A processing method for a four-mass silicon micro-electromechanical gyro structure

Abstract

The invention relates to a processing method, and especially relates to a processing method of a silicon micro-electromechanical gyro mechanism having different height comb structures and needing wafer level packaging. The method comprises the following steps: 1, processing a lower sealing cap; 2, lower sealing cap and sensitive structure bonding: carrying out structure processing of the upper surface of a sensitive structure, and bonding the lower sealing cap with the sensitive structure; 3, sensitive structure processing: removing the support layer and the insulation layer of the sensitive structure, carrying out silicon nitride mask imaging, growing silica, carrying out mask imaging of the sensitive structure, etching a fixed comb structure, and etching a mobile comb structure; 4, upper sealing cab processing: carrying out fairlead processing of the upper sealing cap, and carrying out mass block processing of the upper sealing cap; 5, bonding the sensitive structure with the upper sealing cap; and 6, metalizing. The method is in favor of guaranteeing the line quality and improving the sidewall verticality of the comb structures, solves residual stress caused by the difference of thermal expansion coefficients of different materials, improves the technological compatibility, reduces the processing operation, and reduces the technological cost.

Description

technical field [0001] The invention relates to a processing method for a four-mass silicon micro-electromechanical gyro structure, in particular to a processing method for a silicon micro-electromechanical gyro structure with unequal-height comb structures and wafer-level packaging. Background technique [0002] Research on MEMS gyroscopes began in the 1980s. In 1985, the Drape laboratory first began to develop micro-electromechanical gyroscopes, and its performance changed from a drift of 4000° / h in 1994 to a drift of better than 10° / h in 2000. In 2002, the Jet Laboratory of the United States developed a silicon micro-gyroscope for aircraft with a performance index of 1° / h. At present, it is developing towards an accuracy of 0.1° / h or even higher. Due to the advantages of small size, light weight, high reliability, low power consumption, mass production and large measurement range, micro gyroscopes are used in guided artillery shells, small satellites and spacecraft, aut...

AI Technical Summary

Problems solved by technology

At present, a single layer mask (SiO 2 ) process scheme and metal (Al) and dielectric mask (Si 3 N 4 ) double-mask process scheme, but when the single-layer mask process scheme processes unequal height structures, it is difficult to accurately control the thickness of each mask etching and it is easy to cause large dimensional errors after multiple etchings, while metal and When processing unequal height structures in the double-layer mask process scheme of dielectric mask, it is difficult to guarantee the dimensional accuracy and line quality of the mask pattern due to the need to use wet etching when patterning the metal mask, which in turn affects the dimensional accuracy of the microstructure and sidewall verticality; (2) low-stress wafer-level packaging

At present, silicon micro-electromechanical gyroscopes are often packaged at the wafer level by glass (Corning7740)-silicon anode bonding, but during the bonding process, the thermal expansion coefficient of Corning7740 is almost constant from room temperature to 450 °C at 3.3×10 -6 / °C, while the thermal expansion coefficient of silicon in this temperature range is 2.5×10 -6 / °C increased to 4×10 -6 / °C, this will cause a large residual stress at the glass-silicon bonding interface, which will seriously affect the performance indicators of the MEMS gyroscope; (3) deep lead hole metallization process

In the traditional process, the lift-off process is often used to metallize the microstructure. However, due to the deep lead hole depth in the above structure, the photoresist is accumulated in the deep lead hole during the coating process, making it difficult to develop cleanly. , so cannot be metallized by lift-off process

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