JPH0817926A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent oxidation of a substrate and wiring at the time of reflow of a BPSG film in a steam atmosphere, without using a silicon nitride film of large stress. CONSTITUTION:A modified layer 4 is formed on the surface layer of a silicon oxide film 3 by sputter-etching the silicon oxide film 3 surface with argon gas. A BPSG film 5 is formed and subjected to reflow in a steam atmosphere. The working modified layer 4 prevents the oxidation of the substrate 1 and the wiring layer 2.

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 a method of manufacturing a semiconductor device including a step of subjecting a silicon glass film containing impurities to a reflow process.

[0002]

2. Description of the Related Art In recent years, along with the high integration of semiconductor integrated circuits, it has become important to flatten the surface layer. Among them, BPSG (Boro-Pho) is used as an interlayer insulating film in the upper layer of the wiring layer in performing planarization to eliminate the step shape of the wiring layer such as polysilicon and refractory metal that can withstand high temperature heat treatment.
A spho Silicate Glass) film is used. The BPSG film is an insulating film in which boron (B) and phosphorus (P) are introduced into a silicon oxide film to lower the glass transition temperature (reflow softening temperature). The BPSG film has a temperature of about 900 ° C. in a nitrogen atmosphere. By performing heat treatment at a temperature, a flow phenomenon called reflow occurs, and the surface having a step shape is flattened.

However, with the miniaturization of elements, it is necessary to further lower the reflow temperature. As a method therefor, a method is known in which the atmosphere of the reflow treatment is changed from nitrogen to steam. This method will be briefly described with reference to FIG.

First, as shown in FIG. 3A, a wiring layer 12 is patterned on a semiconductor substrate 11, and then a silicon nitride film 17 is formed on the entire surface.

Next, as shown in FIG. 3B, a BPSG film 15 is formed on the entire surface of the silicon nitride film 17.

Next, as shown in FIG. 3C, heat treatment is performed in a steam atmosphere to reflow the BPSG film 15 to flatten the stepped shape of the wiring layer 12.

The reason why the reflow softening temperature is lowered by the heat treatment in the water vapor atmosphere is that when water vapor is taken into the BPSG film, it becomes an OH molecule and the Si--O--Si bond becomes S.
This is because the bond strength is weakened by changing to the i-OH bond.

[0008]

[Problems to be Solved by the Invention] However, BPS
The OH molecules forming the Si—OH bond in the G film 15 easily diffuse during the heat treatment due to the large diffusion coefficient in the oxide film, and oxidize the semiconductor substrate 11 and the wiring layer 12. Therefore, in order to prevent this oxidation, it was necessary to form a silicon nitride film 17 having a small diffusion coefficient of OH molecules as an anti-oxidation film under the BPSG film 15. However, the silicon nitride film 17 has less stress than the silicon oxide film. large. That is, the BPSG film 15 is formed by the heat treatment in the above-described steam atmosphere.
Although the method of reflowing has an advantage that the reflow softening temperature can be lowered, it has a problem that the stress of the silicon nitride film 17 lowers the reliability of the semiconductor device.

Therefore, an object of the present invention is to provide a method of manufacturing a semiconductor device capable of performing reflow with small stress without using a silicon nitride film while keeping the reflow softening temperature low.

[0010]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor device according to the present invention uses a first step of forming a silicon oxide film on a semiconductor substrate and an inert gas. A second step of sputter etching the silicon oxide film, a third step of forming a silicon glass film containing impurities on the silicon oxide film, and a fourth step of performing a reflow process on the silicon glass film. Have.

[0011]

[Function] A work-affected layer is formed on the surface of the silicon oxide film by sputter etching the silicon oxide film using an inert gas, and this work-affected layer prevents oxidation of the semiconductor substrate or wiring layer during reflow treatment. To prevent. Therefore, the reflow softening temperature can be lowered and the low stress reflow can be performed without using the silicon nitride film.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method of manufacturing a semiconductor device of this embodiment in the order of steps.

First, as shown in FIG. 1A, a polysilicon wiring layer 2 having a film thickness of about 0.3 μm is patterned on a semiconductor substrate 1. Then, a silicon oxide film 3 having a thickness of about 0.2 μm is formed on the entire surface by low pressure thermal CVD.
Instead of the polysilicon wiring layer 2, a high melting point metal single layer such as a tungsten silicide film or a laminated structure film of a high melting point metal and polysilicon may be used. Further, as a method for forming the silicon oxide film 3, a normal pressure thermal CVD method or a plasma CV method is used.
Method D can be used.

Next, as shown in FIG. 1B, the surface of the silicon oxide film 3 is sputter-etched by using argon gas to a thickness of about 0.05 μm. As a result, the work-affected layer 4 having a thickness of about 0.05 μm is formed on the surface layer of the silicon oxide film 3.
Is formed. The conditions for the sputter etching are: a parallel plate type RF etcher, a pressure of about 300 Pa, and an RF
The output is about 500 W and the argon gas flow rate is about 50 sccm. In addition to argon, an inert gas such as nitrogen may be used.

The structure of the work-affected layer 4 will be described with reference to FIG. As shown in FIG. 2A, the silicon oxide film 3 before the sputter etching is in a state in which oxygen atoms (O) are bonded to the four directions of silicon atoms (Si). Therefore, the diffusion of the hydroxyl group OH and the like cannot be prevented, and the underlying semiconductor substrate 1 and the wiring layer 2 are oxidized. On the other hand, when the surface of the silicon oxide film 3 is sputter-etched, as shown in FIG. 2B, the bonding state of silicon and oxygen is disturbed in the surface layer, and many dangling bonds are present. Therefore, since the hydroxyl group OH and the like diffused during the reflow process are captured in this portion, the work-affected layer 4 functions as an antioxidant film of the base film.

Next, as shown in FIG. 1C, a BPSG film 5 having a thickness of about 0.5 μm is formed on the work-affected layer 4 under normal pressure heat C.
The film is formed by the VD method. The BPSG film 5 may be formed using a low pressure thermal CVD method or a plasma CVD method.
A silicon glass film (silicate glass) to which germanium or arsenic is added instead of phosphorus and boron contained in the BPSG film 5 may be used.

Next, as shown in FIG. 1 (d), a heat treatment is performed in a steam atmosphere at a temperature of 850 ° C. for 30 minutes to obtain BPS.
The G film 5 is reflowed to flatten the step shape of the polysilicon wiring layer 2. At this time, as described above, the work-affected layer 4 functions as an antioxidant film for the underlying semiconductor substrate 1 and the polysilicon wiring layer 2.

As described above, according to this embodiment,
The work-affected layer 4 formed on the surface of the silicon oxide film 3 functions as an antioxidant film for capturing OH molecules diffused in the silicon oxide film 3 during the reflow process, and the silicon substrate 1 and the wiring layer 2 are oxidized during the reflow process. Can be prevented. In other words, it is possible to perform reflow at a relatively low temperature in a water vapor atmosphere, and prevent the underlying film from being oxidized without using a silicon nitride film with high stress as in the conventional case.
The reliability and the degree of integration of the semiconductor device can be improved.

[0020]

According to the present invention, the work-affected layer is formed on the surface of the silicon oxide film by sputter etching the silicon oxide film with the use of an inert gas, and the work-affected layer is formed in the semiconductor during reflow treatment. Prevents oxidation of the substrate and wiring layers. Therefore, the reflow softening temperature can be lowered and the low stress reflow can be performed without using the silicon nitride film. Therefore, the reliability and the degree of integration of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in process order.

FIG. 2 is a schematic diagram showing a state of bonding between silicon and oxygen.

FIG. 3 is a schematic cross-sectional view showing a method of manufacturing a conventional semiconductor device in the order of steps.

[Explanation of symbols]

 1 semiconductor substrate 2 polysilicon wiring layer 3 silicon oxide film 4 work-affected layer 5 BPSG film

Claims (1)

[Claims] 1. A first step of forming a silicon oxide film on a semiconductor substrate, a second step of sputter etching the silicon oxide film using an inert gas, and containing impurities on the silicon oxide film. A method of manufacturing a semiconductor device, comprising: a third step of forming a silicon glass film, and a fourth step of subjecting the silicon glass film to a reflow process.