JPH0797566B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an impurity region on a semiconductor surface by using an ion implantation method.

[Conventional technology]

In the conventional method of manufacturing a semiconductor device, when the impurity region is formed in the semiconductor substrate by using the ion implantation method, it is formed in the semiconductor substrate 1 as shown in FIGS. 3 (a) and 3 (b), for example. An ion implantation mask material 5 is formed on the field oxide film 2 or the gate oxide film 3, and impurity ions 6 are implanted so as to reach the semiconductor substrate 1 through the gate oxide film 3.
The impurity region 7 was formed.

[Problems to be solved by the invention]

In the conventional semiconductor device manufacturing method as described above,
In the method of forming the impurity region 7 in the semiconductor substrate 1 by the ion implantation method, the ion implantation mask material 5 is the gate oxide film 3.
For example, there is a case where it directly contacts the thin insulating film on the semiconductor substrate 1. In this case, if the ion implantation mask material 5 has an isolated pattern, there is a drawback that charges may be accumulated in the ion implantation mask material 5 during the impurity ion implantation, and the underlying thin insulating film may be destroyed.

[Means for solving problems]

A method of manufacturing a semiconductor device according to the present invention includes a step of forming a conductive thin film on a thin gate insulating film formed on a semiconductor substrate, and preventing impurities from infiltrating into a lower layer thereof against ion implantation of impurities. A step of selectively forming a mask material on the conductive thin film, and ion-implanting impurities into a region not covered with the mask material through the conductive thin film and the thin gate insulating film to form a source region and A step of forming a drain region, and a step of selectively etching away the conductive thin film in a region not covered with the mask material by using the mask material as a mask to form a gate electrode. .

〔Example〕

 Next, the present invention will be described with reference to the drawings.

1 (a) and 1 (b) are longitudinal sectional views of the first embodiment of the present invention. An element region is formed on the semiconductor substrate 1 so as to be surrounded by the field oxide film 2, and a gate oxide film 3 is formed on the surface of the semiconductor substrate 1 in the element region.

A conductive thin film 4 of polysilicon, metal silicide, refractory metal or the like is formed so as to cover the entire surfaces of the field oxide film 2 and the gate oxide film 3, and an ion implantation mask material 5 is formed on the conductive thin film 4 in a predetermined shape. Form. The entire surface of the semiconductor substrate 1 is irradiated with the impurity ions 6, and the semiconductor substrate 1 in the region below the gate oxide film 3 which is not covered with the ion implantation mask material 5.
Impurity ions 6 are formed on the surface of the conductive thin film 4 and the gate oxide film 3.
Are implanted through to form the impurity region 7.

FIG. 2 is a vertical sectional view of the second embodiment of the present invention.

An island 10 of the semiconductor thin film is formed on the field oxide film 2 so that its end portion contacts the silicide layer 9 formed on the surface of the semiconductor substrate 1, and covers the island 10 of the semiconductor thin film and the surface of the semiconductor substrate 1. Then, the gate oxide film 3 is formed.

A conductive thin film 4 of polysilicon, metal silicide, refractory metal or the like is formed so as to cover the entire surfaces of the field oxide film 2 and the gate oxide film 3, and an ion implantation mask material 5 is formed on the conductive thin film 4. To form. P-type impurity ions 11 are implanted into the region of the island 10 of the semiconductor thin film which is not covered with the ion implantation mask material 5 through the conductive thin film 4 and the gate oxide film 3 to form the P-type impurity region 12.

〔The invention's effect〕

As described above, according to the present invention, when the impurity region is formed in the semiconductor substrate by the ion implantation method, the conductive thin film is provided immediately below the ion implantation mask material so as to cover the semiconductor substrate, and the conductive thin film is used as the substrate. Short circuit or grounding to prevent the accumulation of charges in the ion implantation mask material during impurity ion implantation and to prevent the thin insulating film between the semiconductor substrate and the ion implantation mask material from being destroyed. There is an effect that can be.

Further, a conductive thin film is provided under the ion implantation mask material, and since the conductive thin film is not formed on the side surface of this ion implantation mask material, the pattern of the diffusion region formed on the basic surface of the semiconductor is faithful to the pattern of the ion implantation mask material. Sex is protected.

Furthermore, when the method of the present invention is applied to the formation of the source / drain regions, after the source / drain ions are implanted, the conductive thin film is etched using the ion implantation mask material as a mask to remove the mask Since the lower conductive thin film can be directly used as the gate electrode, the present invention can be applied without increasing the number of steps.

[Brief description of drawings]

1 (a) and (b) are longitudinal sectional views of a first embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a second embodiment of the present invention, and FIGS. 3 (a) and (b). [FIG. 6] is a vertical sectional view of a conventional example. 1 ... Semiconductor substrate, 2 ... Field oxide film, 3 ... Gate oxide film, 4 ... Conductive thin film, 5 ... Ion implantation mask material, 6 ... Impurity ion, 7 ... Impurity region, 8 ...
n-type impurity region, 9 ... silicide layer, 10 ... island of semiconductor thin film, 11 ... P-type impurity region, 12 ... P-type impurity ion.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 29/78 301 F

Claims (1)

[Claims] 1. A step of forming a conductive thin film on a thin gate insulating film formed on a semiconductor substrate, and a mask material for preventing the impurity from penetrating into a lower layer thereof against ion implantation of the impurity. Of selectively forming on the conductive thin film,
Forming a source region and a drain region by ion-implanting impurities into a region not covered with the mask material through the conductive thin film and the thin gate insulating film; and using the mask material as a mask By selectively etching away the conductive thin film in the area not covered with
And a step of forming a gate electrode.