Two manufacturing methods for optical readout infrared detector

March 09, 2024

If a worker wants to do something good, he must first sharpen his tools. In today's globalization, patents are not only a means of protection for innovation, but have become a weapon in the commercial battlefield. Mames Consulting has created a patent operation platform for MEMS, sensors and IoT, integrated intellectual property resources in the entire industry chain, and actively promoted the protection and effective use of intellectual property. The pixel structure of the optical readout infrared detector generally includes: an anchor, a support beam (including a bimaterial beam and a heat insulating beam), and a movable micromirror. The anchor stands above the substrate, and the movable micromirror is coupled to the anchor through the support beam and suspended above the substrate. The bimaterial beam is generally composed of two materials having a large difference in thermal expansion coefficient, such as a metal material and a dielectric material; the heat insulating beam is composed of a material having a small thermal conductivity; the movable micromirror portion generally includes a visible light reflecting layer and infrared Absorbing layer. The current optical readout infrared detectors are generally based on a silicon substrate for device structure and process design, and the fabrication methods can be divided into two categories:

Figure 1 Optical readout infrared detectors based on surface micromachining technology are fabricated by surface micromachining technology (as shown in Figure 1). Silicon is used as the substrate, and silicon oxide, phosphosilicate glass, and polysilicon are used. The sacrificial layer generally uses wet etching to release the pixel structure. Since there is no need to remove the substrate silicon, the mechanical strength of the device is good, and there is no thermal crosstalk between the pixels; since the thickness of the sacrificial layer is only a few micrometers, the optical readout infrared detector array fabricated by this method is easily released and the silicon is easily The substrate is stuck, and infrared radiation needs to pass through the silicon substrate to be incident on the infrared absorbing layer in the pixel structure, and the infrared transmittance of silicon in the wavelength range of 8-14 μm is about 50%, that is to say, The infrared radiation utilization rate of the devices is generally around 50%.

Figure 2: Optical readout infrared detectors based on bulk silicon micromechanical process. The other type is fabricated by bulk silicon micromachining (as shown in Figure 2). The deep reactive ion etching (DRIE) method is generally used to remove the underside of the pixel. The silicon substrate releases the pixel array, and the infrared radiation can be incident on the infrared absorption layer in the pixel structure without blocking, thereby greatly improving the utilization of the infrared radiation; since the silicon substrate under the pixel structure is removed, the pixel and the substrate are avoided. However, the bombardment of high-energy particles during deep reactive ion etching will cause some damage to the pixel structure. Removing the silicon substrate under the pixel will cause the mechanical strength of the device to decrease. In addition, if the silicon substrate under the pixel is When removed completely, there will be severe thermal crosstalk between pixels. In the current solution, the visible light reflecting layer is usually deposited directly on the infrared absorbing layer. On the one hand, the movable micromirror deforms due to the double material effect, resulting in a decrease in device sensitivity; on the other hand, the visible light reflecting layer occupies the entire pixel area. The proportion of the pixel is small, the space for reading signals between pixels is large, and the visible light utilization rate of the pixel is low. Therefore, the current manufacturing method cannot meet the requirements of the optical readout infrared detector for mechanical strength, thermal crosstalk, non-destructive release of pixels, utilization of infrared radiation, flatness of movable micromirrors, and utilization of visible light. [Recommended Invention Patent] "A Optical Readout Infrared Detector Structure and Method of Fabricating the Same" [Invention] The present invention provides an improved optical readout infrared detector structure and a method of fabricating the same. The detector structure comprises: a glass substrate and a suspended structure suspended on the glass substrate by the second anchor; the suspension structure comprises a visible light reflecting layer, an infrared absorbing layer and a supporting beam. Wherein, the visible light reflecting layer is suspended on the glass substrate, the infrared absorbing layer is suspended on the visible light reflecting layer by the first anchor, the supporting beam is suspended on the visible light reflecting layer, and one end of the supporting beam is connected to the infrared absorbing layer in the same plane. The other end is fixed to the glass substrate by a second anchor.

3 is a cross-sectional view of a modified optical readout infrared detector of the present invention. The method for fabricating an optical readout infrared detector array based on a bonding technique has the following beneficial effects: 1. The thickness of the first sacrificial layer is increased, and the dry layer is used. The method is released to ensure the safe release of the pixel structure; 2. The complete glass is used as the substrate, and the pixel structure is fabricated on the glass substrate, so that the device has good mechanical strength and avoids thermal crosstalk between pixels; 3. Infrared radiation Directly incident on the infrared absorbing layer improves the infrared radiation utilization rate of the device; 4. The visible light reflecting layer and the infrared absorbing layer are spatially separated, and the visible light reflecting layer no longer has deformation due to the double material effect, and the visible light reflecting surface The increase in size greatly increases the utilization of visible light.

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