JP6206173B2 - Semiconductor wafer cleaning method - Google Patents

Description

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

  A cleaning solution (SC1 cleaning solution) composed of a mixed solution of ammonia water, hydrogen peroxide solution, and pure water is used as a cleaning solution for the most common semiconductor silicon wafer cleaning method. As an example of a general cleaning flow when this SC1 cleaning liquid is used, cleaning with SC1 cleaning liquid (SC1 cleaning) → rinsing with pure water → SC2 cleaning liquid composed of a mixed liquid of hydrochloric acid, hydrogen peroxide, and pure water Cleaning (SC2 cleaning) → rinsing with pure water → drying. In this cleaning method, particles attached to the semiconductor wafer are removed with the SC1 cleaning solution, and the chemicals are washed away with pure water rinse. Next, metal impurities are removed with an SC2 cleaning solution, and the chemicals are washed away again with pure water rinse, followed by drying (see Patent Document 1).

  The SC1 cleaning liquid is often used after being heated from 60 ° C. to 80 ° C. in order to enhance the cleaning effect. For this reason, a circulating filtration device is attached to the chemical tank, and the temperature of the cleaning liquid is adjusted by a heater at the same time as the removal of particles. Further, in order to prevent the concentration of the cleaning liquid from decreasing due to the evaporation of the chemical, the chemical liquid can be added to control the concentration to be constant. Furthermore, ultrasonic cleaning may be used in combination in order to improve the particle removal power.

  Since the cleaning liquid used here directly affects the cleanliness quality of the semiconductor wafer, the concentration of particles and metal impurities in the cleaning liquid is strictly controlled. Furthermore, since the chemicals used here also directly affect the cleanliness quality of the wafer, high quality chemicals with extremely few particles and impurities are used.

JP 2007-533123 A

  As described above, the SC1 cleaning solution used for cleaning the semiconductor wafer is mainly used for particle removal. This is because particles on the surface of the semiconductor wafer can be removed using the etching action of aqueous ammonia that is alkali. However, the SC1 cleaning can efficiently remove particles, but also etches the surface of the semiconductor wafer, thereby deteriorating the surface roughness of the semiconductor wafer to be cleaned.

  In this SC1 cleaning, it is considered that an etching reaction with ammonia water and an oxidation reaction of the silicon wafer surface with hydrogen peroxide water proceed simultaneously. For this reason, the surface state of the semiconductor wafer before SC1 cleaning affects the surface state of the semiconductor wafer after SC1 cleaning. That is, when there is no protective film on the surface of the semiconductor wafer, the etching with ammonia water precedes and the roughness of the surface of the semiconductor wafer increases.

On the other hand, the deterioration of the surface roughness of the semiconductor wafer can be suppressed by forming an oxide film as a protective film on the surface of the semiconductor wafer before SC1 cleaning.
However, when an oxide film is formed as a protective film on the surface of a semiconductor wafer, ozone water is generally used, so devices such as an ozone water treatment tank, an ozone water generator and an ozone water decomposition device are required. There has been a problem that the cost is greatly increased.

  The present invention has been made in view of the above-described problems, and can suppress the deterioration of the surface roughness of the semiconductor wafer when performing SC1 cleaning. It is an object of the present invention to provide a method for cleaning a semiconductor wafer that can achieve the same surface roughness as when an oxide film is formed on the surface without forming an oxide film as a protective film.

  In order to achieve the above object, according to the present invention, there is provided a semiconductor wafer cleaning method for cleaning a semiconductor wafer with a cleaning liquid comprising a mixed liquid of ammonia water, hydrogen peroxide water, and pure water, wherein the semiconductor wafer comprises: Provided is a method for cleaning a semiconductor wafer, wherein the cleaning is performed twice or more with the cleaning liquid, and the etching rate of the surface of the semiconductor wafer by the second and subsequent cleaning is set to 5 times or more with respect to the first cleaning.

  In this way, in the SC1 cleaning of the semiconductor wafer, it is possible to suppress the deterioration of the surface roughness after the cleaning, and even when the semiconductor wafer in which the oxide film is not formed on the surface is cleaned. The surface roughness can be the same as when an oxide film is formed on the surface. This eliminates the need to oxidize the surface of the semiconductor wafer, which was necessary in the past, eliminates the introduction cost and running cost of the oxidizer, and can greatly reduce the cleaning cost of the semiconductor wafer. .

At this time, it is preferable that the etching rate of the surface of the semiconductor wafer by the second and subsequent cleanings is 1 nm / min or less.
In this way, in the SC1 cleaning, the deterioration of the surface roughness after the cleaning can be surely suppressed, and even when the semiconductor wafer having no oxide film formed on the surface is cleaned. Later deterioration of the surface roughness can be more reliably suppressed.

At this time, the concentration of ammonia water, hydrogen peroxide water, and pure water in the cleaning liquid is within a range of 1: 1: 5 to 1: 1: 100 by volume mixing ratio, and the temperature of the cleaning liquid is It can be 60 degrees C or less.
In this way, if the volume mixing ratio of ammonia water, hydrogen peroxide water, and pure water is set to a concentration of 1: 1: 5 or less, the amount of ammonia water and hydrogen peroxide water used does not increase excessively, resulting in high costs. There will be no. Further, when the volume mixing ratio is 1: 1: 100 or more, the semiconductor wafer can be reliably cleaned without lack of cleaning power. Furthermore, if the temperature of the cleaning liquid is set to 60 ° C. or less at this time, the deterioration of the surface roughness after cleaning can be more reliably suppressed.

At this time, the semiconductor wafer can be a silicon wafer on which no oxide film is formed.
According to the cleaning method of the present invention, deterioration of surface roughness due to SC1 cleaning can be suppressed even for a silicon wafer in which an oxide film is not formed on a surface that has not been oxidized. Therefore, the treatment for oxidizing the surface of the silicon wafer, which has been necessary conventionally, becomes unnecessary, the introduction cost of the oxidizer and the running cost become unnecessary, and the manufacturing cost of the semiconductor wafer can be greatly reduced.

At this time, using a circulating filtration device that circulates the cleaning liquid and performs filtration and constant temperature heating, the cleaning liquid is subjected to circulation filtration and temperature control, and at the same time, each concentration of ammonia and hydrogen peroxide in the cleaning liquid is kept constant. It is possible to wash while being controlled.
In this way, particles in the cleaning liquid can be removed by filtration, and cleaning with a higher degree of cleanliness can be performed. Further, the etching rate can be easily controlled by controlling the temperature and concentration of the cleaning liquid.

At this time, the cleaning can be performed after polishing the semiconductor wafer.
Thus, even if the surface is activated by polishing and the surface of the semiconductor wafer has no oxide film as a protective film, deterioration of the surface roughness can be suppressed by the cleaning method of the present invention.

  The semiconductor wafer cleaning method of the present invention can suppress the deterioration of the surface roughness after cleaning in the SC1 cleaning of the semiconductor wafer, particularly when cleaning a semiconductor wafer having no oxide film on the surface. However, the surface roughness equivalent to that obtained when an oxide film is formed on the surface can be obtained. This eliminates the need for a process for forming an oxide film on the surface of a semiconductor wafer, which was necessary in the past, eliminates the need for introducing an oxide film forming apparatus and running cost, and greatly reduces the manufacturing cost of a semiconductor wafer. It becomes possible.

It is a flowchart which shows an example of the cleaning method of the semiconductor wafer of this invention. It is a flowchart which shows an example in the case of wash | cleaning the semiconductor wafer after grinding | polishing with the washing | cleaning method of the semiconductor wafer of this invention. It is the figure which showed the result of the Example and the comparative example.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
As described above, in the SC1 cleaning, the surface roughness of the semiconductor wafer after cleaning deteriorates, and particularly when the semiconductor wafer does not have a protective film such as an oxide film, the surface roughness of the semiconductor wafer after cleaning significantly deteriorates. There was a problem that. In addition, in order to suppress the deterioration of the surface roughness, it is necessary to introduce an oxide film forming device to form an oxide film, which introduces a running cost and a running cost. I was doing it.

  Therefore, the present inventors have made extensive studies to solve such problems. As a result, a semiconductor wafer having no protective film such as an oxide film can be obtained by cleaning it twice or more with the SC1 cleaning solution and increasing the etching rate of the semiconductor wafer surface by the second and subsequent cleanings to 5 times or more with respect to the first cleaning. Even in the case of cleaning, the inventors have conceived that deterioration of the surface roughness after cleaning can be suppressed, and the present invention has been completed.

  Hereinafter, the semiconductor wafer cleaning method of the present invention will be described with reference to FIGS. In the embodiment described below, as shown in FIGS. 1 and 2, in the cleaning step in which the polished semiconductor wafer is rinsed with pure water, then SC1 cleaning is performed, and then SC2 cleaning is performed and dried. An example in which the semiconductor wafer cleaning method of the present invention is applied to cleaning will be described.

As shown in FIG. 2, first, a semiconductor wafer to be cleaned is prepared. And after grind | polishing a semiconductor wafer, washing | cleaning can be implemented with the washing | cleaning method of the semiconductor wafer of this invention.
Even when a semiconductor wafer having a surface activated without forming a protective film such as an oxide film immediately after the polishing step is subjected to SC1 cleaning, the cleaning method of the present invention forms a protective film. Deterioration of the surface roughness can be suppressed to the same extent as in the case of the above.

As shown in FIG. 1, the semiconductor wafer is first rinsed with pure water after polishing, but this step may be omitted.
Subsequently, the first SC1 cleaning is performed. The cleaning liquid used at this time is an SC1 cleaning liquid composed of a mixed liquid of ammonia water, hydrogen peroxide water and pure water. For cleaning, for example, the semiconductor wafer can be cleaned by immersing the semiconductor wafer to be cleaned in a cleaning tank filled with the SC1 cleaning solution. At this time, it is preferable that the SC1 cleaning solution is set to a temperature within a range from 40 ° C. to 60 ° C. for cleaning. This is because in the first cleaning, it is easier to suppress the surface roughness when the etching rate is lowered.

  Next, the second SC1 cleaning is performed. For this cleaning, an SC1 cleaning liquid composed of a mixture of ammonia water, hydrogen peroxide water and pure water is used. For example, a semiconductor wafer to be cleaned is immersed in a cleaning tank filled with the SC1 cleaning liquid. Can be washed. In the present invention, at the second and subsequent cleanings, the etching rate of the semiconductor wafer surface by the second and subsequent SC1 cleanings is set to 5 times or more of the etching rate of the semiconductor wafer surface by the second and subsequent SC1 cleanings. .

  In order to make the etching rate of the second and subsequent SC1 cleanings 5 times or more higher than the etching rate in the first SC1 cleaning, the volume mixing ratio and temperature of the SC1 cleaning liquid in each SC1 cleaning are adjusted. do it.

  For example, in the first SC1 cleaning, the etching rate is 0.05 nm / min by setting the volume mixing ratio of ammonia water, hydrogen peroxide water, and pure water to 0.1: 1: 10 and the temperature to 50 ° C. It can be. In the second SC1 cleaning, the volumetric mixing ratio of ammonia water, hydrogen peroxide water, and pure water is 1: 1: 10, and the temperature is 60 ° C., so that the etching rate is 0.30 nm / min. In addition, the etching rate of the semiconductor wafer in the second SC1 cleaning can be increased six times with respect to the first SC1 cleaning. Thereby, for example, when the cleaning time in each SC1 cleaning is set to 5 minutes, the etching amount becomes 0.25 nm in the first cleaning and 1.5 nm in the second cleaning, and the second etching with respect to the first cleaning. The etching amount of the semiconductor wafer is also increased six times.

  As described above, if the etching rate of the second and subsequent SC1 cleanings is five times or more than the etching rate of the first SC1 cleaning, the deterioration of the surface roughness of the semiconductor wafer after the cleaning is suppressed. can do. In particular, even when a semiconductor wafer having no oxide film formed on the surface is cleaned, the surface roughness can be equivalent to that obtained when an oxide film is formed on the surface. The etching rate is preferably up to 20 times, and more preferably up to 10 times, by adjusting the temperature and composition of the chemical solution.

  The concentration of the SC1 cleaning solution is generally a volume mixing ratio of ammonia water, hydrogen peroxide water, and pure water, but this range is within a range from 1: 1: 5 to 1: 1: 100. It is preferable to do. If the volume mixing ratio is set to a concentration of 1: 1: 5 or less, the amount of aqueous ammonia and hydrogen peroxide used will not be excessive, and the cost will not increase. Further, if the volume mixing ratio is 1: 1: 100 or more, the semiconductor wafer can be reliably cleaned without insufficient cleaning power. Furthermore, if the temperature of the cleaning liquid is set to 60 ° C. or less at this time, the deterioration of the surface roughness after cleaning can be more reliably suppressed.

Moreover, in this invention, it is preferable to make the etching rate of the semiconductor wafer surface by the cleaning after the 2nd time into 1 nm / min or less.
In this way, the etching rate does not become too high, and even in the case of cleaning the semiconductor wafer on which the surface oxide film is not formed in the SC1 cleaning, the deterioration of the surface roughness after cleaning is more reliably performed. Can be suppressed.

  Then, in the first and second and subsequent SC1 cleanings, the SC1 cleaning solution is circulated and filtered using a circulating filtration device that circulates the SC1 cleaning solution and performs constant temperature heating. At the same time, ammonia in the SC1 cleaning solution is used. And it can wash | clean, controlling each density | concentration of hydrogen peroxide uniformly.

  For example, the SC1 cleaning liquid can be circulated by, for example, a pump, the particles in the cleaning liquid can be removed by a filter made of Teflon (registered trademark), and the circulating filtration device can be temperature-controlled by a heater. Further, in order to control the concentration to be constant, ammonia water and hydrogen peroxide solution can be added to compensate for the decrease in the concentration of the cleaning liquid due to evaporation of ammonia and hydrogen peroxide.

  In this way, particles in the cleaning liquid can be removed by filtration, and cleaning with a higher degree of cleanliness can be performed. Further, the etching rate can be easily controlled by controlling the temperature and concentration of the cleaning liquid.

In the cleaning method of the present invention, the semiconductor wafer to be cleaned can be a silicon wafer on which no oxide film is formed.
Thus, even a silicon wafer having no oxide film formed thereon can suppress the deterioration of surface roughness to the same extent as when the oxide film is formed by the cleaning method of the present invention.

As described above, the processing after the SC1 cleaning is completed is not particularly limited. For example, the semiconductor wafer is rinsed with pure water.
Next, SC2 cleaning is performed, and then the semiconductor wafer is rinsed with pure water. Finally, the semiconductor wafer is dried to complete the cleaning process.

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

Example 1
In the cleaning step as shown in FIG. 1, a silicon single crystal wafer on which both surfaces having a diameter of 300 mm were finished by mirror polishing and having no oxide film formed thereon was cleaned.
The cleaning conditions of the first SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 0.1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 50 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was set to 0.05 nm / min. The cleaning time was 240 seconds. Therefore, the etching amount in the first SC1 cleaning was 0.20 nm.

  The cleaning conditions for the second SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 60 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was set to 0.30 nm / min. The cleaning time was 240 seconds. Therefore, the etching amount in the second SC1 cleaning was 1.2 nm.

  By setting such cleaning conditions, the etching rate (etching rate ratio) of the silicon single crystal wafer surface by the second SC1 cleaning with respect to the first SC1 cleaning was set to 6 times.

  The concentration of the SC2 cleaning liquid composed of a mixed liquid of hydrochloric acid, hydrogen peroxide water and pure water is, as a volume mixing ratio, hydrochloric acid: peroxide perhydrophobic: pure water = 1: 1: 100, and the temperature is 80 ° C. did. Moreover, the temperature control with a heater was performed using the circulation filtration apparatus similarly to SC1 washing | cleaning. The cleaning time for SC2 cleaning was 240 seconds.

  After the silicon single crystal wafer was dried, surface inspection of the silicon single crystal wafer was performed. The surface inspection was performed with a wafer surface defect inspection apparatus SP2 manufactured by KLA-Tencor, and the value of Haze serving as an index indicating the surface roughness of the wafer was measured.

  Further, at this time, in the cleaning process as shown in FIG. 1, cleaning with ozone water is performed instead of the pure water rinsing performed first, and after the double-sided mirror polishing, the silicon single crystal wafer having a natural oxide film formed on the surface is obtained. Washing was also performed. The processes after cleaning with ozone water were the same as the above-described cleaning process and cleaning conditions. Then, the value of Haze was measured in the same manner as described above.

(Example 2)
In the same cleaning process as in Example 1, a silicon single crystal wafer without an oxide film was cleaned.
However, the cleaning conditions of the first SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. In addition, the temperature of the SC1 cleaning solution was set to 40 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was set to 0.06 nm / min. The cleaning time was 240 seconds. Therefore, the etching amount in the first SC1 cleaning was 0.24 nm.

  The cleaning conditions for the second SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 60 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was set to 0.30 nm / min. The cleaning time was 240 seconds. Therefore, the etching amount in the second SC1 cleaning was 1.20 nm.

By setting it as such cleaning conditions, the etching rate (etching rate ratio) of the silicon single crystal wafer surface by the second SC1 cleaning with respect to the first SC1 cleaning was set to 5 times.
The other washing steps and washing conditions were the same as in Example 1, and the value of Haze was measured by the same method as in Example 1.

  Further, at this time, in the cleaning process as shown in FIG. 1, the cleaning of the silicon single crystal wafer in which the cleaning with ozone water is performed instead of the pure water rinsing performed first and the natural oxide film is formed on the polished surface is also performed. went. The processes after cleaning with ozone water were the same as the above-described cleaning process and cleaning conditions. Then, the value of Haze was measured in the same manner as described above.

(Example 3)
In the same cleaning process as in Example 1, a silicon single crystal wafer without an oxide film was cleaned.
However, the cleaning conditions of the first SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 0.1: 2: 10. Further, the temperature of the SC1 cleaning solution was set to 50 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was set to 0.03 nm / min. The cleaning time was 240 seconds. Therefore, the etching amount in the first SC1 cleaning was 0.12 nm.

  The cleaning conditions for the second SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 60 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was set to 0.30 nm / min. The cleaning time was 240 seconds. Therefore, the etching amount in the first SC1 cleaning was 1.20 nm.

By adopting such cleaning conditions, the etching rate (etching rate ratio) of the silicon single crystal wafer surface by the second SC1 cleaning with respect to the first SC1 cleaning was set to 10 times.
The other washing steps and washing conditions were the same as in Example 1, and the value of Haze was measured by the same method as in Example 1.

  Further, at this time, in the cleaning process as shown in FIG. 1, the cleaning of the silicon single crystal wafer in which the cleaning with ozone water is performed instead of the pure water rinsing performed first and the natural oxide film is formed on the polished surface is also performed. went. The processes after cleaning with ozone water were the same as the above-described cleaning process and cleaning conditions. Then, the value of Haze was measured in the same manner as described above.

(Comparative Example 1)
In the same cleaning process as in Example 1, a silicon single crystal wafer without an oxide film was cleaned.
However, the cleaning conditions of the first SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 60 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was set to 0.30 nm / min. The cleaning time was 40 seconds. Therefore, the etching amount in the first SC1 cleaning was 0.20 nm.

  The cleaning conditions for the second SC1 cleaning were the same as the cleaning conditions for the first SC1 cleaning, with the concentration being a volumetric mixture ratio of 1: 1: 10 with ammonia water: peroxide hydrophobe: pure water, The temperature was set to 60 ° C., and the temperature was adjusted with a heater using a circulating filtration device. In this way, the etching rate was 0.30 nm / min as in the first SC1 cleaning. The cleaning time was 240 seconds. Therefore, the etching amount in the second SC1 cleaning was 1.20 nm. In this manner, the total etching amount by the first and second SC1 cleanings was set to 1.40 nm, which is the same etching amount as in Example 1.

And by setting it as such washing | cleaning conditions, the etching rate (etching rate ratio) of the silicon wafer surface by the 2nd SC1 washing | cleaning with respect to the 1st SC1 washing | cleaning was set to 1 time.
The other washing steps and washing conditions were the same as in Example 1, and the value of Haze was measured by the same method as in Example 1.

  Further, at this time, in the cleaning process as shown in FIG. 1, the cleaning of the silicon single crystal wafer in which the cleaning with ozone water is performed instead of the pure water rinsing performed first and the natural oxide film is formed on the polished surface is also performed. went. The processes after cleaning with ozone water were the same as the above-described cleaning process and cleaning conditions. Then, the value of Haze was measured in the same manner as described above.

(Comparative Example 2)
In the same cleaning process as in Example 1, a silicon single crystal wafer without an oxide film was cleaned.
However, the cleaning conditions of the first SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 55 ° C., and the temperature was adjusted with a heater using a circulating filtration device. At this time, the etching rate was 0.20 nm / min. The cleaning time was 72 seconds. Therefore, the etching amount in the first SC1 cleaning was 0.24 nm.

  The cleaning conditions for the second SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 70 ° C., and the temperature was adjusted with a heater using a circulating filtration device. At this time, the etching rate was 0.60 nm / min. The cleaning time was 120 seconds. Therefore, the etching amount in the second SC1 cleaning was 1.20 nm.

By setting such cleaning conditions, the etching rate (etching rate ratio) of the silicon single crystal wafer surface by the second SC1 cleaning with respect to the first SC1 cleaning was set to 3 times.
The other washing steps and washing conditions were the same as in Example 1, and the value of Haze was measured by the same method as in Example 1.

  Further, at this time, in the cleaning process as shown in FIG. 1, the cleaning of the silicon single crystal wafer in which the cleaning with ozone water is performed instead of the pure water rinsing performed first and the natural oxide film is formed on the polished surface is also performed. went. The processes after cleaning with ozone water were the same as the above-described cleaning process and cleaning conditions. Then, the value of Haze was measured in the same manner as described above.

(Comparative Example 3)
In the same cleaning process as in Example 1, a silicon single crystal wafer without an oxide film was cleaned.
However, the cleaning conditions of the first SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 50 ° C., and the temperature was adjusted with a heater using a circulating filtration device. At this time, the etching rate was 0.15 nm / min. The cleaning time was 168 seconds. Therefore, the etching amount in the first SC1 cleaning was 0.42 nm.

  The cleaning conditions for the second SC1 cleaning were such that the concentration of the SC1 cleaning liquid was a volume mixing ratio, and ammonia water: peroxyperoxide hydrophobic: pure water = 1: 1: 10. Further, the temperature of the SC1 cleaning solution was set to 70 ° C., and the temperature was adjusted with a heater using a circulating filtration device. At this time, the etching rate was 0.60 nm / min. The cleaning time was 90 seconds. Therefore, the etching amount in the second SC1 cleaning was 0.90 nm.

By setting such cleaning conditions, the etching rate (etching rate ratio) of the silicon wafer surface by the second SC1 cleaning with respect to the first SC1 cleaning was set to 4 times.
The other washing steps and washing conditions were the same as in Example 1, and the value of Haze was measured by the same method as in Example 1.

  Further, at this time, in the cleaning process as shown in FIG. 1, the cleaning of the silicon single crystal wafer in which the cleaning with ozone water is performed instead of the pure water rinsing performed first and the natural oxide film is formed on the polished surface is also performed. went. The processes after cleaning with ozone water were the same as the above-described cleaning process and cleaning conditions. Then, the value of Haze was measured in the same manner as described above.

  Table 1 summarizes the cleaning conditions in Example 1-3 and Comparative Example 1-3.

  Table 2 summarizes the implementation results in Example 1-3 and Comparative Example 1-3.

As shown in Table 2 and FIG. 3, in Example 1-3, the values of Haze when cleaning a silicon single crystal wafer on which no oxide film is formed are 80 ppb, 82 ppb, 81 ppb, and oxide films in the DWO mode, respectively. The values of Haze when the formed silicon single crystal wafer was washed were 79 ppb, 80 ppb, and 80 ppb, and the values of Haze were similar.
From the above results, the cleaning method of the present invention can suppress the surface roughness after cleaning, and even when a silicon single crystal wafer on which an oxide film is not formed is specifically cleaned, a silicon single film on which an oxide film is formed The Haze value was the same as that obtained when the crystal wafer was cleaned, and it was confirmed that the deterioration of the surface roughness after cleaning was suppressed without forming an oxide film.

  In contrast, in Comparative Example 1-3, the Haze values when cleaning a silicon single crystal wafer on which no oxide film is formed are 91 ppb, 92 ppb, and 90 ppb, respectively, and the silicon single crystal wafer on which an oxide film is formed is cleaned. In this case, the values of Haze were 82 ppb, 82 ppb, and 80 ppb, and the surface roughness was large when a silicon single crystal wafer on which no oxide film was formed was washed.

  From the above results, according to the present invention, even when a silicon single crystal wafer in which an oxide film is not formed as a protective film is cleaned, a Haze value equivalent to that in the case of cleaning a silicon single crystal wafer on which an oxide film is formed is obtained. Thus, it was confirmed that the surface roughness after washing can be improved.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Claims (6)

A semiconductor wafer cleaning method for cleaning a semiconductor wafer with a cleaning liquid composed of a mixed solution of ammonia water, hydrogen peroxide water, and pure water,
The semiconductor wafer is a silicon wafer,
A method of cleaning a semiconductor wafer, wherein the semiconductor wafer is cleaned twice or more with the cleaning solution, and the etching rate of the semiconductor wafer surface by the second and subsequent cleanings is set to 5 times or more with respect to the first cleaning.   The semiconductor wafer cleaning method according to claim 1, wherein an etching rate of the semiconductor wafer surface by the second and subsequent cleanings is set to 1 nm / min or less.   The concentration of ammonia water, hydrogen peroxide water and pure water in the cleaning liquid used for the first cleaning and the cleaning liquid used for the second and subsequent cleanings from 1: 1: 5 to 1: 1: 100 by volume mixing ratio. The temperature of the cleaning liquid used for the first cleaning and the cleaning liquid used for the second and subsequent cleanings is set to 60 ° C. or lower. Cleaning method.   The method for cleaning a semiconductor wafer according to any one of claims 1 to 3, wherein the semiconductor wafer is a silicon wafer having no oxide film formed on a surface thereof.   Using a circulating filtration device that circulates the cleaning liquid and performs filtration and constant temperature heating, the cleaning liquid is subjected to circulation filtration and temperature control, and at the same time, the respective concentrations of ammonia and hydrogen peroxide in the cleaning liquid are controlled to be constant. The semiconductor wafer cleaning method according to claim 1, wherein the semiconductor wafer is cleaned.   The method for cleaning a semiconductor wafer according to claim 1, wherein the cleaning is performed after the semiconductor wafer is polished.

Images