US 5,855,735 AGranted

Process for recovering substrates

AssigneeKobe Precision Inc.

InventorsSatoru Takada, Hidetoshi Inoue, Yoshihiro Hara

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Abstract

A process comprising removing surface layer materials from the wafer by inducing micro-fractures in the surface using a rotating pad and an abrasive slurry until all of the surface layer materials are removed; and chemically etching the surfaces of the wafer until all micro-fractures are removed therefrom. Edge materials are removed by abrasive tape. Wafer thickness reduction during recycling is less than 30 microns per cycle. One of the front and back surfaces of the wafer substrate is polished, any dots or grooves being on the non-polished side. The abrasive slurry contains more than 6 volume percent abrasive particles, and the abrasive slurry has a viscosity greater than about 2 cP at ambient temperature. The preferred pad comprises an organic polymer having a hardness greater than about 40 on the Shore D scale, optimally a polyurethane. The pressure of the pad against the wafer surface preferably does not exceed about 3 psi. Preferably, the chemical etching solution contains potassium hydroxide. An acidic solution can then be applied to the wafer surface. The reclaimed semiconductor wafer can be a silicon wafer having a matted side having etch pits which does not exceed 20 microns in width, an average roughness not exceeding 0.5 microns and a peak-to-valley roughness not exceeding 5 microns. Any laser markings from the original wafer are present on the matted side of the wafer.

Claims30

Dependent claims

A process for reclaiming a substrate wafer from a semiconductor wafer having at least one surface layer of foreign material such as film(s) or implant(s) applied on at least one of a front and a back surface of said substrate comprising the steps of:

(a) contacting at least one surface of a semiconductor wafer to be reclaimed with a controlled viscosity of abrasive suspended in a carrier fluid;
(b) applying a polymeric pad in a rotational motion generally parallel to said wafer foreign material surface layer while applying pressure normal to said surface layer, said pad having a hardness sufficient to produce impingement of granules of said abrasive onto said surface layer, but soft enough to attenuate the force of impingement to reduce the depth of subsurface damage in said substrate;
(c) controlling said pressure during said rotational motion of said pad on said wafer surface layer in an amount sufficient to induce microfractures in said substrate surface, to a depth of less than an average of about 10.mu., by said impingement of abrasive granules without introducing shaving of said substrate surface as evidenced by substantial numbers of substrate surface scratches or grooves;
and
(d) maintaining said pressure and said rotational motion for a time period sufficient to remove substantially all of said surface layer with minimum reduction of said substrate to produce a reclaimed substrate wafer of quality substantially equivalent to the substrate before said surface layer was applied thereto, wherein said wafer substrate thickness reduction is less than about 30.mu., as compared to the thickness of the substrate of the semiconductor wafer before reclaiming processing.

2 more elements

Dependencies are inferred from the claim text.