JPH06181205A - Method of manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To grow CVD oxide films of high quality by low temperature processing at a high film growth rate by depositing the oxide film using the reaction gases of hydrazine, nitrogen oxide, and silanes. CONSTITUTION:With a wafer W placed on the susceptor 4, the pressure inside a reaction chamber 2 is maintained at 3Torr by exhausting the gas inside the reaction chamber 2 via an exhaust pipe 7 while introducing into the reaction chamber 2 via the gas inlet pipe 3 disilane gas (Si2H6) at a flow rate of 3sccm, hydrazine gas (N2H4) at a flow rate of 10sccm, and nitrous oxide (N2O) at a flow rate of 150 to 600sccm. Thus, the silicon oxide film is grown under these conditions by varying the temperature of heating the wafer W. Since the decomposition temperatures of silane gases such as SiH4, Si2H6, Si3H6, etc., are in the range 200 to 300 deg.C, it is possible to grow the oxide film at low temperature and at high speeds if the N2O gas is efficiently decomposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a step of growing a CVD oxide film.

In recent VLSIs, it is necessary to reduce the total heat treatment. For 64M DRAM, the limit is 850 ° C. and 30 minutes. Therefore, C
The VD process also needs to reduce the heat treatment.

[0003]

2. Description of the Related Art Generally, a mixed gas of silanes and nitrous oxide is used as a reaction gas when forming a silicon oxide film by a CVD method.

As a film forming apparatus, a batch type such as a decompression vertical furnace is used. According to this, the deposition rate is as small as 30Å / min at a growth temperature of 800 ° C., and the heat treatment for film formation takes a long time. I will end up. For example, it takes 33 minutes to grow to a thickness of 1000Å.

In addition, including the time for the temperature of the furnace to stabilize, the time during which the wafer is heated reaches 3 hours or more in one step. When an oxide film is formed by a single-wafer type low pressure CVD apparatus, the same reaction gas is used, and the growth rate thereof is 90Å / min at 800 ° C. as shown in FIG. 3 (a). In FIG. 3, the symbol r indicates the flow rate ratio of the nitrous oxide gas to the silane-based gas.

However, at such a high growth temperature,
Since problems such as stress occur, it is preferable to lower the temperature of heat treatment.

[0007]

However, for example, if the oxide film growth temperature in a batch system is lowered to 725 ° C., the deposition rate capable of making the film thickness uniform becomes 6Å / min, which requires a long deposition time of 3 hours. Therefore, the throughput is reduced.

Further, the film quality of the CVD oxide film can be evaluated by the refractive index, and it is generally said that 1.45 is good. However, according to the single-wafer type low pressure CVD apparatus, when the growth temperature is 750 ° C. or less, FIG. On the other hand, as shown in (a), the growth rate increases, but the refractive index of the oxide film becomes considerably larger than 1.45 as shown in FIG. 3 (b).

Further, the growth temperature of the oxide film is set to 400, for example.
When the temperature is lowered to around 0 ° C., at such a temperature, it is difficult to grow the film regardless of whether the batch type or the single-wafer type is used. From the above, it is difficult to reduce the heat treatment, and VLSI
May hinder the development of.

The present invention has been made in view of the above problems, and provides a method for manufacturing a semiconductor device which has a high film growth rate and can grow a high-quality CVD oxide film under a low heat treatment. The purpose is to

[0011]

The above-mentioned object can be achieved by a method of manufacturing a semiconductor device, which comprises a step of depositing an oxide film by using a reaction gas of hydrazine, nitric oxide and silanes.

Alternatively, the substrate temperature during the deposition is set to 370
This is achieved by a method for manufacturing a semiconductor device, which is characterized by setting the temperature to be at least ° C. Alternatively, when the deposition of the oxide film is performed by a single-wafer deposition apparatus, the deposition pressure is 0.1 Torr to 300 To.
It is achieved by a method for manufacturing a semiconductor device, which is performed in a range of rr and when a batch type film forming apparatus is performed, the deposition pressure is in a range of 0.1 Torr to 1.0 Torr.

Alternatively, it is achieved by a method for manufacturing a semiconductor device, which is characterized by introducing nitric oxide into the surface of the oxide film and nitriding it. Alternatively, it is achieved by a method of manufacturing a semiconductor device, which comprises a step of nitriding a surface of an underlayer of the oxide film by introducing hydrazine before growing the oxide film.

Alternatively, as a pretreatment for nitriding the surface of the underlayer, the surface of the underlayer is subjected to either hydrogen baking or anhydrous hydrofluoric acid treatment, which is a method for manufacturing a semiconductor device.

Alternatively, it is achieved by a method of manufacturing a semiconductor device, which includes a step of depositing a nitride film after nitriding the underlayer and before forming the oxide film. Alternatively, it is achieved by a method for manufacturing a semiconductor device, which comprises depositing the oxide film after introducing nitrogen oxide into the surface of the nitride film to oxidize it.

[0016]

[Operation] According to the present invention, hydrazine is added to silanes and nitric oxide as a reaction gas when the silicon oxide film is formed by the CVD method.

Here, the decomposition temperature of silanes is 200 to 3
Since the temperature is 00 ° C., if nitrogen oxide can be decomposed efficiently, film deposition can be performed at low temperature and at high speed. Here, the decomposition temperature of nitric oxide is 600 ° C., and if heat treatment is performed at a temperature higher than that, film deposition will occur, and conventionally, film growth was performed under such conditions.

On the other hand, when hydrazine is contained, nitric oxide is reduced, and oxygen or an intermediate product generated thereby reacts with silanes and an intermediate product thereof,
Since the reaction gas is efficiently consumed, a high deposition rate can be obtained at a low temperature.

The refractive index of the silicon oxide film thus grown was about 1.45, and a good quality film was formed. Moreover, according to this method, a good quality film was grown even at a low temperature of 370 ° C.

In consideration of film uniformity and the like, the deposition pressure is 0.1 Torr to 300 when a single-wafer type film forming apparatus is used.
When the process is performed in the Torr range and the batch type film forming apparatus is used, the deposition pressure is optimally in the range of 0.1 Torr to 1.0 Torr.

Further, the underlying layer may be nitrided before the oxide film is formed, a hydrofluoric acid anhydride treatment or a hydrogen bake treatment may be performed before the nitriding treatment, or a nitride film may be formed thereon after the nitriding treatment. It may be provided. Further, the surface of the nitride film may be oxidized or the surface of the oxide film may be nitrided. According to these, the breakdown voltage of the insulating film is improved.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. (A) Description of the First Embodiment of the Present Invention FIG. 1 (a) shows a single wafer CVD used in the first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing an example of the apparatus, and FIG. 2 is an actual measurement diagram showing changes in growth rate and refractive index with respect to temperature changes of the oxide film formed according to the first embodiment of the present invention.

In FIG. 1A, a single-wafer type low pressure CVD apparatus indicated by reference numeral 1 is a reaction chamber 2, a gas introducing pipe 3 for introducing a reaction gas into the reaction chamber 2, and a wafer W to be deposited. A susceptor 4 on which the gas is introduced, a gas discharge plate 5 attached to the lower end of the gas introduction pipe 3 and facing the susceptor 4, a heater 6 for heating the susceptor 4, and an exhaust pipe 7 attached in the reaction chamber 2. have.

Next, a process of growing a silicon oxide film using the above-mentioned single-wafer CVD apparatus 1 will be described. First,
With the wafer W placed on the susceptor 4, the gas in the reaction chamber 2 is exhausted through the exhaust pipe 7 to maintain the internal pressure at 3 Torr, and the disilane (Si ₂ H _2
6 ) is introduced at 3 sccm, hydrazine (N ₂ H ₄ ) is introduced at 10 sccm, and nitrous oxide (N ₂ O) is introduced at a flow rate of 150 to 600 sccm.

When the heating temperature of the wafer W was changed under these conditions to grow the silicon oxide film, the growth rate was as shown in FIG. 2 (a). By the way, SiH ₄ , Si ₂ H ₆ ,
Since the decomposition temperature of silanes such as Si ₃ H ₈ is about 200 to 300 ° C., if N ₂ O can be decomposed efficiently, the oxide film can be deposited at low temperature and at high speed.

In this embodiment, N ₂ H ₄ is mixed in the reaction gas, so that N ₂ O is reduced and oxygen or an intermediate product thereof is produced. Since this reacts with Si ₂ H ₆ and its intermediate products and the reaction gas is consumed efficiently, the deposition rate does not decrease even at a low temperature of about 700 ° C compared to the conventional method, and even at 370 ° C, 60Å / min. Growth was observed.

On the other hand, when the refractive index due to film formation is examined by ellipsometry or the like, it becomes as shown in FIG.
In a wide range of 850 ° C., the refractive index was around 1.45, which was almost uniform, and a good quality film was obtained even at low temperatures.

In the case of the single-wafer type, the deposition pressure is preferably 0.1 to 300 Torr in consideration of the uniformity of film thickness and film quality. (B) Description of Second Embodiment of the Present Invention FIG. 1 (b) shows a batch type CV used in the second embodiment of the present invention.
It is a schematic block diagram which shows an example of D apparatus.

The batch type vertical decompression CVD apparatus indicated by reference numeral 11 in FIG. 1 (b) is a reaction chamber 12 composed of an outer tube 12a and an inner tube 12b of an open upper end, a heater 13 surrounding the reaction chamber 12, and an outer tube. It has an exhaust pipe 14 connected between 12a and the inner tube 12b, and a plurality of gas injectors 15 penetrating the lower side wall of the inner tube 12b, and the exhaust pipe 14 is connected to an exhaust pump 16. The gas in the reaction chamber 12 is exhausted and the pressure is reduced.

A wafer basket 17 is mounted in the inner tube 12, and the wafer basket 17 is attached.
A plurality of wafers W are housed therein with a gap in the gas flow direction.

Next, a process of forming a silicon oxide film on the wafer W by using the vertical CVD apparatus 11 described above will be described. First, a plurality of wafers W are attached to the wafer basket 17 and housed in the inner tube 12b of the reaction chamber 12.

Then, the inside of the reaction chamber 12 is decompressed through the exhaust pipe 14 and the internal pressure is maintained at 0.2 Torr, while Si ₂ H ₆ is 30 sccm and N ₂ H ₄ is 100 from the gas injector 15.
Sccm and N ₂ O are supplied at a flow rate of 1.5 to 6.0 SLM to form a silicon oxide film on the wafer W.

Also in this case, as in the first embodiment, 370
By the heat treatment at ℃ to 800 ℃, N ₂ O is reduced by N ₂ H ₄ to produce oxygen or its intermediate product. Since this reacts with Si ₂ H ₆ and its intermediate product and the reaction gas is efficiently consumed, a high deposition rate can be obtained at a low temperature. For example, under the above conditions, the growth rate at a temperature of 800 ° C is about 200Å / mi.
n, and the deposition time for a film thickness of 1000Å is 5 minutes.

Further, by adding N ₂ H ₄ , it becomes possible to grow an oxide film at 370 ° C. as in the first embodiment, and the refractive index thereof is 1.45 at 370 to 850 ° C. Was secured.

According to the batch method, the deposition pressure is preferably within the range of 0.1 to 1.0 Torr in view of the film pressure and the uniformity of film quality. (C) Description of Other Embodiments of the Present Invention In the above-mentioned two embodiments, only the growth of the silicon oxide film was described. However, when the underlying layer is silicon, the following processing may be performed.

Before forming the oxide film, hydrazine may be introduced in the film forming apparatus to nitride the surface of the silicon layer, and then the above silicon oxide film may be grown. The nitriding conditions are, for example, a temperature of 800 ° C., an atmospheric pressure of 50 Torr, and 100 sc of monomethylhydrazine.
It is introduced into the reactor at a flow rate of cm. Do this for 3 minutes.
After that, 3 sccm of Si ₂ H ₆ and 1 sc of monomethylhydrazine
A silicon oxide film is deposited by introducing 0 sccm and N ₂ O at a flow rate of 150 to 600 sccm, setting the pressure to 3 Torr and the temperature to 800 ° C.

Before the nitriding, the surface of the underlying silicon may be subjected to hydrogen baking treatment or anhydrous hydrofluoric acid treatment. When the hydrogen bake is performed, for example, H ₂ is introduced at a flow rate of 50 SLM, the temperature is 850 ° C., and the atmospheric pressure is 20 To.
Do as rr. In the case of hydrofluoric acid anhydride treatment, for example, hydrofluoric acid anhydride (AHF; Anhydrous Hydrogen Fluoride) is used.
Is introduced at a flow rate of 100 sccm and the pressure of the atmosphere is adjusted to 10
0 Torr and the air temperature are room temperature.

The underlying layer of the silicon oxide film is a nitride film.
When (Si ₃ N ₄ ) is used, the following steps may be performed. First, monomethylhydrazine was introduced into the reactor at a flow rate of 100 sccm at a temperature of 800 ° C. and an atmospheric pressure of 50 Torr, and the surface of the silicon layer was nitrided by treating for 3 minutes. As 3 Torr, Si ₂ H ₆ and N ₂ H ₄ are caused to flow at a flow rate of 50 sccm and 10 sccm, respectively, thereby depositing a Si ₃ N ₄ film. When SiH ₄ is used instead of Si ₂ H ₆ , the flow rate is 100 sccm.
In place of N ₂ H ₄ , NH ₃ may be introduced in an amount of 20 sccm.

After that, a high-quality silicon oxide film is formed under the conditions described above. The above-mentioned AHF treatment or hydrogen-based treatment may be performed before nitriding the silicon surface.

Further, nitrogen oxide gas may be supplied to the silicon oxide film grown under the above conditions to nitride the surface thereof. In addition, N ₂ is formed on the surface of the Si ₃ N ₄ film that is the base of the silicon oxide film.
O 2 may be supplied to oxidize the surface. The oxidation conditions in this case are a temperature of 750 ° C., a pressure of 100 Torr, and an oxidation time of 30 minutes.

Specific examples of growing a silicon oxide film after nitriding the silicon surface, forming a nitride film and a silicon oxide film after the nitriding, or nitriding the surface of the silicon oxide film are as follows. For example, there is a gate insulating film of a thin film transistor or an insulating film on a floating gate of an EEPROM, which improves the breakdown voltage.

[0042]

As described above, according to the present invention, the CV
When the silicon oxide film is formed by the D method, hydrazine is added as a reaction gas in addition to silanes and nitric oxide.

Here, the decomposition temperature of silanes is 200 to 3
It is 00 ° C. In addition, since nitric oxide is reduced by hydrazine at low temperature, oxygen or its intermediate product generated by this reacts with silanes and its intermediate product,
Since the reaction gas is efficiently consumed, a high deposition rate can be obtained at a low temperature.

The refractive index of the silicon oxide film thus grown is around 1.45, and a high quality film can be formed. Moreover, according to this method, a good quality film can be grown even at a low temperature of 370 ° C.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a low pressure CVD apparatus used in the present invention.

FIG. 2 is a CVD according to a temperature change of the first embodiment of the present invention.
It is a characteristic view which shows the growth rate of an oxide film, and the change of a refractive index.

FIG. 3 is a characteristic diagram showing changes in a growth rate and a refractive index with respect to a temperature change in growing an oxide film by a conventional method.

[Explanation of symbols]

 1 Single wafer type low pressure CVD apparatus 11 Batch type low pressure CVD apparatus

Claims (8)

[Claims] 1. A method of manufacturing a semiconductor device, comprising a step of depositing an oxide film using a reaction gas of hydrazine, nitric oxide and silanes. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the substrate temperature during the deposition is set to 370 ° C. or higher. 3. The deposition pressure is set to 0.1 Torr to 300 Torr when the oxide film is deposited by a single-wafer type film forming apparatus, and the deposition pressure is set to 0.
3. The method for manufacturing a semiconductor device according to claim 1, wherein the method is performed in a range of 1 Torr to 1.0 Torr. 4. The method of manufacturing a semiconductor device according to claim 1, wherein nitric oxide is introduced into the surface of the oxide film to perform nitriding. 5. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of nitriding a surface of an underlayer of the oxide film by introducing hydrazine before growing the oxide film. Method. 6. The method of manufacturing a semiconductor device according to claim 5, wherein as a pretreatment for nitriding the surface of the underlayer, the surface of the underlayer is subjected to either hydrogen baking or anhydrous hydrofluoric acid treatment. . 7. The method of manufacturing a semiconductor device according to claim 5, further comprising a step of depositing a nitride film after nitriding the underlayer and before forming the oxide film. 8. The method for manufacturing a semiconductor device according to claim 7, wherein the oxide film is deposited after introducing nitrogen oxide into the surface of the nitride film to perform oxidation.