CN107799392B - Black silicon, preparation process and preparation method of MEMS device based on black silicon - Google Patents

Black silicon, preparation process and preparation method of MEMS device based on black silicon Download PDF

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CN107799392B
CN107799392B CN201710871041.1A CN201710871041A CN107799392B CN 107799392 B CN107799392 B CN 107799392B CN 201710871041 A CN201710871041 A CN 201710871041A CN 107799392 B CN107799392 B CN 107799392B
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silicon
black silicon
polymer layer
substrate
nano
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CN107799392A (en
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毛海央
杨宇东
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Institute of Microelectronics of CAS
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Institute of Microelectronics of CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02524—Group 14 semiconducting materials
    • H01L21/02532—Silicon, silicon germanium, germanium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
    • B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
    • B81C1/00349—Creating layers of material on a substrate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02587—Structure
    • H01L21/0259—Microstructure
    • H01L21/02592—Microstructure amorphous
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02587—Structure
    • H01L21/0259—Microstructure
    • H01L21/02595—Microstructure polycrystalline
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02587—Structure
    • H01L21/0259—Microstructure
    • H01L21/02598—Microstructure monocrystalline

Abstract

The present disclosure provides a black silicon preparation process, comprising: forming a polymer layer on a substrate; removing the polymer layer, and forming a nano forest structure on the initial position of the polymer layer by using a product in the process of removing the polymer layer; and depositing a silicon film material layer on the nano forest structure to finish the preparation of the black silicon. The disclosure also provides black silicon prepared by the black silicon preparation process and a preparation method of the black silicon-based MEMS device. The black silicon with higher light absorption capacity is prepared by adopting the black silicon preparation process with low process cost, wide popularity and adaptability, and the preparation method of the MEMS device based on the black silicon avoids the black silicon from being corroded and damaged in the release process of the MEMS device.

Description

Black silicon, preparation process and preparation method of MEMS device based on black silicon
Technical Field
The disclosure belongs to the field of nanotechnology, and particularly relates to black silicon, a preparation process and a preparation method of an MEMS device based on the black silicon.
Background
Black silicon is a forest-like large area nano-pillar/needle structure that has been considered as a revolutionary new material in the electronics industry. Compared with the traditional silicon material, the black silicon has extremely high absorption efficiency on light from visible light to near infrared bands. The methods for preparing black silicon proposed at present are various, and include high-energy femtosecond laser-assisted etching, metal-catalyzed electrochemical corrosion, plasma dry etching and the like. The method for preparing black silicon by using the plasma dry etching technology is most commonly used in the conventional semiconductor process due to the comprehensive consideration of multiple aspects such as processing cost, process convenience, process compatibility and the like, but the method is dependent on the preparation of a nanometer mask, or a high-energy injection process, or other special process treatment, and the process complexity is higher. Meanwhile, the black silicon prepared by the method is limited in height due to the capabilities of a thin film deposition process and an etching process, so that the light absorption capability of the black silicon is limited to a certain extent.
At present, there is a method for improving the performance of the MEMS device by using black silicon as a light absorption layer material: after forming a basic structure (comprising a medium supporting film, a signal conversion structure, a metal connection structure and the like) of the MEMS device, depositing and growing an alpha-Si or Poly-Si layer on the surface by a Plasma Enhanced Chemical Vapor Deposition (PECVD) technology, carrying out high-energy ion implantation on the alpha-Si or Poly-Si layer, then carrying out incomplete dry etching, further processing the alpha-Si or Poly-Si layer into black silicon, patterning the black silicon at the position of an absorption region, and finally releasing the device structure. In the method, incomplete etching is utilized for manufacturing the black silicon, so that the controllability of the structure and the size parameters of the black silicon is lower; and high-energy ion implantation of the silicon material layer is required to introduce defects before the preparation of black silicon, thus increasing the complexity of the process. In addition, after the PECVD alpha-Si or Poly-Si layer is formed, the technical idea of leading black silicon and releasing the black silicon is adopted, so that the black silicon is strictly protected from being damaged in the structure releasing process. However, the black silicon still has the physical and chemical properties of the silicon material, and is therefore easily damaged by corrosive gas or corrosive liquid in the subsequent release process; and because the nano structure in the black silicon has a certain height and larger density, the effective protection effect can not be realized by adopting a conventional method, such as film deposition protection or gluing protection.
Disclosure of Invention
Technical problem to be solved
In view of the technical problems, the present disclosure provides a black silicon, a preparation process and a preparation method of a black silicon-based MEMS device, wherein a novel black silicon preparation process is developed to prepare a black silicon with higher light absorption capability by combining a shape-preserving deposition method of a silicon thin film material layer after a nano forest structure is formed on a substrate based on a plasma repolymerization technology; on the basis, a preparation method of the black silicon-based MEMS device is developed by utilizing the compatibility between a plasma repolymerization technology, a silicon film deposition process and a conventional micromachining process.
(II) technical scheme
According to one aspect of the present disclosure, there is provided a black silicon preparation process, including: forming a polymer layer on a substrate; removing the polymer layer, and forming a nano forest structure on the initial position of the polymer layer by using a product in the process of removing the polymer layer; and depositing a silicon film material layer on the nano forest structure to finish the preparation of the black silicon.
In some embodiments of the disclosure, a layer of silicon thin film material is deposited on the nano-forest structures using a low pressure chemical vapor deposition process or a plasma enhanced chemical vapor deposition process.
In some embodiments of the present disclosure, the material of the silicon thin film is polysilicon, single crystal silicon, or amorphous silicon.
In some embodiments of the present disclosure, the thickness of the silicon thin film material layer is 10 to 500 nm.
In some embodiments of the present disclosure, the step of removing the polymer layer and forming a nano forest structure on the initial position of the polymer layer using a product of the process of removing the polymer layer includes: removing the polymer layer by using a plasma bombardment method; removing the product in the process of the polymer layer to form a nano forest structure on the initial position of the polymer layer by a plasma repolymerization technology; the nano forest structure comprises a nano wire forest structure or a nano fiber forest structure.
In some embodiments of the present disclosure, the nano-forest structure comprises a plurality of structural monomers, and the aspect ratio of the structural monomers is 2: 1 to 500: 1.
According to another aspect of the present disclosure, there is provided a black silicon formed using the black silicon preparation process of any one of claims 1 to 6.
In some embodiments of the present disclosure, the diameter of the single nanostructure in the black silicon is 50-800 nm, the height is 50 nm-20 um, and the density is 5-40/um2。
According to another aspect of the present disclosure, there is provided a method for manufacturing a black silicon-based MEMS device, including: arranging an MEMS sensor base structure on a substrate, and then arranging an MEMS sensor sensitive structure on the MEMS sensor base structure; forming a polymer layer on the MEMS sensor sensitive structure; corroding the substrate to form a back corrosion cavity of the MEMS sensor; removing the polymer layer, and forming a nano forest structure on the initial position of the polymer layer by using a product in the process of removing the polymer layer; and depositing a silicon film material layer on the nano forest structure to form black silicon on the sensitive structure of the MEMS sensor.
In some embodiments of the present disclosure, the step of etching the substrate to form a backside etch cavity of the MEMS sensor includes: carrying out front side corrosion release on the substrate by using front side dry corrosion to form a back side corrosion cavity of the MEMS sensor; or back side wet etching or back side dry etching is used for carrying out back side etching release on the substrate to form a back side etching cavity of the MEMS sensor; and protecting the MEMS sensor base structure, the MEMS sensor sensitive structure and the polymer layer before the step of performing back etching release on the substrate by using back wet etching or back dry etching.
(III) advantageous effects
According to the technical scheme, the black silicon, the preparation process and the preparation method of the MEMS device based on the black silicon have at least one of the following beneficial effects:
(1) the preparation process of the black silicon mainly comprises three steps: the polymer layer is arranged, the nano forest structure is prepared, and the silicon film material layer is deposited in a shape-retaining manner, the parallel preparation processes belong to the parallel preparation process, the rapid large-area batch processing can be realized, the process cost is low, all raw materials and equipment related to the process are common materials and equipment in the semiconductor process, and the process is wide in popularity and applicability;
(2) compared with the film process of depositing a silicon film material layer on a substrate and etching the silicon film material layer to form black silicon in the prior art, the black silicon prepared by the method has the height of several microns or even dozens of microns, and the light absorption capacity of the black silicon is improved;
(3) in the preparation method of the MEMS device based on the black silicon, a method of releasing first and black silicon second is adopted, namely, the substrate is corroded and released first, then the black silicon is formed, and the black silicon is prevented from being corroded and damaged in the releasing process;
(4) the preparation of the black silicon and the preparation of the MEMS device based on the black silicon do not relate to the use of metal nano particles, and then metal pollution is not introduced into the black silicon and the MEMS device; and the preparation process of the black silicon does not involve the use of a liquid environment, so that the damage of the liquid environment to the black silicon structure is avoided.
Drawings
Fig. 1 is a schematic cross-sectional structure diagram of a substrate in a first embodiment of the present disclosure.
Fig. 2 is a schematic cross-sectional structure of a polymer layer formed on a substrate in a first embodiment of the present disclosure.
Fig. 3 is a schematic cross-sectional structure diagram of a nano-forest structure formed on a substrate in a first embodiment of the disclosure.
Fig. 4 is an sem (scanning Electron microscope) image of the nano forest structure in the first embodiment of the disclosure.
Fig. 5 is a schematic cross-sectional structure diagram of a silicon film deposited on a nano forest structure to form black silicon in a first embodiment of the disclosure.
Fig. 6 is a schematic cross-sectional view illustrating a selective removal of a silicon thin film to form patterned black silicon in a first embodiment of the present disclosure.
Fig. 7 is an SEM picture of black silicon in the first embodiment of the present disclosure.
Fig. 8 is a schematic cross-sectional structure diagram of a MEMS sensor base structure and a MEMS sensor sensitive structure formed on a substrate according to a second embodiment of the disclosure.
Fig. 9 is a schematic cross-sectional structure diagram of a polymer layer formed on a sensitive structure of a MEMS sensor according to a second embodiment of the present disclosure.
Fig. 10a is a schematic cross-sectional view illustrating a backside etching cavity formed after a backside wet etching is performed to release the backside etching on the MEMS sensor according to a second embodiment of the disclosure.
Fig. 10b is a schematic cross-sectional structure diagram of a backside etching cavity formed after a backside etching release is performed on the MEMS sensor by using a backside dry etching in the second embodiment of the disclosure.
Fig. 11 is a schematic cross-sectional structure diagram of a nano forest structure formed on a released MEMS sensor sensitive structure in a second embodiment of the present disclosure.
Fig. 12a is a schematic cross-sectional structure diagram of a second embodiment of the present disclosure after a silicon thin film material layer is deposited on a nano forest structure to form black silicon, wherein the MEMS sensor release adopts backside wet etching.
Fig. 12b is a schematic cross-sectional structure diagram after a silicon thin film material layer is deposited on the nano forest structure to form black silicon in the second embodiment of the disclosure, wherein the MEMS sensor release adopts backside dry etching.
FIG. 13 is a schematic cross-sectional view of a front side corrosion release hole formed in a polymer layer, a MEMS sensor sensitive structure, and a MEMS sensor base structure according to a third embodiment of the present disclosure.
Fig. 14 is a schematic cross-sectional structure diagram of a back-side etching cavity formed after releasing the substrate by front-side dry etching in the third embodiment of the disclosure.
Fig. 15 is a schematic cross-sectional structure diagram of a nano forest structure formed on a sensitive structure of a MEMS sensor according to a third embodiment of the present disclosure.
Fig. 16 is a schematic cross-sectional structure diagram of a third embodiment of the disclosure after a silicon thin film material layer is deposited on a nano forest structure to form black silicon.
[ notation ] to show
101, 102-a substrate;
201-a polymer layer;
301, 302-nano forest structures;
401, 402-a layer of silicon thin film material;
103-sensor infrastructure;
104-a sensor sensitive structure;
105, 106, 502-backside etch chamber;
501-front corrosion relief holes.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
It should be noted that in the drawings or description, the same drawing reference numerals are used for similar or identical parts. Implementations not depicted or described in the drawings are of a form known to those of ordinary skill in the art. Additionally, while exemplifications of parameters including particular values may be provided herein, it is to be understood that the parameters need not be exactly equal to the respective values, but may be approximated to the respective values within acceptable error margins or design constraints. Directional phrases used in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., refer only to the direction of the attached drawings and are not intended to limit the scope of the present disclosure.
First, first embodiment
The invention provides a black silicon preparation process, which comprises the following steps:
step A1: as shown in fig. 1, a substrate 101 is provided.
Further, the substrate comprises silicon, glass, quartz, polymer; the substrate is not limited to the above four types, and may be any one of those commonly used in microelectronic processes. The substrate may be a4 inch, 6 inch, 8 inch, 12 inch wafer, as well as other substrate pieces of varying shapes and sizes suitable for use in microfabrication processes.
In this example, a 4-inch single crystal silicon substrate was used.
Step A2: a polymer layer 201 is formed on the substrate 101.
Further, the material of the polymer layer comprises photoresist, polydimethylsiloxane, parylene, polyethylene, polycarbonate, and other polymer layer materials which can be removed by a plasma bombardment method;
the polymer layer may be disposed on the substrate 101 by spraying, spin coating, pasting, stamping, curing, or the like, and the polymer layer may completely cover the substrate or may be further patterned.
In the embodiment, the polymer layer is made of polyimide photoresist, and the polyimide photoresist is arranged on the silicon substrate by adopting a spin-coating method; further, this embodiment forms a patterned polymer layer on the substrate, as shown in fig. 2.
More specifically, step a2 includes the following sub-steps:
substep A21: arranging a polymer layer on a 4-inch wafer silicon substrate by adopting a spin coating method, and baking the wafer substrate on a 120-degree hot plate for 20 minutes after the spin coating;
further, in the spin coating process, the adopted rotating speed is 3000rpm, the spin coating time is 30s, and the thickness of the polyimide photoresist layer is about 5 um;
substep A22: exposing the polyimide photoresist;
further, the wavelength of ultraviolet light adopted during exposure is 365nm, the exposure time is 80s, and the exposure dose is 6 mJ/s;
substep A23: after exposure, the wafer is placed in a CD26 developing solution for development, and the development time is 38 s;
substep A24: after developing, placing the patterned wafer in an oxygen plasma degumming machine for carrying out base film scanning treatment for 7min, and removing the polyimide photoresist film layer remained at the position except the pattern;
further, when the basement membrane sweeping treatment is carried out, the oxygen pressure is 0.48Pa, the forward power of the equipment is 500W, the reverse power is 0W, and the temperature is 70 ℃;
substep A25: and (3) placing the wafer in an oven at 140 ℃ for post-baking for 40min, and hardening to form a patterned polymer layer.
Step A3: the polymer layer is completely removed and the nano forest structures 301 are formed in the initial positions of the polymer layer using the products of the process of removing the polymer layer.
Further, in step a3, a plasma bombardment method is used to achieve complete removal of the polymer layer; and forming a nano forest structure on the initial position of the polymer layer on the substrate by using a plasma repolymerization technology through partial products in the process of removing the polymer layer.
Further, the plasma bombardment comprises respective bombardment treatment of oxygen plasma, argon plasma and nitrogen plasma and alternate bombardment after combination of every two, when the polymer layer is bombarded by the plasma, the radio frequency power is 50-500W, the gas flow is 10-200sccm, and the bombardment time is 2-200 min. The present disclosure is not limited to the three plasmas described above, but can also be other plasmas capable of bombarding a polymer layer.
Further, the nano forest structure is a large-area one-dimensional nano structure, and the nano forest structure comprises a nano wire forest structure or a nano fiber forest structure;
in this embodiment, an oxygen plasma is first used for bombardment, the oxygen flow is 50sccm, the power is 200W, and the treatment time is 9min, and then an argon plasma is used for treatment, the argon flow is 20sccm, the power is 200W, and the treatment time is 25 min.
Further, the nano forest structure comprises a plurality of structural monomers, and the length-diameter ratio of the structural monomers is 2: 1-500: 1; the structural monomer refers to a single nano structure in a nano forest structure, namely a single nanowire or a single nanofiber. Fig. 3 and 4 are a schematic cross-sectional structure and sem (scanning Electron microscope) images of the nano forest structure in the first embodiment.
Step A4: a layer of silicon thin film material 401 is deposited over the nano-forest structure 301.
Furthermore, the material of the silicon film material layer comprises polycrystalline silicon, monocrystalline silicon and amorphous silicon, the thickness of the silicon film material layer is 10-500nm, the thickness of the silicon film material layer is influenced by the height and the density of the nanometer forest structure, and meanwhile, the thickness of the silicon film material layer is determined by the process parameters of depositing the silicon film material layer.
The method for depositing the silicon thin film material layer comprises Low Pressure Chemical Vapor Deposition (LPCVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD).
In this embodiment, as shown in fig. 5, an amorphous silicon thin film material layer is deposited on the nano forest structure by using a PECVD method. In the deposition process of the amorphous silicon thin film material layer, the temperature of the cavity is 150-350 ℃, the pressure of the cavity is 5-50Pa, the radio frequency power is 5-20W, and the flow rate of silane is 1-50 sccm. In this embodiment, the chamber temperature is 240 ℃, the pressure is 30Pa, the power is 10W, and the flow rate of the silane gas is 5 sccm.
And in the process of depositing the amorphous silicon thin film material layer, a side wall process is utilized to surround an amorphous silicon side wall material layer outside the nano forest structure. And a relatively compact silicon film is formed on the surface of the nano forest structure by completely covering the nano forest structure with the silicon film material layer. In the disclosure, the silicon film material layer deposited on the surface of the nano forest structure has good shape-keeping performance, namely, the silicon film completely wraps the nano forest structure at any height position to form a good black silicon structure.
The preparation process of the black silicon disclosed by the invention relates to three main steps: the three steps of the setting of the polymer layer, the preparation of the nano forest structure and the shape-retaining deposition of the silicon film material layer belong to a parallel preparation process, the process method is extremely simple, the rapid large-area batch processing can be realized, the process cost is low, all raw materials and equipment related to the process are common materials and equipment in the semiconductor process, and the process is wide in popularity and applicability.
In addition, in the disclosure, if the polymer layer completely covers the substrate, after the silicon thin film material layer is deposited, a black silicon structure is formed on the whole surface of the substrate; in this embodiment, since the patterned polymer layer is formed on the substrate, after the silicon thin film material layer is deposited, the substrate not covered by the polymer layer, i.e. the position outside the nano forest structure pattern, will be directly covered by the silicon thin film material layer. Therefore, the silicon thin film material layer outside the black silicon region can be selectively removed, and the patterned black silicon can be obtained, as shown in fig. 6.
Furthermore, the original graphical nano forest structure is a supporting framework of the silicon thin film material layer, and after the amorphous silicon thin film material layer is deposited, the black color of the position can be observed in a visible light range, namely the graphical black silicon is obtained at the position. And the positions outside the nano forest structure pattern are only covered with a layer of silicon film material, and the specific color matched with the thickness of the silicon film material is presented, so that the selectivity of the optical characteristics is formed inside and outside the patterned black silicon. This feature can be exploited to achieve entirely new functionality of the sensor for a particular optical MEMS sensor.
FIG. 7 is an SEM image of black silicon prepared in this embodiment, in which the diameter of a single nanostructure in the black silicon prepared according to the present disclosure is 50-800 nm, the height is 50 nm-20 um, and the distribution density of the black silicon is 5-40/um2(ii) a The single nanostructure in the black silicon is a unit of nanostructures in the black silicon, such as a single nanopillar as shown in fig. 7. ByThe height of a single nano structure in the black silicon is 50 nm-20 um, and the height of the black silicon prepared by the method can reach several microns or even dozens of microns, so the black silicon prepared by the method has better light absorption characteristic, and the preparation process of the black silicon does not involve the use of a liquid environment, thereby avoiding the damage of the liquid environment to the black silicon structure.
Second and third embodiments
The present disclosure provides a method for preparing a black silicon-based MEMS sensor, comprising the steps of:
step B1: providing a substrate 102;
further, the material of the substrate 102 is selected in the same way as the material of the substrate 101 in the first embodiment.
Step B2: as shown in fig. 8, a MEMS sensor infrastructure 103 is provided on a substrate 102, and then a MEMS sensor sensitive structure 104 is provided on the MEMS sensor infrastructure 103.
Furthermore, the MEMS sensing device is generally provided with a sensor base structure and a sensor sensitive structure, wherein the sensor sensitive structure is configured to sense a physical quantity to be measured and output a physical quantity signal having a certain relationship with the measured physical quantity; the sensor infrastructure converts the physical quantity signals output by the sensor sensitive structure into information in a desired form.
In the embodiment, the MEMS sensor is selected as a thermopile MEMS infrared sensing device, wherein the sensor base structure comprises a thermocouple series connection structure, and the sensor sensitive structure is a silicon nitride film material layer; the silicon nitride film material layer is used for absorbing infrared radiation and converting the infrared radiation into heat, and the heat output by the sensor sensitive structure causes the temperature difference at two ends of the thermocouple series structure, so that the generation of thermoelectromotive force is caused.
Step B3: as shown in fig. 9, a polymer layer 201 is disposed on the sensor sensitive structure.
Further, the process and method of step B3 are similar to those of step a2 in the first embodiment.
In the embodiment, a polymer layer is arranged on the silicon nitride film material layer by adopting spin coating (including spin coating and pre-baking) and photoetching (including exposure, development and post-baking) processes;
step B4: and carrying out back side corrosion release on the substrate 102 of the MEMS sensor to form a back side corrosion cavity of the MEMS sensor.
Furthermore, the MEMS sensor device may form a backside etching cavity on the substrate by backside wet etching or backside dry etching, or may use other methods capable of performing backside etching release on the MEMS sensor substrate to form the backside etching cavity. Fig. 10a and 10b are schematic cross-sectional structural diagrams of the substrate 102 subjected to backside wet etching and backside dry etching to release backside etching to form backside etching cavities 105 and 106, respectively.
In this embodiment, the substrate 102 of the sensor is subjected to back etching release by using a back potassium hydroxide (KOH) wet etching method and a back deep silicon etching (DRIE) method, respectively. Before KOH wet etching, the front structure of the MEMS sensor is protected so as to prevent the front base structure, sensitive structure and polymer layer of the MEMS sensor from being damaged by etching liquid in the etching process. Similarly, when performing deep back silicon etching, proper protection of the front side structure is also required.
Further, for the KOH wet etch: after the polymer layer is arranged on the silicon nitride film material layer, patterning of a back side corrosion cavity opening is carried out on the back side of the wafer substrate by utilizing a double-side registration photoetching process, then front side protection is carried out on the polymer layer pattern, the wafer is placed in KOH corrosive liquid for back side corrosion release, and after the wafer is corroded to a sensor base structure, corrosion is automatically stopped.
For the back deep silicon etching process: when back corrosion release is carried out, etching is stopped on the sensor basic structure layer through etching time and reaction gas monitoring.
Step B5: as shown in fig. 11, after the front protection device is removed, the polymer layer is removed by using a plasma bombardment method, and a nano forest structure 302 is formed on an initial position of the polymer layer by using a product of the process of removing the polymer layer.
Step B6: a layer of silicon film material is deposited on the nano forest structure 302, forming black silicon on the MEMS sensor sensitive structure.
Further, fig. 12a and 12b are schematic cross-sectional structural diagrams after a silicon thin film material layer is deposited on the nano forest structure in the second embodiment of the present disclosure, and the difference between the two is that the sensor in fig. 12a is released by using a back wet etching, and the sensor in fig. 12b is released by using a back dry etching. Referring to fig. 12a and 12b, after depositing the silicon thin film material layer, the silicon thin film material layer 402 is selectively removed to obtain the patterned black silicon.
Further, the methods of step B5 and step B6 are the same as those of step A3 and step a4 in the first embodiment.
Through the process treatment, the preparation of the MEMS device based on the black silicon is realized.
Third and fourth embodiments
The difference between the method for manufacturing a black silicon-based MEMS device provided in this embodiment and the second embodiment is that the present embodiment uses a front release process to etch a substrate to form a backside etching cavity of a MEMS sensor, and the method includes the following steps:
steps C1-C3 are the same as steps B1-B3.
Step C4: as shown in fig. 13, front side corrosion release holes 501 are provided in the polymer layer, the sensor sensitive structure, and the sensor base structure.
Further, the front-side corrosion release hole is formed by a photolithography or etching process, and the front-side corrosion release hole penetrates through the patterned polymer layer, the sensor sensitive structure, and the sensor base structure, and is connected to the substrate 102.
Step C5: as shown in fig. 14, the substrate 102 is subjected to front-side etching release by front-side dry etching to form a back-side etching cavity 502 of the MEMS device.
In the embodiment, the substrate is subjected to front-side corrosion release by using xenon fluoride gas, and the substrate can also be subjected to corrosion release by using other corrosive gases; the front-side etching release of the substrate means that the wafer is placed in a xenon fluoride gas cavity, and in the etching process, the xenon fluoride gas is contacted with the substrate 102 through the front-side etching release holes to gradually etch the substrate 102. With the progress of the corrosion process, forming a hemispherical release small cavity below each corrosion release hole; during the continuous corrosion release process, the individual hemispherical release sub-cavities are interconnected to form a continuous backside corrosion cavity 502 under the sensor infrastructure layer.
In this embodiment, the release depth is about 20 microns, and the distance between the release holes is comparable to the release depth, which is provided to prevent the spacing between the release holes from being too large, resulting in incomplete release locations between the release holes, which can cause the MEMS sensor to fail.
Further, the release depth and the distance between the release holes are not limited to 20 micrometers, the size of the release holes is related to the release depth, a hemispherical structure is formed during release, and as long as all the hemispherical release small cavities are connected in pairs after release to form a continuous cavity, the implementation of the disclosure is not affected.
Step C6: as shown in fig. 15, the polymer layer is removed by using a plasma bombardment method, and a nano forest structure 302 is formed on an initial position of the polymer layer by using a product of the process of removing the polymer layer.
Furthermore, the front corrosion to the substrate is released before the nano forest structure is formed, the nano forest structure does not need to be specially protected, and the black silicon is prevented from being corroded and damaged.
Step C7: as shown in fig. 16, a layer of silicon thin film material is deposited on the nano-forest structure, forming black silicon.
Through the process treatment, the preparation of the MEMS device based on the black silicon is realized.
Further, in the second and third embodiments, the front-side etch release and the back-side etch release refer to etching the released MEMS device from the upper and lower surfaces of the substrate, respectively; the back corrosion cavity of the MEMS device means that the finally formed cavity is on the back of the MEMS device no matter the front corrosion is released or the back corrosion is released.
In the present disclosure, the MEMS sensor is not limited to the optical sensor in the embodiment, since the black silicon may also exhibit many other characteristics, including super-hydrophobicity (self-cleaning function), surface enhancement characteristics, molecular surface adsorption characteristics, field emission, etc., and may be applied to other MEMS devices according to different characteristics exhibited by the black silicon in different directions.
In the preparation method of the MEMS device based on the black silicon, a method of 'releasing first and black silicon second' is adopted, namely, the substrate is corroded first, then the black silicon is formed, and the black silicon is prevented from being corroded and damaged in the releasing process.
Further, the preparation of black silicon and the preparation of black silicon-based MEMS devices in this disclosure do not involve the use of metal nanoparticles, which in turn does not introduce metal contamination in the MEMS device.
Up to this point, the present embodiment has been described in detail with reference to the accompanying drawings. From the above description, those skilled in the art should have clear understanding of the black silicon, the fabrication process, and the method for fabricating the black silicon-based MEMS device according to the present disclosure.
It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. Further, the above definitions of the various elements and methods are not limited to the various specific structures, shapes or arrangements of parts mentioned in the examples, which may be modified or substituted by one of ordinary skill in the art.
It is also noted that the illustrations herein may provide examples of parameters that include particular values, but that these parameters need not be exactly equal to the corresponding values, but may be approximated to the corresponding values within acceptable error tolerances or design constraints. Directional phrases used in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., refer only to the direction of the attached drawings and are not intended to limit the scope of the present disclosure.
The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.

Claims (10)

1. A black silicon preparation process comprises the following steps:
forming a polymer layer on a substrate;
removing the polymer layer, and forming a nano forest structure on the initial position of the polymer layer by using a product in the process of removing the polymer layer; and
and depositing a silicon film material layer on the nano forest structure to form a layer of relatively dense silicon film on the surface of the nano forest structure to finish the preparation of the black silicon.
2. The black silicon production process of claim 1, wherein a layer of silicon thin film material is deposited on the nano forest structure using a low pressure chemical vapor deposition method or a plasma enhanced chemical vapor deposition method.
3. The black silicon preparation process of claim 1, wherein the material of the silicon thin film is polycrystalline silicon, monocrystalline silicon or amorphous silicon.
4. The black silicon preparation process of claim 1, wherein the thickness of the silicon thin film material layer is 10-500 nm.
5. The black silicon manufacturing process according to claim 1, wherein the step of removing the polymer layer and forming a nano forest structure on the initial position of the polymer layer using a product of the process of removing the polymer layer comprises:
removing the polymer layer by using a plasma bombardment method;
removing the product in the process of the polymer layer to form a nano forest structure on the initial position of the polymer layer by a plasma repolymerization technology; the nano forest structure comprises a nano wire forest structure or a nano fiber forest structure.
6. The black silicon preparation process of claim 1, wherein the nano forest structure comprises a plurality of structural monomers, and the aspect ratio of the structural monomers is 2: 1-500: 1.
7. A black silicon formed by the black silicon manufacturing process as set forth in any one of claims 1 to 6.
8. The black silicon of claim 7, wherein the diameter of the individual nanostructures in the black silicon is 50-800 nm, the height is 50 nm-20 um, and the density is 5-40/um2。
9. A preparation method of a black silicon-based MEMS device comprises the following steps:
arranging an MEMS sensor base structure on a substrate, and then arranging an MEMS sensor sensitive structure on the MEMS sensor base structure;
forming a polymer layer on the MEMS sensor sensitive structure;
corroding the substrate to form a back corrosion cavity of the MEMS sensor;
removing the polymer layer, and forming a nano forest structure on the initial position of the polymer layer by using a product in the process of removing the polymer layer; and
and depositing a silicon film material layer on the nano forest structure to form a layer of relatively dense silicon film on the surface of the nano forest structure, and forming black silicon on the MEMS sensor sensitive structure.
10. The method of fabricating a black silicon based MEMS device of claim 9, wherein the step of etching the substrate to form the backside etch cavity of the MEMS sensor comprises:
carrying out front side corrosion release on the substrate by using front side dry corrosion to form a back side corrosion cavity of the MEMS sensor; or
Carrying out back side corrosion release on the substrate by using back side wet corrosion or back side dry corrosion to form a back side corrosion cavity of the MEMS sensor; and protecting the MEMS sensor base structure, the MEMS sensor sensitive structure and the polymer layer before the step of performing back etching release on the substrate by using back wet etching or back dry etching.
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