The demand for ultra flat wafers has increased as the demand for slimmer and handier electronic devices has also increased. Thus, wafer manufacturers have developed various techniques to achieve the desired wafer flatness. If you’re wondering how ultra-flat wafers are made possible, here are some wafer thinning techniques used for ultra flat wafers:
Mechanical grinding is considered to be the most common technique because of its high thinning rate. It is a two-step process which involves coarse grinding and fine grinding. Fine grinding is crucial to get rid of the damage and surface irregularity brought about by the coarse grinding step. The damages produced by this technique is examined through x-ray topography and interference contrast microscopy. The leftover defects put force on the thinned wafers which results in broken wafers and additional bow, especially during handling and further processing. That is why additional thinning is crucial to remove the layer with flaws.
This technique is used to polish silicon wafers. CMP produces ultra-flat surfaces and low total thickness variation standards. The thinning rate of CMP is low compared to the mechanical grinding technique. CMP is practical for large quantity application for thick wafers.
This is considered to be a new method for wafer thinning. Traditional dry etch processing uses plasma which contains fluorine and chlorine but the new method involves Ar/ CF-containing plasma.
This common thinning technique involves etching one side of the wafer. Spin etching is one of the approaches that involves a thin surge of etching agent flowing systematically on top of the rotating wafer. For silicon, common etching agents are HF and HNO3.
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