JP5726812B2 - Silicon wafer drying method - Google Patents

Description

  The present invention relates to a method for drying a silicon wafer.

  In the manufacturing process of a silicon wafer, the silicon wafer is cleaned as a pre-process or a post-process of each process. In the washing process, washing is performed with various chemical solutions, rinsing with ultrapure water, and drying is performed.

  As a drying method performed here, a silicon wafer is rotated in a state where it is housed in a carrier, and a method of drying by spinning off water using a centrifugal force (spin dry drying), an organic solvent such as isopropyl alcohol (IPA) is used. A method of holding a silicon wafer in the used vapor and replacing the moisture on the surface with an organic solvent for drying (IPA drying or the like). Drying method for sucking moisture from the opening (suction drying), Dipping the silicon wafer in ultrapure water, slowly draining the ultrapure water, and drying using the surface tension of the pure water (pure water) Drying), a method of evaporating and drying pure water on the surface of a silicon wafer using a heat source such as a halogen lamp (IR drying), dipping the silicon wafer in warm pure water and slowly pulling it up to dry Method of (on warm water inlet drying), placed silicon wafer in a closed drying vessel, the vessel was evacuated, method of drying with exclusion of moisture evaporation (vacuum drying), and the like.

Japanese Patent Laid-Open No. 10-50657

  In the silicon wafer drying process, tens of silicon wafers are often dried simultaneously. As described above, there are a plurality of methods for drying a silicon wafer. For example, in spin dry drying, the surface of the silicon wafer is generated by dust generated by contact between the silicon wafer and the carrier during rotary drying or by dust generated from the rotary drive unit. The problem arises in the cleanliness.

  In addition, IPA drying has a problem of safety because the organic solvent to be used is volatile and high cost due to an expensive organic solvent. Pure water drying has a problem in that it takes time because a silicon wafer is immersed in pure water and dried while slowly draining ultrapure water, and productivity is extremely low. Similarly, there is a problem that the productivity is low because the silicon wafer is pulled up from the hot water at a low speed in the hot water drawing. IR drying is problematic in terms of productivity because it can mainly dry silicon wafers one by one. With regard to drying under reduced pressure, there is a problem that heat of vaporization is lost during drying and moisture is condensed on the surface of the silicon wafer.

  The present invention has been made in view of the above problems, and an object thereof is to provide a method for efficiently drying a silicon wafer without deteriorating the quality.

  In order to achieve the above object, the present invention provides a method for drying a silicon wafer, wherein the silicon wafer has an opening and an exhaust port after the silicon wafer is taken out from a cleaning tank filled with pure water. Placed on a mounting table in a quartz drying container, the gas in the drying container is exhausted from the exhaust port, and the drying is performed by a heater installed outside the drying container while exhausting the gas from the opening. In the method of drying the silicon wafer by heating the inside of the container, the gas is exhausted from the exhaust port so that the gas wind speed on the surface of the silicon wafer is 0.2 to 0.5 m / sec. A silicon wafer drying method is provided.

With such a drying method, the silicon wafer can be efficiently dried by heating with a heater and a gas flow by exhaust.
Furthermore, by exhausting the gas from the exhaust port so that the gas wind speed on the surface of the silicon wafer is 0.2 to 0.5 m / sec, dry residue occurs and the amount of exhaust is increased. It is possible to prevent an increase in the cost of the air conditioning equipment.

  As described above, according to the present invention, it is possible to provide a method for efficiently drying a silicon wafer by heating with a heater and a gas flow by exhaust.

It is an example of the washing | cleaning and drying process flow of a silicon wafer. It is a flowchart which shows an example of the drying method of the silicon wafer of this invention, (a) rinses, (b) draws pure water, (c) represents the drying stage. It is the schematic of the warm pure water drying method of the silicon wafer in a comparative example, (a) rinses, (b) draws warm pure water, (c) represents the drying stage.

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

In the cleaning of the silicon wafer, first, as shown in FIG. 1, the silicon wafer is cleaned with ammonia / hydrogen peroxide solution (hereinafter also referred to as excess water). Next, after rinsing the silicon wafer that has been subjected to ammonia / overwater cleaning, hydrochloric acid / overwater cleaning is performed. Thereafter, the silicon wafer that has been subjected to hydrochloric acid / overwater cleaning is rinsed with pure water again.
For example, a silicon wafer cleaned as described above can be dried according to the present invention described below.

  In the present invention, after pure rinsing as shown in FIG. 2 (a), as shown in FIG. 2 (b), the rinsed silicon wafer 1 is used from a cleaning tank 2 filled with pure water using a silicon wafer stand 9. Then, as shown in FIG. 2 (c), it is placed on a mounting table 6 in a quartz drying container 5 having an opening 3 and an exhaust port 4, and dried. In addition, when taking out the silicon wafer 1 from the cleaning tank 2, the silicon wafer 1 may be taken out from the state where the pure water in the cleaning tank 2 overflows, or after the pure water is discharged from the cleaning tank 2, The silicon wafer 1 may be taken out from the cleaning tank 2. Moreover, it is preferable that the pure water in the washing tank 2 is normal temperature.

  In the silicon wafer drying method of the present invention, the gas 7 in the drying container 5 is exhausted from the exhaust port 4 to suck out the gas 7 from the opening 3, and the heater 8 installed outside the drying container 5 is used to dry the container. The silicon wafer 1 is dried by heating the inside. At this time, the gas 7 is exhausted from the exhaust port 4 so that the wind speed of the gas 7 on the surface of the silicon wafer 1 is 0.2 to 0.5 m / sec.

  By drying the silicon wafer taken out of the cleaning tank and wetted entirely with water as described above, the silicon wafer can be efficiently dried by heating with a heater and the flow of gas by exhaust. In the present invention, no organic solvent is used, there is no need for an operating part that causes dust generation, no equipment for reducing the pressure to a vacuum, and no hot pure water production equipment is required, and batch processing of a plurality of silicon wafers. Therefore, it is possible to provide a silicon wafer drying method that is excellent in terms of cleanliness, running cost, safety, and automation without deteriorating productivity.

  At this time, if the gas wind speed on the surface of the silicon wafer is less than 0.2 m / sec, there may be a case where dry residue may occur within a predetermined time. This increases the cost of the air conditioning equipment due to the increase, resulting in waste and deterioration of the particle level. Therefore, in the present invention, the silicon wafer can be dried at a low cost without generating dry residue by exhausting the gas so that the wind velocity of the gas on the surface of the silicon wafer is 0.2 to 0.5 m / sec. It becomes possible. Further, the gas in the drying container to be exhausted and sucked is not particularly limited, but if it is air, the silicon wafer can be dried at a low cost.

  Furthermore, since the exhaust air velocity of the gas is preferably controlled by adjusting the air volume of the exhaust duct connected to the exhaust port, it is desirable to use a blower exclusively for exhausting the drying container in which the silicon wafer is disposed. . In this case, the adjustment of the exhaust wind speed can be performed only by changing the output setting of the blower without affecting other exhaust balances.

  In order to maintain the cleanliness in the drying container, it is preferable that the operation of the blower is always set to a constant exhaust air volume. This is because, for example, if the exhaust blower is operated only during drying, the chamber pressure in the drying container changes in accordance with the operation of the blower, and the cleanliness may not be maintained. It should be noted that it is possible to change the exhaust air volume when the silicon wafer is dried and when it is on standby under the condition that the cleanliness in the drying container can be maintained.

  Further, in FIG. 2C, the drying container 5 has a structure capable of introducing clean gas exhausted through the surface of the silicon wafer 1 into the exhaust port 4 below the mounting table 6 without waste. . Therefore, it is preferable that the opening 3 has a minimum opening area and the airflow is not disturbed. Further, since the silicon wafer 1 in the drying container 5 is heated by the heater 8 installed outside the drying container 5, the drying container 5 is made of quartz having heat resistance. Furthermore, the size of the drying container 5 is preferably such that the entire surface of the silicon wafer 1 can be positioned in the drying container 5 in order to efficiently dry the silicon wafer 1 with the exhausted gas.

  Further, in the present invention, in FIG. 2 (c), the silicon wafer 1 is arranged in the vertical direction in the groove portion of the mounting table 6, but can be similarly dried even when arranged horizontally (single-wafer type). it can.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
Example 1
First, a clean silicon single crystal silicon wafer having a mirror finished on both sides with a diameter of 300 mm was prepared. This silicon wafer was washed with ammonia / hydrogen peroxide solution as shown in FIG. 1, then rinsed with pure water, washed with hydrochloric acid / overwater, rinsed with pure water, and finally dried.

  At this time, as shown in Table 1, the cleaning conditions are as follows: chemical composition (mixing ratio) of ammonia / overwater cleaning is ammonia: overwater: pure water = 1: 1: 10, cleaning solution temperature is 80 ° C., hydrochloric acid / overwater The chemical composition (mixing ratio) of the water cleaning was hydrochloric acid: overwater: pure water = 1: 1: 10, the cleaning liquid temperature was 80 ° C., and the cleaning time with each cleaning liquid was 5 min.

  In the process 4 of FIG. 1, after performing the pure water rinse as shown in FIG. 2 (a), as shown in FIG. 2 (b), the movable silicon wafer stand 9 attached to the cleaning tank 2 is The silicon wafer 1 is taken out from the pure water at room temperature by increasing at a speed of 5 mm / sec. Subsequently, as shown in FIG. 2 (c), the silicon wafer 1 is placed on the mounting table 6 and heated by the heater 8. Meanwhile, drying was performed while exhausting with a blower. At this time, the exhaust air velocity on the surface of the silicon wafer 1 was 0.2 m / sec. As the heater 8, two 1.2KW medium wavelength infrared heaters having a wavelength of 2 to 3.5 microns were used. In addition, since the chemical | medical agent is not contained in the exhausted air, it was also possible to return to the clean room in which the drying container 5 was arrange | positioned.

(Example 2)
The silicon wafer was cleaned and dried in the same manner as in Example 1 except that the exhaust air velocity on the surface of the silicon wafer was 0.4 m / sec.

(Example 3)
The silicon wafer was cleaned and dried in the same manner as in Example 1 except that the exhaust air velocity on the silicon wafer surface was set to 0.5 m / sec.

(Comparative Example 1)
As in Example 1, ammonia / overwater cleaning, pure water rinsing, hydrochloric acid / overwater cleaning, and pure water rinsing were performed in succession, and after the pure water rinsing shown in FIG. 3 (a), it is shown in FIG. 3 (b). As described above, warm pure water drying was performed. In the hot pure water drying, the temperature of the pure water in the cleaning tank 12 was 50 ° C., the flow rate was 5 L / min, and the ascending speed of the movable silicon wafer stand 19 attached to the cleaning tank 12 was 2 mm / sec. After that, as shown in FIG. 3C, the silicon wafer 11 was placed on the drying stage 16 and the silicon wafer 11 was dried using the residual heat from the warm pure water drying.

(Comparative Example 2)
The silicon wafer was cleaned and dried in the same manner as in Example 1 except that the exhaust air velocity on the surface of the silicon wafer was 0.1 m / sec.

(Comparative Example 3)
The silicon wafer was cleaned and dried in the same manner as in Example 1 except that the exhaust air velocity on the surface of the silicon wafer was 0.8 m / sec.

  Hereinafter, the particle level (average value) of the silicon wafer after drying in Examples and Comparative Examples and the results of the remaining drying are summarized in Table 2.

  As shown in Table 2, in Comparative Example 1, no dry residue was generated, but the particle level was slightly poor, and the productivity was poor because it took a long time for the hot pure water drying and the subsequent drying. Moreover, in Comparative Example 2, since the exhaust speed on the surface of the silicon wafer was small, dry residue occurred. Furthermore, in Comparative Example 3, since the exhaust speed of the silicon wafer surface was large, the cost of space equipment was increased, and the particle level was also poor.

  On the other hand, in Examples 1 to 3, the silicon wafer could be dried with high productivity, and the particle level was not deteriorated and the dry residue did not occur.

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

  DESCRIPTION OF SYMBOLS 1,11 ... Silicon wafer, 2,12 ... Cleaning tank, 3 ... Opening part, 4 ... Exhaust port, 5 ... Drying container, 6,16 ... Mounting stand, 7 ... Gas, 8 ... Heater, 9, 19 ... Silicon wafer stand.

Claims (1)

A silicon wafer drying method comprising:
After the silicon wafer is taken out of the cleaning tank filled with pure water, the silicon wafer is placed on a mounting table in a quartz drying container having an opening and an exhaust port, and the exhaust port is placed in the drying container. In the method of drying the silicon wafer by heating the inside of the drying container with a heater installed outside the drying container while sucking the gas from the opening by exhausting the gas with a blower A method for drying a silicon wafer, characterized in that the gas is exhausted from the exhaust port by the blower so that an air velocity of the gas on the wafer surface is 0.2 to 0.5 m / sec.

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