KR20140091327A

KR20140091327A - Method for cleaning wafer

Info

Publication number: KR20140091327A
Application number: KR1020130003474A
Authority: KR
Inventors: 백승원; 이승재
Original assignee: 주식회사 엘지실트론
Priority date: 2013-01-11
Filing date: 2013-01-11
Publication date: 2014-07-21

Abstract

The wafer cleaning method of the present embodiment is a wafer cleaning method comprising a first cleaning step of cleaning the wafer using an alkaline cleaning liquid, a second cleaning step of cleaning the wafer with an acidic cleaning liquid after the first cleaning step, And a third cleaning step of cleaning the wafer using an alkaline cleaning liquid after the second cleaning step.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a method of cleaning a wafer, and more particularly, to a cleaning method capable of suppressing the surface state from becoming hydrophobic after wafer cleaning and reducing contamination of the wafer surface.

Silicon wafers are contaminated by various contaminants in the process of wafer manufacturing process and semiconductor process for device integration. Typical contaminants include fine particles, organic contaminants, metal contaminants, and the like. These contaminants cause the production yield of semiconductor devices to deteriorate. Therefore, in the production of a bare silicon wafer, a cleaning process is performed after a mirror polishing process using CMP (Chemical Mechanical Polishing) and after a unit semiconductor process in which a lot of contaminants are generated at the time of manufacturing a semiconductor device, To an appropriate level.

On the other hand, due to increase in the number of cleaning processes due to the increase of the size of the silicon wafers and the reduction of the design rule, the amount of chemical used in the cleaning process is also increasing.

A widely used silicon wafer cleaning method to date is the RCA cleaning method which is classified by the wet cleaning method.

In the conventional cleaning method, several cleaning steps are simply performed. During the cleaning step using each cleaning liquid, a rinsing process is performed to remove the used cleaning liquid from the surface of the wafer.

However, at the end of a conventional general cleaning process, acid cleaning wafers are used to clean the wafer surface, which causes the surface of the wafer to become hydrophobic, causing additional metal / particle contamination of the wafer surface and stain failure This is a problem that often arises.

The present invention has been proposed in order to solve the problems in the conventional cleaning process, that is, the problem that the surface of the wafer becomes hydrophobic by using an acidic cleaning liquid in the final cleaning process.

In particular, a cleaning method capable of improving the quality of a product by causing the surface of the wafer, which has been subjected to the cleaning process, to be hydrophilized even if it is performed a plurality of times for wafer cleaning.

The wafer cleaning method of this embodiment as proposed is a wafer cleaning method comprising: a first cleaning step of cleaning the wafer using an alkaline cleaning liquid; A second cleaning step of cleaning the wafer using an acidic cleaning liquid after the first cleaning step; And a third cleaning step of cleaning the wafer using an alkaline cleaning liquid after the second cleaning step.

The wafer cleaning method of the present invention has an advantage that the wafer has hydrophilicity even after the cleaning process of the wafer is completed, thereby stabilizing the wafer surface.

Also, during the final cleaning, it is possible to prevent re-contamination of the metal through the addition of EDTA, and it is also possible to achieve the effect of removing the metal.

1 is a flow chart showing the flow of a wafer cleaning method according to an embodiment of the present invention.
FIG. 2 is a graph comparing the amount of Fe remaining on the wafer surface with the conventional one when the wafer cleaning method according to the embodiment of the present invention is applied.
FIG. 3 is a graph comparing the amount of Cu remaining on the surface of a wafer when a wafer cleaning method according to an embodiment of the present invention is applied.

Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings. It should be understood, however, that the scope of the inventive concept of the present embodiment can be determined from the matters disclosed in the present embodiment, and the spirit of the present invention possessed by the present embodiment is not limited to the embodiments in which addition, Variations.

1 is a flow chart for explaining a wafer cleaning method according to an embodiment of the present invention.

First, the cleaning process of the present embodiment mainly includes a first cleaning process (S110) for cleaning the wafer using an alkaline cleaning liquid, and a second cleaning process (S110) for cleaning the wafer using an acidic cleaning liquid A second cleaning step (S130) for cleaning the wafer; and a third cleaning step (S150) for cleaning the wafer using an alkaline cleaning liquid after the second cleaning step.

Then, after the first to third cleaning processes are completed, rinse processes (S120, S140, S160) for removing the cleaning liquid from the wafer surface, respectively, are performed.

The method of the present invention for cleaning wafers with such a flow will now be described in more detail.

In detail, the first cleaning step (S110) is a step for removing dust particles and sludge adhering to the surface of the wafer. As the cleaning liquid used in the first cleaning step (S110), it is preferable to mix a surfactant of pH 12 with potassium hydroxide (KOH) and deionized water. The surfactant is a substance that adsorbs at the interface in a dilute solution and reduces the surface tension thereof. Mixing of the cleaning liquid with the hydrophilic and hydrophobic groups in one molecule can be performed more efficiently.

Further, the cleaning tank in which the first cleaning step (S110) is performed is composed of an inner cleaning tank and an outer cleaning tank for cleaning the wafers, and the cleaning liquid introduced into the inner cleaning tank continuously overflows into the outer cleaning tank. The external cleaning tank has a circulation structure for supplying the cleaning liquid again to the internal cleaning tank, so that the mixing of the cleaning liquid for cleaning the wafer is further facilitated.

In addition, it is preferable to perform the cleaning at a temperature of 50 to 60 ° C because the cleaning power is reduced when the temperature is low in the first cleaning step (S110), and the surface is damaged by overetching the wafer when the temperature is high. Under the above conditions, the wafer is chemically cleaned with a cleaning liquid, and an ultrasonic vibrator is provided to physically clean the surface of the wafer. The particles and sludge remaining on the wafer surface can be easily cleaned by the ultrasonic cleaning.

Subsequently, the first rinsing step (S120) is performed. The first rinsing process (S120) is performed by sequentially performing the first, second, and third cleaning processes (S110, S130, and S150), and the wafer surface is subjected to ultrafiltration A step of removing the remnants of the cleaning liquid used in the immediately preceding cleaning step on the surface of the silicon wafer is commonly performed. The first rinsing step (S120) proceeds at a room temperature of 27 占 폚, and ultrapure water supplied to the cleaning tank is continuously overflowed in the cleaning tank, thereby preventing re-contamination of the silicon wafer. The first rinsing step (S120) is preferably carried out simultaneously with the ultrasonic cleaning in order to enhance the cleaning power.

Next, the second cleaning step (S130) will be described. In the acid cleaning step in which a cleaning liquid is prepared by mixing hydrofluoric acid (HF) and hydrogen peroxide (H ₂ O ₂ ₎ , metal impurities remaining on the surface of the silicon wafer are removed Process. The second cleaning step (S130) is preferably carried out at room temperature (27 ° C) because of the generation of heat of vaporization due to the use of highly reactive hydrofluoric acid and hydrogen peroxide as a cleaning liquid. Further, similarly to the first cleaning step (S110), the cleaning liquid having an internal cleaning tank and an external cleaning tank is provided, and the cleaning liquid overflowed in the internal cleaning tank is supplied to the internal cleaning tank again from the external cleaning tank to improve the mixing efficiency of the cleaning liquid .

Subsequently, the second rinsing step (S140) is performed to prevent the cleaning liquid used in the second cleaning step (S130) from remaining on the surface of the wafer, as in the first rinsing step (S120) , The ultra pure water supplied to the cleaning tank is continuously overflowed in the cleaning tank, thereby preventing re-contamination of the silicon wafer.

Next, the third cleaning step (S150) will be described in detail. The third cleaning step (S150) is a step for making the surface hydrophilic in order to prevent the metal surface from being re-contaminated by removing metal impurities in the second cleaning step (S130).

For this purpose, potassium hydroxide (KOH) and hydrogen peroxide (H ₂ O ₂ ) are added with EDTA (chelate) as a cleaning solution. The chelate is a colorless crystalline powder of the formula C ₁₀ H ₁₆ N ₂ O ₈ , ethylenediaminetetraacetic acid. The solubility in water is 1.2 g dissolved in 100 ml of water at 22 ° C, It has the characteristic of making a stable water-soluble chelate.

Since the hydrofluoric acid used in the second cleaning step (S130) removes the oxide film formed on the surface of the silicon wafer, the surface of the wafer from which the oxide film is removed becomes hydrophobic. Therefore, after using the acidic cleaning liquid containing hydrofluoric acid, it is preferable to make the surface of the silicon wafer hydrophilic by using a basic cleaning liquid containing potassium hydroxide (KOH) as in the third cleaning step (S150). Further, since the chelate binds to the chelate by the metal ions that can remain in the cleansing bath, it is possible to prevent further contamination by metal impurities.

The third cleaning step (S150) is preferably performed at a temperature of 50 to 60 캜. In order to enhance the mixing effect of the cleaning liquid, as in the first and second cleaning processes, an internal cleaning tank and an external cleaning tank are provided and a circulation structure for supplying the cleaning liquid overflowed from the internal cleaning tank from the external cleaning tank to the internal cleaning tank As shown in Fig.

Next, the third rinsing step (S161) is performed to prevent the cleaning liquid used in the third cleaning step (S150) from remaining on the surface of the wafer, and it is preferable that the third rinsing step (S161) proceeds at a room temperature of 27 deg. Further, the ultra pure water supplied to the cleaning tank is continuously overflowed in the cleaning tank, thereby preventing re-contamination of the silicon wafer.

Subsequently, a fourth rinsing step (S162) is performed. The fourth rinsing step (S162) may be a final rinsing step, and may proceed at a temperature of 55 ° C after the third rinsing step (S161).

After completing the above-described cleaning process, the silicon wafer is moved to the top of the cleaning bath at a speed of 1 mm / s, and the surface of the silicon wafer is naturally dried according to the above-described speed.

FIG. 2 is a graph comparing the residual amount of Fe metal when the wafer is cleaned according to the present embodiment and when the cleaning is performed by the conventional method, and FIG. 3 is a graph And a residual amount of Cu metal when cleaning was performed by a conventional method.

Referring to FIG. 2, in the case where the final cleaning step is performed by a cleaning process according to an embodiment of the present invention, compared to the case where cleaning with an acidic cleaning liquid containing hydrofluoric acid (HF) is performed, (Fe) was relatively small.

Similarly, as shown in FIG. 3, it can be confirmed that the amount of copper (Cu) remaining on the surface of the silicon wafer is relatively small when the cleaning process is performed through the embodiment of the present invention.

Therefore, according to the wafer cleaning method of the present invention, it is possible to prevent re-contamination of the metal by performing the hydrophilicization process using the alkaline cleaning liquid, and the advantage of removing the metal through addition of EDTA is also advantageous have.

Further, even after the cleaning process of the wafer is completed, the wafer is made hydrophilic and the surface of the wafer is stabilized.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications other than those described above are possible. For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

As a wafer cleaning method,
A first cleaning step of cleaning the wafer using an alkaline cleaning liquid;
A second cleaning step of cleaning the wafer using an acidic cleaning liquid after the first cleaning step; And
And a third cleaning step of cleaning the wafer using an alkaline cleaning liquid after the second cleaning step.

The method according to claim 1,
Wherein the first cleaning step uses a cleaning liquid in which a surfactant, KOH, and deionized water are mixed.

3. The method of claim 2,
Wherein the first cleaning step is performed in a range of 50 占 폚 to 60 占 폚.

The method according to claim 1,
Wherein the second cleaning step uses a cleaning liquid in which HF, H ₂ O ₂ and ultrapure water are mixed.

5. The method of claim 4,
Wherein the second cleaning step is performed at a room temperature.

The method according to claim 1,
Wherein the third cleaning step uses a cleaning liquid in which KOH, EDTA, H ₂ O _2, and DI are mixed.

The method according to claim 6,
Wherein the third cleaning step is performed in a range of 50 캜 to 60 캜.

The method according to claim 1,
After the third cleaning step is completed,
A step of rinsing the wafer with DI at room temperature and a step of rinsing with DI in a range of 50 DEG C to 60 DEG C are further performed.