JP2919218B2 - 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 a method of manufacturing a semiconductor device having a resistance element formed by introducing impurities into a semiconductor substrate.

[0002]

2. Description of the Related Art An example of a conventional technique for forming two types of resistance elements having different sheet resistances in a method of manufacturing a semiconductor device will be described with reference to FIG.

First, as shown in FIG. 2A, a silicon oxide film 2a having a thickness of several tens nm is formed on the surface of an N-type semiconductor substrate 1 by thermal oxidation, and thereafter, a third resistor is formed by a known photolithography technique. A photoresist 3a is formed on the silicon oxide film 2a so as to open a region where an element is to be formed, and then a third resistance element region 4c is formed by ion-implanting boron which is a P-type impurity.

[0004] Next, as shown in FIG.
By performing the same process as the formation of the resistance element region 4c,
The fourth resistance element region 4d is formed. At this time, the implantation amount of boron for ion implantation into the third resistance element region 4c and the fourth resistance element region 4d is freely selected so as to obtain a desired sheet resistance.

Next, heat treatment is performed as shown in FIG.
By activating the impurities, two types of resistance elements having different sheet resistances are formed.

[0006]

In the above-mentioned prior art, the same photolithography step and ion implantation step are repeated twice to form two types of resistance elements having different sheet resistances. Therefore, there is a problem that the number of steps increases, the manufacturing cost increases, and the manufacturing period becomes longer.

An object of the present invention is to manufacture a semiconductor device capable of simultaneously forming diffusion resistance elements having different sheet resistances without providing separate diffusion steps in forming resistance elements having two or more different sheet resistances. It is to provide a method.

[0008]

According to a method of manufacturing a semiconductor device of the present invention, an impurity of a second conductivity type is introduced into a semiconductor substrate of a first conductivity type, and the semiconductor substrate has two or more different sheet resistances. In a method of manufacturing a semiconductor device for forming a resistance element, a step of selectively introducing the impurity into the semiconductor substrate to form a resistance element region, and covering the resistance element region with a film formed by a CVD method. Forming a resistive element region and a resistive element region that does not cover the resistive element region with a film formed using the CVD method;
Thermally oxidizing the semiconductor substrate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a semiconductor device shown in the order of steps for explaining an embodiment of the present invention.

[0010] First, as shown in FIG. 1 (a), a silicon oxide film 2a of 20~50nm by thermal oxidation on the impurity concentration is 10 ¹⁴ ~10 ¹⁶ cm ^-3 of N-type semiconductor substrate 1 of the surface, Thereafter, a photoresist 3a is formed on the silicon oxide film 2a by a well-known photolithography technique so as to open the first resistance element formation region and the second resistance element formation region, followed by boron as a P-type impurity. With acceleration energy of 20 keV to 50 keV and dose of 10 ¹² to 1
Ion implantation is performed at 0 ¹⁴ cm ^-2 to form a first resistance element region 4a and a second resistance element region 4b.

Next, after a polycrystalline silicon film having a thickness of 150 to 1000 nm is grown on the silicon oxide film 2a by the low pressure CVD method, as shown in FIG.
Patterning is performed so that the polycrystalline silicon film 5 remains on a. At this time, the polycrystalline silicon film on second resistance element region 4b is removed.

Next, after removing the silicon oxide film 2a as shown in FIG. 1C, the surfaces of the semiconductor substrate 1 and the polycrystalline silicon film 4 are thermally oxidized as shown in FIG.
A 0-100 nm silicon oxide film 2b is formed. At this time, the silicon oxide film 2a is formed on the first resistance element region 4a.
And the polycrystalline silicon film 5, the first resistance element region 4a
Is not thermally oxidized, but since there is no such film on the second resistance element region 4b, boron is thermally oxidized on the second resistance element region 4b and boron ion-implanted into the second resistance element region 4b is a silicon oxide film. 2b, the second resistance element region 4
The amount of impurities of b decreases.

Subsequently, as shown in FIG.
By performing a heat treatment at about 1000 ° C. to activate the impurities in the first resistance element region 4a and the second resistance element region 4b, a resistance element having a desired sheet resistance is formed.

In the resistance element thus formed, the sheet resistance of the first resistance element region 4a is about 2 KΩ / □, while the sheet resistance of the second resistance element region 4b is taken into the silicon oxide film 2b. Since the impurity concentration is reduced by the amount of about 4.5 KΩ / □, the first resistance element region 4
The value is more than twice as high as the sheet resistance a.

In this case, the sheet resistance of the first resistance element region 4a can be freely changed depending on the amount of boron to be ion-implanted, and the sheet resistance of the second resistance element region 4b can be freely changed by changing the thermal oxidation conditions. Can be changed.

The film formed by the CVD method may be any film other than a polycrystalline silicon film, as long as the film is hardly oxidized such as a nitride film.

[0017]

As described above, according to the present invention, the thermal oxidation is performed after forming the resistive element region having the film for preventing thermal oxidation and the resistive element region having no film on the resistive element region. The resistance element region is thermally oxidized, and impurities in the resistance element region are taken into the thermal oxide film, so that the impurity concentration decreases and the sheet resistance increases. Therefore, by this method,
In one photolithography process and one ion implantation process, two types of resistors having different sheet resistances can be formed at the same time, and the number of processes can be reduced.

As the film for preventing thermal oxidation used in the present invention, a CVD film used for a gate electrode or an emitter electrode of a normal semiconductor device can be used. The number of steps can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device shown in the order of steps for explaining one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor device shown in a process order for explaining an example of a conventional technique.

[Description of Signs] 1 Semiconductor substrate 2a, 2b Silicon oxide film 3a, 3b Photoresist 4a First resistance element area 4b Second resistance element area 4c Third resistance element area 4d Fourth resistance element area 5 Polycrystalline silicon film

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising: introducing a second conductivity type impurity into a first conductivity type semiconductor substrate to form resistance elements having two or more different sheet resistances on the semiconductor substrate. Forming a resistive element region by selectively introducing the impurity into a substrate; and forming a resistive element region covering the resistive element region with a film formed using a CVD method and a film formed using the CVD method. A method of manufacturing a semiconductor device, comprising: a step of forming another resistance element region that does not cover the resistance element region; and a step of thermally oxidizing the semiconductor substrate thereafter.