 All metal giant magnetoresistive memory |
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| Methods of forming magnetoresisitive devices |
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| Electronic package of photo-sensing semiconductor devices, and the fabrication and assembly thereof |
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| Electrically programmable resistance cross point memory |
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| Semiconductor photodiode |
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| Multiple color detection elevated pin photo diode active pixel sensor |
| The present invention is a color detection active pixel sensor which provides efficient absorption ... |
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| Luminance-priority electronic color image sensor |
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| Process for integration of a high dielectric constant gate insulator layer in a CMOS device |
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Microchannel system for fluid delivery
| Details |
Inventors: Wise, Kensall D.; Chen, Jingkuang;
Assignee: The Regents of the University of Michigan (Ann Arbor, MI)
Primary Examiner: Kashnikow; Andres
Assistant Examiner: Evans; Robin O.
Attorney, Agent or Firm: Rader, Fishman & Grauer PLLC
Microchannels for conducting and expelling a fluid are embedded in a surface of a silicon substrate. A channel seal is made of plural cross structures formed integrally with the silicon substrate. The cross structures are arranged sequentially over each channel, each cross structure having a chevron shape. The microchannel is sealed by oxidizing at least partially the cross structures, whereby the spaces therebetween are filled. A dielectric seal which overlies the thermally oxidized cross structures forms a complete seal and a substantially planar top surface to the silicon substrate. The dielectric seal is formed of a low pressure chemical vapor deposition (LPCVD) dielectric layer. The channel is useful in the production of an ink jet print head, and has a polysilicon heater overlying the dielectric seal. A current passing through the heater causes a corresponding increase in the temperature of the ink in the microchannel, causing same to be expelled therefreom. After expulsion of the fluid, the microchannel is refilled by capillary action. Control circuitry, including bonding pads and sensors, can be formed integrally on the silicon substrate. In drug or chemical delivery systems, sensors and/or stimulation circuitry for sensing or inducing neural and other response can be formed directly in the silicon substrate which contains the microchannel. The sensor is disposed in close proximity to the chemical distribution nozzle, facilitating neural and other studies. Microvalve arrangements can be formed with the microchannel, controlled by the on-chip circuitry. |
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DETAILED DESCRIPTION The realization of a buried flow channel in silicon in accordance with the present invention, depends upon the anisotropy of the silicon etch rate in EDP.
For example, the (100) plane has an etch rate that is about 50 times faster than that of the (111) plane.
Another consideration that is important in the practice of the present invention is that highly boron-doped single crystal silicon with a doping concentration higher than 7.
times.
10.
sup.
19 cm.
sup.
-3 is not significantly attached in EDP.
Thus, if highly boron-doped silicon is used as an etch mask, and an opening perpendicular to the <100> direction is cut through this layer to expose the (100) plane, a subsequent wet etch in EDP will undercut the mask to form a continuous flow channel.
FIG.
1 is a top plan schematic representation of a silicon wafer 10 having a plurality of cross structures 11 arranged to overlie a channel 12.
In this specific embodiment, cross structures 11 are each configured to have a chevron shape.
FIG.
2 is a cross-sectional representation of silicon wafer 10 in FIG.
1, taken along line 2--2.
As shown, a cross structure 11 overlies channel 12.
FIG.
3 is a schematic representation of a cross structure 11, further showing the direction and progress of the anisotropic etch over time.
This figure additionally shows the directional orientation of the mask with respect to structure of the silicon wafer.
FIG.
4 is a micrograph showing an actual silicon wafer etched as previously described.
This micrograph was taken at a magnification of 1500 and shows a corresponding 10 .
mu.
m distance.
FIG.
5 is a schematic cross-sectional representation of a microflow structure that is useful as a microprobe capable of delivering chemical agents to local volumes of tissue.
The present invention enables the delivery of drugs to very local areas of tissue, especially in conjunction with electrical recording and/or stimulation.
The present invention achieves the significant advantage of enabling injection of chemical agents with a spatial selectivity of less than approximately 50
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MEMS 
