JPH0653303A - Wafer fork and its manufacture method - Google Patents

Abstract

PURPOSE:To provide a wafer fork in which wafers are not almost contaminated due to impurities and a generation such as a warp, etc., is not almost caused, and which has a high strength and is made with high dimensional precision, and an effective manufacturing method. CONSTITUTION:In a wafer fork 1a for holding a semiconductor wafer and successively carrying it in a semiconductor manufacturing step, it is composed of a ceramic material of at least one of nitrided silicon (Si3N4) and SIALON (Si-Al-O-N), and comes into contact with the periphery of a held wafer 8 to form a marginal step 2 for holding the wafer 8 at a predetermined position and recesses 3 formed so as to oppose to each other without coming into contact with the wafer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer fork used for transferring and transporting semiconductor wafers in a semiconductor manufacturing process and a method of manufacturing the same, and in particular, the contamination of the wafer with impurities is small and the occurrence of warpage is small. The present invention relates to a wafer fork having high strength and high dimensional accuracy, and an efficient manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor wafer heat treatment process or a transfer line in a semiconductor manufacturing process, various holdings such as a wafer fork and a wafer chuck are sequentially carried in order to transfer and transfer a large number of semiconductor wafers sliced from single crystal silicon. The ingredients are used. The wafer fork is formed by forming a shallow recess into which a semiconductor wafer is fitted in the central portion of a flat plate-shaped body, while the wafer chuck is a holder that holds and holds the wafer by vacuum suction or electrostatic action.

The above-mentioned wafer fork is fixed to, for example, the tip of an arm of a transfer robot, is inserted through a minute gap into a gap between cartridges and carriers for accommodating wafers in multiple stages, and the wafer is picked up and held in a concave portion.
It is transported to the processing section of the next process.

Conventionally, as the above-mentioned wafer fork, one in which a stainless steel plate is cut into a predetermined shape and then the processed surface is coated with a fluororesin film or the like, or one in which the entire fork is made of quartz glass is mainly used.

[0005]

However, in a wafer fork having a stainless steel surface coated with a resin, the coating layer is broken in a short period of time, and impurities such as iron and alkali salts are likely to be transferred to the wafer side, which easily causes contamination. There is. Further, the stainless steel forming the main body is likely to be plastically deformed, which often makes it difficult to carry out a highly accurate conveying operation. On the other hand, since the stainless steel itself has a high toughness, if the transfer device itself malfunctions, the wafer fork may damage peripheral equipment such as an expensive robot and stop the manufacturing process.

On the other hand, a wafer fork made of quartz glass is less likely to be contaminated with impurities even when a coating layer is not formed, and is thermally stable, which is advantageous, while strength and rigidity are slightly low, so that it can be used repeatedly. There was a difficulty in using it as a structure that does. Especially in recent years
It is required to load more wafers in a cartridge or a carrier that stores a plurality of wafers, and the gap between adjacent wafers tends to be narrowed. Inevitably, a wafer fork inserted in the gap is also required. The demand for thinner products is increasing. However, as the device becomes thinner, its mechanical strength becomes smaller, so that it is likely to bend in a short period of time, resulting in a problem that the life is shortened.

As a means for solving the above problems, a purity of 9
A wafer fork formed by polishing an alumina (Al ₂ O ₃ ) sintered body of 9.0% or more is also used in part. This Al ₂ O ₃ wafer fork is manufactured by abutting the circular end surface of a cylindrical cup grindstone against the portion to be ground of the Al ₂ O ₃ sintered body to form a recess. That is, since the concave portion is formed into a curved surface shape that matches the curvature of the outer periphery of the wafer, a grinding method using a cup grindstone having a circular end face is generally adopted.

However, in the end surface grinding with the cup grindstone, since the grindstone is rotated in a surface contact state with the portion to be ground, the grinding resistance is likely to be excessive. As a result, after the grinding, the wafer fork is likely to be warped as a processing influence, and it becomes difficult to carry out a highly accurate wafer transfer operation. Further, the grinding of a sintered body, which is a hard and brittle material, has a low processing efficiency even if an expensive diamond grindstone is used, and inevitably causes an increase in manufacturing cost. Furthermore, since the impact force acting during the grinding process becomes large, defects such as cracks are likely to occur.

Further, in the Al ₂ O ₃ wafer fork, depending on the temperature condition and the atmosphere gas in the semiconductor manufacturing process,
There is a drawback that strength characteristics and durability are greatly different and uniform reliability cannot be obtained. On the other hand, as the degree of integration of semiconductor substrates has rapidly increased from 1 Mbit to 4 Mbit, the allowable limit of impurities for semiconductor wafers has become stricter, and conventional Al ₂ O ₃ wafer forks cannot support this. It is becoming.

The present invention has been made to solve the above-mentioned problems, and a wafer fork having less contamination of the wafer due to impurities, less warpage, high strength and high dimensional accuracy, and an efficient method thereof. It aims at providing a simple manufacturing method.

[0011]

In order to achieve the above object, a wafer fork according to the present invention is a wafer fork that holds and sequentially conveys semiconductor wafers in a semiconductor manufacturing process, and is made of silicon nitride (Si ₃ N ₄ ) And sialon (Si-Al-O-N) at least one of the ceramic materials, and a peripheral step portion that holds the wafer in a predetermined position by contacting with the peripheral portion of the wafer to be held, and a non-contact with the wafer. It is characterized in that concave portions formed so as to face each other are formed.

Further, in the method for manufacturing a wafer fork according to the present invention, when the semiconductor wafer is placed, the peripheral step portion which comes into contact with the peripheral portion of the wafer and holds the wafer at a predetermined position is not in contact with the wafer. A method of manufacturing a wafer fork having a concave portion is characterized in that a portion of the ceramic sintered body corresponding to the concave portion is ground by using a flat grindstone to form the concave portion.

Particularly, as a method of efficiently manufacturing a so-called near net shape wafer fork close to the shape of the final product, a ceramic molded body as a material of the wafer fork is laser-processed to precisely cut the contour of the wafer fork. Then, after that, the processed ceramic molded body may be degreased and sintered, and the obtained sintered body may be subjected to polishing to form the peripheral stepped portion and the concave portion.

The ceramic sintered body or the ceramic molded body constituting the wafer fork according to the present invention includes silicon nitride (Si ₃ N ₄ ) and sialon (Si).
At least one of --Al--O--N) is used. Both silicon nitride and sialon have higher strength values such as rigidity and toughness and environmental resistance characteristics than other ceramics,
Even when it is thinly formed like a wafer fork, it has sufficient durability and excellent thermal shock resistance, so that it can be used under all process conditions of the semiconductor manufacturing process.

In particular, the wafer fork formed of the above-mentioned silicon nitride sintered body can be used as it is, but by further forming a contamination preventing layer such as a fluororesin coating on the surface of the sintered body, the contamination of the wafer is more effective. Can be prevented.

The wafer fork is manufactured by the following procedure. First, for at least one of silicon nitride powder and sialon powder, Al ₂ as a sintering aid is added.
0.5 to 5% by weight of O ₃ powder and 0.5 to 5 of AlN powder
1% to 7% by weight of Y ₂ O ₃ powder and 0 to 3% by weight of TiO ₂ powder are added and uniformly mixed to prepare a raw material mixture. By pressure molding, a rectangular ceramic molded body having a uniform thickness can be obtained. Next, the obtained ceramic formed body is cut by laser processing to form a wafer fork formed body having a predetermined contour. Next, this wafer fork compact is degreased under predetermined conditions and further sintered, and the resulting wafer sintered compact is ground to form peripheral stepped portions and recesses, and then the surface is covered with a fluororesin coating or the like for preventing contamination. It is manufactured by applying.

The method of the present invention is characterized in that the ceramics compact is laser-cut at the stage of compacting to form a wafer fork compact having a predetermined shape.
The ceramic molded body is irradiated with a fine laser beam to perform cutting processing (green processing). That is, the laser light is finely focused by the condenser lens of the optical system and is applied to the position corresponding to the contour line of the wafer fork to be formed. The irradiated laser light heats the irradiated part of the molded body to a high temperature, and volatilizes the ceramic components and the like of the part in an instant. As a result, a fine wafer fork compact having high dimensional accuracy can be efficiently formed.

When cutting a ceramic molded body by laser processing in the stage of the molded body as described above, since the impact force due to cutting is extremely small, there is little effect on the processing, and even a soft molded body is not deformed or deformed. It is possible to efficiently form a fork molded body with high dimensional accuracy that is extremely close to the shape of the final product without the risk of cracking.

On the other hand, in the case of forming the peripheral stepped portion and the concave portion in the wafer sintered body, as shown in FIG. 3, a pair of peripheral stepped portions 2 are formed so as to face each other in the longitudinal direction of the wafer fork 1. , 2 is ground by a flat grindstone 4. The peripheral step portion 2 has a shape that contacts the peripheral portion of the wafer and holds the wafer in a predetermined position, and the recess 3 is ground deeper than the peripheral step portion 2 so as to face the wafer in a non-contact manner. It In order to prevent impurity contamination due to contact between the wafer and the wafer fork, the width of the peripheral step portion 2 is set as small as possible.

Then, of the entire recess 3 between the peripheral step portions 2 and 2, only the rectangular region R _{1 with} diagonal lines is ground with the flat grindstone 4, while the arcs at both ends of the peripheral step portion 2 and the recess 3 are formed. A region R ₂ including a curved portion such as a curved portion is ground with a cup grindstone. At this time, the grinding direction by the flat grindstone 4 is as shown in FIG.
It is advisable to set the direction perpendicular to the longitudinal direction of the wafer fork 1 as indicated by the arrow.

Since the flat grindstone comes into line contact with the surface to be ground of the fork body, the grinding resistance is small and the impact force due to grinding is smaller than that of the cup grindstone. In this way, since the region R ₁ occupying most of the portion to be ground of the wafer body is ground by the flat grindstone 4 having a small grinding resistance, the wafer fork as a finished product is less affected by the processing, and the warpage is effectively generated. Can be prevented.

[0022]

According to the wafer fork and the method of manufacturing the same having the above-mentioned structure, since the wafer fork is formed of silicon nitride or sialon having high rigidity and toughness, a wafer fork excellent in durability and thermal shock resistance can be obtained. Further, since the concave portion is formed so as to face the wafer in a non-contact state, impurity contamination due to the contact between the wafer fork and the wafer is significantly reduced.

Further, in this manufacturing method, since the concave portion is ground by using a flat grindstone having a small grinding resistance, a wafer fork having a small influence on the processing and less warpage can be obtained. Also, by laser cutting the ceramic molded body to form a wafer fork molded body with a predetermined shape, the impact force due to the cutting process is reduced, the processing influence is small, deformation and cracks do not occur, and dimensional accuracy and reliability It is possible to efficiently manufacture a wafer fork having a high height.

[0024]

The present invention will now be described more specifically with reference to the following examples and drawings.

Example 1 Al ₂ O ₃ powder was 4% by weight with respect to silicon nitride powder,
3% by weight of AlN powder and 5% by weight of Y ₂ O ₃ powder were uniformly added to prepare a mixed powder, which was press-molded with a die at a pressure of 800 kg / cm ² to obtain a ceramic having a thickness of 5 mm. The molded body is cut by machining to form a fork molded body, and the obtained fork molded body is degreased in a nitrogen gas atmosphere at a temperature of 700 ° C. for 3 hours, and subsequently in a nitrogen gas atmosphere at a temperature of 1750 ° C. Wafer fork sintered body 5 was prepared by sintering for a period of time.

With respect to the wafer fork sintered body thus obtained, as shown in FIG. 3, the portion to be ground (region R ₁ ) corresponding to the concave portion 3 was ground by the flat grindstone 4, and as shown in FIG. The recess 3 having a thickness of 0.9 mm is formed, and as shown in FIG.
The portion to be ground (region R ₂ ,
R ₂ ) is ground with a cup grindstone to form peripheral step portions 2 and 2 having a width of 4.25 mm and a depth of 0.8 mm as shown in FIG. 2, and finally 60 mm in length as shown in FIG. Width 192mm
A large number of wafer forks 1a according to Example 1 having a thickness of 1.8 mm were manufactured.

The resulting wafer fork 1a has a bending strength of 600 MPa and a fracture toughness value of 5 to 6 MPa /
m ^1/2 , Young's modulus of 290 GPa, thermal shock temperature difference of 60
The temperature is 0 ° C., and a conventional wafer fork made of quartz glass (Young's modulus 68 to 72 GPa) and a wafer fork made of stainless steel (tensile strength 520 MPa, Young's modulus 200)
It was found to be superior in strength and thermal shock resistance as compared with GPa).

Comparative Example 1 A 96% quartz glass plate was ground to produce a quartz glass wafer fork having the same size and shape as in Example 1 shown in FIGS. 1 and 2. The Young's modulus of the wafer fork according to Comparative Example 1 was 68 GPa, which was about 1/4 that of the fork of Example 1.

Comparative Example 2 A fork having the same size and shape as in Example 1 was manufactured by cutting a stainless steel (SUS304) plate, and a 20 μm thick fluororesin (Teflon) coating layer was formed on the surface of the fork. A conventional wafer fork according to Example 2 was prepared. The tensile strength of the SUS304 wafer fork according to Comparative Example 2 was as high as 520 MPa, but the Young's modulus was 200 GPa, which was significantly lower than that of Example 1.

Five wafer forks according to Example 1 and Comparative Examples 1 and 2 were fixed to the robot arm 6 of the wafer transfer device via fastening screws 7 as shown in FIGS. It was subjected to continuous operation for a month, and the occurrence status of failure trouble of the transfer device for transferring the semiconductor wafer 8 was recorded, and the results shown in Table 1 below were obtained.

[0031]

[Table 1]

As is clear from the results shown in Table 1, the wafer fork according to Example 1 has excellent durability and can prevent problems due to bending from occurring.

Example 2 The ceramic compact (thickness 5) prepared in Example 1
mm) was laser-cut to form a wafer fork compact, and a wafer fork having the same size and shape as in Example 1 was prepared by adjusting raw materials, molding, degreasing, and sintering under the same processing conditions as in Example 1. 10 sheets were manufactured.

The laser processing conditions are as follows.

That is, laser light emitted from a CO pulse laser (100 W class) is used, and the laser output is 60
W (high peak pulse), pulse repetition rate is 1KH
z, the cutting speed was set to 30 mm / min., and oxygen was used as an assist gas.

Comparative Example 3 The wafer fork sintered body prepared in Example 2 was degreased and sintered under the same conditions as in Example 2 except that a cup grindstone and other cutting tools were used to form the peripheral step and the recess. As a result, ten wafer forks having the same size and shape as in Example 2 were manufactured.

Then, with respect to each of the 10 wafer forks prepared in Example 2 and Comparative Example 3, the processing time until processing into a predetermined fork shape was measured, and the processing effect of the molded body processing portion was investigated. . The machining time is shown as a relative machining time ratio with the reference value 1 in Comparative Example 3. Regarding the influence of processing, each wafer fork was checked for a crack generation state by a fluorescent flaw detection method (PT), and one having a crack even at one place was determined as a defective product. The measurement results are shown in Table 2 below.

[0038]

[Table 2]

As is clear from the results shown in Table 2, in the case of Example 2 in which the molded body was cut by laser processing to form a fork molded body, a wafer fork having less processing influence and no defects such as cracks was used. It can be manufactured efficiently.

Next, regarding the difference in processing effect when the peripheral stepped portion and the recessed portion were formed by using a flat grindstone or a conventional cup grindstone at the stage of the wafer sintered body, Example 1 and Comparative Example 4 below are described. Controls were compared.

Comparative Example 4 The same size and shape as in Example 1 except that the flat grindstone was replaced with a cup grindstone 9 to form the peripheral step 2 and the recess 3 as shown in FIG. 10 wafer forks having 10 were manufactured.

Then, the wafer forks prepared in Example 1 and Comparative Example 4 were placed on a horizontal surface plate, and the maximum height (warpage) of the space formed between the surface of the surface plate and the fork surface was measured. It was measured. Then, the case of Comparative Example 1 was set as a reference value 1 and evaluated as a relative ratio of average values. The measurement results are shown in Table 3 below.

[0043]

[Table 3]

As is clear from the results shown in Table 3, according to the wafer fork of Example 1 which was ground by using the flat grindstone, the wafer fork produced by the machining effect was larger than that of Comparative Example 4 using the cup grindstone. The wafer fork has a small warp and high dimensional accuracy.

By adopting the wafer forks according to the first and second embodiments as described above, the reliability of wafer transfer and the operating rate of the semiconductor manufacturing apparatus are greatly improved, and the productivity of the semiconductor apparatus is greatly improved. You can Further, by adopting the manufacturing method of this embodiment, it becomes possible to efficiently manufacture a high-quality wafer fork with a high yield.

[0046]

As described above, according to the wafer fork and the method for manufacturing the same of the present invention, since it is formed of silicon nitride or sialon having high rigidity and toughness, it is excellent in durability and thermal shock resistance. A wafer fork is obtained. Further, since the concave portion is formed so as to face the wafer in a non-contact state, impurity contamination due to the contact between the wafer fork and the wafer is significantly reduced.

Further, in the manufacturing method of the present invention, since the concave portion is ground by using the flat grindstone having a small grinding resistance, a wafer fork having a small influence of the processing and less warpage can be obtained. In addition, by cutting the ceramic molded body with a laser to form a fork molded body with a predetermined shape, the impact force due to the cutting processing is reduced, the processing influence is less, and further, dimensional accuracy and reliability do not occur without deformation or cracks. It is possible to efficiently manufacture a wafer fork having a high height.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a wafer fork according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a plan view showing a state in which a recess is ground by using a flat grindstone in the method of the present invention.

FIG. 4 is a plan view showing a state in which a concave portion is ground by using a cup grindstone in a conventional manufacturing method. 1,1a Wafer fork 2 Peripheral step 3 Recess 4 Flat grindstone 5 Wafer fork sintered body 6 Robot arm 7 Fastening screw 8 Semiconductor wafer 9 Cup grindstone

Claims (5)

[Claims] 1. A wafer fork for sequentially holding and sequentially transporting semiconductor wafers in a semiconductor manufacturing process, which comprises silicon nitride (Si ₃ N ₄ ) and sialon (Si—Al—).
ON-N) made of at least one of the ceramic materials, and a peripheral step portion that holds the wafer in a predetermined position by contacting the peripheral portion of the wafer to be held, and a recess formed so as to face the wafer in a non-contact manner. A wafer fork characterized by being formed. 2. A method of manufacturing a wafer fork, wherein a peripheral step portion that contacts a peripheral portion of the wafer when the semiconductor wafer is placed and holds the wafer at a predetermined position, and a concave portion that is not in contact with the wafer are formed. 2. A method for manufacturing a wafer fork according to claim 1, wherein a portion corresponding to the recess of the ceramic sintered body is ground by using a flat grindstone to form the recess. 3. A method of manufacturing a wafer fork, comprising a peripheral stepped portion for holding a wafer in a predetermined position by contacting a peripheral portion of the wafer when the semiconductor wafer is placed thereon, and a concave portion not in contact with the wafer. In the method, a ceramic molded body as a material for a wafer fork is prepared, the obtained ceramic molded body is laser-processed to cut the contour portion of the wafer fork, and then the processed ceramic molded body is degreased and sintered. A method of manufacturing a wafer fork, comprising polishing the obtained sintered body to form a peripheral step and a recess. 4. The ceramic compact is made of silicon nitride (Si
_The method for manufacturing a wafer fork according to claim 3, wherein at least one of ₃ N ₄ ) and sialon (Si-Al-O-N) is used as a main raw material. 5. The method of manufacturing a wafer fork according to claim 3, wherein a pollution prevention layer such as a fluororesin coating is formed on the surface of the sintered body.