JP2006054344A - Drying method of silicon wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drying method of a silicon wafer, well finished within a short period of time without taking the silicon wafer out of a wafer carrier and without generating water mark, in the drying of the silicon wafer wetted by water or an organic solvent. <P>SOLUTION: The drying method of the silicon wafer, wetted by water or the organic solvent, comprises a process for spraying water vapor against substantially whole surface of the silicon wafer and another process for spraying nitrogen gas or air against substantially the whole surface of the silicon wafer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for drying a silicon wafer, and more particularly to a method for drying a silicon wafer after wet chemical treatment and cleaning.

  Semiconductor silicon wafers used as substrates for single crystal and polycrystalline crystalline solar cell elements are immersed in various aqueous solutions such as hydrofluoric acid, nitric acid, and sodium hydroxide in the device process, and etching, oxide film removal, etc. Treated, then washed with water and dried.

  Also, for example, in a photolithographic process for forming a thin film such as silicon nitride on the surface of a silicon wafer using a CVD (chemical vapor deposition) apparatus and drawing a fine pattern on the thin film by etching or the like. After etching, the photoresist after etching is finally removed using an organic solvent, and then the organic solvent needs to be dried.

  For example, in the device process of a solar cell element, these dryings are performed by putting about 10 to 50 silicon wafers into a wafer carrier for holding or carrying these silicon wafers, and chemicals for each wafer carrier containing the silicon wafers. After that, several baths were immersed in a bath containing pure water to wash away the chemicals, and then the wafer carrier was set on a rotary rinser dryer, and water droplets were blown off by a rotating centrifugal force and dried.

  With such a rinser dryer, there are only two to four wafer carriers that can be dried at one time, and there is a problem that it takes time to set and dry the wafer carrier because there is an increase and decrease in the number of rotations. It was.

As a countermeasure against such problems, an air knife that takes out a silicon wafer from a wafer carrier that has been subjected to chemical treatment and cleaning, applies high-pressure nitrogen gas or clean air from an oblique direction on the front and back surfaces of the silicon wafer, and blows water droplets away. in use. (Refer to the prior art in Patent Document 1)
Prior art document information related to the invention of this application includes the following.
Japanese Patent Application Laid-Open No. 11-40560

  However, as described above, the silicon wafer is taken out from the wafer carrier that has been treated with chemicals and cleaned, and an air knife is used to apply high-pressure nitrogen gas or clean air from the front and back of the silicon wafer obliquely. In the method of drying, since drying is performed one by one, although it is shorter than drying with a rinser dryer, there is still a problem that it takes time.

  In addition, since the air knife is used, the sprayed water droplets and organic solvent droplets accumulate on the end face of the silicon wafer, and may be dried as it is to leave a stain called a water mark.

  Furthermore, silicon wafers used as substrates for solar cell elements as described above are being made larger and thinner for reasons such as cost reduction and reduction of silicon materials. For this reason, when using an air knife that applies high-pressure nitrogen gas or clean air from the diagonal direction of the front and back surfaces of the silicon wafer, the silicon wafer may bend and vibrate, causing the silicon wafer to crack or crack. May occur.

  In view of the above problems, an object of the present invention is to dry a silicon wafer wet with water or an organic solvent, and to produce a silicon wafer with a good finish in a short time without generating a water mark. Is to provide.

  A method for drying a silicon wafer according to the present invention is a method for drying a silicon wafer wetted with water or an organic solvent, the step of spraying water vapor on substantially the entire surface of the silicon wafer, and the step of spraying nitrogen gas or air on the silicon wafer. And spraying substantially the entire surface.

  In another drying method of the silicon wafer of the present invention, it is desirable that the temperature of nitrogen gas or air sprayed on substantially the entire surface of the silicon wafer is 100 ° C. or higher and 300 ° C. or lower.

  Another method for drying a silicon wafer according to the present invention is a method for drying a silicon wafer wetted with water or an organic solvent, the step of immersing the silicon wafer in water of 70 ° C. or higher, The method includes spraying water vapor on substantially the entire surface and spraying nitrogen gas or air on the substantially entire surface of the silicon wafer.

  Furthermore, it is desirable that the organic solvent contains at least one of methyl alcohol, ethyl alcohol, isopropyl alcohol, and acetone.

  According to the silicon wafer drying method of the present invention, there is provided a method for drying a silicon wafer wetted with water or an organic solvent, the method comprising spraying water vapor on substantially the entire surface of the silicon wafer, and supplying nitrogen gas or air to the silicon wafer. With the step of spraying substantially the entire surface of the wafer, there is no generation of cracks and cracks, the temperature of the silicon wafer can be raised quickly, and no water mark or dry residue is generated. The result is dry. In particular, when the organic solvent is dried, the use of water vapor eliminates the danger of explosion and fire due to drying.

  Further, according to another method of drying a silicon wafer of the present invention, the temperature of nitrogen gas or air sprayed on substantially the entire surface of the silicon wafer is set to 100 ° C. or more and 300 ° C. or less, so that the drying time can be shortened and a water mark or It is possible to ensure a good dry state that does not cause drying residue, and there is no occurrence of cracking or cracking of the silicon wafer due to temperature difference, and the wafer carrier melts, deforms, breaks or deteriorates. There is no.

  According to another silicon wafer drying method of the present invention, there is provided a method for drying a silicon wafer wetted with water or an organic solvent, the step of immersing the silicon wafer in water of 70 ° C. or higher, and the silicon wafer By providing a process of spraying water vapor on substantially the entire surface of the wafer and a process of spraying nitrogen gas or air on the substantially entire surface of the silicon wafer, the drying time can be shortened, and a water mark and residual residue are generated. The good dry state which does not do can be ensured.

  Furthermore, according to another silicon wafer drying method of the present invention, the organic solvent contains at least one of methyl alcohol, ethyl alcohol, isopropyl alcohol, and acetone, so that the affinity for water vapor is improved. Thus, it is possible to ensure a good dry state in which no water mark or dry residue is generated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram showing an example of a drying apparatus using a drying method according to the present invention.

  In FIG. 1, 1 is a silicon wafer, 2 is a wafer carrier, 3 is a spray nozzle, 4 is a flow of water vapor, 5 is a solenoid valve for water vapor, 6 is a flow of clean air or nitrogen gas, and 7 is for clean air or nitrogen gas. An electromagnetic valve, 8 is a side bar of the wafer carrier, and 9 is a pipe.

  The silicon wafer 1 is made of single crystal or polycrystalline silicon as described above, has a thickness of about 0.2 to 0.4 mm, and is often round, square, or rectangular. The size is about 100 to 200 mm in diameter for a circle, and about 100 to 200 mm for one side in a square or rectangle.

  The wafer carrier 2 is constructed so that a plurality of silicon wafers 1 can be stored side by side in an upright state. The material is an acid-resistant resin such as fluororesin or polypropylene when acid or alkali treatment is performed in the pre-drying process, and the temperature is raised to 200 ° C. or higher in the previous process or an organic solvent is used. For example, it is made of metal such as stainless steel.

  Further, the side surface of the wafer carrier 2 used in the drying method according to the present invention is formed by the side bars 8. About 2 to 3 sidebars 8 are attached to one side surface, and V-shaped grooves are formed in a vertical direction at a pitch of about 5 to 10 mm on the inner surface of the wafer carrier. It is stored so as to be inserted into the V-shaped groove. The reason why the silicon wafer 1 is supported by the side bar 8 is that the spray of water vapor, clean air, or nitrogen gas can be easily applied from the side surface.

  The spray nozzle 3 and the pipe 9 are preferably made of stainless steel in consideration of the temperature of water vapor and the generation of rust. Further, the number of spray nozzles 3, the spray pattern, and the arrangement thereof may be determined by testing in consideration of the number of silicon wafers 1 to be dried and the size of the wafer carrier 2.

  The opening and closing of the water vapor solenoid valve 5 and the clean air or nitrogen gas solenoid valve 7 are controlled by a sequencer (not shown). The water vapor electromagnetic valve 5 is connected to a water vapor generator (not shown) such as a boiler, and water vapor flows in the direction indicated by the arrow 4. The electromagnetic valve 7 for clean air or nitrogen gas is connected to a clean air generator or a nitrogen tank including a compressor and a dryer, and clean air or nitrogen gas flows in the direction indicated by the arrow 6.

  The method for drying a silicon wafer wetted with water or an organic solvent according to the present invention is a method for drying a silicon wafer wetted with water or an organic solvent, the method comprising spraying water vapor over substantially the entire surface of the silicon wafer, and nitrogen. Spraying gas or air over substantially the entire surface of the silicon wafer.

  In such an apparatus, the silicon wafer 1 contained in the wafer carrier 2 wet with water or an organic solvent is placed on a net-like belt conveyor or the like and carried to a predetermined position near the spray nozzle 3.

  First, a process of spraying water vapor on substantially the entire surface of the silicon wafer 1 is performed.

  The electromagnetic valve 5 is opened, and water vapor is sprayed from the spray nozzle 3 over substantially the entire surface of the silicon wafer. The substantially entire surface indicates the entire surface excluding a portion where water vapor is difficult to hit, such as a portion where the silicon wafer and the side bar 8 of the wafer carrier 2 are in contact with each other.

  The temperature of the water vapor is optimally 120 ° C. or more and 300 ° C. or less immediately after the spray nozzle 3. When the temperature of the water vapor is lower than 120 ° C., it takes time until the temperature of the silicon wafer 1 rises, and an insufficiently dried portion is generated. When the temperature exceeds 300 ° C., there is a partial temperature difference between the silicon wafer 1 and the wafer carrier 2. As a result, the silicon wafer 1 is warped or cracked, and the wafer carrier 2 is deformed. Further, the resin wafer carrier 2 melts, breaks, or deteriorates.

Further, the pressure of the water vapor is optimally 2 × 10 ⁵ Pa or more and 10 × 10 ⁵ Pa or less immediately before the spray nozzle 3. If the water vapor pressure is less than 2 × 10 ⁵ Pa, the water vapor is not sprayed uniformly, resulting in insufficient drying. If the water vapor pressure is greater than 10 × 10 ⁵ Pa, the silicon wafer 1 is cracked or cracked due to the pressure. It is not preferable because it may occur.

  By spraying water vapor onto the silicon wafer 1 contained in the wafer carrier 2 in this way, the temperature rises while the temperature of the silicon wafer 1 or the wafer carrier 2 remains wet.

  Next, a step of spraying nitrogen gas or air over substantially the entire surface of the silicon wafer 1 is performed.

  The solenoid valve 5 is closed and the solenoid valve 7 is immediately opened to spray clean air or nitrogen gas from the same spray nozzle 3.

  According to the test repeatedly performed by the inventors, the temperature of the silicon wafer is all 90 ° C., when the solenoid valve 5 is closed and the solenoid valve 7 is immediately opened to spray clean air or nitrogen gas from the same spray nozzle 3. This is the best time. This is because if there is a portion of less than 90 ° C., the portion becomes insufficiently dried.

The pressure of clean air or nitrogen gas is optimally 2 × 10 ⁵ Pa or more and 10 × 10 ⁵ Pa or less immediately before the spray nozzle 3. When the pressure of clean air or nitrogen gas is lower than 2 × 10 ⁵ Pa, clean air or nitrogen gas is not sprayed uniformly, and an insufficiently dried portion is generated. When the pressure is higher than 10 × 10 ⁵ Pa, the pressure is increased. Since the silicon wafer 1 may be cracked or cracked, it is not preferable.

  By spraying clean air or nitrogen gas after the water vapor as described above, the water or organic solvent film on the surface of the silicon wafer 1 where the temperature is rising can be quickly and cleanly dried. Water and organic solvent droplets accumulated in the water can also be blown away to achieve a good dry state.

  The temperature of the clean air or nitrogen gas may be room temperature, but is preferably 100 ° C. or higher and 300 ° C. or lower.

  FIG. 2 is a view showing a pipe portion of clean air or nitrogen gas equipped with a heater for raising the temperature of clean air or nitrogen gas.

  In FIG. 2, reference numerals 4, 5, 6, and 7 are the same as in FIG. 1, 4 is the flow of water vapor, 5 is the electromagnetic valve for water vapor, 6 is the flow of clean air or nitrogen gas, and 7 is the electromagnetic wave for clean air or nitrogen gas. Reference numeral 11 denotes a valve. Reference numeral 11 denotes a heater for raising clean air or nitrogen gas.

  The heater 11 has a hot wire inside, and at the same time as the electromagnetic valve 7 is opened, the hot wire inside the heater 11 is energized to raise the temperature of clean air or nitrogen gas. At this time, a temperature sensor such as a thermocouple is arranged near the outlet of a specific spray nozzle, and a temperature controller (not shown) is set so that the temperature of clean air or nitrogen gas to be sprayed is 100 ° C. or more and 300 ° C. or less. ) To control the energization of the heater 11.

  By setting the temperature of the clean air or nitrogen gas to 100 ° C. or more, the water or organic solvent film on the surface of the silicon wafer 1 can be dried more quickly, and the water or organic solvent collected on the lower surface of the silicon wafer can be dried. Since the droplets can be blown off and dried, the drying time can be shortened and a good dry state can be ensured without generating a water mark or residual drying. There is no occurrence of cracks or cracks, and the wafer carrier does not melt, deform, break or deteriorate.

  Further, since the temperature of the clean air or nitrogen gas is set to 300 ° C. or less, a partial temperature difference occurs in the silicon wafer 1 or the wafer carrier 2, and no cracks or cracks occur due to warpage of the silicon wafer 1. Further, when the wafer carrier 2 is deformed due to thermal expansion, and when the resin wafer carrier 2 is used, the wafer carrier 2 is not melted, broken or deteriorated.

  Furthermore, another method for drying a silicon wafer according to the present invention is a method for drying a silicon wafer wetted with water or an organic solvent, the step of immersing the silicon wafer in water at 70 ° C. or higher, and the silicon wafer. A step of spraying water vapor on substantially the entire surface, and a step of spraying substantially the entire surface of the silicon wafer with nitrogen gas or air.

  First, a step of immersing a silicon wafer contained in a wafer carrier wet with water or an organic solvent in water at 70 ° C. or higher is performed.

  In other words, a water tank is prepared that is maintained at 70 ° C. or more and is large enough to immerse all silicon wafers contained in the wafer carrier, and this water is sprayed before the water vapor is sprayed on the silicon wafers contained in the wafer carrier. All the silicon wafers contained in the wafer carrier are immersed in the tank. The immersion time is determined so that the silicon wafer becomes 70 ° C. or higher.

  Thus, by immersing the silicon wafer contained in the wafer carrier in water of 70 ° C. or higher before drying, the temperature of the wafer carrier and the silicon wafer rises, and then the silicon in the state in which the wafer carrier is contained. By performing the step of spraying water vapor on substantially the entire surface of the wafer and the step of spraying nitrogen gas or air on the substantially entire surface of the silicon wafer, the drying time of the silicon wafer can be shortened and the silicon wafer and the wafer can be reduced. The water in the contact portion with the side bar of the carrier can be reliably dried, and a good dry state can be ensured without generating a water mark or dry residue.

  Furthermore, when the silicon wafer contained in the wafer carrier before being dried or immersed in water of 70 ° C. or higher is wet with an organic solvent, the organic solvent is methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone. It is desirable to include at least one of them. In other words, methyl alcohol, ethyl alcohol, isopropyl alcohol, and acetone are easily soluble in water. By containing these, water can be easily mixed with water by spraying with water vapor or immersing in water at 70 ° C. or higher. An inadequate portion does not occur, and a good dry state in which a water mark or dry residue does not occur can be ensured. Further, when the organic solvent used in the process is difficult to mix with water such as toluene or xylene, it is desirable to replace it by immersing it once in methyl alcohol, ethyl alcohol, isopropyl alcohol, or acetone.

  Furthermore, according to the silicon wafer drying method of the present invention, since water vapor is first sprayed, even a flammable organic solvent can be safely dried without worrying about explosion or fire.

  In addition, this invention is not limited to the above-mentioned form, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention. For example, instead of a wafer carrier, other containers or jigs that can set a silicon wafer may be used.

It is a figure which shows an example of the drying apparatus by the drying method which concerns on this invention. It is a figure which shows the piping part of the clean air or nitrogen gas which equipped the heater.

Explanation of symbols

1; silicon wafer 2; wafer carrier 3; spray nozzle 4; water vapor flow 5; water vapor solenoid valve 6; clean air or nitrogen gas flow 7; clean air or nitrogen gas solenoid valve 8; Piping 11; heater for heating up clean air or nitrogen gas

Claims (4)

A method for drying a silicon wafer wetted with water or an organic solvent, comprising: spraying water vapor on substantially the entire surface of the silicon wafer; and spraying nitrogen gas or air on substantially the entire surface of the silicon wafer. A method for drying a silicon wafer. The method for drying a silicon wafer according to claim 1, wherein the temperature of nitrogen gas or air sprayed on substantially the entire surface of the silicon wafer is 100 ° C or higher and 300 ° C or lower. A method for drying a silicon wafer wetted with water or an organic solvent, the step of immersing the silicon wafer in water at 70 ° C. or higher, the step of spraying water vapor on substantially the entire surface of the silicon wafer, and nitrogen gas or air Spraying substantially the entire surface of the silicon wafer. A method for drying a silicon wafer, comprising: 4. The method for drying a silicon wafer according to claim 1, wherein the organic solvent contains at least one of methyl alcohol, ethyl alcohol, isopropyl alcohol, and acetone.

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