TH112592A - Techniques and processes for creating a layer of cavity (Cavity) for surface-type silicon thin-sheet detectors - Google Patents

Abstract

DC60 (20/01/54) This invention is a new process for creating a cavity for a surface structure with a high aspect ratio. The aspect ratio is the ratio between width and depth. The creation method is as follows: using the DRIE (Deep Reactive-Ion Etching) technique to etch silicon into a cavity, for example, etching a cavity with a depth of 3 microns. After that, the cavity is filled by creating two layers of silicon dioxide with two techniques: the first layer is a 1 micron thick wet oxide insulating layer to reduce sharpness at the edge of the cavity. The second layer is an oxide insulating layer using either PECVD or LPCVD, with a thickness equal to the depth of the etched cavity minus 0.75 microns. After that, the oxide insulating layer is etched outside the cavity. By using a photoresist film as a barrier and etching with hydrofluoric (HF) chemicals at the edge of the hole and peeling off the film. After that, smoothing is done by 2 methods: Method 1, coat the Spin on Glass (SOG) film by spin method and dry etching with RIE machine. Method 2, coat the photoresist film and dry etching with RIE machine by etching to the silicon film layer at the edge of the hole. The silicon dioxide insulating layer is in the same plane as the silicon layer. Then, a polysilicon film is created to be the diaphragm layer. This new technique has the advantage of being able to create a cavity of the desired depth, enabling the creation of a detector device with a higher working range, such as A pressure sensing device with a cavity depth of 1.4 microns, under the condition of a diaphragm made of 1.5 microns thick polysilicon and an area of 110 x 110 square microns, can measure pressure from 0 to 8 bar. However, if the cavity depth can be increased to 3 microns under the same condition, it can measure pressure from 0 to 15 bar, etc. This invention is a new process for creating cavities for surface structures with high aspect ratios. The aspect ratio is the ratio of width to depth. The method of creation is as follows: by using the DRIE (Deep Reactive-Ion Etching) technique to etch silicon into a cavity, for example, a cavity depth of 3 microns is etched. After that, the cavity is filled by creating Two layers of silicon dioxide film are fabricated using two techniques: the first layer is a 1 micron thick wet oxide insulating layer to reduce the sharpness at the edge of the hole. The second layer is an insulating oxide layer using either PECVD or LPCVD, with a thickness equal to the depth of the etched channel minus 0.75 microns. The insulating oxide is then etched off outside the hole with a photoresist film. The etching is done with hydrofluoric (HF) chemicals at the edge of the hole and the film is peeled off. The surface is then smoothed with two methods: Method 1: Coating Spin on Glass (SOG) film using the spin method and dry etching with a RIE machine. Method 2: Coating the photoresist film and dry etching with a RIE machine, etching down to the silicon film layer at the edge of the hole. The silicon dioxide insulating layer is in the same plane as the silicon layer. Then, a polysilicon film is fabricated to serve as the diaphragm layer. This new technique has the advantage of being able to create a cavity of the desired depth, enabling the fabrication of a sensing device with a higher working range, such as a pressure sensor with a cavity depth of 1.4 microns under the condition that a diaphragm made of 1.5 microns thick polysilicon and an area of 110 x 110 square microns can measure pressure from 0 to 8 bar. However, if the cavity depth can be increased to 3 microns under the same condition, it can measure pressure from 0 to 15 bar.

Claims (1)

1. Cavity formation process for silicon thin sheet detector The surface consists of the steps of - Insulating the gaps on the semiconductor substrate (1) to a thickness equal to the required cavity depth (6). The gap (6) is released and forms a layer of diaphragm film over the area. The gap Unique is the process of creating the cavity layer (Cavity), which consists of the steps of - creating a barrier around the periphery of the gap (6) to prevent tagging: