JP2001053052A - Chemical cleaning of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a novel method for chemically cleaning a semiconductor wafer. SOLUTION: The method for chemically cleaning a semiconductor wafer includes a stage S20 of cleaning a wafer by a first wet chemical cleaning step, a stage S30 of drying the wafer to remove a moisture therefrom, a stage S40 of cleaning the wafer by a second wet chemical cleaning step, and stage S50 of drying the wafer to remove a moisture therefrom. And a chemical cleaning apparatus for implementing the method is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method, and more particularly to a method for cleaning a semiconductor wafer.

[0002]

2. Description of the Related Art In a manufacturing process of an ultra-super LSI (ULSI), a silicon wafer is placed in a high-temperature furnace and subjected to a diffusion or thermal oxidation process, before a CVD process, or after a thin film is etched. In any case, it is necessary to increase the cleanliness of the surface to a required level by going through the steps of chemical cleaning, rinsing with deionized water, and drying. For this reason, wafer cleaning technology can be said to be one of the important factors affecting the yield of a wafer maker and the quality and reliability of a product. The main purpose of this cleaning is to remove foreign substances on the wafer surface, such as fine particles, organic substances, and inorganic metal ions.

[0003] Among the techniques for cleaning wafers, the conventional R
The CA cleaning method is most commonly used. FIG. 1 shows the process.

[0004] According to the chemical cleaning apparatus 10 shown in FIG. 1, the apparatus includes a wafer load / unload unit (I).
/ O) 30, the wafer to be cleaned is loaded into the chemical cleaning apparatus 10 for cleaning, and then the wafer is sent to a plurality of modules 1, 2, and 3 using the mechanical arm 12, Perform a rinse. Here, a cleaning process including removal of a natural oxide film will be described as an example, and the description will be given in accordance with the order of a standard RCA cleaning technique. First, a wafer is sent to the module 1. Module 1
Is a chemical washing tank 11 having SC-1 solution and a water washing tank (Q
DR) 14, wherein the SC-1 solution employs an APM (NH ₄ OH / H ₂ O ₂ ) mixture and has low removability to metal impurities, but fine particles on the silicon wafer surface. , A high removal effect can be obtained.
After cleaning in the chemical cleaning tank 11, this time, the wafer is sent to a water cleaning tank (QDR) 14 and subjected to quick dump rinsing to prevent the SC-1 solution from remaining. It is sent to the module 2. The module 2 includes a chemical cleaning tank 13 having an SC-2 liquid and a water washing tank (QDR) 16, wherein the SC-2 liquid has an HPM (HCl / H ₂ O ₂ ) formulation. As a result, metal impurities on the wafer surface can be effectively removed. After cleaning in the chemical cleaning tank 13, the wafer is then washed in the water washing tank (QDR).
16 to perform quick dump rinsing.
Prevent liquid C-2 from remaining.

However, in the above-mentioned chemical cleaning process,
Means that hydrogen peroxide solution (H₂O ₂) Such as strong oxidation
Decomposes easily to form oxygen atoms due to mixing of chemicals
As a result, a natural oxide film is formed on the wafer surface.
I will. Therefore, taking the contact method as an example,
After the window is formed, a metal or polysilicon plug
Before forming the oxide, first remove the natural oxide film
It is necessary to prevent the occurrence of a poor contact resistance. this
Therefore, hydrofluoric acid is generally used as the final stage of the cleaning process.
Immersion process (DHF / BHF-LAST)
Step to send wafer to module 3
Have been. Here, the module 3 is made of hydrofluoric acid.
Aqueous solution or buffered hydrofluoric acid solution (DHF / BHF)
Cleaning tank 15 having a water washing tank (QDR) 1
8 is provided. Hydrofluoric acid aqueous solution diluted 100: 1
(DHF solution) or by adding ammonium fluoride
Buffered hydrofluoric acid solution (BHF solution)
By immersing for a short period of time,
After removing the oxide film, the wafer is washed in the washing tank (QD
R) Send it to 18 for quick dump rinsing.
Prevent the chemical solution (DHF / BHF) from remaining.

Subsequently, after a final rinsing (not shown), the wafer is sent to a dryer (DRYER) 20 by the mechanical arm 12 and dried. In order to prevent the wafer from being unloaded without going through the drying process, this chemical cleaning device uses a dryer (DRYER).
20 is set as the final stage. Therefore, once dried, the wafer is always unloaded and never returned to a module in the apparatus.

However, in the above-mentioned chemical cleaning method, for example, as in the modules 1, 2 and 3, the SC-1, SC-2 or BHF / DH
In the case where impurities are removed by a different chemical cleaning solution such as F, if the drying treatment is not performed in advance, the moisture remaining on the wafer in the previous washing treatment in the washing tank 14 or 16 of the module 1 or 2 may be caused. In addition, the concentration of the chemical cleaning solution BHF / DHF used in the module 3 changes, and the wafer is also affected. Taking the removal of the natural oxide film formed on the contact window surface as an example, if moisture remains at the bottom of the contact window, the concentration of the hydrofluoric acid solution is diluted, and the etching rate of the top of the contact window is reduced. Is larger than that at the bottom, making it easier for the top of the adjacent contact window to short circuit due to over-etching.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide a novel chemical cleaning method for a semiconductor wafer.

[0009]

In order to achieve the above object, a novel chemical cleaning method for a semiconductor wafer according to the present invention comprises the steps of (a) cleaning a wafer by a first wet chemical cleaning step; b) drying the wafer to remove water; (c) cleaning the wafer by a second wet chemical cleaning process; and (d) drying the wafer to remove water. , Is contained.

In the step (a), the first wet chemical cleaning step preferably uses a solution containing APM (NH ₄ OH / H ₂ O ₂ ).

In the step (a), a solution containing an HPM (HCl / H ₂ O ₂ ) blend may be used in the first wet chemical cleaning step.

In the step (a), the first wet chemical cleaning step preferably includes rinsing using a deionized water (DI) compound.

In the step (c), it is preferable to use a solution containing a hydrofluoric acid aqueous solution (DHF) in the second wet chemical cleaning step.

In the step (c), a solution containing a buffered hydrofluoric acid (BHF) formulation may be used in the second wet chemical cleaning step.

In the step (c), the second wet chemical cleaning step preferably includes rinsing using a deionized water (DI) compound.

Further, a method of cleaning a semiconductor wafer according to another aspect of the present invention includes: (1) cleaning each wafer by at least two types of wet chemical cleaning steps; Cleaning the wafer with a solution, rinsing the wafer with deionized water, and (2) drying the wafer to remove moisture after each wet chemical cleaning step. And

One of the wet chemical cleaning steps is an APM
It is preferable to use a solution containing a (NH ₄ OH / H ₂ O ₂ ) composition.

One of the wet chemical cleaning steps is an HPM
A solution containing a (HCl / H ₂ O ₂ ) formulation may be used.

In one of the wet chemical cleaning steps, a solution containing an aqueous solution of hydrofluoric acid (DHF) may be used.

In one of the wet chemical cleaning steps, a solution containing a buffered hydrofluoric acid (BHF) formulation may be used.

In the chemical cleaning method of the present invention, since the drying treatment is performed between each wet chemical cleaning step, the second wet chemical cleaning step uses a solution to remove water remaining in the first wet chemical cleaning step. Can be prevented from changing, and the wafer can be prevented from being adversely affected.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In order to further clarify the contents and other objects, features, and advantages of the present invention, preferred embodiments will be described below with reference to the drawings.

The present embodiment mainly provides a method for chemically cleaning a semiconductor wafer. This method comprises the steps of (1)
Each wafer is cleaned by at least two types of wet chemical cleaning steps, and these wet chemical cleaning steps include a step of cleaning the wafer with a chemical cleaning solution and a step of rinsing the wafer with deionized water. And (2) after the respective wet chemical cleaning steps, drying the wafer to remove moisture.

Next, the two types of wet chemical cleaning solutions will be described in detail by way of example. FIG. 3 is a flowchart of a method for chemically cleaning a semiconductor wafer according to the embodiment of the present invention, which is an improvement on a conventional RCA cleaning step. This new chemical cleaning method includes the following steps.

First, as shown by S10 in the figure, a chemical cleaning apparatus is provided, and a wafer is loaded. Next, as shown by S20 in the figure, a first wet chemical cleaning step is performed. That is, the wafer is cleaned by removing the fine particles and metal impurities on the wafer using a first wet chemical cleaning solution represented by, for example, SC-1 or SC-2 solution, and then rinsed with deionized water.

Next, as shown by S30 in the figure, the wafer is dried to remove moisture. Then, S in the figure
As shown at 40, a second wet chemical cleaning step is performed. That is, for example, the second liquid represented by BHF / DHF liquid
After removing and cleaning the native oxide film on the wafer using a wet chemical cleaning solution, rinse with deionized water.

Further, as shown by S50 in the figure, the washed wafer is dried to remove moisture. Finally, as shown by S60 in the figure, the wafer is unloaded from the chemical cleaning device.

FIG. 2 is an internal structural view of the semiconductor wafer chemical cleaning apparatus according to the present embodiment.

In the chemical cleaning apparatus 100, a wafer to be cleaned is loaded into the chemical cleaning apparatus 100 for cleaning using a wafer load / unload unit I / O-300. Then, the setting of the conventional chemical cleaning apparatus is changed, and the dryer (DRYER) 200 is regarded as the module 3 so that the wafer is repeatedly inserted into the dryer.

Subsequently, the wafer is sent to a plurality of modules 1, 2, 3, and 4 using the mechanical arm 120, and the wafer is rinsed. Here, the cleaning process including the removal of the natural oxide film will be described as an example, and the description will be given in the order of the cleaning method according to the present embodiment. First, a wafer is sent to the modules 1 and 2, and a first chemical cleaning step is performed. The module 1 includes a chemical washing tank 110 having an SC-1 solution and a water washing tank (QDR) 140, wherein the SC-1 solution is composed of APM (NH ₄ O).
H / H ₂ O ₂ ) is employed, and although the removability for metal impurities is low, a high removal effect is obtained for fine particles on the silicon wafer surface. The chemical cleaning tank 110
After cleaning, the wafer is washed with a washing tank (QD
R) Send it to 140 for quick dump rinse,
The SC-1 solution is prevented from remaining, and then the wafer is sent to the module 2. The module 2
A chemical cleaning tank 130 having an SC-2 solution, and a water cleaning tank (QDR) 160 are provided.
-2 _{solution, HPM (HCl / H 2 O} 2) adopts a formulation, it is possible to effectively remove metal impurities on the wafer surface. After cleaning in the chemical cleaning tank 130,
This time, the wafer is sent to the washing tank (QDR) 160 and subjected to quick dump rinsing to prevent the SC-2 solution from remaining.

In addition, in the above-described chemical cleaning step, since a strong oxidizing agent such as hydrogen peroxide solution (H ₂ O ₂ ) is mixed in the chemical solution, it is likely to be decomposed to generate oxygen atoms, so that A natural oxide film is formed. Therefore, taking the contact method as an example, after forming the contact window and before forming the metal or polysilicon plug, it is necessary to first remove this natural oxide film cleanly to prevent the occurrence of high contact resistance. . For this reason, as a final step of the cleaning step, a module 4 generally called a final immersion step with hydrofluoric acid (DHF / BHF-LAST)
A step of sending the wafer to the wafer is provided.

However, the module 1 or 2
After the rinsing process in the rinsing tanks 140 or 160, the residual water on the wafers causes the wafers to be cleaned in the chemical cleaning tank 15 of the module 4 in the next step.
At 0, the concentration of the chemical cleaning solution BHF / DHF changes, which in turn has an adverse effect on the wafer. Therefore, for a chemical cleaning solution such as BHF / DHF in which a change in concentration is sufficient to affect the wafer, the wafer having moisture remaining is first removed from the module 3 comprising a dryer 200.
Then, it is necessary to remove the water by using the mechanical arm 120 and to dry it.

Subsequently, the wafer is transferred to the module 4
And a second chemical cleaning step is performed. Here, the module 4 includes a chemical cleaning tank 15 having a hydrofluoric acid aqueous solution or a buffered hydrofluoric acid solution (DHF / BHF).
0, and a washing tank (QDR) 180,
By immersing the wafer in a hydrofluoric acid aqueous solution (DHF solution) diluted 100: 1 or a buffered hydrofluoric acid solution (BHF solution) formed by adding ammonium fluoride for a short time, After removing the generated natural oxide film, the wafer is transferred to the washing tank (QDR) 180 and subjected to quick dump rinsing, and the chemical solution D is removed.
Prevents HF / BHF from remaining.

Subsequently, after performing a final rinsing (not shown), the mechanical arm 120 transfers the wafer to a drier (DRYER) 200 in order to prevent the wafer from being unloaded without going through a drying process. Send in and dry.

As can be understood from the above description, when the above-described chemical cleaning method and apparatus are used, for example, as in the modules 1, 2 and 4, the SC-
1. Even when impurities are removed by a different chemical cleaning solution such as SC-2 or BHF / DHF, since the drying treatment in the module 3 has been performed in advance, the water washing tank of the module 1 or 2 before that. 140 or 16
The water remaining in the water washing treatment at 0 has already been dried. Therefore, the next chemical cleaning tank 15 of the module 4 is used.
0, the chemical cleaning solution BHF /
No change occurs in the concentration of DHF. Taking the removal of the natural oxide film formed on the surface of the contact window as an example, since the moisture does not remain at the bottom of the contact window, the concentration of the hydrofluoric acid solution does not change, and the etching rate of the top of the contact window does not change. Is the same as that at the bottom, so there is no problem that the top of the adjacent contact window is shorted due to excessive etching.

While the preferred embodiment has been disclosed above,
These in no way limit the scope of the invention,
Anyone familiar with the art should make various changes and modifications without departing from the spirit and scope of the invention.

[0037]

As described above, the use of the chemical cleaning method and apparatus according to the present invention makes it possible to remove impurities with a different chemical cleaning solution for each wet chemical cleaning step.
Since a new drying process is interposed between processes, the moisture remaining in the previous wet chemical cleaning process causes a change in the concentration of the chemical cleaning solution used in the next wet chemical cleaning process. And the wafer is not adversely affected.

[Brief description of the drawings]

FIG. 1 is an internal structural view of a conventional semiconductor wafer chemical cleaning apparatus.

FIG. 2 is an internal structural view of a semiconductor wafer chemical cleaning apparatus according to an embodiment of the present invention.

FIG. 3 is a flowchart of a method for chemically cleaning a semiconductor wafer according to an embodiment of the present invention.

[Explanation of symbols]

10, 100 chemical cleaning device 12, 120 mechanical arm 11, 13, 15, 110, 130, 150 chemical cleaning tank 14, 140, 16, 160, 18, 180 water washing tank 20, 200 dryer 30, 300 … Wafer loading / unloading section

 ──────────────────────────────────────────────────の Continued on the front page (71) Applicant 599002397 Mosel Vitalic Inc., Taiwan, Sinchu, Science-Based Industrial Park, Ricin Road No. 19 (71) Applicant 599002401 Siemens-Ahr Germany, D- 80333, München, Wittelsbacher Platz 2 (72) Inventor, Toshihiro Peng, Hsinchu-ri, Taiwan 11 Xingxingli, 550, Rinse Nan-ro, 550 Street 12, No.9, 4 (72) Inventor, Zhao Weicheng 75, Middle East Street, Lingya District, Kaohsiung, Taiwan issue

Claims (12)

[Claims] 1. A step of cleaning a wafer by a first wet chemical cleaning step; (b) a step of drying the wafer to remove moisture; and (c) a second wet chemical cleaning step. Cleaning the wafer; and (d)
Drying the wafer to remove moisture. 2. In the step (a), in the first wet chemical cleaning process, APM (NH ₄ OH / H ₂ O ₂ ) is used.
2. The method according to claim 1, wherein a solution containing the compound is used. 3. The method according to claim 1, wherein in the step (a), the first wet chemical cleaning process uses a solution containing an HPM (HCl / H ₂ O ₂ ) formulation. Chemical cleaning method for semiconductor wafers. 4. The method according to claim 1, wherein in the step (a), the first wet chemical cleaning step includes rinsing using a deionized water (DI) formulation. Or a method for chemically cleaning a semiconductor wafer. 5. The method according to claim 1, wherein in the step (c), the second wet chemical cleaning step uses a solution containing a hydrofluoric acid aqueous solution (DHF) formulation. The chemical cleaning method of a semiconductor wafer as described in the above. 6. The method of claim 1, wherein in step (c), the second wet chemical cleaning step uses a solution containing a buffered hydrofluoric acid (BHF) formulation.
5. The method for chemically cleaning a semiconductor wafer according to any one of the above items 4. 7. The method of claim 1, wherein in the step (c), the second wet chemical cleaning step includes rinsing using a deionized water (DI) formulation. Or a method for chemically cleaning a semiconductor wafer. 8. Each wafer is cleaned by at least two types of wet chemical cleaning steps, wherein the wet chemical cleaning step includes a step of cleaning the wafer with a chemical cleaning solution, and a step of cleaning the wafer with deionized water. A chemical cleaning method for a semiconductor wafer, comprising: a step of rinsing the wafer; and (2) after the wet chemical cleaning steps, drying the wafer to remove moisture. 9. The method of claim 1, wherein one of the wet chemical cleaning steps comprises an APM
_{(NH 4 OH / H 2 O} 2) chemical cleaning method of semiconductor wafer according to claim 8, characterized in that using a solution containing a blend. 10. One of the wet chemical cleaning steps is an HP
M (HCl / H₂O ₂Using a solution containing the formulation
9. The semiconductor wafer according to claim 8, wherein
Chemical cleaning method. 11. The method of claim 8, wherein one of the wet chemical cleaning steps uses a solution containing a hydrofluoric acid aqueous solution (DHF) formulation. 12. The method according to claim 8, wherein one of the wet chemical cleaning steps uses a solution containing a buffered hydrofluoric acid (BHF) formulation. .