KR100255168B1 - Method of cleaning a contact hole in a semiconductor device - Google Patents

Abstract

PURPOSE: A method for cleaning a contact hole of a semiconductor device is provided to remove a natural oxide layer from a contact surface within a short time after removing an organic material and metallic impurity and minimize a damage of a chemical vapor deposition oxide film of a sidewall. CONSTITUTION: A gate(12) is formed on a silicon substrate(11). A gate spacer oxide layer(14) for forming an LDD(Lightly Doped Drain) structure(13) is formed thereon. A planarization process is performed by using an inter-poly oxide film and a BPSG layer(15). A contact hole is formed by a contact mask and an etching process. The ozonized water is formed by implanting ozone gas into pure water with a temperature of 5 to 10 degrees centigrade. An organic material and metallic impurities are removed from a contact hole by utilizing an overflow method using the ozonized water. A natural oxide layer is removed from a surface of a contact by utilizing the overflow method using low density fluoric acid chemicals. A cleaning process is performed by using pure water. A dry process is performed.

Description

Method of cleaning a contact hole in a semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning process applicable to all semiconductor devices, and more particularly to a method of cleaning contact holes in semiconductor devices.

In the conventional semiconductor device manufacturing process, the source and the drain are formed with a shallow junction of 0.08 μm in the 256M class in which the device is highly integrated, and the final contact hole size is 0.15 micrometer or less. In addition, in the 1G class devices, very shallow junctions such as 0.06 μm and 0.1 μm and very narrow contact holes are required. As the junction depth becomes shallower, the contact hole size decreases drastically, which causes a large increase in contact resistance. Also, before forming the bit lines and storage nodes, the first polysilicon layer for the gate electrode and the second polysilicon layer for the bit line, the first polysilicon layer for the gate electrode and charge storage are generally used. In order to prevent electrical breakdown of the third polysilicon layer for the electrode, the second polysilicon layer for the bit line and the third polysilicon layer for the charge storage electrode, a spacer oxide film using a cvd oxide film ( spacer oxide film). However, the wet cleaning process using hydrofluoric acid (HF) or BOE (Buffered Oxide Exchant) solution removes not only the natural oxide layer but also the CVD oxide film on the contact sidewalls. The first polysilicon layer for the gate electrode and the second polysilicon layer for the bit line, the first polysilicon layer for the gate electrode and the third polysilicon layer for the charge storage electrode, and the second polysilicon layer for the bit line and the charge Electrical breakdown of the third polysilicon layer for storage electrodes has a significant effect on the yield improvement and characteristics of the device. Therefore, in order to suppress the growth of the native oxide film of the contact (contact), a nitrogen purge (N ₂ purge box) or a load lock system (attach) is attached to the deposition tube, but not completely controlled. Therefore, in the next generation of ultra-high density devices, the resistance of the source / drain layer is increased, and when the gate length is very small, these resistances are used for the conductance characteristics and driving of the device. Control of contact resistance is a very important issue because it leads to a reduction in capability.

The technology currently used in the semiconductor manufacturing process uses a combination of various cleaning methods as a cleaning method for removing natural oxides, oxides, contaminants, that is, inorganic matters such as organic substances and metallic residual impurities. Primary sulfuric acid solution (piranha) mixed with sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) to remove particulates and organics, or ammonia water (NH ₄ OH) and hydrogen peroxide (H ₂₎ After washing with ammonia solution (SC1) mixed with O ₂ ) and deionized water, it is washed with QDR (Quick Dump Rinse) method. Secondly, the oxide film is washed with hydrofluoric acid (HF) or BOE (Buffered Oxide Exchant) solution to remove the oxide film, and then washed with overflow using deionized water. In order to remove the inorganic material, the third step is washed with a hydrochloric acid solution in which hydrochloric acid (HCl), hydrogen peroxide solution (H ₂ O ₂ ), and deionized water are mixed. In recent years, the purity of chemicals has improved, and the third cleaning process is not performed. The wafer is then dried in a dryer. Such cleaning methods have consumed a large amount of chemicals, have a long cleaning time, and as the size of the wafer increases, the size of the cleaning equipment itself increases, thereby decreasing productivity by occupying a large area of a clean room. In addition, the conventional contact hole cleaning process removes organic and inorganic substances on the contact surface with a high temperature sulfuric acid solution (piranha) at 130 ° C. As it grows, the dip time in the hydrofluoric acid (HF) or BOE (Buffered Oxide Exchant) solution, which is a subsequent natural oxide removal process, is increased. Therefore, the loss of the cvd oxide film, which is an insulating film between the electrodes on the sidewalls of the contact hole, is increased, so that the first polysilicon layer for the gate electrode and the second polysilicon layer for the bit line and the gate electrode Electrical breakdown of the first polysilicon layer, the third polysilicon layer for the charge storage electrode, and the second polysilicon layer for the bit line and the third polysilicon layer for the charge storage electrode is caused, thus affecting the characteristics of the device. Also give.

The present invention provides a loss of a chemical vapor deposition oxide film on a sidewall while completely removing a natural oxide film chemically formed on a contact surface in a short time after removing organic matter and metallic impurity. The purpose is to minimize this.

The contact hole cleaning method of the semiconductor device according to the present invention for achieving the above object is to remove the organic matter and metallic impurities in an overflow method through the cleaning using cold ozone water injecting ozone gas into the deionized water. And a step of removing the natural oxide film on the contact surface in an overflow method with a low concentration of hydrofluoric acid-based chemical, washing with pure water, and drying.

1 and 2 are cross-sectional views for explaining a contact hole cleaning method according to the present invention.

<Description of the symbols for the main parts of the drawings>

11 and 21: silicon substrate 12 and 22: gate layer

13 and 23: LDD structure layer

14 and 24: gate spacer oxide

15 and 25: interpoly oxide (IPO) and BPSG layers

26 second polysilicon layer for bit line 27 tungsten silicide (W-Si) layer

28: third polysilicon layer for charge storage electrode

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

1 is a cross-sectional view of a device illustrating a process of forming a contact hole for explaining a process of cleaning by the method according to the present invention. First, a gate 12 is formed on the silicon substrate 11, and then a gate spacer oxide 14 layer is formed to form the LDD structure 13, and an inter poly oxide film is formed. And a planarization process using the BPSG layer 15. Next, contact holes are formed by a contact mask and an etching process.

First, in order to remove particles, organic matter, and inorganic matter, it is washed by an overflow method using chilled ozone water in which ozone gas is injected into deionized water of 5 ° C to 10 ° C. Since this method is performed at a lower temperature than the conventional washing process using a high temperature sulfuric acid solution (piranha) or ammonia water solution (NH ₄ OH) of about 130 ℃, the thickness of the natural oxide film grown in the solution can be limited to within 4 kPa. . Therefore, it is possible to use the hydrofluoric acid-based solution in low concentration in the subsequent step of removing the natural oxide film. In the case of hydrofluoric acid (HF) solution, the mixing ratio of distilled water (H ₂ O) and hydrofluoric acid (HF) is diluted to 100 to 500: 1, and in the case of BOE (Buffered Oxide Exchant) solution, NH ₄ F and hydrofluoric acid (HF) The mixture ratio is diluted to 100-500: 1 and used. In this process of the present invention, even when the dip time is short, the chemical vapor deposition oxide film on the sidewall of the contact hole is completely removed while completely removing the fine particles, organic and inorganic materials, and the natural oxide film formed on the contact hole surface. (chemical vapor deposition oxide film) losses can be minimized. Thereafter, an overflow cleaning process and a drying process using pure water are performed.

FIG. 2 is a cross-sectional view of a device showing the steps after cleaning by the method according to the present invention. 26) shows a cross section of a stable device in which the electrical insulation properties of the first polysilicon layer 22 for the gate electrode and the third polysilicon layer 28 for the charge storage electrode are not destroyed.

As described above, according to the present invention, when the contact cleaning process using the above process is performed, the natural oxide film formed on the contact portion is completely removed, and in particular, a chemical agent of low concentration hydrofluoric acid is used. Uniformity is improved and contact resistance can be minimized by minimizing the loss of the spacer oxide film formed on the sidewalls, thereby greatly improving device characteristics. In addition, pure water and ozone gas are used in place of chemicals such as sulfuric acid (H ₂ SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) to reduce chemical consumption and simplify the process to reduce cleaning time and equipment size. It is possible to miniaturize.

Claims (6)

Removing organic matter and metallic impurities in the contact hole in an overflow manner by washing with ozone water in which ozone gas is injected into pure water maintaining a temperature of 5 ° C to 10 ° C, Using a low concentration hydrofluoric acid chemical to remove the natural oxide film on the contact surface in an overflow manner; A contact hole cleaning method for a semiconductor device, characterized in that the step of performing a cleaning process using pure water and then drying. The method of claim 1, wherein the concentration of ozone gas injected into the ozone water is 20 ppm to 30 ppm. The method of claim 1, wherein the overflow ratio of the low temperature ozone water is 5LPM to 10LPM. The method of claim 1, wherein the low concentration hydrofluoric acid solution is a hydrofluoric acid (HF) solution in which distilled water (H ₂ O) and hydrofluoric acid (HF) are mixed in an amount of 100 to 500 to 1. The method of claim 1, wherein the low concentration hydrofluoric acid-based solution is a BOE solution in which NH ₄ F and hydrofluoric acid (HF) are mixed at a ratio of 100 to 500 to 1. The method of claim 1, wherein the native oxide film is removed by controlling the low concentration hydrofluoric acid chemical at an overflow ratio of 5 LPM to 10 LPM in a range of 20 ° C to 30 ° C.

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