Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02002—Preparing wafers
  • H01L21/02005—Preparing bulk and homogeneous wafers
  • H01L21/02008—Multistep processes
  • H01L21/0201—Specific process step
  • H01L21/02024—Mirror polishing

Definitions

• Disks made of semiconductor materials which are in articular demand as substrata for the opitaxial grow- .-r.g process (a process that is becoming more and more important in the manufacture of semiconductors) have been produced by a mechanical polishing process, using abrasives like corundum powders, zirconium dioxide, cerium oxide, diamonds, or silicon carbide. Since mechanical polishing has always caused a more or less severe destruction of the surface layer, which disturbes the subsequent epitaxial growing process, the disks must undergo a chemical cauterization or etching before they can be further processed. And this, of course, impairs the oft required smoothness of the surfaces.
• silicic acid brine and silicic acid gels as polishing substances. These can be produced, for example, by acidifying a silicate solution or stirring in water the silicic acid formed by the burning of silicon tetrachloride. Unlike the above-mentioned crystalline polishing powders, the silicic acid brine and gels are amorphous, i.e. they show no crystalline reflex, under X-ray examination. Their polishing effect, too, is very slight.
• Salts of metals of the second and third Group and Subgroup of the Periodic System, as well as silicateforming salts of heavy metals, for instance, zirconium, iron, lead, nickel, cobalt, are suitable as silicateforming metallic salts.
• silicateforming metallic salts for instance, zirconium, iron, lead, nickel, cobalt
• soluble salts of magnes sium, calcium, strontium, barium, zinc or aluminum are suitable as silicateforming metallic salts.
• silicic acid solutions and their salts we mean solutions having anions that are made up of one or more silicon atoms, that are coordinately surrounded by oxygen atoms, and that the oxygen atoms may have attached thereto hydrogen or organic groups; for instance SiO H siof HSiOf', H3SIO41, Shoe HSI2O6 3, HgSIzOs K H3SI20 Precipitation of alkali silicate solutions, for instance sodium silicate solutions, have turned out here to be of particular value.
• Silicic acid esters for example, may be used as derivatives of silicic acid, after they have been partly or completely hydrolyzed for instance, partly hydrolyzed silicic acid tetra-n-butyl ester.
• Silicon fluorides which are difficultly soluble are used as silicon fluorides, after they have been precipitated by the addition of silicon fluoride-forming metallic compounds or their solutions into solutions of fluosilicic acid, their salts or derivatives.
• Salts, oxides or hydroxides of the metals of the first, second, third Groups of the Periodic System, particularly sodium, potassium, magnesium, calcium, barium, aluminum or zinc, are suitable here as silicon fluoride-forming metallic compounds. Solutions of the metal salts can be added individually as well as in mixtures.
• the polishing suspensions produced in accordance with the invention are characterized by a considerably higher rate of erosion without causing, however, any marked distruction of the crystalline structure on the burnished surfaces of the semiconductor disks.
• the polishing suspension applied in the polishing process may be used as either a neutral or an alkaline solution.
• polishing suspensions produced in accordance with the invention contain no oversize grains to cause scraping.
• polishing suspensions are manufactured by the simple process of pouring together solutions of raw materials previously filtered or decanted, any impurities caused by foreign bodies are easily eliminated.
• Round silicon disks of 32 mm diameter and 300 p. thick, obtained by sawing of a monocrystalline silicon rod, are fine-polished with corundum powder (grain size of 5 p.) abrading or wearing each side by 50 t. Every 12 disks are cemented on with bee's wax to a circular refined steel alloy supporting plate of 180 mm diameter, then applied to a rotary plate or dish (450 mm diameter) of a polishing machine covered with a polishing cloth, and finally loaded with 1.5 kg.
• the rotary dish is made to revolve at a speed of 90 rpm.
• the polishing suspension drips out onto the rotary dish at the rate of l to 2 drops per minute.
• the surface of the silicon disk is polished smooth and free of scratches and ready for epitaxial coating.
• EXAMPLE 3 Disks of a thickness of about 300 microns are sawed off a monocrystalline rod of gallium arsenide and finepolished with corundum powder of a grain size of about 2 to 3 microns. in this way about 30 microns were worn off each side.
• the polishing is performed as in Example 1, and an aqueous suspension of barium hexafluosilicate, manufactured as indicated below, is used as the polishing means:
• Process of finish polishing the surface of a semiconductor which comprises applying to said surface a polishing agent consisting essentially of a finely divided, freshly precipitated, difficultly soluble member of the group consisting of a metal silicate and a metal fluosilicate having a particle size range from about 20 to about 60 mp., said metal silicate being precipitated from an aqueous solution of an alkali silicate by addition of a water soluble compound of a metal of the group consisting of zirconium, iron, lead, nickel, cobalt, magnesium, calcium, strontium, barium, zinc and aluminum, and said metal fluosilicate being precipitated' from an aqueous solution of fluosilicic acid or an alkali fluosilicate by addition of a water soluble compound of a metal of the group consisting of sodium, potassium, calcium, barium and aluminum, said freshly precipitated difficultly soluble metal silicate or fluosilicate being in suspension in the aqueous reaction medium in which it is formed by precipitation.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

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Publications (1)

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Cited By (9)

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Citations (10)

• 1968
  • 1968-04-11 DE DE19681752163 patent/DE1752163A1/de active Granted
• 1969
  • 1969-04-10 GB GB08372/69A patent/GB1234894A/en not_active Expired
  • 1969-04-10 BE BE731353D patent/BE731353A/xx unknown
  • 1969-04-10 FR FR6911069A patent/FR2006054A1/fr not_active Withdrawn
  • 1969-04-11 CH CH556969A patent/CH505466A/de not_active IP Right Cessation
• 1972
  • 1972-08-28 US US284167A patent/US3877183A/en not_active Expired - Lifetime

Patent Citations (10)

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