Wafer boat with interference fit wafer supports

Inactive Publication Date: 2005-07-07
SAINT GOBAIN CERAMICS & PLASTICS INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0024] In accordance with one or more embodiments, the present invention provides a method of fabricating a ceramic article. The method can comprise forming a molded component comprising a ceramic powder comprising silicon carbide and sintering the molded component at about 2200° to about 2500° C. to produce a sintered component having an impurity component concentration of less than about 400 ppm.
[0025] In accordance with one or more embodiments, the present invention provides an article. The article can comprise a ceramic material selected from the group consisting of silicon carbide, silicon nitride, and aluminum oxide. The ceramic material can have a pore size of at least about 15 μm and an active impurity c

Problems solved by technology

The use of larger diameter wafers presents several major challenges to semiconductor manufactures.
Moreover, the larger wafers are also heavier, requiring the use of automated wafer transport systems.
As the silicon wafers become bigger and heavier, the problem of preventing impurities and structural defects to the lattice, i.e., of maintaining very high crystalline perfection, becomes even more critical.
Two such structural defects, which become especially problematic in 300 mm silicon wafers and larger, are “back side damage” and “slip” in the lattice structure.
Back side damage generally occurs when a wafer moves across a surface of a wafer support device, causing scratches in the back side of the wafer.
However, severe stress leads to slip, which is the plastic or permanent deformation in the crystal lattice, which remains when the stress is released.
Slip occurs when the elastic limit (or yield strength) of the silicon is exceeded and the lattice becomes permanently misaligned.
Therefore slip, whether induced by thermal or mechanical stress, becomes especially problematic at process temperatures above 720 degrees Celsius.
Therefore, during high temperature thermal processing, the center of the wafers tends to sag, promoting slip in the crystal lattice of the wafer.
However, manufacturing this geometry is cumbersome due to the precise machining required and the inherently low yield rates.
Also the added length of the cantilevered arms imposes a large moment force at the single support point where the arm attaches to the rod body, unduly increasing the probability of failure or breakage.
Moreover, because the arms provide support at only three or four small discrete areas on the wafers, the possibility of back side damage is enhanced for the heavier wafers.
However, each ring typically costs in the range of one thousand to two thousand dollars to manufacture, greatly adding to the cost of the boat.
This makes it difficult for conventional transfer equipment to get between the rings and wafers in order to remove the wafers from the slots.
Additionally, the enclosed design impedes the free flow of gasses that are often important to the processing of the wafers.
That is, the ceramic rings can rub against the wafer support arms during processing or handling, and frictionally rub off microscopic particles which can damage the semiconductor circuitry of the wafers.

Method used

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  • Wafer boat with interference fit wafer supports
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  • Wafer boat with interference fit wafer supports

Examples

Experimental program
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example 1

[0095] Machined samples were heated at different sintering temperatures, from about 1800° C. to about 2500° C., to determine preferable conditions for obtaining a fully recrystallized structure. The pore size monotonically increased from less than about 0.25 μm, as observed in the unfired sample, to greater than about 15 μm, as observed in the sample sintered at about 2400° C., as shown in FIG. 10.

[0096] Comparative results from two different sintering conditions: about 1950° C. at about 0.9 torr for about two hours and about 2475° C. at about 760 torr for about two hours, as shown in FIGS. 11 and 12. Clear differences were observed about the extent of recrystallization between the two sintering conditions. The sample sintered at about 1950° C. recrystallized to a pore size of about 8.8 μm (median pore size) while the sample sintered at about 2475° C. recrystallized to a pore size of about 25.8 μm (median pore size). Copies of photomicrographs of polished cross-sections from the sa...

example 2

[0098] Machined samples were heated at different vacuum levels, from about 0.6 to about 600 torr, and sintered at various temperatures, from about 1650° C. to about 2000° C., to determine preferable processing conditions. A vacuum level below about 10 torr, e.g. about 6 torr, appears to provide good impurity removal during sintering as shown in Table 1.

TABLE 1Impurity concentration at various processing conditions.Temperature (° C.)Pressure (torr)Fe (ppm)Ni (ppm)1850620.318500.60.20.3185060035785200060.20.320000.60.20.320006000.25

[0099] Thus, in addition to the high sintering temperature, between about 2200° and about 2500° C., as described in Example 1, the techniques of the present invention can be conducted utilizing vacuum conditions, e.g., less than about 6 torr pressure, to promote volatilization of impurities and provide a high purity ceramic article, such as a wafer boat suitable for use during annealing processes of silicon semiconductor wafers.

[0100] Thus, the process o...

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Abstract

A wafer boat including a base plate, a top plate, a plurality of support rods, and a plurality of wafer supports. The support rods are disposed about a perimeter of the base plate and extend between the base plate and the top plate, each support rod including a plurality slots that define a plurality of teeth. The wafer supports are received in a corresponding slot of each of the plurality of support rods and have a continuous open shape that includes a pair of leg sections that form an interference fit with at least two of the support rods. The base plate, the top plate, the support rods, and / or the wafer supports may be prepared by molding ceramic powder such as silicon carbide, sintering to vaporize any active impurity components, washing to dissolve any remaining active impurity components with an acid solution, and oxidizing to remove any residual active impurity components.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to semiconductor manufacturing. More specifically, the present invention relates to semiconductor wafer carriers or boats having a plurality of wafer supports that form an interference fit with a body of the wafer carrier or boat. [0003] 2. Discussion of the Related Art [0004] Although other materials may be used, e.g., Silicon-Germanium (SiGe) or Gallium Arsenide (GaAs), Silicon (Si) is presently the most important semiconductor for the electronics industry. Very Large Scale Integrated (VLSI) circuit technology (i.e., up to about 100,000 devices per chip), and Ultra Large Scale Integrated (ULSI) circuit technology (i.e., more than 100,000 and in some cases exceeding one billion devices per chip) are based almost entirely on silicon. [0005] The fabrication of VLSI and ULSI circuits generally takes place on silicon substrates that possess very high crystalline perfection or purity. That ...

Claims

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Application Information

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IPC IPC(8): A47G19/08H01L21/673
CPCH01L21/67303H01L21/67309H01L21/67306
InventorBUCKLEY, RICHARD F.NARENDAR, YESHWANTH
OwnerSAINT GOBAIN CERAMICS & PLASTICS INC