Preparation method of metal bonding pad in through hole of SOI sheet

Abstract

The invention provides a preparation method of a bonding pad in a through hole in MEMS (Micro-electromechanical System) wafer-level vacuum package. According to the preparation method, a special structure of the through hole in an SOI substrate is utilized, and the bonding pad in the through hole is prepared by adopting an electrochemical corrosion method, so that the problem of electrical short circuit of back metal in a base layer of the SOI sheet is effectively solved, and the preparation method has the advantages of being low in cost, suitable for volume production and the like.

Description

technical field [0001] The invention relates to the technical field of micromachining, in particular to a method for manufacturing a metal pad in a through hole of an SOI chip in a MEMS wafer-level vacuum package. Background technique [0002] Micro-Electro-Mechanical System (MEMS) is a high-tech cutting-edge discipline developed on the basis of integrating various micro-processing technologies and applying the latest achievements of modern information technology. It has a wide range of applications in almost all fields that people come into contact with. prospect. [0003] Vacuum packaging plays a vital role in MEMS micro-sensors. On the one hand, it can protect the movable parts in the micro-sensor, making it not easy to damage; on the other hand, it can isolate the external environment (such as gas, humidity, dust, etc.), making Gyroscopes, accelerometers, pressure sensors, RF switches, etc. will work fine. Vacuum packaging can be divided into shell-level and wafer-leve...

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Problems solved by technology

[0013] The spin-coated photoresist process is a commonly used method, but considering that the SOI base layer has been opened, the spin-coated photoresist is difficult to survive on the highly patterned surface, and the photoresist is too thick at the bottom of the pit. It cannot be removed by exposure, so patterned transfer cannot be realized, and the required pads cannot be made

The three-dimensional glue spraying process can not be limited by the highly patterned surface, but this process requires special dry film deposition equipment, and the processing cost is relatively high

Moreover, photolithography on the patterned surface belongs to proximity exposure, and the problem of light diffraction caused by it also affects the accuracy of photolithography to a certain extent.

[0014] Hard mask technology can pattern metal thin films on highly structured wafers, but its poor alignment accuracy limits its use

At the same time, due to the non-directionality of the sputtering process, usually after sputtering, the sidewall of the via hole is connected to the SOI device layer, resulting in a short circuit of the device

[0015] Although the use of SOI chips with via holes to realize the lead interconnection of silicon glass anodic bonding vacuum packaging has the advantages of simple processing, low packaging stress, and good sealing, but the production of pads in this lead method is not easy and feasible. The solution requires expensive special equipment, which limits its use to a certain extent, and is not conducive to reducing costs

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