JP3390890B2 - Method for manufacturing semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to an inorganic thick film SOG (spin).
on glass) for forming an interlayer insulating film.

[0002]

2. Description of the Related Art Conventionally, in order to flatten a wiring layer of a semiconductor integrated circuit device, an inorganic SOG made of tetraalkoxysilane or an organic SOG made of methyltrialkoxysilane has been used. Since the SOG contains a methyl group or an ethyl group that does not contribute to the bond, the shrinkage stress is small, and therefore the crack resistance is good, but conversely, if the methyl group or the ethyl group contained is large, the photoresist becomes In the ashing process and the like, there is a drawback that it deteriorates when exposed to oxygen plasma.

In recent years, as an SOG having both crack resistance and oxygen plasma resistance, an inorganic thick film SOG made of a Si compound material having a molecular end terminated with hydrogen and having a silazane bond in the skeleton has been put to practical use. . Unlike the conventional SOG, this inorganic thick film SOG can oxidize silazane bonds and convert it into a dense and high-quality oxide film by setting it in an oxidizing atmosphere such as an oxygen atmosphere or a steam atmosphere during firing.

However, when such a firing method is used, a defect occurs in the wiring layer such as Al due to the temperature decrease rate after the firing step, or a heat treatment step after the firing step, for example, 450 ° C. before the formation of the Al wiring layer. In annealing at a moderate temperature, a large amount of degas is generated from SOG, and the Al wiring layer is corroded by the reaction with the degas, and the interlayer insulating film is ruptured by bubbles of the degas. It was happening.

Of these, Al depending on the temperature decrease rate after the firing step
In order to prevent the occurrence of defects in the wiring layer such as, the firing reaction is suppressed by lowering the firing temperature, or the firing reaction is shortened to reduce the moisture taken in from the firing atmosphere. Suppressing SO
The stress due to the contraction of G can be reduced to prevent the underlying Al wiring layer from being damaged.

Next, in order to suppress the generation of outgas from SOG in the heat treatment step after the firing step, firing is performed in a steam atmosphere so that degassing is completed at the time of firing and degassing is performed in the subsequent step. Generation of gas can be reduced.

[0007]

However, if the firing temperature is lowered or the heating time is shortened, the oxidation becomes insufficient, which defeats the purpose of converting the oxide film into a dense and high-quality oxide film, resulting in deterioration of the film quality of the oxide film. However, even if the firing is performed in a steam atmosphere, since firing cannot be performed for a sufficient time from the viewpoint of suppressing the occurrence of defects in the underlying Al wiring layer, degassing still occurs. The problem of will remain.

Therefore, according to the present invention, the wiring layer is deficient in the step of firing the inorganic thick film SOG forming material made of a Si compound material having a silazane bond in the skeleton, the molecular end of which is terminated by hydrogen, and the subsequent heat treatment step. The purpose is to suppress the generation of gas and degassing.

[0009]

The present invention provides a wiring layer (3 in FIG. 1) surface provided on a base insulating film (2 in FIG. 1) and an exposed surface of the base insulating film (2 in FIG. 1). CVD film (Fig. 1
4) is deposited, and then an inorganic thick film SOG forming material composed of a Si compound material having a molecular end terminated with hydrogen and having a silazane bond in the skeleton is applied, and this inorganic thick film SOG is applied.
In the step of baking the semiconductor wafer coated with the forming material, pulling out the semiconductor wafer from the baking furnace is 900 mm.
The feature is that it is performed at a high speed of more than 1 minute. Further, the present invention is characterized in that firing is performed in a dry oxygen atmosphere or a steam atmosphere.

The present invention also provides a base insulating film (2 in FIG. 1).
An inorganic thick film SOG forming material composed of a Si compound material whose molecular end is terminated by hydrogen so as to cover the wiring layer (3 in FIG. 1) provided above and having a silazane bond in the skeleton is applied, and this inorganic thickness It is characterized in that the semiconductor wafer coated with the material for forming a film SOG is left in a closed container for 24 hours or more and then baked.

Further, the present invention is characterized in that the inorganic thick film SOG left in a closed container for 24 hours or more after coating is baked in a dry oxygen atmosphere. The present invention also relates to CVD
A feature is that a plasma CVD film is used as the film.

[0012]

[Operation] Pulling out the semiconductor wafer from the baking furnace 900 m
By performing the heating at a high speed of m / min or more, the temperature lowering time from the firing temperature to room temperature can be shortened to about 45 minutes, so that the shrinkage stress can be reduced and the occurrence of defects in the underlying Al wiring layer can be prevented. Also, when firing is performed in a dry oxygen atmosphere, the film quality of the oxide film is somewhat inferior, but the configuration of the firing apparatus can be simplified, while when firing is performed in a steam atmosphere, Although it is necessary to provide a special mechanism such as a steam generator in the baking apparatus, the obtained oxide film becomes more dense and the film quality is improved.

After the inorganic thick film SOG is applied, 2
By leaving it in the closed container for 4 hours or more, the water in the air in the container is naturally adsorbed on the surface of the SOG film in the closed container, and the water reacts with the component of SOG to generate ammonia. The produced ammonia acts as a catalyst to further advance the reaction. Then, as a result, the state of firing is the same as the state of firing in a steam atmosphere, so that degassing is almost completed at the time of firing.

Further, as described above, the state of firing is the same as the state of firing in a steam atmosphere, so firing in a dry oxygen atmosphere is sufficient, and the configuration of the firing apparatus is simplified. be able to. Also, as described later,
Since the Zuma CVD film has a high blocking effect, that is, the film is fine.
Since it is dense, plasma CVD film is used as the CVD film.
Water can be blocked by doing so.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a first embodiment of the present invention. Referring to FIG. 1, first, an Al wiring layer 3 is provided on a silicon semiconductor substrate 1 through a base insulating film ₂ such as SiO ₂ , and then SiH ₄ is 40 ml / min, N ₂ O is 150 ml / min, and N ₂ is 200 ml.
A film thickness of 450 n is obtained by a plasma CVD method in which RF power of 240 W is applied at a substrate temperature of 250 ° C. under a pressure of 3.0 Torr and a flow rate of 0 ml / min.
The SiON film 4 of m is deposited so as to cover the exposed surfaces of the Al wiring layer 3 and the base insulating film 2.

In this case, the SiON film 4 obtained
Represents a silicon oxynitride film generically, and does not represent a film of Si: O: N = 1: 1: 1. The refractive index of the SiON film 4 obtained in this case was 1.58.

Next, after applying an SOG-forming material composed of a Si compound material whose molecular ends are terminated by hydrogen and having a silazane bond in the skeleton, a semiconductor wafer coated with the SOG-forming material is 900 mm / min. 450 ℃ at insertion speed
It is inserted into the firing furnace whose temperature has been raised to.

Then, in a firing furnace, firing is performed at a temperature of 450 ° C. for 30 minutes in a dry oxygen atmosphere, and after the firing is completed, the semiconductor wafer is pulled out from the firing furnace at a withdrawing speed of 900 mm / min, and rapidly heated to room temperature. The temperature is lowered to obtain the densified SOG film 5. In this case, the cooling time from 450 ° C. to room temperature was 45 minutes. The firing temperature is 45
0 ° C. is suitable, but it may be in the range of 400 ° C. to 500 ° C., and may be in the range of 10 minutes to 120 minutes, depending on the firing time and the firing temperature.

Next, Table 1 shows the experimental results of the first embodiment and the comparative example.

[Table 1]

Table 1 shows the first embodiment of the present invention in which the insertion speed into the firing furnace and the withdrawal speed from the firing furnace are both 900 mm / min, and the insertion speed into the firing furnace is 900 mm / min. In comparison with the comparative example in which the drawing speed from the firing furnace was 120 mm / min, the upper fraction in Table 1 represents the size of the defect with respect to the wiring width, and the lower number represents the number of defects in one chip. And 0 means that there is no defect at all. In the comparative example, other conditions are exactly the same except that the drawing speed from the firing furnace is different.

As is clear from Table 1, in the comparative example, the Al wiring layer had a defect, but in the first embodiment of the present invention, no defect was observed. in short,
By setting the drawing speed from the baking furnace to a high speed of 900 mm / min or more, the temperature decrease time from the furnace temperature to the room temperature of the baking furnace can be shortened, thereby reducing the shrinkage stress generated in the inorganic thick film SOG film, and reducing the wiring. The occurrence of defects in the layer is suppressed.

In the comparative example, when the wiring width is 0.7 μm, 71 defects having a size of 0.7 μm are generated per chip, and when the wiring width is 1.0 μm. , 0.2 μm in size, 6 defects were generated per chip. As described above, since the frequency of occurrence tends to increase as the wiring width becomes narrower, the present invention is more effective in an ultra-high integration semiconductor integrated circuit device having an improved integration degree.

In the above embodiment, the baking is carried out in a dry oxygen atmosphere, but it may be carried out in a water vapor atmosphere. In this case, the oxidation reaction proceeds further, so that the film is dense and has a good film quality. A stable SOG film can be obtained. However, in order to obtain a steam atmosphere, it becomes necessary to incorporate a steam generator such as a combustion device composed of oxygen and hydrogen into the firing furnace.
The device becomes large and complicated.

In the first embodiment, the CVD for covering the wiring layer is performed in consideration of the water blocking effect.
Although a plasma SiON film is used as the film, plasma SiN may be used, or a plasma SiO ₂ film may be stacked on this plasma SiN film to form a two-layer film.

Next, a second embodiment of the present invention will be described with reference to FIGS. Referring to FIG. 1, first, an Al wiring layer 3 is provided on a silicon semiconductor substrate 1 via a base insulating film ₂ such as SiO ₂ , then SiH ₄ is 40 ml / min, N ₂ O is 150 ml / min, and N ₂ is 200 ml.
A film thickness of 450 n is obtained by a plasma CVD method in which RF power of 240 W is applied at a substrate temperature of 250 ° C. under a pressure of 3.0 Torr and a flow rate of 0 ml / min.
The SiON film 4 of m is deposited so as to cover the exposed surfaces of the Al wiring layer 3 and the base insulating film 2. Even in this case,
The obtained SiON film 4 is a generic term for a silicon oxynitride film, and does not represent a film of Si: O: N = 1: 1: 1. In addition, the SiO obtained in this case
The refractive index of the N film 4 was 1.58.

Next, an SOG-forming material composed of a Si compound material having molecular ends terminated with hydrogen and having a silazane bond in the skeleton is applied, and then a semiconductor wafer on which the SOG-forming material is applied is processed into a raw crystal BOX ( Store in a closed container (such as the container used to purchase the wafer) and leave it for 24 hours or more.
While left to stand, moisture in the air in the container is naturally adsorbed on the surface of the coating film to generate ammonia as a reaction product, and the generated ammonia acts as a catalyst to further advance the reaction.

Next, after standing for 24 hours or more, the semiconductor wafer coated with the SOG forming material is inserted into a firing furnace heated to 450 ° C. at an insertion speed of 900 mm / min, and in the firing furnace, Sintering is performed at a temperature of 450 ° C. for 30 minutes in a dry oxygen atmosphere, and after the firing is completed, the semiconductor wafer is pulled out from the firing furnace at a withdrawing speed of 900 mm / min, and the temperature is rapidly lowered to room temperature to densify the SOG film 5. To get

Referring to FIG. 2, FIG. 2 shows that the SOG film 5 thus obtained is heated at a heat treatment step after the firing step, for example, at a temperature of about 450 ° C. corresponding to the annealing temperature before the formation of the Al wiring layer. In the case of TDS (Thermal Desorptio)
n Spectroscopy: A device for measuring the gas generated in the system by heating).

As is clear from the figure, the degassing amounts of the gas having a molecular weight of 16, the gas having a molecular weight of 17 and the gas having a molecular weight of 18 are not the same over time, but the total amount of degassing when left for 24 hours ( The third black-painted quadrangular dot from the left side in the figure is reduced to 1/2 or less compared to the case where the leaving time is 0, and when left for 48 hours (fourth black-painted quadrangle from the left side in the figure). Dot) is 1 /
It can be understood that the number is reduced to 6 or less.

Therefore, after applying the SOG forming material,
By leaving it in a closed container for at least 24 hours,
The generation of a large amount of degas can be suppressed. In addition,
If the coating is left to stand in an open system, the ammonia produced by the reaction with water scatters and does not act as a catalyst, and the reaction is slowed down, so that the effect of standing is not so great.

In the second embodiment, the same insertion / drawing conditions and firing conditions as in the first embodiment are adopted, but as is clear from Table 1 above, the wiring layer When the width is 2.0 μm or more, the drawing speed from the firing furnace need not be 900 mm / min or more.

In each of the above embodiments, the Al wiring layer is used as the wiring layer, but the wiring layer is not limited to the Al wiring layer, and an Al alloy wiring layer containing Cu or the like or W or the like. Other refractory metal wiring layers may also be used.

[0033]

According to the present invention, when an inorganic thick film SOG film formed of a Si compound material having molecular ends terminated by hydrogen and having a silazane bond in the skeleton is used as an interlayer insulating film, By increasing the speed of withdrawing the semiconductor wafer from the firing furnace in the firing step, or
Leaving the coated semiconductor wafer in a closed container for a long time before firing suppresses the occurrence of defects in the wiring layer, and also prevents corrosion of the wiring layer and rupture of the interlayer insulating film due to degassing. Since it can be suppressed, a highly reliable semiconductor device can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view common to a first embodiment and a second embodiment of the present invention.

FIG. 2 is a diagram showing a correlation between a standing time and a degassing amount in the second embodiment of the present invention.

[Explanation of symbols] 1 Silicon semiconductor substrate 2 Base insulating film 3 Al wiring layer 4 CVD SiON film 5 SOG film

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Claims (9)

(57) [Claims] 1. A CVD film is deposited on a surface of a wiring layer provided on a base insulating film and an exposed surface of the base insulating film, and then,
An inorganic thick film SOG forming material made of a Si compound material having a molecular terminus terminated by hydrogen and having a silazane bond in the skeleton was applied, and the semiconductor wafer coated with the inorganic thick film SOG forming material was fired in a firing furnace. After that, the withdrawal speed when withdrawing the semiconductor wafer from the firing furnace is 900 mm.
A method for manufacturing a semiconductor device, which is characterized by a high speed of not less than / minute. 2. The inorganic thick film SO prior to the firing.
2. The method for manufacturing a semiconductor device according to claim 1, wherein when the semiconductor wafer coated with the G forming material is inserted into the firing furnace, the insertion speed is set to a high speed of 900 mm / min or more. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the firing is performed in a dry oxygen atmosphere. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the firing is performed in a water vapor atmosphere. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the CVD film is a SiON film. 6. A material for forming an inorganic thick film SOG comprising a Si compound material whose molecular end is terminated by hydrogen so as to cover a wiring layer provided on a base insulating film and has a silazane bond in the skeleton, After leaving the semiconductor wafer coated with the material for forming an inorganic thick film SOG in a closed container for 24 hours or more,
A method of manufacturing a semiconductor device, which comprises firing to form an inorganic thick film SOG film. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the firing is performed in a dry oxygen atmosphere. 8. When the semiconductor wafer is pulled out from the firing furnace after the firing, the pulling rate is 900 mm /
8. The method for manufacturing a semiconductor device according to claim 6, wherein the number of minutes is set to be at least a minute. 9. The CVD film is a plasma CVD film.
9. The method according to any one of claims 1 to 8, characterized in that
Of manufacturing a semiconductor device of.