KR20010037321A - Method of forming a transistor in a semiconductor device - Google Patents

Abstract

PURPOSE: A method for manufacturing a transistor of a semiconductor device is provided to prevent a pitting defect of a silicon substrate in forming a gate electrode, by forming gate oxide layers having different thickness. CONSTITUTION: The first oxide layer is formed on a semiconductor substrate. A predetermined part of the fist oxide layer is etched to expose a predetermined part of the semiconductor substrate, wherein the exposed semiconductor substrate defines a gate oxide layer region. The second oxide layer as a gate oxide layer thinner than the first oxide layer is formed on the exposed semiconductor substrate. A gate electrode layer is formed on the first and second oxide layer. The gate electrode layer on both sides of the second oxide layer as the gate oxide layer is etched to form a gate electrode pattern.

Description

METHODE OF FORMING A TRANSISTOR IN A SEMICONDUCTOR DEVICE

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the formation of a transistor in a semiconductor device. More particularly, the transistor formation of a semiconductor device in which a gate oxide film formed on a channel region of a transistor is formed thin and a gate oxide film formed on a source / drain region is formed thick. It is about a method.

In the semiconductor industry, efforts are continuously made to improve the operating characteristics of a semiconductor device while reducing the manufacturing cost of the semiconductor chip. This effort led to the manufacture of sub-micron sizes. Miniaturization of semiconductor devices reduces operating characteristics that degrade capacitance and resistance, resulting in faster device operating speeds. The miniaturization of semiconductor devices also enables the fabrication of smaller chips, which allows smaller and more chips to be manufactured on a unit wafer, which reduces chip manufacturing costs.

The development of photolithography and dry etching technologies in the semiconductor manufacturing process has made it possible to miniaturize semiconductor devices. Photolithography and dry etching processes widely used in semiconductor manufacturing are as follows. A desired lower film quality (conductive film or insulating film) is deposited, a photoresist film is spin coated with a photosensitive film thereon, and light is passed through the photoresist film through a pre-prepared mask (made of an opaque quartz pattern on a transparent glass substrate). This is developed through a developer. The resulting conductive layer or insulating layer is etched using the resulting photoresist pattern to form a desired conductive layer pattern or contact.

When dry etching the desired film quality in the photolithography and etching process, the film existing under the desired film quality is undesirably etched and may cause various problems.

This problem causes the gate oxide film to be etched and the underlying semiconductor substrate to be etched during the etching of the gate electrode, particularly in the formation of the transistor, resulting in poor device reliability.

Specifically, in the semiconductor manufacturing process, the thickness of the gate oxide film continues to decrease. This is expected to be even lower in the future as the device needs to be increasingly fast. However, one of the problems that occurs as the thickness of the gate oxide film is lowered is that when the gate pattern is formed by etching polysilicon, which is a conductive film for the gate electrode, the semiconductor substrate is pitted in the source / drain region. This becomes more serious as the gate oxide becomes thinner for faster operation speed.

Since the polysilicon forming the gate and the silicon sub forming the lower semiconductor substrate are made of the same silicon, it is difficult to distinguish the film quality when etching.

Therefore, there must be sufficient gate oxide thickness for the fundamental solution.

Accordingly, the present invention has been proposed to solve the above-mentioned problems, and in order to form a low gate oxide film for the high speed of the device and at the same time to prevent damage to the semiconductor substrate, the gate oxide film constituting the transistor is formed thin and source / drain An object of the present invention is to provide a method for forming a transistor in which the gate oxide film on the top is formed thick.

1 is a cross-sectional view schematically illustrating a semiconductor substrate on which a first gate oxide film is formed on a semiconductor active region according to a transistor forming method of the present invention;

FIG. 2 is a cross-sectional view schematically illustrating a semiconductor substrate in which a first photoresist pattern is formed on the first gate oxide film as a process step subsequent to FIG. 1;

FIG. 3 is a schematic cross-sectional view of a semiconductor substrate after wet etching the first gate oxide film exposed by the first photoresist pattern as a process step subsequent to FIG. 2;

4 is a cross-sectional view schematically illustrating a semiconductor substrate in which a second gate oxide film is formed at a place where the first gate oxide film is removed, as a process step subsequent to FIG. 3;

FIG. 5 is a cross-sectional view schematically illustrating a semiconductor substrate on which a conductive film for a gate electrode and a second photoresist pattern are formed, as a process step subsequent to FIG. 4; And

FIG. 6 is a cross-sectional view schematically illustrating a transistor structure according to the present invention as a process step subsequent to FIG. 5.

(Configuration)

According to a preferred embodiment of the present invention, a first oxide film is formed on a semiconductor substrate, and a predetermined portion of the first oxide film is etched to form a predetermined portion of the semiconductor substrate. Exposing the semiconductor substrate, wherein the exposed semiconductor substrate defines a gate oxide region, forming a second oxide film on the exposed semiconductor substrate with a gate oxide film that is relatively thinner than the first oxide film, and wherein the first and second Forming a gate electrode film on the oxide film, and etching the gate electrode film on both sides of the second oxide film as a gate gate oxide film to form a gate electrode pattern.

In the above-described method, the first oxide layer may serve to protect a lower semiconductor substrate during etching of the gate electrode film.

In the above-described method, the gate electrode pattern is formed to be wider than the gate oxide layer.

(Action)

As shown in FIGS. 3 and 4, the photoresist pattern 140 is formed on the semiconductor substrate 100 on which the first gate oxide film 120 is formed to expose a portion where the gate oxide film formed under the gate electrode is to be formed. (160) The first gate oxide film is removed. Then, a thin second gate oxide film 180 is formed on the removed portion. Therefore, a thin gate oxide film can be formed for fast operation of the device, and damage to the semiconductor substrate can be prevented when forming the gate pattern.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1 to 6 are schematic cross-sectional views showing a method of forming a transistor according to the present invention, which are presented step by step. In the drawing, only the active region in which the electrical connection is formed in the semiconductor substrate is shown. The transistor forming method according to the present embodiment is applied not only to p-channel or n-channel of a MOSFET device but also to CMOS, BiCMOS, and the like.

First, a semiconductor substrate is prepared, and a device isolation process for defining an active region and an inactive region is performed. FIG. 1 schematically illustrates only a portion 100 of an active region of the semiconductor substrate. A first gate oxide layer having a thickness sufficient to protect the semiconductor active region 100, specifically, an active region in which a source / drain region is to be formed, is formed during etching of the gate electrode film for subsequent gate pattern formation on the semiconductor active region 100. 120) is formed. For example, it is formed to have a thickness of at least 50 Angstroms or more.

Next, referring to FIG. 2, a first photoresist pattern 140 is formed on the first gate oxide layer 120 to expose a predetermined portion of the first gate oxide layer 120. The portion exposed by the first photoresist pattern 140 is a portion where the gate electrode pattern is to be formed. Next, the first gate oxide layer 120 exposed using the first photoresist pattern 140 is etched. For example, wet etching is performed to expose the active region where the gate is to be formed, that is, the channel region 160 of the transistor as shown in FIG. 3. The wet etching is performed using a conventional oxide removal solution, for example, a buffered oxide etchant (BOE), hydrofluoric acid solution diluted 200: 1 to 250: 1. At this time, it can be seen that undercut of the oxide film occurs under the first photoresist pattern 140 due to the wet etching characteristic.

Next, the first photoresist pattern 140 is removed by a conventional ashing and stripping process. Then, a second gate oxide film 180 having a thickness relatively thinner than the first gate oxide film 120, that is, a gate oxide film having a desired thickness, is formed on the exposed active region (channel region) as shown in FIG. 4. Formed together. The second gate oxide layer 180 is formed as thin as possible for fast operation of the device. As a result, gate oxide layers 120 and 180 having different thicknesses are formed.

Next, referring to FIG. 5, a conductive material 200 for forming a gate electrode is deposited on the first and second gate oxide layers 120 and 180. The conductive material 200 is formed of, for example, polysilicon. It may also be formed from a double film of polysilicon and metal silicide. Next, a second photoresist pattern 220 defining a gate electrode pattern is formed on the gate electrode conductive material 200. The gate electrode pattern 240 is formed by anisotropically etching the gate electrode conductive material 200 using the second photoresist pattern 220 as a mask. The gate electrode pattern 240 is formed in a somewhat wider cross-section than the second gate oxide layer 180.

According to the present invention, the first gate oxide layer 120 is initially formed to be thick enough to sufficiently protect the lower active region when the gate electrode conductive material 200 is etched. In addition, sufficient overetching may be performed to form the gate electrode pattern 240 having a good sidewall profile.

Next, an ion implantation process for source / drain formation is typically performed. For example, when the semiconductor active region is p-type, n-type impurities are implanted. In the case of n-type, p-type impurities are implanted.

Although the present invention has been described with reference to preferred embodiments, the scope of the present invention is not limited thereto. Rather, various modifications and similar arrangements are included. Therefore, the true scope and spirit of the claims of the present invention should be interpreted broadly to encompass such modifications and similar arrangements.

According to one aspect of the present invention, after forming the first gate oxide film, selectively removing the first gate oxide film on the channel region, and forming a thin second gate oxide film, gate oxide films having different thicknesses can be formed. In addition, the silicon substrate is damaged when the gate electrode is formed at the same time as the operation characteristics of the device is improved, so that the pie can prevent the fitting coupling.

Claims (3)

In the transistor forming method of a semiconductor device, Forming a first oxide film on the semiconductor substrate; Etching a predetermined portion of the first oxide layer to expose a predetermined portion of the semiconductor substrate, wherein the exposed semiconductor substrate defines a gate oxide region; Forming a second oxide film on the exposed semiconductor substrate using a gate oxide film that is relatively thinner than the first oxide film; Forming a gate electrode film on the first and second oxide films; And And forming a gate electrode pattern by etching the gate electrode film quality on both sides of the second oxide film as a gate oxide film. The method of claim 1, And the first oxide layer protects the semiconductor substrate under the etching of the gate electrode film. The method of claim 1, And the gate electrode pattern is formed wider than the gate oxide film.