Opaque quartz glass product and method of manufacture

Details Opaque quartz glass product and method of manufacture Opaque quartz glass product and method of manufacture

1998-08-13

1999-11-16

Marcheschi, Michael

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

65 173, 65DIG8, 65 175, 65 174, 65120, C03C 306, C03C 1100, C03B 1908

Patent

active

059857790

DESCRIPTION:

BRIEF SUMMARY
Fused quartz products are widely used in the semiconductor industry to contain various high temperature processes important in the manufacture of microelectronic components. As the technology has advanced and defect levels have been reduced, there has developed a need for fused quartz glass of exceptional purity, particularly with respect to those metallic species which are potentially mobile at the temperatures of use, notably the alkali metals and copper. Such fused quartz products are achieved by fusing highly refined quartz grain, leading to bubble-free transparent quartz glass products of very high purity, as a consequence of which they exhibit very high transmissivity to both visible and infra-red radiation.
While this transparency presents no disadvantages for many of the fused quartz components used in semiconductor processing, there is a requirement for quartz glass products of comparable purity but which are substantially opaque to infra-red radiation. Such an opaque glass is required for the manufacture of thermal baffles, pedestals, flanges etc., in order to restrict transmission of infra-red radiation from the hot zone to other parts of the furnace, thus facilitating the achievement of uniform temperature in the hot zone, while limiting heat transmission to more delicate parts, e.g., the seals at the demountable joints of the apparatus.
The conventional way of reducing the transparency of vitreous silica, while maintaining its intrinsic purity is by incorporation of microbubbles, which reflect and diffuse the radiation. It is beneficial to have a large number of small bubbles, and desirable that the resultant opaque glass be of relatively high density, preferably above 1.9 g/cc (c.f. fused quartz 2.21 g/cc), and with closed pores, since this facilitates the welding of such articles, aids achievement of maximum cleanliness, ensures that the product is impervious to most gases, and minimises dimensional changes on flame polishing etc. The quartz glass manufacturer is thus confronted with the problem of generating at an acceptable cost, a glass product of high purity, incorporating a high concentration of microbubbles, with a well defined site distribution, the bubbles being preferably of small sizes and large bubbles being absent.
One solution to this problem employs amorphous or sol gel silica powders which are fused or sintered under conditions chosen to retain microbubbles, (e.g., Shinetsu Ref, 1, 2 & 3), Tosch Corporation (Ref. 4), and Nitto Chemical Industry (Ref. 5). These methods require careful control of sintering conditions, but this is not easy for large articles which by their very nature are relatively poor thermal conductors. A variation of this technique involves the incorporation of carbon or graphite particles in the silica gel, as reported by Shinetsu (Ref. 6).
Such methods, based on high surface area synthetic silica powders, lead to intrinsically high cost opaque glass products, and a more practical route to large ingots, flanges and other components would be to employ high purity quartz crystal grain as feedstock. Such high purity feedstocks already exist, and are used to manufacture the transparent fused quartz components which comprise the majority of the fused quartz equipment used in the semiconductor industry. The manufacture of specific components via slip-casting of fused quartz powders is well known, and has been used for many years to make articles which, depending on sintering conditions, can be opaque and of controlled porosity (Georgia Institute of Technology Refs. 7 & 8), or transparent and substantially bubble-free (Sherwood Refractories, Ref. 9). Such methods require the initial fusion of the grain, followed by grinding to fine power, suspension of the fine powder in a carrier medium, casting and sintering, and, while they offer the possibility of a near-net-shape product, without stringent precautions these processes give rise to undesirable pollution of the high purity feedstock material. Nevertheless they form the basis of a range of impervious opaque vitre

REFERENCES:
patent: 5114881 (1992-05-01), Kaneko et al.
patent: 5497004 (1996-03-01), Rudolph et al.

Affiliated with

Also associated with

Rating

Opaque quartz glass product and method of manufacture does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Opaque quartz glass product and method of manufacture, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Opaque quartz glass product and method of manufacture will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1324503