JPH0927457A - Thin film depositing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the effective removal of surface contaminants and facilitate the removal of a silicon oxide film formed in areas where it should not exist, by, while applying oxidizing gas to the surface of a workpiece, burning and removing surface contaminating organic substances, and thereafter, while supplying reducing gas, performing heat treatment. SOLUTION: After a wafer substrate 10 is placed in a CVD furnace, the interior of the CVD furnace is evacuated and put under reduced pressure. Oxygen, an oxidizing gas, is introduced to burn and remove organic substances 12 on the surface of the wafer substrate 10. As the result of the combustion and removal of the organic substances, a silicon oxide film 11a is formed on the surface of the wafer substrate 10 positioned at the bottom of a contact hole. Nitrogen gas is substituted for the gas in the CVD furnace. Thereafter, hydrogen gas is introduced into the CVD furnace to chemically reduce and remove the silicon oxide film 11a. This makes it possible to remove the contaminating organic substances 12 from the surface of the wafer substrate 10 under processing, and allows no silicon oxide layer 11a to be present on the surface of the wafer substrate 10 at the bottom of the contact hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film deposition method used, for example, in the manufacturing process of a semiconductor device, and more specifically, to effectively remove surface contaminants and to oxidize oxides formed in unnecessary portions. The present invention relates to a thin film deposition method capable of easily removing a silicon film.

[0002]

2. Description of the Related Art In recent years, as semiconductor integrated circuits have become highly integrated, MOS LSI gate oxide films and flash (Flash)
It is becoming increasingly important to improve the reliability of the thin silicon oxide film used as the tunnel oxide film of memory, and the thin silicon nitride film used as the capacitor insulating film of DRAM and the intermediate insulating film of Flash memory. .
The factors that reduce the reliability of these thin silicon oxide films and nitride films are not single, but are complex, such as defects in the film and heavy metal contamination, but recently, the influence of organic substances adsorbed on the wafer surface from within a clean room environment has been Attention has been paid. The organic matter adsorbed on the wafer surface has been proved to be dioctyl phthalate (DOP) by the evaluation study by Shimazaki et al. (1994 Spring Applied Physics Society 28a-ZQ-2, 28A-ZQ-4).
The correlation between the amount of organic substances adsorbed on the wafer surface and the withstand voltage of the silicon oxide film was also quantified by Shimazaki et al. (Spring Society of Applied Physics 1992 30a-ZF-6). However, DOP as an organic substance and the mechanism of deterioration in breakdown voltage of the silicon oxide film have not been clarified.

As a means for effectively removing the organic DOP adsorbed on the wafer surface from the wafer surface, a combustion removal method using an oxidizing gas has been proposed by the applicant.

[0004]

However, in this method, when the surface of the substrate to be processed is silicon, the silicon is oxidized, and it is desired to form a thin silicon nitride film used as a capacitor insulating film of DRAM, for example, on the silicon surface. In this case, the formation of the silicon oxide film may reduce the capacitance of the capacitor. In addition, if the above-described combustion removal method is used before the step of electrically connecting the silicon substrate and the polysilicon, there is a possibility that a problem that the joining resistance is significantly increased may occur.

What kind of process actually causes such a problem of the prior art will be described with reference to the drawings by taking a low pressure chemical vapor deposition (hereinafter referred to as CVD) method as an example. . FIG. 6 shows an example of a conventional low pressure CVD furnace process sequence in consideration of organic matter combustion. The processing steps based on this are shown below.

The wafer substrate is mounted on a quartz boat and introduced into the inner tube. At this time, the temperature in the furnace is the same as the temperature at the time of introducing the oxidizing gas next. This temperature is the minimum temperature at which organic substances can burn, and is a temperature at which the wafer substrate is not excessively oxidized.

After the introduction of the wafer substrate into the inner tube, the inside of the CVD furnace is evacuated, and then oxygen, which is an oxidizing gas, is introduced into the CVD furnace through the gas introduction port to burn and remove organic substances. After the combustion removal treatment with the oxidizing gas, the inside of the CVD reaction furnace is evacuated again, and then the atmosphere in the furnace is replaced with nitrogen. This is a gas in which monosilane (SiH ₄ ) and disilane (Si ₂ H ₆ ) used as a CVD gas are extremely chemically active, and these easily react with an oxidizing gas to generate particles of silicon oxide. This is to prevent it.

After that, thin film deposition is performed by CVD, then vacuum exhaust is performed, nitrogen substitution in the furnace is performed for the same reason as above, and the wafer is unloaded. FIG. 7 shows another example of the low pressure CVD furnace process sequence in consideration of the combustion of organic substances.

The wafer substrate is mounted on a quartz boat and introduced into the inner tube. At this time, the furnace atmosphere is filled with an oxidizing gas containing oxygen. The furnace temperature is the minimum temperature at which organic substances (carbides) can be burned and the wafer substrate is not excessively oxidized.

After the burning and removing treatment with the oxidizing gas, the chamber is evacuated and then the atmosphere in the CVD reactor is replaced with nitrogen. This is because monosilane and disilane used as the CVD gas are extremely chemically active gases and do not react with the oxidizing gas to generate particles of silicon oxide.

After the surface treatment of the substrate with an oxidizing gas, thin film deposition CVD is performed. However, if the thin film deposition CVD is carried out immediately after the organic substance combustion removal treatment by the oxidizing gas according to the process sequence of the above-mentioned two examples, the following problems occur.

First, the case of depositing a polysilicon film in the above sequence will be described. As shown in FIG. 8, it is assumed that there is a silicon oxide film 11a on the wafer substrate 10 and a contact hole is opened in the silicon oxide film 11a to electrically connect the wafer substrate 10 and the polysilicon 13. Contaminated organic substances 12 due to the clean room environment may be present on the wafer substrate in which this hole is opened. In the conventional low-pressure polysilicon CVD furnace process sequence considering the combustion of organic matter, an oxidizing gas is introduced near the wafer substrate 10 in order to oxidize and burn the organic matter 12. On this occasion,
The organic substances 12 are burned and removed, but at the same time, the surface of the wafer substrate 10 where the holes are opened is also oxidized. Therefore, as shown in FIG. 8B, a silicon oxide film is formed on the silicon surface at the bottom of the holes. 11 had been formed. Therefore, by the subsequent CVD of polysilicon,
The polysilicon 13 was formed on the silicon oxide film 11. Therefore, the wafer substrate 10 and the polysilicon 1
There was a problem that the electrical junction resistance with 3 increased.

Next, the case of depositing a silicon nitride film for a DRAM capacitor by the above sequence will be described. As shown in FIG. 9, when a DRAM capacitor is formed, a silicon oxide film 11a is formed on the wafer substrate 10, and a contact hole is formed in the silicon oxide film 11a to electrically connect the wafer substrate 10 and the polysilicon 13. Is opened, and polysilicon 13 is laminated thereon as a capacitor lower electrode. As shown in FIG. 9A, a polluted organic substance 12 from the clean room environment may be present on the polysilicon 13 that will be the lower electrode of the capacitor. In the conventional silicon nitride film CVD process sequence considering the combustion of organic matter, an oxidizing gas is introduced near the wafer substrate 10 in order to oxidize and burn the organic matter 12. At this time, the organic matter 12 is burned and removed, but at the same time, the surface of the polysilicon 13 that will be the lower electrode of the capacitor is also oxidized, so that the polysilicon 13 that will be the lower electrode of the capacitor will be oxidized as shown in FIG. 9B. The silicon oxide film 11 is formed on top. Therefore, the silicon nitride film 14 has been formed on the silicon oxide film 11 by the subsequent CVD. Therefore, there is a problem that the capacity of the DRAM capacitor is reduced.

The present invention has been made in view of the above circumstances, and provides a thin film deposition method capable of effectively removing surface contaminants and easily removing a silicon oxide film formed in an unnecessary portion. The purpose is to provide.

[0015]

In order to achieve the above object, a thin film deposition method according to the present invention comprises a first heat treatment for burning and removing surface contaminated organic substances while supplying an oxidizing gas to the surface of the object to be treated, A second heat treatment for performing heat treatment while supplying a reducing gas, and thin film deposition is performed after these heat treatments.

In the first heat treatment, the object temperature is 200 °
It is preferable to perform the treatment in the temperature range of not lower than C and not higher than 900 ° C. In the second heat treatment, it is preferable to perform the treatment in a temperature range of the object temperature of 800 ° C. or higher.

After the second heat treatment, for example, a silicon nitride film, a polysilicon film or an amorphous silicon film is formed. The oxidizing gas used in the first heat treatment preferably contains any of oxygen, ozone, nitrous oxide, and water vapor.

The reducing gas used in the second heat treatment preferably contains hydrogen. The thin film deposition method is preferably a low pressure chemical vapor deposition method. It is preferable to manufacture a semiconductor device using the thin film deposition method according to the present invention.

[0019]

According to the CVD thin film forming method of the present invention, by burning and removing the organic substances by the oxidizing gas, it is possible to prevent the deterioration of the device characteristics due to the remaining organic substances. In addition, according to the present invention, the oxide film layer, which is considered to be generated when the organic substance is burned off by the oxidizing gas, is removed by introducing the reducing gas, so that a stable and high-quality CVD thin film can be deposited. As a result, it is possible to prevent an increase in electrical junction resistance between the semiconductor layer and the polysilicon film wiring, and to prevent the capacitance of the DRAM capacitor from decreasing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A low pressure CVD thin film forming method according to an embodiment of the present invention will be described in detail below with reference to the drawings. First, prior to describing each example, the low pressure CVD used in each example.
The device will be described.

FIG. 5 is a schematic sectional view of a vertical low pressure CVD apparatus. The low pressure CVD furnace is composed of an outer tube 1 and an inner tube 2, and a wafer substrate is a quartz boat 3.
And is introduced into the inner tube 2. The outer tube 1 is airtightly connected to the upper flange 4 of the lower tube 20, and the lower flange 21 of the lower tube 20 is airtightly connected to the furnace cap 6. A boat table 8 is installed on the furnace port cap 6. The exhaust tube 5 is connected to the lower tube 20 in an airtight manner. An exhaust port 7 is formed in the exhaust pipe 5. A gas introducing pipe 9 is attached to the lower tube 20, and various gases are introduced into the CVD furnace from there.

After the quartz board on which the wafer substrate is installed is introduced into the CVD furnace, the atmosphere in the CVD reaction furnace is evacuated from the exhaust port 7 to keep the inside of the CVD reaction furnace under reduced pressure. Example 1 This example is an example of forming a polysilicon film by a low pressure CVD process using the method of the present invention.

FIG. 1 shows a reduced pressure CV according to an embodiment of the present invention.
3 shows a process sequence of D. FIG. 2 is a cross-sectional view of a principal part in each step of a polysilicon CVD process performed for obtaining electrical connection with a silicon substrate surface. FIG.
As shown in (a), in a semiconductor device manufacturing process, a wafer substrate 10 composed of a silicon substrate or the like is used.
Oxide film 11 for electrical connection with the surface of
The step of forming a contact hole in a is required. This contact hole is formed by a plasma etching apparatus that performs RIE or the like. When the wafer substrate 10 is carried out of the etching apparatus to the outside of the apparatus, the surface of the wafer substrate is contaminated directly from the clean room environment or indirectly from the transport cassette or the like, and as shown in FIG. Contaminated organic matter 12 may be present on the surface.

The surface of the wafer substrate having such a surface state is then subjected to low pressure CVD according to the sequence shown in FIG.
Thus, a polysilicon film is formed. In step S ₁ shown in FIG. 1, the wafer substrate 10 is mounted on the quartz boat 3 shown in FIG. 5 and introduced into the inner tube 2. At this time, the temperature inside the furnace is set to be the same as the temperature when the oxidizing gas is introduced into the CVD reaction furnace through the inlet in step S ₃ . This temperature is the minimum temperature for the organic substance (hydrocarbon) to burn, and is optimal near 400 ° C to 500 ° C, which is the temperature at which the wafer substrate is hard to be oxidized.

The atmosphere in the CVD furnace and in the vicinity of the furnace in step S ₁ is preferably a nitrogen atmosphere in order to suppress the formation of unnecessary natural oxide film on the wafer substrate 10. Further, it is desirable to provide a load lock chamber and reduce the pressure (about 1 Pa).

After introducing the wafer substrate, in step S ₂ , the inside of the CVD furnace is evacuated to a depressurized state. next,
In step S ₃ , oxygen as an oxidizing gas is supplied to
The gas is introduced into the CVD furnace from the gas inlet 9 shown in FIG. 1 to burn off the organic matter 12 on the surface of the wafer substrate. The optimum conditions at this time are an oxygen flow rate of 500 sccm, a pressure of 1.0 Torr, and a time of about 5 minutes. It was confirmed by the experiments of the present inventors that the organic substances on the surface of the wafer substrate are removed under the conditions by the combustion removal of the organic substances in step S ₃ . By this combustion removal, a silicon oxide film having a thickness of about 1.5 to 2.0 nm is formed on the surface of the wafer substrate located at the bottom of the contact hole. In this example, the silicon oxide film is removed by performing the following steps.

In step S ₄ , the inside of the CVD furnace is evacuated again, and in step S ₅ , the inside of the CVD furnace is replaced with nitrogen gas to completely remove the oxidizing gas atmosphere. During the nitrogen substitution process of step S ₅ , the temperature inside the CVD furnace is gradually raised and stabilized after reaching 850 ° C. Furnace temperature 85
While maintaining 0 ° C., next, in step S ₆ , hydrogen gas is introduced into the CVD furnace at a flow rate of 500 sccm and a pressure of 0.5 Torr for 3 minutes to chemically reduce and remove the silicon oxide film. By adding process in step S _6, be a silicon oxide film produced by the heat treatment in the oxidizing atmosphere is removed,
It has been confirmed by the applicant's experiment.

Next, in step S ₇ , the inside of the CVD furnace is replaced with nitrogen gas again to remove the hydrogen gas atmosphere. During the nitrogen gas replacement process of step S ₇ , the temperature inside the CVD furnace is gradually lowered and stabilized after reaching 630 ° C. As a result of the processes S ₁ to S ₇ , as shown in FIG. 2B, the contaminating organic substances 12 can be removed from the surface of the wafer substrate to be processed, and silicon oxide is formed on the surface of the wafer substrate at the bottom of the contact hole. The layer does not exist.

Next, in step S ₈ , monosilane gas is introduced into the CVD furnace at a flow rate of 150 sccm and a pressure of 0.3 Torr to deposit a polysilicon film 13 on the wafer substrate 10 as shown in FIG. 2C. Let As a result, the polysilicon film 13 can be stably bonded to the surface of the underlying wafer substrate 10 with low resistance in the contact hole.

Example 2 This example is an example of forming a silicon nitride film by a low pressure CVD process using the method of the present invention. FIG. 3 is a chart showing the process sequence of this embodiment.
FIG. 4 is a cross-sectional view of a principal part in each step of a silicon nitride CVD process performed for manufacturing a DRAM capacitor.

As shown in FIG. 4A, in the process of manufacturing a DRAM as a semiconductor device, a silicon oxide film 11a is formed on the surface of the wafer substrate 10, and a contact hole is formed in the silicon oxide film 11a. The step of forming the polysilicon film 13a to be the lower electrode of the capacitor is required so as to be embedded in the contact hole. After depositing the polysilicon film, the wafer substrate 10 may be stored in a transport cassette and stored or transported in a clean room environment. that time,
The surface of the wafer substrate may be contaminated directly from the clean room environment or indirectly from a transport cassette or the like, and contaminated organic substances 12 may be present on the surface as shown in FIG. 4A.

The surface of the wafer substrate having such a surface state is then subjected to low pressure CVD according to the sequence shown in FIG.
Thus, a silicon nitride film is formed. First, step S ₁
In, the wafer substrate 10 is mounted on the quartz boat 3 shown in FIG. 5 and introduced into the inner tube 2. At this time, the atmosphere in the furnace is filled with an oxidizing gas containing oxygen. The oxygen concentration at this time is preferably high, including controllability. This can be achieved by introducing an oxidizing gas containing oxygen from the gas inlet 9 in FIG. Alternatively, a pipe for introducing an oxidizing gas containing oxygen gas may be installed in the exhaust port 7, and the supply amount thereof may be set so that the inside of the furnace has a positive pressure rather than the atmospheric pressure.

The temperature inside the furnace when the wafer substrate 10 is mounted on the quartz board 3 and introduced into the inner tube 2 is the minimum temperature for the organic substances (hydrocarbons) to burn, and the wafer substrate is oxidized. 400 °, which is the temperature
The optimum temperature is around C to 500 ° C. Also step S ₁
Then, it is preferable to hold the wafer substrates 10 for about 5 minutes after all the wafer substrates 10 have been put into the furnace.

Next, in step S ₂ , the inside of the CVD furnace is decompressed by evacuating, and then in step S ₃ , the inside of the CVD furnace is replaced with nitrogen gas to remove the oxidizing gas atmosphere. During the nitrogen gas replacement process in step S ₃ , the temperature inside the CVD furnace is gradually raised and stabilized after reaching 850 ° C.

With the furnace temperature kept at 850 ° C., hydrogen gas is fed into the CVD furnace in step S ₄ at a flow rate of 500 sccm and a pressure of 0.5 T.
It is introduced for 3 minutes under the condition of orr, and the silicon oxide film considered to be generated by the heat treatment in the oxidizing gas atmosphere is chemically reduced and removed. In step S ₅ , the inside of the CVD furnace is replaced with nitrogen gas again to remove the hydrogen gas atmosphere. During the nitrogen gas replacement process of step S ₅ , the temperature inside the CVD furnace is gradually lowered and stabilized after reaching 630 ° C. process
As a result of S ₁ to S ₅ , as shown in FIG. 4B, the contaminating organic substance 12 can be removed from the surface of the polysilicon film 13a, and a silicon oxide layer does not exist on the surface.

Next, in step S ₆ , SiH ₂ Cl ₂ gas has a flow rate of 50 sccm, NH 3 gas has a flow rate of 500 sccm, and the total pressure is 0.6 Torr.
It is introduced into the CVD furnace under the condition of r, and the silicon nitride film 14 is deposited on the polysilicon film 13a as shown in FIG. 4 (c). By this processing, a stable silicon nitride film 14 having a high dielectric constant can be formed on the polysilicon film 13a without a silicon oxide film interposed therebetween.

On the silicon nitride film 14, a polysilicon film 13b to be the upper electrode of the capacitor is formed. In this embodiment, the silicon nitride film serving as the capacitor insulating film of the DRAM can be thinly formed, and the capacitance of the DRAM capacitor is improved.

Embodiment 3 Same as Embodiment 1 except that amorphous silicon is formed by low pressure CVD by performing the process steps after step S ₇ shown in FIG. Then, the connection was made through the contact hole.

In step S ₇ , the inside of the CVD furnace is replaced with nitrogen gas and the hydrogen gas atmosphere is removed. During this nitrogen gas replacement treatment, the temperature inside the CVD furnace was gradually lowered to 520 °.
Stabilize after reaching C. In step S ₈ , monosilane gas is introduced into the CVD furnace at a flow rate of 150 sccm and a pressure of 1.0 Torr to form an amorphous silicon film on the wafer substrate 1.
0 deposit.

Example 4 In Example 1, the process sequence shown in FIG. 3 was used instead of the process sequence shown in FIG.
Connection with contact holes was performed in the same manner as in Example 1 except that the polysilicon film was formed by low pressure CVD.

That is, first, in step S ₁ , the wafer substrate 10 is mounted on the quartz boat 3 shown in FIG. 5 and introduced into the inner tube 2. At this time, the atmosphere in the furnace is filled with an oxidizing gas containing oxygen. The oxygen concentration at this time is preferably high, including controllability. This can be achieved by introducing an oxidizing gas containing oxygen from the gas inlet 9 in FIG. Alternatively, a pipe for introducing an oxidizing gas containing oxygen gas may be installed in the exhaust port 7, and the supply amount thereof may be set so that the inside of the furnace has a positive pressure rather than the atmospheric pressure.

The temperature in the furnace when the wafer substrate 10 is mounted on the quartz board 3 and introduced into the inner tube 2 is the minimum temperature for the organic substance (hydrocarbon) to burn, and the wafer substrate is oxidized. 400 °, which is the temperature
The optimum temperature is around C to 500 ° C. Also step S ₁
Then, it is preferable to hold the wafer substrates 10 for about 5 minutes after all the wafer substrates 10 have been put into the furnace.

Next, in step S ₂ , the inside of the CVD furnace is evacuated and placed under reduced pressure, and then in step S ₃ , the inside of the CVD furnace is replaced with nitrogen gas to remove the oxidizing gas atmosphere. During the nitrogen gas replacement process in step S ₃ , the temperature inside the CVD furnace is gradually raised and stabilized after reaching 850 ° C.

With the furnace temperature kept at 850 ° C., hydrogen gas is fed into the CVD furnace in step S ₄ at a flow rate of 500 sccm and a pressure of 0.5 T.
It is introduced for 3 minutes under the condition of orr, and the silicon oxide film considered to be generated by the heat treatment in the oxidizing gas atmosphere is chemically reduced and removed. In step S ₅ , the inside of the CVD furnace is replaced with nitrogen gas again to remove the hydrogen gas atmosphere. During the nitrogen gas replacement process of step S ₅ , the temperature inside the CVD furnace is gradually lowered and stabilized after reaching 630 ° C. process
As a result of S ₁ to S ₅ , as shown in FIG. 2B, the contaminating organic substance 12 can be removed, and the silicon oxide layer does not exist on the surface of the wafer substrate at the bottom of the contact hole.

Next, in step S ₆ , monosilane gas is introduced into the CVD furnace under the conditions of a flow rate of 150 sccm and a pressure of 0.3 Torr, and as shown in FIG.
3 is deposited on the wafer substrate 10. As a result, the polysilicon film 13 can be stably bonded to the surface of the underlying wafer substrate 10 with low resistance in the contact hole.

Example 5 In Example 2, the process sequence shown in FIG. 1 was used instead of the process sequence shown in FIG.
A DRAM capacitor was formed in the same manner as in Example 2 except that the silicon nitride film was formed by low pressure CVD.

That is, first, step S ₁ shown in FIG.
At this point, the wafer substrate 10 is mounted on the quartz boat 3 shown in FIG. 5 and introduced into the inner tube 2. The temperature in the furnace at this time is C in the step S ₃ where the oxidizing gas is introduced from the inlet.
The temperature is the same as the temperature at which it is introduced into the VD reaction furnace. This temperature is the minimum temperature for the organic substance (hydrocarbon) to burn, and is optimal near 400 ° C to 500 ° C, which is the temperature at which the wafer substrate is hard to be oxidized.

The atmosphere in the CVD furnace and in the vicinity of the furnace in step S ₁ is preferably a nitrogen atmosphere in order to suppress the formation of unnecessary natural oxide film on the wafer substrate 10. Further, it is desirable to provide a load lock chamber and reduce the pressure (about 1 Pa).

After introducing the wafer substrate, in step S ₂ , the inside of the CVD furnace is evacuated to a depressurized state. next,
In step S ₃ , oxygen as an oxidizing gas is supplied to
The gas is introduced into the CVD furnace from the gas inlet 9 shown in FIG. 1 to burn off the organic matter 12 on the surface of the wafer substrate. The optimum conditions at this time are an oxygen flow rate of 500 sccm, a pressure of 1.0 Torr, and a time of about 5 minutes. It was confirmed by the experiments of the present inventors that the organic substances on the surface of the wafer substrate are removed under the conditions by the combustion removal of the organic substances in step S ₃ .

In step S ₄ , the inside of the CVD furnace is evacuated again, and in step S ₅ , the inside of the CVD furnace is replaced with nitrogen gas to completely remove the oxidizing gas atmosphere. During the nitrogen substitution process of step S ₅ , the temperature inside the CVD furnace is gradually raised and stabilized after reaching 850 ° C.

With the furnace temperature kept at 850 ° C., next, in step S ₆ , hydrogen gas is flown into the CVD furnace at a flow rate of 500 scc.
It is introduced for 3 minutes under the conditions of m and a pressure of 0.5 Torr to chemically reduce and remove the silicon oxide film. This step by adding the step of S _6, the silicon oxide film produced by the heat treatment in the oxidizing atmosphere is removed, it has been confirmed by the applicant of the experiment.

Next, in step S ₇ , the inside of the CVD furnace is replaced with nitrogen gas again to remove the hydrogen gas atmosphere. During the nitrogen gas replacement process of step S ₇ , the temperature inside the CVD furnace is gradually lowered and stabilized after reaching 630 ° C. As a result of the processes S ₁ to S _7, from the surface of the wafer substrate to be processed, as shown in FIG.
The contaminated organic substance 12 can be removed from the surface of, and a silicon oxide layer does not exist on the surface.

Next, in step S ₈ , monosilane gas is introduced into the CVD furnace under the conditions of a flow rate of 150 sccm and a pressure of 0.3 Torr, and as shown in FIG. 4C, the silicon nitride film 14 is formed on the polysilicon film 13a. Deposit. By this process, a stable silicon nitride film 14 having a high dielectric constant is formed without using a silicon oxide film therebetween.
Can be formed on

On the silicon nitride film 14, a polysilicon film 13b to be the upper electrode of the capacitor is formed. In this embodiment, the silicon nitride film serving as the capacitor insulating film of the DRAM can be thinly formed, and the capacitance of the DRAM capacitor is improved.

Embodiment 6 In Embodiment 2 or 5, except that the process steps from S ₄ (FIG. 1) onward in Embodiment 5 and S ₂ (FIG. 3) onwards in Embodiment 2 are performed as follows. A DRAM capacitor was manufactured in the same manner as in the example.

That is, in step S ₄ (S ₂ ) CVD
Place inside the furnace under reduced pressure by evacuating the furnace and step
At S ₅ (S ₃ ), the inside of the CVD furnace is replaced with NH ₃ gas to remove the oxidizing gas atmosphere. A proper NH ₃ gas flow rate is about 500 sccm. During this NH ₃ gas replacement treatment, the temperature inside the CVD furnace is gradually raised and stabilized after reaching 850 ° C.

With the furnace temperature kept at 850 ° C., hydrogen gas was introduced into the CVD furnace in step S ₆ (S ₄ ) at a flow rate of 500 sccm and a pressure of 0.5 Torr for 3 minutes to chemically reduce and remove the oxide layer. To do. At step S ₇ (S ₅ )
Replace with ₃ gas and remove hydrogen gas atmosphere. A proper NH ₃ gas flow rate is about 500 sccm. During this NH ₃ gas replacement treatment, the temperature inside the CVD furnace is gradually lowered and stabilized after reaching 700 ° C.

As a result of up to the process S ₇ (S ₅ ), as shown in FIG. 4B, the contaminated organic substances 12 can be removed from the surface of the polysilicon film 13a, and a silicon oxide layer exists on the surface. It becomes a state not to do. Next, in step S ₆ , SiH ₂ Cl ₂ gas flow rate is 50 sccm and NH 3 gas flow rate is 50 sccm.
Introduced into the CVD furnace under the conditions of 0 sccm and total pressure of 0.6 Torr,
As shown in FIG. 4C, the silicon nitride film 14 is deposited on the polysilicon film 13a. By this processing, a stable silicon nitride film 14 having a high dielectric constant can be formed on the polysilicon film 13a without a silicon oxide film interposed therebetween.

On the silicon nitride film 14, a polysilicon film 13b to be the upper electrode of the capacitor is formed. In this embodiment, the silicon nitride film serving as the capacitor insulating film of the DRAM can be thinly formed, and the capacitance of the DRAM capacitor is improved.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention. For example, various modifications can be made within the scope of the present invention by combining the above embodiments.

[0061]

As described above, according to the present invention, an organic substance adhering to the wafer surface can be effectively removed from a clean room environment, and a silicon oxide film formed for removing an organic substance can be easily removed. It can be removed by the method, and the film quality of the silicon nitride film for insulating the DRAM capacitor can be improved without adding a special number of pretreatment steps. Further, it is possible to reduce and stabilize the electrical junction resistance between the wiring layer such as polysilicon and amorphous silicon and the semiconductor layer. As a result, the IC yield can be improved and the reliability of the element can be improved.

[Brief description of drawings]

FIG. 1 is a chart showing a process sequence of a low pressure CVD furnace according to an embodiment of the present invention.

FIG. 2A to FIG. 2C are cross-sectional views of essential parts showing a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a low pressure CVD in another embodiment of the present invention.
It is a chart figure which shows the process sequence of a furnace.

FIG. 4A to FIG. 4C are cross-sectional views of essential parts showing a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 5 is a sectional view of a vertical reduced pressure CVD furnace.

FIG. 6 is a chart showing a process sequence of a low-pressure CVD furnace according to a conventional technique.

FIG. 7 is a chart showing a process sequence of a low pressure CVD furnace according to another conventional technique.

8 (a) and 8 (b) are cross-sectional views of essential parts showing a process of manufacturing a semiconductor device according to a conventional technique.

FIGS. 9A to 9C are cross-sectional views of main parts showing a process of manufacturing a semiconductor device according to another conventional technique.

[Explanation of symbols]

 1 ... Outer tube 2 ... Inner tube 3 ... Quartz boat 4 ... Flange 5 ... Vacuum exhaust pipe 6 ... Furnace port cap 7 ... Vacuum exhaust port 8 ... Boat stand 9 ... Gas inlet port 10 ... Silicon substrate 11, 11a ... Silicon oxide film 12 ... Organic matter 13 ... Polysilicon 14 ... Silicon nitride film

Claims (9)

[Claims] 1. A method for depositing a thin film on the surface of an object to be processed, comprising a first heat treatment for burning and removing surface polluted organic substances while supplying an oxidizing gas to the surface of the object to be treated, and a heat treatment for supplying a reducing gas. A second heat treatment to be performed, and thin film deposition is performed after these heat treatments. 2. In the first heat treatment, the temperature of the object to be treated is 200
The thin film volume method according to claim 1, wherein the treatment is performed in a temperature range of not less than ° C and not more than 900 ° C. 3. In the second heat treatment, the temperature of the object to be processed is 800
The thin film volume method according to claim 1 or 2, wherein the treatment is performed in a temperature range of ° C or higher. 4. The thin film deposition method according to claim 1, wherein a silicon nitride film is formed after the second heat treatment. 5. The thin film deposition method according to claim 1, wherein a polysilicon film or an amorphous silicon film is formed after the second heat treatment. 6. The thin film deposition method according to claim 1, wherein the oxidizing gas used in the first heat treatment contains any one of oxygen, ozone, nitrous oxide, and water vapor. . 7. The thin film deposition method according to claim 1, wherein the reducing gas used in the second heat treatment contains hydrogen. 8. The thin film deposition method according to claim 1, wherein the thin film deposition method is a low pressure chemical vapor phase thin film deposition method. 9. A semiconductor device manufacturing method for manufacturing a semiconductor device using the thin film deposition method according to claim 1. Description: