JP2010042991A - Silica glass jig used in process for manufacturing semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica glass jig by which particles possibly contaminating a semiconductor device are not produced when the jig is used and treatment conditions need not be changed even when the jig is repeatedly used. <P>SOLUTION: In the silica glass jig used in a process for manufacturing a semiconductor, irregularities with a centerline-average roughness Ra of from 0.1 to 20 μm exist on a part or all of the surface thereof, wherein the irregularities have a multi-layer structure composed of large wave-shaped recesses and projections and fine shallow bowl-shaped recesses existing on the surfaces of the recesses and projections, and further the depth of each bowl-shaped recess is shallow and smaller than the edge diameter of the bowl-shaped recess and there is no sharply-angled projection on the edge between the bowl-shaped recesses. Further, in the silica glass jig, when the surface etched with an aqueous solution of hydrogen fluoride having concentration of 3.0-4.0% at 17-23°C for 15-17 h and the surface not subjected to such an etching treatment are measured on the basis of JIS B0601 by using a stylus type surface roughness measuring instrument in which R of the tip of a stylus is within a range of 2-10 μm, the variation rate of the centerline-average roughness Ra is ≤50%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silica glass jig used in a semiconductor manufacturing process, and more particularly, to a silica glass jig having fine irregularities on the surface and a small change in surface state with respect to slight surface etching.

Silica glass jigs are used in various processes such as a diffusion process, a vapor phase growth process, and an etching / ashing process in the manufacture of semiconductor elements. The surface of this silica glass jig is treated with sand blasting or grinding to make it opaque with irregularities, or it is smooth and transparent with flame polishing called mirror polishing or baking finish, etc. Although it is appropriately selected depending on the application and the like, many jigs having a transparent finished surface that is easy to clean and difficult to get dirty are used. Among them, CVD (Chemical
For example, a polysilicon film is grown on a semiconductor element by a vapor deposition method or the like. At this time, a polysilicon film is deposited as a by-product on a transparent silica glass jig, and the semiconductor film is peeled off to form particles. Contamination of the device occurs. Therefore, it was necessary to remove by-products regularly. For the removal, a solution containing hydrofluoric acid and nitric acid is generally used, but the surface of the smooth jig is also etched at the same time to roughen the surface, resulting in a change in surface condition such as surface area. In addition, the amount of attached by-products fluctuates, and the amount of gas phase reaction gas consumed also fluctuates, which makes it difficult to control the growth amount of the polysilicon film on the semiconductor element. Therefore, it was attempted to form fine irregularities on the jig surface by sandblasting and actively capture by-products there to prevent the generation of particles, but this time it occurred during the machining of fine irregularities. Fine particles of silica glass were scattered from damaged parts such as processed plastic layers and microcracks during use, generating particles that contaminated semiconductor elements. In addition, when the by-product becomes thick, damage due to the difference in thermal expansion between silica glass and polysilicon occurs. To prevent this, cleaning by gas etching or wet etching is performed before using the jig. As in the case of a jig having a surface, it is necessary to periodically remove by-products, and there is a problem that a fine uneven surface is etched at the same time to change the surface state.

  The above problems are not limited to the diffusion to the semiconductor element and the vapor phase growth process, but the same is true in the etching process. That is, in the process of etching and ashing using plasma etc. while flowing process gas, by-products may accumulate on the silica glass jig and peel off to generate particles. As a result, fine irregularities were formed on the surface, and byproducts were actively captured to prevent generation of particles. However, there has been a problem that fine fragments of silica glass are scattered by using plasma from damaged portions such as processed plastic layers and microcracks generated during processing of irregularities and become particles that contaminate the semiconductor element during use. In particular, in dry etching, the surface of a silica glass jig is etched very similar to the treatment with a hydrogen fluoride-containing solution, the surface state changes greatly, and it is difficult to control the etching process of the semiconductor element itself. It was.

In order to solve the above problems, a machined jig is etched with a hydrogen fluoride-containing solution to release microcracks, and the surface of the silica glass jig or silica glass jig with a microcrack-free surface is machined. Then, it is treated with a solution containing hydrogen fluoride and ammonium fluoride to form 20-300 μm excavity recesses and grooves with a width of 0.5-50 μm at intervals of 20-30 μm on the surface. There has been proposed a silica glass jig in which small protrusions having a width of 1 to 50 μm and a height of 0.1 to 10 μm are uniformly dispersed in and between the grooves. However, in actual use, any of the above jigs has a large mortar shape due to use, and the amount of attached by-product suddenly changes or the unevenness is reduced. There was a drawback.
Japanese Patent Laid-Open No. 10-59744 Japanese Patent Laid-Open No. 2002-104843

  In view of such a current situation, the present inventors have conducted extensive research, and as a result, the surface roughness of the silica glass jig is set to 0.1 to 20 μm in the centerline average roughness Ra, and even for a slight surface etching process. By using a surface with a small change in surface condition, there is no separation of by-products or scattering of fine fragments of silica glass, and there is little change in processing gas consumption, making it easy to control processing in each process. And the present invention has been completed. Ie

  An object of the present invention is to provide a silica glass jig that does not generate particles that contaminate a semiconductor element during use, and that does not change processing conditions even after repeated use.

  In the silica glass jig used in the process of producing a semiconductor according to the present invention, unevenness having a centerline average roughness Ra of 0.1 to 20 μm exists on a part or all of the surface thereof, and the unevenness is large. It has a multilayer structure consisting of wavy irregularities and fine shallow bowl-shaped depressions existing on the surface thereof, and the depth of the bottom of the bowl-shaped depressions is shallower than the edge diameter of the depressions at the edge between the depressions. Is a surface when etched with a hydrogen fluoride aqueous solution having a sharpness of 3.0 to 4.0% and a liquid temperature of 17 to 23 ° C. for 15 to 17 hours, and a surface when not etched. The rate of change of the centerline average roughness Ra is 50% or less when measured based on JISB0601 using a stylus type surface roughness measuring device in which R at the tip of the stylus part is in the range of 2 to 10 μm. It concerns on the silica glass jig characterized by these.

  The silica glass jig of the present invention is a jig used in a process of manufacturing a semiconductor element, such as a furnace core tube, a wafer mounting boat, an etching / ashing chamber, etc. It is a jig that has unevenness of 0.1 to 20 μm in center line average roughness Ra in all and has a small change in surface state with respect to a slight surface layer etching process. The change in the surface state is as small as 3.0 to 4.0% in the etching process with a hydrofluoric acid solution having a liquid temperature of 17 to 23 ° C. for 15 to 17 hours and before the etching. The center line average roughness based on JISB0601 was measured with a stylus type surface roughness measuring device in which R at the tip of the stylus part was in the range of 2 to 10 μm, and the change rate of the center line average roughness was 50. % Or less. That is, the surface of the silica glass jig is changed by actual etching, for example, etching by plasma gas. Specifically, Ra increases at an early stage, but the magnitude of the change is small in the change of the surface state. In relation to the change rate of the centerline average roughness indicating the roughness, if the change rate is 50% or less, the change in Ra remains small even in actual use. If the concentration of the hydrofluoric acid solution is less than the above range, the change takes too much time and is not efficient. If the concentration exceeds the above range, the initial change speed is high and the determination time is short, but the measurement object is taken out from the solution. Thus, an error occurs until the surface is replaced with water and etching is stopped. Further, the temperature of 17 to 23 ° C. of the hydrofluoric acid solution is adopted because the temperature is most common.

  Furthermore, the etching processing time of 15 to 17 hours is a time for obtaining a highly accurate change rate for determination. For the measurement of the rate of change, it is important to use a stylus type surface measuring device in which R at the tip of the stylus part is 2 to 10 μm based on JISB0601. The reason for using a stylus type surface measuring device in which R at the tip of the stylus part is 2 to 10 μm is that the change in the surface state of the silica glass jig during actual use is caused by microcracks present in the initial state surface. Enlargement is caused by the etching process, or jagged irregularities on the surface thereof change greatly due to a shape change caused by the etching process. In a non-contact type measuring device, for example, a measuring device using reflected light of a laser, the center line average roughness calculated from the measured shape is correct, but it is directly buried by a by-product during use. This is because even a narrow valley portion is detected, and it is difficult to understand a large state change in which processing conditions change during use. By using the measuring method using this stylus type surface measuring device, it is easy to capture not only the change of the convex part but also the change of the valley part particularly sensitive to the adhesion state of the by-product. The R of the tip of the stylus part is 2 to 10 μm from 2 μm, which is a range where thin valleys are not detected, to 10 μm where substantial unevenness can be determined. Can be easily measured.

  In the actual use of the silica glass jig, there is an appropriate amount of by-product trapped according to the process used. For example, in the case of a CVD process, excess gas for film growth on the wafer is caused by plasma or the like in a dry etching process. In some cases, the etched reaction gas causes the surface of the silica glass jig to be roughened, and more is trapped and deposited on the jig as a by-product. If the amount of by-product deposited is too large, the gas for forming a film on the wafer is reduced more than necessary, and the growth and etching of the film are hindered. On the other hand, if the amount of trapping is small, particles are generated due to peeling or the like, and the roughness and state of the silica glass jig due to etching during use change from the initial state, thereby raising the same problem as described above. The surface irregularities of the silica glass jig include saw-shaped irregularities, jagged edges with irregular and sharp peaks and valleys, and trapezoidal convex parts, all of which are edged by etching during actual use. It becomes a large bowl-shaped unevenness with sharp points, and the byproduct trapping ability and the like greatly change from the initial state. In addition, when the bowl-shaped irregularities are formed from the initial state, the surface area is small, so the byproduct capture ability cannot be practically used, and the sharp edges of the bowl-shaped edge fall off, generating particles. To do. Therefore, in the silica glass jig of the present invention, unevenness having a centerline average roughness Ra of 0.1 to 20 μm is present on a part or all of the surface thereof. The presence of the unevenness ensures the capture of by-products and suppresses the peeling of the film. Preferably, the unevenness has a multiple structure in which large unevenness and a fine shallow bowl-shaped recess are formed on the surface. By having this multiple structure, it is possible to secure unevenness capable of capturing a by-product having a required thickness due to large wavy unevenness that is difficult to change by light etching. Further, by making the large wavy irregularities have fine shallow bowl-shaped irregularities, the captured by-products can be fixed without peeling, and a jig having a stable surface can be obtained. It is particularly desirable that the shallow bowl-shaped recess has a bottom depth smaller than the edge diameter of the recess, and that the edge of the boundary between adjacent recesses is not an acute convex. Thus, even if the recess is etched during use, the vicinity of the edge is also uniformly damaged, and it is possible to prevent the occurrence of a protruding edging that is easy to drop off between adjacent recesses.

  The silica glass jig of the present invention can be produced by repeatedly applying the physical surface layer removing means and the chemical surface layer removing means alternately twice or more. Preferably, the processing conditions are selected so that the surface roughness formed by the physical surface layer removing means decreases sequentially.

  The physical surface layer removing means refers to a grinding process using a fixed abrasive wheel, a polishing process using free abrasive grains, a blast process using free abrasive grains, a process using liquid honing, or a combination thereof. As the fixed abrasive grindstone, specifically, a resin bond type diamond grindstone is exemplified. As the free abrasive grain, silica or SiC is exemplified. As the treatment by liquid honing, the free abrasive grain is dispersed in a liquid. For example, a spraying process. In this physical surface layer removing means, a damage layer such as a processed plastic layer or a microcrack is formed on the surface of the silica glass, and fine fragments of the silica glass are scattered when the jig is used, which becomes a generation source of particles. In addition, inhomogeneous erosion occurs during the etching process, deep grooves are formed due to incomplete opening of microcracks, the surface state changes greatly, and it is necessary to change processing conditions such as the CVD process and the etching process. However, by applying a chemical surface layer removing means subsequent to the physical surface layer removing means, the processing plastic layer is removed and the microcracks are released, so that the generation of particles is reduced and the fluctuation of the surface state is reduced. If the removal amount of the surface layer by the chemical surface layer removing means is small, the processed plastic layer and the microcracks are not sufficiently removed. Therefore, if the processed plastic layer formed by the physical surface layer removing means and the damaged layer with microcracks are sufficiently removed, large grooves, bowl-shaped or mortar-shaped concave portions can have many dents with sharp outer edges. . In particular, fine glass fragments are likely to scatter from the sharp edge of the outer periphery. There is a processing method described in Patent Document 2 as a processing method that does not generate a dent with a sharp edge on the outer periphery. In this method, however, a damaged layer such as a processed plastic layer or a microcrack formed by a physical surface layer removing means is removed. Is not sufficient, and the change in the surface state during the etching process becomes large. In addition, when etching during actual use proceeds, a large number of concave portions with sharp edges on the outer periphery appear and particles are easily generated.

  In the manufacturing method of the present invention, after the first physical surface layer removing means, a surface where the microcracks on the surface are opened by the chemical surface layer removing means, for example, a surface having many mortars and bowl-shaped irregularities was formed. Later, the physical surface layer removing means is applied again, the sharp portions of the irregularities are waved, and the chemical surface layer removing means is further applied, so that the processed plastic layer remaining on the relatively flat surface or slightly remains. The micro crack is opened. The physical surface layer removing unit and the chemical surface layer removing unit are preferably repeatedly applied two or more times alternately. Thereby, the jig | tool with a small change of the surface state of the silica glass jig | tool in use is obtained. More preferably, the physical surface layer removing means is selected as the next physical surface layer removing means so that the surface roughness is smaller than the first. In the range where the shape of the large wavy irregularities formed thereby does not change significantly, not only the damage of the next physical surface layer removing means and micro cracks can be easily released by the next chemical surface layer removing means, but also the large wavy shape It is possible to obtain a multiple structure having a large number of bowl-shaped recesses on the uneven surface. For example, abrasive grains having a relatively large grain size are used first, and abrasive grains having a relatively small grain size are used in the next removing means. In that case, a combination of physical surface removal means that combines a grinding process with a fixed abrasive grindstone followed by a polishing process with loose abrasive grains can also be employed. For example, after first using a fixed abrasive wheel containing # 120 diamond abrasive grains, sandblasting with # 600 SiC loose abrasive grains is applied.

  Examples of the chemical surface layer removing means used in the present invention include treatment with a solution containing hydrogen fluoride. Preferably, the chemical surface layer removing means after the last physical surface layer removing means includes the above solution. Furthermore, it is preferable to contain ammonium fluoride. As a result, although the mechanism is not clear, for example, sharp protrusions and other sharp protrusions formed on the outer peripheral edge of the bowl-shaped mortar-shaped recess formed by the chemical surface layer removing means are removed, and the smooth uneven surface It can be. This is because the crystal formed by the reaction of hydrogen fluoride with ammonium fluoride and silica glass often occurs at the bottom of the bowl, for example, and does not occur at the protrusion or the crystal that has absorbed the protrusion is detached immediately, As a result, it is considered that the protrusion is selectively removed by etching, and a rounded shape having no acute angle portion is obtained. More preferably, fine particles of a resin having a particle diameter of 10 to 200 μm, silica, ceramic, or a combination thereof are dispersed in the solution containing hydrogen fluoride. Dispersion of the fine particles facilitates removal of the damaged layer on the jig surface, increases the ability to form fine irregularities, and simplifies the manufacturing procedure. Furthermore, the processing efficiency can be further improved by adding ultrasonic vibration and stirring means.

  The silica glass jig of the present invention produces less particles during use, and the processing conditions hardly change even after repeated use, and has the effect of stably processing a high-quality semiconductor element. Moreover, the silica glass jig can be easily manufactured by repeatedly applying a specific physical surface layer removing means and a chemical surface layer removing means twice or more, and has a high industrial value.

  Examples of the present invention will be described below, but the present invention is not limited thereto. In addition, the centerline average roughness Ra of Example 1 and Comparative Example 1 below was measured with a surface roughness meter (Surfcom 300B manufactured by Tokyo Seimitsu Co., Ltd.). In other examples, etc., a surface roughness meter (SJ-400) manufactured by Mitutoyo Corporation was used.

A surface of quartz glass having a diameter of 300 mm was ground with a resin bond grindstone containing # 300 diamond abrasive grains to prepare a disk-shaped dry etching jig. The center line average roughness Ra of the obtained jig was 1.2 μm. This jig was immersed in a 50% hydrofluoric acid solution for 10 minutes. The obtained jig had a center line average roughness Ra of 2.8 μm. Subsequently, the surface of the jig was removed with a resin bond grindstone of # 1000 SiC abrasive grains, the center line average roughness Ra was set to 0.5 μm, and further, 15% by mass of hydrogen fluoride, 15% by mass of ammonium fluoride, It was treated for 1 hour with a treatment solution comprising 50% by mass of acetic acid and water. The centerline average roughness Ra at that time was 1.4 μm. The jig was immersed in a hydrofluoric acid solution at 20 ° C. and 3.5% by mass, and the change in Ra was examined. The surface photograph observed with the microscope at the time of 0 hours is shown in FIG. 1, and the surface photograph observed with the microscope after the etching treatment for 16 hours is shown in FIG. Furthermore, the photograph observed with the scanning electron microscope at the time of 0 hours is shown in FIG.
(Comparative Example 1)

  A quartz glass jig similar to that in Example 1 was ground with a resin-bodied grindstone containing # 300 diamond abrasive grains to produce a disk-shaped dry etching jig. The center line average roughness Ra of the obtained jig was 1.2 μm. This jig was then immersed in a 10% hydrofluoric acid solution for a minute. Ra at that time was 1.3 μm. When the jig was examined for changes in surface roughness caused by 3.5% by mass of hydrofluoric acid in the same manner as in Example 1, it was as shown in Table 1.

As shown in Table 1 above, the silica glass jig of Example 1 of the present invention has a surface condition change such as Ra as compared with Comparative Example 1 in an etching test of a 3.5% by mass hydrofluoric acid solution. It was extremely small. Therefore, the jigs of Example 1 and Comparative Example 1 were actually put into a CF ₄ / Ar gas, 2 kw plasma dry etching apparatus, and 5 batches of processing were performed with the jig of Example 1; The number of occurrences was less than 10 in any batch. On the other hand, in the jig of Comparative Example 1, a large amount of particles of 50 or more were generated in the third batch, and the use was stopped. In addition, the Ra after each use is 2 μm for the jig of Example 1 and 5.2 μm for the jig of Comparative Example 1, and there is a large difference as in the etching test using a 3.5 mass% hydrofluoric acid solution. It was. Further, when the etching rates of the fifth batch of Example 1 and the third batch of the processed wafer of Comparative Example 1 were compared, the rate of the jig of Comparative Example 1 was lower than that of the jig of Example 1.

A vertical type vapor phase growth wafer boat corresponding to a silicon wafer having a diameter of 150 mm was prepared. The wafer boat was sandblasted with # 150 silicon carbide abrasive grains, then treated with a 15% hydrofluoric acid solution for 20 minutes, and further sandblasted with # 600 silicon carbide abrasive grains. It was treated for 1 hour with a treatment solution consisting of 14% by mass of hydrogen fluoride, 12% by mass of ammonium fluoride and water. The surface of the obtained wafer boat was photographed with a scanning electron microscope (SEM). The results are shown in FIGS. The surface roughness of the wafer boat was 2.1 μm in terms of centerline average roughness Ra. As shown in FIGS. 4 and 5, it was a multiple structure in which shallow concave portions were formed on the surface of large wavy irregularities. The wafer boat was subjected to an etching test with a 3.5% hydrofluoric acid solution at 20 ° C. for 16 hours. FIGS. 6 and 7 show photographs taken by SEM of the surface of the wafer boat after the test. It was a multi-layer structure although the number of wave-like concave portions larger than before was slightly widened to reduce the number. At this time, Ra was 2.1 μm. Further, the wafer boat was used in an actual silicon nitride vapor phase growth process to deposit a 2 μm film. For each cumulative growth in the growth step, washing for 1 hour with a 4% hydrofluoric acid solution was repeated 5 times. The surface Ra after use was 2.5 μm.
(Comparative Example 2)

  The same wafer boat as in Example 2 was subjected to sand blasting treatment with # 150 silicon carbide abrasive grains, and further subjected to sand blasting treatment with # 600 silicon carbide abrasive grains. Next, treatment was performed for 1 hour with a 10% hydrofluoric acid solution. The surface of the obtained wafer boat was photographed with a scanning electron microscope (SEM). The results are shown in FIGS. The roughness of the wafer boat was 2.2 μm in terms of centerline average roughness Ra. This wafer boat was subjected to an etching test for 16 hours with a 3.5% hydrofluoric acid solution at 20 ° C. in the same manner as in Example 2. 10 and 11 show photographs of the surface of the wafer boat after the test taken with an SEM, which differs greatly from the surface of FIG. 6 in which the concaves having large concave shapes and sharp edges are continuous, and Ra is 4.8 μm. It was. Further, the wafer boat was used in an actual silicon nitride vapor phase growth process, and for each cumulative growth of a film having a thickness of 2 μm, washing with a 4% hydrofluoric acid solution for 1 hour was repeated five times. The surface Ra after use was 5.1 μm. Further, the film thickness growing on the wafer abruptly decreased from the third time, and the increase of particles on the treated wafer was observed.

  Since the silica glass jig of the present invention does not generate particles that contaminate semiconductor elements during use, and the processing conditions do not change even after repeated use, the furnace core tube, wafer mounting boat, etching It can be usefully used as an ashing chamber, ring, or plate.

2 is a 500 × photograph of the surface of a dry etching jig of Example 1 observed with a microscope. It is a 500 times as many photograph observed with the microscope, after immersing the jig | tool surface for dry etching of Example 1 in 3.5 mass% hydrofluoric acid for 16 hours. 3 is a 500 × photograph of the surface of a dry etching jig of Example 1 observed with a scanning electron microscope. 4 is a 200 × photograph of the wafer boat of Example 2 observed with a scanning electron microscope. 4 is a 1,000 times photograph of the wafer boat of Example 2 observed with a scanning electron microscope. It is a 200 times photograph observed by SEM after performing the etching test of the wafer boat of Example 2 for 16 hours with 20 degreeC and a 3.5% hydrofluoric acid solution. It is a 1000 times photograph observed by SEM after performing the etching test of the wafer boat of Example 2 for 16 hours with 20 degreeC and a 3.5% hydrofluoric acid solution. 4 is a 200 × photograph of the wafer boat of Comparative Example 2 observed with an SEM. It is a 1000 times photograph which observed the wafer boat of the comparative example 2 with SEM. It is a 200 times photograph observed by SEM after performing the etching test for 16 hours for the wafer boat of the comparative example 2 with 20 degreeC and a 3.5% hydrofluoric acid solution. It is a 1,000 times photograph which observed the wafer boat of the wafer boat of the comparative example 2 after 20-degree C and a 3.5% hydrofluoric acid solution for 16 hours, and observed with SEM.

Claims (1)

In the silica glass jig used in the process of manufacturing a semiconductor, there are irregularities having a center line average roughness Ra of 0.1 to 20 μm on a part or all of the surface, and the irregularities are large wavy irregularities. It has a multilayer structure composed of fine shallow bowl-shaped depressions existing on the surface, and the depth of the bottom of the bowl-shaped depression is shallower than the edge diameter of the depressions, and the edges between the depressions have sharp projections. There is no stylus, and the surface when etched for 15 to 17 hours with a hydrogen fluoride aqueous solution having a concentration of 3.0 to 4.0% and a liquid temperature of 17 to 23 ° C. is compared with the surface when not etched. The rate of change of the center line average roughness Ra when measured according to JISB0601 using a stylus type surface roughness measuring device in which R at the tip of the part is in the range of 2 to 10 μm is 50% or less. Silica glass jig.

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