KR20090056083A - Fabrication method of a semiconductor device - Google Patents

Abstract

A fabrication method of a semiconductor device is provided to prevent the clog of a filter at a phosphoric acid bath, by maintaining etch rate constantly and increasing production yield. A pad oxide film(302) and a pad nitride layer are formed on a semiconductor substrate(300) in order. The pad oxide film and the pad nitride layer are patterned so that a semiconductor substrate of an element isolation region is exposed, and an element isolating trench is formed by using the patterned pad nitride layer as the hard mask. After burying the inside of a trench with an insulating material, the top of the trench is planarized and the element isolation film(310) is formed. The pad nitride layer is removed through a first wet etching using a phosphoric acid after forming the element isolation film. A residue of the pad nitride film and a part of the pad oxide film are removed through a second etching with the phosphoric acid and fluorine base solution.

Description

Manufacturing method of semiconductor device {FABRICATION METHOD OF A SEMICONDUCTOR DEVICE}

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device suitable for etching the pad oxide film and the pad nitride film in forming the device isolation film of the semiconductor device.

As is well known, semiconductor devices have a large number of unit devices, such as transistors and capacitors, limited by the capacity of the semiconductor device (eg, thousands to billions), which are integrated for independent operation. It is necessary to isolate (or isolate) electrically.

Therefore, as a method for electrical separation between such semiconductor devices, a silicon partial oxidation (LOCOS) method of recessing a silicon substrate and growing a field oxide layer and etching the silicon substrate in a vertical direction Shallow Trench Isolation (STI) is a well known method of filling with insulating material.

Among them, the shallow trench isolation device isolation layer is a method of forming narrow and deep shallow trenches using dry etching methods such as reactive ion etching and plasma etching, and gapfilling the insulating film therein. Flattening is advantageous for miniaturization by reducing the area occupied by device isolation regions.

In describing the process of forming the shallow trench isolation device isolation layer, the pad oxide layer and the pad nitride layer are sequentially formed on the semiconductor substrate, and the pad oxide layer is etched to expose the semiconductor substrate according to a predetermined photoresist pattern. Using a hard mask to etch the semiconductor substrate to form a trench for isolation of the device, filling the formed trench with an insulating material, and then planarizing the upper portion thereof, and removing the pad nitride film by wet etching, thereby forming a shallow trench isolation method. The device isolation layer is formed. Here, a liner oxide film may be formed on the surface of the trench before filling the trench with an insulating material.

In this case, the pad oxide layer serves as an intermediate protective layer to alleviate the physical stress caused by the difference in the lattice structure between the pad nitride layer and the polysilicon oxide interface, and forms the end point using the selectivity in the etching process. To prevent over-etching, and to protect the surface of the silicon substrate in the implant process and to form a dose profile (Dose Profile).

In addition, the pad nitride film protects the portion where the channel is to be formed from a subsequent process, prevents impurities from being introduced, and when the photoresist is used in the process of forming the liner oxide film after the trench process, the pad nitride film may be formed as a hard mask. An oxide film is formed by using the same, and is formed for use as an end point when planarization of the embedded insulating material.

Meanwhile, after the device isolation layer is formed, wet etching using a phosphoric acid solution of about 80% to 85% is performed to etch the pad nitride layer, which is performed at a high temperature of 150 ° C or higher. When the water in the phosphoric acid solution decreases during this wet etching, the concentration of the phosphoric acid solution is increased, and the etching rate of the pad nitride film is gradually lowered.

The pad nitride film was removed by wet etching using a phosphate solution, and the pad oxide film was etched using two successive phosphate baths to perform Moat Wet Etching. Seasoning is performed using 50 wafers grown at 6000 GPa (± 5ea), and the conventional Mortium etching process includes etching the pad oxide film grown in a high temperature phosphoric acid process in addition to removing the pad nitride film. .

It also includes the removal of pad nitride film residues and in-situ etching of the pad oxide film in the 2nd phosphate bath of the Mott etch process, with a pad nitride film of 1400 Å-1800 에서 in the first phosphate bath subjected to the seasoning. Dip processing time of more than 60 minutes is required to etch the oxides, and oxide particles exceeding the filter size in the wet fin etching process using the phosphoric acid solution to etch the pad nitride film and the pad oxide film into the in-suite. Filter contamination has occurred.

However, when the pad oxide layer and the pad nitride layer are etched during the formation of a conventional device isolation layer, the pad nitride layer is easily removed through wet etching using a phosphoric acid solution, while the pad oxide layer remains in a particle form and is contaminated by oxide particles. The filter has a problem that the pressure in the filter increases and the increased pressure causes particles to reverse contamination the wafer surface.

In addition, the induced particles contain a residue component in addition to the pad oxide film, and thus may not be removed in subsequent cleaning, and as the etching time of the pad oxide film is increased in the seasoned phosphate bath, Additional work was needed to cause filter contamination of the phosphate bath and periodically perform filter cleaning with a fluorine-based solution (eg, HF, etc.). As an example, as shown in FIG. 1, the phosphoric acid solution does not show a significant difference in the etching rate of the nitride film according to the number of times of use, whereas as shown in FIG. 2, the phosphoric acid solution has an etching rate of the oxide film as the number of times of use increases. This is greatly reduced and the oxide film etching ability is lost.

Accordingly, the present invention is to provide a method for manufacturing a semiconductor device that can effectively etch the pad oxide film through wet etching using a phosphoric acid solution and a fluorine-based solution in the process of forming a device isolation layer of the semiconductor device.

In addition, the present invention is to provide a method for manufacturing a semiconductor device that can prevent the clogging of the phosphate filter by adding a fluorine-based solution when the pad oxide film is etched in the process of forming a device isolation layer of the semiconductor device.

The present invention comprises the steps of sequentially forming a pad oxide film and a pad nitride film on a semiconductor substrate; Patterning the pad oxide layer and the pad nitride layer to expose the semiconductor substrate in an isolation region; Forming a device isolation trench using the patterned pad nitride layer as a hard mask; Filling the inside of the trench with an insulating material and then planarizing an upper portion thereof to form an isolation layer; Removing the pad nitride layer through primary wet etching using a phosphoric acid solution after forming the device isolation layer, and removing the pad nitride residue and a portion of the pad oxide layer remaining after the first wet etching process using the phosphoric acid solution and the fluorine-based solution. It provides a method of manufacturing a semiconductor device comprising the step of removing through the secondary wet etching.

Unlike the conventional method of removing the pad oxide film and the pad nitride film by wet etching using a phosphoric acid solution when forming the device isolation layer of the semiconductor device, the pad oxide film and the pad nitride film are sequentially formed on the semiconductor substrate and then patterned. Accordingly, after forming the device isolation layer through trench formation, embedding of an insulating material, and planarization, the pad nitride layer is removed by primary wet etching using a phosphate solution, and the remaining pad nitride layer and a part of the pad oxide layer are replaced with the phosphoric acid solution and fluorine. By removing through a second wet etching process using a lean solution, the etching rate of the oxide film can be maintained to improve the yield of the semiconductor device, and the fluorine-based solution can be added to prevent clogging of the phosphate filter. .

The technical gist of the present invention is to remove the pad nitride layer through primary wet etching using a phosphoric acid solution when forming an isolation layer, and to remove the remaining pad nitride layer and a part of the pad oxide layer from the second wet type using a phosphoric acid solution and a fluorine-based solution. It is to be removed by the etching process, it is possible to solve the problems in the prior art through this technical means.

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

3A through 3F are process flowcharts illustrating a process of etching a pad nitride layer and a pad oxide layer during formation of a device isolation layer according to an embodiment of the present disclosure. Referring to these drawings, a semiconductor device may be manufactured according to example embodiments. Explain how.

Referring to FIG. 3A, a pad oxide film 302 and a pad nitride film 304 are sequentially formed on the entire upper surface of the semiconductor substrate 300. Here, the pad oxide film 302 is formed to a thickness of 160 kPa-180 kPa, the pad nitride film 304 is formed to a thickness of 1600 kPa-2000 kPa, and the pad oxide film 302 is a high temperature phosphoric acid of approximately 155 ° C. In the case of etching using a solution, an additional thickness of 20 kW-40 kW can be further grown, since the thickness is excessively measured according to the damage of the boundary portion due to the high temperature phosphoric acid etching process.

After the photoresist is applied on the semiconductor substrate 300 on which the pad oxide film 302 and the pad nitride film 304 are sequentially formed, a photolithography process (for example, exposure, development, etc.) is performed to perform device isolation regions. A photoresist pattern (not shown) defining the photoresist pattern is formed, and the pad nitride film 304 and the pad nitride film 302 are dry-etched by reactive ion etching (RIE) or the like according to the photoresist pattern, as shown in FIG. 3B. Likewise, the semiconductor substrate 300 is exposed. Thereafter, a predetermined ashing process using ions such as N and O is performed to remove the photoresist pattern.

Next, using the pad nitride film 304 as a hard mask, dry etching is performed by reactive ion etching or the like to a predetermined depth of the semiconductor substrate 300 to form an isolation trench 306 as shown in FIG. 3C.

Subsequently, in order to protect the semiconductor substrate 300 on the sidewalls and the bottom of the trench 306, a liner oxide layer 308 is formed through an oxidation process using a thermal oxidation method and the like, and the inside of the trench 306 is formed of an insulating material, for example, HDP. (High Density Plasma) oxide film, TEOS (Tetra Ethyl Ortho Silicate) oxide film, and the like, and then, the upper surface thereof is planarized by chemical mechanical polishing (CMP) or the like to expose the pad nitride film 304 as shown in FIG. 3D. The device isolation layer 310 is formed. In this case, the device isolation layer 310 formed in FIG. 3D is formed to have a thickness of 4000 kPa-4500 kPa.

The pad nitride layer 304 is removed as shown in FIG. 3E by performing a primary wet etching process using a phosphoric acid solution (H 3 PO 4). At this time, even after the pad nitride film 304 is removed through a wet etching process, the pad nitride film residue 304a remains on the surface of the pad oxide film 302. Here, the phosphoric acid solution is a solution of approximately 80% to 85%, the wet process is carried out at a high temperature of more than 150 ℃, the seasoning process can be performed before the wet etching process using the phosphoric acid solution, for example For example, seasoning is performed using at least 48 wafers on which a nitride film is formed on a phosphate bath, and since the etching rate of the oxide film of the phosphoric acid solution is excessively high initially, the nitride is diluted in the phosphoric acid solution, thereby reducing the etching rate of the oxide film by approximately 0.5 to 1.5. It can be kept at Å / min.

In this case, in FIG. 3E, the device isolation layer 310 has a thickness of 2000 kPa-2500 kPa, and the etching rate of the nitride film is kept constant regardless of the number of times of use with the phosphate solution, for example, 45%-55%. Overetching of the range can be performed.

Next, a second wet etching process using a phosphoric acid solution or the like is performed to remove the remaining pad nitride film residue 304a and a part of the pad oxide film 302 to include the device isolation film 310 as illustrated in FIG. 3F. A semiconductor device is manufactured. At this time, the secondary wet etching process removes the remaining pad nitride film 304a and the part of the pad oxide film 302 by using a phosphoric acid solution, as shown in FIG. 4. At this point in time, a fluorine-based solution (e.g., HF, etc.) is added to maintain the etching rate with respect to the pad oxide film 302. In FIG. 3F, the pad oxide film 302 has a thickness of 140 kPa to 160 kPa. It has a thickness, and the device isolation layer 310 has a thickness of 2000 Å-2500 Å.

Here, in the etching amount of the pad nitride residue 304a in which the etching rate of the pad oxide film 302 using the phosphoric acid solution is reduced, the etching rate of the oxide film is approximately 0.3 when the nitride film of 8 inches is continuously etched in the phosphoric acid solution. The thickness of the nitride film lowered to / min or less is approximately 800000 mW (wafer long life x nitride film thickness), and a fluoroin solution in a ratio of 100: 1 since the nitride film is etched in the phosphoric acid solution of about 800000 mW or more (for example, , HF solution, etc.) is added to the phosphoric acid solution for 10 cc / min-100 cc / min, it is possible to prevent the phosphate filter clogging phenomenon by the oxide film by the added fluorine-based solution (HF solution). 5A and 5B illustrate a conventional wet etching process and a phosphate filter according to a wet etching process of the present invention, and FIG. 5A illustrates a conventional wet etching process without using a fluorine-based solution. 5 is a view illustrating a phosphate bath filter, and FIG. 5B illustrates a phosphate bath filter in a wet etching process according to the present invention using a fluoroin solution.

In addition, when wet etching is performed by a hot phosphoric acid solution and a fluorine-based solution, particles may be caused in a subsequent process due to hydrophobicity of the wafer surface. The phosphate bath for removing the pad nitride film residue 304a and the pad oxide film 302 may be maintained at 100 ° C. to 120 ° C. lower than 120 ° C., which is the boiling point of the fluorine-based solution (HF solution). In addition, when ammonia (NH 4 OH) is added, wet etching may be performed at a temperature of 80 ° C.-100 ° C. lower than 100 ° C. SC1 is a cleaning solution for removing particles and contaminants at a temperature of 75 ° C. to 90 ° C. by mixing ammonia (NH 4 OH), hydrogen peroxide (H 2 O 2), and water (H 2 O) at a constant ratio. Etching reaction by ammonia occurs at the same time, the surface oxidation by hydrogen peroxide serves to reduce the roughness of the silicon wafer surface.

Therefore, by removing the pad nitride layer, which is used as a hard mask, through the first wet etching process and forming the device isolation layer by removing the pad nitride layer residue and a part of the pad oxide layer through the second wet etching process, the device isolation layer is formed through the second wet etching process. The yield of a semiconductor element can be improved.

In the foregoing description, the present invention has been described with reference to preferred embodiments, but the present invention is not necessarily limited thereto. Those skilled in the art will appreciate that the present invention may be modified without departing from the spirit of the present invention. It will be readily appreciated that branch substitutions, modifications and variations are possible.

1 is a graph showing an etching rate of a nitride film in a conventional wet etching using a phosphoric acid solution,

Figure 2 is a graph showing the etching rate of the oxide film in the conventional wet etching using a phosphoric acid solution,

3A to 3F are process flowcharts illustrating a process of etching a pad nitride layer and a pad oxide layer during formation of an isolation layer according to an embodiment of the present invention;

4 is a graph showing an etching rate of an oxide film to which a fluorine-based solution is added in wet etching using a phosphoric acid solution according to the present invention;

5A and 5B are views illustrating a phosphate bath filter according to a conventional wet etching process and a wet etching process of the present invention.

Claims (9)

Sequentially forming a pad oxide film and a pad nitride film on the semiconductor substrate; Patterning the pad oxide layer and the pad nitride layer to expose the semiconductor substrate in an isolation region; Forming a device isolation trench using the patterned pad nitride layer as a hard mask; Filling the inside of the trench with an insulating material and then planarizing an upper portion thereof to form an isolation layer; Removing the pad nitride layer through primary wet etching using a phosphoric acid solution after forming the device isolation layer; Removing the pad nitride film residue and the portion of the pad oxide film remaining after the first wet etching through the second wet etching using the phosphoric acid solution and the fluorine-based solution Method for manufacturing a semiconductor device comprising a. The method of claim 1, The manufacturing method, Seasoning the phosphoric acid solution and the nitride film before performing the first wet etching; Method of manufacturing a semiconductor device further comprising. The method according to claim 1 or 2, The manufacturing method may include forming a liner oxide layer on sidewalls and bottoms of the trenches after forming the device isolation trenches. Method of manufacturing a semiconductor device further comprising. The method of claim 3, wherein The secondary wet etching is performed by adding the fluorine-based solution to the phosphoric acid solution at a time when the etching rate of the pad oxide film is reduced. The method of claim 4, wherein The second wet etching is a method of manufacturing a semiconductor device, characterized in that the temperature of the bath containing the phosphoric acid solution and the fluorine-based solution is maintained in the range of 100 ℃-120 ℃. The method of claim 3, wherein The secondary wet etching is performed by adding the fluorine-based solution and SC1 (Standard Cleaning-1) to the phosphoric acid solution at a time when the etching rate of the pad oxide film is reduced. The method of claim 6, The secondary wet etching is a method of manufacturing a semiconductor device, characterized in that the temperature of the bath containing the phosphoric acid solution, the fluorine-based solution and the SC1 is in the range of 75 ℃-90 ℃. The method of claim 3, wherein The second wet etching is performed by adding the fluorine-based solution and ammonia to the phosphoric acid solution at a time when the etch rate of the pad oxide film is decreased. The method of claim 8, The secondary wet etching is a method for manufacturing a semiconductor device, characterized in that the temperature of the bath containing the phosphoric acid solution, the fluorine-based solution and the ammonia is maintained in the range of 80 ℃ to 100 ℃.

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