TW201351498A - Method for cleaning semiconductor wafer - Google Patents

Abstract

This method for cleaning a semiconductor wafer has: a first cleaning step (1) for performing SC1 cleaning with respect to the semiconductor wafer; a second cleaning step (2) for performing HF cleaning with respect to the semiconductor wafer after the first cleaning step (1); and a third cleaning step (3) for cleaning the semiconductor wafer using a hydrogen peroxide solution after the second cleaning step (2). Consequently, nonuniformity of the surface roughness (haze) of the semiconductor wafer due to cleaning is reduced, and the semiconductor wafer can be effectively cleaned.

Description

Semiconductor wafer cleaning method

The present invention relates to a method of cleaning a semiconductor wafer.

As a method of cleaning a semiconductor wafer, a cleaning procedure such as RCA cleaning is often used, and a cleaning procedure such as RCA cleaning is a combination of SC1 cleaning, SC2 cleaning, and HF cleaning; wherein the SC1 washing is performed. The net is washed by a mixed cleaning solution of ammonia water, hydrogen peroxide water (hereinafter also referred to as "hydrogen peroxide") and ultrapure water, which is washed by a mixture of hydrochloric acid, hydrogen peroxide and ultrapure water. The cleaning solution was washed with HF (hydrofluoric acid). For example, Patent Document 1 describes a method of cleaning a semiconductor wafer which is subjected to HF cleaning after SC1 is washed, and then SC1 is washed.

After the particles on the semiconductor wafer are removed by SC1 cleaning, the HF is washed, and the heavy metal in the oxide film and the oxide film generated by the SC1 cleaning is removed to prevent the particles from reattaching. On the surface of the semiconductor wafer, after the HF is washed, the surface of the semiconductor wafer is usually added by using ozone water. To oxidize.

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 11-87281

As described above, when washing with SC1 → HF → ozone water, since the ozone water is extremely unstable, in the ozone water treatment tank of the immersion type cleaning device, the concentration is caused by decomposition over time. decline. Originally, it is preferable that the ozone concentration in the washing tank is uniform, but in fact, a difference in concentration occurs between the newly supplied ozone water and the ozone water in the washing tank in which the concentration is attenuated. As a result, if the bare surface of the HF-treated semiconductor wafer is oxidized by ozone water, unevenness is formed during oxidation due to uneven concentration of ozone water, and the unevenness of the oxidation occurs on the surface of the semiconductor wafer. The roughness (haze) is uneven.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for cleaning a semiconductor wafer, which can reduce unevenness in surface roughness (haze) of a semiconductor wafer due to cleaning, and can effectively Wash the semiconductor wafer.

In order to achieve the above object, the present invention provides a method for cleaning a semiconductor wafer, comprising: a first cleaning step of performing SC1 cleaning on the semiconductor wafer; and a second cleaning step in the first cleaning step After the step, the semiconductor wafer is subjected to HF cleaning; and a third cleaning step is performed in the second cleaning After the net step, the semiconductor wafer is washed by hydrogen peroxide water.

As described above, in the third cleaning step, the semiconductor wafer is cleaned by hydrogen peroxide water (hydrogen peroxide), thereby suppressing the adhesion of the particles to the surface of the semiconductor wafer and the oxidation of the surface of the semiconductor wafer. All. Therefore, the surface roughness (haze) of the semiconductor wafer is not uneven, and the semiconductor wafer can be cleaned, and a higher quality semiconductor wafer can be obtained.

In this case, it is preferred to set the temperature of the hydrogen peroxide water to 20 to 80 °C.

Thereby, it is possible to more effectively suppress the occurrence of oxidative unevenness of the fine particles reattaching to the surface of the semiconductor wafer after cleaning and the surface of the semiconductor wafer.

In this case, it is preferred to set the concentration of the hydrogen peroxide water to 0.1 to 30% by weight.

Thereby, it is possible to more reliably suppress the occurrence of oxidative unevenness in the semiconductor wafer after the cleaning, and it is possible to reduce the burden on the exhaust equipment caused by the evaporation of hydrogen peroxide.

As described above, according to the present invention, the oxidation unevenness of the surface of the semiconductor wafer due to the cleaning can be reduced, the surface roughness (haze) of the semiconductor wafer is not uneven, and the semiconductor can be cleaned. Wafer.

Fig. 1 is a flow chart showing the cleaning of a semiconductor wafer in the present invention.

Fig. 2 is a graph showing the particle size of the ruthenium wafer after washing in the case of changing the liquid temperature in the hydrogen peroxide cleaning in Examples 1 to 9 and Comparative Example 1.

Fig. 3 is a graph showing the particle size of the ruthenium wafer after washing in the case of changing the concentration of the solution in the hydrogen peroxide cleaning in Examples 10 to 15 and Comparative Example 1.

Fig. 4 is a graph showing the results of evaluation of haze and haze unevenness of the tantalum wafer after the first to third cleaning steps in Examples 1 to 6 and Comparative Example 1.

Fig. 5 is a graph showing the haze diagram and the haze unevenness evaluation of the tantalum wafer after the first to third cleaning steps in the seventh to third embodiments.

Fig. 6 is a graph showing the haze diagram and the haze unevenness evaluation of the tantalum wafer after the first to third cleaning steps in the fourteenth to the fifteenth embodiments.

Hereinafter, the present invention will be described in detail with reference to the drawings as an example, but the invention is not limited thereto.

In the cleaning of the polishing agent after the mirror polishing, the present invention is as shown in Fig. 1. First, the semiconductor wafer is SC1 washed by a mixed cleaning solution of ammonia, hydrogen peroxide and water ( First washing step). In the SC1 cleaning, the particles adhering to the surface of the semiconductor wafer are lifted off by etching and removed. Further, in the SC1 washing, the mixing ratio of ammonia, hydrogen peroxide and water, and the temperature of the SC1 washing liquid are not particularly limited. Any of the conditions generally employed can be applied. Further, after the SC1 is cleaned, the semiconductor wafer can be cleaned with pure water.

Next, the semiconductor wafer subjected to SC1 cleaning is subjected to HF cleaning by a HF aqueous solution (second cleaning step). In the HF cleaning, the oxide film on the surface of the semiconductor wafer formed by the SC1 cleaning is removed, whereby the particles on the surface of the semiconductor wafer firmly bonded to the oxide film are peeled off and removed, and can also be removed. Heavy metals in the oxide film. Further, the concentration of the HF aqueous solution is not particularly limited.

The surface of the semiconductor wafer after HF cleaning is a water-repellent surface, and the particles are easily adhered. Therefore, in order to prevent the fine particles from adhering to the surface of the semiconductor wafer, in the present invention, the HF-cleaned semiconductor wafer is washed with hydrogen peroxide by hydrogen peroxide water to oxidize the surface (third cleaning step).

Conventionally, when ozone semiconductor water (10 ppm) is used to clean the surface of a semiconductor wafer, unevenness of haze due to oxidative unevenness occurs on the surface of the semiconductor wafer after cleaning.

On the other hand, in the present invention, hydrogen peroxide water is used instead of ozone water, and the semiconductor wafer is washed with hydrogen peroxide, whereby the particles can be reattached to the surface of the semiconductor wafer, and the surface of the semiconductor wafer can be suppressed. Uneven oxidation. Therefore, the surface roughness (haze) of the semiconductor wafer is not uneven, the semiconductor wafer can be cleaned, and a higher quality semiconductor wafer can be obtained.

Further, in the third washing step of the present invention, it is preferred to set the temperature of the hydrogen peroxide water to 20 to 80 °C.

Thus, if the temperature of the hydrogen peroxide water is 20 ° C or more, The effect of preventing the particles from reattaching to the surface of the semiconductor wafer is improved, so that the level of particles after washing is further improved. In addition, if the temperature of the hydrogen peroxide water is 80° C. or less, since the evaporation amount of the cleaning liquid is kept constant and bubbles are prevented from being added to the cleaning liquid, the semiconductor crystal after washing can be more effectively suppressed. Uneven haze on the circle.

Further, in the third washing step of the present invention, the concentration of the hydrogen peroxide water is preferably set to 0.1 to 30% by weight.

As described above, if the concentration of the hydrogen peroxide water is 0.1% by weight or more, it is possible to suppress the occurrence of unevenness in the semiconductor wafer by the cleaning, and the particle level after the cleaning is improved. In addition, if the concentration of the hydrogen peroxide water is 30% by weight or more, the amount of evaporation of hydrogen peroxide from the cleaning liquid can be appropriately maintained, and the burden on the exhaust equipment can be prevented from increasing.

[Examples]

Hereinafter, the examples and comparative examples of the present invention will be more specifically described, but the present invention is not limited to these examples.

(Example 1)

First, the ruthenium wafer having a diameter of 300 mm, a crystal orientation of <100>, and a P-type of 10 Ωcm is continuously subjected to the following steps: after washing with SC1 (first cleaning step), after cleaning with pure water, The HF washing (second washing step) is carried out by washing with hydrogen peroxide (third washing step). Further, after the completion of the third cleaning step, the germanium wafer after the completion of the cleaning is dried. After the wafer is dried, the particle counter is used to measure the particles of the germanium wafer (≧41nm) and Haze.

At this time, the SC1 cleaning solution used was a mixing ratio of ammonia, hydrogen peroxide (hydrogen hydroxide water), and water of 1:1:10, and the temperature of the SC1 cleaning solution was 70 °C. Further, the HF concentration in the second washing step was set to 1.5%, the hydrogen peroxide concentration in the third washing step was 3.0% by weight, and the temperature of the hydrogen peroxide was set to 10 °C to carry out the first to third washings. Net step.

(Example 2)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 20 °C.

(Example 3)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 30 °C.

(Example 4)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 40 °C.

(Example 5)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 50 °C.

(Example 6)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 60 °C.

(Example 7)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 70 °C.

(Example 8)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 80 °C.

(Example 9)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 90 °C.

(Embodiment 10)

The first to third washing steps were carried out in the same manner as in Example 1 except that the temperature of the hydrogen peroxide in the hydrogen peroxide washing was changed to 80 ° C and the hydrogen peroxide concentration was changed to 0.03 wt %.

(Example 11)

The first to third washing steps were carried out in the same manner as in Example 10 except that the hydrogen peroxide concentration was changed to 0.1% by weight.

(Embodiment 12)

The first to third washing steps were carried out in the same manner as in Example 10 except that the hydrogen peroxide concentration was 0.3% by weight.

(Example 13)

The first to third washing steps were carried out in the same manner as in Example 10 except that the hydrogen peroxide concentration was 1.0 wt%.

(Example 14)

The first to third washing steps were carried out in the same manner as in Example 10 except that the hydrogen peroxide concentration was changed to 10.0% by weight.

(Example 15)

The first to third washing steps were carried out in the same manner as in Example 10 except that the hydrogen peroxide concentration was changed to 30.0% by weight.

(Comparative Example 1)

The first and second washing steps were carried out in the same manner as in the first embodiment. Then, instead of the hydrogen peroxide washing, the cerium wafer was washed with 10 ppm of ozone water.

2 to 6 are the results of Examples 1 to 15 and Comparative Example 1.

As shown in FIGS. 4 to 6 , the wafers are washed in the order of SC1 cleaning, HF cleaning, and hydrogen peroxide cleaning, whereby in Examples 1 to 15, the washing can be reduced. The haze on the surface of the wafer after the net is uneven. In the case of Example 9, the reason why the haze unevenness occurred on the surface of the tantalum wafer after the hydrogen peroxide cleaning was that the hydrogen peroxide temperature was a high 90 °C. Further, in the case of Example 10, the reason why the haze unevenness occurred on the surface of the tantalum wafer after the hydrogen peroxide washing was that the hydrogen peroxide concentration was as low as 0.03 wt%. However, in comparison with Comparative Example 1, Example 9 and Example 10 were able to suppress haze unevenness on the surface of the tantalum wafer.

Further, as shown in Fig. 2, when the temperature of the hydrogen peroxide was 20 to 80 ° C, the amount of fine particles on the surface of the tantalum wafer after the hydrogen peroxide washing was small, which was the same as in Comparative Example 1 after ozone washing. Further, if the temperature of the hydrogen peroxide is lower than 20 ° C, the particles tend to increase. This is because the effect of preventing the particles from reattaching to the germanium wafer is lowered due to the temperature drop of the hydrogen peroxide. Therefore, in Example 1, the number of fine particles deteriorated to 47, but as described above, in the case where ozone water was washed after HF washing, uneven haze was marked, and compared with that after washing with HF In the case of performing hydrogen peroxide washing, Example 1 can improve haze unevenness.

Further, as shown in Fig. 3, in the eighth embodiment and the tenth to fifteenth embodiments, the number of fine particles on the surface of the tantalum wafer after the hydrogen peroxide cleaning was small was about 15 pieces. For example, in Example 8, the number of particles was 17, which was relatively good.

In this manner, the silicon wafer is washed in the order of SC1 cleaning, HF cleaning, and hydrogen peroxide cleaning, whereby the number of fine particles and uneven haze can be reduced. Further, when the hydrogen peroxide is washed, if the temperature of the hydrogen peroxide is 20 to 80 ° C and the concentration is 0.1 to 30 wt%, the amount of particles after washing can be more effectively reduced, and the burden on the exhaust equipment can be reduced.

On the other hand, in Comparative Example 1, as shown in Figs. 2 and 3, the number of fine particles on the surface of the cleaned wafer was not significantly different from that of the examples. However, as shown in Fig. 4, since the haze unevenness occurs on the surface of the germanium wafer after the ozone water is washed, the quality of the cleaned germanium wafer is inferior.

Further, the present invention is not limited to the above embodiment. The above-described embodiments are exemplified, and those having substantially the same configuration as the technical idea described in the scope of the patent application of the present invention can achieve the same effects and are included in the technical scope of the present invention.

Claims (3)

A method for cleaning a semiconductor wafer, comprising: a first cleaning step of performing SC1 cleaning on the semiconductor wafer; and a second cleaning step, after the first cleaning step, on the semiconductor wafer The HF cleaning is performed; and the third cleaning step, after the second cleaning step, the semiconductor wafer is washed by hydrogen peroxide water. The method of cleaning a semiconductor wafer according to claim 1, wherein the temperature of the hydrogen peroxide water is set to 20 to 80 °C. The method for cleaning a semiconductor wafer according to claim 1 or claim 2, wherein the concentration of the hydrogen peroxide water is 0.1 to 30% by weight.