JP4039385B2 - Removal method of chemical oxide film - Google Patents

Description

The present invention is related to a method for removing the chemical oxide film formed on the surface of the object to be processed such as a semiconductor wafer.

Generally, in order to manufacture a semiconductor integrated circuit, various processes such as a film formation process, an etching process, an oxidation process, a diffusion process, and a modification process are performed on a semiconductor wafer made of a silicon substrate or the like. In this case, the semiconductor wafer is exposed to a clean atmosphere when the semiconductor wafer is transferred from the processing container to the next processing container in order to end a certain process and proceed to the next processing. At this time, oxygen and moisture in the atmosphere react with active silicon atoms exposed on the wafer surface to form a natural oxide film made of SiO ₂ . Since this natural oxide film causes a decrease in electrical characteristics, the natural oxide film is removed by wet cleaning using, for example, an HF solution before the next processing is performed on the semiconductor wafer. . Patent Document 1 discloses a method for selectively removing silicon oxide films having different film qualities using HF gas at room temperature.

Since the surface of the wafer from which the natural oxide film has been removed by this cleaning is rich in activity, when the wafer is exposed to the atmosphere, the above-mentioned natural oxide film (SiO ₂ ) adheres again. Therefore, in order to prevent the re-adhesion of the natural oxide film, a chemical treatment is actively performed in a wet state on the wafer surface from which the natural oxide film has been removed to attach a chemical oxide film (SiO ₂ ), and this chemical oxidation is performed. The wafer with the film attached was transferred to a processing vessel for the next processing, and the next processing was performed with the chemical oxide film attached. That is, this chemical oxide film is excellent in electrical characteristics as compared with the natural oxide film, and is formed with good uniformity in the wafer surface, so that the next treatment is, for example, the formation of a gate oxide film. In this case, a thermal oxide film (SiO ₂ ) or the like is formed with the chemical oxide film attached.

Here, a series of processing steps on the surface of the semiconductor wafer will be described with reference to FIG. Here, a case where a thermal oxide film (SiO ₂ ) to be a gate oxide film is formed on the surface of the semiconductor wafer will be described as an example.
First, as shown in FIG. 10A, since the surface of a semiconductor wafer W made of, for example, a silicon substrate is exposed to the atmosphere or the like, oxygen, water vapor (moisture) in the atmosphere reacts with silicon atoms. As a result, a natural oxide film (SiO ₂ ) having inferior electrical characteristics adheres with a non-uniform thickness. Therefore, as shown in FIG. 10B, first, a wet cleaning process using an HF solution is performed on the semiconductor wafer W to remove the natural oxide film 2 on the surface. Here, since the surface of the wafer W from which the natural oxide film 2 has been removed is very active, it reacts with oxygen and water vapor, so that the natural oxide film easily adheres again.

Therefore, in order to prevent the natural oxide film from adhering again, as shown in FIG. 10C, for example, H ₂ O ₂ and NH ₄ OH are formed on the surface of the wafer W from which the natural oxide film 2 has been removed. A chemical oxide film (SiO ₂ ) 4 is formed as a protective film by performing a chemical treatment using the mixed solution and slightly oxidizing the surface. As described above, the chemical oxide film 4 has better electrical characteristics than the natural oxide film 2, has a small film thickness, and is excellent in in-plane uniformity. The thickness L of the chemical oxide film 4 is, for example, about 0.7 to 0.9 nm.

Next, as shown in FIG. 10D, for example, the wafer W is transferred to a thermal oxidation apparatus, and the wafer W is subjected to a thermal oxidation process (for example, Patent Document 2 and Patent Document 3), thereby forming a thermal oxide film. (SiO ₂ ) 6 is formed, and this is used as a gate oxide film by pattern etching or the like in a later process. In this case, the thermal oxide film 6 is formed at the interface between the chemical oxide film 4 and the silicon surface of the wafer W.

JP-A-6-181188 Japanese Patent Laid-Open No. 3-140453 JP 2002-176052 A

By the way, the demand for further integration and miniaturization of the semiconductor integrated circuit tends to further reduce the film thickness per layer. Under such circumstances, the target value of the film thickness per layer can also be formed, for example, with a controllability of a gate oxide film having a thickness of 1.0 to 1.2 nm, for example, by taking a gate oxide film as an example. It is desired.
However, as described above, the thickness L of the chemical oxide film 4 is only about 0.7 to 0.9 nm, but the target value of the gate oxide film (chemical oxide film 4 + thermal oxide film 6) as described above. When the thickness is reduced to about 1.0 to 1.2 nm, the ratio of the thickness of the chemical oxide film 4 to the total thickness of the gate oxide film increases, and it is difficult to sufficiently control the thickness of the gate oxide film. There was a problem of becoming. Such a problem is not limited to the case of forming a gate oxide film, but the same problem has been associated with the controllability of the film thickness when a thin film of another film type is formed.

In this case, it is conceivable to remove the chemical oxide film using HF gas as in Patent Document 1, but when this HF gas is used alone, the treatment must be performed at room temperature, and in particular the heat capacity. However, it takes a lot of time to raise and lower the temperature of the entire processing vessel in a large vertical furnace, which causes a significant reduction in throughput.
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 provide a method for removing a chemical oxide film that can efficiently remove the chemical oxide film at a temperature considerably higher than room temperature.

The invention according to claim 1 is a silicon oxide film formed on the surface of an object to be processed in a processing container that can be evacuated, and a mixed solution of H ₂ O ₂ and NH ₄ OH treated in removing method for removing a chemical oxide film formed by Ke Michal treatment with a mixed gas of HF gas and NH ₃ gas in order to obtain a selectivity of the chemical oxide film to the silicon material used The temperature is set in the range of 200 ° C. to 400 ° C., the processing pressure is set in the range of 26 Pa (0.2 Torr) to 53200 Pa (400 Torr), and the flow rate ratio of the HF gas and NH ₃ gas is as follows: The chemical oxide film removing method is characterized in that the chemical oxide film is set within a range of 10: 1 to 1:50.
As described above, by using a mixed gas of HF gas and NH ₃ gas, it becomes possible to efficiently remove the silicon oxide film which is a chemical oxide film formed on the surface of the object to be processed.

Further, the silicon oxide film made of a chemical oxide film with respect to the silicon material can be etched and removed with high selectivity.

The invention according to claim 2 is a silicon oxide film formed on the surface of an object to be processed in a processing vessel that can be evacuated, and a mixed solution of H ₂ O ₂ and NH ₄ OH In the removal method for removing the chemical oxide film formed by the used chemical treatment, a mixed gas of HF gas and NH ₃ gas is used, and treatment is performed to obtain the selectivity of the chemical oxide film with respect to the silicon nitride film The temperature is set in the range of 200 ° C. to 600 ° C., the processing pressure is set to 53200 Pa (400 Torr) or less, and the flow rate ratio of the HF gas to NH ₃ gas is in the range of 1:10 to 1:50. The chemical oxide film removal method is characterized in that the chemical oxide film is removed by setting to 1.
According to this, the silicon oxide film made of the chemical oxide film can be etched and removed with high selectivity with respect to the silicon nitride film.

The invention defined in claim 3 is a silicon oxide film formed on the surface of an object to be processed in a processing vessel that can be evacuated, and is a mixed solution of H ₂ O ₂ and NH ₄ OH. In the removal method for removing the chemical oxide film formed by the chemical treatment using HF, the mixed gas of HF gas and NH ₃ gas is used and the silicon oxide film formed by CVD (Chemical Vapor Deposition) is used. In order to obtain the selectivity of the chemical oxide film, the processing temperature is set in a range of 200 ° C. to 400 ° C., the processing pressure is set to 53200 Pa (400 Torr) or less, and the flow rate ratio of the HF gas and NH ₃ gas is A chemical that is set within a range of 1:10 to 1:50 and removes the chemical oxide film. A method of removing the oxide film.
According to this, a silicon oxide film made of a chemical oxide film can be etched and removed with high selectivity with respect to a silicon oxide film formed by CVD.

The invention defined in claim 4 is a silicon oxide film formed on the surface of an object to be processed in a processing vessel that can be evacuated, and is a mixed solution of H ₂ O ₂ and NH ₄ OH. In order to obtain a selectivity of the chemical oxide film with respect to the thermal oxide film, a mixed gas of HF gas and NH ₃ gas is used in the removal method for removing the chemical oxide film formed by the chemical treatment using The processing temperature is set in the range of 100 ° C. to 600 ° C., the processing pressure is set to 53200 Pa (400 Torr) or less, and the flow rate ratio of the HF gas to NH ₃ gas is in the range of 1:10 to 1:50. The chemical oxide film removal method is characterized in that the chemical oxide film is removed by setting to 1.
According to this, the silicon oxide film made of the chemical oxide film can be etched and removed with high selectivity with respect to the thermal oxide film (SiO ₂ ).
The related technology of the present invention is to remove a silicon oxide film formed on the surface of an object to be processed, which is formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the processing apparatus, the processing container made evacuable, the support means for holding the object to be processed, the heating means for heating the object to be processed, and the atmosphere in the processing container are evacuated. a vacuum pumping system, and HF gas supply system for supplying HF gas into the processing chamber, and a NH ₃ gas supply system for supplying NH ₃ gas into the processing container, during the heat treatment, the HF gas and NH ₃ with a mixed gas of the gas, the treatment temperature in order to obtain a selectivity of the chemical oxide film to the silicon material set in the range of 200 ° C. to 400 ° C., the process pressure 26 Pa (0. Is set within a range of Torr) ~53200Pa (400Torr), further flow ratio of said HF gas and NH ₃ gas is 10: 1 to 1: is in the range of 50 to remove the chemical oxide film This is a processing apparatus characterized by the above.
The related technology of the present invention is to remove a silicon oxide film formed on the surface of an object to be processed, which is formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the processing apparatus, the processing container made evacuable, the support means for holding the object to be processed, the heating means for heating the object to be processed, and the atmosphere in the processing container are evacuated. a vacuum pumping system, and HF gas supply system for supplying HF gas into the processing chamber, and a NH ₃ gas supply system for supplying NH ₃ gas into the processing container, during the heat treatment, the HF gas and NH ₃ with a mixed gas of a gas, is set within a range of the processing temperature is 200 ° C. to 600 ° C. in order to obtain a selectivity of the chemical oxide film to the silicon nitride film, process pressure 53200P (400 Torr) is set below, further flow ratio of said HF gas and NH ₃ gas is 1: 10 to 1: characterized in that it is set to so as to remove the chemical oxide film in the range of 50 It is a processing device.

The related technology of the present invention is to remove a silicon oxide film formed on the surface of an object to be processed, which is formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the processing apparatus, the processing container made evacuable, the support means for holding the object to be processed, the heating means for heating the object to be processed, and the atmosphere in the processing container are evacuated. a vacuum pumping system, and HF gas supply system for supplying HF gas into the processing chamber, and a NH ₃ gas supply system for supplying NH ₃ gas into the processing container, during the heat treatment, the HF gas and NH ₃ with a mixed gas of the gas, the treatment temperature in order to obtain a selectivity of the chemical oxide film to the silicon oxide film formed by CVD is in the range of 200 ° C. to 400 ° C., treatment The pressure is set to less than 53,200 Pa (400 Torr), further wherein the HF gas and the NH ₃ flow rate ratio of the gas is 1: 10 to 1: is in the range of 50 to that so as to remove the chemical oxide film It is the processing apparatus characterized.
The related technology of the present invention is to remove a silicon oxide film formed on the surface of an object to be processed, which is formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the processing apparatus, the processing container made evacuable, the support means for holding the object to be processed, the heating means for heating the object to be processed, and the atmosphere in the processing container are evacuated. a vacuum pumping system, and HF gas supply system for supplying HF gas into the processing chamber, and a NH ₃ gas supply system for supplying NH ₃ gas into the processing container, during the heat treatment, the HF gas and NH ₃ with a mixed gas of the gas, the treatment temperature in order to obtain a selectivity of the chemical oxide film to a thermal oxide film is in the range of 100 ° C. to 600 ° C., the process pressure 53,200 Pa (40 Torr) is set to, further the HF gas and the NH ₃ flow rate ratio of the gas is 1: 10-1: processing is set in the range of 50, characterized in that so as to remove the chemical oxide film Device.
In this case, for example, an oxidizing gas supply system for supplying water vapor or a gas for forming water vapor is provided in the processing container.
Further, for example , a silicon film forming gas supply system for supplying a gas for forming a silicon film is provided in the processing container.

By the method of removing the chemical oxide film of the present invention lever can exhibit an excellent action and effect as follows.
According to the engaging Ru invention in claim 1, effectively removing the silicon oxide film is chemical oxide film formed by a chemical treatment on the surface of the object to be processed by using the mixed gas of HF gas and NH ₃ gas can do.
Further, the silicon oxide film made of a chemical oxide film with respect to the silicon material can be etched and removed with high selectivity.
According to the engaging Ru invention in claim 2, effectively removing the silicon oxide film is chemical oxide film formed by a chemical treatment on the surface of the object to be processed by using the mixed gas of HF gas and NH ₃ gas In addition, the silicon oxide film made of a chemical oxide film with respect to the silicon nitride film can be etched and removed with high selectivity.
According to the invention of claim 3, by using a mixed gas of HF gas and NH ₃ gas, the silicon oxide film, which is a chemical oxide film formed on the surface of the object by chemical treatment, is efficiently removed. In addition, a silicon oxide film made of a chemical oxide film can be etched and removed with high selectivity with respect to a silicon oxide film formed by CVD.
According to the engaging Ru invention in claim 4, effectively removing the silicon oxide film is chemical oxide film formed by a chemical treatment on the surface of the object to be processed by using the mixed gas of HF gas and NH ₃ gas In addition, the silicon oxide film made of a chemical oxide film can be etched and removed with high selectivity with respect to the thermal oxide film (SiO ₂ ).

Hereinafter will be described in detail with reference to Kazumi施例the method for removing the chemical oxide film according to the present invention in the accompanying drawings.
FIG. 1 is a block diagram showing an example of a processing apparatus for carrying out the method for removing a chemical oxide film according to the present invention. The processing apparatus 12 includes a vertical processing container 18 having a predetermined length of a quartz double pipe structure including an inner cylinder 14 and an outer cylinder 16. The processing space S in the inner cylinder 14 accommodates a quartz wafer boat 20 as a support means for holding the object to be processed. The wafer boat 20 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 22 is provided to open and close the lower portion of the processing container 18, and a rotary shaft 26 is provided through the cap 22 via a magnetic fluid seal 24. A rotary table 28 is provided at the upper end of the rotary shaft 26, a heat insulating cylinder 30 is provided on the table 28, and the wafer boat 20 is placed on the heat insulating cylinder 30. The rotating shaft 26 is attached to an arm 34 of a boat elevator 32 that can be moved up and down, and can be moved up and down integrally with the cap 22 and the wafer boat 20. The wafer boat 20 is moved into the processing container 18. It can be inserted and removed from below. The wafer boat 20 may be fixed without rotating.
A stainless steel manifold 36, for example, is joined to the lower end opening of the processing vessel 18, and HF for introducing flow-controlled HF gas and NH ₃ gas into the processing vessel 18 is connected to the manifold 36. A gas supply system 38 and an NH ₃ gas supply system 40 are individually provided.

Specifically, first, the HF gas supply system 38 has an HF gas nozzle 42 provided through the manifold 36, 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 36. A flow rate controller 52 such as a mass flow controller is provided in the nozzle 50 on the way. 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 42 and 50 ascend the wafer storage area, which is the processing space S in the inner cylinder 14, and turn downward at the ceiling, and the inner cylinder 14 and the outer cylinder 16. Then, it flows down in the gap of the gas and is discharged. In addition, an exhaust port 58 is provided in the bottom side wall of the outer cylinder 16, and a vacuum exhaust system 64 is connected to the exhaust port 58, and a vacuum pump 62 is connected to the exhaust path 60. The inside of the processing container 18 is evacuated.
In addition, a heat insulating layer 66 is provided on the outer periphery of the processing vessel 18, and a heater 68 is provided on the inner side as a heating unit to heat the wafer W positioned on the inner side to a predetermined temperature. ing. Here, the overall size of the processing container 18 is, for example, the size of the wafer W to be deposited is 8 inches, the number of wafers held in the wafer boat 20 is about 150 (about 130 product wafers, dummy wafers, etc.). 20), the inner cylinder 14 has a diameter of about 260 to 270 mm, the outer cylinder 16 has a diameter of about 275 to 285 mm, and the processing container 18 has a height of about 1280 mm.

Further, when the size of the wafer W is 12 inches, the number of wafers held in the wafer boat 20 may be about 25 to 50. At this time, the diameter of the inner cylinder 14 is about 380 to 420 mm, The diameter of the cylinder 16 is about 440 to 500 mm, and the height of the processing container 18 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 22 and the manifold 36, and this is sealed between the upper end portion of the manifold 36 and the lower end portion of the outer cylinder 16. A sealing member 72 such as an O-ring 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 processing apparatus configured as described above will be described.
Here, a case where a chemical oxide film (SiO ₂ ) is removed as a silicon oxide film to be removed will be described as an example.
FIG. 2 is a process diagram showing a part of a semiconductor wafer processing process. On the surface of the semiconductor wafer W shown in FIG. 2 (A), which is chemical oxide film 4 is formed as a silicon oxide film, the wafer W with a the chemical oxide film 4, FIGS. 10 (A) and above As described with reference to FIG. 10 (B ), after removing the natural oxide film 2 on the wafer surface, the surface of the wafer W is subjected to chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. Is formed.

Here, the wafer W with the chemical oxide film 4 is accommodated in the processing apparatus 12, and a mixed gas of HF gas and NH ₃ gas is used here, as shown in FIG. The oxide film 4 is removed by etching.
Thereafter, as shown in FIG. 2C, the thermal oxide film 6 is formed to form, for example, a gate oxide film in another processing apparatus. In the embodiment described later, the removal process of the chemical oxide film 4 and the formation process of the thermal oxide film 6 can be performed in the same processing apparatus.

Next, the removal process of the chemical oxide film 4 performed using the processing apparatus 12 will be specifically described.
First, as shown in FIG. 2A, a large number of unprocessed semiconductor wafers W having a chemical oxide film 4 on the surface are held in a multi-stage at a predetermined pitch on the wafer boat 20, and the boat elevator 32 is moved in this state. By driving up, the wafer boat 20 is inserted into the processing container 18 from below, and the processing container 18 is sealed. The inside of the processing container 18 is previously maintained at a predetermined temperature, and the chemical oxide film 4 is formed on the surface of the semiconductor wafer W as described above, for example. When the wafer W is inserted as described above, the processing chamber 18 is evacuated by the vacuum exhaust system 64.

At the same time, the HF gas whose flow rate is controlled from the HF gas nozzle 42 of the HF gas supply system 38 is introduced into the processing vessel 18 and the NH ₃ gas whose flow rate is controlled from the NH ₃ gas nozzle 50 of the NH ₃ gas supply system 40. Is introduced into the processing vessel 18.
As described above, the HF gas and the NH ₃ gas separately introduced into the processing container 18 are mixed while rising in the processing container 18, and this mixed gas etches the chemical oxide film 4 formed on the wafer W. And can be removed.
Regarding the etching processing conditions at this time, the processing temperature is higher than room temperature, for example, within a range of 100 ° C. to 600 ° C. 0.2 Torr) to 53200 Pa (400 Torr).

As described above, the HF (hydrogen fluoride) gas alone cannot remove the silicon oxide film unless the temperature of the processing vessel 18 is lowered to around room temperature. However, by mixing NH ₃ (ammonia) gas, the processing vessel 18 is mixed. The silicon oxide film, here the chemical oxide film, can be removed without lowering the temperature of the substrate to near room temperature. Therefore, the time for raising and lowering the temperature of the processing vessel 18 can be reduced, so that the throughput can be improved. .

  Thus, the wafer W from which the chemical oxide film 4 has been removed is obtained when the thermal oxide film forming member is provided in the processing apparatus 12 and the above member is not provided in the processing apparatus. As shown in FIG. 2C, for example, a thermal oxide film 6 for a gate oxide film is formed by an oxidation process. In this case, as described above, even if the gate oxide film is required to be thinned for high miniaturization and high integration of the semiconductor integrated circuit, the target film thickness value is reduced to about 1.0 to 1.2 nm. The thermal oxide film 6 can be formed with good controllability of film thickness.

Here, since the actual change in the thickness of the chemical oxide film (SiO ₂ ) was evaluated, the evaluation result will be described. FIG. 3 is a graph showing changes in the film thickness of the chemical oxide film. In the figure, “TOP” indicates the position of the upper portion of the wafer boat 20, and “BTM” indicates the position of the lower portion of the wafer boat 20. The processing conditions here are a processing temperature of 300 ° C., a processing pressure of 53200 Pa (400 Torr), a flow rate of HF gas of 182 sccm, a flow rate of NH ₃ gas of 1820 sccm, a flow rate of N ₂ gas of 8000 sccm, and etching for 10 minutes. Processed.
As is apparent from FIG. 3, the film thickness greatly changes before and after the treatment in both “TOP” and “BTM”, and the chemical oxide film has a thickness of 0.39 to 0. It was confirmed that the material could be scraped off in the range of about 41 nm.

Next, since the effectiveness of adding and mixing NH ₃ gas was evaluated, the evaluation result will be described. FIG. 4 is a graph showing the NH ₃ gas dependency of the amount of abrasion of the chemical oxide film. In FIG. 4, the left part shows a case where only HF gas is used, and the right part shows a case where a mixed gas of HF gas and NH ₃ gas is used. The processing conditions here are the same as those described with reference to FIG. 3, the processing temperature is 300 ° C., the processing pressure is 53200 Pa (400 Torr), the flow rate of HF gas is 182 sccm, the flow rate of NH ₃ gas is 1820 sccm, and N _2. The gas flow rate was 8000 sccm, and the etching process was performed for 10 minutes.
As is apparent from FIG. 4, when the treatment is performed only with the HF gas without adding the NH ₃ gas, the chemical oxide film is hardly scraped, whereas the mixed gas of the HF gas and the NH ₃ gas is changed. It has been found that when used, the thickness can be cut off by about 0.59 to 0.61 nm. As a result, it was found that the chemical oxide film could not be removed unless NH ₃ gas was added.

Next, since the selectivity with other silicon oxide films and silicon-containing materials other than the chemical oxide film was evaluated, the evaluation results will be described. FIG. 5 is data showing the presence / absence of selectivity between the chemical oxide film and other silicon oxide films and silicon-containing materials. The pressure is 1 Torr = 133 Pa, and the selective portion is marked with “◯”. Further, “-” in FIG. 5 means that Si material is over-etched and measurement is impossible.
Here, the processing temperature is changed from 100 to 600 ° C., the processing pressure is changed from 26 Pa (0.2 Torr) to 53200 Pa (400 Torr), and the etching process is performed for 10 minutes. Note that the pressure “VAC” in FIG. 5 indicates the pressure when the inside of the processing vessel 18 is evacuated by vacuuming, and the pressure in the processing vessel 18 at that time is 26 Pa, depending on the capacity of the vacuum pump and the like. It is about (0.2 Torr) to 40 Pa (0.3 Torr). The flow rate ratio between HF gas and NH ₃ gas is changed within the range of 1:10 to 10: 1. Each numerical value in this figure indicates the thickness removed by the etching process for 10 minutes, and its unit is nm.

The material used in the evaluation is a chemical oxide film, a silicon material (polysilicon film), a silicon nitride film (SiN), a silicon oxide film formed using TEOS as a silicon oxide film other than the chemical oxide film, and heat. A thermal oxide film formed by oxidation treatment was used.
First, when the chemical oxide film was examined, it was confirmed that the chemical oxide film could be scraped in all regions within the processing temperature range of 100 to 600 ° C., although the amount of scraping was large. Similarly, it was confirmed that the chemical oxide film could be scraped off in the entire processing pressure range of “VAC” (0.2 Torr) to 400 Torr. In particular, even when the processing temperature is 100 ° C., the chemical oxide film can be scraped off when the processing pressure is “VAC” and the NH ₃ gas is rich. However, when the processing temperature is 100 ° C. and the processing pressure is 7.6 Torr or 400 Torr, and when the processing temperature is 300 ° C. and the processing pressure is “VAC”, the NH ₃ gas is not in a rich state, so the chemical The oxide film could not be removed. In addition, when the processing temperature was set to 50 ° C. lower than 100 ° C. and etching was performed with a mixed gas of HF gas and NH ₃ gas, the chemical oxide film was not scraped at all. Accordingly, the processing temperature needs to be 100 ° C. or higher.

Next, the selectivity between the chemical oxide film and polysilicon (silicon material) will be examined.
As is clear from FIG. 5, when polysilicon is processed at a processing temperature of 100 ° C., the processing pressure is 400 Torr, and when the processing temperature is 600 ° C., the processing pressure is large in a pressure range of “VAC” to 7.6 Torr. It has been scraped off. When the processing temperature is 300 ° C. and 400 ° C., the processing pressure is in the whole range of “VAC” to 400 Torr, and the flow rate ratio of HF gas to NH ₃ gas is in the whole range of 10: 1 to 1:10. The amount of polysilicon scraped is approximately “0”. Therefore, it is found that the chemical oxide film can be selectively scraped with respect to polysilicon when the processing temperature is in the range of 300 to 400 ° C.

Next, the selectivity between the chemical oxide film and the silicon nitride film is examined.
As is apparent from FIG. 5, the silicon nitride film has been scraped in the entire processing temperature range of 100 to 600 ° C., but when the processing temperature is 300 ° C. and the processing pressure is 7.6 Torr, the processing temperature When the processing pressure is “VAC” and 7.6 Torr at 400 ° C., when the processing temperature is 600 ° C. and the processing pressure is “VAC”, the scraping amount is smaller than the scraping amount of the chemical oxide film, respectively. Yes. Therefore, it is found that when the processing temperature is in the range of 300 to 600 ° C. and the processing pressure is 7.6 Torr or less, the chemical oxide film can be selectively scraped off from the silicon nitride film.

Next, the selectivity between the chemical oxide film and the silicon oxide film formed by TEOS will be described.
As is apparent from FIG. 5, the silicon oxide film formed by TEOS has been scraped in the entire processing temperature range of 100 to 600 ° C., but the processing temperature is 300 ° C. and the processing pressure is 7.6 Torr. In this case, when the processing temperature is 400 ° C. and the processing pressure is “VAC” and 7.6 Torr, the scraping amount is smaller than the scraping amount of the chemical oxide film. Therefore, it is found that when the processing temperature is in the range of 300 to 400 ° C. and the processing pressure is 7.6 Torr or less, the chemical oxide film can be selectively scraped with respect to the silicon oxide film formed by TEOS. .

Next, the selectivity between the chemical oxide film and the thermal oxide film (SiO ₂ ) formed by the thermal oxidation process will be described.
As is apparent from FIG. 5, the silicon oxide film formed by the thermal oxidation process has been scraped within the entire processing temperature range of 100 to 600 ° C., but at the processing temperature of 100 ° C., the processing pressure “VAC "In the case of a processing temperature of 300 ° C. and a processing pressure of 7.6 Torr, 150 Torr, 400 Torr (when NH _{3 is} rich), the processing temperature is 400 ° C. and the processing pressure is“ VAC ”to 400 Torr. Is 600 ° C. and the processing pressure is “VAC” and 7.6 Torr, the amount of scraping is smaller than that of the chemical oxide film, respectively. Therefore, it can be seen that the chemical oxide film can be selectively scraped with respect to the silicon oxide film formed by the thermal oxidation process within the entire processing temperature range of 100 to 600 ° C.

As is clear from FIG. 5, according to the mixed gas of HF gas and NH ₃ gas, not only the chemical oxide film but also the silicon oxide film formed from TEOS and the silicon oxide film formed by heat treatment are scraped off. Therefore, other silicon oxide films, for example, a natural oxide film formed on a silicon substrate, a silicon oxide film deposited by thermal CVD processing or plasma CVD processing, and the like can be scraped off.

Next, since the selective etching property at a flow rate ratio in which the NH ₃ gas is richer than the HF gas was examined, the evaluation result will be described.
FIG. 6 is a diagram showing selectivity data between a chemical oxide film and other silicon oxide films and silicon-containing materials, and FIG. 7 is a bar graph showing the data of FIG. 6, with respect to “TOP” and “BTM” data. Each is shown.
Here, the region richer in NH ₃ gas than in the case shown in FIG. 5 described above is examined. Specifically, the flow rate ratio of HF gas: NH ₃ gas is 1:10 to 1:50. This is done for a range of areas. Here, the processing temperature, processing pressure, and processing time are set to average values in the process conditions shown in FIG. 5, specifically, the processing temperature is 200 ° C., the processing pressure is 150 Torr, the processing Each time is set to 10 minutes. As for the process gas, NH ₃ gas is fixed at 1820 sccm, and the flow rate ratio of both gases is changed by changing the flow rate of the HF gas. The number of processed wafers is 150.

As apparent from FIGS. 6 and 7, even if the flow rate ratio of HF: NH ₃ is changed from 1:10 to 1:50, such as 1:10, 1:20, and 1:50, The etching amount (scraping amount) is almost zero and is hardly scraped. On the other hand, the etching amount of the chemical oxide film is stably shaved in the range of 0.41 to 0.57 nm. It was confirmed that the chemical oxide film can be selectively etched with respect to the polysilicon film in the entire range of the flow rate ratio.
Further, when the selective etching property between the chemical oxide film and the SiN film, the TEOS film, and the thermal oxide film is examined, the TEOS film is larger than the etching amount of the chemical oxide film at all flow rate ratios, and is etched intensely. The amount of etching gradually decreases as the degree of NH ₃ richness increases.

As for the SiN film and the thermal oxide film, when the HF: NH ₃ ratio is 1:10, the etching amounts of the SiN film and the thermal oxide film are both approximately equal to or larger than the etching amount of the chemical oxide film. Etched. However, when the HF: NH ₃ ratio is 1:20, the etching amounts of the SiN film and the thermal oxide film are both considerably smaller than the etching amount of the chemical oxide film. In particular, the HF: NH ₃ ratio is At 1:50, the etching amounts of the SiN film and the thermal oxide film are both substantially zero. As a result, in order to reduce the chemical oxide film as much as possible while suppressing the etching of the SiN film, the TEOS film, and the thermal oxide film, the NH ₃ gas should be made as rich as possible, and preferably the HF: NH ₃ ratio is increased. It was confirmed that it should be set within the range of 1:20 to 1:50.

In the example of the apparatus shown in FIG. 1, the case where the HF gas supply system 38 and the NH ₃ gas supply system 40 are provided as gas supply sources has been described as an example in order to facilitate understanding of the present invention. However, the present invention is not limited to this, and a continuous gas supply may be performed by providing a gas supply source required for other processes. As an example of this, FIG. 8 shows a block diagram of a processing apparatus provided with an oxidizing gas supply system for supplying water vapor or a gas for forming water vapor. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 8, here, in addition to the HF gas supply system 38 and the NH ₃ gas supply system 40, an oxidizing gas supply system 80 is provided as a gas supply source. Specifically, as the oxidizing gas supply system 80, an H ₂ gas source 80A and an O ₂ gas source 80B are provided, and gas flow paths in which the respective flow rate controllers 82A and 82B are interposed. The gas nozzles 86A and 86B can be introduced into the processing vessel 18 as necessary via the 84A and 84B.
By supplying H ₂ gas and O ₂ gas into the processing container 18 in this way, for example, these gases are combusted in the processing container 18 to generate water vapor, and thereby, for example, thermal oxidation is performed on the surface of the silicon substrate. A thermal oxide film can be formed by processing.

Therefore, according to this processing apparatus shown in FIG. 8, first, HF gas and NH ₃ gas are supplied to remove the chemical oxide film adhering to the wafer surface and supply of HF gas and NH ₃ gas. Next, a thermal oxidation process is performed by continuously supplying H ₂ gas and O ₂ gas to generate water vapor to form, for example, a thermal oxide film that becomes a gate oxide film. can do.
It is to be noted that an external combustion device for combusting H ₂ gas and O ₂ gas is provided as the oxidizing gas supply system 80, or water vapor generated using a water vapor generating device utilizing a catalyst is introduced into the processing vessel 18. It may be.

As another example, FIG. 9 shows a block diagram of a processing apparatus provided with a silicon film forming gas supply system for supplying a gas for forming a silicon film. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.
As shown in FIG. 9, here, in addition to the HF gas supply system 38 and the NH ₃ gas supply system 40, a gas supply system 90 for forming a silicon film is provided as a gas supply source. Specifically, as the silicon film forming gas supply system 90, a monosilane (SiH ₄ ) gas source 90A is provided, and this gas is supplied from a gas nozzle 96A through a gas flow path 94A in which a flow rate controller 92A is interposed. It can be introduced into the processing vessel 18 as required.
At the same time, for example, a monogermal (GeH ₄ ) gas source 90B is provided as a dopant gas source in order to introduce a dopant (impurity), and this gas is supplied to a gas nozzle 94B through a gas flow path 94B provided with a flow rate controller 92B. 96B can be introduced into the processing vessel 18 as required.

Thus, by supplying monosilane and monogermale into the processing container 18, a silicon film (polysilicon film) into which germanium is introduced as a dopant can be formed.
Therefore, according to this processing apparatus shown in FIG. 9, first, HF gas and NH ₃ gas are supplied to perform removal processing of the chemical oxide film adhering to the wafer surface, and supply of HF gas and NH ₃ gas. Then, a silicon film in which germanium is introduced as an impurity can be continuously formed by continuously supplying monosilane gas and monogermal gas. In this case, an epitaxial film doped with germanium can also be formed by appropriately selecting the temperature. Further, by combining the apparatus configurations shown in FIGS. 8 and 9, it is possible to form an apparatus configuration capable of continuously processing the formation of the gate oxide film and the formation of the silicon gate electrode after the chemical oxide film removal process.

In this example, the case where a thermal oxide film or a silicon film into which germanium is introduced is continuously formed after the chemical oxide film is removed has been described as an example. However, after the chemical oxide film is removed, a metal film, a nitride film, or another film is formed. An insulating film may be formed. In this case, as described above, instead of the chemical oxide film, for example, the natural oxide film may be removed by the method of the present invention as described above, and then the above-described continuous treatment may be performed.
In the above embodiment, the processing apparatus having a double-pipe structure has been described as an example. However, this is merely an example. For example, the present invention can be applied to a processing apparatus having a single-pipe structure. Each gas is introduced from below or above the processing vessel, and the inside of the processing vessel is evacuated from above or below.

Further, the method of the present invention is not limited to the batch type processing apparatus that can oxidize a large number of semiconductor wafers at a time as described above. As a means, the present invention can also be applied to a single-wafer processing apparatus that performs oxidation processing one by one by lamp heating or heater heating.
Further, the object to be processed is not limited to a semiconductor wafer, and can be applied to an LCD substrate, a glass substrate, and the like.

It is a block diagram which shows an example of the processing apparatus for enforcing the removal method of the silicon oxide film which concerns on this invention. It is process drawing which shows a part of process process of a semiconductor wafer. It is a graph which shows the change of the film thickness of the chemical oxide film before and behind an etching process. Is a graph showing the NH ₃ gas dependence wear amount of the chemical oxide film. It is a figure which shows the data of the presence or absence of the selectivity of a chemical oxide film, a silicon oxide film other than this, and a silicon containing material. It is a figure which shows the selectivity data of a chemical oxide film and other silicon oxide films and silicon-containing materials. FIG. 7 is a bar graph showing the data of FIG. 6 and shows the data of “TOP” and “BTM”, respectively. It is a block diagram which shows the processing apparatus which provided the gas supply system for oxidation which supplies the gas for forming water vapor and water vapor | steam. It is a block diagram which shows the processing apparatus which provided the gas supply system for silicon film formation which supplies the gas for silicon film formation. It is a figure which shows a series of process steps of the surface of a semiconductor wafer.

Explanation of symbols

2 Natural oxide film 4 Chemical oxide film 6 Thermal oxide film 12 Processing equipment 18 Processing container 20 Wafer boat (support shelf)
38 HF gas supply system 40 NH ₃ gas supply system 48 HF gas source 56 NH ₃ gas source 68 heater (heating means)
80 Gas supply system for oxidation 90 Gas supply system for silicon film formation W Semiconductor wafer (object to be processed)

Claims (4)

A silicon oxide film formed on the surface of an object to be processed in a processing container that can be evacuated, and formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the removal method for removing the chemical oxide film,
While using a mixed gas of HF gas and NH ₃ gas, the processing temperature is set in the range of 200 ° C. to 400 ° C. in order to obtain the selectivity of the chemical oxide film with respect to the silicon material,
The processing pressure is set in the range of 26 Pa (0.2 Torr) to 53200 Pa (400 Torr), and the flow rate ratio of the HF gas to NH ₃ gas is set in the range of 10: 1 to 1:50. A method for removing a chemical oxide film, wherein the chemical oxide film is removed. A silicon oxide film formed on the surface of an object to be processed in a processing container that can be evacuated, and formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the removal method for removing the chemical oxide film,
While using a mixed gas of HF gas and NH ₃ gas, the processing temperature is set in the range of 200 ° C. to 600 ° C. in order to obtain the selectivity of the chemical oxide film with respect to the silicon nitride film,
The processing pressure is set to 53200 Pa (400 Torr) or lower, and the flow rate ratio of the HF gas to NH ₃ gas is set within the range of 1:10 to 1:50 to remove the chemical oxide film. A method for removing a chemical oxide film characterized by the following. A silicon oxide film formed on the surface of an object to be processed in a processing container that can be evacuated, and formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the removal method for removing the chemical oxide film,
In order to obtain the selectivity of the chemical oxide film with respect to the silicon oxide film formed by CVD (Chemical Vapor Deposition) using a mixed gas of HF gas and NH ₃ gas, the processing temperature is in the range of 200 ° C. to 400 ° C. Set to
The processing pressure is set to 53200 Pa (400 Torr) or lower, and the flow rate ratio of the HF gas to NH ₃ gas is set within the range of 1:10 to 1:50 to remove the chemical oxide film. A method for removing a chemical oxide film characterized by the following. A silicon oxide film formed on the surface of an object to be processed in a processing container that can be evacuated, and formed by chemical treatment using a mixed solution of H ₂ O ₂ and NH ₄ OH. In the removal method for removing the chemical oxide film,
While using a mixed gas of HF gas and NH ₃ gas, in order to obtain the selectivity of the chemical oxide film with respect to the thermal oxide film, the processing temperature is set within a range of 100 ° C. to 600 ° C.,
The processing pressure is set to 53200 Pa (400 Torr) or lower, and the flow rate ratio of the HF gas to NH ₃ gas is set within the range of 1:10 to 1:50 to remove the chemical oxide film. dividing removed by the method of chemical oxide film according to claim.

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