MEMS structure and processing method thereof, pyroelectric sensor and infrared detector
阅读说明：本技术 Mems结构及其加工方法、热释电传感器、红外探测器 (MEMS structure and processing method thereof, pyroelectric sensor and infrared detector ) 是由 石少伟 武军伟 梁自克 于 2019-11-06 设计创作，主要内容包括：本发明公开了一种MEMS结构及其加工方法、热释电传感器、红外探测器,属于MEMS技术及红外探测技术领域。该MEMS结构包括设有读出集成电路的基底,以及包括：悬浮在基底一侧的热敏感层,所述的热敏感层为镧钛酸铅铁电薄膜；用于支撑所述热敏感层的支撑结构,所述支撑结构通过若干组锚柱与所述基底相连,所述支撑结构与所述基底之间形成光学谐振腔；所述的支撑结构依次包括第一碳化硅层、电极层以及第二碳化硅层；所述的电极层为钛膜和/氮化钛膜。本发明通过采用镧钛酸铅铁电薄膜作为热敏感层,以及使热敏感层通过支撑结构悬浮在基底一侧,可以提高MEMS结构的光学吸收特性以及降低MEMS结构的噪声等效温差。(The invention discloses an MEMS structure and a processing method thereof, a pyroelectric sensor and an infrared detector, and belongs to the technical field of MEMS technology and infrared detection. The MEMS structure includes a substrate provided with a readout integrated circuit, and includes: the thermal sensitive layer is suspended on one side of the substrate and is a lanthanum lead titanate ferroelectric film; the supporting structure is used for supporting the heat sensitive layer and is connected with the substrate through a plurality of groups of anchor posts, and an optical resonant cavity is formed between the supporting structure and the substrate; the support structure sequentially comprises a first silicon carbide layer, an electrode layer and a second silicon carbide layer; the electrode layer is a titanium film and/or a titanium nitride film. The invention adopts the lanthanum lead titanate ferroelectric film as the heat sensitive layer, and the heat sensitive layer is suspended on one side of the substrate through the supporting structure, so that the optical absorption characteristic of the MEMS structure can be improved, and the noise equivalent temperature difference of the MEMS structure can be reduced.)
1. A MEMS structure comprising a substrate provided with a readout integrated circuit, further comprising:
the thermal sensitive layer is suspended on one side of the substrate and is a lanthanum lead titanate ferroelectric film;
the supporting structure is used for supporting the heat sensitive layer and is connected with the substrate through a plurality of groups of anchor posts, and an optical resonant cavity is formed between the supporting structure and the substrate; the support structure sequentially comprises a first silicon carbide layer, an electrode layer and a second silicon carbide layer; the electrode layer is a titanium film and/or a titanium nitride film.
2. A MEMS structure as claimed in claim 1 wherein said anchor posts are of tungsten.
3. A MEMS structure as claimed in claim 2, wherein the anchor posts are provided with a silicon oxide layer around their periphery.
4. A MEMS structure according to claim 1 wherein the substrate is further provided with a metallic reflective layer.
5. The MEMS structure of claim 4, wherein the metal reflective layer is an aluminum film.
6. A method of fabricating a MEMS structure according to any of claims 1 to 5, comprising the steps of:
spin-coating a polyimide film on a substrate to serve as a sacrificial layer, and depositing a silicon carbide protective film on the sacrificial layer by using a chemical vapor deposition method;
etching and punching the sacrificial layer and the silicon carbide protective film to obtain a plurality of groups of first pore channels;
depositing silicon oxide in the first pore channel by using a chemical vapor deposition method, and carrying out primary flattening on the sacrificial layer;
depositing a layer of silicon oxynitride protective film on the sacrificial layer after the first leveling by using a chemical vapor deposition method;
etching the silicon oxide in the silicon oxynitride protective film and the first pore channel to obtain a second pore channel filled with a silicon oxide layer, depositing tungsten in the second pore channel and carrying out secondary flattening on the sacrificial layer to form a plurality of groups of anchor columns corresponding to the second pore channel;
depositing a silicon carbide film on the second-time flattened sacrificial layer by using a chemical vapor deposition method, and etching the silicon carbide film on the anchor post to form a first silicon carbide layer;
depositing a titanium film and/or a titanium nitride film above the first silicon carbide layer by using a physical vapor deposition method, and etching the deposited titanium film and/or titanium nitride film to form an electrode layer of an interdigital electrode structure;
depositing a silicon carbide film over the electrode layer using a chemical vapor deposition process to form a second silicon carbide layer;
depositing a lanthanum lead titanate ferroelectric film above the second silicon carbide layer by using a chemical vapor deposition method;
etching the lanthanum lead titanate ferroelectric film to form a heat sensitive layer; etching the first silicon carbide layer, the electrode layer and the second silicon carbide layer to form a support structure;
and releasing the polyimide film in an oxygen environment by a dry method to form an optical resonant cavity, thereby obtaining the MEMS structure.
7. The method as claimed in claim 6, wherein the polyimide film has a thickness of 1-3 μm, the first silicon carbide layer has a thickness of 10-20 nm, the second silicon carbide layer has a thickness of 10-20 nm, and the lanthanum lead titanate ferroelectric thin film has a thickness of 120-180 nm.
8. A MEMS structure fabricated by the method of claim 6 or 7.
9. A pyroelectric sensor, characterized in that it comprises a MEMS structure as claimed in any one of claims 1 to 5 and 8.
10. An uncooled infrared detector, wherein the uncooled infrared detector comprises the pyroelectric sensor of claim 9.
Technical Field
The invention relates to the technical field of MEMS (micro-electromechanical systems) technology and infrared detection, in particular to an MEMS structure and a processing method thereof, a pyroelectric sensor and an infrared detector.
Background
Micro-Electro-Mechanical systems (MEMS), also called Micro-electromechanical systems, microsystems, micromachines, can be used to form pixel arrays or blind pixel structures of non-refrigerated infrared detectors and other detectors.
At present, most of MEMS structures adopted by the existing detectors adopt vanadium oxide and the like as materials, and generally only an anchor column is used as a support in the structure, the MEMS structure of the type has the problems of large noise equivalent temperature difference and the like, and the influence on the comprehensive performance of the detectors is large, so that the MEMS structure is not suitable for detectors such as uncooled infrared detectors and the like.
Disclosure of Invention
It is an object of the present invention to provide a MEMS structure to solve the above problems in the prior art.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
a MEMS structure comprising a substrate provided with a readout integrated circuit, and further comprising:
the thermal sensitive layer is suspended on one side of the substrate and is a lanthanum lead titanate ferroelectric film;
the supporting structure is used for supporting the heat sensitive layer and is connected with the substrate through a plurality of groups of anchor posts, and an optical resonant cavity is formed between the supporting structure and the substrate; the support structure sequentially comprises a first silicon carbide layer, an electrode layer and a second silicon carbide layer; the electrode layer is a titanium film and/or a titanium nitride film.
Preferably, the anchor post is made of tungsten.
Preferably, the periphery of the anchor post is provided with a silicon oxide layer.
Preferably, a metal reflecting layer is further arranged on the substrate.
Preferably, the metal reflecting layer is an aluminum film.
Another objective of the embodiments of the present invention is to provide a method for processing the MEMS structure, which includes the following steps:
spin-coating a polyimide film on a substrate to serve as a sacrificial layer, and depositing a silicon carbide protective film on the sacrificial layer by using a chemical vapor deposition method;
etching and punching the sacrificial layer and the silicon carbide protective film to obtain a plurality of groups of first pore channels;
depositing silicon oxide in the first pore channel by using a chemical vapor deposition method, and carrying out primary flattening on the sacrificial layer;
depositing a layer of silicon oxynitride protective film on the sacrificial layer after the first leveling by using a chemical vapor deposition method;
etching the silicon oxide in the silicon oxynitride protective film and the first pore channel to obtain a second pore channel filled with a silicon oxide layer, depositing tungsten in the second pore channel and carrying out secondary flattening on the sacrificial layer to form a plurality of groups of anchor columns corresponding to the second pore channel;
depositing a silicon carbide film on the second-time flattened sacrificial layer by using a chemical vapor deposition method, and etching the silicon carbide film on the anchor post to form a first silicon carbide layer;
depositing a titanium film and/or a titanium nitride film above the first silicon carbide layer by using a physical vapor deposition method, and etching the deposited titanium film and/or titanium nitride film to form an electrode layer of an interdigital electrode structure;
depositing a silicon carbide film over the electrode layer using a chemical vapor deposition process to form a second silicon carbide layer;
depositing a lanthanum lead titanate ferroelectric film above the second silicon carbide layer by using a chemical vapor deposition method;
etching the lanthanum lead titanate ferroelectric film to form a heat sensitive layer; etching the first silicon carbide layer, the electrode layer and the second silicon carbide layer to form a support structure;
and releasing the polyimide film in an oxygen environment by a dry method to form an optical resonant cavity, thereby obtaining the MEMS structure.
Preferably, in the step, the thickness of the polyimide film is 1-3 μm, the thickness of the first silicon carbide layer is 10-20 nm, the thickness of the second silicon carbide layer is 10-20 nm, and the thickness of the lanthanum lead titanate ferroelectric film is 120-180 nm.
Another object of the embodiments of the present invention is to provide a MEMS structure processed by the above processing method.
Another object of the embodiments of the present invention is to provide an application of the MEMS structure in a detector.
Another objective of the embodiments of the present invention is to provide a pyroelectric sensor, which includes the above MEMS structure.
Another object of an embodiment of the present invention is to provide an uncooled infrared detector, which includes the pyroelectric sensor.
Compared with the prior art, the embodiment of the invention has the beneficial effects that:
according to the MEMS structure provided by the embodiment of the invention, the lanthanum lead titanate ferroelectric film is used as the heat sensitive layer, and the heat sensitive layer is suspended on one side of the substrate through the supporting structure comprising the first silicon carbide layer, the electrode layer and the second silicon carbide layer, so that the optical absorption characteristic of the MEMS structure can be improved, and the noise equivalent temperature difference of the MEMS structure can be reduced.
Drawings
Fig. 1 is a schematic structural diagram of a MEMS structure provided in
Fig. 2 is a perspective view of the support structure and the heat-sensitive layer provided in example 1.
FIG. 3 is a graph of simulation analysis of optical absorption characteristics of the MEMS structure processed in example 6.
In the figure: 1-substrate, 2-heat sensitive layer, 3-support structure, 31-first silicon carbide layer, 32-electrode layer, 33-second silicon carbide layer, 4-anchor column, 5-silicon oxide layer, 6-metal reflecting layer and 7-optical resonant cavity.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.