JP2903594B2 - 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 a mask used in an ion implantation step.

[Conventional technology]

Conventionally, a photoresist film is generally used as a mask for an ion implantation process. In particular, in a method for manufacturing a MOS LSI, a metal film is often used as a mask in order to prevent a gate portion from being damaged by charge-up.

2 (a) to 2 (d) are a plan view, a CC 'line sectional view, and a DD' line sectional view of a semiconductor chip shown in the order of steps for explaining a conventional method of manufacturing a semiconductor device. .

First, as shown in FIGS. 2 (a) and 2 (b), a gate electrode 3 having a thickness of 0.5 to 1.0 μm is selectively formed on an insulating film 2 provided on a silicon substrate 1. The aluminum layer 4 is formed on the surface containing
Deposit to a thickness of 1.5 μm. Here, if the cross section of the gate electrode 3 has an inverted trapezoidal shape, a cavity 6 is formed on the side surface of the gate electrode 3. Next, a photoresist film 5 is applied on the aluminum layer 4 to a thickness of 1 μm and patterned.

Next, as shown in FIGS. 2C and 2D, a pattern for ion implantation is formed by wet etching the aluminum layer 4 using the photoresist film 5 as a mask.
The cavity 6 is widened by the wet etching, and the mouth hole 7 is formed. Next, the photoresist film 5 is peeled off,
Using the aluminum layer 4 as a mask, impurity ions 8 are implanted to form a diffusion layer in the silicon substrate 1. Here, impurity ions 8 penetrate in the thinned portion of the aluminum layer 4 due to the mouse hole 7, and the impurity layer 9 is formed in a region other than the predetermined region of the silicon substrate 1.

[Problems to be solved by the invention]

In the conventional method of manufacturing a semiconductor device described above, the impurity ions are not sufficiently masked due to the mouse hole formed under the metal layer, and the impurity layer is formed in the semiconductor substrate other than the predetermined region and formed in the predetermined region. There is a problem that the characteristics of the semiconductor device are deteriorated due to connection with the diffusion layer.

[Means for solving the problem]

The method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device, comprising: forming a mask for ion implantation by patterning a metal layer on a surface including a step provided on a semiconductor substrate. A step of applying a positive photoresist film to a surface including a mouse hole portion generated by wet etching of the metal layer to fill the mouse hole portion, and exposing the entire surface and developing the positive photoresist only in the mouse hole portion. A step of removing the positive photoresist film in another region while leaving a film; and a step of ion-implanting impurities into the semiconductor substrate using the metal layer as a mask.

〔Example〕

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

1 (a) to 1 (d) are a plan view of a semiconductor chip and an A-
It is sectional drawing along the A 'line and BB' line.

First, as shown in FIGS. 1A and 1B, a pattern for ion implantation is formed by selectively etching the aluminum layer 4 by the same process as in the conventional example. Here, the mouse hole 7 is formed as in the conventional example.

Next, as shown in FIGS. 1 (c) and 1 (d), a positive photoresist film 10 having a viscosity of 20 to 60 cp is applied to the surface including the mouse hole 7 to fill the inside of the mouse hole 7 and prebaked. Thereafter, the entire surface is exposed and developed. At this time, the positive photoresist film 10 filling the inside of the mouse hole 7 is not exposed because of the aluminum layer 4, so that only the positive photoresist film 10 in the mouse hole 7 remains due to the development, and The positive type photoresist film 10 is removed. Next, using the aluminum layer 4 as a mask, impurity ions 8 are ion-implanted into the silicon substrate 1 to form a diffusion layer in a predetermined region.

As described above, since the positive type photoresist film 10 is filled in the mouse hole 7, it is possible to prevent formation of an impurity layer in an unnecessary region.

After the positive photoresist film 10 is developed, post-baking at a temperature of 200 ° C. and curing with ultraviolet light (temperature 100 to 200 ° C.) may be performed, and gas is released from the positive photoresist film 10 during ion implantation. However, there is an advantage that the ion implantation time can be shortened.

Further, a photosensitive polyimide resin film may be used instead of the positive type photoresist film 10.

〔The invention's effect〕

As described above, according to the present invention, even when a mouse hole is formed by wet etching of a metal layer due to a bad gate shape, ion implantation is performed with a resist film buried in the mouse hole. An impurity can be introduced only into the semiconductor device, and there is an effect that a semiconductor device with high yield and high reliability can be manufactured.

The yield of the semiconductor device according to the present invention was improved by 30% as compared with the conventional method.

[Brief description of the drawings]

1 (a) to 1 (d) are plan views and AA 'of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.
2 (a) to 2 (d);
FIG. 2 is a plan view, a CC ′ line sectional view, and a DD ′ line sectional view of a semiconductor chip shown in a process order for describing a conventional method of manufacturing a semiconductor device. DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Insulating film, 3 ... Gate electrode, 4 ... Aluminum layer, 5 ... Photoresist film,
6: cavity, 7: mouse hole, 8: impurity ion, 9: impurity layer, 10: positive photoresist film.

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising: forming a mask for ion implantation by patterning a metal layer on a surface including a step portion provided on a semiconductor substrate, wherein the step includes wet etching of the metal layer. A step of applying a positive photoresist film on the surface including the mouse hole portion generated by the above to fill the mouse hole portion, and leaving the positive photoresist film only in the mouse hole portion by whole-surface exposure and development. Removing the positive photoresist film in a region of the semiconductor device, and ion-implanting impurities into the semiconductor substrate using the metal layer as a mask.