Preparation method for deep trench isolation channel

Abstract

The invention discloses a preparation method for a deep trench isolation channel, aiming at the requirements of mechanical connection but electrical insulation in MEMS (Micro Electro Mechanical System) technology. The method comprises the following steps of: polishing a silicon wafer; photo-etching; performing DRIE (Deep Reactive Ion Etching) to form a deep channel 2, wherein the deep channel 2 has an inverted isosceles trapezoid shape, and an included angle theta between a side wall of the channel and vertical direction is greater than or equal to 1 degree and is less than or equal to 5 degrees; cleaning with oxygen; generating a silicon dioxide insulating layer 3 on the surface of the side wall of the deep channel 2 and the surface of the silicon wafer; and filling a polycrystalline silicon layer 4. The preparation method has the beneficial effects that: the silicon wafer is etched into the inverted trapezoidal deep trench isolation channel by using DRIE; Notching phenomenon in isotropic etching is avoided; and the filling of the bottom of the deep channel can be guaranteed. Since the deep channel has the inverted trapezoid shape, an open part is still larger than the middle part of the channel, and the situation of a gap caused by blockage of the open part is also avoided during deposition of polycrystalline silicon. Since the included angle between the side wall of an oblique channel and the vertical direction is smaller, insulating characteristic and mechanical strength of the isolation channel are not influenced, and packaging air-tightness and insulation requirement can be met.

Description

[0001] Field: [0002] The present invention generally relates to microelectromechanical systems (MEMS) and micromachining techniques. Background technique: [0003] In MEMS technology, there are often scenarios that require mechanical connection but electrical isolation. The existing method is realized by a deep trench isolation trench with a rectangular cross section, and the deep trench isolation trench is filled with a sandwich material with silicon dioxide on both sides and polysilicon in the middle. However, since the etching ions will bounce back from the bottom surface during the etching process, resulting in secondary etching of the sidewall, it is easy to cause the opening to be smaller than the middle part of the trench. Experimental verification shows that this cross-section is a rectangular deep trench isolation. Grooves are prone to gaps during preparation. The preparation method of this deep trench isolation groove is widely used, can be used in the encapsulat...

AI Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is: in order to solve the problems such as gaps and horseshoe phenomenon in LPCVD polysilicon in the prior art, the present invention proposes a new method for preparing deep trench isolation grooves

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