JPH065786A - Fabrication of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress level difference at the side wall part of a resistor formed of poly-Si and to obviate the necessity of high temperature heat treatment. CONSTITUTION:The method for fabricating a semiconductor device comprises a step for forming a first insulation film 2 on a semiconductor substrate 1 and then forming a second insulation film 3 having etching selectivity with the first insulation film 2 thereon, a step for removing the second insulation film 3 selectively from parts for forming resistors by etching, a step for forming a poly-Si film 4 on the entire surface and introducing impurities therein in order to achieve required conductivity, and a step for forming a mask 5 on the poly-Si film at the resistor forming parts and removing the poly-Si film 4 selectively by etching through the use of the mask 5, wherein the poly-Si film 4 being left after etching is constituted as a resistor 10.

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 resistor formed of polycrystalline silicon (hereinafter, simply referred to as a resistor).

[0002]

2. Description of the Related Art An example of a conventional method of manufacturing a resistor of this type is shown in FIG. First, as shown in FIG. 3A, a base insulating film 2 is formed on a silicon substrate 1, and a polycrystalline silicon film 4 is formed on the entire surface. After doping the polycrystalline silicon film 4 with impurities such as arsenic and phosphorus by ion implantation,
As shown in (b), the polycrystalline silicon film 4 is selectively etched by photolithography to form the resistor 10. Next, as shown in FIG. 3C, after forming a protective insulating film 6 for protecting the resistance 10, the resistance contact hole 7 is opened by photolithography, and finally the resistance 10 is passed through the resistance contact hole 7. Forming an electrode 8 connected to.

Another manufacturing method is shown in FIG. Figure 4
As shown in (a), after forming the base insulating film 2 on the silicon substrate 1 and forming the resistor 10 with the polycrystalline silicon film,
As shown in Fig. 4 (b), SOG (Spin On Glass) is formed on the entire surface.
11 is applied and heat-treated at about 900 ° C., and then SOG 11 is etched back until the surface of the polycrystalline silicon resistor 10 is exposed. As a result, the SOG 11 has a resistance of 10
Is left only on the side wall of the resistor 10 and alleviates the step of this part of the resistor 10. Next, as shown in FIG. 4C, a protective insulating film 6 is formed on the entire surface, and a resistance contact hole 7 and an electrode 8 are formed.

[0004]

Among the conventional methods of manufacturing a resistor described above, in the method shown in FIG. 3, the thickness of the polycrystalline silicon film 4 for forming the resistor 10 is the same as that of the protective insulating film 6. If it is thicker than the film thickness of, the angle of the side wall portion of the resistor 10 becomes steep. For this reason, in the electrode formation step, when a metal film of aluminum, gold, or the like is formed on the entire surface by sputtering and the metal film other than on the resistance contact hole is selectively removed by reactive ion etching, the polycrystalline film is used. There is a problem that metal remains on the side wall portion of the silicon resistor, which causes a short circuit defect or the like.

Further, in the method shown in FIG. 4, since the SOG 11 is left on the side wall portion of the resistor 10 to mitigate the step, the problem of metal remaining as described above can be solved, but in the processing of SOG. Since it is necessary to perform heat treatment at a high temperature, for example, in the case of a bipolar IC, there is a problem that it adversely affects the impurity concentration profile of the already formed base diffusion layer and deteriorates the characteristics of the transistor. It is an object of the present invention to provide a method of manufacturing a semiconductor device that alleviates the step difference on the side wall portion of the resistor and does not require heat treatment at high temperature.

[0006]

According to the present invention, a step of forming a first insulating film on a semiconductor substrate, and forming a second insulating film having etching selectivity with the first insulating film on the first insulating film And a step of selectively etching away the second insulating film where a resistor is formed, a step of forming a polycrystalline silicon film on the entire surface, and introducing impurities into the polycrystalline silicon film to give a required conductivity. A step of forming a mask on the portion of the polycrystalline silicon film where the resistance is to be formed, and using the mask to selectively remove the polycrystalline silicon film by etching.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention in the order of manufacturing steps. First, as shown in FIG. 1A, the silicon substrate 1
A first insulating film 2 as a base insulating film and a second insulating film 3 having etching selectivity with respect to the first insulating film are formed thereover. Then, the second insulating film 3 is selectively etched by a photolithography technique, and the second insulating film 3 is etched only in a portion where a resistance of polycrystalline silicon is formed.

Next, as shown in FIG. 1 (b), a polycrystalline silicon film 4 having the same thickness (1000Å to 3000Å) as the second insulating film 3 is grown on the entire surface, and arsenic and phosphorus are deposited on the polycrystalline silicon film 4. Etc. are doped using ion implantation. Further, a photoresist 5 is applied on it. Then, the mask used for the selective etching of the second insulating film 3 is reused to
The photoresist 5 is selectively left on the region where the insulating film 3 is removed by etching, that is, on the region where the resistor is formed.

Next, as shown in FIG. 1C, the polycrystalline silicon film 4 is isotropically etched by using the remaining photoresist 5 as a mask until the first insulating film 2 is exposed to form a resistor 10. To do. Then, the photoresist 5 is removed. As a result, the formed resistor 10 is also etched by side etching near the edges of the photoresist 5 for isotropic etching, and as a result, the cross-sectional shape of the resistor is a film having substantially the same plane as the second insulating film 3. Formed into a shape. Thereafter, as shown in FIG. 1D, an insulating film 6 for resistance protection is formed on the entire surface, a resistance contact hole 7 is opened, and then an electrode 8 connected to the resistance 10 through the resistance contact hole 7 is formed.

Therefore, according to this manufacturing method, the resistor 10 formed of the polycrystalline silicon film 4 has the second insulating film 3
Since it is formed in the etched region, the side wall thereof is covered with the second insulating film 3 having the same thickness. Therefore, the step on the side wall of the resistor 10 is almost eliminated,
There is an effect of preventing a short circuit defect or the like due to the metal remaining on the side wall of the resistor resulting from this.

FIG. 2 is a sectional view showing a second embodiment of the present invention in the order of manufacturing steps. First, as shown in FIG. 2A, the first insulating film 2 and the second insulating film 3 are formed on the silicon substrate 1 in the same manner as in the first embodiment, and the first portion of the portion where the resistance is formed is formed. The second insulating film 3 is selectively etched to form a polycrystalline silicon film 4 and perform ion implantation. Next, FIG.
As shown in (b), some dimensions from the end of the second insulating film 3
Here, a photoresist 5 covering the polycrystalline silicon film 4 is formed in a region inside about 500 to 1000 Å.
Subsequently, about 1/3 of the film thickness of the polycrystalline silicon film 4 is anisotropically etched by reactive ion etching. Further, as shown in FIG. 2C, the remaining polycrystalline silicon film 4 is removed by isotropic etching. Then, the photoresist 5 is removed.

Finally, as shown in FIG. 2D, the insulation film 6 for resistance protection and the electrode 8 are formed in the same manner as in the first embodiment. In this embodiment, by adjusting the distance between the second insulating film 3 and the photoresist 5 or the ratio of anisotropic etching with respect to the polycrystalline silicon film 4, the protrusion 9 left on the polycrystalline silicon is adjusted. It is also effective in reducing steps.

[0013]

As described above, after the resistance forming portion of the second insulating film formed on the first insulating film is selectively etched, a polycrystalline silicon film is grown on this portion. By selectively etching the polycrystalline silicon film other than the resistive portion, the polycrystalline silicon film left in the etched portion of the second insulating film can be configured as a resistor. As a result, the side wall portion of the resistor can be covered with the second insulating film, the step at the side wall portion can be eliminated, and there is an effect that a short circuit defect or the like due to metal residue caused by this can be prevented. Further, since the high temperature process is not required, the characteristics of the transistor are not deteriorated.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a sectional view showing a second embodiment of the present invention in the order of manufacturing steps.

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

FIG. 4 is a cross-sectional view showing a second conventional method in the order of manufacturing steps.

[Explanation of symbols]

 1 Silicon Substrate 2 First Insulating Film 3 Second Insulating Film 4 Polycrystalline Silicon Film 5 Photoresist 6 Protective Insulating Film 10 Resistor

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[Procedure amendment]

[Submission date] March 2, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 3]

[Figure 4]

[Figure 1]

[Fig. 2]

Claims (1)

[Claims] 1. In a semiconductor device having a resistance formed of polycrystalline silicon, a first insulating film is formed on a semiconductor substrate, and a second insulating film having etching selectivity with the first insulating film is formed on the first insulating film. A step of forming an insulating film, a step of selectively etching away the second insulating film in a portion where a resistance is formed, a polycrystalline silicon film is formed on the entire surface, and impurities are introduced into the polycrystalline silicon film to obtain a desired conductivity. And a step of forming a mask on a portion of the polycrystalline silicon film where a resistor is to be formed, and using the mask to selectively etch away the polycrystalline silicon film. A method of manufacturing a semiconductor device, comprising: forming a polycrystalline silicon film left in an etched portion as a resistor.