Infrared MEMS bridge column structure and process method

Abstract

The present invention discloses an infrared MEMS bridge column structure and a formation method. The structure adopts a multi-layer thin film composite structure, including a first release protection layer, a metal dielectric layer and a second release protection layer; the first release protection layer is a silicon oxide layer; the second release protection layer is a four-layer structure, which is a mixed layer of silicon oxynitride and silicon oxide, a silicon oxide layer, a silicon oxynitride layer, and a silicon oxide layer from bottom to top. The present invention neutralizes several film stresses by controlling the stress of the bridge structure: by adding a variety of films with reaction stresses, the warping of the bridge caused by the release of the bridge structure can be effectively reduced, which does not affect the thickness of the overall bridge structure, and is also conducive to the alignment of the subsequent photolithography process and the control of the subsequent etching channel.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device manufacturing, and in particular to an infrared MEMS bridge column structure in a MEMS product bridge structure, which can effectively support a MEMS hollowed-out structure and effectively reduce subsequent packaging abnormalities caused by warping of the bridge structure.

[0002] The invention also relates to a process method for the infrared MEMS bridge column structure. Background Art

[0003] Micro-electro-mechanical system (MEMS), also known as micro-electro-mechanical system, microsystem, micro-machine, etc., refers to high-tech devices with a size of several millimeters or even smaller. Its internal structure is generally in the micrometer or even nanometer level. It is an independent intelligent system. It is mainly composed of three parts: sensors, actuators (actuators) and micro-energy. Micro-electro-mechanical systems involve multiple disciplines and engineering technologies such as physics, semiconductors, optics, electronic engineering, chemistry, materials engineering, mechanical engineering, medicine, information engineering and bioengineering, and have opened up broad applications in the fields of intelligent systems, consumer electronics, wearable devices, smart homes, synthetic biology and microfluidics technology of system biotechnology. Common products include MEMS accelerometers, MEMS microphones, micromotors, micropumps, microvibrators, MEMS pressure sensors, MEMS gyroscopes, MEMS humidity sensors, etc. and their integrated products.

[0004] MEMS has the following basic characteristics: miniaturization, intelligence, multi-function, high integration and suitable for mass production. The goal of MEMS technology is to explore components and systems with new principles and functions through the miniaturization and integration of the system. MEMS technology is a typical multidisciplinary frontier research field, focusing on ultra-precision machining, and involves almost all fields of natural and engineering sciences, such as electronic technology, mechanical technology, physics, chemistry, biomedicine, materials science, energy science, etc. Its research content can generally be summarized into the following three basic aspects: 1. Theoretical basis: At the scale that MEMS can currently achieve, the basic physical laws of the macroscopic world still work, but due to the impact of size reduction (Scaling Effects), many physical phenomena are very different from the macroscopic world, so many of the original theoretical foundations will change, such as the size effect of force, the surface effect of microstructure, and the micro friction mechanism. Therefore, it is necessary to conduct in-depth research on microdynamics, microfluid mechanics, microthermodynamics, microtribology, micro-optics and microstructure. Although this aspect of research is valued, it is difficult and often requires scholars from multiple disciplines to conduct basic research. 2. Technical basic research: mainly including technical basic research on micro-mechanical design, micro-mechanical materials, micro-fabrication, micro-assembly and packaging, integration technology, micro-measurement, etc. 3. Application research of micro-mechanics in various disciplines.

[0005] Micro-electromechanical systems (MEMS) are high-tech electronic mechanical devices developed on the basis of microelectronics technology (semiconductor manufacturing technology) and are manufactured by integrating technologies such as lithography, corrosion, thin film, LIGA, silicon micromachining, non-silicon micromachining and precision machining.

[0006] Amorphous silicon is an allotropic form of silicon that can be deposited in thin films on a variety of substrates, providing certain unique features for a variety of electronic applications. Amorphous silicon is used in mass-produced microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS), solar cells, microcrystalline silicon and microamorphous silicon, and is even useful for rolling process technologies on various substrates. Traditional MEMS devices rely on typical materials used in silicon-based circuit manufacturing, such as single crystal silicon, polycrystalline silicon, silicon oxide and silicon nitride. Due to the mechanical nature of MEMS devices, material properties such as Young's modulus, thermal expansion coefficient and yield strength are very important for MEMS design. MEMS structures often have unsupported (or overhanging) components, so the stress and stress gradient in the film need to be strictly controlled, otherwise the unsupported components will break or curl, causing the structure to fail.

[0007] The existing process includes the following steps:

[0008] Step 1, forming a metal reflective layer on a semiconductor substrate, depositing a sacrificial layer and patterning it after patterning;

[0009] Step 2, depositing a protective layer and a photosensitive layer as a whole;

[0010] Step 3, patterning the photosensitive layer;

[0011] Step 4, in the support hole area outside the bridge column, patterning the membrane layer in the support hole area;

[0012] Step 5, overall deposition to form a metal electrode film;

[0013] Step 6, depositing a DARC film (Dielectric Anti Reflective Coating, DARC) and patterning it;

[0014] Step seven, etching the metal electrode film layer;

[0015] Step eight, depositing a protective layer film to pattern the bridge column structure area;

[0016] Step nine, patterning the contact PAD area.

[0017] The membrane layer of the bridge column structure formed by the above process is prone to membrane fracture due to uneven stress release. Summary of the invention

[0018] The technical problem to be solved by the present invention is to provide an infrared MEMS bridge column structure and a forming method, which can effectively reduce the subsequent packaging anomalies caused by the warping of the bridge structure through the new composite membrane structure layer design.

[0019] In order to solve the above problems, the infrared MEMS bridge column structure described in the present invention comprises a first release protection layer, a metal dielectric layer and a second release protection layer;

[0020] The first release protection layer is a silicon oxide layer;

[0021] The second release protection layer has a four-layer structure, which includes, from bottom to top, a mixed layer of silicon oxynitride and silicon oxide, a silicon oxide layer, a silicon oxynitride layer, and a silicon oxide layer.

[0022] A further improvement is that, in the area outside the bridge column structure, there is also a MEMS structure formed by other multiple film layers, and the layers outside the bridge column structure area include a substrate, a metal reflective layer, a dielectric layer, a release layer, a first release protection layer, a photosensitive layer, a metal electrode, a DARC layer and a second release protection layer;

[0023] The first release protection layer is deposited on the release layer and is located on the dielectric layer together;

[0024] The photosensitive layer is deposited on the first release protection layer;

[0025] The DARC layer is deposited on the metal electrode;

[0026] The second release protection layer is deposited on the DARC layer.

[0027] A further improvement is that the substrate is a silicon substrate, which is a circuit substrate for reading infrared sensor signals.

[0028] A further improvement is that the reflective layer is a metal film with high reflectivity, and the material is gold, silver, aluminum or copper, or a mixture of several of these materials.

[0029] A further improvement is that the dielectric layer, the first release protection layer, and the DARC layer are all electrically insulating layers, and the material is one or more of silicon dioxide, silicon nitride, silicon oxynitride and silicon carbide; or one or more of silicon nitride and silicon oxynitride in a non-stoichiometric ratio; the silicon carbide can replace silicon oxide.

[0030] A further improvement is that the photosensitive layer material is an infrared absorbing amorphous silicon material.

[0031] A further improvement is that the material of the metal electrode is a metal film with a Ti / TiN structure.

[0032] A further improvement is that a support hole area is also included.

[0033] The process method of the infrared MEMS bridge column structure described in the present invention comprises:

[0034] Step 1, forming a metal reflective layer on a semiconductor substrate, depositing a sacrificial layer and patterning it after patterning;

[0035] Step 2, depositing a first release protection layer and a photosensitive layer as a whole;

[0036] Step 3, patterning the photosensitive layer;

[0037] Step 4, in the support hole area outside the bridge column, patterning the membrane layer in the support hole area;

[0038] Step 5, overall deposition to form a metal electrode film;

[0039] Step 6, overall deposition to form a DARC film and patterning;

[0040] Step seven, etching the metal electrode film layer;

[0041] Step eight, depositing a second release protective layer film to pattern the bridge column structure area;

[0042] Step nine, patterning the contact PAD area.

[0043] A further improvement is that the semiconductor substrate is a circuit substrate for reading infrared sensor signals.

[0044] A further improvement is that the semiconductor substrate is a silicon substrate.

[0045] The infrared MEMS bridge column structure and formation method described in the present invention are applied to the process with bridge structure in MEMS process, which can effectively reduce the bridge warping caused by the release of the bridge structure, thereby affecting the subsequent packaging test. The present invention mainly neutralizes several film stresses by controlling the stress of the bridge structure: by adding a variety of films with reaction stress, it does not affect the thickness of the overall bridge structure, and is also conducive to the alignment of the subsequent photolithography process and the control of the subsequent etching channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of a common infrared MENS structure, including support holes and bridge column structures.

[0047] Figure 2 The bridge column structure provided by the present invention comprises a first release protection layer, a metal layer and a second release protection layer.

[0048] Figures 3-4 It is a schematic diagram of the manufacturing process steps of the infrared MEMS structure in the prior art.

[0049] Figure 5 Schematic diagram of the manufacturing process steps of the infrared MEMS structure of the present invention (continued Figure 3 after the process shown). DETAILED DESCRIPTION

[0050] The infrared MEMS bridge column structure described in the present invention mainly improves the membrane layer of the MEMS structure bridge column. Since the traditional membrane layer is single, the stress cannot be offset and released, resulting in uneven stress and fracture of the membrane layer, causing the bridge column structure to be damaged and fail.

[0051] like Figure 1 As shown in the figure, it is a cross-sectional view of an infrared MEMS structure, which includes a support hole structure, a bridge column structure, and a membrane layer structure outside the bridge column area. In the figure, the support holes are located at both ends, and the MEMS structure is between the two support holes. Figure 1 The dotted circle in the figure is the bridge column structure area of ​​the infrared MEMS structure. Compared with the film layers in other areas, it is slightly concave. The traditional bridge column structure film layer is Figure 1As shown by the arrow in the figure, it generally includes two layers of stress release protection layers, that is, a three-layer sandwich structure with a metal layer in the middle of two silicon oxide layers, and the two silicon oxide layers are the corresponding two layers of stress release protection layers. Since the stress characteristics of a single layer of silicon oxide layer (for a certain layer of stress release protection layer) are relatively simple, warping in a single direction will occur during stress release, resulting in problems such as film fracture.

[0052] In view of the problem that the stress release protective layer of the traditional bridge column structure has a relatively single film layer, the present invention provides a composite film layer as a stress release protective layer, specifically a second release protective layer.

[0053] The bridge column structure includes a first release protection layer, a metal dielectric layer and a second release protection layer; Figure 2 shown.

[0054] The first release protection layer is a silicon oxide layer, which is the same as a conventional first release protection layer.

[0055] The metal dielectric layer is a Ti / TiN layer.

[0056] The second release protection layer comprises a four-layer structure, which, from bottom to top, is a mixed layer of silicon oxynitride and silicon oxide, a silicon oxide layer, a silicon oxynitride layer, and a silicon oxide layer.

[0057] In the area outside the bridge column structure, there is also a MEMS structure formed by other multiple film layers. The layers outside the bridge column structure area include a substrate, a metal reflective layer, a dielectric layer, a release layer, a first release protection layer, a photosensitive layer, a metal electrode, a DARC layer and a second release protection layer.

[0058] The first release protection layer is deposited on the release layer and is located on the dielectric layer together.

[0059] The photosensitive layer is deposited on the first release protection layer.

[0060] The DARC layer is deposited over the metal electrode.

[0061] The second release protection layer is deposited on the DARC layer.

[0062] The present invention changes the second release protection layer from a traditional single-layer silicon oxide film to a composite structure of a multi-layer film, through a composite film of a mixed layer of silicon oxynitride and silicon oxide, a silicon oxide layer, a silicon oxynitride layer, and a silicon oxide layer, each layer has different positive and negative stress characteristics, and the positive stress and the negative stress offset each other, so that the stress of the composite film layer reaches neutrality, and no problems such as curling will occur. With respect to the above structure, the present invention also discloses a method for making the MENS structure, which includes the following process steps:

[0063] Step 1, forming a metal reflective layer on a semiconductor substrate, depositing a sacrificial layer and patterning it after patterning;

[0064] Step 2, depositing a first release protection layer and a photosensitive layer as a whole;

[0065] Step 3, patterning the photosensitive layer;

[0066] Step 4, in the support hole area outside the bridge column, patterning the membrane layer in the support hole area;

[0067] Step 5, overall deposition to form a metal electrode film;

[0068] Step 6, overall deposition to form a DARC film and patterning;

[0069] Step seven, etching the metal electrode film layer;

[0070] Step eight, depositing a second release protective layer film to pattern the bridge column structure area;

[0071] Step nine, patterning the contact PAD area.

[0072] The above process steps can be referred to in the attached Figure 3 And attached Figure 5 , because the front-end process of the present invention is the same as that of the traditional device, that is, Figure 3 The process steps shown are as follows: Figure 3 From the following steps, the process of the present invention is different from the traditional process. It should be noted that the above nine process steps are different from the conventional process. Figure 3 and Figure 5 The combinations are not completely corresponding, that is, the steps in the drawings may be more detailed.

[0073] The bridge column structure described in the present invention can be formed through the above process.

[0074] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An infrared MEMS bridge column structure, characterized in that: The bridge column structure includes a first release protection layer, a metal dielectric layer and a second release protection layer; The first release protection layer is a silicon oxide layer; The second release protection layer has a four-layer structure, which includes, from bottom to top, a mixed layer of silicon oxynitride and silicon oxide, a silicon oxide layer, a silicon oxynitride layer, and a silicon oxide layer.

2. The infrared MEMS bridge column structure according to claim 1, characterized in that: In the area outside the bridge column structure, there is also a MEMS structure formed by other multiple film layers, and the layers outside the bridge column structure area include a substrate, a metal reflective layer, a dielectric layer, a release layer, a first release protection layer, a photosensitive layer, a metal electrode, a DARC layer and a second release protection layer; The first release protection layer is deposited on the release layer and is located on the dielectric layer together; The photosensitive layer is deposited on the first release protection layer; The DARC layer is deposited on the metal electrode; The second release protection layer is deposited on the DARC layer.

3. The infrared MEMS bridge column structure according to claim 2, characterized in that: The substrate is a silicon substrate, which is a circuit substrate used to read infrared sensor signals.

4. The infrared MEMS bridge column structure according to claim 2, characterized in that: The metal reflective layer is a metal film with high reflectivity, and the material is gold, silver, aluminum or copper, or a mixture of several of these materials.

5. The infrared MEMS bridge column structure according to claim 2, characterized in that: The dielectric layer, the first release protection layer and the DARC layer are all electrical insulating layers, and the materials are one or more of silicon dioxide, silicon nitride, silicon oxynitride and silicon carbide; or one or more of silicon nitride and silicon oxynitride in non-stoichiometric ratio.

6. The infrared MEMS bridge column structure according to claim 2, characterized in that: The photosensitive layer material is an infrared absorbing amorphous silicon material.

7. The infrared MEMS bridge column structure according to claim 2, characterized in that: The metal electrode is made of a metal film with a Ti / TiN structure.

8. The infrared MEMS bridge column structure according to claim 2, characterized in that: Also includes support hole areas.

9. A process for a bridge column structure of an infrared MEMS, characterized in that: The method comprises: Step 1, forming a metal reflective layer on a semiconductor substrate, depositing a sacrificial layer and patterning it after patterning; Step 2, depositing a first release protection layer and a photosensitive layer as a whole; Step 3, patterning the photosensitive layer; Step 4, in the support hole area outside the bridge column, patterning the membrane layer in the support hole area; Step 5, overall deposition to form a metal electrode film; Step 6, overall deposition to form a DARC film and patterning; Step seven, etching the metal electrode film layer; Step eight, depositing a second release protection layer film to pattern the bridge column structure area; the second release protection layer is a four-layer structure, which is, from bottom to top, a mixed layer of silicon oxynitride and silicon oxide, a silicon oxide layer, a silicon oxynitride layer, and a silicon oxide layer; Step nine, patterning the contact PAD area.

10. The process for the infrared MEMS bridge column structure according to claim 9, characterized in that: The semiconductor substrate is a circuit substrate used to read infrared sensor signals.

11. The process for the infrared MEMS bridge column structure according to claim 10, characterized in that: The semiconductor substrate is a silicon substrate.

12. The process for the infrared MEMS bridge column structure according to claim 9, characterized in that: The bridge column structure includes a first release protection layer, a metal layer and a second release protection layer.

13. The process for the infrared MEMS bridge column structure according to claim 12, characterized in that: The first release protection layer is a silicon oxide layer, the metal layer is a Ti / TiN layer, and the second release protection layer is a composite layer formed by a mixed layer of silicon oxynitride and silicon oxide, a silicon oxide layer, a silicon oxynitride layer, and a silicon oxide layer.

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