JP2005053730A - Quartz glass surface treatment method and quartz glass jig - Google Patents

Abstract

【Task】
The surface treatment solution is generally used as an etching solution for quartz glass. Therefore, it is possible to form fine irregularities on the surface of quartz glass using hydrofluoric acid that has a low environmental impact and does not require excessive wastewater treatment equipment. A surface treatment method for quartz glass and a quartz glass jig in which fine irregularities without microcracks are formed on the surface are provided.
[Solution]
A hydrofluoric acid fine particle (hereinafter sometimes referred to as a hydrofluoric acid mist or simply a mist) composed of 10% to 75% hydrofluoric acid and having a maximum particle size of 300 μm or less and an average particle size of 3 μm to 50 μm. Was adhered to the surface of the quartz glass, and the quartz glass was etched only in the portion of the quartz glass where the hydrofluoric acid fine particles were adhered, so that fine irregularities were formed on the surface of the quartz glass.
[Selection] Figure 1

Description

  The present invention relates to a surface treatment method for forming fine irregularities on the surface of quartz glass, particularly on the surface of a quartz glass jig for manufacturing semiconductors, and a quartz glass jig treated by the method.

  Quartz glass containers and jigs are widely used in semiconductor processes because they have a small chemical interaction with a silicon wafer and are also thermally stable. In the heat treatment jig for semiconductor manufacturing made of quartz glass, for example, in the process of forming a polysilicon film by the LPCVD method or the plasma CVD method, the deposition of the polysilicon film also occurs on the surface of the quartz glass jig. There arises a problem that it peels off during the heat treatment to contaminate the atmosphere, or adheres to the wafer and causes a defect. Further, in the semiconductor heat treatment, there is a problem that infrared radiation propagates through a quartz glass core tube or a boat holder to deteriorate the seal portion at the end or the organic material for connection.

  In order to avoid the above-mentioned problems, it is common to form fine irregularities on the surface of the quartz glass jig, so as to form a so-called rubbing glass to prevent the exfoliation of the deposit or to scatter the propagation of infrared rays. Has been done.

  This surface treatment method of quartz glass is generally performed by a method of spraying quartz or ceramic powder onto the surface of the quartz glass called the sand blast method, but in such a method of physically roughening the surface of the quartz glass, A layer with microcracks is formed under the uneven surface, and sometimes the depth can reach as much as 100 μm. Substances that contaminate the silicon wafer can be taken into the cracks, or the cracks can break down. It may progress and cause product strength degradation.

  In order to avoid such problems, the surface of the quartz glass is finely etched on the surface of the quartz glass by non-uniform etching using a special chemical mixed with hydrogen fluoride, ammonium fluoride and an organic acid such as acetic acid. A surface treatment method for forming irregularities has been proposed (see Patent Documents 1 to 3).

  Since the unevenness formed by the chemical treatment method is not accompanied by microcracks at all, it can maintain a clean surface state without taking in contaminants, and does not deteriorate the strength of the product.

However, since this method uses a chemical solution containing an organic acid such as acetic acid in addition to hydrofluoric acid, there is a problem in that it is difficult to drain the cleaning water obtained by washing the treatment chemical solution or the treated product. Especially when organic acid is included in the waste liquid, the BOD and COD of the factory wastewater is greatly increased compared to the case of using only hydrofluoric acid, so a large-scale comprehensive drainage facility is required to meet this environmental standard. become. As a result, the processing cost becomes high and the environmental load is very large.
JP-A-7-267679 Japanese Patent Laid-Open No. 2001-240429 JP 2001-335342 A

  The present invention is a quartz glass surface that can avoid the problem of waste liquid treatment due to containing an organic acid in the treatment liquid while maintaining the advantage of the chemical surface treatment method that micro-cracks do not exist in the unevenness to be formed. It aims at providing the processing method and the quartz glass jig processed by this method.

  That is, in the present invention, the surface treatment liquid is generally used as an etching liquid for quartz glass, and therefore, the surface of the quartz glass is formed with fine irregularities by using hydrofluoric acid that has a small environmental load and does not require an excessive drainage treatment facility. An object of the present invention is to provide a quartz glass surface treatment method and a quartz glass jig in which fine irregularities without microcracks are formed on the surface.

  As a result of intensive studies by the present inventors in order to solve the above problems, hydrofluoric acid is made into a fine mist to adhere to the quartz glass surface, and the mist of hydrofluoric acid particles and the quartz glass surface to which the fluorinated acid adheres are etched. It has been found that fine irregularities can be formed on the surface of quartz glass by utilizing the reaction.

  That is, the quartz glass surface treatment method of the present invention comprises hydrofluoric acid fine particles (hereinafter referred to as “hydrofluoric acid particles”) having a maximum particle size of 300 μm or less and an average particle size of 3 μm or more and 50 μm or less. Hydrofluoric acid mist or simply mist) is adhered to the surface of the quartz glass, and the quartz glass is etched only in the quartz glass portion to which the hydrofluoric acid fine particles are adhered. It is characterized by forming fine irregularities.

In the method of the present invention, the particle density of the hydrofluoric acid fine particles adhering to the quartz glass surface is preferably 50,000 or more and 1,000,000 or less per 1 cm ^{2 of the} quartz glass surface.

  In the method of the present invention, it is preferable that the quartz glass surface temperature is kept low in the range of 5 ° C. or more and 50 ° C. or less with respect to the ambient temperature containing the hydrofluoric acid fine particles. It is preferable that the hydrofluoric acid fine particles are formed by an ultrasonic nozzle or a precision spray nozzle.

  The quartz glass jig of the present invention is a quartz glass jig processed by the surface treatment method of the quartz glass of the present invention, and fine irregularities without microcracks are formed on the surface of the quartz glass jig. The surface roughness of the fine irregularities is 0.1 μm or more and 1.0 μm or less in Ra value, and 1.0 μm or more and 10 μm or less in Rmax value.

  According to the surface treatment method for quartz glass of the present invention, etching is performed by adhering 10% to 75% hydrofluoric acid to a mist having an average particle diameter of 3 μm to 100 μm and a maximum particle diameter of 300 μm or less to the quartz glass surface. Quartz glass with the same surface condition as when surface treatment is performed with a special chemical solution using acetic acid, ammonium fluoride, etc. as hydrofluoric acid can be manufactured. As a result, waste liquid treatment is extremely easy. At the same time, the environmental load can be greatly reduced. Furthermore, the amount of hydrofluoric acid to be used can be greatly reduced by the surface treatment method for quartz glass of the present invention. The quartz glass jig of the present invention has fine irregularities not accompanied by microcracks, and can be suitably used as a quartz glass jig for manufacturing semiconductors.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. However, the illustrated examples are shown by way of example, and various modifications can be made without departing from the technical idea of the present invention. Absent.

  An example of a mist generating apparatus used in carrying out the quartz glass surface treatment method of the present invention will be described with reference to FIG. FIG. 1 is a schematic explanatory view showing one structural example of a mist generation treatment apparatus. In FIG. 1, reference numeral 10 denotes a mist generation processing device, which has a mist generation device 11 that generates mist M. Reference numeral 12 denotes a mist generating chamber constituting the mist generating device 11, and a hydrofluoric acid reservoir 14 for storing hydrofluoric acid F is provided at the bottom of the mist generating chamber 12. An ultrasonic nozzle 16 is installed in the center of the mist generating chamber 12. The ultrasonic nozzle 16 is controlled by an ultrasonic nozzle control panel 18 provided outside the mist generating chamber 12.

The hydrofluoric acid reservoir 14 is connected to the pump P through a pipe 20a, and the pump P is connected to the ultrasonic nozzle 16 through a pipe 20b. The pump P is also connected to a pipe 20 c that opens above the hydrofluoric acid reservoir 14. V ₁ , V ₂ and V ₃ are valves provided in the pipes 20a, 20b and 20c. The hydrofluoric acid F stored in the hydrofluoric acid storage unit 14 is supplied to the ultrasonic nozzle 16 by the pump P via the pipes 20a and 20b, and is injected as mist M from the ultrasonic nozzle 16 to fill the mist generating chamber 12. To do. The hydrofluoric acid F can be circulated through the pipes 20a and 20c as necessary.

  A mist processing chamber 22 mist-processes an object to be processed 24 such as a quartz glass jig. A mist transport pipe 26 connects and connects the mist generation chamber 12 and the mist processing chamber 22, and performs an action of guiding the mist M generated in the mist generation chamber 12 to the mist processing chamber 22. A plurality of baffle plates 28a and 28b are erected in the mist conveyance path 26a inside the mist conveyance tube 26, and function to collect mist M exceeding a predetermined diameter (for example, 300 μm). In addition, 30a is a damper provided in the upper passage 12a of the mist generating chamber 12, and 30b is a damper provided in the upper passage 22a of the mist processing chamber 22.

  With the configuration described above, the mist M generated and filled in the mist generating chamber 12 moves and fills in the mist processing chamber 22 through the mist transfer pipe 26 and adheres to the surface of the object to be processed 24, and performs an etching treatment. Fine irregularities are formed on the surface of the processed object 24. As described above, since the mist M exceeding the predetermined diameter is collected by setting the baffle plates 28a, 28b upright on the mist transporting path 26a, the etching action by the mist M in the predetermined particle diameter range is performed. It can be done.

  Further, a mist M generated in the mist generation chamber 12 is formed in advance by forming a differential pressure between the mist processing chamber 22 and the mist generation chamber 12 (with the mist processing chamber 22 in a reduced pressure state). Can be guided and moved into the mist processing chamber 22 more smoothly.

  The quartz glass surface treatment method of the present invention comprises hydrofluoric acid fine particles having a maximum particle size of 300 μm or less, an average particle size of 3 μm or more and 50 μm or less, comprising 10% to 75% hydrofluoric acid. The quartz glass is etched only in the quartz glass portion to which the hydrofluoric acid fine particles are adhered, thereby forming fine irregularities on the surface of the quartz glass.

(Selection of mist diameter)
In order to attach a mist of hydrofluoric acid to the surface of the quartz glass and form fine irregularities on the quartz glass surface by the etching effect, the particle size of the mist is larger than the depth of etching (the height of the irregularities). It must be large and it must be smaller than the size of the irregularities to be formed.

  When unevenness is formed on the surface for the purpose of suppressing peeling of the film adhering to the quartz glass surface during film formation as a semiconductor processing jig, the degree of unevenness is 0.1 μm to 1 μm in terms of surface roughness Ra value, RmaX value Thus, it is known to be effective in the range of 1 μm to 10 μm (see Patent Document 2).

  Although the concentration of hydrofluoric acid and the treatment time are closely related, in order to form an unevenness of 0.1 μm in Ra value, hydrofluoric acid mist having a mist diameter 30 times or more is necessary. In this case, if the hydrofluoric acid concentration is high, deep etching can be performed with a mist having a small particle size, but if the concentration is low, a mist having a larger particle size is required. For this reason, the average particle size of the hydrofluoric acid mist must be at least 3 μm.

  On the other hand, when the mist diameter is increased, the surface roughness is increased, but the mist itself is likely to be unstable, and the container and the processed product are likely to drop off and flow out from the attached surface. If the mist diameter exceeds 300 μm, the mist itself is bonded in the air and falls in the form of raindrops, so that it is extremely difficult to disperse and attach the fine mist uniformly to the workpiece 24. For this reason, in the present invention, the maximum diameter of the hydrofluoric acid mist is required to be 300 μm or less, and preferably 200 μm or less.

  Also, the average particle size of the mist needs to be 50 μm or less. In order to limit the maximum diameter of such mist, the mist generator 11 and the mist use atmosphere (mist treatment chamber 22 in FIG. 1) are not directly connected, but at a moderate linear speed of about 10 cm / second to 50 cm / second. It is preferable to drop the large mist by conveying the mist to the workpiece 24, or to provide baffle plates 28a and 28b for collecting the large mist in the middle of the mist conveying path 26a.

  By transporting the mist to a certain distance from the mist generating device 11, the stability of the mist is remarkably improved. For example, the mist can be attached to the inner surface of the quartz glass tube. The mist in question in the present invention is generally considered to have a logarithmic normal distribution of particle diameter, but the average particle diameter referred to in the present invention is the particle diameter that gives the most frequent frequency (statistically the mode diameter). It is shown.

(Hydrofluoric acid concentration)
A higher concentration of hydrofluoric acid that forms mist is preferable because it increases etching efficiency and shortens the processing time. As described above, when the concentration of hydrofluoric acid is low, a relatively large mist diameter is required. However, when the particle diameter is large, the stability of the mist is lowered and the mist itself aggregates and drops.

  Even if such a problem does not occur, since the mist diameter is large, the density of the mist adhering to the quartz glass surface does not increase sufficiently, resulting in a decrease in the number of irregularities on the surface, resulting in a sufficient effect. There is also a problem that it is not possible. From such a viewpoint, the concentration of hydrofluoric acid that forms mist must be at least 10%.

  On the other hand, since hydrofluoric acid itself is a very strong acid, when its concentration is high, it often causes a problem in the mist generator. Although the present invention is not limited to the mist generation method, for example, the limit of the concentration of hydrofluoric acid that can be used in a mist generation apparatus using an ultrasonic vibrator is about 25%. In a precision spray nozzle (for example, a small precision vortex nozzle MN90P manufactured by Atmax Co., Ltd.), a hydrofluoric acid having a high concentration of up to about 80% can be used by using a hydrofluoric acid resistant nozzle.

  However, in consideration of work safety, the maximum concentration of hydrofluoric acid is up to 75%. Therefore, the concentration of hydrofluoric acid forming mist is 10% to 75%, preferably 15% to 50%. It must be an acid.

(Mist density)
The density of the mist is determined by the density of the unevenness on the surface. When surface treatment is performed with a special chemical solution disclosed in Patent Documents 1 to 3, the density of the unevenness for effectively functioning as a semiconductor processing jig has a density of 50,000 or more per 1 cm ² of the quartz glass surface. Since it is not more than 1,000, preferably 100,000 / cm ² or more and 500,000 / cm ² , the mist density needs to be in the same range.

  The quartz glass jig of the present invention is a quartz glass jig treated by the surface treatment method of the quartz glass of the present invention, and the method has fine irregularities without microcracks on the surface of the quartz glass jig. The surface roughness of the fine irregularities is 0.1 μm or more and 1.0 μm or less in Ra value and 1.0 μm or more and 10 μm or less in Rmax value.

  The present invention will be described more specifically with reference to the following examples. However, it is needless to say that these examples are shown by way of illustration and should not be construed in a limited manner.

(Examples 1-4)
A quartz glass tube having an outer diameter of 200 mm, a wall thickness of 5 mm, and a length of 500 mm is placed in a 500 mm × 500 mm × 1000 mm transparent vinyl chloride container C using an apparatus similar to the mist generation processing apparatus 10 shown in FIG. The mist was introduced into the container (mist processing chamber 22) from the adjacent mist generator 11 through the mist transport pipe 26 at a linear speed of 50 cm / sec.

  Mist generation is 10% hydrofluoric acid (Examples 3 and 4) or 25% as shown in Table 1 in the hydrofluoric acid resistant ultrasonic nozzle 16 (Pretech fine jet, but special specification that can use hydrofluoric acid). The ultrasonic vibration was applied while supplying hydrofluoric acid (Examples 1 and 2). In the case of hydrofluoric acid, the generated mist particle diameter cannot be measured because it is highly corrosive. Therefore, mist was generated using pure water under the same conditions and measured with a light diffusing fine particle measuring instrument.

  At this time, the average particle diameter of the mist generated by changing the voltage applied to the ultrasonic oscillator was changed in the range of 5 μm to 80 μm as shown in Table 1 (Example 1: 5 μm, Example 2: 50 μm, Example 3: 10 μm, Example 4: 80 μm). Further, by changing the operation time of the mist generating device 11, the density of the hydrofluoric acid mist adhering to the quartz glass surface was changed by changing the mist density filling the processing container (mist processing chamber 22). Moreover, all the mists having a particle diameter of 300 μm or more could be collected by the baffle plates 28a and 28b provided in the mist transport path 26a of the mist transport pipe 26.

  After confirming that a predetermined amount of mist adhered to the surface of the quartz glass, the mist generating device 11 was stopped in order to avoid any further mist from adhering to the surface of the quartz glass tube. After leaving the quartz glass tube surface to be etched with hydrofluoric acid mist for a predetermined time (the treatment time in Table 1), the inner surface of the vessel (mist treatment chamber 22), the atmosphere inside the vessel, and the quartz glass tube are sufficiently showered with pure water. After washing, the quartz glass tube was taken out.

  The obtained quartz glass tube was etched on the inner and outer surfaces with hydrofluoric acid mist to form fine irregularities and surface-treated in the form of ground glass. The inner surface of the obtained quartz glass tube was measured with a surface roughness meter. The measurement results are shown in Table 1.

  Since it was impossible to measure directly the adhesion density of hydrofluoric acid mist on the quartz glass surface, mist was generated under the same conditions as in each example using pure water instead of hydrofluoric acid. Then, an adhesion experiment on a quartz glass tube was performed, and the adhesion mist density was examined by observing it with a microscope. The measurement results are also shown in Table 1.

(Example 5)
Using a device similar to that of Example 1, a mist is heated while supplying a throwing heater in which 25% hydrofluoric acid is coated with polytetrafluoroethylene in a pool of hydrofluoric acid (hydrofluoric acid reservoir 14) and heating to about 50 ° C. The surface treatment was performed under the conditions shown in Table 1. Since the temperature of the quartz glass was 20 ° C. which is room temperature, it was confirmed that the temperature difference between the hydrofluoric acid mist and the quartz glass was 10 ° C. or more. The conditions for generating mist other than those shown in Table 1 were the same as in Example 1. The results are also shown in Table 1.

(Examples 6 to 8)
Using the same apparatus as in Example 1, a quartz glass tube (object to be processed 22) of the same size as in Example 1 was installed in a transparent vinyl chloride container (mist processing chamber 22), and the mist in the adjacent mist generator 11 was used. The generation method is changed to a small precision vortex nozzle MN90P manufactured by Atmax Co., and spraying is performed while flowing 40% hydrofluoric acid at a flow rate of 30 mL / min (Example 6) and 200 mL / min (Example 7). The experiment was conducted by generating mist using compressed air of 3.0 kg / cm ² . Further, 60% hydrofluoric acid was sprayed at a flow rate of 100 mL / min (Example 8) with compressed air of 3.0 kg / cm ² . Further, in order to change the density of the hydrofluoric acid fine particles adhering to the surface of the quartz glass tube, the treatment time was changed between 15 minutes and 20 minutes as shown in Table 1 (Examples 6, 7: 20 minutes, Examples 8:15 minutes). Experimental conditions and results are also shown in Table 1.

  In Table 1, the appearance was mainly focused on the presence or absence of unevenness by visual inspection, but it was not inferior at all compared to the chemical-treated product using acetic acid shown in Example 1 of Patent Document 2, in particular. The sample was marked with ◎, the sample with slight unevenness, which was judged as having no practical problem, was marked with O, and the sample with clearly poor quality was marked with ×.

  As shown in Table 1, in Examples 1 to 8, a quartz glass having the same surface state as that obtained when surface treatment was performed with a special chemical solution using acetic acid, ammonium fluoride or the like for hydrofluoric acid was produced. Was made.

It is a schematic explanatory drawing which shows one structural example of a mist generation processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mist generation processing apparatus 11 Mist generation apparatus 12, 12a Mist generation chamber 14 Hydrofluoric acid storage part 16 Ultrasonic nozzle 20a, 20b, 20c Pipe 22, 22a Mist processing chamber 24 To-be-processed object 26 Mist conveyance pipe 26a Mist conveyance path 28a, 28b baffles 30a, 30b damper M mist F hydrofluoric P pumps V _1, V _2, V ₃ valve

Claims (6)

  A hydrofluoric acid particle composed of 10% to 75% hydrofluoric acid and having a maximum particle size of 300 μm or less and an average particle size of 3 μm to 50 μm was adhered to the surface of the quartz glass, and the hydrofluoric acid particles were adhered A method for treating a surface of quartz glass, comprising: forming fine irregularities on the surface of the quartz glass by etching the quartz glass only in the quartz glass portion. ^2. The surface treatment of quartz glass according to claim 1, wherein a particle density of the hydrofluoric acid fine particles adhering to the quartz glass surface is 50,000 or more and 1,000,000 or less per 1 cm ² of the quartz glass surface. Method.   3. The method for treating the surface of quartz glass according to claim 1, wherein the surface temperature of the quartz glass is kept low in the range of 5 ° C. or more and 50 ° C. or less with respect to the ambient temperature containing the hydrofluoric acid fine particles.   The surface treatment method for quartz glass according to any one of claims 1 to 3, wherein the hydrofluoric acid fine particles are formed by an ultrasonic nozzle.   The surface treatment method for quartz glass according to claim 1, wherein the hydrofluoric acid fine particles are formed by a precision spray nozzle.   A quartz glass jig treated by the surface treatment method for quartz glass according to any one of claims 1 to 5, wherein fine irregularities without microcracks are formed on the surface of the quartz glass jig. A quartz glass jig characterized in that the surface roughness of the fine irregularities is 0.1 μm or more and 1.0 μm or less in terms of Ra value and 1.0 μm or more and 10 μm or less in terms of Rmax value.

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