JPH05335407A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the increase of junction leak between an adjacent diffusion layer (the source-drain of a transistor in general) and a substrate which leak is to be caused by crystal defect generated under bird's beaks in an element isolation region formed by an LOCOS method, in relation to a forming method of an element isolation region in a semiconductor device. CONSTITUTION:Firstly an element isolation region 15 is formed so as to be smaller than the final size. Next, thereon, an oxide film 19 is formed, and the oxide film 19 on the element forming regions 20, 21 are eliminated, thereby forming the element isolation region having the final size C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an element isolation region in a semiconductor device.

[0002]

2. Description of the Related Art MIS (Metal Insulator)
In recent years, the local oxidation method has been widely used as a method for separating element formation regions in an r Semiconductor (semiconductor) type semiconductor integrated circuit device. This method is called LOCOS
(Local Oxidation of Silic
On) method, by selectively forming a thick silicon oxide film as an insulating film, the semiconductor substrate is insulated and separated into a plurality of parts, and the separated parts are used as element formation regions.
Further, a method of doping impurities in the isolation region as an inversion prevention layer is also used in combination for element isolation.

FIG. 2 shows an example of this conventional method for forming an element isolation region.

First, as shown in FIG. 2A, an oxide film 2 and a nitride film 3 are formed on a semiconductor substrate 1. Next, as shown in FIG. 2B, the portion of the nitride film 3 to be the element isolation region is removed by photolithography (hereinafter abbreviated as photolithography) / etching technique, and only the portion is covered with an impurity for inversion prevention. The inversion preventing impurity 4 is implanted under a predetermined condition by an implantation (implantation: ion implantation) technique.

Next, as shown in FIG. 2B, the portion from which the nitride film 3 has been removed is oxidized to form an element isolation oxide film 5 as shown in FIG. 2C. Next, as shown in FIG. 2D, the oxide film 2 and the nitride film 3 are removed, and the element formation region 6 is formed.
And complete the separation of 7.

[0006]

However, in the above-mentioned conventional technique, as shown in FIG.
In the lower part of the bird's beak 5a, which is the edge of the above, a crystal defect 8 occurs due to the stress at the time of element isolation formation. Further, in general, the impurity diffusion layer as an element electrode (source and drain electrodes of the MIS transistor) formed after element isolation formation, in the edge 9 of FIG. 3B, the crystal defect under the bird's beak 5a described above. Therefore, there is a tendency that a problem that increases the junction leak between the diffusion layer 9 and the substrate 1 and hinders the device operation occurs.

According to the present invention, the crystal defects generated during the element isolation formation described above are taken into the element isolation region, that is, they are formed so as not to be located at the edge of the element electrode diffusion layer, and the diffusion layer and the substrate are bonded together. The purpose is to reduce leakage as much as possible.

[0008]

In order to achieve the above-mentioned object, according to the present invention, an element isolation region smaller than a target element isolation width is formed by a conventional element isolation technique LOCOS method, and then CVD (Chemical An oxide film is formed by the vapor phase epitaxy method, and the CVD oxide film is patterned by the photolithography technique and the wet etching technique so as to have the target element isolation width, and then diffused for the element electrode in the element region (active region). The layers were formed by the implantation technique and the diffusion technique. From this, LOCO
The crystal defects in the lower part of the bird's beak formed by the S method are taken into the isolation region from the edge of the diffusion layer, which is smaller than the target size of the element isolation width described above, and are substantially bonded to the substrate at the edge of the diffusion layer. Leakage is reduced.

[0009]

As described above, the present invention is based on the known LOCOS.
Since the crystal defects under the bird's beak formed by the method are taken into the finally formed element isolation region, there is no crystal defect in the element electrode diffusion layer or the edge part, and the element electrode diffusion due to the crystal defect is caused. Junction leakage between the layer and the semiconductor substrate is eliminated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

First, as shown in FIG. 1A, an oxide film 12 and a nitride film 13 are sequentially formed on a semiconductor substrate 11 in the same manner as in the prior art, and then, as shown in FIG. 1B, an element isolation region is formed. The nitride film 13 at the desired portion is removed by a known photolithography (photolithography) etching technique. At this time, the removal width A of the nitride film 13 is such that the finished element isolation width is smaller than the target dimension C.

That is, the removal width A = target dimension> A ≧ minimum slit dimension in the photolithography technique. Next, the inversion preventing impurity 14 is implanted into the element isolation region by an ion implantation method.

Subsequently, as shown in FIG. 1C, the oxide film 12 in the portion where the nitride film 13 has been removed is further oxidized and grown to form an element isolation oxide film 15. At this time, the bird's beak 15a corresponding to the edge of the element isolation oxide film 15 is formed.
A crystal defect layer 16 is formed on the semiconductor substrate 11 below the substrate.

Next, as shown in FIG. 1D, the nitride film 1
3 and oxide film 12 by wet etching technology
By removing, element formation regions (active regions) 17 and 18 are formed, and the well-known technique LOCOS (Local Oxid) is formed.
device isolation by the cation of silicon) method is completed. However, the element isolation region width B formed at this time is formed smaller than the target dimension C due to the above-described pattern width A.

Next, as shown in FIG. 1 (e), a known C
The oxide film 19 is formed by the VD method.

Subsequently, as shown in FIG. 1F, a portion of the CVD oxide film 19 which will be an element forming region is removed by a known photolithography / wet etching technique. As a result, the final element formation regions 20 and 21 are formed.

At this time, as shown in FIG. 1G, the width C of the final element isolation region is formed to have a target dimension.
Here, the element isolation formation according to the present embodiment is completed.

Further, the CVD oxide film 19 is provided with an impurity diffusion layer 22 as an element electrode (source and drain electrodes of a MIS transistor) which is generally formed after element isolation is formed.
Is used as a mask by an implantation technique and a diffusion annealing technique.

As a result, the previously formed bird's beak 1
The crystal defect 16 under 5a is taken into the element isolation region and is not located in the element electrode diffusion layer 22 or in the edge portion.
The junction leak between the diffusion layer 22 and the substrate 11 due to the phenomenon is eliminated.

[0020]

As described above in detail, according to the present invention, the crystal defects under the bird's beak formed by the known LOCOS method are taken into the finally formed element isolation region. In the electrode diffusion layer, or
There is no crystal defect in the edge part. Therefore, a junction leak between the element electrode diffusion layer and the semiconductor substrate due to the crystal defect is eliminated, and stable element operation can be obtained.

[Brief description of drawings]

FIG. 1 Example of the present invention

FIG. 2 Conventional example

[Figure 3] Problem explanatory diagram

[Explanation of symbols]

 11 semiconductor substrate 12 oxide film 13 nitride film 15 element isolation oxide film 16 crystal defect 17,18 element formation region 19 CVD oxide film 20, 21 final element formation region

Claims (1)

[Claims] 1. A process of forming an element isolation region having a width narrower than a target finish dimension on a semiconductor substrate, a process of forming an insulating film on the structure formed in the preceding paragraph, and a process of forming an insulating film. ) Removing the insulating film in the portion to be the element formation region,
And (d) a step of forming a diffusion layer by injecting impurities into the element formation region using the insulating film remaining in the step as a mask, A method of manufacturing a semiconductor device, comprising: