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CN-121983487-A - MEMS suspended heating bearing structure for TEM characterization and preparation method thereof

CN121983487ACN 121983487 ACN121983487 ACN 121983487ACN-121983487-A

Abstract

The application provides a MEMS suspended heating bearing structure for projection electron microscope (TEM) characterization and a preparation method thereof. The surface of the device layer is provided with a first silicon oxide layer, a heating electrode is arranged on the first silicon oxide layer, and the surface of the substrate layer is provided with a second silicon oxide layer for back patterning and etching control. The device layer silicon is etched from the back to form a second cavity, and the second cavity covers the bearing area, the transmission window and the projection range of the support beam in the thickness direction. And is communicated with the first cavity, thereby forming a through cavity heat insulation structure. The application can realize stable bearing and controllable heating of the sample to be tested while maintaining the permeability of the electron beam transmission window, and also meets the requirements of structural reliability, low power consumption and electrical parasitic inhibition.

Inventors

  • LIU YAOWEN
  • LIU JIANYI

Assignees

  • 苏州博纳微电子科技有限公司

Dates

Publication Date
20260505
Application Date
20260203

Claims (10)

  1. 1. The MEMS suspended heating bearing structure for TEM characterization is characterized by comprising an SOI silicon wafer, a first silicon oxide layer (5), a second silicon oxide layer (6) and a heating electrode (1), wherein the SOI silicon wafer sequentially comprises device layer silicon (2), an oxygen burying layer (4) and substrate layer silicon (3), the first silicon oxide layer (5) is arranged on the surface of the device layer silicon (2), the second silicon oxide layer (6) is arranged on the surface of the substrate layer silicon (3), and the heating electrode (1) is arranged on the first silicon oxide layer (5); The device layer silicon (2) is provided with a first cavity (21) to form a suspension supporting structure (22), the first silicon oxide layer (5) is provided with an opening which is isomorphous with the first cavity (21), the suspension supporting structure (22) comprises a central bearing area (222), a plurality of supporting beams (221) connected with the central bearing area and a transmission window area (223), the transmission window area (223) is provided with a through hole array (2231), and grid supporting ribs (2232) are reserved between adjacent through holes; The substrate layer silicon (3) is provided with a second cavity (31), and the second silicon dioxide layer (6) is provided with an opening which is in the same shape as the second cavity (31), wherein the projection of the second cavity (31) in the thickness direction at least covers the projection of the central bearing area (222) and the support beam (221); The buried oxide layer (4) is completely removed in the area corresponding to the first cavity (21) and the second cavity (31), so that the first cavity (21) is communicated with the second cavity (31), and a through heat insulation cavity is formed below the central bearing area (222).
  2. 2. MEMS suspended heating load-bearing structure for TEM characterization according to claim 1, wherein the thickness of the device layer silicon (2) is less than 10 μm, the thickness of the buried oxide layer (4) is 1-2 μm and the thickness of the substrate layer silicon (3) is 200-500 μm.
  3. 3. MEMS suspended heating load-bearing structure for TEM characterization according to claim 1, wherein the transition junction of the support beam (221) and the central load-bearing zone (222) is provided with a fillet, the width of the support beam (221) is 2-10 μm and the fillet radius is 2-50 μm.
  4. 4. MEMS suspended heating carrying structure for TEM characterization according to claim 1, wherein the heating electrodes (1) are spirally distributed in the central carrying region (222) and led out to pads of non-suspended regions for external electrical connection.
  5. 5. MEMS suspended heating load-bearing structure for TEM characterization according to claim 1, wherein the through-hole array (2231) is a hexagonal close-packed array or an orthogonal array, the through-holes in the through-hole array (2231) having a hole diameter of 2-10 μm and a hole pitch of 5-20 μm.
  6. 6. The preparation method of the MEMS suspended heating bearing structure for TEM characterization is characterized by comprising the following steps of: a) Taking an SOI silicon wafer, forming a first silicon oxide layer (5) on the surface of a device layer silicon (2) of the SOI silicon wafer, and forming a second silicon oxide layer (6) on the surface of a substrate layer silicon (3) of the SOI silicon wafer; b) Forming a heating electrode (1) on the first silicon oxide layer (5); c) Carrying out graphical etching on the surface of the first silicon oxide layer (5), sequentially etching the first silicon oxide layer (5) and the device layer silicon (2) until the buried oxide layer (4) of the SOI silicon wafer to form a first cavity (21) and define a suspended supporting structure (22), and simultaneously forming a penetrating hole array (2231) of a transmission window region (223); d) Carrying out graphical etching on the surface of the second silicon dioxide layer (6), and sequentially etching the second silicon dioxide layer (6) and the substrate layer silicon (3) until the oxygen burying layer (4) to form a second cavity (31); e) And removing the buried oxide layer (4) positioned in the corresponding area of the first cavity (21) and the second cavity (31), so that the first cavity (21) is communicated with the second cavity (31), and the suspended supporting structure (22) is released.
  7. 7. The method for preparing a MEMS suspended heating load-bearing structure for TEM characterization according to claim 6, wherein the first silicon oxide layer (5) and the second silicon oxide layer (6) are formed by means of thermal oxidation or PECVD or LPCVD.
  8. 8. Method for the preparation of a MEMS suspended heating load-bearing structure for TEM characterization according to claim 6, characterised in that the formation of a heating electrode (1) on the first silicon oxide layer (5) comprises: Firstly, performing magnetron sputtering or vapor plating on titanium, then performing magnetron sputtering or vapor plating on platinum, obtaining a metal layer on the first silicon oxide layer (5), and forming a spiral heating electrode pattern after photoetching and developing; the metal layer not covered by the pattern is removed by ion beam etching IBE to obtain the heating electrode (1).
  9. 9. The method of preparing a MEMS suspended heating load-bearing structure for TEM characterization according to claim 6, wherein the patterning of the surface of the first silicon oxide layer (5) comprises: RIE is adopted to etch the first silicon oxide layer (5) and etch the device layer silicon (2) to the buried oxide layer (4), wherein the etching of the device layer silicon (2) adopts deep silicon etching or KOH/TMAH wet etching.
  10. 10. The method of preparing a MEMS suspended heating load-bearing structure for TEM characterization according to claim 6, wherein the patterning of the surface of the second silicon dioxide layer (6) comprises: And etching the second silicon dioxide layer (6) and etching the substrate layer silicon (3) to the buried oxide layer (4) by using RIE, wherein the etching of the substrate layer silicon (3) adopts deep silicon etching or KOH/TMAH wet etching, and the removing of the buried oxide layer (4) adopts RIE dry etching or HF wet etching.

Description

MEMS suspended heating bearing structure for TEM characterization and preparation method thereof Technical Field The invention relates to the technical field of micro-mechanical electronic system processing, in particular to an MEMS suspended heating bearing structure for TEM characterization and a preparation method thereof. Background In Transmission Electron Microscope (TEM) systems, MEMS micro-heating chips are often used to achieve precise temperature control of the sample. Such chips are typically fabricated using a sacrificial layer release process by selectively etching away a layer of material (i.e., the sacrificial layer) under the device layer to form a suspended heating or sensing structure. However, the etching process of the sacrificial layer generally cannot completely remove the bottom substrate, which leads to that after the electron beam penetrates through the sample, a layer of continuous silicon or dielectric film still needs to be used, so that scattering background and absorption are increased, imaging quality is reduced, adhesion is easily caused by the action of fluid tension in the releasing process of the sacrificial layer, and problems such as pollution, structural warping and the like are easily caused due to insufficient releasing. Another type of solution removes most of the silicon by back Deep Reactive Ion Etching (DRIE), leaving only a thin SiNx or Si film on the front surface as an electron-transmissive window. Although the local thinning is realized, the problems are that (1) the functional layers such as a heating electrode and the like are usually directly arranged on a film or are closely attached to a silicon layer, parasitic capacitance and a leakage path are larger, high-speed low-noise electric measurement and temperature control are not facilitated, and (2) the root of a cantilever beam actually manufactured is thinner than the designed due to the fact that a sawtooth-shaped step appears on the side wall of the deep silicon etching, so that the stress concentration phenomenon is more likely to appear, and the stability of the structure is influenced. (3) The SiNx film is difficult to realize larger thickness, so that the SiNx film has insufficient rigidity and poor mechanical property when being used as a structural layer. In summary, the existing TEM chip technology still has room for improvement in terms of the cantilever beam release mode, window permeability and electrical properties, and a novel structure and process are needed, which simultaneously give consideration to mechanical stability, transmission performance, heat insulation low power consumption, electrical properties and installation convenience. Disclosure of Invention Aiming at the defects and improvement requirements of the existing heating structure applied to TEM characterization. The invention provides an MEMS suspended heating bearing structure for TEM characterization and a preparation method thereof, the structure is based on an SOI wafer to realize and integrate a heating function, a supporting part of the MEMS suspended heating bearing structure adopts a round angle suspended beam structure penetrating through silicon of a substrate layer, and the MEMS suspended heating bearing structure can overcome the defects that 1, the reliability of the structure is reduced due to stress concentration of the root of a suspended beam, 2, the view field transmission capacity is insufficient due to non-penetration of the bottom or limited window size, and 3, the parasitic capacitance of a heating electrode structure is larger, and electric leakage and noise are higher. The embodiment of the invention provides an MEMS suspended heating bearing structure for TEM characterization, which comprises an SOI silicon wafer, wherein the SOI silicon wafer sequentially comprises device layer silicon, an oxygen buried layer and substrate layer silicon, a first silicon oxide layer is arranged on the surface of the device layer silicon and forms a heating electrode on the first silicon oxide layer, and a second silicon oxide layer is arranged on the back surface of the substrate layer silicon and used as a back surface patterning and etching mask layer. The method comprises the steps of forming a first cavity in device layer silicon to form a suspended supporting structure, forming a second cavity in substrate layer silicon and covering the suspended supporting structure area in a projection mode, removing an oxygen burying layer in the corresponding area of the first cavity and the second cavity, enabling the first cavity to be communicated with the second cavity to release the suspended supporting structure, and forming a through heat insulation cavity below a central bearing area. In a preferred embodiment, the central carrying region includes a transmissive window region provided with an array of through holes and retaining grid support ribs to provide support and heating while satisfying electron beam transmissi