This technology was first separated from the silicon-based circuit production technology, and the application of this technology has played a crucial role in the development of manufacturing in certain industries.
The following is a comprehensive and detailed discussion of micromachining processes and applications.
I. Micro-mechanical manufacturing process and application
1. Micro-mechanical etching technology
Micro-mechanical production technology in the use of integrated circuits in the production process, the corresponding processing process is actually only required for the depth of 10 microns or so on the surface of the wafer to be taken into account, but for the micro-mechanical structural components for the processing of the process, it is necessary to completely through the entire wafer thickness for three-dimensional processing. The three-dimensional processing is carried out through the entire thickness of the wafer.
At the same time, depending on the etchant used, the etching method used is also divided into wet etching, dry etching.
In the process of dry etching, mainly isotropic etching, in case of need, can also be anisotropic etching; and wet etching, in fact, is in the etchant for the liquid case called wet etching.
In the implementation of the anisotropic etching process, due to the complexity of the atomic structure of monocrystalline silicon, resulting in the crystalline surface of the corrosion rate has a greater variability, and in the crystalline surface of the silicon substrate to take the anisotropic corrosion measures, will be directly along the surface of the crystal to stop the etching, and the face and the face of the inter-face will be formed at an angle of 54.75°.
After utilizing the relationship between this type of etching rate and the crystalline surfaces, the silicon substrate can be processed to produce a variety of different structures.
2. Silicon Surface Micromachining
Silicon surface micromachining is a processing technology in which micromechanical devices are fabricated entirely on the surface of the wafer without penetrating the wafer surface.
Generally speaking, the micro-mechanical structure is commonly used thin film material layer to produce, commonly used thin film layer materials are: polycrystalline silicon, silicon nitride, silicon oxide, phosphosilicate glass (PSG), borosilicate glass (BPSG) and metal.
In order to fabricate complex microstructures, such thin film layers are deposited on silicon wafers using PVD or CVD methods, and the structures are fabricated using photolithography processes and chemical or physical etching processes.
Here, the sacrificial layer plays a very important role.
The role of the sacrificial layer is to separate the structural layer from the substrate during the successive processing to form the structural layer.
The thickness of the sacrificial layer is generally 1-2 μm, but it can be thicker.
After deposition, the sacrificial layer is etched into the desired shape.
Using the surface micromachining process, it is possible to fabricate suspended structures such as miniature cantilever beams, cantilevers, miniature bridges and miniature cavities.
3. LIGA process
LIGA process itself is a kind of micro-mechanical technology through the X-ray ray three-dimensional microstructure processing, in this technology, in fact, contains the X-ray depth of synchrotron radiation photo-etching, electroforming, plastic injection molding of the three main process steps.
The LIGA technology itself is actually for the planar IC process involved in lithography to draw on, but compared to the LIGA technology for the material processing process shows the depth and width of far greater than the standard IC production technology in the thin film sub-micron photolithography technology parameters.
At the same time, the thickness that can be processed is also higher than the typical value of the plane process 2μm standard; In addition, the LIGA process can also be effective for non-silicon materials to perform three-dimensional microfabrication work, and which can be used in a wider range of materials.
The application of LIGA technology in the micromachining system effectively promotes the rapid promotion and development of MEMS technology itself in the production industry.
4. Quasi-LIGA technology
LIGA technology in the actual use of the process, the cost of higher demand, and the process technology is extremely complex.
In order to minimize the costly use of synchrotron light, an approximation of ultraviolet light can be used as an alternative light source.
And this is a micromechanical process similar to the LIGA technology, called LIGA technology, which is also capable of presenting deeper and wider comparisons to large three-dimensional microstructural processing.
The application of the specific processing process is as follows:
l) In the position of the silicon substrate, through the sputtering way, so that the surface can form a layer of tungstenized Chinn film with a thickness of about 230nm.
The main reason for the use of this material is that tungstenized chine exhibits excellent adhesion and can also be used as a barrier layer for isolation in the photolithography process.
After the corresponding cleaning treatment, it can also be plated again with a layer of gold with a thickness of about 200nm, which is mainly used as a pre-plating layer.
2) Next, a positive resist layer of about 30 μm is obtained by utilizing the spin coating method several times.
3)The mask is exposed in close contact with the resist layer to obtain a steep profile.
4)The light source is usually a high-pressure mercury lamp.
After exposure, the microstructure with a depth to width ratio greater than 7 can be obtained by developing in an alkaline developer, washing in water and drying in small combinations.
5)The photolithographic microstructure is plated, can get three-dimensional metal microstructure, can be used wet etching method or reactive ion etching to remove the pre-plated layer of gold and tungstenized Chin.
5. Traditional manufacturing process
l) ultra-precision machinery manufacturing process
Ultra-precision machinery manufacturing is to use the hardness of the tool is higher than the workpiece, cutting and processing of the workpiece material.
The tools used at present are turning tools, drills, milling cutters, etc., such as the use of diamond tool micro-cutting technology can be processed with a diameter of Φ25μm of the shaft, the surface roughness value is very low; the use of micro-drill can be processed with a diameter of Φ2.5μm of the holes; the use of micro-fine abrasive machining can improve the machining accuracy and the quality of the surface of the workpiece, the machining unit of up to 0.01μm, the surface roughness of Rao0.005 μm.
The use of wire discharge grinding processing can be processed with an external diameter of Φ0.1mm injection needle and a caliber of Φ0.6mm microfine nozzle.
2) special processing technology
(l) laser beam processing.
The laser generator further focuses the high energy density laser light onto the surface of the workpiece.
The light energy is absorbed and instantaneously converted into thermal energy.
Depending on the energy density, it is possible to realize punching small holes, micro-holes, precision cutting, processing of fine anti-fake marking, laser fine-tuning, dynamic balancing, typing, welding and surface heat treatment.
(2) Microfabrication with tunneling microscope.
This processing method uses scanning tunneling microscope technology for molecular-level processing, which is based on the tunneling effect in quantum mechanics.
The use of extremely fine tip (diameter of nanometers) of the metal probe as an electrode, in a vacuum with piezoelectric ceramics and other micro-displacement mechanism to control the tip of the needle and the surface of the workpiece to maintain a distance of 1 ~ 10 μm, and in the probe and the workpiece coupled with a lower voltage, then in the tip of the needle and the workpiece microscopic surface of the original insulating potential barriers between the fluctuations in the particle and the electric field due to the aberrations in the quantum mechanics, it will produce a near field! Penetration of the "tunnel" current, while the probe relative to the surface of the workpiece samples for micro-displacement scanning, you can observe the surface of a single atom or molecule of the arrangement of the state and the behavior of electrons on the surface, to obtain a single atom on the surface of the arrangement of information.
(3) Microfine EDM.
Micro-fine EDM is in the insulating working fluid through the tool electrode and the workpiece between the pulse spark discharge generated by the transient, localized high temperature to dissolve and vaporize the etching of metal, the machining process between the tool and the workpiece without macro cutting force, as long as the control of the subtle individual pulse discharge energy, with precision micro-feeding can be achieved by removing the processing of the very fine metal materials can be processed, can process the micro-fine shafts, holes, narrow slits, planes, and so on. It can process fine shafts, holes, narrow slits, flat surfaces, spatial surfaces and so on.
II. Conclusion
In summary, after decades of development, micromechanical technology has expanded from the previous single three-dimensional machining, towards the direction of system integration, from the basic exploration, began to carry out practical research.
And in the future of micro-mechanical production technology value research on the key links involved, lies in the micro-organisms three-dimensional three-dimensional respect for the work, micro-mechanical integration, micro-mechanical packaging technology.
In short, the application of micro-mechanical technology, for the development of China's high-tech industry, plays a vital role in promoting.
References
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