JP2007142458A - Treatment apparatus and method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to easily automate the timing and the quantity of phosphoric acid recovered to the phosphoric acid regenerator side and to reduce or maintain impurities in the phosphoric acid constant in a treatment apparatus for regenerating phosphoric acid in use in a tank through a circulation filtering passage and a phosphoric acid regenerator employing hydrofluoric acid. <P>SOLUTION: The treatment apparatus is provided with an etching tank 3 with an overflow section 3a for treating a wafer 1 with hot phosphoric acid; the circulation filtering passage 5 for leading the phosphoric acid flowing over the overflow section 3a to the outside of the tank 3 and returning it back to the tank while filtering, heating and adding pure water; the phosphoric acid regenerator 6 for heating the phosphoric acid taken out of the circulation filtering passage 5 through branch piping 60 by adding hydrofluoric acid thereto; and a supplying piping 67a for supplying the phosphoric acid regenerated by the phosphoric acid regenerator 6 to the tank 3. The improvement is to provide a branch piping 60 before a filtering section 52 for filtering phosphoric acid of the circulation filtering passage 5, and to provide a flow regulation means (a pressure gauge and a needle valve or the like) for controlling the quantity of phosphoric acid branched to the phosphoric acid regenerator 6 side depending on the circulating liquid pressure flowing to the filtering section 52. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a silicon nitride film (hereinafter abbreviated as a nitride film) such as a semiconductor wafer (for example, a Si wafer, hereinafter abbreviated as a wafer), which is a semiconductor device, may be abbreviated as hot phosphoric acid (hereinafter abbreviated as phosphoric acid). In particular, the present invention relates to a processing apparatus having a regenerating unit that makes it possible to recover and reuse a used chemical solution that has contributed to the chemical processing, and a method for manufacturing a semiconductor device. It is.

In wafer processing in semiconductor manufacturing or the like, a fine nitride film pattern may be formed on a wafer by etching. In this etching, dry etching is mainly used, but an oxide film is selectively formed by using the formed nitride film as an oxidation mask, and the nitride film and the oxide film are etched to remove the unnecessary nitride film mask. A method of treating with hot phosphoric acid having a high selectivity is still widely used today. In this wafer processing, if etching is performed under a condition where the etching selectivity between the nitride film and the oxide film is large, the nitride film on the wafer reacts with water and decomposes into silicon oxide and ammonia, so that the etching is performed appropriately. In this reaction, it is known that phosphoric acid acts as a catalyst and can be used permanently as a catalyst by simply replenishing water without being consumed, and efficient etching is possible.
Japanese Patent Laid-Open No. 11-293479 JP-A-9-45660 Japanese Patent Laid-Open No. 9-275091

  However, in actual wafer processing, in order to increase the etching selectivity, it is unavoidable to use the decomposed silicon oxide dissolved in hot phosphoric acid at a high concentration. The amount reaches the saturation dissolution amount and the silicon oxide precipitates as fine particles, which become fine particles that contaminate the wafer and clog the circulating filter for reusing the etchant. Cause various obstacles. Therefore, before the dissolved amount of silicon oxide reaches the saturated dissolved amount, for example, the etching solution must be replaced with new phosphoric acid, or the concentration of silicon oxide in phosphoric acid must be lowered. Phosphoric acid containing a large amount of silicon oxide cannot be used as an etching solution and must be disposed of as a waste solution, which may adversely affect the environment.

  Further, the etching rate of the nitride film mask is constant regardless of the silicon oxide concentration if the phosphoric acid temperature is constant, but the etching rate of the oxide film is inversely proportional to the silicon oxide concentration in phosphoric acid, and the silicon oxide concentration increases. Decrease. As described above, since the etching selectivity between the nitride film and the oxide film changes according to the silicon oxide film concentration, it causes the oxide film thickness to fluctuate between the processing lots, resulting in quality degradation. Therefore, it is necessary to increase the design and processing margin of the used wafer processing apparatus by that amount, but the allowable margin has been reduced as IC miniaturization and higher integration progressed. From such a background, it is desired to realize a wafer processing apparatus that has a high selection ratio, little variation between processing lots, and that does not discharge phosphoric acid waste liquid.

  The present applicants have developed a wafer processing apparatus structure and a regeneration method such as Japanese Patent Application Laid-Open Nos. 11-293479 and 9-45660 from the above situation. The present invention is a further improvement of the present invention, in which phosphoric acid in use in an etching tank is regenerated by a circulation filtration path and regenerated by a phosphoric acid regenerating apparatus using hydrofluoric acid recovered through a branch pipe. It is an object of the processing apparatus to facilitate the automation of the recovery amount and the recovery amount to the phosphoric acid regenerating apparatus side, and to reduce or maintain the impurities in the phosphoric acid. Then, the etching selectivity between the nitride film and the oxide film is kept high, and the nitride film can be etched with phosphoric acid with a constant selectivity.

  In order to achieve the above object, according to the present invention of claim 1, as illustrated in the drawing, the semiconductor wafer 1 is etched with hot phosphoric acid, the etching tank 3 with the overflow portion 3a, and the overflow portion 3a overflowed. Circulating filtration path section 5 for introducing phosphoric acid outside the etching tank, filtering, heating, adding pure water and returning it to the etching tank 3, and hydrofluoric acid in the phosphoric acid taken out from the circulation filtering path section 5 through the branch pipe 60 And a replenishing pipe 67a for replenishing the etching tank 3 with the phosphoric acid regenerated by the phosphoric acid regenerating apparatus 6, the branch pipe 60 is subjected to the circulation filtration. A flow rate adjusting means (pressure gauge) that is provided in front of the filtration unit 51 for filtering the phosphoric acid in the passage unit 5 and that can control the amount of phosphoric acid branched to the phosphoric acid regenerating apparatus 6 side according to the circulating fluid pressure flowing to the filtration unit 51. 6 It is characterized by having a needle valve 65 or the flow meter or the like) and.

  In the above structure, first, in the etching section, hot phosphoric acid is led from the etching tank 3 to the circulation filtration path section 5 and circulated while being filtered, heated and added with pure water, and impurities ( (Silicon oxide etc.) removal and phosphoric acid concentration (concentration change caused by moisture evaporation) are adjusted to be constant. Based on this premise, the main part is that the amount of phosphoric acid branched by the branch pipe 60 provided in front of the filtering part 51 can be controlled according to the circulating fluid pressure flowing to the filtering part 51. That is, the degree of clogging of the filter of the filtration unit 51 gradually increases due to the filtration action. Circulating fluid pressure is proportional to the degree of clogging. Therefore, the present invention makes the amount of phosphoric acid branched off from the branch pipe 60 and recovered in the regeneration section correspond to the circulating fluid pressure, and the phosphoric acid regeneration is proportional to the amount of impurities (such as silicon oxide) in the phosphoric acid used. Take out to the apparatus 6 side (note that the amount corresponding to the recovered amount is replenished from the replenishment pipe 67a). That is, the removal amount to the phosphoric acid regenerating apparatus 6 side can be automatically performed by a flow rate adjusting means (for example, a pressure gauge 61 and a needle valve 65 or a measuring tank). This not only automates the control of the recovery amount and the recovery amount of phosphoric acid from the circulation filtration path 5 to the phosphoric acid regenerating apparatus 6, but also makes it possible to keep impurities (such as silicon oxide) in the used phosphoric acid at a predetermined value. . This advantage is due to fluctuations in etching characteristics before and after replacement, which is a problem in a method in which part or all of phosphoric acid used is periodically replaced as in the past (the variation in the etching rate ratio of the nitride film and the oxide film, that is, the variation in selectivity). In addition, the device operation rate does not deteriorate. Moreover, the lifetime of the filter of the filtration part 51 can be lengthened, and the operating rate fall accompanying filter replacement can also be avoided.

The above invention is more preferably embodied as in claims 2-6. That is,
First, the phosphoric acid regenerating apparatus 6 includes a receiving tank 63 for temporarily storing the phosphoric acid branched by the branch pipe 60, a treatment tank 100 for adding and heating hydrofluoric acid to phosphoric acid introduced from the receiving tank 63, and The storage tank 113 temporarily stores phosphoric acid regenerated in the processing tank 100, and the processing tank 100 cools and liquefies the vapor evaporated from the processing tank, and is liquefied by the cooler 200. It has a configuration including a thermostatic chamber 201 that adjusts the obtained liquid to a constant temperature, and a measurement unit 112 that includes a fluorine measuring device 205 that measures the fluorine concentration in the liquid adjusted in the thermostatic chamber 201. In this structure, for example, the recovered phosphoric acid in the receiving tank 63 is batch transferred to the processing tank 100, the recovered phosphoric acid is regenerated in the processing tank 100, and the end point of the regeneration is determined via the measuring unit 112. When the recovered phosphoric acid reaches a predetermined low silicon oxide concentration, the phosphoric acid is stored in the storage tank 113, or the phosphoric acid in the storage tank 113 can be used for replenishment to the etching tank 3 side. The regeneration principle using hydrofluoric acid is the same as that of JP-A-11-293479 and JP-A-9-45660. In terms of apparatus, it is possible to continuously perform the etching process and the regeneration process by simple control.
Secondly, the fluorine measuring device 205 is constituted by a resistivity meter or a conductivity meter. In particular, the fluorine concentration in the regenerated phosphoric acid can be measured with high accuracy, and as a result, the silicon oxide concentration in the phosphoric acid can be controlled to be constant, thereby improving the control accuracy of the apparatus of the present invention. Is.
Thirdly, the storage tank 113 has heating means 116 and 120 for controlling the regenerated phosphoric acid introduced from the processing tank 100 to a predetermined temperature, and between the overflow section 3a. It is the structure connected by the said supply piping 67a. This is because, in particular, the regenerated and heated phosphoric acid in the storage tank 113 is once sent to the overflow part 3a of the etching tank 3 through the replenishment pipe 67a, and passes through the circulation filtration path part 5 from the overflow part 3a. This is significant in that it is introduced into the etching tank 3 and the concentration and temperature fluctuations of the regenerated phosphoric acid supplemented to the phosphoric acid in use are minimized.
Fourth, the amount of phosphoric acid replenished sent from the storage tank 113 can be controlled by a signal from the liquid level gauge 36 provided in the overflow portion 3a. This is significant in that the amount of phosphoric acid replenished is automatically controlled according to the amount of phosphoric acid in the overflow portion 3a, and a necessary amount of phosphoric acid is secured in the etching tank 3.
Fifth, the supply pipe can switch between a path 67a for sending the regenerated phosphoric acid taken out from the storage tank 113 to the etching tank 3 or the overflow part 3a, and a circulation path 67b for returning to the storage tank again. That is to make up. In particular, the recycled phosphoric acid in the storage tank 113 is circulated by the circulation path 67b so that the temperature and the like are made uniform and can be used in an optimum state.

  The apparatus of the present invention as described above can maintain phosphoric acid and regenerated phosphoric acid in use at a desired silicon oxide concentration. For example, in a high-mix low-volume production line that manufactures different wafers, nitridation that is removed by etching. Even if there is a difference in film amount, it can be easily dealt with, and it is suitable for a system LSI production line that has become increasingly necessary in recent years. Further, by controlling the silicon oxide concentration of phosphoric acid as desired, it is desirable that the etching amount of the oxide film of the wafer 1 in phosphoric acid be as small as possible in forming the nitride film mask, and the silicon oxide concentration in the hot phosphoric acid used. Can be applied to the case where it is required to be as high as possible, and etching with hot phosphoric acid having such a high silicon oxide concentration is possible particularly in the manufacture of fine ICs. This is because the deposited silicon oxide in the filtration part 51 in the circulation filtration path part 5 is re-dissolved together with the regenerated phosphoric acid that is replenished with the phosphoric acid overflowing the overflow part 3a of the etching tank 3, so that the particulate contamination increases rapidly. This is because clogging of the filter of the filtration unit 51 is eliminated and the process is maintained normally.

  Each of the above inventions is specified based on the embodiment. As a technical idea, for example, the semiconductor wafer is an object to be processed, the etching tank is a processing tank that performs processing such as etching, the circulation filtering path is circulated and a circulation path that performs filtration, and the like. Can be generalized as in claims 7 to 9 by using a chemical solution treatment unit for performing a treatment such as regeneration of a chemical solution such as phosphoric acid.

  That is, the invention of claim 7 includes a treatment tank 3 for treating the object to be treated 1 with a chemical solution, a circulation path section 5 for guiding the chemical solution in the treatment tank to the outside of the tank and returning it to the treatment tank, and the chemical solution. In a processing apparatus including a chemical solution processing unit 6 that performs processing, a flow rate adjusting unit that controls the flow rate of the chemical solution sent to the chemical solution processing unit 6 according to the pressure of the chemical solution flowing in the circulation path unit 5 ( It has a pressure gauge 61 and a needle valve 65 or a flow meter). In the present invention, the circulation path unit 5 includes a filtering unit 51 that filters the chemical solution, and the hydraulic pressure is mainly a hydraulic pressure that is generated when the chemical solution passes through the filtering unit 51. In addition, the circulation path section 5 includes a first circulation path section (a pipe connecting the discharge port 34 and the filtration section 51 in FIG. 2) that sends the chemical solution from the processing tank 3 to the filtration section 51. And a second circulation path section (pipe connecting between the filtration section 51 and the supply port 35 in FIG. 2) that sends the chemical solution that has passed through the filtration section to the treatment tank 3 from the filtration section 51. In addition, a branch pipe 60 that connects the first circulation path section and the chemical liquid processing section 6 is provided, and the chemical liquid is sent to the chemical liquid processing section 6 through the branch pipe.

  In the structure described above, for example, an object other than the wafer or an etching solution other than phosphoric acid as the chemical solution can provide the advantages of the above-described invention. Further, the manufacturing method of claim 10 is significant in that each of the above inventions is a processing apparatus, and is specified from the viewpoint of making various wafers as semiconductor devices.

  As described above, in the processing apparatus and the method for manufacturing a semiconductor device according to the present invention, for example, as in claim 1, the phosphoric acid overflowed in the overflow portion of the etching tank is filtered, heated, and purified water. In the structure provided with the circulation filtration path portion by addition, the circulation fluid pressure before filtration of the circulation filtration passage portion is measured, and the amount of liquid branched to the branch pipe is controlled according to the circulation fluid pressure pressure. It is easy to automate the control of the recovery amount and the recovery amount to the regenerator side, maintain the etching accuracy and suppress the recovery amount, suppress variation in wafer etching accuracy between lots, and the like.

Hereinafter, the present invention will be described with reference to the drawings showing the embodiments. 1 is an overall schematic configuration diagram of the apparatus of the present invention, FIG. 2 is a configuration diagram mainly including an etching tank and a circulation filtration path portion of the apparatus, and FIG. 3 is a configuration diagram mainly including a phosphoric acid regenerating apparatus of the apparatus. is there. In the following description, after describing each part of the apparatus of the present invention, the advantages of the present invention will be clarified by referring to an apparatus operation example.
(Apparatus Structure) This wafer processing apparatus is an etching unit mainly composed of an etching tank 3 for etching a nitride film of the wafer 1 by immersing the wafer 1 in a hot phosphoric acid (etching solution) in a state where the wafer 1 is housed in a wafer cassette 2. 4, a circulation filtration path part 5 for returning the phosphoric acid overflowing from the etching tank 3 to the etching tank 3 again through filtration, heating and pure water addition steps, and branching the phosphoric acid from the circulation filtration path part 5 A phosphoric acid regenerating apparatus 6 is provided which lowers the silicon oxide concentration, regenerates phosphoric acid having a certain silicon oxide concentration usable in the etching solution, and returns the phosphoric acid to the overflow portion 3a of the etching tank 3.
(Etching part) In this etching part 4, an automatic transfer robot (not shown), a belt conveyor, and the like are disposed together with the etching tank 3, and the wafer 1 is taken in and out of the tank body of the etching tank 3 to be etched. In the etching tank 3, the tank body is defined by the inner peripheral wall 30 and the bottom wall 31, and an overflow portion 3 a that receives phosphoric acid overflowing from the upper end of the inner peripheral wall 30 is formed on the outer periphery. The inner peripheral wall 30 and the bottom wall 31 are provided with a surface heater which is a heating element (not shown). The tank body is provided with a mesh 32 which is a dispersion plate inside the bottom, and the wafer cassette 2 is held on the mesh 32. In addition, the liquid introduction / discharge structure is provided on the upper side of the overflow portion 3a to replenish phosphoric acid (mainly regenerated phosphoric acid), and the overflowed phosphoric acid provided on the bottom wall of the overflow portion 3a. And a supply port 35 for introducing phosphoric acid provided in the bottom wall 31 and treated in the circulation filtration path 5 into the tank body. As a control system, a plurality of liquid level sensors (S1 to S3) 36 for measuring the phosphoric acid liquid level of the overflow portion 3a, a temperature sensor 37 for detecting the liquid temperature of phosphoric acid in the tank body, and detection by the temperature sensor 37 A heater controller 38 is provided for controlling the surface heater based on the temperature to maintain phosphoric acid at a predetermined temperature.
(Circulation filtration path part) This circulation filtration path part 5 includes a pump 50 for returning phosphoric acid discharged from the discharge port 34 to the tank body of the etching tank 3 from the supply port 35, a filter 51 for filtering the phosphoric acid, A line heater 52 which is a heater for bringing the filtered phosphoric acid to a predetermined temperature, a temperature sensor 53 and a heater controller 54 for controlling the line heater 52, and a predetermined amount of phosphoric acid heated to the predetermined temperature. And a metering pump 55 for adding pure water. That is, here, phosphoric acid is first filtered by the filter 51 with respect to the etching solution, that is, phosphoric acid discharged from the overflow portion 3a. Next, phosphoric acid is heated to a certain temperature by the line heater 52, and then purified water is added by the metering pump 55 to adjust the phosphoric acid concentration to be kept constant, and returned to the tank body. The line heater 52 is heated because the temperature of the phosphoric acid discharged from the overflow portion 3a is slightly lowered, the metering pump 55 corrects the fluctuation of the phosphoric acid concentration caused by the evaporation, and the filter 51 contains impurities (precipitation) in the phosphoric acid. Removed silicon oxide). Therefore, it is important to filter the filter 51 before warming the phosphoric acid discharged from the overflow portion 3a.
(Phosphoric acid regenerating apparatus) This phosphoric acid regenerating apparatus 6 includes a branch pipe 60 and a flow rate adjusting means (pressure gauge 61, needle valve 65, etc.) provided in the piping section between the pump 50 and the filter 51 in the circulation filtration path section 5. An appropriate amount of phosphoric acid flowing through the circulation filtration path unit 5 is collected in the receiving tank 63, and the collected phosphoric acid is processed in the regenerating unit 7 of FIG. 2 so that it can be reused. That is, the branch pipe 60 is provided with a pressure gauge 61, a flow meter 62, a needle valve 65, and an automatic valve 66. Here, the pressure gauge 61 measures the fluid pressure (circulating fluid pressure or filtration pressure) before the filter 51, that is, the piping portion between the pump 50 and the filter 51. The flow meter 62 is an integrating type, and measures the flow rate of phosphoric acid (phosphoric acid to be regenerated) branched through the branch pipe 60. The needle valve 65 is a flow rate adjusting valve. By appropriately adjusting the opening degree of the needle valve 65, the flow rate of phosphoric acid branched from the branch pipe 60 is automatically set in accordance with the circulating fluid pressure. Controlled. The automatic valve 66 is an on-off valve. When the automatic valve 66 is in an open state, the phosphoric acid branched from the branch pipe 60 is collected in the receiving tank 63. The receiving tank 63 has a plurality of liquid level sensors (S4, S5) 64, and always measures the recovery amount. The phosphoric acid collected here is introduced into the treatment tank 100 from the drain port 72 at the bottom by controlling the automatic valve 101 with a signal from the control circuit 300 described later in a state where it is in a predetermined amount or more.

  The processing tank 100 is configured as a set with the concentration measuring unit 112 and the storage tank 113. The treatment tank 100 includes a liquid level sensor (S6, S7) 102, a surface heater 103 and a surface heater 104 for heating phosphoric acid in the tank, a temperature sensor 105 for detecting the temperature of phosphoric acid in the tank, and a temperature sensor. A heater controller 106 for heating the phosphoric acid in the tank by controlling the surface heaters 103, 104 and the like based on the detected temperature 105; a metering pump 107 which is a pure water supply means for adding pure water into the tank; The replenishment pipe 108 in the tank, the HF tank 109 and the metering pump 110 which are chemical supply means for supplying a necessary amount of HF (hydrofluoric acid, that is, hydrogen fluoride) into the tank, and the vapor provided to evaporate provided in the upper part of the tank. A steam outlet 111 and the like for extraction are provided.

  The measuring unit 112 is a part for detecting the current concentration of hydrofluoric acid introduced into the phosphoric acid in the treatment tank 100 for regeneration and determining the progress and end point of regeneration. In this embodiment, a cooler 200 that cools the vapor of the processing bath 100, a thermostatic chamber 201 including a spiral tube that adjusts the liquid cooled here to a constant temperature, its temperature controller 202, and the liquid from the thermostatic bath 201. In order to calculate the fluorine concentration of phosphoric acid in the treatment tank 100, a conductivity meter 205 having a conductivity sensor 204 that measures the conductivity of the liquid in the heat retention vessel 203 is provided. Since the heat retaining container 203 here uses the conductivity sensor 204, a container having a certain depth is used. Further, the fluorine concentration in the phosphoric acid in the treatment tank 100 is calculated by arithmetic processing in a control circuit (microcomputer or the like) 300 which is the main control means of the apparatus based on the conductivity data measured by the conductivity meter. Is done. The control circuit 300 calculates the input amount of hydrofluoric acid and pure water according to the amount of phosphoric acid in the treatment tank 100, controls the metering pumps 110 and 107 to satisfy each calculated input amount, and controls the fluorine concentration. When the value becomes less than the specified value, the end of regeneration is notified, the automatic valves, needle valves, metering pumps, etc. of each part described above are controlled as necessary, and necessary signals are exchanged with the heater controller, etc. of each part. The entire wafer processing apparatus is controlled by giving and receiving.

On the other hand, the storage tank 113 stores the phosphoric acid regenerated in the processing tank 100 in a batch manner via the automatic valve 115, and replenishes the regenerated phosphoric acid to the overflow portion 3a via the supply pipe 67a. is there. The storage tank 113 includes a surface heater 116 and a surface heater 117 that heat the stored regenerated phosphoric acid to a predetermined temperature, a plurality of liquid level sensors (S8 to S10) 118 that measure the amount of phosphoric acid in the storage tank 113, and storage. A temperature sensor 119 for detecting the temperature of phosphoric acid in the tank 113 and a heater controller 120 for controlling the phosphoric acid in the storage tank 113 to a predetermined temperature based on the temperature detected by the temperature sensor 119 are provided. Further, the storage tank 113 and the overflow portion 3a are connected by a supply pipe 67a provided with an automatic valve 69 and a needle valve 70 on the overflow portion 3a side. The regenerated phosphoric acid in the storage tank 113 receives the signal from the liquid level sensors (S1 to S3) 36 by the control circuit 300, and overflows in response to a command transmitted from the control circuit 300 to the pump 68 and the needle valve 70. Replenished to 3a. Further, in this structure, the recycle phosphoric acid taken out from the storage tank 113 is provided with a supply pipe 67a for sending it to the overflow portion 3a and a circulation pipe 67b for returning it to the storage tank again. The circulation pipe 67b circulates the regenerated phosphoric acid in the storage tank 113 from the supply pipe 67a into the storage tank 113 again when the automatic valve 69 is closed.
(Apparatus Operation) Next, an outline of an operation or operation example of the above wafer processing apparatus will be described. First, when the nitride film-formed wafer 1 is placed in the wafer cassette 2 and placed in the etching bath 3 filled with heated phosphoric acid, the nitride film on the wafer 1 is etched by the hot phosphoric acid. The In this treatment process, hot phosphoric acid overflowing from the main body of the etching tank 3 is collected in the overflow portion 3 a, discharged from the discharge port 34 to the circulation filtration path portion 5, and sent to the filter 51 side by the pump 50. The phosphoric acid that has passed through the filter 51 is heated to a desired temperature (for example, the temperature just before the boiling point of phosphoric acid) by the line heater 52, and a predetermined amount of pure water is added to the heated phosphoric acid via the metering pump 55. Then, it is sent from the supply port 35 into the main body of the etching tank 3 and circulated. In this way, since phosphoric acid is circulated in the etching tank 3, the nitride film of the wafer 1 is appropriately etched. In this process, when the concentration of silicon oxide in phosphoric acid becomes high, the selective etching of the nitride film on the wafer 1 is not performed properly, and the silicon oxide deposition on the filter 51 increases, and the filtration pressure of the filter 51, that is, the circulation filtration path. The circulating fluid pressure in front of the filter 51 in the part 5 increases.

  In such etching, phosphoric acid etches a very small amount of quartz, which is the main constituent material of the etching tank 3, so that the silicon oxide concentration in phosphoric acid cannot be accurately estimated simply by the number of processed wafers 1. . However, the clogging of the filter 51 remains a good guideline for estimating the silicon oxide concentration in phosphoric acid, particularly when etching is performed at a high silicon oxide concentration close to the saturation dissolution value. It can be a very optimal guide. This is because, for example, when the filter 51 is new or phosphoric acid is new, that is, phosphoric acid has a low silicon oxide concentration, silicon oxide deposition on the filter 51 is small. In this case, if the pressure value (circulation fluid pressure) measured by the pressure gauge 61 is equal to or less than the first predetermined value (X1), the automatic valve 66 is closed so that phosphoric acid does not flow into the receiving tank 63 side. To do. This is because the selective etching of the nitride film of the wafer 1 is still appropriately performed by phosphoric acid that has undergone the filtration, heating, and pure water addition steps of the circulation filtration path portion 5. Here, when the processing operation time of the wafer 1 is long, or when the number of processed wafers 1 is large and the silicon oxide concentration in phosphoric acid becomes high (close to the saturation dissolution value), the circulating fluid pressure increases. Then, the amount of phosphoric acid branched off from the branch pipe 60 and recovered to the regeneration unit is automatically supplied to the receiving tank 63 in proportion to the circulating fluid pressure if the valve opening of the needle valve 65 is constant, for example. It will be taken out. As another control, when the pressure measured by the pressure gauge 61 is larger than the first predetermined value (X1) but less than the second predetermined value (X2), the needle valve 65 is adjusted to the measured pressure. The amount of phosphoric acid recovered from the circulation filtration path 5 and taken out to the receiving tank 63 is adjusted accordingly. Each of the predetermined values (X1) and (X2) is an empirically obtained value, and the larger the pressure measured by the pressure gauge 61, the larger the degree of opening of the needle valve 65 and the greater the amount recovered. Conversely, the smaller the pressure, the smaller the recovery amount. When the value is equal to or greater than the predetermined value (X2), the needle valve 65 is fully opened and a large amount is collected in a short time.

  When the phosphoric acid in the circulation filtration path section 5 flows into the receiving tank 63 through the branch pipe 60, the flow meter 62, the needle valve 65, and the automatic valve 65 by the control as described above, the receiving tank is associated with this. 63 phosphoric acid increases, and phosphoric acid in the etching tank 3 decreases. The flow meter 62 monitors the total amount of phosphoric acid recovered in the receiving tank 63 and obtains data necessary for subsequent processing via the control circuit 300. For example, the control circuit 300 controls the automatic valve 69 to be in an open state and supplies the regenerated phosphoric acid in the storage tank 113 through the needle valve 70 to an appropriate amount from the replenishing port 33 to the overflow portion 3a. The amount of phosphoric acid in the overflow portion 3a is detected by the liquid level sensor (S2) 36. When an appropriate amount is supplied, the automatic valve 69 is closed by a signal from the control circuit 300. The phosphoric acid replenished to the overflow part 3a flows into the circulation filtration path part 5 through the discharge port 34, and thereby the amount of phosphoric acid in the etching tank 3 is kept constant.

  In this case, since the regenerated phosphoric acid in the storage tank 113 is regenerated in the treatment tank 100 and has a low silicon oxide concentration, the silicon oxide concentration in the phosphoric acid in the etching tank 3 can be maintained at a low value accordingly. . Further, in the circulating filtration path section 5, since the phosphoric acid having a low silicon oxide concentration is sent from the pump 50 to the filter 51 side, the deposited silicon oxide on the filter 51 is redissolved and removed. This advantage is that when the phosphoric acid has a low silicon oxide concentration, the deposited silicon oxide of the filter 51 is redissolved so that the filter 51 can be used for a long time.

  Therefore, in this structure, not only the increase of the circulating fluid pressure (filtering pressure) due to clogging of the filter 51 is eliminated, but also the phosphoric acid in the etching tank 3 is reduced by decreasing the silicon oxide concentration in the phosphoric acid in the etching tank 3. Phosphoric acid is obtained in which the silicon oxide concentration has a desired etching rate ratio, that is, the etching selectivity ratio between the nitride film and the oxide film is large and the ratio is constant, and the silicon oxide does not reach the saturation dissolution value. If the circulating fluid pressure (filtering pressure) decreases, the amount of phosphoric acid in the circulation filtration path 5 that branches and flows to the phosphoric acid regenerating apparatus 6 can be reduced, or the time for stopping the branching of phosphoric acid can be lengthened. In addition, the nitride film mask of the wafer 1 is continuously etched under optimum conditions by phosphoric acid having a large etching selectivity ratio between the nitride film and the oxide film and a constant ratio thereof, and high-efficiency etching is maintained. In addition, the accuracy variation that easily occurs between the processing lots of the wafer 1 can be eliminated.

  On the other hand, phosphoric acid in the receiving tank 63 is put into the processing tank 100 through the automatic valve 101 and regenerated into phosphoric acid usable in the processing tank 100. In this regeneration process, an appropriate amount of hydrofluoric acid in the HF tank 109 is supplied into the processing tank 100 by the metering pump 110, and pure water is supplied into the processing tank 100 through the pure water supply pipe 108 by the measuring pump 107. The For the supply amount of the hydrofluoric acid and pure water, see, for example, the relevant part of JP-A-11-293479. In this regeneration process, the surface heaters 103 and 104 are controlled to increase the liquid temperature in the processing tank 100, and the evaporated vapor is guided to the cooler 200 from the vapor outlet 111 and returned to the liquid. This liquid flows into the heat insulating container 203 while being adjusted to a constant temperature through the spalar pipe in the thermostat 201. It should be noted that new liquid always flows into the heat retaining container 203 so that old liquid does not accumulate. The liquid that has flowed out of the heat insulating container 203 is subjected to necessary processing.

  Subsequently, the conductivity of the liquid in the heat retaining container 203 is measured by the conductivity meter 205 (conductivity sensor 204), and the measured data is stored in the storage unit of the control circuit 300. In the control circuit 300, the data is arithmetically processed to calculate the fluorine concentration, the time when the fluorine concentration becomes a conductivity corresponding to a desired value is determined, and the silicon oxide concentration in the phosphoric acid in the treatment tank 100 is a predetermined value. Determine when it is lower. The phosphoric acid in the treatment tank 100 is added with the above-mentioned hydrofluoric acid and added with pure water, so that the silicon oxide concentration in the phosphoric acid is lowered, and this phosphoric acid can be used for etching the nitride film of the wafer 1. When the concentration is reached, the automatic valve 115 is opened and discharged to the storage tank 113. The opening time of the automatic valve 115 is controlled depending on which of the liquid level sensors (S8, S9, S10) 118 detects the liquid level of the phosphoric acid in the storage tank 113.

  Moreover, when the phosphoric acid in the storage tank 113 is maintained at a predetermined temperature (for example, a temperature just before the boiling point) by the surface heaters 116 and 117 and replenished to the overflow part 3a, the circulation filtration path part 5 and the etching tank 3 It is processed so as not to cause a temperature drop of the phosphoric acid in the main body. And in the replenishment to the overflow part 3a, the automatic valve 69 is made into an open state, and the phosphoric acid in the storage tank 113 is supplied through the pump 68, the automatic valve 69, and the needle valve 70. In addition, the phosphoric acid in the storage tank 113 is normally circulated through the replenishment piping 67a through the needle valve 71 and the circulation piping 67b. The needle valve 71 is controlled so that the valve opening is minimized, for example, only when refilling the overflow portion 3a. This is to maintain the phosphoric acid temperature in the storage tank 113 as constant as possible. Moreover, the pure water supplied to the above circulation filtration path part 5 and the processing tank 100 is actually sent from the same pure water reservoir part through the illustrated piping.

As described above, in this structure, the fluorine concentration in the phosphoric acid in the treatment tank 100 is measured without being affected by temperature change or carbon dioxide in the air. The residual fluorine concentration can be measured with high accuracy, and the silicon oxide concentration in phosphoric acid can be estimated with high accuracy from the measured value of fluorine concentration. Further, the phosphoric acid solution regenerating apparatus 6 can suppress phosphoric acid as a waste solution as much as possible, and can suppress not only cost reduction but also adverse effects on the environment.
(Modifications) The present invention is not limited to the above embodiments, and various modifications and developments can be made within the scope of the technical requirements of the claims. For example, the regenerated phosphoric acid in the storage tank 113 may be supplied not to the overflow part 3 a but to the circulation filtration path part 5 or to the main body of the etching tank 3. When supplying to the circulation filtration path | route part 5, the form with which regenerated phosphoric acid joins the upstream of the filter 51 is preferable. This is because particles and the like contained in the regenerated phosphoric acid can be automatically removed by passing the regenerated phosphoric acid through the filter 51 before being supplied to the etching tank 3. Furthermore, when the form in which the regenerated phosphoric acid joins the upstream side of the line heater 52 and the metering pump 55 is adopted, the concentration of phosphoric acid is obtained by supplying pure water from the metering pump 55 before the regenerated phosphoric acid is supplied to the etching tank 3. Adjustment can be performed efficiently, and temperature adjustment can be performed efficiently with a line heater. Further, when the capacity of the etching tank 3 is large, the processing tanks 100 may be provided in pairs, and the recovered phosphoric acid in the receiving tank 63 may be introduced into both the processing tanks 100 by a switching method and regenerated. On the other hand, the storage tank 113 that stores the regenerated phosphoric acid may be provided with a metering pump to supply pure water. In this case, the concentration of the regenerated phosphoric acid can be adjusted while being stored in the storage tank 113. That is, since the regenerated phosphoric acid in the storage tank 113 can always be used in the etching process as it is, the regenerated phosphoric acid in the storage tank 113 is used as it is for the etching process. The supply time can be shortened.

  Further, when the phosphoric acid is continuously sent from the etching tank 3 to the phosphoric acid regenerating apparatus 6, the phosphoric acid may be sent via an air vent line of a filter 51 connected to the circulation filtration path unit 5. In this case, it is set so that the same amount of regenerated phosphoric acid sent to the phosphoric acid regenerating apparatus 6 is supplied to the etching tank 3. Here, the air vent line is a pipe provided in the filter 51 in order to remove air mixed in the circulation filtration path 5. When the phosphoric acid in the etching tank 3 is replaced or when the amount of circulating phosphoric acid is reduced, air is mixed into the circulation filtration path 5 from the discharge port 34. If the circulation is continued as it is, the mixed air stays in the filter 51, and the filtering material in the filter 51 is dried to reduce the filtering ability. Therefore, it is necessary to remove the air in the filter 51. Generally, the piping of the air vent line is connected to the overflow part 3a of the etching tank 3, and a small amount of phosphoric acid is always supplied to the overflow part 3a even when air is not mixed. Therefore, by using this air vent line pipe, it is possible to separately use the branch pipe 60 and the air vent line, and the configuration of the apparatus can be further simplified.

  Further, as another method for sending phosphoric acid from the etching tank 3 to the phosphoric acid regenerating apparatus 6, a mode in which phosphoric acid is intermittently sent to the phosphoric acid regenerating apparatus 6 may be used. In this embodiment, when the wafer cassette 2 containing the wafer 1 is carried into the etching tank 3, the same amount of phosphoric acid overflows into the overflow portion 3a. The overflowed phosphoric acid is detected by the liquid level sensor (S1) 36 in the overflow portion 3a, and is recovered by the phosphoric acid regenerating apparatus 6 by opening the automatic valve 66 with a signal from the control circuit 300. Then, after the appropriate amount is recovered, the liquid level sensor (S1 to S3) 36 detects a decrease in the amount of phosphoric acid in the overflow portion 3a, and the automatic valve 66 is closed by a signal from the control device 300. Stop. Further, when the wafer cassette 2 is carried out of the etching tank 3, the amount of phosphoric acid in the overflow portion 3a is reduced by the same amount as its volume. The amount of phosphoric acid thus reduced is detected by the liquid level sensors (S2 to S3) 36 in the overflow portion 3a, and the automatic valve 69 is opened by a signal from the control device 300, so that the regenerated phosphoric acid is removed from the etching tank. 3 is supplied. When a part of phosphoric acid in the etching tank 3 is intermittently replaced with regenerated phosphoric acid, the concentration of silicon oxide contained in the phosphoric acid in the etching tank 3 increases as the number of wafers processed increases. Therefore, it is preferable to match the timing of intermittently replacing the phosphoric acid in the etching tank with the regenerated phosphoric acid with the timing of newly processing the wafer. Therefore, it is preferable that the phosphoric acid overflowing when the wafer cassette 2 is carried into the etching tank 3 is sent to the phosphoric acid regenerating apparatus 6.

  Furthermore, a filter that filters the regenerated phosphoric acid regenerated in the treatment tank 100 until it is supplied to the overflow portion 3a may be provided. In this case, the filtration unit may be provided in a pipe between the processing tank 100 and the storage tank 113, or may be provided in the supply pipes 67a and 67b. It is also possible to newly provide an in-storage circulation path connected to the storage tank 113 and provide a filtration unit in the in-storage circulation path. In this case, the regenerated phosphoric acid in the storage tank 113 flows from the storage tank 113 to the in-storage circulation path, and after being filtered by the filtration unit, is recirculated to the storage tank 113. Similarly, a circulation path in the treatment tank connected to the treatment tank 100 can be newly provided, and a filtration unit can be provided in the circulation path in the treatment tank.

It is a whole schematic block diagram which shows the wafer processing apparatus of this invention. It is a block diagram which made the main part the etching part and circulation filtration path | route part of FIG. FIG. 2 is a configuration diagram mainly including a playback unit in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor wafer (to-be-processed object), 3 ... Etching tank (processing tank), 3a ... Overflow part, 4 ... Etching part, 5 ... Circulation filtration path part (circulation path part), 6 ... Phosphate regenerator (chemical solution processing) Part), 7 ... regenerating part, 51 ... filter (filtering part), 60 ... branch pipe, 61 ... pressure gauge (flow rate adjusting means), 62 ... flow meter (flow rate adjusting means), 63 ... receiving tank, 65 ... needle valve (Flow rate adjusting means), 67a ... replenishment piping, 68a ... circulation piping, 100 ... treatment tank, 109 ... hydrofluoric acid tank (HF tank), 112 ... measuring section, 113 ... storage tank, 200 ... cooler, 201 ... constant temperature bath (Including spiral tube), 202 ... temperature controller, 203 ... heat insulation container, 204 ... conductivity sensor, 205 ... conductivity meter (fluorine meter), 300 ... control circuit (control means)

Claims (10)

An etching tank with an overflow part for etching a semiconductor wafer with hot phosphoric acid, and circulation in which the phosphoric acid overflowing the overflow part is guided outside the etching tank, filtered, heated and added with pure water. A filtration path section, a phosphoric acid regenerating apparatus for adding a hydrofluoric acid to the phosphoric acid taken out from the circulation filtering path section through a branch pipe, and a replenishment for replenishing the etching tank with the phosphoric acid regenerated by the phosphoric acid regenerating apparatus. In a processing apparatus equipped with piping,
The branch pipe is provided in front of the filtration section for filtering phosphoric acid in the circulation filtration path section, and a flow rate adjusting means capable of controlling the amount of phosphoric acid branched to the phosphoric acid regenerating apparatus side according to the circulating fluid pressure flowing to the filtration section. A processing apparatus characterized by comprising: The phosphoric acid regenerating apparatus includes a receiving tank for temporarily storing phosphoric acid branched by the branch pipe, a processing tank for adding and heating hydrofluoric acid to phosphoric acid introduced from the receiving tank, and phosphoric acid regenerated in the processing tank. Consisting of a temporary storage tank,
The treatment tank includes a cooler that cools and liquefies vapor evaporated from the treatment tank, a thermostat that adjusts the liquid liquefied by the cooler to a constant temperature, and fluorine in the liquid adjusted in the thermostat. The processing apparatus of Claim 1 which has a measurement part which consists of a fluorine measuring device etc. which measure a density | concentration. The processing apparatus according to claim 2, wherein the fluorine measuring instrument is a specific resistance meter or a conductivity meter. The said storage tank has a heating means which controls the regenerated phosphoric acid introduced from the said processing tank to predetermined temperature, and is connected with the said overflow part by the said supplementary piping. And the processing apparatus according to 2. The processing apparatus according to claim 4, wherein the amount of phosphoric acid replenished sent from the storage tank can be controlled by a signal from a liquid level gauge provided in the overflow portion. The said supply piping is comprised so that switching is possible between the path | route which sends the regenerated phosphoric acid taken out from the said storage tank to the said etching tank or the said overflow part, and the circulation path which returns to a storage tank again. Processing equipment. A treatment tank comprising a treatment tank for treating an object to be treated with a chemical liquid, a circulation path section for guiding the chemical liquid in the treatment tank to the outside of the tank and returning it to the treatment tank again, and a chemical liquid treatment section for processing the chemical liquid. In the device
A processing apparatus comprising flow rate adjusting means for controlling a flow rate of the chemical solution sent to the chemical solution processing unit in accordance with a liquid pressure of the chemical solution flowing in the circulation path unit. The processing apparatus according to claim 7, wherein the circulation path unit includes a filtering unit that filters the chemical solution, and the hydraulic pressure is mainly a hydraulic pressure that is generated when the chemical solution passes through the filtering unit. The circulation path section includes a first circulation path section that sends the chemical solution from the treatment tank to the filtration section, and a second circulation path section that sends the chemical solution that has passed through the filtration section to the treatment tank from the filtration section. Including
The processing apparatus according to claim 8, further comprising a branch pipe that connects the first circulation path section and the chemical liquid processing section, and the chemical liquid is sent to the chemical liquid processing section via the branch pipe. 10. A semiconductor device manufacturing method for manufacturing a semiconductor device such as a wafer using the processing apparatus according to claim 1.

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