JPH077008A - Semiconductor device manufacturing method - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a semiconductor device effi ciently. CONSTITUTION:In a process for manufacturing a semiconductor device, silicon oxide film 2 is formed on both surfaces of a substrate 1 (Fig. B) and the silicon oxide film 2 on a reverse side is eliminated by etching (Fig. C). After the elimination, silicon nitride film is formed on both surfaces of the substrate (Fig. D). Since a reverse side silicon oxide film 60 is directly formed on the substrate 1, strains HS30 and HS40 are generated at the interface of both films and then the impurity within the substrate 1 for relaxing the strain generated at the interface is trapped by the strains HS30 and HS40 with gettering. The gettering is accelerated by heat treatment to be performed later. Since the gettering is performed during the manufacturing process of the semiconductor device. it is not necessary to perform gettering process separately. thus manufacturing the semiconductor device efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to improving the efficiency thereof.

[0002]

2. Description of the Related Art Generally, a semiconductor device is formed on a thin substrate called a wafer. A substance of high purity (eg, silicon) is used for this substrate, but a small amount of impurities (Fe, Na, etc.) remain in the substrate. In order to remove such impurities and improve the performance of the semiconductor device, there is a technique of forming a film on a substrate and trapping the impurities in the strain of the interface formed between the substrate and the film. This technique is called gettering, and giving a gettering function from outside the substrate is called EG (Extrinsic Gettering).

The gettering mechanism and specific examples will be described below. A polysilicon film 20 is formed on the front and back surfaces of the substrate 1 shown in FIG. 8A by, for example, the CVD method (FIG. 8B). A schematic view showing the particles 10 of the formed polysilicon film 20 is shown in FIG. 5A. Only the front surface side of the substrate 1 of the formed polysilicon film 20 is removed by etching, and the polysilicon film 20 on the rear surface side of the substrate 1 is left (FIG. 8).
C).

Here, the polysilicon particles 10 shown in FIG. 5A grow during the manufacturing process of the semiconductor device and become as shown in FIG. 5B. When the polysilicon particles grow, strain occurs on the wafer side HS1 between the polysilicon particles 10 and on the wafer interface HS2 with the polysilicon film 20 (FIG. 5).
B). In order to alleviate this strain, impurities (Fe,
Na and the like) are trapped in the strains HS1 and HS2. Thus, strains HS1 and HS2 are generated at the interface between the polysilicon film 20 left on the back surface side of the substrate 1 and the substrate, and impurities in the substrate 1 are trapped. Further, by performing heat treatment on the substrate 1 on which the polysilicon film 20 is formed, the impurities in the substrate 1 are trapped at the locations where the above strain occurs.

Usually, gettering is performed at the time of manufacturing a wafer, that is, before manufacturing a semiconductor device, and the substrate after the gettering is used for manufacturing a semiconductor device.
Therefore, gettering and semiconductor manufacturing processes in wafer manufacturing are always performed separately.

Here, a conventional semiconductor device manufacturing method will be described. A silicon oxide film 2 is formed on both surfaces of the substrate (FIG. 6A) on which the gettering described above is completed by thermal oxidation.
Are formed (FIG. 6B). Next, the surface silicon oxide film 2
A silicon nitride film 3 is formed on it (FIG. 6C). A resist 18 is formed on the formed silicon nitride film 3, and boron is ion-implanted into the substrate 1 using the resist 18 as a mask (FIG. 6D). After the ion implantation, the silicon nitride film 3 is removed by etching (FIG. 7A).

After the silicon nitride film 3 is removed by etching, the resist 18 is removed and the substrate 1 is thermally oxidized to form a field oxide film (element isolation region) 30. When this element isolation region 30 is formed, the back surface oxide film 8 is formed on the back surface of the substrate 1 (FIG. 7B). Next, the silicon nitride film 3 and the silicon oxide film 2 formed in the element forming region 15 are removed, and the gate oxide film 16 having a uniform thickness is formed in the element forming region 15 (FIG. 7C). After the gate oxide film 16 is formed, a polysilicon film 20 is formed on both surfaces of the substrate, phosphorus is doped into the polysilicon film 20, and then a part of the polysilicon film 20 on the element formation region is covered with the gate 40.
(FIG. 7D).

As described above, in the conventional method for manufacturing a semiconductor device, the semiconductor device is manufactured by using the substrate from which impurities have been previously removed by gettering.
Therefore, it was possible to manufacture a high quality semiconductor device.

[0009]

However, the conventional semiconductor device manufacturing method has the following problems. Conventionally,
Gettering was performed separately from the semiconductor device manufacturing process. Therefore, when manufacturing a semiconductor device, be sure to
It has been time-consuming to perform separate steps. Further, if a substrate for which the gettering step has not been completed is used for manufacturing a semiconductor device, a desired semiconductor device cannot be manufactured, and the manufacturing cost may increase. Therefore, there is a problem that a desired semiconductor device cannot be manufactured depending on the progress of the gettering process, and the semiconductor device cannot be manufactured efficiently.

Therefore, it is an object of the present invention to provide a semiconductor device manufacturing method capable of performing efficient manufacturing.

[0011]

According to a first aspect of the present invention, there is provided an insulating film forming step of forming an insulating film on both surfaces of a substrate, and a first film forming a first film on both surfaces of the formed insulating film. A semiconductor device manufacturing method comprising: a forming step, a first film removing step of selectively removing a first film on a substrate surface, an element isolation region forming step of oxidizing an insulating film exposed by the first film removing, After the insulating film forming step and before the first film forming step, the insulating film on the back surface of the substrate is removed, and the first film formed on the back surface of the substrate is used as a gettering film.

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device in which an element isolation insulating layer and an element insulating layer are formed on the front surface of the substrate, and a back insulating layer is formed on the back surface of the substrate. A method of manufacturing a semiconductor device, comprising: a conductive film forming step of forming a film, wherein the second insulating film on the back surface of the substrate is removed after the insulating layer forming step and before the conductive film forming step to form a conductive film formed on the back surface of the substrate. The feature is that the film is used as a gettering film.

The method of manufacturing a semiconductor device according to a third aspect is the method of manufacturing a semiconductor device according to the second aspect, wherein impurities are implanted into the substrate and gettering is performed by the impurities.

[0014]

The semiconductor device manufacturing method according to the first and second aspects is characterized in that the first film or the conductive film formed on the back surface of the substrate is used as a gettering film.

A semiconductor device manufacturing method according to a third aspect is characterized in that, in the semiconductor device manufacturing method according to the second aspect, impurities are implanted into the substrate and gettering is performed by the impurities.

Therefore, gettering can be performed in the semiconductor device manufacturing process, and it is not necessary to separately provide a gettering process.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing and manufacturing a semiconductor tank according to the present invention will be described below. The substrates used in the following examples are those without gettering. First, the silicon oxide film 2 is formed on both surfaces of the substrate 1 shown in FIG. 1A by thermal oxidation (FIG. 1B). Next, only the silicon oxide film formed on the back surface of the substrate 1 is removed by etching (FIG. 1C). After removing the silicon oxide film on the back surface, a silicon nitride film 3 is formed on both surfaces of the substrate 1 by the CVD method. At this time, strains HS30 and HS40 occur at the interface between the back surface silicon nitride film 60 formed on the back surface of the substrate 1 and the substrate 1 (FIG. 1D). The strains HS30 and HS40 generated at the interface between the back surface silicon nitride film 60 and the substrate 1 trap impurities (Fe, Na, etc.) in the substrate 1 in the strains HS30 and HS40. That is, EG (Extrinsic Gettering) is performed by the strain generated at the interface between the backside silicon nitride film 60 directly formed on the backside of the substrate and the substrate 1.

A resist 18 is formed on the silicon nitride film 3 formed on the surface of the substrate, and the silicon nitride film 3 is removed by etching using the resist 18 as a mask. After etching the nitride film 3, boron is ion-implanted using the resist 18 as a mask (FIG. 2A). After the ion implantation, the resist 18 is removed, and the field oxide film (element isolation region) 30 is formed by heat diffusion (FIG. 2B). The heat treatment at the time of forming the element isolation region 30 promotes gettering in the strains HS30 and HS40.

After forming the element isolation region 30, the silicon nitride film 3 and the silicon oxide film 2 on the element forming region 15 are removed, and a gate oxide film 16 having a uniform thickness is formed on the element forming region 15 (see FIG. 2C). After forming the gate oxide film 16, a polysilicon film is formed on both surfaces of the substrate 1 by the CVD method, and a gate electrode 40 is formed by etching (FIG. 2D). In this way, a desired semiconductor device is formed in the element formation region 15. In addition, on the back surface of the substrate 1,
Since the back surface silicon nitride film 60 is formed, gettering is continuously performed. Further, the gettering here can be easily completed only by removing the back surface silicon nitride film 60. Therefore, the degree of gettering can be arbitrarily selected depending on the removal timing of the back surface silicon nitride film 60.

Furthermore, in the present embodiment, gettering is performed during the semiconductor device manufacturing process (so-called in-line), so there is no need to provide a separate gettering process. Therefore, it is possible to manufacture the semiconductor device efficiently without any trouble.

Another embodiment of the present invention will be described below. In the present embodiment, description will be given by using a substrate on which an element isolation region has been formed (FIG. 3A). An element isolation region 30 is formed on the surface of the substrate 1, and a gate oxide film 16 having a uniform thickness is formed on the element formation region 15. Further, the silicon oxide film 2 formed simultaneously when the gate oxide film 16 is formed remains on the back surface of the substrate 1 (FIG. 3A).

Next, the silicon oxide film 2 remaining on the back surface of the substrate 1 is removed by etching (FIG. 3B). After removing the silicon oxide film 2 by etching, a polysilicon 50 film is formed on both surfaces of the substrate 1 (FIG. 4A). When the polysilicon film is formed on both surfaces of the substrate 1, the back surface polysilicon film 55 is directly formed on the back surface of the substrate. When the polysilicon film 55 is directly formed on the back surface of the substrate, strains HS50 and HS60 occur at the interface between the back surface polysilicon film 55 and the substrate 1 (FIG. 4A). Therefore, the impurities (F
(e, Na, etc.) is strained by gettering HS50, HS6
Trapped to 0.

After forming a polysilicon film on both sides of the substrate 1, part of the front and back surfaces of the substrate 1 (element forming region 15) is doped with phosphorus (FIG. 4B). When phosphorus is doped into the polysilicon film 50 which will be the gate electrode 50 formed on the element formation region 15, phosphorus is diffused also into the back surface polysilicon film 55. The phosphorus doped on the back surface of the substrate causes new strain HS7 at the interface between the back surface polysilicon film 55 and the substrate 1.
0, HS80 is formed (FIG. 4B), and impurities (Na) in the substrate 1 are trapped. That is, in addition to gettering of the back surface polysilicon 55 film, gettering (so-called ring gettering) is further performed. Therefore, more reliable gettering can be performed by performing phosphorus doping on the back surface of the substrate shown in FIG. 4A.

Also in this embodiment, since the back surface polysilicon film 55 is formed on the back surface of the substrate, gettering is continuously performed. Further, gettering can be easily completed only by removing the back surface silicon oxide film 55. Therefore, the back surface silicon oxide film 55
It is possible to arbitrarily select the degree of gettering depending on the timing at which the semiconductor device is removed, and an efficient semiconductor device can be manufactured. Also in this embodiment, since gettering is performed during the semiconductor manufacturing process (so-called in-line), it is not necessary to separately provide a gettering process. Therefore, it is possible to manufacture the semiconductor device efficiently without any trouble.

In the gettering step in the above-mentioned two semiconductor device manufacturing methods, an optimum time can be selected as needed before or after the formation of the element isolation region in the semiconductor device manufacturing process. Therefore, gettering can be performed at an optimum time, and the semiconductor device can be efficiently manufactured.

[0026]

The semiconductor device manufacturing method according to the first and second aspects is characterized in that the first film or the conductive film formed on the back surface of the substrate is used as a gettering film.

A semiconductor device manufacturing method according to a third aspect of the present invention is characterized in that, in the semiconductor device manufacturing method according to the second aspect, impurities are implanted into the substrate and gettering is performed by the impurities. That is, it is possible to perform gettering in the semiconductor device manufacturing process, and it is not necessary to separately provide a gettering process.

Therefore, an efficient semiconductor device can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram showing steps of a semiconductor device manufacturing method according to the present invention.

FIG. 2 is a diagram showing steps of a semiconductor device manufacturing method according to the present invention.

FIG. 3 is a diagram showing another step of the semiconductor device manufacturing method according to the present invention.

FIG. 4 is a diagram showing another step of the semiconductor device manufacturing method according to the present invention.

FIG. 5 is a schematic view showing particles of a polysilicon film formed on a substrate.

FIG. 6 is a diagram showing steps of a conventional semiconductor device manufacturing method.

FIG. 7 is a diagram showing a step in a conventional semiconductor device manufacturing method.

FIG. 8 is a diagram showing a conventional gettering process.

[Explanation of symbols]

 1 ... Substrate 2 ... Silicon oxide film 60 ... Backside silicon oxide film HS30, HS40 ... Strain

Claims (3)

[Claims] 1. An insulating film forming step of forming an insulating film on both sides of a substrate, a first film forming step of forming a first film on both sides of the formed insulating film, and a first film on a substrate surface is selectively removed. And a device isolation region forming step of oxidizing an insulating film exposed by the first film removing step, the substrate being formed after the insulating film forming step and before the first film forming step. A method of manufacturing a semiconductor device, wherein the insulating film on the back surface is removed, and the first film formed on the back surface of the substrate is used as a gettering film. 2. An insulating layer forming step of forming an element isolation insulating layer and an element insulating layer on the front surface of the substrate and a back insulating layer on the back surface of the substrate, and a conductive film forming step of forming conductive films on both sides of the substrate. A method of manufacturing a semiconductor device, comprising: after the insulating layer forming step and before the conductive film forming step, removing the second insulating film on the back surface of the substrate and using the conductive film formed on the back surface of the substrate as a gettering film. And a method for manufacturing a semiconductor device. 3. The method for manufacturing a semiconductor device according to claim 2, wherein impurities are implanted into the substrate and gettering is performed by the impurities.