JPH05144765A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent doping to a region where boron or phosphorus or the like is diffused during heat treatment from a BPSG film. CONSTITUTION:After an aperture is opened in a BPSG film 5 to expose a diffused region 2 on a silicon substrate 1, an upper oxide film 6 is formed. Moreover, an aperture is opened on the upper oxide film 6 in such a manner that the upper oxide film 6 is left at the surface of BPSG film 5 and the side surface of aperture. Thereafter, the heat treatment is carried out to form aluminum wirings. Thereby, fluctuation of resitances in the diffused region and precipitation of silicon in the aluminum wiring process can be controlled, as much improving reliability of a semiconductor device.

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 opening a BPSG film.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show conventional BPSG (Boro-Ph).
It is sectional drawing which shows the process of forming an opening in an ospho Silicate Glass) film. In these figures, 1 is a silicon substrate, 2 is a diffusion region of N ⁺ or P ⁺ , 3 is a thermal oxide film,
4 is a gate electrode or wiring (hereinafter referred to as wiring), 5 is BP
It is an SG film.

First, the flow of FIGS. 3A and 3B will be described. As shown in FIG. 3A, a BPSG film 5 is formed as an insulating film on the entire surface of the silicon substrate 1 on which the wiring 4 is formed, and the BPSG film 5 is reflowed by heat treatment for planarization. Next, as shown in FIG. 3B, the silicon substrate 1
A BPSG film 5 is opened for bonding with the diffusion region 2 formed above.

Further, in the flow of FIGS. 4 (a) and 4 (b),
As shown in FIG. 4A, the BPSG film 5 is formed similarly to FIG.
4B, the wet etching is first performed to open the BPSG film 5, and then the BPSG film 5 is formed.
When anisotropic dry etching is performed, the opening portion is opened upward, and the coverage of aluminum wiring in the next aluminum wiring step is improved. As described above, after the BPSG film 5 is opened, heat treatment is performed to form aluminum wiring (not shown).

[0005]

Since the conventional opening process of the BPSG film 5 is performed as described above, the boron and phosphorus of the BPSG film 5 are diffused at the opening part in the heat treatment of the next process. There are problems such as auto-doping in the region 2 to cause variations in the resistance of the diffusion region 2 and to accelerate the deposition of silicon in the aluminum wiring process.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to prevent the autodoping of boron and phosphorus from the BPSG film during the heat treatment after the formation of the BPSG film. It is an object of the present invention to provide a manufacturing method capable of obtaining a semiconductor device having a high aperture.

[0007]

According to the method of manufacturing a semiconductor device of the present invention, after forming a hole in a BPSG film, an oxide film for protecting the BPSG film including the hole is stacked and heat treatment is performed. Is formed.

[0008]

According to the method of manufacturing a semiconductor device of the present invention, the BP
Since the surface of the SG film, the side surface of the opening, and the surface of the diffusion region exposed in the opening are covered with the oxide film, the boron and phosphorus diffusion regions of the BPSG film can be automatically doped during the heat treatment in the subsequent process. Can be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1A to 1D are sectional views showing the main steps of the method for manufacturing a semiconductor device of the present invention. In FIG. 1, the same reference numerals as those in FIGS. 3 and 4 denote the same components, and 6 denotes the BPS.
It is an overlying oxide film formed after the opening of the G film 5.

Next, the flow of FIG. 1 will be described. As shown in FIG. 1A, BPS is formed on the wiring 4 as an insulating film.
After the G film 5 is formed, a B heat treatment is performed for planarization.
The PSG film 5 is reflowed. Next, as shown in FIG. 1B, the BPSG film 5 is opened for bonding with the diffusion region 2 formed on the silicon substrate 1. Next, FIG.
As shown in (c), an overlying oxide film 6 is formed and BP
The surface of the SG film 5 and the side and bottom surfaces of the opening, that is, the exposed surface of the diffusion region 2 is covered with this overlying oxide film 6. Further, as shown in FIG. 1D, the upper oxide film 6 is opened for bonding with the diffusion region 2. At that time, B
The upper oxide film 6 is opened so as to be smaller than the opening of the PSG film 5. In this way, after the BPSG film 5 and the overlying oxide film 6 are opened, heat treatment is performed to form aluminum wiring.

2A to 2D are process sectional views showing another embodiment of the present invention. First, as shown in FIG. 2A, after forming the BPSG film 5 as an insulating film, the BPSG film 5 is reflowed by heat treatment for planarization. Next, as shown in FIG. 2B, the BPSG film 5 is opened for the diffusion region 2 formed on the silicon substrate 1. Next, as shown in FIG. 2C, an overlying oxide film 6 is formed, and the surface of the BPSG film 5 and the side surface of the opening are covered with the overlying oxide film 6. Further, as shown in FIG. 2D, in order to bond with the diffusion region 2, an opening is performed by anisotropic dry etching so that the stacked oxide film 6 remains on the surface of the BPSG film 5 and the side surface of the opening. Make a hole. In this way, BP
After the SG film 5 and the overlying oxide film 6 are opened, heat treatment is performed to form aluminum wiring.

In the embodiment shown in FIG. 2, anisotropic etching is performed so that the overlying oxide film 6 remains on the surface of the BPSG film 5 and the side surface of the opening, but it is left only on the side surface of the opening. May be etched.

[0013]

As described above, according to the present invention,
Since the surface of the BPSG film and the side surface of the opening are covered with the overlying oxide film, the BPS at the time of heat treatment in the subsequent process
It is possible to prevent the diffusion of boron and phosphorus from the G film into the diffusion region, and suppress variations in resistance in the diffusion region and silicon deposition in the aluminum wiring process.

[Brief description of drawings]

FIG. 1 is a process sectional view showing an embodiment of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a process sectional view showing another embodiment of the present invention.

3A to 3D are process cross-sectional views showing a conventional method for manufacturing a semiconductor device.

FIG. 4 is a process sectional view showing another conventional example.

[Explanation of symbols]

 1 Silicon substrate 2 Diffusion region 3 Thermal oxide film 4 Wiring 5 BPSG film 6 Stacked oxide film

Claims (1)

[Claims] 1. An opening is formed in a BPSG film formed as an insulating film on a semiconductor substrate, and a wiring layer formed in the opening is contacted with a diffusion region formed in the semiconductor substrate. In the method of manufacturing a semiconductor device, the BP
After forming an opening in the SG film, a step of forming an overlying oxide film on the surface of the BPSG film and the side surface of the opening to cover it, and then performing a heat treatment to form a wiring. Device manufacturing method.