SOI pressure sensor piezoresistor, manufacturing method thereof and SOI pressure sensor

Abstract

The invention discloses an SOI pressure sensor piezoresistor and a manufacturing method thereof, and an SOI pressure sensor. The manufacturing method comprises the following steps: preparing an injection buffer protection layer, and preparing an injection barrier layer; performing P-type doping and annealing to form a P-type heavily doped region; and removing the non-P-type heavily doped region bywet etching to obtain the piezoresistor of the SOI pressure sensor. The piezoresistor of the SOI pressure sensor is prepared by the method. The SOI pressure sensor comprises a P-type heavily doped piezoresistor, and the P-type heavily doped piezoresistor is the piezoresistor of the SOI pressure sensor. The manufacturing method of the SOI pressure sensor piezoresistor has the advantages of being low in cost, high in etching precision, good in consistency, high in mass production efficiency, little in secondary pollution and the like, the surface of the manufactured piezoresistor is straight and smooth, and the piezoresistor can be widely used as a piezoresistor of an SOI pressure sensor and has high use value and good application prospects.

Description

technical field [0001] The invention belongs to the technical field of pressure sensor preparation, and relates to an SOI pressure sensor piezoresistor, a manufacturing method thereof, and an SOI pressure sensor. Background technique [0002] With the continuous development of aviation, aerospace, petrochemical and other fields, the demand for pressure sensors in these fields is increasing, and the demand for pressure measurement under special environmental conditions is also increasingly urgent. Therefore, pressure sensors such as: High temperature, high precision, high reliability, miniaturization and other requirements. [0003] Traditional bulk silicon pressure sensors use ordinary N-type bulk silicon wafers. Silicon piezoresistors are obtained by performing P-type doping in the piezoresistive and interconnection areas. The piezoresistive and substrate are separated by a PN junction without a separate silicon pressure sensor. Resistance to etching, but as the working te...

AI Technical Summary

Problems solved by technology

However, the existing etching equipment and etching process still have the following problems: (1) the etching equipment used in the existing MEMS is expensive, and the cost of improving the etching equipment is high; (2) the existing piezoresistive etching mainly uses Dry etching. In dry etching, the silicon in the area without photoresist protection is removed by means of ion beam bombardment, thereby forming piezoresistive. However, in the dry etching process, there is usually a certain curvature between the etched side and the bottom corner. The bottom and sides of the etched area are rough in a small area due to ion bombardment. From a microscopic point of view, the piezoresistive surface formed by ion beam etching has a local small island structure, and the local small island has a stress concentration phenomenon. The stress distribution is uneven, which makes the measurement accuracy of the sensor lower; further, in the dry etching process, the etching selection ratio between different media is usually small, such as the selection ratio of silicon and silicon dioxide is usually less than 5:1, in order to ensure that the top silicon film is etched clean, a certain amount of over-etching is usually required, and the silicon dioxide layer below will continue to be etched after the silicon etching in the faster-etched area during the over-etching process (BOX layer), as a result, the BOX layer is also etched to a certain thickness, and the increase in the distance between the piezoresistive and the strain diaphragm surface will lead to relaxation of the piezoresistive stress, so that the stress cannot be effectively transmitted to the piezoresistor, reducing the sensitivity of the sensor, resulting in The measurement accuracy of the sensor is reduced; in addition, when the photoresist is usually used as the etching barrier layer in the dry etching process, the photoresist is directly in contact with the silicon piezoresistive surface, and it is easy to introduce organic contamination, and these organic contamination The existence of is not conducive to the accurate measurement of stress by SOI pressure sensor

The existence of the above problems makes it difficult for existing SOI pressure sensors to meet the needs of aerospace and other fields for high temperature resistance and high precision.

In addition, with the development of technology, the size of silicon wafers corresponding to MEMS technology is also getting larger and larger. In the whole area of ​​larger silicon wafers, there are still certain technical challenges in ensuring good uniformity of ion beams. The uniformity of the beam cannot ensure the uniformity of the etching of the entire silicon wafer, so that the yield of the product cannot be guaranteed

In addition, the etching equipment used in the existing MEMS is expensive, and the cost of improving the process by improving the etching equipment is even higher

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