JPH0917952A - Semiconductor integrated circuit and manufacture thereof - Google Patents

Abstract

PURPOSE: To make it possible to form a resistor having no temperature characteristic without variation by diffusing impurities with which polysilicon is doped in a semiconductor layer through a slit to form a diffusion resistance region. CONSTITUTION: A slit 12 is formed in part of an insulating layer 11 on a semiconductor layer 10 to expose the semiconductor layer 10. A polysilicon layer 14 is formed which extends from the portion of the insulating layer 11 on one side of the slit 12 to the portion of the insulating layer 11 on the other side, covering the slit 12. Impurities in the polysilicon layer 14 are diffused in the semiconductor layer 10 through the slits 12 to form a diffusion resistor 18. This makes it possible to virtually determine the characteristics of the diffusion resistor only according to the impurity concentration of the polysilicon. Since the characteristics of the diffusion film can be determined only according to the condition of the polysilicon film, as mentioned above, it is possible to control variations and thus obtain a resistor having no temperature characteristic without variation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit containing a poly-Si resistor and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, an IC generates a voltage for detecting a current. And a resistor is built in for generating a voltage. However, since the diffusion resistor and the poly-Si resistor each have a temperature characteristic, it is not possible to realize a resistor with accuracy that is not affected by temperature by itself.

On the other hand, the diffusion resistance has a positive temperature characteristic of 0.1 to 0.3 percent / degree, and the poly-Si resistance is
Since they have a negative temperature characteristic of 0.03 to 0.17 percent / degree, an attempt was made to combine them to compensate for the temperature characteristic. This is, for example, in JP-A-6
No. 0-128651 and its structure is shown in FIG.

Reference numeral 1 is an N-type epitaxial layer laminated on a P-type semiconductor substrate, in which a P-type diffusion region 2 is formed, and a poly-Si film 5 is formed via insulating films 3 and 4. . Here, 3 is a Si oxide film, and 4 is a Si nitride film. Further, an aluminum electrode 7 is provided via the insulating layer 6. Therefore, since the diffusion resistance having a positive temperature coefficient and the poly-Si having a negative temperature characteristic are connected in parallel, a resistor having a small temperature coefficient can be realized.

[0005]

However, the diffusion resistance is caused by ion implantation or impurity deposition by using poly S.
The characteristics are determined to some extent before the formation of the i-resistor. Further, the poly-Si resistor covers the insulating film after the diffusion resistor is formed, forms poly-Si on the insulating film, and thereafter determines the characteristics by ion implantation or impurity deposition.

Therefore, the diffusion resistance is due to the formation of the insulating films 3 and 4.
There is a problem in that the characteristics do not reach the desired values due to the addition of heat or the like due to the formation of the poly-Si5, and the characteristics of the poly-Si also do not reach the desired values due to variations in the state of impurities. Further, in the entire resistor, there is a problem that the diffusion resistance and the variation of the poly-Si resistor interact with each other to make it difficult to obtain desired characteristics.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. First, a part of an insulating layer on a semiconductor layer is opened to expose the semiconductor layer, and the opening. A poly-Si layer which covers the opening from one insulating layer around the portion and extends to the other insulating layer.
A resistor composed of an i layer, and the poly-Si through the opening.
This is solved by forming a resistor with a diffusion resistor formed by diffusing impurities in the layer.

Secondly, the problem is solved by making the opening equal to or smaller than the width of the poly-Si resistor. Thirdly, the polysilicon resistor has a negative temperature characteristic, the diffusion resistor has a positive temperature characteristic, and the resistor has a substantial temperature characteristic of zero.

Fourthly, a step of exposing a part of the insulating layer on the semiconductor layer to expose the semiconductor layer, and a step of passing from one insulating layer around the opening while covering the opening. Extending a polysilicon layer to the other insulating layer,
It is solved by providing a step of diffusing impurities introduced into the polysilicon layer into the semiconductor layer, and a step of connecting both ends of a polysilicon resistor having the polysilicon layer as a resistor to an IC circuit. is there.

[0010]

First, by providing the opening under the poly-Si layer, a diffusion region can be formed in the semiconductor layer through the opening. Further, the impurity of poly-Si is diffused and the value of the diffusion resistance and the temperature characteristic are determined. That is, if other conditions such as the thermal diffusion temperature are properly grasped and the same conditions are set, the diffusion resistance value is determined only by the impurity concentration of the substantial poly-Si. That is, condition 1 for the poly-Si film
Since the diffusion film can be determined by one, the variation can be suppressed. Conventionally, the introduction of impurities into the diffusion resistance is performed by using poly-Si.
This diffusion region is provided before the formation and also when the poly-Si is formed, the diffusion region affects the characteristics of the diffusion resistance due to heat. However, in the present invention, the characteristic of the diffusion resistance is determined only by the impurity concentration of the substantial poly-Si. Therefore, it is easier to obtain desired characteristics as compared with the conventional one.

Second, when the opening is designed to be larger than the pattern of poly-Si, the diffusion region has a region in which impurities are diffused and a region in which impurities are not diffused.
In the area outside the pattern, the surface is etched during the pattern etching of poly-Si, and it is difficult to obtain desired characteristics.However, the present invention solves this problem because the opening is smaller than the poly-Si pattern. Easy to obtain characteristics.

Thirdly, the polysilicon resistor has a negative temperature characteristic and the diffused resistor has a positive temperature characteristic.
In addition, since each resistor easily obtains a desired resistance value as described above, the resistor can have a substantial temperature characteristic of zero, and a highly accurate circuit can be realized. 4th
A step of exposing a part of the insulating layer on the semiconductor layer to expose the semiconductor layer; and from one insulating layer around the opening to the other insulating layer passing through while covering the opening. A step of extending the polysilicon layer, a step of diffusing impurities introduced into the polysilicon layer into the semiconductor layer, and both ends of the polysilicon resistor having the polysilicon layer as a resistor are connected to an IC circuit. By including the step, since it is possible to form while using the poly-Si forming step without going through the diffusion resistance diffusion step in advance, the number of steps can be reduced, and the variation can be reduced by that amount. Can be realized with high accuracy.

[0013]

[Examples] The semiconductor integrated circuit of the present invention will be described in detail below. FIG. 1 shows only a resistor which is a part of this integrated circuit, and FIG. 2 is a sectional view taken along the line AA. First, as shown in FIG. 1, there is a semiconductor layer 10. The semiconductor layer referred to here is, as described in the conventional example, an N-type epitaxial layer (bipolar IC) laminated on a P-type substrate.
Substrate), or a P substrate or N substrate used for Bi-CMOS or MOS.

An insulating film 11 is formed on the semiconductor layer 10. This insulating film 11 may be a thermal oxide film, a chemical vapor deposition method or a LOCOS oxide film. Here, LO
It is shown by a COS oxide film. The insulating film 11 has an opening 1 where the semiconductor layer 10 is exposed, as shown by the alternate long and short dash line in FIG.
2 are provided. As shown in Figure 2, the insulating film is LOCOS
If it is an oxide film, the place where this LOCOS oxide film terminates in the semiconductor layer corresponds to the opening in FIG. here,
For example, since the Si nitride film 13 is formed on the LOCOS oxide film, the etching area of this Si nitride film corresponds to the opening. If it is an insulating film other than the LOCOS oxide film, the opening is formed by etching. Said S
The i-nitride film serves as a shielding film for preventing the impurities trapped in the oxide film 11 from being re-diffused into the poly-Si 14 in the present invention.

The opening 12 is completely covered with a patterned poly-Si resistor 14, which will be described later. Further, the shape of the opening is an elongated shape depending on the resistance value, and in the case of a high resistance value, a shape such as meandering that is adopted in a normal IC is possible. In either case, the opening is completely covered, and the poly-Si resistor 14 has a certain length from both ends of the opening.
Are formed.

Further, an insulating film 15 is further coated on the poly-Si resistor 14, and for example, the uppermost wiring (for example, A
(l wiring) 16 and 17 are electrically connected to the poly-Si resistor 14 through the contact holes indicated by X. Naturally, the other ends of the Al wirings 16 and 17 are in contact with other wirings, elements, etc. to configure the circuit of this IC. Therefore, the equivalent circuit of this resistor is as shown in FIG. Rd is
It is a diffusion resistance, and Rp is a poly-Si resistor. That is, the poly-Si resistors that are in contact with the diffusion resistor 18 are equivalently connected in parallel, and the poly-Si resistors are connected in series at both ends.

A feature of the present invention is that the impurity doped in poly-Si is diffused into the semiconductor layer through the opening to form a diffusion resistance region 18 as shown in FIG. Conventionally, in order to form a diffusion resistance, an impurity depot (or ion implantation) for diffusion resistance and a heat treatment for diffusion (hereinafter referred to as diffusion resistance treatment) are required. ) And a heat treatment for diffusion (hereinafter referred to as poly-Si resistance treatment) were required. Therefore, due to variations in diffusion resistance treatment and variations in poly-Si resistance treatment, there is a variation in the overall resistance value, and at the same time, there is a variation in resistance value due to the interaction of these two processes, and it is very difficult to control when actually making an IC. Although problematic, the present invention is essentially determined by the concentration of impurities that are doped into the poly-Si due to the openings. Therefore, since there is no diffusion resistance treatment as in the conventional example, it is possible to minimize variations in resistance value.

Further, in FIG. 1, by providing the separation distances a and b between the opening 12 and the contact, an equivalent circuit as shown in FIG. 3 can be achieved. In other words, the two resistors connected in parallel are adjusted so as to have a slightly positive temperature characteristic, and this positive temperature characteristic can be relatively easily adjusted by compensating with poly-Si having negative temperature characteristics at both ends. . If the opening 12 is designed to be larger than the pattern of poly-Si, the diffusion region has a region in which impurities are diffused and a region in which impurities are not diffused. The surface of the diffused region protruding to the surface is etched during the pattern etching of poly-Si, and it is difficult to obtain desired characteristics.However, the present invention solves this problem because the opening is smaller than the poly-Si pattern. Easy to obtain characteristics. Here, the diffusion region diffused from the opening by the heat treatment is laterally diffused, but it is necessary to set such that the diffused diffusion region does not jump out from the poly-Si resistor.

The structure of the resistor of the present invention has been described above, and a simple manufacturing method thereof will be described below. First, LOCOS is formed by utilizing the Si nitride film which is an oxidation resistant film, and L
The opening 12 is formed by removing the Si oxide film and the Si nitride film between OCOS. In addition, if necessary, a Si nitride film is attached to the region other than the opening, and a poly-Si pattern is formed so as to cover the opening.

Since the resistivity of the patterned poly-Si film is too low by the impurity deposition, impurities are introduced into the poly-Si by ion implantation. For example, phosphorus, which is an impurity, is injected at a dose amount of about 10 16 to obtain about 1
A specific resistance of about 100 ohms / square can be obtained in one hour at 000 degrees. Then, a contact is opened through the insulating film 15 and electrically connected to the wirings 16 and 17 of the IC through this contact.

That is, since it is possible to form the poly-Si without using the diffusion resistance process in advance while utilizing the process of forming poly-Si, the number of steps can be reduced and the variation can be reduced accordingly, so that a desired value can be accurately achieved.

[0022]

As is clear from the above description, the first
By providing the opening in the insulating film below the poly-Si layer, the impurity of poly-Si can be diffused into the semiconductor layer through the opening. That is, the impurity of poly-Si is diffused, and the value of the diffusion resistance and the temperature characteristic are determined. That is, if other conditions such as the thermal diffusion temperature are properly grasped and the same conditions are set, the diffusion resistance value is determined only by the impurity concentration of the substantial poly-Si. That is, since the diffusion film can be determined by one condition of the poly-Si film, the variation can be suppressed. Therefore, by utilizing the poly-Si and the diffusion resistance, it is possible to achieve resistance without temperature characteristics without variation.

Second, if the opening is designed to be larger than the pattern of poly-Si, the diffusion region has a region in which impurities are diffused and a region in which impurities are not diffused.
The outer surface of the poly-Si pattern is etched during the pattern etching of, and it is difficult to obtain desired characteristics.
In the present application, since the opening is smaller than the poly-Si pattern, this problem is solved and the desired characteristics are easily obtained.

Thirdly, the polysilicon resistor has a negative temperature characteristic and the diffusion resistor has a positive temperature characteristic.
In addition, since each resistor easily obtains a desired resistance value as described above, the resistor can have a substantial temperature characteristic of zero, and a highly accurate circuit can be realized. 4th
In addition, since the formation can be performed by using the poly-Si forming process without the diffusion resistance diffusion process in advance, the number of processes can be reduced and the variation can be reduced accordingly, so that a desired value can be accurately achieved.

[Brief description of the drawings]

FIG. 1 is a plan view of a semiconductor integrated circuit of the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG.

3 is an equivalent circuit diagram of the resistor of FIG.

FIG. 4 is a diagram illustrating a resistor.

FIG. 5 is a sectional view of a conventional resistor.

6 is an equivalent circuit diagram of FIG.

Claims (4)

[Claims] 1. An insulating layer formed on a semiconductor layer, an opening in which a part of the insulating layer is opened to expose the semiconductor layer, and one insulating layer around the opening, And a poly-Si layer covering the opening and extending to the other insulating layer, wherein a resistor made of the poly-Si layer is formed by diffusing impurities in the poly-Si layer through the opening. A semiconductor integrated circuit comprising a diffusion resistor and a resistor. 2. The semiconductor integrated circuit according to claim 1, wherein the opening is equal to or smaller than the width of the poly-Si resistor. 3. The semiconductor integrated circuit according to claim 1, wherein the polysilicon resistor has a negative temperature characteristic and the diffusion resistance has a positive temperature characteristic, and the resistor has a substantial temperature characteristic of zero. 4. A step of exposing a part of an insulating layer on a semiconductor layer to expose the semiconductor layer, and a step of passing one insulating layer around the opening while covering the opening and the other. A step of extending a polysilicon layer to an insulating layer; a step of diffusing impurities introduced into the polysilicon layer into the semiconductor layer; and an IC circuit having both ends of the polysilicon resistor having the polysilicon layer as a resistor. And a step of connecting to the semiconductor integrated circuit.