JP2525150B2 - Method for manufacturing MOS semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a MOS type semiconductor device, and more particularly to R
The present invention relates to OM (Read Only Memory) technology.

[Conventional technology]

Conventionally, ion implantation with the same polarity as the channel, source, and drain under the gate of a MOS transistor is performed,
When the operation of the S-transistor is fixed and, for example, a ROM is formed, the steps described below are performed.

(1) First, after a gate oxide film is formed on a silicon substrate (108), a place to be a gate electrode of a MOS transistor is opened by photolithography, and then ions having the same polarity as the source and drain are implanted to ROM. Data was being written (Fig. 2 (a)). Next, after removing the resist (103), the polysilicon (106) was deposited and patterning was performed (second
(C) figure).

(2) According to another method, first, a gate oxide film (101) is formed on a Si substrate (108), and then polysilicon is used for 4000
Deposition about Å (Fig. 3 (a)). After that, a hole is formed on the gate of the MOS transistor from above the polysilicon by photolithography, and then ions of the same polarity as the source and drain are implanted to write ROM data (FIG. 3 (b)). ).

[Problems to be solved by the invention]

However, in the above-mentioned conventional technique (1), the gate oxide film is directly exposed to the ions during the ion implantation for writing the ROM data, so that the gate oxide film is easily damaged, which is one of the causes of the gate film short circuit. Further, in the case of ROM, it is desirable that the ion implantation for writing data is carried out to the later step as much as possible, but this method is immediately after the gate oxidation step, and it takes the longest time to commercialize it. Had.

Further, in the above-mentioned conventional technique (2), since the ion implantation for ROM data writing is performed after polysilicon and deposition, the time until commercialization is also the conventional technique (1).
Compared with the above, it can be accelerated by 1 to 2 days and the damage of the gate film is relatively small, but since the ion implantation is performed through the polysilicon film of about 4000 Å, the acceleration voltage at the time of ion implantation is set to 320 keV or more. Therefore, the throughput at the time of ion implantation is extremely reduced.

The present invention solves such a problem, and an object of the present invention is to improve the throughput at the time of ion implantation, reduce the damage of the gate oxide film, and shorten the time for commercialization. To provide.

[Means for solving problems]

The method for manufacturing a MOS semiconductor device according to the present invention includes (a) a step of forming a gate insulating film of a MOS transistor on a semiconductor substrate, and (b) a gate electrode of the MOS transistor on the gate insulating film. A step of forming a first conductive film having a film thickness of 2000 angstroms or less, and (c) selectively forming a resist on the first conductive film except above a region which becomes a channel part of the MOS transistor in the semiconductor substrate. Forming step, (d) using the resist as a mask, implanting ions into the channel portion of the MOS transistor, (e) removing the resist, (f) contacting the first conductive film A step of forming a second conductive film to be a gate electrode of the MOS transistor,
(G) patterning the first conductive film and the second conductive film to form a gate electrode of the MOS transistor, which is composed of the patterned first conductive film and the second conductive film, It is characterized by having.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is a diagram showing an embodiment of the present invention in the order of steps.
First, as shown in FIG. 1 (a), a gate oxide film (101) is formed on a silicon substrate (108), and then a polysilicon first conductive film (106) is deposited on the order of 1000 to 2000Å. After thermally diffusing phosphorus into polysilicon, a resist pattern is formed according to the ROM pattern by photolithography, and impurities having the same polarity as the source and drain, such as boron for a p-channel transistor and phosphorus for an n-channel transistor, are formed. Alternatively, arsenic is ion-implanted. At this time, since the gate oxide film is not directly exposed to ions, damage to the gate oxide film is small, and since the polysilicon film thickness is 2000 Å or less, the ion accelerating voltage can be suppressed to about 160 keV. As a result, the throughput could be improved.

Next, as shown in FIG. 1B, after removing the resist, the electrode material (second conductive film) is deposited. At this time, there are polysilicon, tungsten silicide, molybdenum silicide, etc. as the electrode material.

Next, a pattern of the gate electrode was formed by photoetching.

 The advantages of the present invention have been described above with examples.

〔The invention's effect〕

As described above, according to the manufacturing process of the present invention, ion implantation is performed after depositing the first gate electrode layer having a film thickness of 2000 Å or less on the gate oxide film, thereby damaging the gate oxide film by ions. In addition to being able to reduce the number of ions, the accelerating voltage for ion implantation can be suppressed to about 160 keV, which is less than half compared to the case of implanting from above 4000 Å polysilicon, resulting in improved throughput and the number of days for commercialization It has become possible to make it one to two days earlier than the process of.

[Brief description of drawings]

1A to 1C are main cross-sectional views showing a method for manufacturing a MOS semiconductor device of the present invention. 2 (a) to (c) and FIGS. 3 (a) to (c) are main sectional views showing a conventional method for manufacturing a MOS semiconductor device. 101 …… Gate oxide film 102 …… Element isolation insulating film 103 …… Resist 105 …… Ion implantation layer 106 …… Polysilicon layer 107 …… Gate electrode material layer 108 …… Silicon substrate

Claims (1)

(57) [Claims] 1. A step of: (a) forming a gate insulating film of a MOS transistor on a semiconductor substrate; (b) a film having a film thickness of 2000 angstroms or less, which becomes a gate electrode of the MOS transistor, on the gate insulating film. 1 step of forming a conductive film, (c) step of selectively forming a resist on the first conductive film except above a region to be a channel portion of the MOS transistor in the semiconductor substrate, (d) Using the resist as a mask, implanting ions into the channel portion of the MOS transistor; (e) removing the resist; (f) contacting the first conductive film with the MOS transistor. Forming a second conductive film to be a gate electrode, and (g) patterning the first conductive film and the second conductive film to form the patterned first conductive film and the second conductive film. And a step of forming a gate electrode of the MOS transistor composed of the second conductive film, and a method of manufacturing a MOS semiconductor device.