JP2000021888A - Silicon wafer heat-treating quartz glass jig having high- purity grooved surface and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid depositing transition metal element foreign substances, without providing a sharp irregularity based on a fine irregularity or opening of microcracks by forming a grooved surface having a hexagonal pattern structure and specified center line mean surface roughness of the entire grooved surface. SOLUTION: The quartz glass jig has a grooved surface forming a hexagonal pattern structure with irregularity coupled hexagonal protrusions having mountain-like sections with gentle recesses sandwiching them, the mean spacing between the protrusions of the hexagonal pattern structure is 20-200 μm, the max. height Rmax to the recess of the protrusion is 2-20 μm, it is not practical to cut so that the center line mean roughness Ra is less than 0.5 μm, and if exceeding 5 μm, an Si wafer is damaged by its roughness, and hence the surface roughness of the entire grooved surface is set to a center line mean roughness Ra of 0.5-5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for heat treatment of a silicon wafer having a high-purity groove cut surface and a method of manufacturing the same.
More specifically, the present invention relates to a high-purity quartz glass jig for heat treatment of a silicon wafer having no quartz glass particles or transition metal element foreign matter on a grooved surface of the quartz glass jig for heat treatment of a silicon wafer, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a heat treatment jig for a silicon wafer, a quartz glass jig has been used because of its heat resistance and high purity. In the processing of the quartz glass jig, a diamond blade is generally used because a large number of grooves need to be cut at a constant pitch and with high precision, such as a wafer boat. However, since silica glass is a brittle material, microscopic irregularities and microcracks are generated on the processing surface by cutting with a diamond blade to damage the silicon wafer, or foreign substances due to various transition metal elements derived from the binder of the diamond blade Remains on the cutting surface,
It has the disadvantage that it melts and diffuses during heat treatment of the silicon wafer to contaminate the wafer. For this reason, a method of lightly etching and cleaning the quartz glass jig with a hydrofluoric acid solution after cutting with a diamond blade has been proposed.However, this light etching cleaning with dilute hydrofluoric acid roughens the grooved surface and damages the wafer, Alternatively, since the cleaning is not perfect, various transition metal element foreign matters remain and contaminate the silicon wafer, which may lower the product yield. In addition, a so-called fire polishing method has been proposed, in which the grooved surface after grinding is burned with a burner flame such as an oxyhydrogen burner or a propane burner to remove fine irregularities and microcracks generated by the cutting process to make a smooth surface. However, this method is not a satisfactory treatment method because contamination by a burner crater and a gas may occur in addition to contamination by melting and diffusion of foreign substances attached during cutting.

[0003]

In view of the current situation,
The present inventors have conducted intensive studies and found that a silica glass heat-treated member processed with a diamond blade was processed under predetermined cutting conditions and etching conditions, thereby forming a turtle structure on the grooved surface and having fine irregularities. It has been found that a quartz glass jig for heat treatment of a silicon wafer can be obtained in which sharp irregularities due to the opening of micro-cracks and smoothness of the micro-cracks are smoothed, and various transition metal element foreign matters are completely removed. That is,

An object of the present invention is to provide a quartz glass jig for heat-treating a silicon wafer having a high-purity groove cut surface having no fine irregularities or sharp irregularities due to opening of microcracks and having no adhesion of transition metal element foreign matter. With the goal.

Another object of the present invention is to provide a quartz glass jig for heat-treating silicon wafers having a novel high-purity grooved surface having a grooved surface having a turtle structure.

Another object of the present invention is to provide a method of manufacturing a quartz glass jig having a high-purity groove cut surface for silicon wafer heat treatment.

[0007]

According to the present invention, there is provided a quartz glass jig for heat-treating a silicon wafer having a grooved surface formed by cutting, wherein the grooved surface has a turtle structure and the entire grooved surface is provided. The present invention relates to a quartz glass jig for heat treatment of a silicon wafer having a high-purity groove-cut surface, wherein the surface roughness of the quartz glass jig is 0.5 to 5 μm in center line average roughness (R _a ), and a method of manufacturing the same.

As described above, the quartz glass jig for heat-treating a silicon wafer according to the present invention has a grooved surface having a tortoiseshell structure, and the surface roughness of the entire grooved surface is the center line average roughness (R _a ).
Is a quartz glass jig in the range of 0.5 to 5 μm.
The tortoiseshell structure is a structure in which polygonal projections are irregularly connected, and the cross section has a mountain-shaped projection and a gentle concave portion sandwiching the projection. FIG. 1 shows a schematic cross-sectional view of the projection. The average spacing between the protrusions of this tortoiseshell structure is 20 to 2
00 μm, the maximum height of the projection relative to the recess (R _max ) is 2
It is preferably in the range of ２０20 μm. The surface roughness of the entire grooved surface of the quartz glass jig for heat treatment of a silicon wafer is 0.5 to 5 μm in center line average roughness (R _a ).
Must be in the range. The center line average roughness is 0.5
Cutting to less than μm is not practical in terms of productivity and cost, and if it exceeds 5 μm, even if the cutting surface has a turtle structure, the silicon wafer is damaged by the roughness, which is not preferable.

The quartz glass jig for heat treatment of a silicon wafer is formed by cutting a quartz glass jig for heat treatment by cutting with a diamond blade, and then cutting the quartz glass jig from 20 to 70.
Using hydrofluoric acid of wt%, temperature (T) 273-323K
And Equation 2

[0010]

[Formula 2] t = V / [7.2 × C ^2.4 × exp ｛−2.7
× 10 ⁴ /(8.31×T)}] (where V is the etching amount (μm), C is the hydrofluoric acid concentration (wt%), T is the absolute temperature (K), and t is the etching time (min). This is manufactured by performing an etching treatment for a time represented by the following expression) and removing quartz glass in an amount of 20 to 200 μm from the cut surface.

The etching rate of quartz glass by hydrofluoric acid depends on two conditions, hydrofluoric acid concentration and temperature.
Equation 3 between them

[0012]

[Formula 3] v = 7.2 × C ^2.4 × exp ｛−2.7 × 10 ⁴
/(8.31×T)｝ [where v represents an etching rate (μm / min)]. Have been experimentally found by the present inventors. Since there is a relationship of t = V / v between the etching rate, the etching time, and the etching amount, Expression 2 is derived, and by using this Expression 2, any etching conditions (hydrofluoric acid concentration, temperature, etching amount) can be obtained. Can be determined.

FIG. 2 shows an example of the change in the surface roughness of the groove cut surface due to the above-mentioned hydrofluoric acid etching. The surface roughness rapidly increases immediately after the etching process, reaches a maximum value, and then gradually decreases. Eventually it reaches a certain value. After the surface roughness reaches the maximum, the turtle structure appears, but the etching amount of quartz glass up to that time depends on the cutting conditions such as the type of blade used for cutting, the peripheral speed of the blade, the feed speed,
It is necessary to increase the etching amount as the initial surface after cutting is rough. Under the cutting conditions of the present invention, the etching amount is 2
It is good to set it in the range of 0 to 200 μm. If the etching amount is less than 20 μm, no turtle shell structure appears, and even if the amount of quartz glass exceeding 200 μm is removed, there is no change in the surface structure, resulting in useless etching, which is not preferable.

The concentration of hydrofluoric acid used in the production method of the present invention is preferably higher because the etching time is shorter. However, in general, those having a concentration of 70% by weight or less are available, and therefore, 70% by weight or less. Use hydrofluoric acid. However, if the hydrofluoric acid concentration is less than 20 wt%, it takes too much time for etching, which is not preferable. Therefore, the hydrofluoric acid concentration is set in the range of 20 to 70 wt%. Further, it is not necessary to control the temperature at the time of etching.
The range of ３２323 K is preferred. If the temperature is lower than 273K, it takes too much time for etching, and if it exceeds 323K, the etching solution is liable to evaporate and volatilize, which is not preferable in handling.

Since high precision is required for grooving of the quartz glass jig for heat treatment of a silicon wafer of the present invention,
A diamond blade is used. Specific examples of the diamond blade include a metal-bonded diamond blade, a resin-bonded diamond blade and a vitrified bond-type diamond blade. Is also not preferred because of poor durability. When using the diamond blade specifically, in order to obtain a high-precision and high-quality cut surface, in the case of a resin-bonded diamond blade, the particle size is # 14.
0 to 230, bonding degree: N to R, concentration degree: 75 to 125, and in the case of a metal bond diamond blade, particle size: # 140 to 230, bonding degree: N, concentration degree:
In the case of a vitrified diamond blade having a particle size of 30 to 75, a particle size of # 140 to 230 and a concentration of 75 to 125 are suitable. In addition, in the groove cutting by the diamond blade, since the groove width is enlarged by the etching process, it is preferable to cut the groove width smaller than a finished dimension of the groove width by a predetermined etching amount.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to specific examples, but the present invention is not limited thereto.

[0017]

EXAMPLES Examples 1 to 3 A wafer boat was prepared using a bar having a diameter of 12 mm, and a diamond blade having the specifications shown in Table 1 was used at a peripheral speed of 1300 m / min and a feed speed of 60 mm / min.
A wafer boat having a groove depth of 6 mm, a groove width of 3 mm, and a groove pitch of 3 mm was prepared. Next, each wafer boat was processed under the etching conditions shown in Table 1. FIG. 3 shows a scanning electron micrograph of the grooved surface of the wafer boat subjected to the processing of Example 1. As is clear from the photograph, it can be seen that there are protrusions having a turtle shell structure. Observe the surface shape of the grooved surface of the obtained quartz glass jig for heat treatment of silicon wafer, and observe the surface roughness and transition metal foreign matter.
The number was measured. Table 1 shows the results.

Comparative Example 1 A wafer boat similar to that of the example was cut with an electrodeposited diamond blade, and the same etching treatment as that of the example 1 was performed. Table 1 shows the results.

Comparative Example 2 A wafer boat similar to that in the example was cut with a resin-bonded diamond blade, and then subjected to an etching process using a conventionally used low-concentration hydrofluoric acid solution. Table 1 shows the results.

The numerical values in the examples and comparative examples are values obtained by the following measuring methods. (I) Surface roughness Surface roughness meter (Surfcom300 manufactured by Tokyo Seimitsu Co., Ltd.)
Measured values of _Rmax and _Ra (center line average roughness) according to B).

(Ii) Average distance between protrusions The number of protrusions per unit length is measured from the data of the roughness profile by the surface roughness meter of (i) and calculated.

(Iii) Number and identification of transition metal foreign matter Scanning electron microscope (JSM5800L manufactured by JEOL Ltd.)
V) and energy dispersive X-ray analysis (Oxford.
(Link ISIS L2001-S / S-ATM) to measure the number of transition metal foreign substances and identify the elemental composition of the transition metal foreign substances.

[0023]

[Table 1] Note) Resin: Resin bond type diamond blade, Vitri: Vitrified bond type diamond blade,
Metal: Metal bond type diamond blade, electrodeposition:
Electroplated diamond blade.

<Evaluation> As is clear from Table 1, the grooved surfaces of Examples 1 to 3 have increased surface roughness, but have a turtle shell structure, no fine irregularities or microcracks, and no particles are generated. In addition, there is almost no transition metal foreign matter,
High purity.

On the other hand, the grooved surface of Comparative Example 1 has a tortoiseshell structure, is free from fine irregularities and microcracks, has no particles, and has almost no transition metal foreign matter. Since the surface roughness was large, the silicon wafer was damaged.

Further, since the etching treatment with hydrofluoric acid was not sufficient on the grooved surface of Comparative Example 2, no turtle shell structure appeared on the grooved surface, and transition metal foreign matter was not completely removed.

[0027]

The quartz glass jig for heat-treating a silicon wafer according to the present invention has a high-purity with a grooved surface having a turtle-shape structure, no fine irregularities or microcracks, no particles, and no transition metal foreign matter remaining. This is a quartz glass jig having a cutting surface. Therefore, in the heat treatment of the silicon wafer using the quartz glass jig, there is no damage or contamination of the silicon wafer, and a high-quality silicon wafer can be manufactured with high yield. The quartz glass jig for silicon wafer heat treatment can be easily manufactured by processing the jig obtained by the conventional manufacturing method under specific etching conditions,
Its industrial value is high.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a groove cut surface of a quartz glass jig for heat treatment of a silicon wafer.

FIG. 2 is a graph showing a change in surface roughness of a grooved surface due to HF etching.

FIG. 3 is a scanning electron micrograph of a grooved surface of a quartz glass jig for heat treatment of a silicon wafer of Example 1.

Claims (5)

[Claims] 1. A quartz glass jig for heat-treating a silicon wafer having a grooving surface formed by cutting, wherein the grooving surface has a tortoiseshell structure, and the surface roughness of the entire grooving surface is a center line average roughness ( _Ra). A quartz glass jig for heat treating silicon wafers having a high-purity groove cut surface, wherein the jig has a thickness of 0.5 to 5 μm. 2. The average spacing between protrusions of the turtle shell structure is 20 to 20.
0 μm, the maximum height (R _max ) of the projection with respect to the concave portion is 2
2. The quartz glass jig for heat treatment of a silicon wafer having a high-purity grooved surface according to claim 1, wherein the jig is 20 μm. 3. A quartz glass jig for heat-treating a silicon wafer is cut, and then a hydrofluoric acid of 20 to 70% by weight is used at a temperature (T) of 273 to 323K and an equation 1 t = V / [ 7.2 × C ^2.4 × exp ｛−2.7
× 10 ⁴ /(8.31×T)}] (where V is the etching amount (μm), C is the hydrofluoric acid concentration (wt%), T is the absolute temperature (K), and t is the etching time (min). A method for producing a quartz glass jig for heat treatment of a silicon wafer, wherein an etching treatment is performed for a time represented by the formula (1), quartz glass is removed from the cut surface by 20 to 200 μm, and the groove cut surface has a turret structure. 4. The method for producing a quartz glass jig for heat treatment of a silicon wafer having a high-purity groove cut surface according to claim 3, wherein the cutting is performed by a diamond blade. 5. The heat treatment of a silicon wafer having a high-purity grooved surface according to claim 4, wherein the diamond blade is any one of a metal bond type diamond blade, a resin bond type diamond blade and a vitrified bond type diamond blade. Method of manufacturing quartz glass jigs.