JP4351980B2 - Plasma processing method - Google Patents

Description

  The present invention relates to a plasma processing technique, and more particularly to a plasma processing technique performed using a processing chamber in which yttrium oxide is formed on an inner wall.

   In general, a processing chamber wall of a plasma processing apparatus is scraped or a film adheres as the plasma processing is repeated by sputtering with ions in plasma, etching with chemically active species, or deposition of reaction products. If the inner wall is sharpened, the plasma processing characteristics will be affected, so that maintenance work such as replacement of inner wall parts is required. Further, when a film adheres to the inner wall, if the amount of adhesion increases, the plasma processing characteristics may be affected, and the film may eventually peel off and fall on the surface of the substrate to be processed, which may impair the plasma processing quality. For this reason, maintenance work such as removing deposits accumulated on the inner wall is required.

  Such maintenance work lowers the operating rate of the plasma processing apparatus and reduces productivity. Also, replacement parts are often expensive in general, and this is one of the main factors that increase the processing cost of plasma processing. For this reason, there are demands for materials, processing methods, and the like with less shaving of the inner wall and less film deposition.

  Under these circumstances, yttrium oxide has been attracting attention as a material that is less likely to be scraped by ion bombardment and chemically active species, and is being applied to plasma processing apparatuses from the viewpoint of improving processing efficiency, such as reducing maintenance frequency.

  As a conventional plasma processing apparatus, an electromagnetic wave is input into a processing chamber through a quartz window, plasma is generated in the processing chamber, and a high-frequency bias power is applied to a substrate electrode on which a substrate to be processed is placed. An apparatus that performs an etching process by drawing ions therein into a substrate to be processed is known (see, for example, Patent Document 1).

In this apparatus, the high frequency bias current applied to the substrate electrode flows from the substrate to be processed to the processing chamber wall surface through plasma. The high-frequency voltage applied to the substrate electrode is applied mainly to a region called a sheath formed at the interface between the substrate to be processed and the plasma. At this time, a DC voltage is generated in the sheath due to the non-linearity of the sheath, and as a result, a high-frequency bias voltage and a DC voltage are applied to the sheath. Due to the voltage applied to the sheath, ions in the plasma are accelerated toward the substrate to be processed, and the plasma processing quality such as etching is improved. However, since a sheath is also formed on the processing chamber wall surface, similarly, accelerated ions collide with the processing chamber wall surface to etch the processing chamber wall surface.
JP 2003-163204 A

  As described above, the processing chamber wall surface may be scraped by sputtering due to ion bombardment in plasma or etching by chemically active species in plasma. When the wall surface of the processing chamber is scraped, if the scraped material is not gasified, it is deposited on the surface of the processing chamber including the surface of the substrate to be processed. These deposits not only lower the quality of the plasma processing, but also change the state of the inner surface of the processing chamber, thereby changing the plasma processing characteristics and reducing the life of the parts constituting the processing chamber wall surface.

  By the way, yttrium oxide is a material that is relatively chemically stable and resistant to sputtering impact. However, it reacts with halogen atoms contained in the main processing gas in an etching apparatus or the like to produce yttrium chloride, yttrium fluoride, yttrium bromide, or the like on its surface. Although the mechanism by which yttrium oxide is removed by plasma containing halogen atoms is not necessarily clear, the present inventors presume as follows.

(1) A halogen atom and yttrium oxide react to form a yttrium halide on the surface.

(2) Yttrium halide is shaved by sputtering action of ions in plasma.

  When the produced yttrium halide adheres to the inner wall of the processing chamber, these are chemically stable, and there is a problem in that there is no simple method for removal.

  The present invention has been made in view of such problems, and reduces the wear of the member coated with yttrium oxide on the inner surface of the plasma processing chamber, thereby enabling stable plasma processing over a long period of time.

  In order to solve the above problems, the present invention employs the following means.

A vacuum processing chamber in which yttrium oxide is formed in a portion of the inner wall that comes into contact with plasma, a gas supply means for supplying a processing gas containing halogen into the processing chamber, and an antenna, which supplies high-frequency power from the first high-frequency power source to the processing chamber And a plasma generating means for generating plasma in the processing chamber, a substrate electrode disposed in the processing chamber on which a sample is placed, and a second high-frequency power source for supplying a high-frequency bias voltage to the substrate electrode. Each time the processing of one sample is completed, plasma treatment is performed on the surface of the processing chamber in a gas containing chlorine, not containing fluorine, and containing silicon atoms, boron atoms, or carbon atoms, and then oxygen-containing gas is put into the processing chamber. The plasma processing is performed on the inside of the processing chamber.

  Since the present invention has the above-described configuration, it is possible to reduce the wear of the member coated with yttrium oxide on the inner surface of the plasma processing chamber, and to enable stable plasma processing over a long period of time.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings. FIG. 1 is a view for explaining an etching apparatus according to the first embodiment of the present invention. UHF power output from a UHF power source (first high frequency power source) 101 having a frequency of 450 MHz is transmitted to the on-disk antenna 104 via the coaxial line 102 and the automatic matching machine 103. The UHF power radiated from the on-disk antenna 104 is radiated into the processing chamber 107 through the quartz window 105 and the shower plate 106. A substrate electrode 109 for placing the substrate to be processed 108 is provided in the processing chamber 107. A bias power source (second high frequency power source) 111 is connected to the substrate electrode 109 via a matching unit 110, and a bias can be applied to the substrate 108 to be processed.

  A member 112 covered with an yttrium oxide film is provided on the inner surface of the processing chamber 107. A processing gas supply means (not shown) supplies a gas containing an element such as chlorine, fluorine, bromine or the like to a minute gap provided between the quartz window 105 and the shower plate 106, and a plurality of the gas provided in the shower plate 106. Gas is supplied into the processing chamber 107 through a fine gas supply hole in the form of a shower. Further, a vacuum exhaust system (not shown) is connected to the processing chamber 107, and the pressure in the processing chamber can be maintained at a predetermined pressure suitable for the etching process together with the flow rate of the gas supplied from the gas supply system.

  The diameter of the fine gas supply hole provided in the shower plate 106 was 0.5 mm. However, from the standpoint of preventing discharge in the gas supply hole, it is desirable that the diameter of the gas supply hole is smaller. A static magnetic field generator 113 is provided around the processing chamber 107, and can generate a static magnetic field in the processing chamber. This static magnetic field can control the diffusion of plasma generated in the processing chamber 107. Further, when the electron cyclotron motion coincides with the cycle of the UHF power source to be input, an ECR (electron cyclotron resonance) phenomenon occurs in which the UHF power is absorbed into the plasma in a resonant manner, and the plasma can be generated efficiently. In the case of the present embodiment having a frequency of 450 MHz, it is known that the ECR phenomenon occurs at 0.0166 Tesla. It is also possible to control the plasma generation region by controlling the static magnetic field distribution and controlling the location of the magnetic field of 0.0166 Tesla, which is the ECR condition. Further, by causing the ECR phenomenon, plasma can be stably generated and maintained even at a low pressure of, for example, 0.1 Pa or less, which is difficult to generate with the conventional plasma generation method. The controller 114 controls the entire apparatus such as the first and second high-frequency power sources 101 and 111, the static magnetic field generator 113, the processing gas supply unit, and the sample loading / unloading unit (not shown).

  A bias voltage is applied to the substrate to be processed by the bias power supply 111 as described above. A frequency of 400 kHz was used as the frequency of the bias power source. The electric power supplied from the bias power source is consumed mainly in the sheath region formed at the interface of the plasma generated in the processing target substrate 108 and the processing chamber 107, but a part thereof is other sheath region, for example, yttrium oxide film. It is consumed in the sheath region formed at the interface between the coated member 112 and the plasma. Ions in the plasma are accelerated by the bias power applied to the sheath region, collide with the surface of the member 112, for example, and scrape the surface by sputtering. The mechanism by which the surface of yttrium oxide is scraped by being exposed to plasma is presumed as described above.

  The present inventors conducted long-term stability experiments of etching processing using a gas containing chlorine, fluorine, and bromine using the etching apparatus shown in this embodiment. As a result, when the etching process was repeated for a long time, a slight amount of deposit was detected on the inside of the processing chamber, and as a result of elemental analysis, yttria (yttrium oxide) and fluorine were detected simultaneously. From this, the inventor presumes that the yttrium element is deposited as yttrium fluoride in the deposit.

  Examples of the yttrium halide include yttrium fluoride, yttrium chloride, and yttrium bromide. Among these, yttrium chloride is considered to be relatively easily sputtered. Also, yttrium chloride easily reacts with fluorine to become yttrium fluoride, and it is assumed that yttrium chloride reacts with yttrium fluoride when the sputtered yttrium chloride is exposed to a plasma containing fluorine atoms thereafter. To do. As a result, it is estimated that yttrium fluoride was formed in the deposit as described above.

  As a result of the experiment, deposits containing yttria were detected in the processing chamber. In order to reduce the quality of plasma processing when deposits in the processing chamber fluctuate in processing characteristics or peel off and adhere to the substrate to be processed, a method for reducing these deposits was examined. As a result, it was found that deposits can be reduced by performing the treatment according to the following procedure.

(1) The substrate to be processed is etched with a gas containing halogen such as fluorine, chlorine or bromine.

(2) A silicon substrate is introduced onto the substrate electrode, plasma is generated in a gas system containing chlorine and not containing fluorine, and etching is performed. For example, only chlorine gas is introduced into the processing chamber to generate plasma. At this time, it is desirable to apply a bias power to the substrate, etch the silicon substrate at a high speed, and release silicon atoms into the processing chamber.

(3) Oxygen-containing plasma is generated in the processing chamber, and the inside of the processing chamber is plasma-processed.

  In the process of etching the substrate to be processed (1), yttrium halides such as yttrium fluoride and yttrium chloride are formed on the surface of the yttrium oxide inside the processing chamber. In the process (2), silicon atoms released from the silicon substrate have an effect of extracting fluorine from the yttrium fluoride formed in the process (1) and discharging it as silicon fluoride. Chlorine is simultaneously supplied from the plasma, yttrium is salified, and reacts with yttrium chloride.

  As a method of supplying silicon for extracting fluorine from yttrium fluoride, it may be supplied as a gas such as silicon chloride in addition to supplying from a silicon substrate. Further, although silicon is used as an element having an action of extracting fluorine, carbon atoms or boron atoms may be supplied. Similarly, when supplying these atoms to the processing chamber, a gas such as boron trichloride or carbon tetrachloride may be supplied, or a solid such as silicon carbide is supplied as a substrate to be processed, and this is etched. Also good.

In the process (3), yttrium chloride is oxidized and reacted with yttrium oxide.

In the above process (2), for example,
4YF ₃ + 3SiCl ₄ → 4YCl ₃ + 3SiF ₄ ↑
4YF ₃ + 3CCl ₄ → 4YCl ₃ + 3CF ₄ ↑
YF ₃ + BCl ₃ → YCl ₃ + BF ₃ ↑
YF ₃ + 2BCl ₃ → YCl ₃ + BCl ₂ F + BClF ₂ ↑
It is thought that such a reaction is taking place.

In the process (3) above,
4YCl ₃ + 3O ₂ → 2Y ₂ O ₃ + 6Cl ₂
It is thought that this reaction is occurring.

  The treatments (2) and (3) are preferably performed every time the substrate to be treated of (1) is etched from the viewpoint of suppressing the yttrium oxide scraping. The process itself takes time, leading to a reduction in the productivity of the etching process. Therefore, from the viewpoint of productivity, the above (2) and (3) may be carried out every time several substrates to be processed are processed. In addition, when the gas supply method is used as a method for supplying atoms for extracting fluorine atoms when the process (2) is performed, it is not necessary to introduce the substrate. It may be carried out using the time in the middle.

  FIG. 2 is a diagram for explaining a second embodiment of the present invention. The main part different from the above-described embodiment is the configuration of the etching apparatus. A part of the description of the common parts is omitted. The high frequency power output from the first high frequency power supply 101 is connected to the automatic matching machine 103 via the coaxial line 102. The frequency of the first high frequency power source was 60 MHz. This high-frequency power is introduced into the antenna 204 through the automatic matching machine 103 and further into the processing chamber 107. A gas supply means (not shown) and a vacuum exhaust means (not shown) are connected to the processing chamber 107, and the inside is maintained at a pressure and gas atmosphere suitable for the etching process. The inner surface of the processing chamber 107 is covered with a member 112 covered with yttrium oxide. Instead of using the member 112, the inner surface of the processing chamber 107 may be directly coated with yttrium oxide by a method such as thermal spraying.

  A substrate electrode 109 for installing a substrate to be processed 108 is provided inside the processing chamber 107, and a second high-frequency power source 111 is connected to the substrate electrode 109 via an automatic matching machine 110. The high frequency of the second high frequency power supply 111 is applied to the substrate to be processed 108, and ions in the plasma generated by the power supplied from the first high frequency power supply are drawn into the processing chamber to the substrate to be processed, thereby increasing the etching process speed. We are trying to improve quality. The frequency of the second high frequency power source was 2 MHz.

  As a material of the antenna 204, at least a surface that comes into contact with plasma is mainly silicon, carbon, or silicon carbide. In addition, a gas reservoir 205 and a plurality of gas supply holes 206 for supplying a processing gas to the processing chamber are provided in the antenna 204, and the processing gas can be supplied into the processing chamber 107 in a shower shape.

  When the substrate to be processed is etched using halogen gas as in the first embodiment, the surface of the member 112 covered with yttrium oxide is halogenated. As the main mechanism for scraping the surface of the member 112, it is considered that ions in the plasma collide with the halogenated surface and are shaved by the sputtering action as in the above example.

  Among the yttrium halides, yttrium fluoride, as in the first embodiment, contains atoms that bind relatively strongly to fluorine such as silicon, boron, and carbon having the action of extracting fluorine in the plasma generated in the processing chamber. While being released and extracted from the yttrium fluoride on the surface of the member 112, chlorine atoms are supplied into the plasma, and chlorine is supplied to the yttrium from which fluorine has been extracted to stabilize it as yttrium chloride.

  Further, the surface of the member 112 is treated with a plasma containing a gas containing oxygen and not containing a halogen element so that yttrium chloride is reacted (converted) with yttrium oxide. As a method of emitting atoms, which are relatively strongly bonded to fluorine such as silicon, boron, and carbon, into the plasma, silicon or carbon or silicon carbide on the surface of the antenna 204 is directly brought into contact with the plasma, and by sputtering action of ions in the plasma. These atoms can be released.

  The electric potential of the antenna 204 may be galvanically isolated. In that case, the surface of the antenna 204 is DC-biased by the non-linearity of the plasma sheath, and ions in the plasma are accelerated and collide with the surface of the antenna 204. In this case, the surface of the antenna 204 is sputtered by ion collision, and atoms on the surface of the antenna 204 can be efficiently emitted into the plasma.

  In addition, as a method of supplying a gas containing chlorine, not containing fluorine, and containing silicon atoms, boron atoms, or carbon atoms into the processing chamber, (1) a method of supplying via a gas supply means, (2) silicon A method in which a bias power is applied to a substrate to be processed having atoms or carbon atoms exposed on the surface, and a substance containing silicon atoms or carbon atoms is emitted from the substrate to be processed into the processing chamber; Has been described with respect to a method in which silicon, carbon, or silicon carbide is used and a substance containing silicon atoms or carbon atoms is released from the surface into the processing chamber, but the gas may be supplied in combination.

  As described above, according to the embodiment of the present invention, the consumption of the processing chamber wall surface that comes into contact with plasma is suppressed, and the adhesion of the product to other surfaces of the processing chamber due to the scraping of the processing chamber wall surface is suppressed. , Plasma processing quality can be improved. In addition, maintenance labor can be reduced.

It is a figure explaining the etching apparatus concerning a 1st embodiment. It is a figure explaining 2nd Embodiment.

Explanation of symbols

101 First high frequency power source 102 Coaxial line 103, 110 Automatic matching machine 104 Antenna 105 Quartz window 106 Shower plate 107 Processing chamber 108 Substrate to be processed (sample)
109 Substrate electrode 111 Second high-frequency power source 112 Member coated with yttrium oxide film 113 Static magnetic field generator 114 Controller 205 Gas reservoir 206 Gas supply hole

Claims (10)

A vacuum processing chamber in which yttrium oxide is formed on the inner wall in contact with the plasma;
Gas supply means for supplying a processing gas containing halogen into the processing chamber;
A plasma generating means for generating plasma in the processing chamber by supplying high-frequency power from the first high-frequency power source to the processing chamber by including an antenna;
A substrate electrode placed in the processing chamber and on which a sample is placed;
A second high frequency power supply for supplying a high frequency bias voltage to the substrate electrode;
Each time one or more samples are processed, plasma treatment is performed on the inside of the processing chamber in a gas containing chlorine, not containing fluorine, and containing silicon atoms, boron atoms, or carbon atoms, and then containing oxygen. Is supplied to the processing chamber, and the plasma processing is performed on the inner surface of the processing chamber. The plasma processing method according to claim 1,
A plasma processing method, wherein a surface of the antenna that comes into contact with plasma is made of silicon, carbon, or silicon carbide. The plasma processing method according to claim 1,
At the end of processing of one or more samples, plasma treatment applied to the inside of the processing chamber in a gas containing chlorine, not containing fluorine, and containing silicon atoms, boron atoms, or carbon atoms is performed using silicon or silicon carbide. A plasma processing method, which is an etching process using a substrate to be processed as a substrate to be processed. The plasma processing method according to claim 1,
A plasma treatment method, wherein a gas containing chlorine, not containing fluorine, and containing silicon atoms, boron atoms, or carbon atoms is supplied from the gas supply means. The plasma processing method according to claim 1,
A plasma processing method characterized by spraying yttrium oxide on a portion of a vacuum processing chamber wall that comes into contact with plasma. A vacuum processing chamber in which yttrium oxide is formed on the inner wall in contact with the plasma;
Gas supply means for supplying a processing gas containing halogen into the processing chamber;
A plasma generating means for generating plasma in the processing chamber by supplying high-frequency power from the first high-frequency power source to the processing chamber by including an antenna;
A substrate electrode placed in the processing chamber and on which a sample is placed;
A second high frequency power supply for supplying a high frequency bias voltage to the substrate electrode;
A control device for controlling the entire device is provided,
The control device includes a plasma treatment of a treatment chamber surface in a gas containing chlorine, not containing fluorine, and containing silicon atoms, boron atoms, or carbon atoms after etching the sample, and a treatment chamber with a gas containing oxygen. A plasma processing apparatus characterized by sequentially performing surface plasma processing. The plasma processing apparatus according to claim 6, wherein
A plasma processing apparatus, wherein a surface of the antenna that comes into contact with plasma is made of silicon, carbon, or silicon carbide. The plasma processing apparatus according to claim 6, wherein
The plasma treatment applied to the inside of the processing chamber in a gas containing chlorine, fluorine, and silicon atoms or boron atoms is an etching process using a substrate containing silicon or silicon carbide as a substrate to be processed. Plasma processing equipment. The plasma processing apparatus according to claim 6, wherein
A plasma processing apparatus, wherein a gas containing chlorine, not containing fluorine, and containing silicon atoms, boron atoms, or carbon atoms is supplied from the gas supply means. The plasma processing apparatus according to claim 6, wherein
A plasma processing apparatus characterized in that yttrium oxide is thermally sprayed on a portion of the vacuum processing chamber wall that comes into contact with plasma.

Images