JP2712245B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device.

[Conventional technology]

With the increase in the degree of integration of semiconductor devices, the contact portions of electrodes or wirings have been miniaturized, and various means for improving the step coverage of the contact portions have been studied.

2 (a) and 2 (b) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining a conventional method of manufacturing a semiconductor device.

As shown in FIG. 2A, a p-type diffusion region 2 is selectively provided on one main surface of an n-type silicon substrate 1, and a p-type diffusion region 2 is formed.
A silicon oxide film (hereinafter, referred to as a BPSG film) 3 containing boron and phosphorus is deposited on the surface containing. Next, the p-type diffusion region 2
The BPSG film 3 is selectively etched to form a contact opening 4, and the end of the BPSG film in the opening 4 is reflowed and smoothed by heat treatment. At this time, out diffusion of the impurity is caused from the BPSG film 3 and diffused to the surface of the diffusion region 2 of the opening 4 to form the impurity diffusion layer 8.

Next, as shown in FIG. 2B, an aluminum layer 7 is deposited on the surface including the opening 4 and is selectively etched to form an electrode which is in contact with the diffusion region 2 of the opening 4. .

[Problems to be solved by the invention]

The above-described conventional method of manufacturing a semiconductor device is characterized in that the contact resistance is reduced by an impurity diffusion layer formed on the surface of the diffusion region of the contact opening due to out-diffusion of impurities from the BPSG film during a heat treatment for reducing the step of the contact opening. There is a disadvantage that it varies. In addition, since the planarization of the interlayer film due to the miniaturization of the element is indispensable, it is necessary to increase the concentration of phosphorus and boron in the oxide film between the layers,
The effect is also greater.

Further, in order to prevent the above out diffusion, an oxide film can be formed on the entire surface at a relatively low temperature by a vapor phase growth method or the like. However, since the BPSG film is covered with an oxide film, the flowability of the BPSG film is suppressed, and there is a disadvantage that the step cannot be sufficiently reduced.

[Means for solving the problem]

The method of manufacturing a semiconductor device according to the present invention includes a step of selectively providing a diffusion region of the opposite conductivity type on one main surface of the semiconductor substrate of one conductivity type, and a step of forming a silicon oxide film containing boron and phosphorus on the surface including the diffusion region. Providing a contact opening in the diffusion region by selective etching, depositing a thin first silicon oxide film on a surface including the opening, and diffusing the opening in the opening by a thermal oxidation method. Forming a second silicon oxide film on the surface of the region, etching the first silicon oxide film and smoothing the upper end of the opening of the silicon oxide film containing boron and phosphorus; Removing the second silicon oxide film, depositing a metal film on the surface including the opening, and selectively etching the metal film to form an electrode in contact with the diffusion region. .

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1 (a) to 1 (e) are sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1 (a), boron ions are selectively implanted into one main surface of the n-type silicon substrate 1 at an acceleration energy of 30 keV and a dose of 5 × 10 ¹⁵ cm ⁻² to perform p-type diffusion. Region 2 is formed. Next, a BPSG film 3 is deposited to a thickness of about 0.7 μm, and the BPSG film 3 on the diffusion region 2 is selectively anisotropically etched to form a contact opening 4.

Next, as shown in FIG. 1B, a non-doped silicon oxide film 5 is formed on the surface including the opening 4 by the CVD method.
Deposit to 30 nm. At this time, the surface temperature of the BPSG film 3 is 400
C., and no out diffusion of impurities occurs.

Next, as shown in FIG. 1 (c), the flow rate of hydrogen is 16 / m
A thermal oxidation process at 900 ° C. is performed in a mixed atmosphere with a flow rate of in and oxygen of 11 / min to oxidize the surface of the diffusion region 2 of the opening 4 through the silicon oxide film 5 to make the silicon oxide film 6 60 nm.
Formed to a thickness of During this oxidation treatment, the diffusion of phosphorus and boron into the diffusion region 2 of the opening 4 can be prevented by the presence of the silicon oxide film 5 on the surface.

Next, as shown in FIG. 1D, the silicon oxide film 5 is removed by hydrofluoric acid-based wet etching. At this time, the silicon oxide film 6 formed by thermal oxidation is also etched. However, since the silicon oxide film 6 is formed as thick as 60 nm and has a lower etching rate than the silicon oxide film 5 formed by the vapor deposition method,
About 30 to 40 nm can be left. Thereafter, a heat treatment is performed for 30 minutes in a nitrogen atmosphere at 900 ° C. to reduce the step of the opening 4.

Next, as shown in FIG. 1 (e), the silicon oxide film 6 is removed by hydrofluoric acid-based wet etching, and the opening 4 is removed.
An aluminum layer is deposited to a thickness of 1 μm on the surface including the above by sputtering, and this is selectively etched to form an aluminum electrode wiring 7.

〔The invention's effect〕

As described above, according to the present invention, the non-doped first silicon oxide film is formed at a relatively low temperature (400 ° C.) on the surface of the BPSG film including the contact opening, and then the surface of the diffusion region of the opening is formed. Is thermally oxidized to form a second silicon oxide film, the first silicon oxide film is removed, and a heat treatment is performed using the remaining second silicon oxide film as a mask to reduce the step of the opening. There is an effect that contamination of the diffusion region due to out diffusion of impurities from the film can be prevented, and variations in contact resistance can be eliminated.

[Brief description of the drawings]

1 (a) to 1 (e) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) show a conventional method of manufacturing a semiconductor device. FIG. 4 is a cross-sectional view of a semiconductor chip shown in the order of steps for explaining the method. 1 .... n-type silicon substrate, 2 .... p-type diffusion region, 3 ....
BPSG film, 4 ... opening, 5, 6 ... silicon oxide film, 7 ...
... aluminum electrode wiring, 8 ... impurity diffusion layer.

Claims (1)

(57) [Claims] 1. A step of selectively providing a diffusion region of the opposite conductivity type on one main surface of a semiconductor substrate of one conductivity type, and selectively providing a silicon oxide film containing boron and phosphorus on a surface including the diffusion region. Providing a contact opening in the diffusion region by etching, depositing a thin first silicon oxide film on a surface included in the opening, and forming a first silicon oxide film on the surface of the diffusion region in the opening by a thermal oxidation method. Depositing a second silicon oxide film, etching the first silicon oxide film and then smoothing the upper end of the opening of the silicon oxide film containing boron and phosphorus; Removing the silicon film, depositing a metal film on the surface including the opening, and selectively etching the metal film to form an electrode in contact with the diffusion region. Method.