JPH02192160A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce resist film forming processes in number so as to reduce a semiconductor device of this design in cost and to improve it in throughput by a method wherein a resist film used for removing a gate oxide film in a region where a thin film transistor is formed is used as a mask for ion- implantation. CONSTITUTION:A resist film 4 provided with openings in the regions where thin film transistors 1 and 5 are formed. With the film 4 used as a mask, ions are implanting into these transistor formation regions, and the thresholds of the thin film transistors 1 and 5 are concurrently controlled. Then, gate oxide films 1a and 5a of the openings are removed through etching, the resist film 4 is removed, and gate oxide films 1a and 5a of thin film are formed through an oxidation process in an oxidizing oven. Here, a resist film 9 provided with an opening corresponding to a region where a thick film transistor 2 is formed is formed, and ion implantation is executed using the resist film 9 as a mask and the threshold of the thick film transistor 2 is controlled. By this setup, processes can be reduced in numbers and a semiconductor device of this design can be reduced in cost and improved in throughput.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a method for manufacturing a semiconductor device in which transistors with gate insulating films of different thicknesses are formed on the same chip, which reduces the number of steps and contributes to cost reduction and increased throughput. In order to provide a method for manufacturing a semiconductor device that enables the formation of a semiconductor device, a resist film is formed in a region where the thick film transistor is to be formed in a semiconductor substrate on which a transistor defined by a field oxide film is formed, and the resist film is a step of controlling the threshold value of the thin film transistor formed on the semiconductor substrate as a mask; a step of removing the gate insulating film in the region where the thin film transistor is to be formed using the resist film as a mask; The method is configured to include a step of forming a gate insulating film.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device in which transistors having gate insulating films of different thicknesses are formed on the same chip.

In recent years, the number of steps in the manufacturing process of semiconductor devices has tended to increase due to addition of special functions to semiconductor devices, multilayering, and the like.

On the other hand, in order to reduce costs and increase throughput, it is necessary to reduce the number of steps as much as possible.

Under the above circumstances, there is a need for a semiconductor device manufacturing method that reduces the number of steps, contributes to cost reduction, and increased throughput.

[Conventional technology]

A conventional method for manufacturing a semiconductor device will be explained step by step with reference to FIG.

First, as shown in FIG. 2 (al), a field oxide film 13 is formed on a semiconductor substrate 18 to define an element formation region in which a thin film transistor 11 and a thick film transistor 12 are to be provided.

Next, as shown in FIG. 2 (bl), the entire surface is oxidized to form gate oxide films 11a and 12a of the same thickness as the gate oxide film of the thick film transistor 12, respectively, on the thin film transistor 11.
and is formed on the surface of the thick film transistor 12.

Next, as shown in FIG. 2(C), the thin film transistor 1
A resist film 14 having an opening is formed in the region where the resist film 1 is to be formed, and the resist film 14 is used as a mask to remove the resist film 11a in this region by etching.

Thereafter, the resist film 14 is removed, and oxidation treatment is performed in an oxidation furnace to form the thin film transistor 1 as shown in FIG.
A thin gate oxide film 11a is formed on the surface of 1.

Here, as shown in FIG. 2 again, the resist film 19 has an opening in the region where the thin film transistor 11 is to be formed.
is formed, and ions are implanted using this resist film 19 as a mask to control the threshold value of the thin film transistor 11.

Next, this resist film 19 is removed, and as shown in FIG.
Ions are implanted using the mask as a thick film transistor 12.
control the threshold.

Finally, as shown in FIG. 2(g), by removing the resist film 20, it becomes possible to form transistors with different film thicknesses on the same chip.

The order of the threshold voltage control step of the thin film transistor 11 shown in FIG. 2 fe) and the threshold voltage control step of the thick film transistor 12 shown in FIG. 2 ff) may be reversed.

It is necessary to perform the resist film forming process three times: the resist film 20 used for ion implantation to control the low value.

The resist film forming process includes resist 1-coating, resist curing, alignment, exposure, development, resist removal, cleaning,
The problem was that the process involved many steps including drying, resulting in a large number of steps and therefore a long turn.

In view of the above-mentioned circumstances, the present invention aims to provide a method for manufacturing a semiconductor device that can reduce the number of steps and contribute to cost reduction and increase in throughput.

[Problem to be solved by the invention]

In the conventional semiconductor device manufacturing method described above,
As shown in FIG. 2, a resist film 14 as a mask for removing the gate oxide film 11a on the surface of the thin film transistor 11, a resist film 19 used for implanting ions to control the threshold value of the thin film transistor 11, and a resist film 19 with a thickness Thick Film Transistor 12 [Means for Solving the Problems] A method for manufacturing a semiconductor device of the present invention includes forming a resist film in a region where a thick film transistor is to be formed in a semiconductor substrate on which a transistor defined by a field oxide film is formed. and controlling the threshold of the thin film transistor formed on the semiconductor substrate using the resist film as a mask; removing the gate insulating film in the region where the thin film transistor is to be formed using the resist film as a mask; The method is configured to include a step of forming a gate insulating film in a region where the thin film transistor is to be formed.

[Effect]

That is, in the present invention, ions are implanted to control the threshold value of the thin film transistor using a resist film used as a mask when removing the gate oxide film in the thin film transistor formation region. Since it is only necessary to perform the resist film formation process twice for the resist film used for the ion implantation for controlling the ions, the number of steps in the manufacturing process is reduced, and the number of steps can therefore be shortened.

〔Example〕

The case of 0MO8 according to an embodiment of the present invention will be explained below in the order of steps with reference to FIG.

First, as shown in FIG. 1(a), wells 6 and 7 are formed on the surface of a semiconductor substrate 8, and by forming a field oxide film 3, a thin film transistor 1, such as a normal P channel thin film transistor, is formed in the N type well 6. (Hereinafter, Pch
It is abbreviated as thin film T r . , ) and a thick film transistor 2, for example, a high voltage type P channel thick film transistor (hereinafter referred to as Pch thick film Tr).

It is abbreviated as. ) is defined, and a region is provided in the P-type well 7 to form a thin film transistor 5, for example, an N channel thin film transistor (hereinafter abbreviated as Nch thin film Tr).

Next, as shown in FIG. 1 (bl), the entire surface is oxidized to form gate oxide films 1a and 2a having the same thickness as the gate oxide film of the thick film transistor 2 on the surfaces of the thin film transistor 11 and the thick film transistor 12, respectively. .

Next, as shown in FIG. 1(C), the thin film transistor 1
A resist film 4 having openings is formed in the formation region of the thin film transistor 1 and the thin film transistor 5, and using this resist film 4 as a mask, the thin film transistor 1 and the thin film transistor 5 are formed.
Ions are simultaneously implanted into the forming regions of the thin film transistors 1 and 5 to simultaneously control the threshold values of the thin film transistors 1 and 5.

Then, as shown in FIG. 1(d), the gate oxide films 1a and 5a in these openings are removed by etching.

Thereafter, the resist film 4 is removed and oxidation treatment is performed in an oxidation furnace to form thin gate oxide films 1a and 15a on the surfaces of the thin film transistors 1 and 5, respectively, as shown in FIG. .

Here, as shown in FIG. 1(f), the thick film transistor 2
A resist film 9 having an opening is formed in the region where the thick film transistor 2 is to be formed, and ions are implanted using the resist film 9 as a mask to control the threshold value of the thick film transistor 2.

Next, as shown in FIG. 1(g), the resist film 9 is removed, a Pch thin film Tr and a Pch thick film Tr are formed in the N type well 6, and an Nch thin film Tr and a Pch thick film Tr are formed in the P type well 7. It becomes possible to form.

It is possible to reverse the order of the threshold voltage control process of the thin film transistors 1 and 5 shown in FIG. 1(C) and the etching removal process of the gate oxide films 1a and 5a shown in FIG. 1(dl). .

The above embodiment has been described for the case of 0MO8 in which the threshold values of PchTr and NchTr can be controlled at the same time. It is possible to apply the invention at all times.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, ions are implanted using the resist film used for removing the gate oxide film in the region where the thin film transistor is to be formed as a mask, so the process of forming the resist film is reduced by one step. Therefore, it is possible to provide a method for manufacturing a semiconductor device that can reduce the number of steps, contribute to cost reduction and increase throughput, and can be expected to have significant economic effects.

=9-

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view showing an embodiment of the present invention in order of steps, and FIG. 2 is a side cross-sectional view showing a conventional method for manufacturing a semiconductor device in order of steps. In the figure, 1 is a thin film transistor, 1a is a gate oxide film, 2 is a thick film transistor, 2a is a gate oxide film, 3 is a field oxide film, 4 is a resist film, 5 is a thin film transistor, 5a is a gate oxide film, 6 is a well, 7 is a well, 8 is a semiconductor substrate, and 9 is a resist film.

Claims (1)

[Claims] In a semiconductor substrate (8) on which transistors (1, 2, 5) defined by a field oxide film (3) are formed, a resist film (4) is provided in a region where the thick film transistor (2) is to be formed. ) and controlling the threshold values of the thin film transistors (1, 5) formed on the semiconductor substrate (8) using the resist film (4) as a mask; Thin film transistor (1, 5
), and forming the gate insulating film (1a, 5a) in the region where the thin film transistor (1, 5) is to be formed. A method for manufacturing a semiconductor device, characterized by: