KR100815036B1 - Device Separator Formation Method of Semiconductor Device - Google Patents

Abstract

The present invention relates to a method of forming a device isolation layer of a semiconductor device, and more particularly, to a method of forming a device isolation layer of a semiconductor device for rounding an edge of an active region when forming a device isolation layer by a shallow trench isolation method.

The device isolation film forming method of the semiconductor device of the present invention for realizing the above object is to sequentially form a pad oxide film, a silicon nitride film, a silicon oxide film on a semiconductor substrate and then proceed to the trench photo / etching process to the silicon oxide film, A hard mask forming step of patterning a silicon nitride film and a pad oxide film; A first dry etching step of etching a portion of the silicon layer of the semiconductor substrate using the patterned silicon oxide layer as an etching barrier; A wet etching step of etching the silicon surface exposed in the first dry etching step by a wet etching solution in which TMH, H ₂ O ₂ , and DIW are mixed; A second dry etching step of further etching the silicon layer of the semiconductor substrate by using the patterned silicon oxide layer as an etching barrier; A trench filling step of cleaning the wafer on which the second dry etching step is completed, and depositing a device isolation layer so that the trench is completely filled after the oxide film forming process is performed; And a field oxide film forming step of removing the silicon nitride film by a wet etching process after polishing the device isolation layer and the silicon oxide film by a CMP process.

According to the method of forming a device isolation layer of a semiconductor device according to the present invention, a portion of the trench is partially etched and then the silicon is etched by a wet etching method, and the remaining trench is etched. There is an effect that can prevent the formation of the semiconductor to improve the semiconductor manufacturing yield.

STI, Rounding, Pullback Process, Phosphate, Watermark, TMH

Description

Isolation method of semiconductor device

1A to 1F are cross-sectional views illustrating a method of forming a device isolation film using a conventional STI process;

2a to 2b is a SEM photograph of the trench after the progress of the conventional silicon nitride film pullback process,

3 is a graph analyzing a profile of a component of the watermark portion of FIG. 2;

4 is a flowchart illustrating a method of forming a device isolation film of a semiconductor device according to an embodiment of the present invention;

5A to 5F are cross-sectional views illustrating a method of forming a device isolation film of a semiconductor device in accordance with an embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

10 semiconductor substrate 20 pad oxide film

30 silicon nitride film 40 TEOS film

50: trench 60: oxide film

70: device isolation film

The present invention relates to a method of forming a device isolation layer of a semiconductor device, and more particularly, to a method of forming a device isolation layer of a semiconductor device for rounding an edge of an active region when forming a device isolation layer by a shallow trench isolation method.

In general, miniaturization of a pattern due to high integration of semiconductor devices is generally applied to semiconductor processes. Device isolation layers for separating active devices have been performed by a conventional local oxidation of silicon (LOCOS) method, but recently, shallow trench isolation (hereinafter, referred to as shallow trench isolation) capable of maintaining a relatively small occupied area is described below. The method of forming a device isolation layer using a 'STI' method has been introduced to expand the scope of application.

The STI method is a method of forming a trench by selectively etching a specific region of a semiconductor substrate and then separating the device by embedding an insulator in the trench.

In the method of forming a device isolation layer using the STI method, an angle is formed at an edge (or edge) of an active region to be formed, whereby an electric field is concentrated, and the threshold voltage of the transistor decreases as the channel width decreases on the transistor. An inverse narrow width effect occurs in which the threshold voltage is reduced, or a hump phenomenon occurs in which the channel at the edge is formed first so that the transistor is turned on twice.

Therefore, when the STI method is used in a highly integrated semiconductor device, the rounding process of the edge portion is an important step in determining the electrical characteristics of the semiconductor device.

1A to 1F are cross-sectional views illustrating a method of forming a device isolation film using a conventional STI process.

Referring to FIG. 1A, a pad oxide film 20, a silicon nitride film 30, and a tetraethylorthosilicate (TEOS) film 40 are sequentially formed on a semiconductor substrate 10. Thereafter, a trench photo / etch process is performed to pattern the TEOS layer 40, the silicon nitride layer 30, and the pad oxide layer 20.

Referring to FIG. 1B, the trench 50 is formed by etching the silicon layer of the semiconductor substrate using the patterned TEOS film 40 as an etch barrier.

Referring to FIG. 1C, a pull back process of the pad oxide layer 20 and the silicon nitride layer 30 is performed.

Referring to FIG. 1D, a wafer subjected to the pullback process is subjected to a chemical downstream etch (hereinafter referred to as 'CDE') process to round the upper corner portion A of the formed trench.

Referring to FIG. 1E, after the oxide film 60 is formed to etch damage caused during the trench etching process, the device isolation layer 70 is deposited to completely fill the trench.

Referring to FIG. 1F, after polishing the device isolation layer 70 and the TEOS film 40 by the CMP process using the silicon nitride film 30 as the polishing stop layer, the silicon nitride film 30 is subjected to a wet etching process. Remove by

However, the conventional method of forming an isolation layer using the STI process has a problem of generating a watermark in the trench region during the pullback process of the pad oxide layer and the silicon nitride layer.

That is, the phosphoric acid solution used to remove the silicon nitride film is a high temperature (160 ° C.) and high concentration (85%) solution, and has a high selectivity ratio (about 1:40) of the silicon nitride film to the silicon oxide film. Therefore, it is an etchant that is mainly used to remove the silicon nitride film.

Although the phosphoric acid solution has a high selectivity, the native oxide present in the trench region is removed during the silicon nitride pullback process to expose the hydrophobic silicon surface and subsequent HQDR (hot). The inside of the trench where the silicon surface is exposed during the quick dump rinse, the DIW (deionized water) cleaning step, and the spin dry step is a defect in which a silicon oxide-based material is filled (hereinafter referred to as a 'watermark'). ) Is generated.

2A to 2B are SEM photographs of trenches observed after the progress of the conventional silicon nitride film pullback process, and FIG. 3 is a graph analyzing the profile of the components of the watermark portion of FIG. 2.

As shown in the left photograph of FIG. 2A, the normal STI pattern shows a good profile, but as shown in the right photo of FIG. 2A and FIG. 2B, the abnormal STI pattern shows that the trench region is filled with a silicon oxide-based material. The state can be observed. FIG. 2B shows a cross section of portion A of the right picture of FIG. 2A.

The data analyzed in FIG. 3 is a graph comparing and analyzing surface components of trench regions of the abnormal STI pattern in AES (Auger electron spectroscopy) equipment. As observed in the accompanying FIG. 3, the main components constituting the watermark are Si and O, and therefore, it is assumed to be a silicon oxide-based material.

Accordingly, the present invention has been made to solve the above-mentioned problems, and the device isolation film is formed in the semiconductor device which can fundamentally prevent the formation of the watermark generated in the rinse step of the highly viscous phosphoric acid solution during the pull back process of the silicon nitride film The purpose is to provide a method.

The device isolation film forming method of the semiconductor device of the present invention for realizing the above object is to sequentially form a pad oxide film, a silicon nitride film, a silicon oxide film on a semiconductor substrate and then proceed to the trench photo / etching process to the silicon oxide film, A hard mask forming step of patterning a silicon nitride film and a pad oxide film; A first dry etching step of etching a portion of the silicon layer of the semiconductor substrate using the patterned silicon oxide layer as an etching barrier; A wet etching step of etching the silicon surface exposed in the first dry etching step by a wet etching solution mixed with TMH, H ₂ O ₂ , and DIW; A second dry etching step of further etching the silicon layer of the semiconductor substrate by using the patterned silicon oxide layer as an etching barrier; After cleaning the wafer on which the second dry etching step is completed, an oxide film forming process is performed to grow a silicon oxide film on the silicon surface exposed by the wet etching step and the second dry etching step so that the trench is completely buried. A trench filling step of depositing a device isolation layer; And a field oxide film forming step of removing the silicon nitride film by a wet etching process after polishing the device isolation layer and the silicon oxide film by a CMP process.

delete

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4 is a flowchart illustrating a method of forming a device isolation film of a semiconductor device according to an embodiment of the present invention, and FIGS. 5A to 5F illustrate a method of forming a device isolation film of a semiconductor device according to an embodiment of the present invention. It is a section for.

As shown in FIG. 4, a method of forming a device isolation layer of a semiconductor device according to an embodiment of the present invention may include a hard mask forming step, a first dry etching step, a wet etching step, a second dry etching step, and a trench filling step. And a field oxide film forming step.

The hard mask forming step is a step of patterning the silicon oxide film, silicon nitride film, and pad oxide film by sequentially forming a pad oxide film, a silicon nitride film, and a silicon oxide film on a semiconductor substrate and performing a trench photographing / etching process (FIG. 5A). The pad oxide film serves as a buffer film for alleviating stress caused by the silicon nitride film. The silicon nitride film not only serves as a hard mask in a subsequent trench etching step, but also serves as a CMP stop layer in a subsequent CMP process. The silicon oxide film serves as a hard mask in a subsequent trench etching step.

The first dry etching step is to etch a portion of the silicon layer of the semiconductor substrate using the patterned silicon oxide layer as an etch barrier (see FIG. 5B). The silicon oxide may be etched by a subsequent wet etching process by removing the natural oxide layer and exposing the silicon layer by etching a predetermined thickness.

In the wet etching step, the surface of the silicon exposed in the first dry etching step is silicon-etched by a wet etching solution (see FIG. 5C). Thus, the pad oxide layer and the semiconductor may be wet-etched with an isotropic etching property. It is possible to form an under cut in the edge portion of the trench region in which the substrate is in contact.

In the second dry etching step, the silicon layer of the semiconductor substrate is further etched using the patterned silicon oxide layer as an etching barrier (see FIG. 5D). Thus, the trench pattern is etched by etching the trench to a desired depth. Is completed.

The trench filling step is a step of cleaning the wafer on which the etching step is completed, and then depositing a device isolation layer so that the trench is completely filled after the oxide film forming process is performed (see FIG. 5E), that is, a buffered hydrofluoric acid solution (buffered). After the cleaning step of removing the etching residue generated in the etching step using a mixture of HF) and hydrochloric acid (HCl) and ozone (O ₃ ), the device isolation film such as TEOS oxide film and the like is embedded in the trench. .

The field oxide film forming step is a step of polishing the device isolation film and the silicon oxide film by a CMP process, and then removing the silicon nitride film by a wet etching process (see FIG. 5F). That is, the silicon nitride film is a polishing stop layer. The device isolation film and the silicon oxide film are polished by a CMP process, and then the silicon nitride film 30 is removed by a wet etching process using a high temperature phosphoric acid solution.

Therefore, in the method of forming a device isolation layer of a semiconductor device according to an embodiment of the present invention, a rounding process is performed by performing a silicon etching process using a wet etching solution in the wet etching step, instead of a rounding process using a conventional pull back process of a silicon nitride film. This is to prevent the generation of the watermark generated in the step of rinsing the high phosphoric acid solution.

In the first dry etching step of the method of forming a device isolation layer of a semiconductor device according to an embodiment of the present invention, it is preferable to proceed to the process conditions for etching silicon of 10 ~ 100Å. The thickness of the silicon etched in this step is to determine the shape of the undercut of the silicon to be performed by the subsequent wet etching process to bring about the rounding effect of the trench edge region, and to proceed to the process conditions of the silicon of 10 ~ 100Å Optimum device characteristics can be secured.

The wet etching step of the method of forming a device separator of a semiconductor device according to an embodiment of the present invention is TMH (trimethyl-oxyethyl-ammonium-hydroxide, hereinafter referred to as TMH), H ₂ O ₂ , and DIW (deionized water) It is preferable to etch the silicon layer using a wet etching solution (hereinafter referred to as 'NC2') mixed with 'DIW'.

The NC2 is a cleaning liquid mainly used for removing the cured photoresist and removing particles. TMH contained in the NC2 is anisotropically etched on the surface of single crystal silicon and the etching rate is high, so that the roughness of the silicon surface increases when used alone, together with hydrogen peroxide (H ₂ O ₂ ) and DIW. Use by mixing. That is, the hydrogen peroxide reduces surface roughness by decomposing organic contaminants and forming an oxide film on the silicon surface to passivate the silicon surface.

In addition, if the hydrogen peroxide is not rapidly decomposed in the NC2 solution, the oxidizing power is lowered, and the process is performed at a high temperature to compensate for this. Therefore, when the temperature is high, the surface of the silicon forms an oxide film, so that it becomes hydrohpilic and the contact angle becomes small.

The general chemical reaction for etching silicon (Si) by the NC2 solution is as follows.

Si  + 6 OH ^-  = SiO ₃ ^{2 +}  + 3 H ₂ O  + 3e ^-

Therefore, by etching the silicon by NC2 solution and further dry etching, it is possible to obtain a trench shape in which the edge portion is rounded.

It will be apparent to those skilled in the art that the present invention is not limited to the above embodiments and can be practiced in various ways without departing from the technical spirit of the present invention. will be.

As described in detail above, according to the method of forming a device isolation layer of a semiconductor device according to the present invention, a partial etching of the trench is performed, followed by silicon etching by a wet etching method, followed by the remaining trench etching to pull back the conventional silicon nitride film. There is an effect that it is possible to fundamentally prevent the formation of watermarks generated in the process step to improve the semiconductor manufacturing yield.

Claims (3)

delete delete A hard mask forming step of sequentially forming a pad oxide film, a silicon nitride film, and a silicon oxide film on a semiconductor substrate and performing a trench photo / etch process to pattern the silicon oxide film, the silicon nitride film, and the pad oxide film; A first dry etching step of etching a portion of the silicon layer of the semiconductor substrate using the patterned silicon oxide layer as an etching barrier; A wet etching step of etching the silicon surface exposed in the first dry etching step by a wet etching solution mixed with TMH, H ₂ O ₂ , and DIW; A second dry etching step of further etching the silicon layer of the semiconductor substrate by using the patterned silicon oxide layer as an etching barrier; After cleaning the wafer on which the second dry etching step is completed, an oxide film forming process is performed to grow a silicon oxide film on the silicon surface exposed by the wet etching step and the second dry etching step so that the trench is completely buried. A trench filling step of depositing a device isolation layer; And a field oxide film forming step of polishing the device isolation film and the silicon oxide film by a CMP process, and then removing the silicon nitride film by a wet etching process.

Images