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A novel anti-shock silicon etching apparatus for solving diaphragm release problems
石莎莉, 陈大鹏, 欧毅, 景玉鹏, 徐秋霞, 叶甜春
2010 (6):
60701-060701.
doi: 10.1088/1674-1056/19/6/060701
摘要
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This paper presents a novel anti-shock bulk silicon
etching apparatus for solving a universal problem which occurs when
releasing the diaphragm (e.g.\ SiNx), that the diaphragm tends to be
probably cracked by the impact of heating-induced bubbles, the swirling of heating-induced
etchant, dithering of the hand and imbalanced etchant
pressure during the wafer being taken out. Through finite element
methods, the causes of the diaphragm cracking are analysed.
The impact of heating-induced bubbles could be the main factor which
results in the failure stress of the SiNx diaphragm and the rupture of
it. In order to reduce the four potential effects on the cracking of the released
diaphragm, an anti-shock bulk silicon etching apparatus is
proposed for using during the last etching process of the diaphragm
release. That is, the silicon wafer is first put into the regular
constant temperature etching apparatus or ultrasonic plus, and when
the residual bulk silicon to be etched reaches near the
interface of the silicon and SiNx diaphragm, within a distance of
50--80~\mu m (the exact value is determined by the thickness,
surface area and intensity of the released diaphragm), the wafer is
taken out carefully and put into the said anti-shock silicon etching
apparatus. The wafer's position is at the geometrical centre, also
the centre of gravity of the etching vessel. An etchant outlet is
built at the bottom. The wafer is etched continuously, and
at the same time the etchant flows out of the vessel. Optionally, two
symmetrically placed low-power heating resistors are put in the
anti-shock silicon etching apparatus to quicken the etching process.
The heating resistors' power should be low enough to avoid the
swirling of the heating-induced etchant and the impact of the heating-induced bubbles
on the released diaphragm. According to the experimental
results, the released SiNx diaphragm thus treated is unbroken, which
proves the practicality of the said anti-shock bulk silicon etching
apparatus.
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