JPH027436A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance a gettering effect even in a main part of a semiconductor element by a method wherein the surface of a semiconductor substrate is made partially amorphous, a nitride film is formed on its region and, after that, a heat treatment is executed. CONSTITUTION:Ions of a P-type impurity used to form a base of an npn transistor, an emitter and a collector of a pnp lateral transistor, a resistance and the like are implanted selectively into a surface part of a silicon semiconductor layer 4; after that, the impurity is diffused; then, emitters 16e, 16c of the npn transistor, resistance regions 17, 18, 19, a P-type region forming an electrode of a MIS type capacitor, individual P-type regions 21 constituting an IIL and the like are formed. During this diffusion process, individual isolation layers 12... are made amorphous by implanting the ions of the P-type impurity; a strain caused by a thermal strain by a difference in a coefficient of thermal expansion between an SiN silm 8 and the semiconductor layer 4 is relaxed during a heat treatment. The strain has a strong gettering effect when it is relaxed; it powerfully absorbs a crystal defect and a heavy metal in the neighborhood.

Description

[Detailed description of the invention] The present invention will be described in the following order.

A. Field of industrial application B0 Overview of the invention C9 Prior art 1. Problems to be solved by the invention (A. Field of industrial application) The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device that performs gettering effectively. The present invention relates to a method for manufacturing a device.

(B. Summary of the Invention) The present invention provides a method for manufacturing a semiconductor device that performs gettering, in which the surface of a semiconductor substrate is partially amorphous in order to effectively getter the essential parts of a semiconductor element. The method includes a step of crystallizing, a step of forming a nitride film on a region to be (or has been) amorphized, and a heat treatment step of performing heat treatment after the above two steps are completed.

(C, Prior Art) Gettering, which removes crystal defects and heavy metals in a semiconductor substrate, is necessary to improve the characteristics of a semiconductor device f formed on a semiconductor substrate. As described in Japanese Patent Publication No. 49-40856, by utilizing the gettering effect of a polycrystalline silicon film, a polycrystalline silicon film is formed on a semiconductor substrate, and then heat treatment is performed at a high temperature to form a semiconductor substrate. This was often done by collecting crystal defects and heavy metals inside the polycrystalline silicon film. Of course, the method described in the above publication involves forming a polycrystalline silicon film on the surface of a semiconductor substrate and removing the polycrystalline silicon film after heat treatment; This method forms a polycrystalline silicon film on the back surface of a substrate. Also, instead of polycrystalline silicon film, LP (low pressure) SiN (
In some cases, nitriding (1) is used, and in some cases, gettering is performed by depositing poci3 on the back surface of the semiconductor substrate during the process, or by implanting phosphorus P ions.

Further, as another gettering method, there is a method in which oxygen is injected into the semiconductor substrate (for example, injected at the manufacturing stage of a semiconductor ingot) and gettering is performed using the oxygen.

(D. Problems to be Solved by the Invention) By the way, a gettering method in which a polycrystalline silicon film is formed on the back surface of a semiconductor substrate and gettering is performed by heat treatment has a problem that the gettering effect does not last. This is because, although the heating temperature is set to about 1200° C. in the collector diffusion step when manufacturing a bipolar semiconductor device, if the polycrystalline silicon film is heated to 1100° C. or higher, the gettering effect will almost disappear. As a result, almost no gettering effect can be obtained during the formation of the base and emitter, which have the greatest influence on the characteristics of bipolar transistors, and crystal defects and heavy metals in the main parts of semiconductor devices cannot be effectively removed, which effectively reduces the deterioration of characteristics. It was very difficult to prevent it. This is explained in the above-mentioned Japanese Patent Application Laid-Open No. 49-40
The same applies to the gettering method described in Japanese Patent No. 856, in which a polycrystalline silicon film is formed on the surface of a semiconductor substrate and removed after heat treatment. The same applies to the method of forming.

In addition, the gettering method of pre-depositing POCfL3 on the back surface of the semiconductor substrate during the process has a gettering effect, but since it is a method of pre-deposition in a diffusion furnace, there are difficulties with the furnace tube ring.
There are problems that cannot be ignored, such as the occurrence of dust due to the mist. Further, gettering using a polycrystalline silicon film and gettering using pre-deposition of poci both have the disadvantage that the cost is too large to ignore.

In the gettering method, which involves injecting oxygen into the semiconductor substrate, it is difficult to obtain uniform oxygen concentration.
The reality is that it is difficult to put it into practical use. Furthermore, since oxygen acts as a donor impurity, gettering with oxygen also poses the problem of making it difficult to control the resistivity.

The present invention has been made to solve these problems, and by making it possible to sustainably obtain the gettering effect without incurring a significant cost increase, the present invention can also be applied to the main parts of the conductor element. It is an object of the present invention to produce a semiconductor device such as a bipolar IC with good performance at low cost by exerting a gettering effect.

(E. Means for Solving the Problems) In order to solve the above problems, the method for manufacturing a semiconductor device of the present invention includes a step of partially making the surface of a semiconductor substrate amorphous;
It is characterized by having a step of forming a nitride film on a region to be (or has been) made amorphous, and a heat treatment step of performing heat treatment after these two steps are completed.

(F. Effect) According to the method for manufacturing a semiconductor device of the present invention, the surface of the semiconductor substrate is partially amorphized, and a nitride film is formed on the amorphous (or amorphous) area. As a result, the surface of the semiconductor substrate partially becomes amorphous, and the difference in thermal expansion coefficient between the nitride film and the semiconductor substrate causes large distortions in the amorphous portion, which causes the getter to deteriorate. The core of Then, the strain of the highly strained getter nucleus is relaxed during heat treatment, and when the strain is relaxed, it has a strong gettering effect. and,
The gettering effect can absorb crystal defects and heavy metals in the main parts of the semiconductor device, such as the base and emitter. This is because the getter nucleus is formed on the surface of the semiconductor substrate and is located at the same height as the base and emitter, so it is very close to the base and emitter. Therefore, the gettering effect of the getter nucleus is very effectively exerted on the base and emitter.

Since the getter nucleus can be selectively provided by partially making it amorphous and forming a nitride film there, the getter nucleus can be provided by shifting its position from the semiconductor element or from the main part of the semiconductor element. It is possible to prevent the adverse effects of strain on the semiconductor element or the essential parts of the semiconductor element.

(G, Embodiment) [FIGS. 1 and 2] Hereinafter, a method for manufacturing a semiconductor device of the present invention will be described in detail according to the illustrated embodiment.

FIGS. 1A to 1J are cross-sectional views showing one embodiment of the method for manufacturing a semiconductor device of the present invention in the order of steps.

(A) n+ type scattered layer 2a2 on the surface of the P type semiconductor substrate
b, selectively forming 2C12d. The diffusion layers 2a, 2
b, 2c, and 2d will become buried layers later, and the diffusion layer 2a
is a buried layer for an npn transistor, and the diffusion layer 2b is an npn transistor.
2C is a buried layer for the lateral transistor, 2d is a buried layer for 11L. Said 6 diffusion layer 2a
, 2b, 2c, 2d are Sin, film (film thickness 3300 people) 3
It is formed by diffusion of antimony sb using as a mask. FIG. 1(A) shows the state after the diffusion layers 2a, 2b, 2c, and 2d.

(B) Next, the 5in2 film 3 on the semiconductor substrate 1 is removed, and an n-type silicon semiconductor layer (thickness: 2 μm) 4 is epitaxially grown on the semiconductor substrate 1, as shown in FIG. 2(B).

(C) Next, as shown in FIG. 2C, a 5in2 film 5 having a thickness of 200 mm is formed on the surface of the n-type silicon semiconductor layer 4.

(D) Next, a resist film 6 is selectively formed on the SiO, @s, and the SiO2 film 5 is etched using the resist film 6 as a mask. Specifically, the area corresponding to the area where the isolation layer is to be formed is the window opening 7.7.7.7.
A resist film 6 is selectively formed so that... and the 5i02 film 5 is etched using the resist film 6 as a mask. FIG. 1(D) shows the state of 5totllfi5 after etching.

(E) Next, as shown in FIG. 1(E), a 5iNl15i8 film having a thickness of, for example, about 510 layers is formed on the 5in2 film 5 including the exposed portion of the surface of the semiconductor layer 4 by low pressure CVD. Therefore, the SiN film 8 is the SiO2 film 5.
The etched portion comes into direct contact with the n-type epitaxial growth layer 4. This 5iNl space 8 is formed in order to prevent out-diffusion that causes the isolation to become n-type when forming a P-type isolation layer. It plays the role of causing distortion due to thermal stress in the parts that are in direct contact with the 4-surface.

(F) Next, as shown in FIG. 1(F), a resist film 9 is selectively formed on the surface of the SiN film 8.
Using this as a mask, a P-type impurity 1 such as boron B is added to the surface of the semiconductor layer 4 where an isolation layer is to be formed.
0 is ion implanted. As a result, the ion-implanted portion becomes amorphous.

(G) Next, the portion of the SiN film 8 corresponding to the portion where the n-type region for preventing bunch-through of the lateral transistor is to be formed is removed by photoetching, and the 5iNP7 is removed.
! Using A8 as a mask, n-type impurity 11 is ion-implanted as shown in FIG. 1(G).

(H) Next, for example, at a temperature of 1100°C, impurities 10.1
1 is diffused to form P-type isolation layers 12, 12, . . . and punch-through prevention n as shown in FIG.
A mold diffusion layer 13 is formed. During this diffusion process, distortion occurs in the isolation layers 12, 12, . . . , particularly in the vicinity of the surface, due to thermal stress caused by the difference in coefficient of thermal expansion between the SiN film 8 and the silicon semiconductor layer 4. This strain occurs only in the isolation layers 2a, 2b, 2c, and 2d, and does not occur in the element formation region surrounded by the isolation layers 2a, 2b, and 2C12d.

Thereafter, P-type impurity ions are selectively implanted into the surface of the silicon semiconductor layer 4 to form the base of the npn) transistor, the emitter/collector of the pnp lateral transistor, the resistor, etc. By diffusing npn as shown in Figure 1 (1)
Transistor emitter 16e, 16c1 resistance region 17
．． 18.19, P-type head area 20 forming the electrode of MIS type capacitor, each P-type head area 21.21.21 forming IIL
．． 21 etc. is formed. In this diffusion step, not only the base 15 of the npn transistor is formed, but also the isolation layers 12, 12, . . . are made amorphous by ion implantation of P-type impurities, Strain caused by thermal stress due to the difference in thermal expansion coefficient between the semiconductor layers 4 is relaxed during heat treatment at a temperature of 1100°C. When the strain is relaxed, it has a strong gettering effect and strongly absorbs nearby crystal defects and heavy metals. Therefore, the isolation layer 12.12
, . . . The main parts (for example, the base, emitter, etc.) of each semiconductor element surrounded by the elements have improved crystallinity and are free of heavy metals.

Furthermore, after that npn) - the emitter of the transistor, pn
Selective ion implantation of n-type impurities is performed to form the base extraction region (ohmic contact region) of the p lateral transistor, and then, for example, 110
By diffusing at a temperature of 0°C, as shown in FIG. Form.

In this step as well, the isolation layer 1 is formed by heat treatment.
2.12, ... is relaxed, but it also has a gettering effect and strongly absorbs nearby crystal defects and heavy metals. Therefore, the isolation layer 12.12,
The main part of each semiconductor element surrounded by..., for example n
The crystallinity of the base, emitter, etc. of the pn transistor is further improved, and a semiconductor element with very high performance can be obtained.

In the manufacturing method of the present semiconductor device, the surface of the conductive layer 4 is exposed by etching the portion where the isolation layer of 5 to 2 nm is to be formed, which is formed entirely on the surface of the semiconductor layer 4, and then the SiN film is etched. 8, so that thermal stress is generated in the part where the isolation layer is to be formed when heat treatment is performed, and then impurity ions are implanted to form the isolation layer in the part where the isolation layer is to be formed. After that, heat treatment for impurity diffusion to form an isolation layer, heat treatment for diffusion to form a base, and heat treatment for diffusion to form an emitter are performed. Distortion with a gettering effect occurs on the surface.

Therefore, each semiconductor element is surrounded by a strained isolation layer that has a gettering effect.
As a result, crystal defects on the surface and in the vicinity of the semiconductor At-, which are essential parts, are absorbed by the isolation layer. This gettering effect can be obtained both in the base formation stage and in the emitter formation stage.

The generation of strain within the isolation layer, especially on its surface, due to thermal stress is a sin.

This can be done by forming an SiN film 8 for out-diffusion prevention on the surface of the semiconductor substrate on which the film 5 is selectively formed, and the isolation layer can be prevented from becoming amorphous and causing distortion. This can be done by implanting ions of impurities necessary for formation. Therefore, the gettering effect can be obtained without needlessly increasing the number of steps.

By the way, in the above embodiment, the surface of the portion of the semiconductor layer 4 where the isolation layer is to be formed is exposed and the Si layer is formed.
After forming the N film 8, impurity ions were implanted for amorphous conversion and isolation layer formation.

However, the order may be reversed. FIGS. 2(A) to 2(C) show such an embodiment in the order of steps,
As shown in FIG. 4A, a SiO2 film 5 is formed entirely on the surface of the semiconductor layer 4, and a resist film 6 is formed on the 5in2 film 5.
is selectively formed and impurity ions are implanted using the resist film 6 as a mask, thereby introducing an impurity 10 for forming an isolation layer only into a portion of the surface of the semiconductor layer 4 where an isolating layer is to be formed. Next, 5i02k
The surface of the semiconductor layer 4 is exposed by etching the portion where the isolation layer is to be formed, and then a SiN film 8 is formed as shown in FIG. For example, the isolation layer 12 is formed by diffusion at a temperature of 1100° C. as shown in FIG. The fact that gettering is performed on the surface is the same as in the embodiment shown in FIG.

(H, Effects of the Invention) As described above, the method for manufacturing a semiconductor device of the present invention is as follows:
A method characterized by comprising a step of partially amorphizing the surface of a semiconductor substrate, a step of forming a nitride film on the region to be (or has been) amorphized, and a step of performing heat treatment. It is.

Therefore, according to the method for manufacturing a semiconductor device of the present invention, it is possible to partially form a strain for gettering on the surface of a semiconductor substrate, and when forming a semiconductor element, especially a main part thereof, the strain causes the semiconductor element to be damaged. In particular, it can absorb crystal defects and heavy metals in the main parts.

The strain can be selectively created by partially amorphizing the semiconductor substrate and forming a nitride film on the surface of the semiconductor substrate. By shifting, it is possible to prevent the adverse effects of strain from reaching the semiconductor element or its essential parts.

FIGS. 2A to 2C are cross-sectional views showing another embodiment of the method for manufacturing a semiconductor device of the present invention in the order of steps.

Explanation of symbols 1.4...Semiconductor substrate, 8...Nitride film.

[Brief explanation of the drawing]

Claims (1)

[Claims] (1) It is characterized by comprising the steps of: partially making the surface of the semiconductor substrate amorphous; forming a nitride film on the region to be made amorphous; and performing heat treatment. Manufacturing method of semiconductor device