KR19990061997A - Gate Forming Method of Semiconductor Device - Google Patents

Abstract

A method of forming a gate of a semiconductor device for forming two or more kinds of transistors having different thicknesses of gate oxide films is disclosed. According to the present invention, in the gate structure of a semiconductor device having a gate oxide film having a different thickness according to the characteristics of a device, a thick gate oxide film and a thin gate oxide film are separately formed and formed, and a photoresist film, which has been a problem of the prior art during gate oxide film formation, is used. By eliminating the step, a gate oxide film having a good film quality can be obtained, and precise thickness control is possible even if two kinds of gate oxide films have different thicknesses.

Description

Gate Forming Method of Semiconductor Device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a gate of a semiconductor device, and more particularly, to a method of forming a gate of a semiconductor device for forming two or more kinds of transistors having different thicknesses of gate oxide films in semiconductor devices in which gate driving currents are to be applied differently. It is about.

As semiconductor devices become more versatile and complex, technologies for implementing various devices on a single chip are being developed. Among them, MML (Dynamic Random Access Memory) and MML (Logic Memory / Logic) devices, which implement logic devices on one chip, are based on other MML devices for the logic part to play a specific role. It must have a different drive current than the part. In order to easily accomplish such a task, the design of the semiconductor device may be changed by changing the size of the device or by changing the voltage applied to the device. However, such a method is difficult to adopt because it increases the production cost of the semiconductor device.

The method of changing the driving current applied to the gate without changing the design of the semiconductor device is to have a different gate oxide film thickness for each device region. However, in order to form a gate oxide film having a partially differentiated thickness from the beginning, a difficult process is required, and the characteristics of the formed gate oxide film are also deteriorated.

1A to 1H are cross-sectional views illustrating a method of manufacturing a MOS transistor according to the prior art.

In order to manufacture a MOS transistor by the prior art, first, as shown in FIG. 1A, a field oxide film 20 for defining an active region and separating devices is formed on a silicon substrate 10.

Subsequently, as shown in FIG. 1B, a lower silicon oxide layer 30 is formed on the active region.

Next, as shown in FIG. 1C, the photoresist pattern 40 is formed only in a predetermined region having a large driving current applied to the gate electrode in the logic of the semiconductor device, for example, the MML element, and the photoresist pattern 40 is formed as an etch mask. When the silicon oxide film 30 is wet etched, the lower silicon oxide film pattern 31 may be obtained. Here, the predetermined region having a large driving current refers to a region having a gate oxide film that is relatively thicker than the gate oxide film formed in the region where the active region is exposed by the photosensitive film pattern 40.

Then, the photoresist pattern 40 is removed and an oxidation process is performed on the entire surface of the resultant to form a gate oxide silicon oxide film to obtain the structure shown in FIG. 1D. Accordingly, the first gate oxide layer 33 in which the lower silicon oxide layer pattern and the gate forming oxide layer are sequentially stacked is formed in a predetermined region having a large driving current applied to the gate electrode, and in the other active region, only the gate forming oxide layer is formed. A two gate oxide film 32 is formed. Thus, a relatively thick first gate oxide film 33 and a relatively thin second gate oxide film 32 are present on a single silicon substrate.

Next, the polysilicon film 50 is deposited to obtain the structure of FIG. 1E.

Thereafter, the gate electrodes 52 and 53 are formed through a photolithography process to obtain the gate structure shown in FIG. 1F.

FIG. 1G illustrates a process of forming a lightly doped drain (LDD) to prevent short channel effects in transistor formation. First, when the gate electrode is formed, thin oxide layers 62 and 63 are formed to heal damage caused in the etching process, and ions are implanted at a relatively low concentration to lightly doped drain 80 in the source / drain target region 80. ).

Subsequently, as shown in FIG. 1H, spacer oxide films 90 are formed on sidewalls of the gate electrodes 52 and 53 and the gate oxide films 32 'and 33', respectively. Ions are then implanted at relatively high concentrations to complete the source / drain regions 80 and 110.

The conventional double gate oxide film formed by the above-described method must undergo photoresist coating, its removal, and an additional oxidation process in the process of forming the first gate oxide film 33, and in this process, it will lead to deterioration of charge-containing properties and oxide film quality due to impurities. Can be. Particularly, in the case of forming a fine transistor, a relatively thick gate oxide film must be formed as a thin film of absolutely less than 100 GPa, and thus there is a possibility that the quality of the film is degraded or the thickness control fails.

Accordingly, an object of the present invention is to provide a gate forming method of a semiconductor device capable of ensuring a reliable film quality of a gate oxide film in implementing a gate structure using a double gate oxide film.

Another object of the present invention is to provide a gate forming method of a semiconductor device capable of precisely adjusting the thickness of a gate oxide film in implementing a gate structure using a double gate oxide film.

1A to 1H are cross-sectional views illustrating a method of manufacturing a MOS transistor according to the prior art;

2A to 2K are cross-sectional views illustrating a process sequence for implementing an embodiment of the present invention.

Explanation of Codes on Major Parts of Drawings

45... PSG film

36. First gate oxide

56. First gate electrode

38. Second gate oxide

58. Second gate electrode

The present invention for solving the above technical problem, in the gate structure of the semiconductor device having a gate oxide film having a different thickness according to the characteristics of the device, the insulating film on the entire surface of the silicon substrate formed by the active region separated by the device isolation field oxide film Forming a; Etching the insulating layer to expose the active region by selecting a group of portions in which the gate oxide films having the same thickness are to be formed in the active region, and forming a first gate oxide layer in the active region exposed by the etching step; Depositing a polysilicon film on the entire surface of the resultant product on which the first gate oxide film is formed, and completing the first gate electrode by chemical mechanical polishing of the polysilicon film to expose the insulating film outside the portion where the first gate oxide film is formed; Etching the insulating layer to expose an active region by selecting another group of portions where the gate oxide layers having the same thickness are to be formed, and forming a second gate oxide layer on the other active region exposed by the etching step; And depositing a polysilicon film on the entire surface of the resultant product on which the second gate oxide film is formed, and completing the second gate electrode by chemical mechanical polishing of the polysilicon film to expose the insulating film outside the portion where the second gate oxide film is formed. A method of forming a gate of a semiconductor device is provided.

In the present invention, the insulating film may be formed of a PSG or silicon nitride film.

In addition, it is preferable to further proceed with the step of forming a thermal oxide thin film before the step of forming the insulating film.

In addition, the step of selecting the groups of the portion where the gate oxide film having the same thickness is to be formed is preferably a step of selecting from the order of the thickness of the gate oxide film.

Meanwhile, the first gate electrode and the second gate electrode may be doped with impurities having different concentrations, one of the first gate electrode and the second gate electrode is doped with n-type, and the other is p-type. It can also be doped with.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A to 2K are cross-sectional views illustrating a process sequence for implementing an embodiment of the present invention.

Referring to FIG. 2A, a field oxide film 20 is first formed on a silicon substrate 10 to define an active region and to separate devices.

Subsequently, as shown in FIG. 2B, a thermal oxide thin film 30 is formed and a PSG (PhosphoSilicate Glass) film 45 is deposited on the resultant. At this time, the role of the thermal oxide film 30 is to use as a buffer layer for ion implantation when forming the LDD structure to be described later.

Next, a photolithography process is applied to the PSG film of the portion where the thick gate oxide film is to be formed to form the structure shown in FIG. 2C in which the active region of the portion is exposed.

Thereafter, a thick first gate oxide film 36 is formed, and a polysilicon film 55 is deposited to obtain the structure shown in FIG. 2D. The polysilicon film 55 may be doped with impurities after deposition, or doped during deposition to serve as a gate electrode. At this time, the type of doping impurity, such as n-type or p-type or the doping concentration, can be freely selected according to the type of semiconductor element to be used.

Subsequently, as illustrated in FIG. 2E, the deposited polysilicon film 55 is planarized by chemical mechanical polishing (hereinafter referred to as CMP) to form a first gate electrode on the first gate oxide film 36. Leave (56) and the rest leave the PSG film exposed.

2F to 2H are cross-sectional views showing a process for forming a gate oxide film thinner than the first gate oxide film 36, and the basic process method is the same as that shown in FIGS. 2A to 2E.

Referring to FIG. 2F, a photolithography process is applied to the PSG film of the portion where the thin gate oxide film is to be formed to expose the active region of the portion.

Subsequently, a thin second gate oxide film 38 is formed, and a polysilicon film 57 is deposited to obtain the structure shown in FIG. 2G.

Thereafter, as illustrated in FIG. 2H, the deposited polysilicon film 57 is planarized by CMP, leaving the second gate electrode 58 on the second gate oxide film 38.

Referring to FIG. 2I, by removing the PSG film pattern 47 by wet etching, first gates 36 and 56 and second gates 38 and 58 having different thicknesses of the gate oxide film are obtained.

2J to 2K are cross-sectional views illustrating a process of forming an LDD, and a basic process method is the same as that shown in FIGS. 1G to 1H of the prior art, and thus a detailed description thereof will be omitted.

Although the present invention has been described through the above embodiments, the present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical idea to which the present invention belongs. Accordingly, the above embodiment has been described with respect to the gate oxide film having two different thicknesses, but the thickness of the gate oxide film may be varied in various ways as necessary.

According to the present invention, there is provided a gate forming method of a semiconductor device for easily forming two or more kinds of transistors having different thicknesses of gate oxide films in a semiconductor device in which gate driving currents are to be applied differently. In addition, a reliable gate oxide film quality is ensured, and in implementing the gate structure using the double gate oxide film, accurate thickness control of the gate oxide film is possible.

Claims (6)

In the method of forming a gate structure of a semiconductor device having a gate oxide film having a different thickness, Forming an insulating film on the entire surface of the semiconductor substrate on which the active region separated by the device isolation field oxide film is formed; Etching the insulating layer to expose the active region by selecting a group of portions in which the gate oxide films having the same thickness are to be formed in the active region, and forming a first gate oxide layer in the active region exposed by the etching step; Depositing a polysilicon film on the entire surface of the resultant product on which the first gate oxide film is formed, and completing the first gate electrode by chemical mechanical polishing of the polysilicon film to expose the insulating film outside the portion where the first gate oxide film is formed; Etching the insulating layer to expose an active region by selecting another group of portions where the gate oxide layers having the same thickness are to be formed, and forming a second gate oxide layer on the other active region exposed by the etching step; And Depositing a polysilicon film on the entire surface of the resultant product on which the second gate oxide film is formed, and completing the second gate electrode by chemical mechanical polishing of the polysilicon film to expose the insulating film outside the portion where the second gate oxide film is formed; A method of forming a gate of a semiconductor device. The method of forming a gate of a semiconductor device according to claim 1, wherein said insulating film is a PSG or silicon nitride film. 2. The method of claim 1, further comprising forming a thermally oxidized thin film prior to forming the insulating film. The method of claim 1, wherein the selecting of the groups of the portions in which the gate oxide film having the same thickness is to be formed comprises selecting the gate oxide film in order of increasing thickness. The method of claim 1, wherein the first gate electrode and the second gate electrode are doped with impurities having different concentrations. The method of claim 1, wherein one of the first gate electrode and the second gate electrode is doped with an n-type, and the other is doped with a p-type.