Semiconductor wafer, apparatus and process for producing the semiconductor wafer

Abstract

The invention relates to a process for producing a semiconductor wafer by double-side grinding of the semiconductor wafer, in which the semiconductor wafer is simultaneously ground on both sides, first by rough-grinding and then by finish-grinding, using a grinding tool. The semiconductor wafer, between the rough-grinding and the finish-grinding, remains positioned in the grinding machine, and the grinding tool continues to apply a substantially constant load during the transition from rough-grinding to finish-grinding. The invention also relates to an apparatus for carrying out the process and to a semiconductor wafer having a local flatness value on a front surface of less than 16 nm in a measurement window of 2 mm×2 mm area and of less than 40 nm in a measurement window of 10 mm×10 mm area.

1 . A process for planarizing a semiconductor wafer, comprising double-side grinding of the semiconductor wafer, in which the semiconductor wafer is simultaneously ground on both sides using a grinding tool, firstly by rough-grinding and then by finish-grinding, wherein the semiconductor wafer, between rough-grinding and finish-grinding, remains positioned in one grinding machine, and a substantially constant load is applied to the wafer during the transition from rough-grinding to finish-grinding.  
   
   
       2 . The process of  claim 1 , wherein the semiconductor wafer is ground between two double spindles, each spindle of the double spindles provided with a grinding wheel.  
   
   
       3 . The process of  claim 1 , wherein the semiconductor wafer is is polished after double-side grinding.  
   
   
       4 . The process of  claim 1 , wherein an edge of the wafer is profiled by edge-rounding before or after double-side grinding.  
   
   
       5 . The process of  claim 1 , wherein the wafer is treated with an etching medium after double-side grinding, so as to remove material from one or both sides of the wafer.  
   
   
       6 . The process of  claim 1 , wherein the wafer acquires a nonplanar intermediate form during rough-grinding and a planar final form during finish-grinding.  
   
   
       7 . The process of  claim 1 , wherein the wafer, after double-side grinding, is subjected to a material-removing subaperture process and is then polished.  
   
   
       8 . The process of  claim 1 , wherein the wafer, after double-side grinding, is subjected to material-removal polishing and finish polishing.  
   
   
       9 . The process of  claim 8 , wherein the material-removal polishing comprises double-side polishing or single-side polishing.  
   
   
       10 . The process as claimed in  claim 8 , wherein the material-removal polishing comprises polishing only a back surface of the wafer.  
   
   
       11 . The process of  claim 10 , wherein the material-removal polishing of the back surface of the wafer comprises a short polish which removes less than 5 μm of material from the back surface.  
   
   
       12 . The process of  claim 8 , wherein the wafer, prior to finish-polishing, is subjected to a material-removing subaperture process.  
   
   
       13 . The process of  claim 7 , wherein the wafer is machined using a magneto-rheological medium during the subaperture process.  
   
   
       14 . The process of  claim 12 , wherein the wafer is machined using a magneto-rheological medium during the subaperture process.  
   
   
       15 . The process of  claim 1 , wherein two opposed colinearly mounted rough grinding wheels contact opposing sides of said wafer, followed by contact with two opposed, colinearly mounted finish grinding wheels.  
   
   
       16 . The process of  claim 15 , wherein the colinearly mounted rough grinding wheels and colinearly mounted fine grinding wheels are respectively mounted on coaxial inner and outer spindles.  
   
   
       17 . An apparatus suitable for the double-side grinding of flat workpieces as described in  claim 1 , comprising two double spindles each having an inner sub-spindle and an outer sub-spindle, a device for loading and unloading a workpiece, and a workpiece holder which is positioned between the double spindles and by which the workpiece is held in a free-floating position during a grinding step, the sub-spindles positioned coaxially and bearing grinding wheels for grinding opposite sides of the workpiece, at least one sub-spindle per double spindle being axially displaceable independently of the other sub-spindle of the double spindle.  
   
   
       18 . The apparatus of  claim 17 , wherein the double spindles can be inclined from a position in which they are arranged co-linearly into a position in which they include an angle.  
   
   
       19 . The apparatus of  claim 17 , wherein the sub-spindles of the double spindles bear one rough-grinding wheel for rough- grinding and one finish-grinding wheel for finish-grinding of the workpiece per double spindle.  
   
   
       20 . A semiconductor wafer having a local flatness value on a front surface of less than 16 nm in a measurement window of 2 mm×2 mm area and of less than 40 nm in a measurement window of 10 mm×10 mm area.  
   
   
       21 . The semiconductor wafer as claimed in  claim 20 , which has a surface roughness of at most 200 Å RMS.  
   
   
       22 . The semiconductor wafer of  claim 20 , comprising silicon, a compound semiconductor, a strained silicon substrate, an SOI substrate, or an sSOI substrate.