Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2002-08-05
2004-11-23
Thompson, Craig A. (Department: 2813)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
Reexamination Certificate
active
06821854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor integrated circuit device. More particularly, the invention relates to technology that can be effectively adapted to a semiconductor integrated circuit device containing two kinds of MISFETs (metal insulator semiconductor field-effect transistors) to which different voltages are applied.
2. Prior Art
In a memory LSI such as CMOS (complementary metal oxide semiconductor) logic LSI (large scale integrated circuit) and SRAM (static random access memory) or DRAM (dynamic random access memory) and in a CMOS logic LSI mounting a memory circuit, the power source voltages may not often be the same between the internal circuit and the input/output circuit. In the CMOS logic LSI, for example, the length (gate length) of the gate electrodes of MISFETs in the internal circuit is set to be shorter than the gate length of MISFETs in the input/output circuit in order to increase the speed. In order to maintain a breakdown voltage of the semiconductor regions constituting the sources and drains of MISFETs in the internal circuit, however, the power-source voltage for the internal circuit is set to be lower than the power-source voltage for the input/output circuit. Here, in order to maintain reliability of the gate-insulating films of MISFETs in the input/output circuit having the high power-source voltage, the thickness of the gate-insulating films is selected to be larger than the thickness of the gate-insulating films of MISFETs in the internal circuit having the low power-source voltage.
Two kinds of gate-insulating films having different thicknesses are formed on a semiconductor substrate of silicon by, first, forming element isolation regions on the main surface of the semiconductor substrate and, then, subjecting the semiconductor substrate to the heat oxidation treatment of the first time to form a silicon oxide film on the surface of the semiconductor substrate. Next, active regions where the thick gate-insulating film will be formed are covered with a photoresist film, the silicon oxide film on the active regions on where the thin gate-insulating film will be formed is removed by wet etching and, then, the photoresist film is removed, followed heat-oxidizing the semiconductor substrate in the second time. That is, the thin gate-insulating film is formed through the heat oxidation of the second time, and the thick gate-insulating film is formed through the heat oxidation of the first time and through the heat oxidation of the second time.
SUMMARY OF THE INVENTION
Through their study, however, the present inventors have discovered the fact that according to the above-mentioned method of forming two kinds of gate-insulating films of different thicknesses, the active regions on where the thick gate-insulating film is to be formed is covered with the photoresist film at the time of removing, by wet etching, the silicon oxide film from the active regions on where the thin gate-insulating film is to be formed. Therefore, the thin gate-insulating film, thick gate-insulating film or these two gate-insulating films lose breakdown voltage due to contamination caused by the photoresist film and due to any damage in the step of removing the photoresist film and in the subsequent step of washing.
The object of the present invention is to provide technology capable of improving reliability of the semiconductor integrated circuit device containing a plurality of kinds of MISFETs having gate-insulating films of different thicknesses.
The above and other objects as well as novel features of the invention will become obvious from the description of the specification and the accompanying drawings.
Briefly described below are representative examples of the invention disclosed in this application.
That is, the invention is concerned with a process for forming two kinds of gate-insulating films, wherein a first insulating film is formed by etching, using a photoresist film as a mask, on a region of a semiconductor substrate on where an insulating film of a first relatively large thickness is to be formed and, then, a second insulating film is formed on the first insulating film in order to prevent the first insulating film from being scraped off in the step of washing which precedes the processing for forming an insulating film of a second relatively small thickness.
Further, the invention is concerned with a process for forming two kinds of gate-insulating films, wherein a first insulating film is formed by etching, using a photoresist film as a mask, on a region of a semiconductor substrate on where an insulating film of a first relatively large thickness is to be formed and, then, a second insulating film that has been formed in advance on the first insulating film is used as an etching stopper in the step of washing which precedes the processing for forming an insulating film of a second relatively small thickness.
Other representative examples of the invention disclosed in the application are as described below briefly.
A method of manufacturing a semiconductor integrated circuit device by forming an insulating film of a first thickness on a first active region of a semiconductor substrate and forming an insulating film of a second thickness smaller than the first thickness on a second active region is provided. This method includes the steps of:
(a) forming a first insulating film on the surface of the semiconductor substrate;
(b) forming a second insulating film which is a protection film on said the first insulating film;
(c) covering the first active region with a masking pattern;
(d) successively removing the second insulating film and the first insulating film from the second active region by using the masking pattern as a mask;
(e) selectively removing chiefly the second insulating film formed from the first active region after the masking pattern has been removed; and
(f) forming a third insulating film on the semiconductor substrate.
A method of manufacturing a semiconductor integrated circuit device by forming an insulating film of a first thickness on a first active region of a semiconductor substrate and forming an insulating film of a second thickness smaller than the first thickness on a second active region is also provided. This method includes the steps of:
(a) forming a first insulating film on the surface of the semiconductor substrate;
(b) forming a second insulating film which is a protection film on the first insulating film after the surface of the first insulating film has been removed by not more than about 1 nm;
(c) covering the first active region with a masking pattern;
(d) successively removing the second insulating film and the first insulating film from the second active region by using the masking pattern as a mask;
(e) selectively removing the second insulating film from said first active region after the masking pattern has been removed; and
(f) forming a third insulating film on the semiconductor substrate.
A method of manufacturing a semiconductor integrated circuit device is provided. This method includes the steps of:
(a) forming a first insulating film on the surface of a semiconductor substrate;
(b) forming a second insulating film which is a protection film on the first insulating film;
(c) forming a masking pattern on the semiconductor substrate so as to cover a first region on which an insulating film having a relatively large thickness will be formed but not covering a second region on which an insulating film having a relatively small thickness will be formed other than the first region;
(d) successively removing the second insulating film and the first insulating film from the second active region by using the masking pattern as a mask;
(e) after the masking pattern has been removed, removing the second insulating film by washing the semiconductor substrate, the second insulating film being used for suppressing the first insulating film from being scraped off; and
(f) forming a third insulating film on the semiconductor substra
Hiraiwa Atsushi
Horibe Shinichi
Ikeda Shuji
Kanda Takayuki
Sakai Satoshi
Antonelli Terry Stout & Kraus LLP
Renesas Technology Corp.
Thompson Craig A.
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