KR100252768B1 - Method for forming device isolation of semiconductor device - Google Patents

Abstract

PURPOSE: A method for forming an isolation layer of a semiconductor device is provided to prevent a bird's beak of a conventional field oxide layer and to improve step coverage. CONSTITUTION: In the method, a thick oxide layer(22) is formed on a silicon substrate(21) by oxidation of the substrate(21). Next, the thick oxide layer(22) is covered with a mask layer at an isolation region and removed at an active region to expose the substrate(21). The mask layer is then removed. After that, a silicon layer(24) is grown to a certain height on an entire structure and then selectively removed by using the oxide layer(22) as an etch stopper. Thus, the remaining silicon layer(24) as the isolation layer has the same plane as the oxide layer(22) has.

Description

METHODE FOR FORMING DEVICE ISOLATION OF SEMICONDUCTOR DEVICE}

The present invention relates to a device isolation film forming method, and to a device isolation film formation method that can remove the bird beak and the step.

Device isolation technology is a technology that provides the functions required to manufacture integrated devices by separating the individual devices constituting the integrated device from each other electrically and structurally so that each device can perform its own function without interference from adjacent devices. . In general, device isolation is divided into a dielectric film and a P-N junction. A typical example of a device isolation method using a dielectric film is a local oxidation of silicon (LOCOS) device isolation method.

Referring to FIG. 1, a method of forming an isolation layer of a semiconductor device according to a conventional LOCOS process will be described.

First, in order to relieve stress of the nitride film on the silicon substrate 11, a pad oxide film 12 is formed and the nitride film 13 is deposited. In this case, the polysilicon film may be further deposited before the nitride film 13 is deposited.

Subsequently, an etch stop mask (not shown) is formed in the active region A, the nitride layer 13 is removed until the pad oxide layer 12 is exposed, and then an inter-element insulating layer is formed by a thermal oxidation process. A phosphorous oxide layer 14 is formed. In this case, in the portion where the nitride layer 13 is located, the oxide layer is selectively grown only in the region where the oxide layer is not grown and the nitride layer 13 is absent, thereby separating the cells.

However, as the oxidation proceeds to the pad oxide film 12 existing under the nitride film 13 and the sidewall of the nitride film 13 is raised, a field oxide film 14 is formed, thereby forming a Bird's Beak (14 '). Occurs and the active area A is reduced.

As the Budbeek formed as described above has a larger area occupied as the device becomes more and more highly integrated, the operation characteristics of the device are reduced due to the reduction of the active area A necessary for the device to operate, and the insulation between devices is insufficient. There is a problem such as being. In addition, when the field oxide film is grown, 55% of the thickness of the oxide film is grown on the surface and 45% is grown below the surface. Thus, a step is generated between the cells by the field oxide film, which causes notches in a subsequent mask process.

An object of the present invention is to provide a method for forming a device isolation film of a semiconductor device from which the bird beak and the step are removed to solve the above problems.

1 is a cross-sectional view of a device isolation film forming process of a semiconductor device according to the prior art.

2A to 2D are cross-sectional views of a device isolation film forming process in a semiconductor device according to an embodiment of the present invention.

* Description of the main parts of the drawing

11, 21: silicon substrate 12: pad oxide film

13: nitride film 14: field oxide film

22: oxide film 23: mask

24: single crystal silicon film A: active region

B: device isolation region

The present invention for achieving the above object is a first step of forming an oxide film by a wet oxidation method of reacting oxygen and hydrogen on a silicon substrate; Forming a mask covering the device isolation region on the oxide film; Removing the oxide layer on an active region by using the mask as an etch stop layer; A fourth step of removing the mask; Forming a silicon film on the entire structure; And a sixth step of removing the silicon film so that the silicon film is flush with the oxide film.

In addition, the present invention for achieving the above object is a first step of forming an oxide film by a dry oxidation method on a silicon substrate; Forming a mask covering the device isolation region on the oxide film; Removing the oxide layer on an active region by using the mask as an etch stop layer; A fourth step of removing the mask; Forming a silicon film on the entire structure; And a sixth step of removing the silicon film so that the silicon film is flush with the oxide film.

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

2A to 2D illustrate a method of forming an isolation layer in accordance with an embodiment of the present invention.

First, as shown in FIG. 2A, the silicon substrate 21 is oxidized to form a thick oxide film 22. At this time, the oxide film 22 is made of a high temperature thermal oxidation process and is the same as a conventional field oxide film growth method. In addition, the oxide film may be formed by a wet oxidation method using oxygen and hydrogen by reaction and a dry oxidation method using only oxygen.

Next, as shown in FIG. 2B, a mask 23 for preventing etch is formed in the device isolation region B, and the oxide layer 22 on the active region A is removed by dry etching. During the etching process, all of the oxide layer is removed or a 50 nm thick oxide layer is left to completely expose the silicon substrate 21.

Next, as shown in Fig. 2C, a cleaning process for removing the mask 23 is performed. At this time, the oxide film remaining in the process of removing the oxide film 22 is completely removed in the cleaning process. Subsequently, the single crystal silicon film 24 is grown by a predetermined thickness over the entire structure in a temperature range of 900 ° C to 1250 ° C. By forming the single crystal silicon layer 29, damage to the silicon substrate 21 generated during the oxide layer etching process may be restored.

Next, as shown in FIG. 2D, the single crystal silicon 24 film is removed using the oxide film 22 as a stop layer so that the single crystal silicon film 24 has the same height as the oxide film 22. Next, as shown in FIG. In this case, the single crystal silicon film 24 may be removed using chemical mechanical polishing.

The present invention is a method of growing an oxide film having a predetermined thickness on a silicon substrate and etching an oxide film on an active region, and then forming a silicon film on the active region. You can prevent it. Therefore, it is possible to obtain a critical dimension required by design in a mask process for transferring a subsequent pattern. In addition, the process step is reduced because no process such as pad oxide film, polysilicon, nitride film deposition, etc. is required.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the technical field of the present invention without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

The present invention made as described above is a device isolation film forming method to fundamentally prevent the bird beak and the step, it is possible to improve the reliability of the device.

Claims (6)

A first step of forming an oxide film by a wet oxidation method in which oxygen and hydrogen are reacted on a silicon substrate; Forming a mask covering the device isolation region on the oxide film; Removing the oxide layer on an active region by using the mask as an etch stop layer; A fourth step of removing the mask; Forming a silicon film on the entire structure; And A sixth step of removing the silicon film such that the silicon film is flush with the oxide film; Device isolation film forming method of a semiconductor device comprising a. The method of claim 1, The fifth step, A method of forming an isolation film in a semiconductor device, comprising forming a single crystal silicon film in a temperature range of 900 ° C to 1250 ° C. The method according to claim 1 or 2, The third step, Characterized in that the oxide film having a thickness not exceeding 50 nm is left in the active region, The fourth step, And removing the mask and the oxide film remaining in the third step at the same time. A first step of forming an oxide film on a silicon substrate by a dry oxidation method; Forming a mask covering the device isolation region on the oxide film; Removing the oxide layer on an active region by using the mask as an etch stop layer; A fourth step of removing the mask; Forming a silicon film on the entire structure; And A sixth step of removing the silicon film such that the silicon film is flush with the oxide film; Device isolation film forming method of a semiconductor device comprising a. The method of claim 4, wherein The fifth step, A method of forming an isolation film in a semiconductor device, comprising forming a single crystal silicon film in a temperature range of 900 ° C to 1250 ° C. The method according to claim 4 or 5, The third step, Characterized in that the oxide film having a thickness not exceeding 50 nm is left in the active region, The fourth step, And removing the mask and the oxide film remaining in the third step at the same time.

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