We describe two fabricated microthermal shear stress sensors by antiadhesion surface technology and anodic bulk-bonding technology. Two sensors are based on thermal transfer principles with adiabatic structures. The thermal sensor element is a titanium—platinum alloy resistor sputtered on the top of a low pressure chemical vapor deposited (LPCVD) silicon nitride diaphragm with an adiabatic vacuum cavity underneath. The surface micromachined thermal shear stress sensor uses microbumps on the silicon substrate in the sacrificial layer technology to prevent the silicon nitride diaphragm's stiction to the substrate. Microbumps formed by isotropic silicon etching in HNA (the system HF, HNO3, and HC2H3O2) are arrayed in several points on the silicon substrate with distances of 147 µm in the (200×250)-µm2×1.5-µm vacuum cavity. This cavity is formed by LPCVD silicon nitride film sealing with 30-Pa vacuum degree. The anodic bulk-bonding micromachined thermal shear stress sensor uses bulk silicon substrate etching and anodic bonding to form the (200×250)-µm2×400-µm high aspect ratio cavity with 5×10−2 Pa vacuum degree. The titanium platinum alloy resistor, (5×150)-µm2×0.2 µm, sputtered on the top of the 1.5-µm-thick LPCVD silicon nitride diaphragm with this bonding chamber, has a temperature coefficient of resistance (TCR) value of 0.33%/°C. According to the comparison of the adiabatic characteristics among three cases—a titanium platinum alloy resistor located over the high aspect ratio 5×10−2 Pa vacuum cavity, over the 30-Pa vacuum cavity, and directly on top of the substrate—the first case has the best adiabatic characteristic: the titanium platinum alloy resistor located over the 5×10−2-Pa vacuum cavity has the maximum thermal resistance of 5362 °C/W. Besides the sensor sensitivity performances, it has a comparatively short time constant with value of 0.1 ms under the constant current (CC) mode driving circuit.
In this paper, Beam Propagation Method (BPM) with Fast Fourier Transforms(FFT) is employed to efficiently calculate the diffract image in the wafer plane for both conventional and second generation synchrotron-based proximity x-ray lithography(PXL). In the simulation, a dark-field isolated space pattern silicon nitride/Ta x-ray mask is used for conventional PXL and a diamond /Ta x-ray mask is used for second generation PXL, the diffract image’s dependency on absorber thickness, mask-wafer gap, effective total blur, linewidth and absorber sidewall slope has been numerically evaluated. For conventional PXL, in order to obtain a isolated trench resolution of 50nm, the mask-wafer gap should be controlled below 5 micron, the optimization condition is mask-wafer gap 5 micron, Ta absorber thickness 300nm, effective total blur 10nm, absorber sidewall slope 3°, the corresponding aerial image contrast is 0.457; For second generation, in order to obtain a isolated trench resolution of 50nm, the mask-wafer gap can be as large as 10 micron. In order to obtain a isolated trench resolution of 35nm, mask-wafer gap should be controlled below 5 micron.
T-shaped gate formation is a important process step in the fabrication of high frequency monolithic microwave integrated circuits (MMIC), many different lithography process have been used for this purpose, such as bi-layer or tri-layer using e-beam lithography, hybrid UV-e-beam lithography. Proximity x-ray lithography (PXL) has shown many advantages in the MMIC manufacturing, such as high resolution, large process windows, low cost and high throughout, and so on. In this article, a new ZEP520/P(MMA-MAA)/ZEP520 tri-layer process using synchrotron-based PXL is proposed for the T-shaped gate formation, without any additional intermediate layer, the resists intermixing problem has been solved successfully, a dark-field isolated trench x-ray mask was used for this purpose. A three stage development process using xylene for the head, MIBK:IPA=1:3 for the middle and xylene for the foot was also used. Initial work has shown this process to be robust.
This paper reports a novel freestanding stencil bi-material cantilever structure without sacrificial layer process in detail; the complexity and costs of fabrication process are reduced greatly. This type of microcantilever is made of two material layers (SiNx/Au), which is a 2dimension device, not a 3dimension one. The cantilevers and the support points are at the same plane in the stencil structure. MEMS sacrificial layer process problems are avoided completely in the process of the freestanding stencil bi-material cantilever microstructure so as to simplify process steps. Since two materials selected in the bi-material cantilever have a large mismatch in thermal conductivity and expansion coefficient, and all cantilevers in the device are freestanding completely, this kind of device is sensitive to a lot of physical varieties, such as thermal, infrared, mechanical vibration and electronic signals. This paper illuminates the total fabrication process of freestanding stencil bi-material cantilever structure; and in particular presents an application of uncooled infrared imaging system based on the novel freestanding bi-material cantilever structure in the final part of this paper.
The temperature distribution on the surface of the mask, during post exposure bake (PEB) of the X-ray mask after electron beam writing (EBW), is very important for controlling the mask critical dimension(CD). In this paper, three-dimensional finite element (FE) thermal model of the X-ray mask has been set up. The results of the numerical simulation indicate that it will take 2.16 seconds for PEB to get thermal steady when the boundary conditions of the top surface of the resist are natural convections, and that the temperature distribution of the mask is non-uniform, and the maximum temperature difference is 10.19°C, which will most likely make the resist at the high temperature region baked excessively. By using insulation measures, the boundary conditions of the top surface of the resist are changed to adiabatic conditions, and the temperature distribution of the mask is very uniform, which will reduce the influence on the absorber CD from PEB.
In this paper a brief description is given to introduce the activities of the manufacturing technology using the synchrotron radiation light source in the National Synchrotron Radiation Laboratory (NSRL). The light source in NSRL is a dedicated synchrotron radiation facility in China. Five beamlines and corresponding experimental stations, including soft x-ray lithography, have been constructed. The main experimental results obtained from the soft x-ray lithography station are reported. We have fabricated some devices using the synchrotron radiation lithography, for example, the high electron mobility transistor, high Tc superconductor infrared detector-array, diffraction grating, and micro condenser zone plate. A simple method for the achievement of synchrotron radiation x-ray lithography mask will also be presented. The LIGA (German abbreviation for: Lithograpie, Galvanoforming, and Abforming) technique has been developed in NSRL. It is the most promising technique for the fabrication of three-dimensional microstructures. We are successful in making several microdevices by deep x-ray lithography and microelectroforming, such as microgearwheel, micro acceleration sensor.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.