RU2439741C1 - Method of making sensitive elements of micromechanical systems - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: method of making sensitive elements of micro-electromechanical systems (MEMS) involves applying protective coatings on front and back sides of a wafer, photolithography on the protective layers on the front and back sides, deep high-precision silicon etching on the front and back sides of the wafer at a given depth and with a given profile, removing remaining masking coatings from the front and back sides of the wafer. After etching moats on the front side and removing the remaining protective coating, an operation is performed to deposit onto the silicon wafer a silicon dioxide layer and a profile of etch moats, followed by etching on the back side of the wafer and mechanical fixation of falling out fragments of the structure. ^ EFFECT: reduced expenses on making MEMS elements compared to when using grown wafers and fewer process operations when making MEMS and high output of suitable elements. ^ 3 dwg

Description

A method of manufacturing sensitive elements of microelectromechanical systems (MEMS) of a given thickness, in the volume of the working plate or near the surface of one of its sides.

Analogues of the patented method are the technology of obtaining MEMS sensitive elements through the operation of doping silicon to create layers that prevent etching / 1 / or the use of two or more spliced plates through different connecting layers / 2 /. Such methods as the creation of highly alloyed regions have a number of significant drawbacks: the need to use expensive equipment to create highly alloyed regions in silicon, the additional costs of materials, and do not allow the formation of three-dimensional structures in the volume of the plate.

The closest in technical essence is a method of manufacturing an electromagnetic actuator / 3 /. Two spliced plates having a dielectric layer in the splicing zone are used for its manufacture. This allows the etching process from the front side to the dielectric layer to a precisely defined depth, and etching on the back side of the plate without etching the front side with the pattern already formed. The use of this method is associated with the need to use two fused working plates, one of which has to be thinned to a predetermined thickness of the future sensing element, which requires expensive equipment for combining and splicing the plates together. And this leads to an increase in the price of finished products and complication of the technological route for manufacturing sensitive MEMS elements.

The objective of the invention is to reduce the cost of manufacturing MEMS elements in comparison with the use of spliced plates and reducing the number of technological operations in the manufacture of MEMS and, as a result, increasing the yield coefficient of suitable products.

A method of manufacturing sensitive elements of microelectromechanical systems (MEMS), including the application of protective coatings on the front and back of the wafer, photolithography on the protective layers on the front and back of the wafer, high-precision etching of silicon from the front and back of the wafer to a predetermined depth and with a given profile, removal residues of masking coatings on the front and back sides of the wafer, characterized in that on the silicon wafer after etching the grooves on the front side and removing the remainder the protective coating is made of silica deposition operation layer for protecting the face of the plate and the profile of the etched grooves rastrava during subsequent etching from the reverse side of the plate and mechanical fixing constructions falling fragments.

A method of manufacturing MEMS sensitive elements contains a set of proven and widely used technological operations used to create a complex profile pattern on the surface of a silicon substrate, but after etching the front side of the substrate and forming grooves of a given profile and depth, the depth of the grooves will determine the final thickness of the MEMS element on the front a layer of silicon dioxide of sufficient thickness is applied to the side of the substrate, as to protect the front side of the plate and the side walls of the etched grooves (their profile), and for reliable fixation of falling out fragments in a suspended state. The thickness of the silicon dioxide layer is chosen in such a way as to provide reliable protection of the etched profile and the front side of the plate during subsequent operations, as well as to provide reliable mechanical fixation of the falling fragments and, at the same time, not to create difficulties when removing this layer after final etching from the back side plates - the final formation of the sensitive element. The operation of splicing the working plates and the operation of doping silicon to create a layer that stops etching is eliminated, replacing them with the operation of applying a layer of silicon dioxide, both to protect the side walls of the etched grooves and to hang out the etched fragments of the substrate, excluding their loss in the reactor and, as a result, elimination of reactor pollution and shutdown of the production process.

The process of splicing two substrates is a complex and responsible technological process requiring expensive equipment and rooms with a high class of cleanliness. In order to merge two plates, they must first be cleaned, applied to the surfaces that will be spliced, some auxiliary layer should be combined in the alignment unit along the base cut, spliced in the splicer, and then one of the plates should be thinned to the thickness that will be necessary for the sensing element. Since the elements can have different thicknesses, this means that for each type of sensitive elements you need to make a separate type of fused plates, differing in thickness, which greatly reduces the flexibility of this method. Using the method of applying a layer of silicon dioxide, we can form MEMS sensitive elements of various thicknesses using standard plates of the same thickness.

Figure 1 shows a silicon single crystal wafer with etched grooves and a deposited layer of silicon dioxide, where 1 is a silicon wafer; 2 - masking layer of the reverse side of the plate; 3 - grooves etched on the front side of the plate; 4 - a layer of silicon dioxide on the front side of the plate; 5 - a layer of silicon dioxide on the profile of the grooves.

Figure 2 presents a silicon wafer with etched grooves on the front and back sides, where 1 is a silicon wafer; 2 - masking layer of the reverse side of the plate; 3 - grooves etched on the front side of the plate; 4 - a layer of silicon dioxide on the front side of the plate; 5 - a layer of silicon dioxide on the profile of the grooves; 6 - grooves etched on the back of the plate; 7 - drop-down fragment held by a layer of silicon dioxide 5.

Figure 3 presents the final view of the sensitive element, after removing the falling fragments and protective coatings, where 1 is a silicon wafer; 3 - grooves etched on the front side of the plate; 6 - grooves etched on the back of the plate; 8 is the final view of the sensing element.

A method of manufacturing MEMS sensitive elements is as follows: a protective coating is applied to the front side of the wafer, photolithography is performed on the protective layer to create a pattern of future etching, an operation of deep high-precision plasma-chemical etching of silicon from the front of the wafer to a predetermined depth and with a given etching profile is carried out, and residues are removed a protective coating on the front side of the plate, apply a layer of silicon dioxide on the front side to protect the surface of the plate and the profile equal grooves on the front side, apply a protective coating to the back side of the plate and carry out photolithography on this protective layer, to create an etching pattern on the back side of the plate, perform the operation of deep high-precision plasma-chemical etching of silicon from the back side of the plate, bringing the sensitive element to a predetermined thickness, remove the remains of the protective mask on the back side of the plate, remove the layer of silicon dioxide from the front side of the plate, freeing the falling out elements and the structure of the senses important elements from an unnecessary layer of silicon dioxide.

An example of a specific implementation. A photoresist with a thickness of 2 μm is applied to the front side of the wafer, photolithography is performed along the protective layer to create a pattern of future etching, an operation of deep high-precision plasma-chemical etching of silicon from the front of the wafer to a depth of 100 μm with a vertical etching profile is removed, the remaining photoresist is removed from the front of the wafer, a layer of silicon dioxide with a thickness of 1 μm on the front side to protect the surface of the plate and the profile of the etched grooves on the front side, apply an aluminum film on the back side of the plate and photolithography is performed on this protective layer, to create an etching pattern on the back of the plate, an operation of deep high-precision plasma-chemical etching of silicon from the back of the plate to a depth of 200 μm is performed, the remains of the aluminum mask from the back of the plate are removed, the dioxide layer is removed silicon from the front of the plate, freeing the falling out elements and the structure of the sensitive elements from the unnecessary layer of silicon dioxide.

This method is used for the manufacture of MEMS sensitive elements. Using the proposed method, it is possible to arrange the production of MEMS sensitive elements from single-crystal plates without using the technology of splicing plates, which can significantly simplify and cheapen the manufacturing process of MEMS elements. Using this method, it is possible to produce sensitive elements of microelectromechanical gyroscopes, micromirrors and accelerometers.

Information sources

1. Hsiao Wei-Min, US Patent 7808060 MEMS MICROPHONE MODULE AND METHOD THEREOF.

2. Brosnihhan Timothy J., US Pat. No. 7,083,997 Bonded wafer optical MEMS process.

3. Norihiro Asada, U.S. Patent 6404313 Electromagnetic actuator.

Claims (1)

A method of manufacturing sensitive elements of microelectromechanical systems (MEMS), including the application of protective coatings on the front and back sides of the plate, photolithography on the protective layers on the front and back sides, deep high-precision etching of silicon from the front and back sides of the plate to a predetermined depth and with a given profile, removal residues of masking coatings on the front and back sides of the wafer, characterized in that on the silicon wafer after etching the grooves on the front side and removing residues beyond The protective coating is applied to apply a layer of silicon dioxide to protect the front side of the plate and the profile of the etched grooves from raster during subsequent etching from the back of the plate and mechanical fixation of the falling fragments of the structure.

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