently assembled and evacuated independently.

  The load / unload unit 2 includes two or more (three in this embodiment) front load units 20 on which substrate cassettes for stocking a large number of substrates (workpieces) are placed. These front load portions 20 are arranged adjacent to each other in the width direction (direction perpendicular to the longitudinal direction) of the flattening device. The front load unit 20 can be equipped with an open cassette, a SMIF (Standard Manufacturing Interface) pod, or a FOUP (Front Opening Unified Pod). Here, SMIF and FOUP are sealed containers that can maintain an environment independent of the external space by accommodating a substrate cassette inside and covering with a partition wall.

  In addition, a traveling mechanism 21 is laid along the front load section 20 in the load / unload section 2, and the first transport mechanism that can move along the arrangement direction of the substrate cassettes on the traveling mechanism 21. The first transfer robot 22 is installed. The first transfer robot 22 can access the substrate cassette mounted on the front load unit 20 by moving on the traveling mechanism 21. The first transfer robot 22 has two hands on the upper and lower sides. For example, the upper hand is used when returning the substrate to the substrate cassette, and the lower hand is used when transferring the unprocessed substrate. By doing so, you can use the upper and lower hands properly.

  Since the load / unload unit 2 is an area where it is necessary to maintain the cleanest state, the inside of the load / unload unit 2 is higher than any of the outside of the apparatus, the surface removal processing unit 3 and the cleaning unit 4. Always maintained at pressure. In addition, a filter fan unit (not shown) having a clean air filter such as a HEPA filter or a ULPA filter is provided above the traveling mechanism 21 of the first transfer robot 22. The clean air from which the gas has been removed is constantly blowing downward.

  The surface removal processing unit 3 is a region where the substrate surface (surface to be processed) is removed. In this example, the lapping unit 30A as a first surface removal processing unit and the CMP unit 30B as a second surface removal processing unit. And two catalyst reference etching (CARE) units 30C and 30D as third surface removal processing units (final surface removal processing units). These wrapping unit 30A, CMP unit 30B, and CARE units 30C, 30D are arranged along the longitudinal direction of the planarization apparatus, as shown in FIG.

  The wrapping unit 30A includes a surface plate 300A having a wrapping surface on the surface, a top ring 301A for holding the substrate detachably and pressing the surface plate 300A, a diamond slurry, a colloidal silica slurry, etc. on the surface plate 300A. A wrap liquid supply nozzle 302A for supplying the lap liquid and a pure water supply nozzle 303A for supplying pure water to the surface of the surface plate 300A. At the time of lapping of the lapping unit 30A, lapping liquid (slurry) is supplied from the lapping liquid supply nozzle 302A onto the surface plate 300A, and the substrate as a workpiece is held by the top ring 301A and pressed toward the surface plate 300A. Wrapping of the substrate surface is performed.

  The lapping unit (first surface removal processing unit) 30A, for example, improves the flatness of the substrate surface while mainly obtaining a processing amount when flattening the substrate surface having relatively large initial unevenness to a desired flatness. For example, when the substrate surface does not have relatively large initial unevenness, it can be omitted. In this example, the wrapping unit 30A is used as the first surface removal processing unit, but instead of the wrapping unit 30A, a grinding unit, such as an electrolytic in-process dressing, which can significantly increase the processing amount than the CARE units 30C and 30D. (ELID) A mirror grinding unit may be used.

  The CMP unit (second surface removal processing unit) 30B includes a polishing table 300B having a polishing surface, a top ring 301B for holding the substrate in a detachable manner and polishing while pressing against the polishing table 300B, and a polishing table 300B. A polishing liquid supply nozzle 302B for supplying a polishing liquid or a dressing liquid (for example, water) to the surface, a dresser 303B for dressing the polishing surface of the polishing table 300B, a liquid (for example, pure water), and a gas (for example, nitrogen). ) And an atomizer 304B that sprays the mixed fluid from one or a plurality of nozzles onto the polishing surface of the polishing table 300B.

  A polishing cloth or a grindstone (fixed abrasive) or the like is affixed to the upper surface of the polishing table 300B of the CMP unit 30B, and a polishing surface for polishing the substrate surface is configured by the polishing cloth or the grindstone (fixed abrasive) or the like. Yes. At the time of polishing by the CMP unit 30B, the polishing liquid is supplied from the polishing liquid supply nozzle 302B to the polishing surface on the polishing table 300B, and the substrate, which is a workpiece, is held by the top ring 301B and pressed toward the polishing surface. Surface polishing is performed.

  The CMP unit (second surface removal processing unit) 30B is for increasing the flatness of the substrate surface while increasing the processing speed and increasing the processing amount as compared with the CARE units 30C and 30D. In combination with the lapping unit (first surface removal processing unit) 30A, it is efficient to flatten the substrate surface having relatively large initial irregularities to a desired flatness, but may be omitted.

  In this example, a CMP unit is used as the second surface removal processing unit. However, instead of the CMP unit, the CARE units 30C and 30D configured as shown in FIGS. 2 to 4 below are held by the substrate holder. A light source that emits light, preferably ultraviolet rays, toward the surface of the substrate is provided. When removing the substrate surface, the substrate surface is irradiated with light to activate the substrate surface, thereby increasing the processing speed compared to the CARE unit. Alternatively, a light irradiation catalyst substrate unit (light irradiation CARE unit) may be used. Further, a light irradiation catalyst substrate unit (light irradiation CARE unit) shown in FIG. 13 may be used.

  As shown in detail in FIG. 2, the CARE units (third surface removal processing units) 30C and 30D include a treatment tank 124, a catalyst surface plate 126 rotatably disposed in the treatment tank 124, and a surface (covered). A substrate holder 130 for holding the substrate (workpiece) 128 detachably with the processing surface facing downward is provided. The substrate holder 130 is made of, for example, SiC having excellent processability, chemical resistance, and temperature resistance, but may be made of hard vinyl chloride or PEEK material. It is connected to the tip of a rotary shaft 132 that can be moved up and down and provided in a parallel and eccentric position. Since the substrate holder 130 is pivot-supported (ball bearing supported) with respect to the rotation shaft 132, the substrate holding surface of the substrate holder 130 can follow the surface of the catalyst surface plate 126, and the workpiece 128 can be moved. The catalyst surface plate 126 can be brought into surface contact.

  In this example, since the surface removal processing of the substrate 128 such as an SiC wafer is performed by the CARE units 30C and 30D, for example, hydrofluoric acid (50% HF) is used as the processing liquid, A material in which platinum 142 having a thickness of 1 mm as a catalyst is attached to the surface of a substrate 140 made of molybdenum having a thickness of 28 mm is used. The catalyst surface plate 126 may be made of molybdenum or a molybdenum alloy without providing platinum as a catalyst, and the catalyst surface plate 126 itself may be used as a catalyst. A hydrohalic acid other than hydrofluoric acid, such as hydrochloric acid, may be used.

  Moreover, it is preferable to use what added the wettability improvement agent which improves the wettability of the catalyst surface plate surface as a process liquid. A wettability improver is a substance having a hydrophilic group and a hydrophobic group in the same molecule. By adding a wettability improver to the treatment liquid, the wettability of the catalyst platen to the treatment liquid can be improved. . Thereby, the supply efficiency of the process liquid between a board | substrate (to-be-processed object) and a catalyst surface plate improves, and the stable surface removal process can be performed.

A pH adjusting buffer may be further added to the treatment liquid. Thereby, pH of a process liquid can be adjusted and it can suppress that a board | substrate (processed object) melt | dissolves in a process liquid except a removal process reaction part. In addition, H ⁺ ions and OH ⁻ ions, which are active species generated on the surface of the catalyst platen, can be quickly deactivated, and the removal processing reaction can be limited to the immediate vicinity of the surface of the catalyst platen. The flatness of the processed surface of the substrate (workpiece) after processing can be improved.

  An organic alcohol such as methanol or ethanol, or an inorganic acid such as sulfuric acid or nitric acid may be added to the treatment liquid. F atoms and OH radicals generated on the surface of the catalyst platen are very active, have a short survival time, and are immediately deactivated. For this reason, a sufficient processing speed may not be obtained. In such a case, by adding an alcohol such as ethanol or an inorganic acid such as nitric acid to the treatment liquid and reacting with F atoms or OH radicals, organic radicals or nitric acid having a longer survival time than F atoms or OH radicals. Radicals are generated secondarily, and the processing speed can be improved.

In addition, you may add said processing agent (wetability improvement agent, pH adjuster, organic alcohol, inorganic acid) to a process liquid 1 type or in combination of 2 or more types.
Furthermore, a buffering agent (buffer solution) that prevents the pH of the processing solution from changing may be added to the processing solution.

  Inside the substrate holder 130, a heater 170 as a temperature control mechanism for controlling the temperature of the substrate 128 held by the holder 130 is embedded in the rotating shaft 132. A processing liquid supply nozzle 174 that supplies a processing liquid (hydrofluoric acid) controlled to a predetermined temperature by a heat exchanger 172 as a temperature control mechanism to the inside of the processing tank 124 is disposed above the processing tank 124. Yes. Further, a fluid flow path 176 as a temperature control mechanism for controlling the temperature of the catalyst surface plate 126 is provided inside the catalyst surface plate 126.

  In this example, the heater 170 as a temperature control mechanism for controlling the temperature of the substrate 128, the heat exchanger 172 as a temperature control mechanism for controlling the temperature of the processing liquid, and the temperature control for controlling the temperature of the catalyst surface plate 126. Although an example in which the fluid flow path 176 as a mechanism is provided is shown, all of these temperature control mechanisms may be omitted, or one of them may be provided.

  As is known from the Arrhenius equation, the higher the reaction temperature, the higher the chemical reaction. Therefore, by controlling at least one of the temperatures of the workpiece 128, the treatment liquid, and the catalyst surface plate 126 to control the reaction temperature, the stability of the processing speed can be improved while changing the processing speed. it can.

On the surface of the platinum (catalyst) 142 of the catalyst surface plate 126, as shown in FIGS. 3 and 4, a plurality of grooves 144 are concentrically formed across the three groove forming portions 146a, 146b, 146c. Yes. In this example, three groove forming portions 146 a, 146 b, and 146 c are provided, and the width of the groove forming portion 146 b located at the center is set smaller than the diameter of the substrate 128 held by the substrate holder 130. As a result, both ends of the substrate 128 held by the substrate holder 130 are positioned on the flat portions sandwiched between the groove forming portions 146a and 146b and the groove forming portions 146b and 146c, respectively, and are held and rotated by the substrate holder 130. Further, the end of the substrate 128 is not caught in the groove 144. Further, when the thickness of the platinum (catalyst) 142 is reduced, the depth of the groove to be formed is necessarily reduced, but when the groove width, depth, pitch, etc. are reduced, the fluidity of the fluid is reduced. Deteriorates and the suction (adsorption) force generated between the substrate and the catalyst increases.
Therefore, it is desirable to make the groove depth D as shallow as possible with an acceptable adsorption force.

  Further, as indicated by phantom lines in FIG. 3, for example, when a substrate holder having a retainer ring 148 surrounding the periphery of the substrate 128 is used, both ends of the retainer ring 148 are formed on the groove forming portions 146 a and 146 c on both sides. The entire width of the groove forming portions 146a, 146b, and 146c is set to be smaller than the diameter of the retainer ring 148 so that the rotating retainer ring 148 located on the outer flat portion is not caught by the groove 144. . In this example, the groove 144 is formed not in a square shape but in an R shape as shown in FIG. 4 in order to prevent the end portion of the substrate 128 from being caught. The groove may have an arbitrary tapered shape.

  In order to efficiently supply the treatment liquid to the contact portion (processing portion) between the catalyst surface plate 126 and the substrate 128, it is preferable to make the pitch of the grooves 144 (groove pitch) as fine as possible. In this example, as shown in FIG. 4, the groove pitch P is set to about 3 mm to 5 mm, and the groove depth D is set to about 0.5 mm to 1.0 mm. The groove depth D is preferably as shallow as possible so that no sticking occurs in order to reduce the thickness of the platinum 142 as the catalyst. As in this example, when a large number of grooves 144 are provided concentrically on the surface of the platinum (catalyst) 142 of the catalyst surface plate 126, the substrate 128 can be swung by the substrate holder 130. It is preferable for improving the internal uniformity. The concentric groove shape may be eccentric, or the spiral groove shape may be used.

  Thus, the processing liquid (hydrofluoric acid) is supplied from the processing liquid supply nozzle 174 toward the catalyst surface plate 126. Then, the processing liquid is held in a groove 144 provided on the surface of the catalyst surface plate 126. Then, the substrate (workpiece) 128 held by the substrate holder 130 is pressed against the surface of the platinum (catalyst) 142 of the catalyst surface plate 126 with a predetermined pressure, and the substrate 128 is contacted with the platinum (catalyst) 142 of the catalyst surface plate 126. The catalyst surface plate 126 and the substrate 128 are rotated while the processing liquid is interposed in the contact portion (processing portion), and the surface (lower surface) of the substrate 128 made of SiC wafer or the like is removed flatly (etched). The substrate 128 is held in close proximity to the platinum (catalyst) 142 without pressing the substrate 128 held by the substrate holder 130 against the platinum (catalyst) 142 of the catalyst surface plate 126 with a predetermined pressure. The removal process (etching) may be performed flat.

  When using a substrate holder having a retainer ring 148 for preventing substrate jump-out, the material of at least the portion of the retainer ring 148 facing the catalyst platen 126 is the surface of the catalyst platen 126 used. It is preferable to use the same material. For example, when platinum is used as the surface material (catalyst) of the catalyst surface plate 126, the material of the portion of the retainer ring 148 that contacts the surface of the catalyst surface plate 126 is platinum. For example, when iron is used as the surface material of the catalyst surface plate, the material of the portion of the retainer ring that contacts the catalyst surface plate is iron.

  Thus, even when the surface material of the retainer ring 148 is scraped off due to abrasion with the catalyst surface plate 126 and adheres to the surface of the catalyst surface plate 126, the processing can be continued without losing the catalytic effect of the catalyst surface plate 126. it can. The surface material of the retainer ring 148 may be an alloy containing much of the same metal as the surface material of the catalyst surface plate 126. For example, when iron is used as the surface material of the catalyst surface plate, the surface material of the retainer ring may be carbon steel or stainless steel, which is an alloy containing a large amount of iron.

  As shown in FIGS. 5 and 6, for example, a catalyst surface plate 200 having a large number of through holes 200a is provided in a region in contact with a substrate (workpiece) 128 that is held and processed by the substrate holder 130 shown in FIG. May be used. For example, similar to the above-described catalyst platen 126, the catalyst platen 200 has platinum as a catalyst attached to the surface of a base material made of molybdenum.

  In this example, a plurality of through holes 200a are formed in the catalyst surface plate 200 at equally spaced lattice positions. The lattice spacing is, for example, 5 mm, and the diameter of the through hole 200a is, for example, 1 mm. The lattice spacing and hole diameter of the through holes 200a are preferably as small as possible. As described above, by uniformly providing the plurality of through holes 200a in the catalyst surface plate 200, the entire surface of the substrate (workpiece) 128 can be processed uniformly.

  A concave portion 200 b is formed on the lower surface of the catalyst surface plate 200, and the treatment liquid pool 204 is formed between the catalyst surface plate 200 and the rotating body 202 by attaching the catalyst surface plate 200 to the upper surface of the rotating body 202. Is formed. Furthermore, the center of the catalyst surface plate 200 penetrates up and down, and a rotary joint 206 is attached thereto. The rotary joint 206 is connected to, for example, a processing liquid supply nozzle 174 shown in FIG.

  According to this example, while rotating the catalyst surface plate 200 together with the rotating body 202, the processing liquid is supplied to the processing liquid reservoir 204 between the catalyst surface plate 200 and the rotating body 202 through the rotary joint 206, and the through hole 200a. Processing is performed so that the processing liquid is ejected from Thereby, it is possible to replace the processing liquid accumulated in the through hole 200a while suppressing the substrate (workpiece) 128 from sticking to the catalyst surface plate 200.

  The ejection pressure when the processing liquid is ejected from the through hole 200 a is preferably sufficiently lower than the pressure for pressing the substrate (workpiece) 128 against the catalyst surface plate 200. In consideration of the strength of the catalyst platen, a radial groove may be formed from the center of the catalyst platen, and the treatment liquid may be supplied to the lower part of the through hole through this groove.

  As shown in FIG. 1, the CARE units 30C and 30D are directed toward the surface of the platinum (catalyst) 142, which is the surface of the catalyst surface plate 126, while generating cavitation or applying ultrasonic waves as necessary. A pure water injection nozzle 150 is disposed as a conditioning unit that injects pure water to condition the surface. In addition, light is directed toward the catalyst platen and photoelectrochemical etching is used to remove fragments and organic contamination from the surface of the catalyst platen, or an electrode is placed opposite the catalyst platen to face the catalyst platen. The conditioning unit may be configured by an electrolytic removal apparatus that electrolytically removes fragments on the surface of the catalyst plate or organic contamination by applying a voltage between the electrodes. The fragments separated from the catalyst surface plate 126 are removed by, for example, filtration (filter or the like).

  Between the wrapping unit 30A and the CMP unit 30B and the cleaning section 4, there are four transport positions along the longitudinal direction (first transport position TP1, second transport position TP2, first transport position TP2 in order from the load / unload section 2 side). A first linear transporter 5 is disposed as a second (linear motion) transport mechanism for transporting the substrate between the third transport position TP3 and the fourth transport position TP4. A reversing machine 31 for reversing the substrate received from the first transport robot 22 of the load / unload unit 2 is disposed above the first transport position TP1 of the first linear transporter 5, and below that is disposed. A lifter 32 that can be moved up and down is arranged. Also, a pusher 33 that can be moved up and down below the second transfer position TP2, a pusher 34 that can be moved up and down below the third transfer position TP3, and a pusher 34 that can move up and down below the fourth transfer position TP4. Possible lifters 35 are respectively arranged.

  At the side of the CARE units 30C and 30D, adjacent to the first linear transporter 5, there are three transfer positions along the longitudinal direction (the fifth transfer position TP5, the sixth transfer position in order from the load / unload unit 2 side). A second linear transporter 6 serving as a second (linear motion) transport mechanism for transporting the substrate between the transport position TP6 and the seventh transport position TP7 is disposed. A lifter 36 that can be moved up and down below the fifth transport position TP5 of the second linear transporter 6, a pusher 37 below the sixth transport position TP6, and a pusher 38 below the seventh transport position TP7. Are arranged respectively. Further, a pure water replacement section 160 having a ridge and a pure water nozzle is provided between the CARE unit 30C and the pusher 37, and a pure water replacement section 160 having a ridge and a pure water nozzle is also provided between the CARE unit 30D and the pusher 38. A water replacement part 162 is arranged.

  As can be seen from the use of slurry or the like during the surface removal processing, the surface removal processing portion 3 is the most dirty (dirty) region. Therefore, in this embodiment, exhaust is performed from the periphery of the removal processing unit such as a surface plate so that the particles in the surface removal processing unit 3 are not scattered outside, and the pressure inside the surface removal processing unit 3 is reduced. Further, the scattering of particles is prevented by making the pressure outside the apparatus, the surrounding cleaning unit 4 and the load / unload unit 2 negative. Usually, an exhaust duct (not shown) is provided below the removal processing section such as a surface plate, and a filter (not shown) is provided above, and the exhaust duct and the filter are used for cleaning. Air is blown out and a down flow is formed.

  The cleaning unit 4 is an area for cleaning a substrate, and includes a second transfer robot 40, a reversing machine 41 for inverting the substrate received from the second transfer robot 40, and three cleaning units 42, 43, 44 for cleaning the substrate. And a dry unit 45 for rinsing the cleaned substrate with pure water and spin-drying, and a third transport unit for transporting the substrate between the reversing machine 41, the cleaning units 42, 43, 44 and the drying unit 45. A robot 46 is provided. The second transfer robot 40, the reversing machine 41, the cleaning units 42 to 44, and the drying unit 45 are arranged in series along the longitudinal direction, and the second transfer robot 40, the reversing machine 41, and the cleaning units 42 to 44 are arranged. And the 3rd conveyance robot 46 is arrange | positioned so that driving | running | working is possible between the drying unit 45 and the 1st linear transporter 5. FIG. A filter fan unit (not shown) having a clean air filter is provided above the cleaning units 42 to 44 and the drying unit 45, and clean air from which particles are removed by this filter fan unit is always below. It is blowing out towards. Further, the inside of the cleaning unit 4 is always maintained at a pressure higher than that of the surface removal processing unit 3 in order to prevent inflow of particles from the surface removal processing unit 3.

  In this example, as the first and second cleaning units 42 and 43, there are chemical cleaning units for cleaning the substrate by immersing the substrate in a chemical solution such as aqua regia, SPM (hydrogen sulfate aqueous solution) or hydrofluoric acid. Used as the third cleaning unit 44 is a pure water cleaning unit that supplies pure water toward the substrate to clean the substrate. Specifically, a cleaning unit that cleans the substrate with hydrofluoric acid is used as the first cleaning unit 42, and a cleaning unit that cleans the substrate with aqua regia is used as the second cleaning unit 43.

  As shown in FIG. 1, the partition wall 1 a surrounding the surface removal processing unit 3 is provided with a shutter 10 positioned between the reversing machine 31 and the first transfer robot 22. 10 is opened, and the substrate is transferred between the first transfer robot 22 and the reversing machine 31. The partition wall 1b surrounding the surface removal processing unit 3 is provided with a shutter 13 located at a position facing the CMP unit 30B and a shutter 14 located at a position facing the CARE unit 30C.

  Next, a process for flattening the surface of the substrate using the flattening apparatus having such a configuration will be described.

  One substrate is taken out from the substrate cassette mounted on the front load unit 20 by the first transfer robot 22 and transferred to the reversing machine 31. The reversing device 31 reverses the substrate by 180 ° and then places the substrate on the lifter 32 at the first transport position TP1. The wrapping unit 30A receives the substrate from the lifter 32 by the top ring 301A and wraps the substrate surface. That is, in the wrapping unit 30A, for example, while supplying a lapping liquid such as diamond slurry or colloidal silica slurry to the surface plate 301A, the substrate surface is removed by about 10 μm at a processing speed of, for example, several tens of μm / h or less. Wrapping to improve the flatness. In this case, the damage depth after processing on the substrate surface is about 1 μm. Then, the substrate surface is rinsed with pure water as necessary.

  The substrate after lapping is delivered to the pusher 33 at the second transport position TP2, and is transported to the third transport position TP3 as the first linear transporter 5 moves laterally. Then, at the third transport position TP3, the CMP unit 30B receives the substrate from the pusher 34 by the top ring 301B and performs CMP on the surface of the substrate. That is, in the CMP unit 30B, for example, while supplying a polishing liquid having colloidal silica to the polishing table 300B, the substrate surface is removed by about several μm at a processing speed of, for example, several μm / h or less, thereby improving the flatness of the substrate surface. Further improving CMP is performed. In this case, the damage depth after processing on the substrate surface is about 10 nm. Then, the substrate surface is rinsed with pure water as necessary.

  The substrate after CMP is transferred to the lifter 35 at the fourth transport position TP4. The second transfer robot 40 receives the substrate from the lifter 35 and transfers it to the reversing machine 41. Then, the reversing machine 41 reverses the substrate by 180 °, and then transports the substrate to the first cleaning unit (chemical cleaning unit) 42. The first cleaning unit 42 performs hydrofluoric acid cleaning of the substrate, for example, by immersing the substrate in hydrofluoric acid. The substrate after the hydrofluoric acid cleaning is transferred to the third cleaning unit (pure water cleaning unit) 45 by the third transfer robot 46, washed with pure water, and then returned to the reversing machine 41 by the third transfer robot 46. . When there is no need for chemical cleaning of the substrate, the substrate that has been inverted 180 ° by the reversing machine is transported to the third cleaning unit (pure water cleaning unit) 45 by the third transport robot 46 and cleaned with pure water. The third transfer robot 46 returns to the reversing machine 41. The reversing machine 41 reverses the substrate by 180 °.

  The second transfer robot 40 receives the reversed substrate from the reversing machine 41 and places it on the lifter 36 at the fifth transfer position TP5. The second transporter 6 moves laterally and transports the substrate on the lifter 36 to one of the sixth transport position TP6 or the seventh transport position TP7. The CARE unit 30C receives the substrate from the pusher 37 with the substrate holder 130, and the CARE unit 30D receives the substrate from the pusher 38 with the substrate holder 130, and performs CARE (catalyst reference etching) processing. That is, in the CARE units 30C and 30D, for example, while supplying a treatment liquid made of hydrofluoric acid to the catalyst surface plate 126, the catalytic action of the platinum 142 provided on the surface of the catalyst surface plate 126 with respect to SiC is used, for example. CARE processing for removing the substrate surface by about several tens of nm is performed at a processing speed of 100 nm / h or less. In this case, the damage depth after processing on the substrate surface is zero.

  Then, in the substrate subjected to CARE processing by the CARE unit 30C, hydrofluoric acid remaining on the surface of the substrate after CARE processing is replaced with pure water by the pure water replacement unit 160 and returned to the sixth transport position TP6. In the substrate that has been subjected to CARE processing by the CARE unit 30D, the hydrofluoric acid remaining on the substrate surface after the CARE processing is replaced with pure water by the pure water replacement unit 162 and returned to the seventh transport position TP7. Thereafter, the substrate after the replacement with pure water is moved to the fifth transport position TP5 by moving the second transporter 6 laterally. When the hydrofluoric acid is attached to the surface of the substrate after CARE processing, the substrate surface may be roughened when light of an excitation wavelength hits it. In such a case, it is desirable to attach a UV blocking film to the window of the conveyance path from the CARE unit 30C to the pure water replacement unit 160 and from the CARE unit 30D to the pure water replacement unit 162.

  The second transfer robot 40 takes out the substrate from the fifth transfer position TP5 and transfers it to the reversing machine 41. The reversing machine 41 reverses the substrate by 180 ° and then transports the substrate to the first cleaning unit. The third transport unit 46 transports the substrate from the first cleaning unit 42 to the second cleaning unit 43, where the substrate is immersed in aqua regia for cleaning, and a substrate aqua regia cleaning is performed a plurality of times as necessary. Do.

  Then, the third transport robot 46 transports the substrate after the aqua regia cleaning to the third cleaning unit (pure water cleaning unit) 44, where the substrate is cleaned with pure water, and then transported to the drying unit 45. Here, after rinsing the substrate with pure water, the substrate is rotated at a high speed and spin-dried. The first transfer robot 22 receives the substrate after spin drying from the drying unit 45 and returns it to the substrate cassette mounted on the front load unit 20.

  As CARE machining end point detection methods by the CARE units 30C and 30D, (a) a method for detecting the end point from the processing time, and (b) a method for detecting the end point from a change in the current value of the drive motor that drives the catalyst surface plate to rotate. (C) A method for detecting the end point from the change in the concentration of the processing solution, (d) A method for detecting the end point by measuring the processing surface with an in-situ optical monitor (for example, a photoluminescence measuring method), (e) The substrate is taken out from the processing solution, and the end point is inspected using equipment such as TEM (in-line or ex-situ). (G) The end point is detected from the change in the weight of the substrate (workpiece) before and after processing. The method of doing is mentioned. In addition, in the case of a substrate such as a SiC wafer on which a pattern is formed, the SEM may be used. When the crystallinity of the surface after processing is important, photoluminescence measurement that can confirm the crystallinity is preferable. Since photoluminescence measurement can be performed at atmospheric pressure, it is easy to handle.

  According to this example, the lapping unit 30A as the first surface removal processing unit performs lapping processing for removing the substrate surface by about 10 μm at a processing speed of, for example, several tens of μm / h or less to improve the flatness of the substrate surface. (Damage depth after processing on the substrate surface is about 1 μm), by the CMP unit 30B as the second surface removal processing unit, the substrate surface is removed about several μm at a processing speed of several μm / h or less, for example. CMP for further improving the flatness is performed (damage depth after processing on the substrate surface is about 10 nm), and then, for example, 100 nm by the CARE unit 30C or 30D as the third surface removal processing unit (final surface removal processing unit). The surface of the substrate is removed by about several tens of nanometers at a processing speed of / h or less. CARE processing is performed (the damage depth after processing on the substrate surface is zero).

  This makes it possible to create a final processed surface that has excellent flatness and no damage at a sufficient processing speed, while gradually increasing the flatness of the surface (processed surface) of the substrate (workpiece). it can. In this case, depending on the type and processing state of the workpiece, one of lapping (first surface removal) or CMP (second surface removal) may be omitted.

  When SiC is processed by CARE, C (carbon) is eluted in the treatment liquid after use, and it is necessary to treat the carbon. As the carbon treatment method, the treatment solution after use is irradiated with UV in the position opposite to the substrate holder of the catalyst platen and / or in the circulation line to break the chemical bond, and the carbon is deposited in another place. The method of reducing the carbon concentration of the inside processing liquid is mentioned. In addition, it is preferable to install a filter in the processing liquid circulation line or piping to filter components that adversely affect CARE processing such as carbon.

  As shown in this example, when hydrofluoric acid is used as the processing liquid and platinum is used as the catalyst, the surface of the substrate made of SiC wafer is removed flatly (CARE processing). Platinum contamination remains. This platinum contamination can be removed by aqua regia cleaning in which the substrate is immersed in aqua regia.

  In other words, using a hydrofluoric acid as a treatment liquid and platinum as a catalyst, the sample was contaminated with platinum after CARE processing of a sample made of SiC under the processing conditions shown in Table 1 below. FIG. 7 shows the results of measuring platinum contamination after washing with water by the total reflection X-ray fluorescence (TRXF) method under the measurement conditions shown in Table 2 below. In washing with aqua regia, the sample was immersed for 10 minutes in a solution (aqua regia) mixed with hydrochloric acid (60%): nitric acid (60%) at a ratio of 3: 1 and heated to 60 ° C., and then rinsed with ultrapure water. Was performed for 1 minute for one aqua regia washing.

  From FIG. 7, platinum contamination was confirmed in the sample after CARE processing. Thereafter, it can be seen that platinum contamination decreases every time the sample is washed with aqua regia.

  As a comparison, FIG. 8 shows the TRXF measurement results when the sample made of SiC is CARE processed as described above, and then the sample is subjected to SPM cleaning and further hydrofluoric acid cleaning. The SPM cleaning was performed by immersing the sample in a solution of sulfuric acid (98%): hydrogen peroxide (30%) = 4: 1 for 10 minutes and then rinsing with ultrapure water for 1 minute. In the hydrofluoric acid cleaning, the sample was immersed in a hydrofluoric acid (HF: 50%) solution for 10 minutes, and then rinsed with ultrapure water for 1 minute. FIG. 8 shows that platinum contamination existing after CARE processing cannot be removed by SPM cleaning or hydrofluoric acid cleaning. This SPM cleaning and hydrofluoric acid cleaning are the same in the following.

  In this example, the surface of SiC is removed (etched) by the CARE method using hydrofluoric acid as the treatment liquid and platinum as the catalyst on the surface of the catalyst platen. Si, SiC, GaN, sapphire, CARE method using halogenated hydroxides such as hydrofluoric acid and hydrogen chloride as treatment liquid, platinum, gold, ceramic fixed catalyst, molybdenum or molybdenum alloy as catalyst. The surface of ruby or diamond may be removed (etched).

  Further, Si, SiC, GaN, sapphire is obtained by the CARE method using hydrogen peroxide water or ozone water as a treatment liquid and a transition element such as Fe, Ni, Co, Cu, Cr, or Ti as a catalyst on the surface of the catalyst platen. The surface of ruby or diamond may be removed (etched).

  For example, in the CARE units 30C and 30D shown in FIGS. 2 to 4, hydrogen peroxide water as the processing liquid is supplied from the processing liquid supply nozzle 174 to the catalyst surface plate 126, and the catalyst surface plate 126 itself has a catalytic action. A substrate made of Fe with a certain thickness may be used to remove (etch) the substrate surface such as a SiC wafer. Thus, when CARE processing is performed on the surface of a substrate such as a SiC wafer using hydrogen peroxide water as a treatment liquid and Fe as a catalyst, iron contamination occurs on the processed surface of the substrate after processing, and oxidation occurs. A film is produced.

  After using a hydrogen peroxide solution as a treatment liquid and iron as a catalyst, and subjecting the SiC sample to CARE processing under the processing conditions shown in Table 1, the sample was contaminated with iron, and the sample was subjected to SPM cleaning. FIG. 9 shows the result of measurement of iron contamination by X-ray photoelectron spectroscopy (XPS). Here, FIG. 9A shows the XPS measurement result of the Fe2p core level of the sample after CARE processing, and FIG. 9B shows the XPS measurement result of the Fe2p core level of the sample after SPM cleaning. From FIG. 9 (a), a signal of Fe2p core level was confirmed after CARE processing, but from FIG. 9 (b), no signal of Fe2p core level was detected after SPM cleaning. From this, it can be seen that iron contamination generated by CARE processing has been completely removed by SPM cleaning.

  The surface removal process of SiC generally undergoes a process of oxide / oxide film removal, so that an oxide film remains on the surface of the workpiece after processing. In particular, in the light irradiation CARE process in which processing is performed while irradiating the processing surface of the workpiece with ultraviolet rays, the oxidation film is likely to remain on the processed workpiece surface in order to promote the oxidation by irradiating the ultraviolet rays.

After processing a sample made of SiC for 6 hours by light irradiation CARE that uses hydrogen peroxide water as a treatment liquid and quartz glass as a catalyst, and further irradiates the work surface of the work piece with ultraviolet rays. FIG. 10 and FIG. 11 show the results of measurement of the sample surface by X-ray photoelectron spectroscopy after the sample was washed with hydrofluoric acid. FIG. 10 shows the result of measurement of the sample surface after light irradiation CARE processing. In addition to the peak (101.3 eV) indicating the Si—C bond as the sample material, 103.6 eV indicating the oxide film (SiO ₂ ). The peak is observed. FIG. 11 is a result of X-ray photoelectron spectroscopy measurement after immersing a sample after light irradiation CARE for 10 minutes in a 50% hydrofluoric acid solution. The oxide film was removed and SiO ₂ was removed. It can be seen that the peak of the Si—C bond is increased and the peak of the Si—C bond is increased. From this, it was confirmed that the oxide film remaining on the sample surface can be removed by immersing the SiC sample after light irradiation CARE processing in hydrofluoric acid.

  Even after CARE processing is performed on a sample made of SiC using hydrogen peroxide water as a treatment liquid and iron as a catalyst, it is considered that an oxide film remains on the surface of the sample due to the principle of the removal processing. Therefore, also in this case, it is preferable to remove the oxide film by hydrofluoric acid cleaning after the removal processing.

  From the above, for example, in the CARE units 30C and 30D shown in FIGS. 2 to 4, the catalyst surface plate 126 has a catalytic action by using hydrogen peroxide water as the processing liquid supplied from the processing liquid supply nozzle 174. When made of Fe, as the first cleaning unit 42 of the flattening apparatus shown in FIG. 1, a fluorine oxide acid cleaning unit that cleans the substrate by immersing it in hydrofluoric acid is used as in the above example. As the second cleaning unit 43, it is preferable to use an SPM cleaning unit that immerses and cleans the substrate in the SPM. Thus, the substrate after CARE processing is cleaned with hydrofluoric acid by the first cleaning unit 42 and SPM cleaned by the second cleaning unit 43 to remove iron contamination on the substrate surface and an oxide film generated on the substrate surface. can do.

When hydrogen peroxide water or ozone water is used as the treatment liquid, in addition to the above transition metals, noble metals such as platinum and gold, ceramic-based metal oxide films, or glass-based metal oxides are used as catalysts on the surface of the catalyst platen. You may use things. Examples of the ceramic metal oxide film include alumina, and examples of the glass metal oxide include sapphire (Al ₂ O ₃ ), quartz (SiO ₂ ), and zirconia (ZrO ₂ ).

Furthermore, when hydrogen peroxide water or ozone water is used as the treatment liquid, an acidic or basic solid catalyst may be used as the catalyst on the surface of the catalyst platen. Examples of the acidic or basic solid catalyst include non-woven fabric, resin or metal imparted with an ion exchange function. The material imparting the ion exchange function is preferably, for example, a nonwoven fabric made of polyethylene fiber, a resin such as fluororesin or PEEK, or a metal oxidation-resistant material such as Pt or Au. An ion exchange function can be imparted to a nonwoven fabric made of fibers. In this case, the etching rate for the workpiece can be increased by increasing the ion exchange capacity of the solid catalyst. Examples of the solid acid catalyst include solid acid obtained by attaching H ₂ SO ₄ , H ₃ PO _4, etc. to silica-alumina, inorganic salts such as metal sulfate and metal phosphate, Al ₂ O ₃ , ThO _2. And oxides such as Al ₂ O ₃ —SiO ₂ and TiO ₂ —SiO ₂ . As the solid base catalyst, a solid base obtained by attaching NaOH, KOH, Na, K to silica gel or the like, an inorganic salt such as Na ₂ CO ₃ , BaCO ₃ , Na ₂ WO ₄ , CaO, MgO, SrO, MgO Examples thereof include oxides such as —SiO ₂ and MgO—Al ₂ O ₃ .

It is thought that contamination of the surface of the surface plate (especially organic contamination) or the presence or absence of an oxide film on the surface of the surface plate contributes to wettability. As means for improving the wettability of the catalyst surface plate, there are a method performed before processing and a method performed during processing.
(1) When wettability of the catalyst surface plate is improved as a separate process before processing Wash the chemical with a chemical solution (for example, sulfuric acid / overwater cleaning) or UV irradiation before processing the surface plate. Thereby, organic matter contamination on the surface of the surface plate is removed, and the wettability of the surface of the surface plate is improved. Further, by performing ultraviolet irradiation, the surface of a surface plate such as iron is oxidized and wettability is improved. It is applicable to a platen other than platinum to generate an oxide film on the catalyst surface by ultraviolet irradiation and improve the wettability of the catalyst platen.
(2) Improving the wettability of the catalyst surface plate during processing During processing, the surface of the surface plate is irradiated with ultraviolet rays at a position different from the top ring, and an oxide film is generated on the surface of the catalyst surface. Improves wettability. As a result, organic substances on the surface of the surface plate attached during processing are removed, so that the wettability is improved and the surface becomes hydrophilic. Moreover, even if the oxide film on the surface of the platen such as iron is removed during the processing, the oxide film can be generated again by irradiating with ultraviolet rays, and the wettability is improved.

  In the CARE units 30C and 30D of the above-described embodiment, one substrate is held by the substrate holder 130, and each substrate is pressed toward the catalyst surface plate to perform CARE processing. The catalyst surface plate is generally expensive, and the processing performance is affected by the surface state of the catalyst surface plate. For this reason, it is preferable to simultaneously carry out CARE processing of a plurality of substrates by simultaneously holding a plurality of substrates, for example, four substrates, with a substrate holder and simultaneously pressing the substrates toward the catalyst surface plate. A CARE unit including a plurality of substrate holders for holding one substrate may be used.

  Before performing the CARE process, it is preferable to clean the surface (processed surface) of the substrate (processed object) by wet cleaning. The substrate surface contamination includes, for example, particulate contamination, organic contamination, and metal contamination. For particulate contamination, non-scrub cleaning such as water jet (hydrofluoric acid cleaning when colloidal silica is used), organic SPM cleaning (sulfuric acid / hydrogen peroxide cleaning) is suitable for contamination, and SPM cleaning or hydrofluoric acid cleaning is appropriate for metal contamination. In these cleanings, since the surface of the SiC substrate does not change, only contamination can be removed.

FIGS. 12A to 12D show a processing concept of CARE processing of a workpiece using a processing solution to which a buffer solution (buffering agent) is added. As shown in FIG. 12A, when the solid acidic catalyst 416 is immersed in the treatment liquid 412b and arranged, hydrogen ions (H ⁺ ) 416a are generated on the surface of the solid acidic catalyst 416, and the hydrogen ions 416a are Detach from the surface of the solid acidic catalyst 416. Here, the buffer solution 480 is dissolved in the processing solution 412b by adding the buffer solution (buffer agent). Therefore, as shown in FIG. 12B, the buffer solution 480 is removed from the surface of the solid acidic catalyst 416. The released hydrogen ions 416a react with the buffer 480 quickly and become inactivated. Therefore, the hydrogen ions 416a exist only on or in the vicinity of the solid acidic catalyst 416 serving as a processing reference surface. Therefore, as shown in FIG. 12C, when the solid acidic catalyst 416 and the processing surface of the workpiece 414 are brought into contact with or in close proximity to each other in the processing liquid 412b containing the buffer 480, the processing of the contact portion is performed. Surface atoms of the object 414 are dissolved in the treatment liquid 412b by a chemical reaction. Then, as shown in FIG. 12 (d), when the solid acidic catalyst 416 is separated from the workpiece surface of the workpiece 414, hydrogen ions 416 a generated on the surface of the solid acidic catalyst 416 are formed on the surface of the workpiece 414. The dissolution reaction stops because it no longer works. Therefore, the processing surface of the workpiece 414 is processed only while the solid acidic catalyst 416 is in contact with or in close proximity.

Examples of the solid acid catalyst include solid acid obtained by attaching H ₂ SO ₄ , H ₃ PO _4, etc. to silica-alumina, inorganic salts such as metal sulfate and metal phosphate, Al ₂ O ₃ , ThO _2. And oxides such as Al ₂ O ₃ —SiO ₂ and TiO ₂ —SiO ₂ , and cation exchangers. As the solid base catalyst, a solid base obtained by attaching NaOH, KOH, Na, K to silica gel or the like, an inorganic salt such as Na ₂ CO ₃ , BaCO ₃ , Na ₂ WO ₄ , CaO, MgO, SrO, MgO Examples thereof include oxides such as —SiO ₂ and MgO—Al ₂ O ₃ and anion exchangers.

  When no buffer solution (buffering agent) is added to the processing solution, that is, when there is no buffering agent in the processing solution, hydrogen ions diffuse into the processing solution even after the surface of the solid acidic catalyst is desorbed. For this reason, hydrogen ions are also present at some distance from the surface of the solid acidic catalyst. For this reason, when the solid acidic catalyst and the work surface of the work piece are brought into contact with or in close proximity to each other in the processing liquid, not only the contact portion but also the portion away from the surface of the solid acidic catalyst is subjected to a chemical reaction. Surface atoms of the surface are dissolved in the processing solution. Thus, hydrogen ions act not only on the convex portion of the surface to be processed but also on the concave portion, the surface to be processed is processed isotropically, and flattening does not proceed.

  Examples of the buffer solution (buffer agent) include a phosphate buffer solution. In addition to the phosphate buffer solution, a buffer solution such as an acetate buffer solution or a citrate buffer solution that reduces the change in pH of the treatment solution may be used. That's fine. In the case of using a buffer solution added to the treatment solution, the treatment solution is preferably ultrapure water or an aqueous solution containing an oxidizing agent such as ozone water, hydrogen peroxide solution or potassium persulfate aqueous solution. It is preferable to adjust the additive concentration so as to have a predetermined pH. For example, when processing a GaN substrate, the pH of the treatment liquid is desirably around 7 (pH = 6.5 to 7.5).

  FIG. 13 shows an outline of a CARE unit (light irradiation CARE unit) including a light source. This CARE unit (light irradiation CARE unit) is connected to a container 484 filled with a processing solution 482 containing, for example, a buffer solution (buffering agent) and an upper end of a rotating shaft 486 and is rotatably arranged in the container 484. A surface plate 488 and a holder 492 that detachably holds a workpiece 490 such as a GaN substrate with the processing surface facing downward. The holder 492 is fixed to the lower end of the rotation shaft 494. A light source 496 is installed below the surface plate 488, and the surface plate 488 is made of a solid acidic catalyst having excellent light transmittance, for example, quartz. Thus, the light source 496 irradiates the lower surface (processed surface) of the workpiece 490 with light, for example, ultraviolet light, through the surface plate 488. The surface plate 488 may be made of sapphire or zirconia having excellent light transmittance.

  Using the CARE unit (light irradiation CARE unit) shown in FIG. 13, the GaN wafer (sample) was processed while irradiating with ultraviolet rays. Processing time is 3 hours. FIG. 14A shows a phase shift interference microscope image of the sample surface before processing. FIG. 14B shows a phase shift interference microscope image of the sample surface after processing using a processing solution (ultra pure water) to which no buffer solution (buffering agent) is added, and FIG. The phase shift interference microscope image of the sample surface after processing using the processing solution (pure water) which added the buffer solution (phosphate buffer solution of pH 6.8) is shown.

  From FIG. 14 (a), the surface roughness introduced into the surface of the sample in the pre-processing can be observed, and from FIG. 14 (b) and (c), processing was performed using a processing solution to which a buffer solution (buffering agent) was added. In this case, it can be seen that the surface roughness is greatly reduced as compared with the case of processing using a processing solution to which no buffer solution (buffering agent) was added.

  For example, when a substrate such as a semiconductor wafer is irradiated with light having energy larger than the band gap, electrons in the valence band are excited and electron-hole pairs are generated. Oxidation of the substrate surface is performed through valence band holes generated by light irradiation. When electron-hole pairs generated by light absorption recombine and disappear, an oxidation reaction on the substrate surface is not performed, and thus recombination needs to be suppressed. By bringing platinum (Pt) and the substrate into electrical contact, the electrons of the conductor generated by light absorption are accumulated in the platinum and exchanged with the solution, so that recombination of electron-hole pairs is suppressed. It is possible.

  In order to confirm the effect of electrically contacting the substrate with platinum, a photo-oxidation experiment on the surface of the GaN substrate was performed. The sample was an n-type GaN substrate (0001) surface, and platinum was formed on the back surface (000-1) with a thickness of 500 nm by electron beam evaporation, and the substrate and platinum were brought into electrical contact. A GaN substrate on which no platinum film was formed was used as a comparative sample.

  The light irradiation was performed for 3 hours in a state where the substrate was immersed in ultrapure water. FIG. 15 shows XPS O1s spectra before and after light irradiation. The change in the O1s peak intensity of the sample that was not subjected to the platinum film formation was not confirmed as compared with the intensity before the light irradiation. On the other hand, it can be seen that the O1s peak intensity of the sample on which the platinum film was formed is larger than that before light irradiation. From the above, it can be seen that oxidation of the sample surface is performed only when platinum deposition is performed.

  Further, a processing experiment was performed by a light irradiation CARE method using a GaN substrate with platinum deposited on the back surface and a GaN substrate not subjected to platinum deposition as samples. In the experiment, the sample was processed for 3 hours while irradiating the sample surface with light in a phosphate buffer solution of pH = 6.86. 16 (a) and 16 (b) show phase shift buffer microscope images of the sample (GaN substrate) surface before and after processing of the sample not subjected to platinum deposition on the back surface, and FIG. 16 (c) shows platinum deposition on the back surface. The phase shift buffer microscope image of the sample (GaN substrate) surface after processing of the performed sample is shown, respectively. The sample surface (FIG. 16 (b)) on which the platinum film is not formed on the back surface has no change in morphology and microroughness compared to the pre-processed surface (FIG. 16 (a)), and the processing proceeds. You can see that it is not. On the other hand, it can be seen that the sample surface (FIG. 16C) on which the platinum film is formed on the back surface is flattened by removing scratches existing on the pre-processed surface. It can also be seen that the microroughness is improved from 6.497 nm rms to 0.804 nm rms.

  In addition to platinum, other metals such as Ti, Ni, and Cr may be used as the metal to be brought into contact with the substrate, but platinum is preferably used at the interface between the treatment liquid and the metal. As a film forming method, any of vacuum vapor deposition, electron beam vapor deposition, sputter film formation, etc. may be used. Although it is desirable to deposit platinum on almost the entire back surface, platinum may be deposited on a part of the back surface, and it is not always necessary to form a film on the back surface of the substrate, and a metal substrate holder is used. As long as the substrate and the metal are electrically connected. Platinum may be coated on the inside of the retainer of the substrate holder and contacted with the edge portion of the substrate.

  The embodiment of the present invention has been described so far, but the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention may be implemented in various different forms within the scope of the technical idea.

It is a top view which shows the whole structure of the planarization apparatus used for this invention. It is a longitudinal front view which shows the outline | summary of the CARE unit as a final surface removal processing unit of the planarization apparatus of FIG. It is a top view of the catalyst surface plate of the CARE unit of FIG. It is a partially expanded sectional view of FIG. It is a top view which shows the other example of a catalyst surface plate. It is sectional drawing which shows the state which attached the catalyst surface plate shown in FIG. 5 to the rotary body. It is a graph which shows the result of having measured the sample after carrying out CARE processing, and the platinum contamination after wash | cleaning this sample with aqua regia by a total reflection X ray fluorescence analysis method. It is a graph which shows the result of having measured the sample after carrying out CARE processing, and the platinum contamination after wash | cleaning this sample by SPM and also hydrofluoric acid (HF) by the total reflection X ray fluorescence analysis method. It is a graph which shows the result of having measured the iron contamination of the sample after carrying out CARE processing, and the iron contamination after washing | cleaning this sample by SEM photoelectron spectroscopy. It is a graph which shows the result of having measured the sample surface by X-ray photoelectron spectroscopy after carrying out light irradiation CARE processing of the SiC sample. It is a graph which shows the result of having measured the sample surface after hydrofluoric-acid washing | cleaning of the SiC sample which carried out light irradiation CARE process by the X ray photoelectron spectroscopy. It is a figure which shows the process concept which carries out the CARE process of the to-be-processed object using the process liquid which added the buffer solution (buffer agent) to process order. It is a figure which shows the outline | summary of the CARE unit (light irradiation CARE unit) provided with the light source. FIG. 14A shows a phase shift interference microscope image of the sample surface before CARE processing, and FIG. 14B shows CARE using a processing solution (ultra pure water) that does not contain a buffer solution (buffer agent). FIG. 14C shows a phase shift interference microscope image of the sample surface after processing, and FIG. 14C shows the phase shift of the sample surface after performing CARE processing using a processing solution containing a buffer solution (buffer agent). An interference microscope image is shown. It is an XPS O1s spectrum before and after light irradiation when light irradiation is performed in a state where a substrate on which platinum is formed and a substrate on which platinum is not formed is immersed in ultrapure water. FIG. 16A shows a phase shift buffer microscope image of the surface of the sample (GaN substrate) before processing, and FIG. 16B shows the sample (GaN substrate) after processing in the sample that is not subjected to platinum deposition on the back surface. FIG. 16C shows a phase shift buffer microscope image of the surface of the sample (GaN substrate) after processing the sample with platinum deposited on the back surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Load unload part 3 Surface removal process part 4 Cleaning part 5 1st linear transporter 6 2nd linear transporter 20 Front load part 30A Lapping unit (1st surface removal process unit)
30B CMP unit (second surface removal processing unit)
30C, 30D CARE (catalyst reference etching) unit (third surface removal processing unit)
124 treatment tank 126 catalyst surface plate 128 substrate (workpiece)
130 Substrate holder 140 Base material 142 Platinum (catalyst)
144 Groove 150 Pure water injection nozzles 160, 162 Pure water replacement unit 170 Heater 172 Heat exchanger 174 Treatment liquid supply nozzle 176 Fluid flow path 200 Catalyst surface plate 200a Through hole 202 Rotating body 204 Treatment liquid reservoir 206 Rotary joint 300A Surface plate 300B Polishing tables 301A, 301B Top ring 302A Lapping liquid supply nozzle 302B Polishing liquid supply nozzle 303B Dresser

Claims (6)

A flattening method for flatly removing a processed surface made of SiC or GaN of a workpiece,
An initial surface removal step is performed to improve the flatness of the work surface by processing the work surface of the work piece flatly by grinding, lapping or CMP.
The surface to be polished of the workpiece after the initial surface removal process is cleaned with hydrofluoric acid cleaning or pure water cleaning,
Hydrohalic acids, arranged workpiece hydrogen peroxide or ozone water or Ranaru processing liquid, at least the surface of platinum, gold, ceramic-based solid catalyst, transition metals, and any of glass-based metal oxide The final surface removal step is performed by catalyst-based etching in which the surface of the catalyst platen made of only is brought into contact with or in close proximity to the work surface of the work piece and the work surface is processed flat without damage.
A planarization method comprising: cleaning a processed surface of an object to be polished after the final surface removal step with at least one of SPM cleaning, aqua regia cleaning, and hydrofluoric acid cleaning.   The planarization method according to claim 1, wherein a wettability improving agent for improving the wettability of the catalyst surface plate is further added to the treatment liquid.   The planarization method according to claim 2, wherein the wettability improver is nitric acid or ethanol.   The flattening method according to claim 1, wherein a pH adjusting buffer is further added to the treatment liquid.   The planarization method according to claim 1, wherein an organic alcohol or an inorganic acid is further added to the treatment liquid. Any of a change in the current value of the drive motor that rotationally drives the catalyst platen, a change in the concentration of the treatment liquid, a measurement result when the work surface is measured with an optical monitor, and a change in mass before and after the work piece is processed 6. The planarization method according to claim 1 , wherein an end point of the final surface removal step is detected .

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