In this work we demonstrate strain relief etching using an advanced chemical etching (ACE) process of the full wafer surface on commercial grade n-type 4H-SiC at production throughputs (μm’s/hr). The data shows >4x improvement of breakage strength in laser split wafers. Warp and bow of ground wafers is reduced to match wafers that have been CMP processed showing the potential of stronger, flatter wafers being available for chemical mechanical polishing.
Strain relief etching is a critical wet process technique use in high volume manufacturing of semiconductor substrates and device wafers. The goal of a strain relief etch is application dependent but can generally be considered for removal of warp/bow or improving mechanical strength by removing sub-surface damage thereby optimizing yields. Silicon Carbide (SiC) has a high chemical resistance which has blocked the manufacturing community from using strain relief etching to date.
Without an effective wet etch, the SiC substrate manufacturing community has resorted to expensive mechanical techniques for the polishing and thinning of wafers, which imparts significant stress and strain within the layer. Use of extensive mechanical techniques is also expensive and difficult to perform at volume where wafers are fragile early in the substrate manufacturing line. Research has explored mechanisms of wet etching for creating microstructures on 4H-SiC and trenches in 6H-SiC.