JP2010166092A - Method for plasma etching - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for plasma etching which avoids generation of a fence, while being able to etch Ti at a high etching rate, inhibiting the generation of a deposit in a chamber in the process of an etching, and which is capable of preventing particle contamination. <P>SOLUTION: The method for plasma etching includes a first plasma treatment process in which the plasma of an etching gas comprising a fluorine compound is worked on a body to be treated, to which a Ti layer as a layer to be etched formed under the mask layer are formed, at a pressure of 4 Pa or less in a chamber. The method for plasma etching, further, includes a second plasma treatment process which dry-cleans the inside of the treating chamber by the plasma of a cleaning gas after the first plasma treatment process. The cleaning gas, which consist of only one gas selected from a group of fluorine compound, gas mixture of fluorine compound and noble gas, and oxygen, removes the deposit comprising a Ti compound generated by the first plasma treatment process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma etching method, and more particularly, to a plasma etching method for etching a metal film such as Ti using a reactive gas plasma.

In a semiconductor device, a metal such as titanium (Ti) is used, for example, as a wiring material, and is silicided for the purpose of reducing parasitic resistance of a MOS transistor or the like. For example, in the process of manufacturing a MOS transistor, a process of forming a Ti film on the surface of a gate electrode or a diffusion layer and then performing a heat treatment to form a silicide and remove an unreacted Ti film is performed. As a technique for removing the Ti film formed on the substrate by etching, a method of performing dry etching using plasma of a CF ₄ etching gas has been proposed (for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 53-118372 (FIGS. 1-5, etc.) JP-A-56-66040 (Claims etc.)

  In general, from the viewpoint of improving throughput, a higher etching rate is preferable, and it is required to realize processing at a high etching rate even when etching is performed on a Ti film. However, none of the above prior art methods takes into account increasing the etching rate. For example, in the method of Patent Document 2, only an etching rate of about 30 to 40 nm / min is obtained even in etching after performing pre-etching in order to speed up the rise (see the same document, FIG. 1). It cannot meet the demand for high-speed etching.

  On the other hand, when the Ti film is etched at a high speed by the plasma of the CF-based gas described in Patent Documents 1 and 2, a re-deposition phenomenon of an etching residue called a fence may occur. This phenomenon is that etching residues such as Ti are scattered by a strong sputtering action during high-speed etching, and are reattached to the side surfaces of the photoresist and other metal materials. Since this fence causes contamination by Ti, it is required to avoid it as much as possible.

  In addition, when the Ti film is plasma etched, a large amount of deposits in the chamber are formed. This deposit causes particle contamination, which hinders the manufacture of a highly reliable semiconductor device. Therefore, it is necessary to take measures against deposits in the chamber in the plasma etching of the Ti film.

  Accordingly, an object of the present invention is to provide a plasma etching method capable of etching Ti at a high etching rate while avoiding the generation of a fence, and further, the generation of deposits in the chamber during the etching process. It is an object of the present invention to provide a plasma etching method capable of suppressing and preventing particle contamination.

In order to solve the above-described problem, according to a first aspect of the present invention, a mask layer in which a pattern of at least a predetermined shape is formed, and a mask layer formed under the mask layer in a processing container that can be maintained in a vacuum. For the object to be processed in which the Ti layer as the layer to be etched is formed,
A first plasma treatment step of etching the Ti layer by applying a plasma of an etching gas containing a fluorine compound at a chamber internal pressure of 4 Pa or less;
A second plasma processing step of dry-cleaning the inside of the processing chamber with a cleaning gas plasma after completion of the first plasma processing step;
A cleaning gas used in the second plasma treatment step is a gas composed of only one gas selected from the group consisting of a fluorine compound, a mixed gas of a fluorine compound and a rare gas, and oxygen, In the plasma processing step, a plasma etching method is provided, in which the deposit containing the Ti compound generated in the first plasma processing step is removed.

In the plasma etching method of the first aspect, it is preferable that the first plasma processing step and the second plasma processing step are alternately repeated. The cleaning gas used in the second plasma treatment step is preferably a gas containing a fluorine compound or oxygen. Here, as the fluorine compound, NF ₃ or CF ₄ is preferable.
Moreover, it is preferable that the chamber internal pressure in the said 2nd plasma processing process is 6.7 Pa or less.

  According to a second aspect of the present invention, there is provided a control program that operates on a computer and controls the plasma processing apparatus so that the plasma etching method according to the first aspect is performed at the time of execution. Is done.

According to a third aspect of the present invention, there is provided a computer storage medium storing a control program that operates on a computer,
A computer storage medium is provided in which the control program controls a plasma processing apparatus used in the plasma etching method of the first aspect at the time of execution.

According to a fourth aspect of the present invention, a plasma supply source for generating plasma;
A processing container for partitioning a processing chamber for performing an etching process on an object to be processed by the plasma;
A support for placing the object to be processed in the processing container;
An exhaust means for decompressing the inside of the processing vessel;
Gas supply means for supplying gas into the processing vessel;
A control unit for controlling the plasma etching method of the first aspect to be performed;
A plasma etching apparatus is provided.

According to the plasma etching method of the present invention, a Ti film can be etched while maintaining a high etching rate by using a gas containing a fluorine compound as an etching gas and performing plasma etching under a predetermined low pressure condition. Can be effectively prevented.
In addition, by combining plasma etching and plasma cleaning under specified conditions, accumulation of deposits in the chamber can be suppressed, thus preventing particle contamination and increasing the reliability of semiconductor devices. become.

Sectional drawing which shows schematic structure of the magnetron RIE plasma etching apparatus for enforcing the method concerning this invention. The horizontal sectional view which shows typically the dipole ring magnet of the state arrange | positioned around the chamber of the apparatus of FIG. The schematic diagram for demonstrating the electric field and magnetic field which are formed in a chamber. The procedure of the plasma etching method which concerns on 1st Embodiment of this invention is shown, (a) is at the time of an etching, (b) is a figure which shows the state after completion | finish of an etching process. The graph which shows the waveform separation result by the XPS analysis of the deposit in a chamber after a plasma etching process. The flowchart which shows the process sequence of the plasma etching method which concerns on 2nd Embodiment of this invention. The graph which shows the measurement result of the thickness of the deposit in an upper top plate after changing processing gas and performing cleaning processing. The graph which shows the measurement result of the thickness of the deposit in an upper top plate after changing a pressure and performing a cleaning process. 6 is a graph showing the relationship between the number of wafers processed and particles in plasma etching.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an outline of a magnetron RIE type plasma etching apparatus 100 that can be suitably used for the purpose of carrying out the method of the present invention. This etching apparatus 100 is airtight, has a stepped cylindrical shape composed of a small-diameter upper portion 1a and a large-diameter lower portion 1b, and has a wall (processing vessel) 1 made of, for example, aluminum.

  In the chamber 1, there is provided a support table 2 for horizontally supporting a semiconductor wafer (hereinafter simply referred to as “wafer”) W, which is a silicon substrate on which a Ti film is formed as an object to be processed. The support table 2 is made of aluminum, for example, and is supported by a conductor support 4 via an insulating plate 3. A focus ring 5 made of, for example, Si or quartz is provided on the outer periphery above the support table 2. The support table 2 and the support table 4 can be moved up and down by a ball screw mechanism including a ball screw 7, and a drive portion below the support table 4 is covered with a bellows 8 made of stainless steel (SUS). . A bellows cover 9 is provided outside the bellows 8. A baffle plate 10 is provided outside the focus ring 5. The chamber 1 is grounded.

  An exhaust port 11 is formed on the side wall of the lower portion 1 b of the chamber 1, and an exhaust system 12 is connected to the exhaust port 11. The inside of the chamber 1 can be depressurized to a predetermined degree of vacuum by operating a vacuum pump of the exhaust system 12. On the other hand, a gate valve 13 for opening and closing the loading / unloading port for the wafer W is provided on the upper side wall of the lower portion 1 b of the chamber 1.

  The support table 2 is connected to a first high-frequency power source 15 for plasma formation via a matching unit 14, and high-frequency power of a predetermined frequency is supplied from the first high-frequency power source 15 to the support table 2. It is like that. On the other hand, a shower head 20, which will be described later in detail, is provided in parallel with each other so as to face the support table 2, and the shower head 20 is grounded. Therefore, the support table 2 and the shower head 20 function as a pair of electrodes.

  An electrostatic chuck 6 for electrostatically attracting and holding the wafer W is provided on the surface of the support table 2. The electrostatic chuck 6 is configured by interposing an electrode 6a between insulators 6b, and a DC power source 16 is connected to the electrode 6a. When a voltage is applied to the electrode 6a from the power source 16, the wafer W is attracted by electrostatic force, for example, Coulomb force.

  A temperature control medium chamber 17 is provided inside the support table 2, and the temperature control medium chamber 17 is introduced into the temperature control medium chamber 17 through the introduction pipe 17 a, discharged from the discharge pipe 17 b, and circulated. The heat (hot heat, cold heat) is transferred to the wafer W via the support table 2, whereby the processing surface of the wafer W is controlled to a desired temperature.

  Further, even when the chamber 1 is evacuated by the exhaust system 12 and kept in a vacuum, the temperature of the wafer W can be effectively adjusted by the temperature adjustment medium circulated to the temperature adjustment medium chamber 17. The gas is introduced at a predetermined pressure (back pressure) between the surface of the electrostatic chuck 6 and the back surface of the wafer W through the gas supply line 19 by the gas introduction mechanism 18. By introducing the gas as the heat transfer medium in this way, the heat of the temperature adjustment medium is effectively transmitted to the wafer W, and the temperature adjustment efficiency of the wafer W can be increased.

  The shower head 20 is provided on the top wall portion of the chamber 1 so as to face the support table 2. The shower head 20 is provided with a large number of gas discharge holes 22 on the lower surface thereof, and has a gas introduction part 20a on the upper part thereof. And the space 21 is formed in the inside. A gas supply pipe 23a is connected to the gas introduction part 20a, and a processing gas supply system 23 for supplying a processing gas such as an etching gas or a cleaning gas is connected to the other end of the gas supply pipe 23a.

  Such a processing gas reaches the space 21 of the shower head 20 from the processing gas supply system 23 via the gas supply pipe 23a and the gas introduction part 20a, and is discharged from the gas discharge hole 22.

  On the other hand, a pair of upper and lower dipole ring magnets 24 a and 24 b are arranged concentrically around the upper portion 1 a of the chamber 1. As shown in the horizontal sectional view of FIG. 2, each of the dipole ring magnets 24a and 24b is configured by attaching a plurality of anisotropic segment columnar magnets 31 to a ring-shaped magnetic casing 32. In this example, 16 anisotropic segment columnar magnets 31 having a cylindrical shape are arranged in a ring shape. In FIG. 2, the arrows shown in the anisotropic segment columnar magnet 31 indicate the direction of magnetization. As shown in this figure, the magnetization directions of the plurality of anisotropic segment columnar magnets 31 are gradually shifted. Thus, a uniform horizontal magnetic field B directed in one direction as a whole is formed.

  Therefore, in the space between the support table 2 and the shower head 20, as shown schematically in FIG. 3, a vertical electric field EL is formed by the first high frequency power supply 15, and the dipole ring magnets 24 a and 24 b are formed. As a result, a horizontal magnetic field B is formed, and a magnetron discharge is generated by the orthogonal electromagnetic field thus formed. As a result, plasma of an etching gas in a high energy state is formed, and the wafer W is etched.

  Each component of the plasma etching apparatus 100 is connected to and controlled by a process controller 50 having a CPU. The process controller 50 includes a user interface 51 including a keyboard on which a process manager inputs commands to manage the plasma etching apparatus 100, a display that visualizes and displays the operating status of the plasma etching apparatus 100, and the like. Is connected.

  In addition, the process controller 50 includes a storage unit 52 that stores a recipe in which a control program for realizing various processes executed by the plasma etching apparatus 100 under the control of the process controller 50 and processing condition data are stored. It is connected.

  Then, if necessary, an arbitrary recipe is called from the storage unit 52 by an instruction from the user interface 51 and is executed by the process controller 50, so that the plasma etching apparatus 100 can control the process under the control of the process controller 50. Desired processing is performed. The recipe may be stored in a readable storage medium such as a CD-ROM, a hard disk, a flexible disk, or a nonvolatile memory, or may be a dedicated line from another device, for example. It is also possible to transmit and use it as needed.

Next, a plasma etching method according to the first embodiment of the method of the present invention using the plasma etching apparatus 100 configured as described above will be described with reference to FIG. 4 as appropriate.
First, the gate valve 13 of FIG. 1 is opened, and the wafer W is loaded into the chamber 1 and placed on the support table 2. Then, the support table 2 is raised to the position shown in the figure, and is evacuated by a vacuum pump of the exhaust system 12. The chamber 1 is evacuated through the port 11. As shown in FIG. 4A, the wafer W in this state has a structure in which an SiO ₂ layer 102 as an insulating oxide film, a Ti layer 103 as an etching target layer, and a mask layer 104 are stacked on an Si substrate 101. is doing. The mask layer 104 is not particularly limited as long as it has an etching selectivity with respect to the Ti layer 103. For example, a photoresist, a hard mask made of metal, or an upper layer formed by another process can be used. . In addition, a pattern having a predetermined shape is formed on the mask layer 104.

  Then, a processing gas including an etching gas and a dilution gas is introduced into the chamber 1 from the processing gas supply system 23 at a predetermined flow rate, the pressure in the chamber 1 is 4 Pa (30 mTorr) or less, and the temperature of the wafer W (support table 2) is set. A predetermined high frequency power is supplied from the first high frequency power supply 15 to the support table 2 in this state. From the viewpoint of increasing the etching rate, the high frequency power for generating plasma is preferably, for example, 2000 W or more, and more preferably about 3000 to 5000 W. At this time, the wafer W is attracted and held on the electrostatic chuck 6 by, for example, Coulomb force when a predetermined voltage is applied to the electrode 6a of the electrostatic chuck 6 from the DC power supply 16, and the shower head which is the upper electrode. A high frequency electric field is formed between 20 and the support table 2 which is a lower electrode. Since a horizontal magnetic field B is formed between the shower head 20 and the support table 2 by the dipole ring magnets 24a and 24b, an orthogonal electromagnetic field is formed in the processing space between the electrodes on which the wafer W is present. Magnetron discharge is generated by the drift of the generated electrons. Then, the wafer W is etched by the plasma of the etching gas formed by this magnetron discharge. In this case, in normal etching, by setting the gas pressure in the chamber 1 to be high, not only charged particles of ions and electrons but also a sufficient amount of radicals can be generated. The etching rate can be improved by acting. In addition, since the sputtering effect is increased and the fence is likely to be generated when the pressure is low, a relatively high pressure condition of 6.7 Pa (50 mTorr) or more is adopted in this etching from this viewpoint. However, in the present embodiment, in the plasma etching of the Ti layer 103, as described later, a low pressure condition of 4 Pa or less (that is, a range of 0 to 4 Pa) is used, thereby preventing the generation of a fence, for example, 90 High-speed etching of ˜140 nm / min can be realized.

  In this embodiment, RIE type plasma generation mechanism is used and high frequency power is applied to the support table 2 which is a lower electrode on which the wafer W is placed, so that plasma can be formed immediately above the object to be processed. Etching while forming a magnetic field orthogonal to the electric field between the electrodes can draw spiral orbits on the electrons and increase the chances of collision with gas molecules. Is realized. Thus, etching can be performed at a higher speed.

As the processing gas used in the first etching step, it is preferable to use a highly reactive fluorine compound-containing gas from the viewpoint of etching the wafer W at a high speed. Examples of the fluorine compound, for _example, a _{CF 4, C 3 F 8,} SF 6, S 2 F 10, CHF 3, CH 2 F 2, C 4 F 8 or the like. In addition to these fluorine compounds, for example, a rare gas such as Ar, Xe, or Kr or an inert gas such as N ₂ can be used.

  Further, a gas of a heat transfer medium for effectively supplying heat (hot or cold) to the wafer W through the gas supply line 19 by the gas introduction mechanism 18 is between the surface of the electrostatic chuck 6 and the back surface of the wafer W. At a predetermined pressure (back pressure). As this gas, for example, He or the like can be used.

  The frequency and output of the first high frequency power supply 15 for generating plasma are appropriately set in order to form a desired plasma. From the viewpoint of increasing the plasma density directly above the wafer W, the frequency is preferably 10 MHz or more.

  The dipole ring magnets 24a and 24b apply a magnetic field to the processing space between the support table 2 as the counter electrode and the shower head 20 in order to increase the plasma density directly above the wafer W, but the effect is effectively exhibited. In order to achieve this, it is preferable that the magnet be strong enough to form a magnetic field of 10,000 μT (100 G) or more in the processing space. It is considered that the stronger the magnetic field is, the higher the effect of increasing the plasma density is. However, from the viewpoint of safety, it is preferably 100000 μT (1 kG) or less.

In the etching process, as shown in FIG. 4A, the Ti layer 103 is etched by, for example, CF ₄ gas plasma. At this time, in the method of the present invention, high-speed etching at a high etching rate of, for example, 90 to 140 nm / min is possible. In the case of the plasma etching process at a low pressure of 4 Pa or less, Ti constituting the Ti layer 103 becomes TiF _{4 and} is evaporated by the low vapor pressure. This low-pressure etching mechanism prevents the generation of a fence. Then, Ti that has formed the Ti layer 103 by etching is removed from the SiO ₂ layer 102 except for the region masked by the mask layer 104. The remaining Ti layer 103 is patterned in the same pattern as the mask layer 104 as shown in FIG.

Here, the test result which confirmed the effect of this invention is described.
With the plasma etching apparatus 100 having the same configuration as that of FIG. 1, CF ₄ and Ar are used as etching gases for the wafer W having the Ti layer 103 having the same configuration as that of FIG. Plasma etching was performed.

<Condition 1>
Magnetic field strength = 12000 μT (120 G) gradient magnet;
Magnetic field gradient = 8.53 deg. ;
Pressure in chamber 1 = 4 Pa (30 mTorr);
High frequency power = 4000 W;
CF ₄ / Ar flow rate = 300/600 ml / min (sccm);
Distance between upper and lower electrodes (distance between the lower surface of the shower head 20 and the upper surface of the support table 2, the same applies hereinafter) = 40 mm;
He back pressure (center portion / edge portion) = 1333 / 3332.5 Pa (10/25 Torr);
Temperature of shower head 20 = 60 ° C;
Temperature of side wall of chamber 1 = 60 ° C .;
Temperature of support table 2 = 50 ° C .;
Processing time = 53.7 seconds

<Condition 2>
Plasma etching was performed in the same manner as in Example 1 except that the pressure in the chamber was 6.7 Pa and the processing time was 94.8 seconds.

After the plasma etching process, each of the wafers 1 under the conditions 1 and 2 was observed with a scanning electron microscope (SEM). A vertical stripe-like fence was observed on the side wall of the mask layer 104. On the other hand, in the case of condition 1, the occurrence of a fence was not observed (both the results are not shown).
Further, when the deposit in the chamber 1 was analyzed by XPS after the etching under the condition 1, a Ti peak was detected. The result of waveform separation of this Ti peak is shown in FIG. From this FIG. 5, it was confirmed that most of Ti contained in the deposit exists as TiF ₄ .
In condition 2, which is a high pressure treatment of 6.7 Pa, although the etching rate was as high as 140 nm / min, a fence was generated as described above, and therefore a phenomenon peculiar to etching the Ti layer 103 with fluorine-containing gas plasma. As a result, it was confirmed that there is a trade-off between the etching rate improvement and the fence suppression. On the other hand, under the condition 1, while preventing the generation of the fence, the etching rate was 90 nm / min, and high-speed etching was realized at a practically sufficient etching rate.

From the above, by performing an etching process under a low pressure condition of 4 Pa or less with plasma of a fluorine-containing gas, Ti constituting the Ti layer 103 can be changed to TiF ₄ and evaporated to be removed. It has been confirmed that the etching by this method can prevent the occurrence of a fence in which Ti adheres to the photoresist or other metal film by sputtering.

Next, a plasma etching method according to a second embodiment of the present invention in which the cleaning process for the chamber 1 is combined with the plasma etching method of the first embodiment will be described. When the plasma etching process of the first embodiment is performed, a large amount of deposits are generated in the chamber 1. XPS analysis of this deposit revealed that TiF ₄ and a CF compound were mixed. Since this deposit is in the form of powder, particles adhere to and accumulate on parts around the wafer W, in particular, the upper top plate (a member disposed below the shower head 20 in FIG. 1; not shown). Cause. For this reason, the plasma etching process can be stably performed by combining the dry etching process with the plasma etching process.

  FIG. 6 is a flowchart showing a processing procedure of the plasma etching method according to the second embodiment. First, in step S101, a Ti blanket wafer on which the Ti layer 103 is formed is carried into the chamber 1, and in step S102, a plasma etching process is performed. The plasma etching process in step S101 and step S102 is performed in the same manner as in the first embodiment.

After completion of the plasma etching process, in step S103, after performing necessary processes such as pressure adjustment after the etching, the gate valve 13 in FIG. 1 is opened and the wafer W is unloaded from the chamber 1. Next, in step S <b> 104, the bare Si wafer is carried into the chamber 1. A bare Si wafer is a clean wafer on which no film is formed.
In step S105, a plasma cleaning process is performed on the bare Si wafer. As a processing gas in the plasma cleaning, for example, a fluorine compound such as NF ₃ or CF ₄ or a gas containing O ₂ is preferably used. Further, the processing gas can include, for example, a rare gas such as Ar, Xe, Kr, and He and an inert gas such as N ₂ . The pressure of the cleaning process in step S105 is preferably 6.7 Pa or less (that is, a range of 0 to 6.7 Pa) from the viewpoint of improving the cleaning efficiency, more preferably 4 Pa or less, and preferably 2 Pa or less. Further, the temperature of the cleaning treatment is preferably 50 ° C. or higher, and more preferably 80 ° C. or higher.

Here, the result of studying the influence of the type of processing gas on the cleaning effect will be described. Three types of processing gas, CF ₄ / Ar mixed gas, NF ₃ / Ar mixed gas, and O ₂ gas (single), were cleaned under the conditions shown below, and the thickness of the deposit on the upper top plate was adjusted. It was measured.

CF ₄ / Ar gas:
Magnetic field strength = 12000 μT (120 G) gradient magnet;
Magnetic field gradient = 8.53 deg. ;
Pressure in chamber 1 = 4 Pa (30 mTorr);
High frequency power = 4000 W;
CF ₄ / Ar flow rate = 300/600 ml / min (sccm);
Distance between upper and lower electrodes = 40 mm;
He back pressure (center portion / edge portion) = 1333 / 3332.5 Pa (10/25 Torr);
Temperature of shower head 20 = 80 ° C .;
Temperature of side wall of chamber 1 = 60 ° C .;
Temperature of support table 2 = 50 ° C .;
Processing time = 90 seconds

NF ₃ / Ar gas:
The test was carried out under the same conditions as in the case of CF ₄ / Ar gas except that NF ₃ / Ar gas was used.

O ₂ gas:
O ₂ flow rate = 900 ml / min (sccm), magnetic field gradient = 12.88 deg. Except that, it was carried out under the same conditions as in the case of CF ₄ / Ar gas.

The measurement points of the deposit are the central part (C) and the outermost edge part (E3) of the upper top plate, and the intermediate part (M) and the first edge in order from the central part (C) side between them at substantially equal intervals. The portion (E1) and the second edge portion (E2) were used (hereinafter the same). The results are shown in FIG.
From FIG. 7, the most effective gas is NF ₃ / Ar, O ₂ has the action of cleaning the upper top plate almost entirely, and CF ₄ / Ar is the second gas system compared to the other two gas systems. It was found that the cleaning effect of one edge portion (E1) was weak. From this result, for example, by NF ₃ / Ar gas alone, and by CF ₄ / Ar gas treatment, combined with O ₂ gas treatment, for example by performing O ₂ gas treatment after CF ₄ / Ar gas treatment, A sufficient cleaning effect can be expected.

Next, FIG. 8 shows the result of studying the influence of the processing pressure on the cleaning effect. Using O ₂ gas (single), cleaning was carried out under the following conditions under different pressures (gas flow rates), and the thickness of the deposit on the upper top plate was measured.

Cleaning conditions:
Magnetic field strength = 12000 μT (120 G) gradient magnet;
Magnetic field gradient = 12.88 deg. ;
Pressure in chamber 1 = 4 Pa (30 mTorr) or 2 Pa (15 mTorr);
High frequency power = 4000 W;
O ₂ flow rate = 900 ml / min (sccm) or 450 ml / min (sccm);
Distance between upper and lower electrodes = 40 mm;
He back pressure (center portion / edge portion) = 1333 / 3332.5 Pa (10/25 Torr);
Temperature of shower head 20 = 80 ° C .;
Temperature of side wall of chamber 1 = 60 ° C .;
Temperature of support table 2 = 50 ° C .;
Processing time = 90 seconds

  From FIG. 8, it was shown that by reducing the pressure in the chamber from 4 Pa (30 mTorr) to 2 Pa (15 mTorr), the film thickness of the deposit becomes thinner in almost the entire area of the upper top plate, and the cleaning effect is improved.

  In the processing procedure of FIG. 6, after the cleaning is completed, after performing necessary processing such as pressure adjustment, the gate valve 13 of FIG. 1 is opened and the wafer W is unloaded from the chamber 1 in step S <b> 106. Next, the process returns to step S101 again, and a new Ti blanket wafer is processed. The cleaning can be performed after etching a certain number of wafers W (for example, one lot). However, as shown in FIG. 6, every time one Ti blanket wafer is plasma-etched, It is preferable to perform plasma cleaning. As a result, deposits in the chamber 1 are removed, and a stable plasma etching process can be performed while preventing particle contamination.

  FIG. 9 shows the result of measuring the number of particles of 0.5 μm or more with a particle counter when the Ti blanket wafer was plasma etched under the following conditions according to the flowchart of FIG. For comparison, the results when cleaning was not performed are also shown.

Etching conditions:
Magnetic field strength = 12000 μT (120 G) gradient magnet;
Magnetic field gradient = 8.53 deg. ;
Pressure in chamber 1 = 4 Pa (30 mTorr);
High frequency power = 4000 W;
CF ₄ / Ar flow rate = 300/600 ml / min (sccm);
Distance between upper and lower electrodes = 40 mm;
He back pressure (center portion / edge portion) = 1333 / 3332.5 Pa (10/25 Torr);
Temperature of shower head 20 = 60 ° C;
Temperature of side wall of chamber 1 = 60 ° C .;
Temperature of support table 2 = 50 ° C .;
Processing time = 90 seconds

Cleaning conditions:
Magnetic field strength = 12000 μT (120 G) gradient magnet;
Magnetic field gradient = 8.53 deg. ;
Pressure in chamber 1 = 4 Pa (30 mTorr);
High frequency power = 4000 W;
NF ₃ / Ar flow rate = 300/600 ml / min (sccm);
Distance between upper and lower electrodes = 40 mm;
He back pressure (center portion / edge portion) = 1333 / 3332.5 Pa (10/25 Torr);
Temperature of shower head 20 = 80 ° C .;
Temperature of side wall of chamber 1 = 60 ° C .;
Temperature of support table 2 = 50 ° C .;
Processing time = 90 seconds

  From FIG. 9, when plasma cleaning is not performed, the number of particles increases as the number of processed Ti blanket wafers increases. On the other hand, it has been shown that a highly reliable semiconductor device can be manufactured with few particles generated by performing plasma cleaning of a single wafer.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.
For example, in the above embodiment, a dipole ring magnet is used as the magnetic field forming means of the magnetron RIE plasma etching apparatus 100. However, the present invention is not limited to this. Various plasma etching apparatuses 100 such as a capacitive coupling type and an inductive coupling type can be used.
Moreover, although the example which etches Ti layer 103 based on the pattern of the mask 104 was given in the said embodiment, it is not restricted to this, It can apply to the whole etching of Ti layer.

1; chamber (processing vessel)
2: Support table (electrode)
12; exhaust system 15; first high-frequency power source 17; temperature control medium chamber 18; gas introduction mechanism 20; shower head (electrode)
23; processing gas supply systems 24a and 24b; dipole ring magnet 100; plasma etching apparatus 101; Si substrate 102; SiO ₂ layer 103; Ti layer 104; mask layer W;

Claims (7)

In a processing container in which a vacuum can be maintained, a mask layer in which a pattern of at least a predetermined shape is formed, and a Ti layer as a layer to be etched formed under the mask layer are to be processed. ,
A first plasma treatment step of etching the Ti layer by applying a plasma of an etching gas containing a fluorine compound at a chamber internal pressure of 4 Pa or less;
A second plasma processing step of dry-cleaning the inside of the processing chamber with a cleaning gas plasma after completion of the first plasma processing step;
A cleaning gas used in the second plasma treatment step is a gas composed of only one gas selected from the group consisting of a fluorine compound, a mixed gas of a fluorine compound and a rare gas, and oxygen, In the plasma processing step, the deposit containing the Ti compound generated in the first plasma processing step is removed.   The plasma etching method according to claim 1, wherein the first plasma processing step and the second plasma processing step are alternately repeated. The plasma etching method according to claim 1, wherein the fluorine compound is NF ₃ or CF ₄ .   The plasma etching method according to claim 1 or 3, wherein the pressure in the chamber in the second plasma treatment step is 6.7 Pa or less.   A control program which operates on a computer and controls the plasma processing apparatus so that the plasma etching method according to any one of claims 1 to 4 is performed at the time of execution. A computer storage medium storing a control program that runs on a computer,
A computer storage medium characterized in that, when executed, the control program controls a plasma processing apparatus used in the plasma etching method according to any one of claims 1 to 4. A plasma source for generating plasma;
A processing container for partitioning a processing chamber for performing an etching process on an object to be processed by the plasma;
A support for placing the object to be processed in the processing container;
An exhaust means for decompressing the inside of the processing vessel;
Gas supply means for supplying gas into the processing vessel;
A control unit for controlling the plasma etching method according to any one of claims 1 to 4 to be performed;
A plasma etching apparatus comprising:

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