JP5201934B2 - Method for reducing metal contamination of substrate processing apparatus - Google Patents

Description

The present invention relates to a substrate processing apparatus that performs processing such as forming a thin film such as SiO _{2 on} an object to be processed such as a semiconductor wafer, and more particularly to a metal contamination reducing method for reducing metal contamination in the substrate processing apparatus.

In the manufacturing process of a semiconductor device, there is a film forming process for forming a thin film such as SiO ₂ on a semiconductor wafer typified by a silicon wafer. In the film forming process, a technique is used in which a plurality of semiconductor wafers are collectively formed by chemical vapor deposition (CVD) using a vertical batch heat treatment apparatus.

With the progress of miniaturization and high integration of semiconductor devices, high-quality thin films such as SiO ₂ have been demanded. As a technology capable of realizing a high-quality thin film, a source gas serving as a thin film source, for example, ALD that alternately and repeatedly forms a film at an atomic layer level or a molecular layer level while alternately supplying Si source and an oxidizing agent, or A technique for forming a SiO ₂ film using the MLD technique is described in Patent Document 1, for example.

  Patent Documents 2 to 5 describe techniques for pre-coating the inside of a processing container.

In a semiconductor device manufacturing process, there is a film forming process for forming a thin film such as SiO ₂ on a semiconductor wafer typified by a silicon wafer. In the film forming process, a technique is used in which a plurality of semiconductor wafers are collectively formed by chemical vapor deposition (CVD) using a vertical batch heat treatment apparatus.
Japanese Patent Laid-Open No. 2003-7700 Japanese Patent Laid-Open No. 9-246256 JP 2002-313740 A JP 2003-188159 A JP-A-9-171968

The demand for the quality of thin films such as SiO ₂ is increasing year by year. One of the major factors affecting the properties of thin films is metal contamination of the thin films. The source of metal contamination is metal that has fallen into the processing chamber. One of the metal contamination that flows into the processing chamber is volatilization of the metal taken into the fused quartz (natural quartz) that is a constituent material of the processing chamber. There is no problem as long as the amount of volatilization is very small and the amount of scattering into the processing chamber falls within an allowable range. However, in reality, the allowable range of the scattering amount is narrowing year by year.

  If the allowable range becomes narrower in the future, it is difficult to keep the metal, for example, copper, scattered in the processing chamber within the allowable range as it is.

  The present invention provides a method for reducing metal contamination in a substrate processing apparatus that can suppress the volatilization of metal incorporated in the constituent material of the processing chamber and can cope with the narrowing of the allowable range of the scattering amount. With the goal.

In order to solve the above-described problems, a metal reduction method for a substrate processing apparatus according to one aspect of the present invention includes a processing container, and a container inner member that is disposed in the processing container and includes a holding member that holds an object to be processed. A metal contamination reducing method for a substrate processing apparatus using natural quartz for the processing vessel , wherein a film containing chlorine is used to form a thin film on the object to be processed.
Before performing a film forming process on the object to be processed using the chlorine- containing gas, the inner wall of the processing container and the surface of the member in the container are formed using a gas not containing chlorine. Pre-coat with the silicon oxide film.

  According to the present invention, there is provided a method for reducing metal contamination in a substrate processing apparatus capable of suppressing the volatilization of metal taken into the constituent material of the processing chamber and capable of dealing with the narrowing of the allowable range of the scattering amount. it can.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  1 is a longitudinal sectional view showing an example of a film forming apparatus, FIG. 2 is a transverse sectional view of the film forming apparatus shown in FIG. 1, and FIG. 3 is a timing chart showing an example of gas supply timing of the film forming apparatus shown in FIG. It is.

  The film forming apparatus 100 includes a cylindrical processing container 1 having a ceiling with a lower end opened. The entire processing container 1 is made of, for example, quartz, and a ceiling plate 2 made of quartz is provided on the ceiling in the processing container 1 and sealed. In addition, a manifold 3 formed in a cylindrical shape from, for example, stainless steel is connected to the lower end opening of the processing container 1 via a seal member 4 such as an O-ring.

  The manifold 3 supports the lower end of the processing vessel 1, and a quartz wafer boat 5 on which a large number of, for example, 50 to 100 semiconductor wafers W can be placed in multiple stages as objects to be processed from below the manifold 3. Can be inserted into the processing container 1. The wafer boat 5 has three columns 6 (see FIG. 2), and a large number of wafers W are supported by grooves formed in the columns 6.

  The wafer boat 5 is placed on a table 8 via a quartz heat insulating cylinder 7, and the table 8 passes through a lid 9 made of, for example, stainless steel that opens and closes the lower end opening of the manifold 3. It is supported on the rotating shaft 10.

  And the magnetic fluid seal | sticker 11 is provided in the penetration part of this rotating shaft 10, for example, and the rotating shaft 10 is supported rotatably, sealing airtightly. Further, a sealing member 12 made of, for example, an O-ring is interposed between the peripheral portion of the lid portion 9 and the lower end portion of the manifold 3, thereby maintaining the sealing performance in the processing container 1.

  The rotary shaft 10 is attached to the tip of an arm 13 supported by an elevating mechanism (not shown) such as a boat elevator, for example, and moves up and down the wafer boat 5 and the lid 9 etc. integrally. 1 is inserted into and removed from the inside. The table 8 may be fixedly provided on the lid 9 side, and the wafer W may be processed without rotating the wafer boat 5.

Further, the film forming apparatus 100 includes an oxygen-containing gas supply mechanism 14a that supplies an oxygen-containing gas, for example, N ₂ O gas, into the processing container 1 as a film forming gas used for the film forming process, and silicon into the processing container 1. A silicon source gas supply mechanism 14b for supplying a source gas, for example, dichlorosilane (DCS) gas.

The film forming apparatus 100 also has a purge gas supply mechanism 16 that supplies an inert gas, for example, nitrogen (N ₂ ) gas, into the processing container 1 as a purge gas.

The oxygen-containing gas supply mechanism 14a is connected to an oxygen-containing gas supply source 17a and a gas pipe that guides the oxygen-containing gas from the gas supply source 17a. The oxygen-containing gas supply mechanism 14a penetrates the side wall of the manifold 3 inward and is bent upward. A dispersion nozzle 19 made of an extending quartz tube is provided. A plurality of gas discharge holes 19a are formed at a predetermined interval in the vertical portion of the dispersion nozzle 19, and an oxygen-containing gas, for example, substantially uniformly from each gas discharge hole 19a toward the processing container 1 in the horizontal direction. N ₂ O gas can be discharged. The gas pipe for guiding the oxygen-containing gas is provided with an on-off valve 18a and a flow rate controller 18b such as a mass flow controller, and the oxygen-containing gas is supplied to the dispersion nozzle 19 while controlling the flow rate. ing.

  The silicon source gas supply mechanism 14b is connected to a silicon-containing gas supply source 17b and a gas pipe that guides the silicon-containing gas from the gas supply source 17b. And a dispersion nozzle 24 made of a quartz tube bent in the direction and extending vertically. A plurality of gas discharge holes 24 a are also formed in the vertical portion of the dispersion nozzle 24 so that a silicon-containing gas, for example, DCS gas, can be discharged into the processing container 1 uniformly in the horizontal direction. The gas piping for guiding the silicon source gas is also provided with an on-off valve 18c and a flow rate controller 18d, and the silicon source gas is supplied to the dispersion nozzle 24 while controlling the flow rate, similarly to the oxygen-containing gas.

  The purge gas supply mechanism 16 includes a purge gas supply source 25 and a nozzle 27 that is connected to a gas pipe that guides the purge gas from the purge gas supply source 25 and that penetrates the side wall of the manifold 3.

  An on-off valve 26a and a flow rate controller 26b are also connected to the gas pipe for guiding the purge gas, and the purge gas is also supplied to the nozzle 27 while the flow rate is controlled.

  An exhaust port 37 for evacuating the inside of the processing container 1 is provided in a part of the processing container 1 opposite to the dispersion nozzles 19 and 24. The exhaust port 37 is formed in an elongated shape by scraping the side wall of the processing container 1 in the vertical direction. An exhaust port cover member 38 having a U-shaped cross section so as to cover the exhaust port 37 is attached to a portion corresponding to the exhaust port 37 of the processing container 1 by welding. The exhaust port cover member 38 extends upward along the side wall of the processing container 1, and defines a gas outlet 39 above the processing container 1. A vacuum exhaust mechanism including a vacuum pump (not shown) is connected to the gas outlet 39. A vacuum exhaust mechanism (not shown) evacuates the processing container 1.

  A cylindrical heating device 40 is provided on the outer periphery of the processing container 1. The heating device 40 is provided so as to surround the processing container 1 and heats the processing container 1 and an object to be processed, for example, a semiconductor wafer W accommodated therein.

  Control of each component of the film forming apparatus 100, for example, supply and stop of each gas by opening and closing the on-off valves 18a, 18c, and 26a, control of flow rate by the flow rate controllers 18b, 18d, and 26b, control of the heating device 40, etc. For example, it is performed by a controller 50 composed of a microprocessor (computer). Connected to the controller 50 is a user interface 51 including a keyboard for an operator to input commands for managing the film forming apparatus 100, a display for visualizing and displaying the operating status of the film forming apparatus 100, and the like. Yes.

  A storage unit 52 is connected to the controller 50. The storage unit 52 is a program for realizing various processes executed by the film forming apparatus 100 under the control of the controller 50, and for causing each component of the film forming apparatus 100 to execute processes according to the processing conditions. A program or recipe is stored. The recipe is stored in a storage medium in the storage unit 52, for example. The storage medium may be a hard disk or a semiconductor memory, or a portable medium such as a CD-ROM, DVD, or flash memory. Moreover, you may make it transmit a recipe suitably from another apparatus via a dedicated line, for example. The recipe is read from the storage unit 52 according to an instruction from the user interface 51 as necessary, and the controller 50 executes processing according to the read recipe, whereby the film forming apparatus 100 is Under the control of 50, a desired process is performed.

  The film forming process by the film forming apparatus 100 is performed as follows.

  FIG. 3 is a timing chart showing gas supply timing. In this example, a silicon oxide film is formed on the semiconductor wafer W by alternately supplying a silicon source gas and an oxygen-containing gas into the processing chamber 1.

  First, at normal temperature, for example, a wafer boat 5 on which 50 to 100 semiconductor wafers W are mounted is loaded into the processing container 1 controlled in advance to a predetermined temperature by raising the wafer boat 5 from below the processing container 1. . An example of the semiconductor wafer W has a diameter of 300 mm. Next, the lid 9 is used to close the lower end opening of the manifold 3 to make the inside of the processing container 1 a sealed space. Next, the inside of the processing container 1 is evacuated to maintain a predetermined process pressure, and the power supplied to the heating device 40 is controlled to increase the wafer temperature to maintain the process temperature, and to rotate the wafer boat 5. In this state, the film forming process is started.

As shown in FIG. 3, the film forming process at this time includes a process S1 in which silicon source gas is supplied to the processing container 1 and silicon is adsorbed on the semiconductor wafer W, and, for example, O ₃ gas is used as the oxygen-containing gas in the processing container. 1 and the step S2 of oxidizing the silicon by alternately supplying to the substrate 1 are repeated alternately. Between these processes S1 and S2, process S3 which removes residual gas from the inside of processing container 1 is carried out. The process temperature in these steps S1 to S3 is set to 100 to 400 ° C., for example. As described above, by alternately supplying the silicon source gas and the oxygen-containing gas into the processing container 1, a silicon oxide film is formed on the semiconductor wafer.

  By the way, the processing container 1 etc. are formed using fused quartz, that is, natural quartz. Natural quartz originally contains impurities. In particular, the problematic impurity is copper. Copper is one of the contaminants when manufacturing semiconductor devices. For example, if copper diffuses into the interlayer insulating film, the insulating properties of the interlayer insulating film may be impaired.

In order to prevent impurities originally contained in natural quartz from coming out of the processing vessel 1, the inner wall of the processing vessel 1 is precoated with a silicon oxide film. The inventors of the present application used dichlorosilane (DCS) gas, formed a silicon oxide film using N ₂ O gas as an oxidizing agent, and precoated the inner wall of the processing vessel 1. In this specification, a process of forming a silicon oxide film using DCS and N ₂ O gas as an oxidizing agent is referred to as a DCS-HTO process.

A silicon oxide film was accumulated 600 nm on the inner wall of the processing vessel 1 and the surface of the inner member of the vessel by the DCS-HTO process. Using this film forming apparatus, a silicon oxide film was formed on a semiconductor wafer by a DCS-HTO process at a temperature of 780 ° C. for the purpose of analyzing impurities in the film. The silicon oxide film formed on the semiconductor wafer was analyzed for the amount of copper in the film using ICP (Inductively-Coupled Plasma) emission spectrometry. However, even when a 600 nm silicon oxide film is accumulated on the inner wall of the processing vessel 1 using the DCS-HTO process, the amount of copper in the silicon oxide film formed on the semiconductor wafer is 5 × 10 ¹⁰ atoms / cm ² . , Did not decrease more than expected.

  As a cause of this, the inventors of the present invention are that the precursor DCS contains chlorine, that is, halogen having high activity, and volatilizes the copper contained in the natural quartz constituting the processing vessel 1 and the like as copper chloride. I found out. For this reason, even if the silicon oxide film is accumulated by the DCS-HTO process, a silicon oxide film containing copper chloride continues to be formed on the inner wall of the processing container 1, so that copper is scattered into the processing container 1. It's hard to reduce.

Therefore, the inventors of the present invention use a precursor that does not contain halogen, in this example, monosilane (MS: SiH ₄ ) as a precursor, form a silicon oxide film using N ₂ O gas as an oxidizing agent, and process vessel 1 The inner wall was pre-coated. In this specification, a process of forming a silicon oxide film using MS and N ₂ O gas as an oxidizing agent is referred to as an MS-HTO process. The precoat refers to a stabilization process in the processing container 1 (furnace) performed before the main film formation on the wafer. This pre-coating is performed with no wafer in the processing container 1.

In this example, the silicon oxide film is exposed to the inner wall of the processing vessel 1 and the inner member of the processing vessel 1 (wafer boat 5, support column 6, heat insulating cylinder 7, table 8, and lid 9 in the processing vessel 1 by the MS-HTO process. 600 nm is accumulated on the surface and the like. Using this film forming apparatus, for the purpose of analyzing impurities in the film, a silicon oxide film is formed on a semiconductor wafer by a DCS-HTO process at a temperature of 780 ° C. as described above, and the semiconductor wafer is then formed using ICP emission spectrometry. The amount of copper in the upper silicon oxide film was analyzed. In this case, the amount of copper in the silicon oxide film formed on the semiconductor wafer decreased to 3 × 10 ¹⁰ atoms / cm ² with a cumulative 600 nm. This is shown in FIG. 4A.

As shown in FIG. 4A, according to the MS-HTO precoat (600 nm accumulation), copper could be reduced to the order of about 3 × 10 ¹⁰ atoms / cm ² from the silicon oxide film on the semiconductor wafer. Incidentally, according to the DCS-HTO precoat (600 nm accumulation), as shown by a circle in FIG. 4A, copper is only up to about 5 × 10 ¹⁰ atoms / cm ² order. FIG. 4B shows a schematic cross section of the film forming apparatus used for the evaluation.

  As shown in FIG. 4B, the film forming apparatus used for the evaluation is a vertical batch type film forming apparatus, in which an MS-HTO precoat is applied to the inner wall of the processing container 1 or the container inner member. .

  Further, as shown in FIG. 4B, the evaluation of the amount of copper in the film includes the uppermost one (top wafer) and the lowermost one (bottom wafer) among the semiconductor wafers W held on the wafer boat 5. It carried out in.

In this example, as shown in FIG. 4A, the top wafer has less copper in the film than the bottom wafer. This is because in a vertical batch type film forming apparatus, the temperature of the lower part of the processing container 1 is difficult to be pre-coated with MS-HTO, for example, a heat insulating cylinder (insulating material) 7 which is an inner member of the container. There is a low part, and it is presumed that MS-HTO was not deposited thick in the low temperature part. For example, as shown by an arrow A in FIG. 4A, when the cumulative film thickness is 200 nm, the bottom wafer contains about 8 × 10 ¹⁰ atoms / cm ² of copper, and the cumulative film thickness and the copper in the film It is far from the expected curve showing the relationship. This is presumed to be because MS-HTO was not deposited thick in the low temperature part.

However, as shown in FIG. 4A, when the cumulative film thickness is 400 nm or more, the amount of copper is reduced to the order of about 3 × 10 ¹⁰ atoms / cm ² , as in the case of the top wafer. For example, if MS-HTO is deposited to a thickness of 400 nm or more, there will be no problem even if there are a high temperature portion and a low temperature portion inside the processing vessel 1.

  In addition, if the lower part of the container inner member is brought to the upper part and precoated during the MS-HTO pre-coating, a sufficiently thick MS-HTO film can be formed also on the lower part of the container inner member. In this way, it is possible to expect the effect of reducing the copper in the film to the same level as the top wafer even with the bottom wafer.

  As described above, according to the present embodiment, by using the MS-HTO process, the silicon oxide film is formed on the inner wall of the processing container 1 and the surface of the container inner member with a gas not containing halogen, The amount of copper can be reduced from the thin film formed on the semiconductor wafer.

  The reason for this is that the oxide film deposition rate is faster than that of the DCS-HTO process, and the inner wall of the processing vessel 1 and the surface of the inner member of the vessel are removed by using an MS-HTO process that does not contain halogen, for example, chlorine. Pre-coat. Thereby, copper which is an impurity is applied as copper oxide in the silicon oxide film formed by the MS-HTO process. Copper oxide has a slower diffusion rate than copper chloride. That is, a stable copper oxide is formed between the natural quartz surface with a large amount of impurities and the silicon oxide film, and further thickly coated with a silicon oxide film with a small amount of impurities thereon.

  According to the present embodiment, the processing vessel 1 has a configuration in which copper oxide is formed on natural quartz and the copper oxide is further covered with a silicon oxide film (synthetic quartz) formed using a precursor not containing halogen. The inner wall and the surface of the container inner member, that is, the gas contact surface can be covered with, for example, a silicon oxide film (synthetic quartz) not containing copper chloride or the like.

  Therefore, it is possible to provide a film forming apparatus capable of suppressing the volatilization of the constituent material of the processing chamber, for example, the metal taken in the natural quartz, and dealing with the narrowing of the allowable range of the scattering amount. FIG. 5 shows an example of a film forming apparatus to which this embodiment is applied.

  As shown in FIG. 5, a silicon oxide film 50 formed using the MS-HTO process is formed on the inner wall of the processing container 1 and the surface of the container inner member.

  Although the present invention has been described according to one embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made, and the above-described one embodiment is not the only embodiment.

  For example, in the above-described embodiment, the present invention is applied to a batch-type film forming apparatus in which a plurality of semiconductor wafers are mounted and collectively formed. However, the present invention is not limited to this. The present invention can also be applied to a single-wafer type film forming apparatus for forming a film.

Moreover, in the said embodiment, although the film-forming apparatus which forms the thin film containing oxygen with respect to a to-be-processed object, for example, a silicon oxide film, was illustrated, for example, the thin film containing nitrogen with respect to a to-be-processed object, For example, a film forming apparatus for forming a silicon nitride film may be used. For example, when a silicon nitride film is formed, DCS may be used as a deposition gas (precursor) and NH ₃ may be used as a gas containing nitrogen. It is also possible to oxynitride the thin film. In this case, an oxynitride film such as a silicon oxynitride film can be formed on the object to be processed. The substance to be oxidized, nitrided, or oxynitrided is not limited to silicon, and may be a metal material used for a semiconductor device, such as hafnium or zirconium.

  Moreover, in the said embodiment, although scattering of the copper from natural quartz was suppressed as a contaminant, the said embodiment uses the precursor which does not contain a halogen, and the inner wall and container inner member of the processing container 1 are used. Therefore, scattering of contaminants other than copper, such as aluminum contained in natural quartz, can also be suppressed.

  Furthermore, the above embodiment can be applied not only to a film forming apparatus but also to an oxidation process in which films cannot be accumulated, that is, a thermal oxidation apparatus.

  Further, the object to be processed is not limited to a semiconductor wafer, and the present invention can also be applied to other substrates such as an LCD glass substrate.

A longitudinal sectional view showing an example of a film forming apparatus used in the practice of the present invention Cross-sectional view showing an example of a film forming apparatus used in the practice of the present invention Timing chart showing gas supply timing in film formation The figure which shows the metal contamination reduction method which concerns on one Embodiment of this invention Sectional drawing which expands and shows the vicinity of a processing container

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Processing container, 2 ... Ceiling board, 3 ... Manifold, 5 ... Wafer boat, 6 ... Support | pillar, 7 ... Thermal insulation cylinder, 8 ... Table, 9 ... Lid part, 14a ... Oxygen containing gas supply mechanism, 14b ... Silicon source gas Supply mechanism, 16 ... purge gas supply mechanism, W ... semiconductor wafer (object to be processed)

Claims (6)

A processing container and a container inner member that includes a holding member that is disposed in the processing container and holds the object to be processed, and performs a film forming process on the object to be processed using a gas containing chlorine . A method for reducing metal contamination in a substrate processing apparatus using natural quartz in the processing container ,
Before performing a film forming process on the object to be processed using the chlorine- containing gas, the inner wall of the processing container and the surface of the member in the container are formed using a gas not containing chlorine. A method for reducing metal contamination in a substrate processing apparatus, comprising pre-coating with a silicon oxide film.   2. The method of reducing metal contamination in a substrate processing apparatus according to claim 1, wherein the thickness of the silicon oxide film is 400 nm or more. The substrate processing apparatus according to claim 2, wherein the copper in the thin film formed on the object to be processed is in the order of 1 × 10 ¹⁰ atoms / cm ^{2 to} 3 × 10 ¹⁰ atoms / cm ^2. To reduce metal contamination. The method for reducing metal contamination in a substrate processing apparatus according to any one of claims 1 to 3, wherein the chlorine-free gas is monosilane. The substrate processing apparatus is a film forming apparatus for forming a thin film containing oxygen or nitrogen on an object to be processed, wherein the chlorine- containing gas and the oxygen are formed during the film forming process on the object to be processed. 5. The method for reducing metal contamination in a substrate processing apparatus according to claim 1 , wherein a thin film containing oxygen or nitrogen is formed by supplying a gas containing nitrogen or a gas containing nitrogen. . The pre-coating is performed using the chlorine- free gas and oxygen-containing gas,
Silicon oxide formed by using copper contained in natural quartz used in the substrate processing apparatus as copper oxide, and using the gas containing no chlorine and the gas containing oxygen on the copper oxide. 6. The method for reducing metal contamination of a substrate processing apparatus according to claim 1, wherein the metal contamination is covered with a film.

Images