JP4325473B2 - Cleaning method for heat treatment apparatus - Google Patents

Description

  The present invention relates to a cleaning method for a heat treatment apparatus for forming a film on an object to be processed such as a semiconductor wafer.

  Generally, in order to manufacture a semiconductor integrated circuit, various processes such as film formation and etching are performed on a semiconductor wafer. For example, in a CVD apparatus that forms a film on the surface of a large number of wafers at once, semiconductor wafers are placed on a quartz wafer boat at an equal pitch, for example, and the wafer surface is heated to a predetermined temperature under reduced pressure. A process gas for film formation is supplied to the substrate, and a decomposition product or a reaction product of this gas is deposited on the wafer.

When film formation is performed on the wafer surface in this way, in addition to the wafer surface where film formation is required, an unnecessary film is also formed on an unintended part such as a wafer boat or the inner surface of a processing vessel. Will stick. Since the adhesion film in such unnecessary portions floats as particles and causes defects in the semiconductor integrated circuit, the vacuum processing apparatus is used regularly or irregularly to remove this unnecessary adhesion film. A cleaning process is performed.
In addition to the above-described batch type hot wall type LP-CVD (Chemical Vapor Deposition) apparatus, it is necessary to perform the cleaning process in this way, as well as a single wafer type film forming apparatus for processing wafers one by one. The same applies to.

Conventionally, in a hot wall type LP-CVD apparatus, regardless of whether it is a horizontal type or a vertical type, in a periodic cleaning process, a wet using a chemical solution is used to remove an unnecessary film adhering to an inner wall of a processing container. Although it was common to perform the cleaning method, recently cleaning can be performed in-situ with the LP-CVD apparatus assembled without disassembling the LP-CVD apparatus. The dry cleaning method used is performed. As this dry cleaning method, for example, a cleaning method using ClF ₃ gas as an etching gas has been proposed (Patent Document 1, Patent Document 2, and Patent Document 3). In this cleaning method, a gas containing, for example, ClF ₃ as a cleaning gas is introduced into the processing container, and unnecessary films attached to the wafer boat, the inner surface of the processing container, and the like are removed with the cleaning gas. In this case, for example, HF gas is used as the cleaning gas in correspondence with the type of unnecessary film to be removed.

JP-A-3-31479 Japanese Patent Laid-Open No. 4-155825 JP-A-6-151396

  By the way, an important point in the above-described cleaning process is how efficiently an unnecessary film can be scraped and removed without damaging components in a heat treatment apparatus such as a processing vessel or a wafer boat. . In this case, the higher the selectivity between the material constituting the processing container and the film type to be removed by etching, the better the etching gas. That is, as the etching gas, a gas that reacts easily with the film type to be removed by etching and can be removed efficiently, and that does not easily react with constituent materials such as processing containers is suitable. .

However, in the case where the constituent material of the processing vessel or wafer boat is similar to the unnecessary film to be removed by etching, or the same kind of material, the above-mentioned selectivity cannot be obtained sufficiently. It becomes easy to do damage by. As such an example, in a heat treatment apparatus in which a processing vessel or a wafer boat is formed of quartz, for example, a silicon oxide film (SiO ₂ ) is deposited and formed on the surface of a semiconductor wafer using TEOS (tetraethylorthosilicate). There is a case. In this case, the constituent material of the processing container and the unnecessary film adhering to this surface are different in molecular density, but the main constituent material is SiO ₂ .

In such a heat treatment apparatus, conventionally, HF gas or the like has been used alone or together with an inert gas as a carrier gas as a cleaning gas, but this HF gas has an etching rate (cleaning against SiO ₂ by TEOS). (It is synonymous with rate) is not sufficiently large, and there is a problem that it takes a long time for the cleaning process. In addition, since the etching rate is not sufficiently large, the end point of the cleaning process calculated by the calculation may deviate more than the end point of the actual cleaning process in which the unnecessary film is completely removed. The overetching process results in damage to structures such as a processing vessel, a wafer boat, and a heat insulating cylinder, and there is a problem that the lifetime of these components is shortened.

The present invention has been devised to pay attention to the above problems and to effectively solve them. An object of the present invention is to perform a cleaning process quickly by efficiently and quickly removing a silicon oxide film by TEOS, which is an unnecessary film attached to a structure in a heat treatment apparatus, at a high etching rate. An object of the present invention is to provide a cleaning method for a heat treatment apparatus capable of improving throughput and suppressing damage to a structure.
In addition, an object of the present invention is to remove an arsenic glass film by TEOS, which is an unnecessary film attached to a structure in a heat treatment apparatus, efficiently and quickly at a high etching rate, thereby improving throughput and improving the structure. Another object of the present invention is to provide a cleaning method for a heat treatment apparatus that can suppress the damage.

  Another object of the present invention is to remove the boron glass film by TEOS, which is an unnecessary film attached to the structure in the heat treatment apparatus, efficiently and quickly at a high etching rate, thereby improving the throughput and improving the structure. Another object of the present invention is to provide a cleaning method for a heat treatment apparatus that can suppress the damage.

The invention according to claim 1 is an arsenic glass film or TEOS which is a film containing impurities using a SiO ₂ film or a TEOS film using TEOS with respect to an object to be processed in a quartz processing vessel which can be evacuated. a method of cleaning a film forming processes performed heat treatment apparatus of the boron silicate glass film is a film containing an impurity using supplies a HF gas and NH ₃ gas into the process container, the temperature of the processing chamber A cleaning method for a heat treatment apparatus, comprising: a cleaning step in which a pressure is set in a range of 100 to 300 ° C. and a pressure in the processing container is set to 53200 Pa (400 Torr) or more.
In this way, by using a mixed gas of HF gas and NH ₃ gas as the cleaning gas, an unnecessary adhesion film of the silicon oxide film formed by TEOS is suppressed while suppressing damage to the structure in the heat treatment apparatus. It is possible to perform the cleaning process quickly by removing it quickly and efficiently.
Further, an AsSG film (arsenic glass film) formed by TEOS is unnecessary while a mixed gas of HF gas and NH ₃ gas acts as a cleaning gas and suppresses damage given to the structure in the heat treatment apparatus. It is possible to remove the adhered film quickly and efficiently.
Further, the mixed gas of HF gas and NH ₃ gas acts as a cleaning gas, suppressing damage given to the structure in the heat treatment apparatus, and eliminating the need for the BSG film (boron glass film) formed by TEOS. It is possible to remove the adhered film quickly and efficiently.

In this case, for example, as defined in claim 2, in the cleaning step, the supply amount of HF gas is equal to or more than the supply amount of NH ₃ gas.

According to the cleaning method of the heat treatment apparatus of the present invention, the following excellent effects can be exhibited.
By using a mixed gas of HF gas and NH ₃ gas as the cleaning gas, damage to the structure in the heat treatment apparatus is suppressed, and the silicon oxide film including impurities formed by TEOS is unnecessary. The cleaning process can be performed quickly by removing the adhered film quickly and efficiently.

Hereinafter, an embodiment of a cleaning method for a heat treatment apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an example of a heat treatment apparatus in which a cleaning method according to the present invention is performed. The heat treatment apparatus 2 includes a vertical processing container 8 having a predetermined length of a double tube structure made of quartz made of an inner cylinder 4 and an outer cylinder 6. The processing space S in the inner cylinder 4 accommodates a quartz wafer boat 10 as a supporting means for holding the object to be processed. The wafer boat 10 includes a semiconductor wafer W as the object to be processed. Are held in multiple stages at a predetermined pitch. This pitch may be constant or may vary depending on the wafer position.

  A cap 12 is provided to open and close the lower portion of the processing container 8, and a rotating shaft 16 is provided through the cap 12 via a magnetic fluid seal 14. A rotary table 18 is provided at the upper end of the rotary shaft 16, a quartz heat insulating cylinder 20 is provided on the table 18, and the wafer boat 10 is placed on the heat insulating cylinder 20. The rotating shaft 16 is attached to an arm 24 of a boat elevator 22 that can be moved up and down, and can be moved up and down integrally with the cap 12, the wafer boat 10 and the like. It can be inserted and removed from below. The wafer boat 10 may be fixed without rotating.

For example, a stainless steel manifold 26 is joined to the lower end opening of the processing container 8, and a film forming gas supply system 28 for supplying a film forming gas is provided in the manifold 26. Specifically, the film-forming gas supply system 28 has a film-forming gas nozzle 30 provided through the manifold 26, and the nozzle 30 has a flow control such as a mass flow controller in the middle. A gas supply path 34 is connected via a vessel 32. A TEOS source 36 for storing TEOS as a film forming gas is connected to the gas supply path 34, and the TEOS gas can be supplied while controlling the flow rate during the film forming process. Further, the manifold 26 is individually provided with an HF gas supply system 38 and an NH ₃ gas supply system 40 for introducing HF gas and NH ₃ gas whose flow rates are controlled as cleaning gases into the processing vessel 8. ing.

Specifically, first, the HF gas supply system 38 has an HF gas nozzle 42 provided through the manifold 26, and a flow rate controller 44 such as a mass flow controller is provided in the nozzle 42 on the way. Is connected to a gas supply path 46. An HF gas source 48 is connected to the gas supply path 46.
Similarly, the NH ₃ gas supply system 40 has an NH ₃ gas nozzle 50 provided through the manifold 26. The nozzle 50 is provided with a flow rate controller 52 such as a mass flow controller. The interposed gas supply path 54 is connected. An NH ₃ gas source 56 is connected to the gas supply path 54.

Accordingly, the gases supplied from the nozzles 30, 42, 50 rise up the wafer storage area, which is the processing space S in the inner cylinder 4, and turn downward at the ceiling, and the inner cylinder 4 and the outer cylinder It flows down in the gap with 6 and is discharged. An exhaust port 58 is provided on the bottom side wall of the outer cylinder 6, and a vacuum exhaust system 64 is connected to the exhaust port 58 via a vacuum pump 62 in the exhaust path 60. The inside of the processing container 8 is evacuated.
In addition, a heat insulating layer 66 is provided on the outer periphery of the processing vessel 8, and a heater 68 is provided as a heating means on the inner side to heat the wafer W positioned inside to a predetermined temperature. ing. Here, the overall size of the processing vessel 8 is, for example, that the size of the wafer W to be deposited is 8 inches, the number of wafers held in the wafer boat 10 is about 150 (about 130 product wafers, dummy wafers, etc.). 20), the inner cylinder 4 has a diameter of about 260 to 270 mm, the outer cylinder 6 has a diameter of about 275 to 285 mm, and the processing vessel 8 has a height of about 1280 mm.

Further, when the size of the wafer W is 12 inches, the number of wafers held on the wafer boat 10 may be about 25 to 50. At this time, the diameter of the inner cylinder 4 is about 380 to 420 mm, The diameter of the cylinder 6 is about 440 to 500 mm, and the height of the processing container 8 is about 800 mm. These numerical values are merely examples.
Further, a seal member 70 such as an O-ring is provided between the cap 12 and the manifold 26, and an O-ring is provided between the manifold 26 and the lower end portion of the outer cylinder 6. A sealing member 72 is provided. Although not shown, as a gas supply system, for example, a gas supply system that supplies, for example, N ₂ gas as an inert gas is also provided.

Next, the method of the present invention performed using the heat treatment apparatus configured as described above will be described.
First, a process for forming a SiO ₂ film on the surface of the semiconductor wafer W using TEOS will be described. A large number of unprocessed semiconductor wafers W are held in multiple stages on the wafer boat 10 at a predetermined pitch, and in this state, the boat elevator 22 is driven upward to insert the wafer boat 10 into the processing container 8 from below. The inside of the processing container 8 is sealed. The inside of the processing container 8 is preheated in advance. When the wafer W is inserted as described above, the supply voltage to the heater 68 is increased to raise the temperature of the wafer W to a predetermined processing temperature, and the processing chamber 8 is evacuated by the vacuum exhaust system 64.

At the same time, a TEOS gas is supplied from the TEOS source 36 of the film forming gas supply system 28, and the flow-controlled TEOS gas is introduced into the processing container 8 from the film forming gas nozzle 30. The TEOS gas is formed by depositing a SiO ₂ film on the surface of the wafer W through a thermal decomposition reaction while rising in the processing chamber 8.
When the film forming process described above is completed, the supply of TEOS gas is stopped, the residual gas in the processing vessel 8 is purged with N ₂ gas and discharged, and then the wafer boat 10 is lowered. The processed wafer W is taken out. Then, a series of film forming processes as described above are repeated.

By repeating such a film forming process, unnecessary films (SiO 2 by TEOS) are formed on the surface of the internal structure, for example, the surface of the processing container 8 including the inner cylinder 4 and the outer cylinder 6, the surface of the wafer boat 10, and the surface of the heat insulating cylinder 20. since ₂ film) is attached, periodically or irregularly, a cleaning process for removing by scraping these unnecessary film is performed. In this cleaning process, the wafer W is not held in the wafer boat 10 (in an empty state), and this is inserted into the processing container 8 to seal the inside.
Then, while maintaining the temperature in the processing container 8 at a predetermined temperature, the HF gas whose flow rate is controlled is introduced from the HF gas nozzle 42 of the HF gas supply system 38 into the processing container 8 as the cleaning gas, and the NH ₃ gas An NH ₃ gas whose flow rate is controlled is introduced into the processing container 8 from the NH ₃ gas nozzle 50 of the supply system 40.

As described above, the HF gas and the NH ₃ gas separately introduced into the processing container 8 are mixed while rising in the processing container 8, and the mixed gas is mixed with the heat insulating cylinder 20, the wafer boat 10, the inner cylinder 4, and the outside. The silicon oxide film (SiO ₂ ) made of TEOS adhering to each surface of the cylinder 6 is removed by etching and cleaned.
The cleaning process time at this time is a time obtained by dividing the accumulated amount of unnecessary films by the etching rate, and is obtained by calculation, for example. Moreover, it is preferable that the processing conditions at the time of a cleaning process are the process temperature within the range of 100-300 degreeC. The processing pressure is 53200 Pa (400 Torr) or more, and the supply amount of HF gas to the NH ₃ gas is preferably equal to or higher than that of HF gas rich.

Thus, by using a mixed gas of HF gas and NH ₃ gas as the cleaning gas, an unnecessary silicon oxide film formed by TEOS can be quickly and efficiently scraped in a short time. Accordingly, the time required for the cleaning process is much shorter than in the case where HF gas is conventionally used alone as a cleaning gas, so that the cleaning time becomes excessively long due to calculation errors in the cleaning period. Even if the over-etching process is performed, the excess time can be shortened, so that damage to the internal structure, that is, the inner cylinder 4, the outer cylinder 6, the wafer boat 10, the heat retaining cylinder 20, and the like can be significantly suppressed. .

Here, since the comparison of the etching rate between the silicon oxide film (SiO ₂ ) formed using TEOS and the quartz material (SiO ₂ ) used for the processing vessel 8, the wafer boat 10, etc. was performed under various conditions, The evaluation result will be described. FIG. 2 is a diagram showing a comparison of etching rates between a silicon oxide film by TEOS and a quartz material. Here, the temperature at the time of the cleaning process is set to 300 ° C., which is the temperature at the time of the conventional general cleaning process, and the processing pressure is set to 400 Torr (53200 Pa). Further, the flow rate ratio between the HF gas and the NH ₃ gas is greatly changed. Note that 1 Torr = 133 Pa.

As apparent from FIG. 2, in the case of the conventional method, that is, when the processing temperature is 300 ° C., the processing pressure is 400 Torr, the HF gas flow rate is 1820 sccm, and the NH ₃ gas flow rate is zero, the etching of the silicon oxide film by TEOS is performed. While the rate is 0.4 nm / min, the etching rate for the quartz material forming the processing vessel 8 and the like is 170.1 nm / min. Thus, in the case of the conventional cleaning method, the evaluation is “x” (defective). That is, the etching rate with respect to the silicon oxide film by TEOS is considerably small. Therefore, the cleaning process must be performed for a long time, which causes a reduction in operating rate (a reduction in throughput). In addition, since the etching rate is small as described above, it is difficult to accurately determine the end point of the cleaning process. There is also the risk of damaging it.

On the other hand, in the case of the method of the present invention using a mixed gas of HF gas and NH ₃ gas as the cleaning gas, the evaluation is “Δ” (slightly good) or “◯” (good). In particular, when the flow rate ratio of HF gas and NH ₃ gas is set to 1000: 1000 or 1820: 182, respectively, that is, the supply amount of HF gas is set equal to or higher than the supply amount of NH ₃ gas. Sometimes (HF gas rich state), the etching rate for the silicon oxide film by TEOS is 26.8 nm / min and 96.6 nm / min, respectively, and an etching rate 67 to 240 times larger than the case of the conventional method can be obtained. did it. Accordingly, the time required for the cleaning process can be shortened accordingly, and the cleaning process can be performed efficiently, and the operating rate (throughput) of the apparatus can be improved.

  In this case, the etching rates for the quartz material are 69.1 nm / min and 196.6 nm / min, respectively, which are considerably large as in the case of the conventional method (170.1 nm / min). Since the total time required can be greatly reduced, even if an error occurs in the end point of the cleaning process, there is little time for erroneously performing the excessive cleaning process, and therefore, damage to the quartz material can be greatly suppressed. . For example, assuming that an error of 10% occurs in the cleaning process time, if the cleaning process time is calculated as 60 minutes in the case of the conventional method, the cleaning process may be excessively performed for 6 minutes. In contrast, in the case of the method of the present invention, the cleaning processing time is 0.6 minutes (when the etching rate is 96.6 nm / min), so that the cleaning processing is performed for 0.06 minutes (3.6 seconds). Therefore, in the case of the method of the present invention, damage to the quartz material can be suppressed to a much smaller extent.

In the case of the present invention method, and 182sccm the supply of HF gas, the evaluation when the state of the NH ₃ gas rich a supply amount of the NH ₃ gas as 1820sccm is "△", etching of TEOS Niyoriru silicon oxide film The rate is 0.6 nm / min, which is about 1.5 times larger than the conventional method of 0.4 nm / min. In this case as well, although not as high as the case of the above-described HF gas rich state, a sufficient effect is expected. be able to. In this case, the etching rate with respect to the quartz material is 15.9 nm / min, which is considerably small, and accordingly, damage to the quartz material when the cleaning process is excessively performed can be suppressed.

Further, in addition to the above evaluation experiment, the evaluation of the etching rate of the etching gas (mixed gas of HF gas and NH ₃ gas) with respect to the silicon oxide film by TEOS was performed supplementarily, and the result will be described. The processing temperature is maintained at 300 ° C. (same as in FIG. 2), the processing pressure is set at 150 Torr (lower than in FIG. 2), and the flow rate ratio of HF gas to NH ₃ gas is 1: 10-10. The cleaning process was performed with various changes in the range of 1: 1. In this case, the silicon oxide film by TEOS could hardly be etched. Further, when the processing pressure was set higher than 400 Torr under the same conditions as described above, the silicon oxide film by TEOS could be sufficiently etched. Therefore, it was confirmed that the pressure during the cleaning process needs to be set to 400 Torr or more.

Further, the processing temperature is set to 400 ° C. (higher than in the case of FIG. 2), the processing pressure is set to 400 Torr (the same as in the case of FIG. 2), and the flow rate ratio of HF gas to NH ₃ gas is set to 1:10. The cleaning process was performed with various changes in the range of 10: 1 as shown in FIG. As a result, the silicon oxide film by TEOS could hardly be etched.
In contrast, the processing temperature is set to 100 ° C. (lower than in the case of FIG. 2), the processing pressure is set to 400 Torr (the same as in FIG. 2), and the flow rate ratio of HF gas to NH ₃ gas is set to 1. When the cleaning process was performed at a setting of 1 (1000 sccm: 1000 sccm), the silicon oxide film by TEOS could be etched at an etching rate of 6 nm / min, and the effectiveness could be confirmed. Further, cleaning treatment was performed at room temperature under the same conditions, but the silicon oxide film by TEOS could not be etched. Therefore, it has been confirmed that the processing temperature needs to be set within the range of 100 to 300 ° C.

FIG. 3 is a configuration diagram showing another example of a heat treatment apparatus in which the cleaning method according to the present invention is performed. The heat treatment apparatus shown in FIG. 3 is a heat treatment apparatus that performs an AsSG film (arsenic glass film) film formation process on an object to be processed using TEOS in a processing container that can be evacuated.
The heat treatment apparatus shown in FIG. 3 is provided with a second film formation gas supply system 128 that supplies a TEOA gas for film formation. Specifically, the second film-forming gas supply system 128 has a second film-forming gas nozzle 130 that penetrates the manifold 26. A gas supply path 134 in which a flow rate controller 132 such as a mass flow controller is interposed is connected to the second film forming gas nozzle 130. A TEOA source 136 that stores TEOA (Ttieoxyrsenic) as the second film forming gas is connected to the gas supply path 134. Thereby, the TEOA gas can be supplied into the processing container 8 while the flow rate is controlled during the film forming process.
The other structure of the heat treatment apparatus of FIG. 3 is the same as that of the heat treatment apparatus of FIG. In FIG. 3, the same parts as those of the heat treatment apparatus of FIG.

Next, the method of the present invention performed using the heat treatment apparatus configured as described above will be described.
First, a process for forming an AsSG film on the surface of the semiconductor wafer W using TEOS and TEOA will be described.
A large number of unprocessed semiconductor wafers W are held on the wafer boat 10 in multiple stages at a predetermined pitch. The wafer boat 10 in this state is inserted into the processing container 8 from below by driving up the boat elevator 22. The cap 12 seals the inside of the processing container 8. The inside of the processing container 8 is preheated in advance. If the wafer W is inserted as described above, the supply voltage to the heater 68 is increased and the wafer W is heated to a predetermined processing temperature. On the other hand, the inside of the processing container 8 is evacuated by the vacuum exhaust system 64.

At the same time, TEOS from the TEOS source 36 of the film forming gas supply system 28 is introduced into the processing container 8 through the film forming gas nozzle 130 while the flow rate is controlled. Similarly, TEOA from the TEOA source 136 of the second film-forming gas supply system 128 is introduced into the processing container 8 through the film-forming gas nozzle 130 while the flow rate is controlled. The TEOS gas and the TEOA gas are thermally decomposed while rising in the processing container 8 to deposit an AsSG film on the surface of the wafer W.
When the above film forming process is completed, the supply of the TEOS gas and the TEOA gas is stopped, and the residual gas in the processing container 8 is purged with N ₂ gas or the like and discharged. Thereafter, the wafer boat 10 is lowered and the processed wafers W are taken out. Then, a series of film forming processes as described above are repeated.

By repeating such film formation processing, unnecessary films (by TEOS and TEOA) are formed on the surface of the internal structure, for example, the surface of the processing vessel 8 including the inner cylinder 4 and the outer cylinder 6, the surface of the wafer boat 10, and the surface of the heat insulating cylinder 20. (AsSG film) adheres. Therefore, a cleaning process for scraping and removing these unnecessary films is performed regularly or irregularly.
In this cleaning process, the wafer boat 10 that does not hold the wafer W is inserted into the processing container 8. Then, the inside of the processing container 8 is sealed. The temperature in the processing container 8 is maintained at a predetermined temperature. In this state, the flow rate-controlled HF gas is introduced into the processing container 8 from the HF gas nozzle 42 of the HF gas supply system 38 as a cleaning gas. On the other hand, NH ₃ gas from the NH ₃ gas nozzle 50 of the NH ₃ gas supply system 40 is flow control is introduced into the processing vessel 8.

As described above, the HF gas and the NH ₃ gas separately introduced into the processing container 8 are mixed while rising in the processing container 8. This mixed gas scrapes off the AsSG film by TEOS and TEOA adhering to each surface of the heat retaining cylinder 20, the wafer boat 10, the inner cylinder 4, the outer cylinder 6 and the like by etching, that is, cleans it.
The cleaning process time at this time is a time obtained by dividing the accumulated amount of unnecessary films by the etching rate, and is obtained by calculation, for example. As for the processing conditions during the cleaning process, the processing temperature is preferably in the range of 100 to 300 ° C. Further, the processing pressure is 53200 Pa (400 Torr) or more, and the supply amount of HF gas to the NH ₃ gas is preferably equal to or higher than that in the HF gas rich state.

As described above, by using a mixed gas of HF gas and NH ₃ gas as the cleaning gas, an unnecessary arsenic glass film formed by TEOS and TEOA can be scraped quickly and efficiently in a short time. Therefore, the time required for the cleaning process can be much shorter than when HF gas is conventionally used alone as a cleaning gas. Therefore, even if the cleaning time becomes excessively long due to a calculation error of the cleaning time and the like, and the overcleaning process is performed, the excessive time is short, so that the internal structure, that is, the inner cylinder 4, the outer cylinder 6, the wafer The damage given to the boat 10, the heat insulation cylinder 20, etc. can be suppressed significantly.
FIG. 4 is a configuration diagram showing still another example of a heat treatment apparatus in which the cleaning method according to the present invention is performed. The heat treatment apparatus shown in FIG. 4 is a heat treatment apparatus that performs a film formation process of a BSG film (boron glass film) on a target object using TEOS in a processing container that can be evacuated.

The heat treatment apparatus of FIG. 4 is provided with a third film forming gas supply system 228 for supplying a film forming BCl ₃ gas. Specifically, the third film forming gas supply system 228 includes a third film forming gas nozzle 230 that penetrates the manifold 26. A gas supply path 234 in which a flow rate controller 232 such as a mass flow controller is interposed is connected to the third film forming gas nozzle 230. A BCl ₃ source 236 that stores BCl ₃ gas as the third film forming gas is connected to the gas supply path 234. As a result, during the film forming process, the BCl ₃ gas can be supplied into the processing vessel 8 while the flow rate is controlled.
The other configuration of the heat treatment apparatus of FIG. 4 is the same as that of the heat treatment apparatus of FIG. In FIG. 4, the same parts as those in the heat treatment apparatus in FIG.

Next, the method of the present invention performed using the heat treatment apparatus configured as described above will be described.
First, a process for forming a BSG film on the surface of the semiconductor wafer W using TEOS and BCl ₃ will be described.
A large number of unprocessed semiconductor wafers W are held on the wafer boat 10 in multiple stages at a predetermined pitch. The wafer boat 10 in this state is inserted into the processing container 8 from below by driving up the boat elevator 22. The cap 12 seals the inside of the processing container 8. The inside of the processing container 8 is preheated in advance. If the wafer W is inserted as described above, the supply voltage to the heater 68 is increased and the wafer W is heated to a predetermined processing temperature. On the other hand, the inside of the processing container 8 is evacuated by the vacuum exhaust system 64.

At the same time, TEOS from the TEOS source 36 of the film forming gas supply system 28 is introduced into the processing container 8 through the film forming gas nozzle 30 while the flow rate is controlled. Similarly, the BCl ₃ gas from the BCl ₃ source 236 of the third film forming gas supply system 228 is introduced into the processing container 8 through the third film forming gas nozzle 230 while the flow rate is controlled. The TEOS gas and the BCl ₃ gas are formed by depositing a BSG film on the surface of the wafer W through a thermal decomposition reaction while rising in the processing vessel 8.
When the film forming process described above is completed, the supply of the TEOS gas and the BCl ₃ gas is stopped, and the residual gas in the processing container 8 is purged with N ₂ gas or the like and discharged. Thereafter, the wafer boat 10 is lowered and the processed wafers W are taken out. Then, a series of film forming processes as described above are repeated.

By repeating the film forming process, unnecessary films (TEOS and BCl) are formed on the surface of the internal structure, for example, the surface of the processing container 8 including the inner cylinder 4 and the outer cylinder 6, the surface of the wafer boat 10, and the surface of the heat insulating cylinder 20. ₃ is attached. Accordingly, a cleaning process is performed to scrape and remove these unnecessary films periodically or irregularly.
In this cleaning process, the wafer boat 10 that does not hold the wafer W is inserted into the processing container 8. Then, the inside of the processing container 8 is sealed. The temperature in the processing container 8 is maintained at a predetermined temperature. In this state, the flow rate-controlled HF gas is introduced into the processing container 8 from the HF gas nozzle 42 of the HF gas supply system 38 as a cleaning gas. On the other hand, NH ₃ gas nozzle 50 of the NH ₃ gas supply system 40 has its flow rate controlled NH ₃ gas is introduced into the processing vessel 8.

As described above, the HF gas and the NH ₃ gas separately introduced into the processing container 8 are mixed while rising in the processing container 8. This mixed gas scrapes off the BSG film formed of TEOS and BCl ₃ adhering to the surfaces of the heat retaining cylinder 20, the wafer boat 10, the inner cylinder 4, the outer cylinder 6 and the like by etching, that is, cleans it.
The cleaning process time at this time is a time obtained by dividing the accumulated amount of unnecessary films by the etching rate, and is obtained by calculation, for example. As for the processing conditions during the cleaning process, it is preferable that the processing temperature is in the range of 100 to 300 ° C. Further, the processing pressure is 53200 Pa (400 Torr) or more, and the supply amount of HF gas to the NH ₃ gas is preferably equal to or higher than that in the HF gas rich state.

As described above, by using a mixed gas of HF gas and NH ₃ gas as the cleaning gas, an unnecessary boron glass film formed of TEOS and BCl ₃ can be quickly and efficiently scraped in a short time. Therefore, the time required for the cleaning process can be much shorter than when HF gas is used alone as a cleaning gas in the future. Accordingly, even if the cleaning time becomes excessively long due to the calculation error of the cleaning time and the overetching process is performed, the excessive time is short, so that the internal structure, that is, the inner cylinder 4, the outer cylinder 6, Damage to the wafer boat 10 and the heat insulating cylinder 20 can be greatly suppressed.

In the above description, a batch type heat treatment apparatus having a double pipe structure has been described as an example. However, the present invention can also be applied to a single pipe structure heat treatment apparatus or a single wafer type heat treatment apparatus. The silicon oxide film using can be efficiently cleaned.
In addition, the object to be processed is not limited to a semiconductor wafer, and can naturally be applied to a heat treatment apparatus for glass substrates and LCD substrates.

It is a block diagram which shows an example of the heat processing apparatus with which the cleaning method which concerns on this invention is implemented. It is a figure which shows the comparison of the etching rate of the silicon oxide film and quartz material by TEOS. It is a block diagram which shows the other example of the heat processing apparatus with which the cleaning method which concerns on this invention is implemented. It is a block diagram which shows the further another example of the heat processing apparatus with which the cleaning method which concerns on this invention is implemented.

Explanation of symbols

2 Heat treatment equipment 8 Processing container 10 Wafer boat (support shelf)
28 Gas supply system for film formation 36 TEOS source 38 HF gas supply system 40 NH ₃ gas supply system 48 HF gas source 56 NH ₃ gas source 68 Heating heater (heating means)
W Semiconductor wafer (object to be processed)

Claims (2)

A film containing an impurity with arsenic glass film or TEOS is a film containing an impurity with a SiO ₂ film or TEOS using TEOS against the workpiece in an evacuable to made the quartz processing vessel a cleaning method of a heat treatment apparatus for performing a film forming process of a boron silicate glass film,
While supplying HF gas and NH ₃ gas into the processing container, the temperature of the processing container is set in a range of 100 to 300 ° C., and the pressure in the processing container is set to 53200 Pa (400 Torr) or more. A cleaning method for a heat treatment apparatus, comprising a cleaning step. 2. The cleaning method for a heat treatment apparatus according to claim 1, wherein, in the cleaning step, a supply amount of HF gas is equal to or more than a supply amount of NH ₃ gas.

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