CN101538005B - Method for manufacturing optical modulation thermal imaging focal plane array - Google Patents

Abstract

The invention relates to a method for manufacturing an optical modulation thermal imaging focal plane array, which comprises the following steps: step 1, manufacturing a doped layer on the upper surface of a monocrystalline silicon piece; step 2, etching a groove on the upper surface of the monocrystalline silicon piece according to a preset pattern; step 3, covering a silicon oxide layer on the inner wall of the groove; step 4, growing polysilicon to fill the groove; step 5, covering a thin film layer A on the upper surface of the monocrystalline silicon piece; step 6, covering a metal layer on the thin film layer A; step 7, etching the metal layer according to a preset pattern; step 8, etching the thin film layer A according to a preset pattern; step 9, corroding monocrystalline silicon from the back of the silicon wafer according to a preset pattern; and step 10, corroding the doped layer according to a preset pattern to obtain the fully-hollowed structure optical modulation thermal imaging focal plane array with the silicon support frame.

Description

Fabrication method of light modulation thermal imaging focal plane array

technical field

The invention belongs to the field of silicon micromachining in microelectronic technology, and in particular relates to a method for manufacturing a fully hollowed-out structural light modulation thermal imaging focal plane array (FPA) with a silicon support frame by silicon micromachining technology. the

Background technique

Micro-electromechanical systems (MEMS)-based uncooled infrared detection focal plane arrays (FPA) that use optical modulation methods mostly use micro-cantilever thermal isolation structures, and their detection sensitivity is directly related to the structure of the device. This type of focal plane array (FPA) usually adopts a multilayer dual-material cantilever beam thermal isolation structure with a sacrificial layer. The disadvantage of isolation is that infrared radiation will be reflected by the silicon substrate before reaching the sensitive unit, resulting in low utilization of infrared radiation for such devices and affecting device performance. In order to solve this problem, we have proposed a light-modulating uncooled infrared focal plane array with a fully hollowed-out substrate structure. The feature of this device is that the silicon substrate in the infrared sensitive unit area is completely removed, and the sensitive unit relies entirely on Supported by a layer of membrane structure. This light-modulating uncooled infrared focal plane array with a fully hollow structure solves the problem that infrared radiation is reflected by a silicon substrate, thereby greatly improving the response sensitivity performance of the device. However, this device is extremely fragile and easily damaged because the device structure is only supported by a thin film. the

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for manufacturing a fully hollow structured light modulation thermal imaging focal plane array (FPA) with a silicon support frame. the

The present invention solves the above-mentioned technical problems through the following technical solutions. The present invention proposes a method for manufacturing a fully hollow structured light modulation thermal imaging focal plane array with a silicon support frame, including the following steps:

Step 1, covering the surface of the monocrystalline silicon wafer with a doped layer;

Step 2. Etching grooves on the surface of the single crystal silicon wafer according to the preset pattern;

Step 3, covering the inner wall of the trench with a silicon oxide layer;

Step 4, growing polysilicon to fill the trench;

Step 5, covering the surface of the monocrystalline silicon wafer with a film layer A;

Step 6, covering the metal layer on the film layer A;

Step 7. Etching the metal layer according to the preset pattern;

Step 8. Etching the thin film layer A according to the preset pattern;

Step 9. Etch the monocrystalline silicon from the back according to the preset pattern;

Step 10, etching the doped layer according to a preset pattern. the

Thus, a fully hollow structured light modulation thermal imaging focal plane array with a silicon support frame is obtained. the

Preferably, the monocrystalline silicon crystal orientation of the above-mentioned single crystal silicon wafer is <100>. the

Preferably, in the above step 1, the doped layer is doped with concentrated B (boron), boron, P (phosphorus), or As (arsenic) impurities. the

Preferably, in the above-mentioned step 2, the described etching groove on the monocrystalline silicon wafer adopts SiO2 (silicon dioxide) as a masking layer, and uses RIE (Reactive Particle Etching) equipment or ICP (Inductively Coupled Plasma Etching) ) devices are realized by anisotropic dry deep silicon etching. the

Preferably, in the above step 3, growing silicon oxide on the inner wall of the trench is realized by using a dry oxidation process or a wet oxidation process. the

Preferably, in the above step 4, growing polysilicon is to adopt LPCVD (low pressure chemical vapor deposition) process to generate a layer of polysilicon on the upper surface of the single crystal silicon wafer, and fill up the groove, and then use Br (bromine) substrate to etch Etching gas and RIE (Reactive Ion Etching) equipment, through polysilicon dry etching excess polysilicon. the

Preferably, the above step 5 also includes covering the lower surface of the single crystal silicon wafer with a thin film layer B, and the thin film layer A and the thin film layer B are both silicon nitride materials or silicon oxide materials, and the process adopts LPCVD (low pressure chemical vapor deposition) or PECVD (plasma enhanced chemical vapor deposition). the

Preferably, in the above step 6, the covering metal layer is realized by MSS (magnetron sputtering) process. the

Preferably, in the above step 7, the etching of the metal layer A is achieved by using RIE (Reactive Ion Etching) equipment through a dry etching process. the

Preferably, in the above step 8, the etching thin film layer A is formed by etching with RIE (Reactive Ion Etching) equipment. the

Preferably, the above step 9 further includes etching the thin film layer B according to a preset pattern, and the etching process is realized by using RIE (reactive ion etching) equipment and RIE (reactive ion etching) process. the

Preferably, in the above step 9, the etching of single crystal silicon uses KOH (potassium hydroxide) solution or TMAH (tetramethylammonium hydroxide) solution as the etching solution. the

Preferably, in the above step 10, the etching of the doped layer uses XeF ₂ (xenon difluoride) as the etching gas.

In summary, from the perspective of microfabrication, the present invention combines technologies such as deep etching of bulk silicon, polysilicon trench filling, self-termination of monocrystalline silicon wet etching, and isotropic dry etching of silicon to propose a A method for manufacturing a fully hollow structured light modulation thermal imaging focal plane array of a supporting frame, thereby perfecting a method for manufacturing a fully hollow structured light modulating thermal imaging focal plane array (FPA) with a silicon support frame proposed by the present invention. the

A method for manufacturing a fully hollow structured light-modulated thermal imaging focal plane array (FPA) with a silicon support frame of the present invention also includes: a series of pattern transfer operations such as gluing, exposure, and development of positive photoresist. the

The above description is only an overview of the technical solutions of the present invention. In order to understand the technical means of the present invention more clearly and implement them according to the contents of the description, the preferred embodiments of the present invention and accompanying drawings are described in detail below. the

Description of drawings

1 to 12 are structural schematic diagrams of products formed in various steps of the method for manufacturing a fully hollow structured light modulation thermal imaging focal plane array with a silicon support frame according to the present invention. the

Detailed ways

In order to further explain the technical means and effects of the present invention to achieve the intended purpose of the invention, the following combined with the accompanying drawings and preferred embodiments, the full hollow structured light modulation thermal imaging focal plane with a silicon support frame proposed according to the present invention The fabrication method of the array and its specific implementation, structure, features and functions are described in detail below. the

Step 1, referring to Fig. 1, adopting the method of high-temperature annealing after high-energy particle implantation or the standard impurity diffusion doping process, doping a layer of concentrated B (boron) on the front surface of the single crystal silicon wafer 101 with a crystal orientation of <100> A doped layer 102, the impurity concentration of which is greater than 1e19l/cm ³ , and the depth of the doped concentrated B (boron) doped layer 102 is between 2 microns and 20 microns;

Step 2, referring to FIG. 2, using RIE (Reactive Particle Etching) equipment or ICP (Inductively Coupled Plasma Etching) equipment, using SiO2 (silicon dioxide) as the mask layer 103, anisotropic Dry deep silicon etching to form trenches, and obtain trenches with a depth between 5 microns and 30 microns and a width between 0.5 microns and 3 microns;

Step 3, referring to FIG. 3, oxidizing the monocrystalline silicon wafer by using a dry oxidation process or a wet oxidation process, and growing a silicon oxide layer 104 of 0.05 micron to 0.1 micron on the inner wall of the trench;

Step 4, with reference to Fig. 4 and Fig. 5, adopt LPCVD (low pressure chemical vapor deposition) process, grow a layer of polysilicon layer 105 on the front side of described monocrystalline silicon wafer 101, the thickness of polysilicon layer 105 is between 0.25 microns to 1.5 microns , and fill the groove; use Br (bromine) based etching gas, adopt RIE (reactive ion etching) equipment, etch away the polysilicon on the single crystal silicon wafer 101 except in the groove;

Step 5, referring to FIG. 6, using LPCVD (low pressure chemical vapor deposition) process or PECVD (plasma enhanced chemical vapor deposition) process, on both sides of the single crystal silicon wafer 101, grow Low-stress silicon nitride film layer 106 or silicon oxide film layer 106;

Step 6, referring to FIG. 7, using MSS (magnetron sputtering) process, sputtering a layer of aluminum metal with a thickness between 0.1 micron and 0.8 micron on the silicon nitride film layer 106 or silicon oxide film layer 106 film layer 107;

Step 7, referring to FIG. 8, using RIE (reactive ion etching) equipment, using a dry etching process to etch away part of the aluminum metal film layer 107;

Step 8, referring to FIG. 9, using RIE (reactive ion etching) equipment, using fluorine-based gas, etching away part of the silicon oxide film layer 106 to form a cantilever beam structure;

Step 9, with reference to Fig. 10 and Fig. 11, use the lithography machine with double-sided lithography function such as the MA6 of SUSS company or the 620 lithography machine of EVG company to define the back pattern on the back side of the single crystal silicon wafer 101, use RIE (reaction Ion etching) equipment adopts the RIE (reactive ion etching) process to dry-etch the silicon nitride film layer 106 or silicon oxide film layer 106 on the back side of the silicon wafer corresponding to the pattern area on the front side of the silicon wafer, so that The monocrystalline silicon part on the back side of the monocrystalline silicon wafer 101 is exposed, which needs to use a photolithography machine with double-sided photolithography function such as the MA6 of SUSS Company or the 620 photolithography machine of EVG Company; the back part of the monocrystalline silicon wafer 101 is exposed The single crystal silicon window is etched, and the silicon doped with a high concentration of B element is not corroded by the etching solution and the anisotropic etching solution has a very low etching rate on the <111> crystal surface of the single crystal silicon. Make the etching process reach the concentrated boron-doped layer 102, then stop automatically, KOH (potassium hydroxide) solution or TMAH (tetramethylammonium hydroxide) solution, the concentration is respectively 33% KOH (potassium hydroxide) solution or 20% The TMAH (tetramethylammonium hydroxide) solution, the corrosion temperature is between 50 degrees and 90 degrees. the

Step 10, referring to FIG. 12 , using XeF ₂ (xenon difluoride) as the etching gas under normal pressure, using dry anisotropic etching to etch away the concentrated B ( The single crystal silicon with boron) impurity, that is, the concentrated B (boron) doped layer 102, completes the etching work, and finally releases the device structure to complete the processing procedure of the entire device.

The method of the above embodiment also includes: a series of pattern transfer operations such as coating of positive photoresist, exposure, and development. the

Claims (13)

1. A method for making a light-modulated thermal imaging focal plane array, characterized in that the method comprises: Step 1, manufacturing a doped layer on the upper surface of the single crystal silicon wafer; Step 2. Etching grooves on the upper surface of the monocrystalline silicon wafer according to a preset pattern; Step 3, covering the inner wall of the trench with a silicon oxide layer; Step 4, growing polysilicon to fill the trench; Step 5, covering the upper surface of the monocrystalline silicon wafer with thin film layer A, and covering the lower surface of the single crystal silicon wafer with thin film layer B; Step 6, covering the metal layer on the film layer A; Step 7. Etching part of the metal layer according to the preset pattern; Step 8. Etching part of the thin film layer A according to the preset pattern; Step 9. Etch the single crystal silicon from the back of the silicon wafer according to the preset pattern; etch the thin film layer B according to the preset pattern; Step 10: Etching the doped layer according to a preset pattern to obtain a fully hollow structured light modulation thermal imaging focal plane array with a silicon support frame. 2 . The method for fabricating a light modulation thermal imaging focal plane array according to claim 1 , wherein the monocrystalline silicon crystal orientation of the monocrystalline silicon wafer is <100>. 3 . 3. The manufacturing method of light modulation thermal imaging focal plane array according to claim 1, characterized in that, in the above-mentioned step 1, the doped layer adopts the method of high-temperature annealing after high-energy particle implantation or standard impurity The diffusion doping process is realized by doping concentrated boron, arsenic or phosphorus on the single crystal silicon wafer. 4. The manufacturing method of light modulation thermal imaging focal plane array according to claim 1, characterized in that, the etching groove on the monocrystalline silicon wafer described in the above step 2 is to use silicon dioxide as a masking layer, It is realized by anisotropic dry deep silicon etching using reactive particle etching equipment or inductively coupled plasma etching equipment. 5 . The method for fabricating a light modulation thermal imaging focal plane array according to claim 1 , wherein, in the above step 3, the growth of silicon oxide on the inner wall of the trench is realized by a dry oxidation process or a wet oxidation process. 6 . 6. The manufacturing method of light modulation thermal imaging focal plane array according to claim 1, characterized in that, in the above-mentioned step 4, growing polysilicon is to adopt a low-pressure chemical vapor deposition process to generate a layer of polysilicon on the upper surface of a single crystal silicon wafer , and fill the trenches, and then use bromine-based etching gas and reactive ion etching equipment to dry-etch the polysilicon on the single crystal silicon wafer except in the trenches. 7. The manufacturing method of light modulation thermal imaging focal plane array according to claim 1, characterized in that, the thin film layer A and the thin film layer B described in the above step 5 are both silicon nitride materials or silicon oxide materials, the The process is realized by low pressure chemical vapor deposition or plasma enhanced chemical vapor deposition. 8 . The method for fabricating a light-modulated thermal imaging focal plane array according to claim 1 , wherein, in the above step 6, the covering metal layer is realized by using a magnetron sputtering process. 9. The manufacturing method of light-modulated thermal imaging focal plane array according to claim 1, characterized in that, in the above-mentioned step 7, the etching metal layer is to use reactive ion etching equipment, through a dry etching process Achieved. 10 . The method for manufacturing a light modulation thermal imaging focal plane array according to claim 7 , wherein, in the above step 8, the etching thin film layer A is formed by etching with reactive ion etching equipment. 11 . 11. The manufacturing method of light modulation thermal imaging focal plane array according to claim 1, characterized in that, the etching process in the above step 9 is realized by using reactive ion etching equipment and adopting reactive ion etching process. 12. The manufacturing method of light modulation thermal imaging focal plane array according to claim 1, characterized in that, in the above step 9, potassium hydroxide solution or tetramethylammonium hydroxide is used for the etching of single crystal silicon solution as a corrosion solution. 13 . The method for fabricating a light modulation thermal imaging focal plane array according to claim 1 , wherein, in the above step 10, xenon difluoride is used as the etching gas for the etching of the doped layer. 14 .

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