Method for producing discs from a cylindrical rod made of a semiconductor material

Patent metadata

Field	Value
Publication number	US-2024234125-A9
Application number	US-202218546434-A
Country	US
Kind code	A9
Filing date	Feb 4, 2022
Priority date	Feb 18, 2021
Publication date	Jul 11, 2024
Grant date	—

Abstract

A method produces wafers from a cylindrical ingot of semiconductor material having an axis and an indexing notch in an outer surface of the cylindrical ingot and parallel to the axis. The method includes, in the order specified: (a) simultaneous removal of a multiplicity of sliced wafers from the cylindrical ingot by multi-wire slicing in the presence of a cutting agent; (b) etching of the sliced wafers with an alkaline etchant in an etching bath at a temperature of 20° C. to 50° C. and for a residence time, such that the material removed from each of the sliced wafers is less than 5/1000 of an initial wafer thickness; and (c) grinding of the etched wafers by simultaneous double-disk grinding using an annular abrasive covering.

First claim

1 . A method for producing wafers from a cylindrical ingot of semiconductor material having an axis and an indexing notch in an outer surface of the cylindrical ingot and parallel to the axis, the method comprising, in the order specified:
(a) simultaneous removal of a multiplicity of sliced wafers from the cylindrical ingot by multi-wire slicing in the presence of a cutting agent; (b) etching of the sliced wafers with an alkaline etchant in an etching bath at a temperature of 20° C. to 50° C. and for a residence time, such that the material removed from each of the sliced wafers is less than 5/1000 of an initial wafer thickness; and (c) grinding of the etched wafers by simultaneous double-disk grinding using an annular abrasive covering.

2 . The method as claimed in claim 1 , wherein the alkaline etchant is a hydroxide of an alkali metal or of a nonmetallic cation that is dissolved in the etching bath.

3 . The method as claimed in claim 1 , wherein the alkaline etchant comprises potassium hydroxide (KOH), sodium hydroxide (NaOH), ammonium hydroxide (NH 4 OH) or tetramethylammonium hydroxide (TMAH, N(CH 3 ) 4 OH), or a mixture of at least two of these compounds.

4 . The method as claimed in claim 1 , wherein the residence time of the wafers is 0.5 min to 15 min.

5 . The method as claimed in claim 1 , wherein the concentration of the alkaline etchant in the etching bath is 0.5 to 10 wt % and the material removed per wafer is not more than 4.5 μm.

6 . The method as claimed in claim 4 , wherein the temperature is 25° C. to 40° C., the residence time is 1 min to 6 min, and the concentration of the alkaline etchant in the etching bath is 2 wt % to 6 wt %.

7 . The method as claimed in claim 1 , wherein the wire slicing is performed as slurry wire slicing, the wire is a hypereutectoid steel wire having a carbon content of 0.8 wt % to 1 wt % and a diameter of 50 lam to 175 μm, and the cutting agent is a slurry of silicon carbide (SiC) having a particle size of 7 μm to 13 μm in glycol.

8 . The method as claimed in claim 7 , wherein the wire is structured and bears a multiplicity of indentations and protrusions in directions perpendicular to a wire axis.

9 . The method as claimed in claim 1 , wherein the wire slicing is performed as diamond wire slicing, the wire is a hypereutectoid steel wire having a carbon content of 0.8 wt % to 1 wt % and having a diameter of 50 lam to 120 μm, the cutting agent comprises diamonds with a particle size of 4 μm and 20 μm, and the diamonds are anchored in the surface of the wire by moans of electroplate binding with nickel, by means of synthetic resin binding or mechanically.

10 . The method as claimed in claim 1 , wherein the wire is moved in a multiplicity of pairs of directional reversals around wire-guiding rollers, a pair of directional reversals comprises in each case a moving in a first longitudinal wire direction by a first length and a subsequent moving in a second direction, exactly opposite to the first longitudinal wire direction, by a second length, and the first length is chosen to be greater than the second length.

11 . The method as claimed in claim 1 , wherein the annular abrasive covering comprises diamond which is ceramically bonded and has a particle size of 0.5 μm to 12 μm.

12 . The method as claimed in claim 11 , wherein the particle size is 1.5 μm to 6 μm

Assignees

• Siltronic Ag

Inventors

• Pietsch Georg
• Junge Joachim

Classifications

• H10P90/126 Primary

  by chemical etching · CPC title

• B28D7/02

  for removing or laying dust, e.g. by spraying liquids; for cooling work · CPC title

• B28D5/045

  by cutting with wires or closed-loop blades (B28D5/042 takes precedence) · CPC title

• B24D7/06

  with inserted abrasive blocks, e.g. segmental · CPC title

• B24B7/228

  for grinding thin, brittle parts, e.g. semiconductors, wafers (grinding edges of thin, brittle parts B24B9/065) · CPC title