Patents by Inventor Tiemin Zhao
Tiemin Zhao has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 7456887Abstract: An improved active pixel sensor soft reset circuit for reducing image lag while maintaining low reset kTC noise. The circuit pulls down the sensor potential to a sufficiently low level before the soft reset function is completed. The level to which the sensor potential is pulled is set between 0 and the critical potential at which the reset transistor will be on when the soft reset function begins. The timing of the pull down function is such that the sensor is stabilized at the low potential before the soft reset function completes. In one embodiment, the sensor potential is pulled down using a pull-down circuit, which may consist of a CMOS type inverter. In another embodiment, the sensor potential is pulled down by the bit line. Two ways in which the bit line may be pulled down are natural discharge, or by increasing the bias on the loading transistor. Two ways in which the bias on the loading transistor may be increased are a biasing circuit, or by using a pull-down transistor.Type: GrantFiled: October 21, 2003Date of Patent: November 25, 2008Assignee: OmniVision Technologies, Inc.Inventors: Tiemin Zhao, Xinping He, Qingwei Shan, Datong Chen
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Patent number: 7368772Abstract: The active pixel includes a photodiode, a transfer gate, and a reset transistor. The photodiode is substantially covered with an overlying structure, thus protecting the entire surface of the photodiode from damage. This substantially eliminates potential leakage current sources, which result in dark current. In one embodiment, the photodiode is covered by a FOX region in combination with the transfer gate.Type: GrantFiled: August 7, 2003Date of Patent: May 6, 2008Assignee: Omnivision Technologies, Inc.Inventors: Xinping He, Chih-huei Wu, Tiemin Zhao
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Patent number: 6909162Abstract: A method for reducing dark current in a photodiode is disclosed. The photodiode comprises a N-well formed in a P-substrate. The method comprises doping the surface of said N-well with a nitrogen dopant. Alternatively, an oxygen or silicon dopant may be used. Still alternatively, a silicon oxynitride layer may be formed over the N-well.Type: GrantFiled: November 2, 2001Date of Patent: June 21, 2005Assignee: OmniVision Technologies, Inc.Inventors: Chih-huei Wu, Tiemin Zhao, Xinping He
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Publication number: 20040080646Abstract: An improved active pixel sensor soft reset circuit for reducing image lag while maintaining low reset kTC noise. The circuit pulls down the sensor potential to a sufficiently low level before the soft reset function is completed. The level to which the sensor potential is pulled is set between 0 and the critical potential at which the reset transistor will be on when the soft reset function begins. The timing of the pull down function is such that the sensor is stabilized at the low potential before the soft reset function completes. In one embodiment, the sensor potential is pulled down using a pull-down circuit, which may consist of a CMOS type inverter. In another embodiment, the sensor potential is pulled down by the bit line. Two ways in which the bit line may be pulled down are natural discharge, or by increasing the bias on the loading transistor. Two ways in which the bias on the loading transistor may be increased are a biasing circuit, or by using a pull-down transistor.Type: ApplicationFiled: October 21, 2003Publication date: April 29, 2004Inventors: Tiemin Zhao, Xinping He, Qingwei Shan, Datong Chen
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Patent number: 6727946Abstract: An improved active pixel sensor soft reset circuit for reducing image lag while maintaining low reset kTC noise. The circuit pulls down the sensor potential to a sufficiently low level before the soft reset function is completed. The level to which the sensor potential is pulled is set between 0 and the critical potential at which the reset transistor will be on when the soft reset function begins. The timing of the pull down function is such that the sensor is stabilized at the low potential before the soft reset function completes. In one embodiment, the sensor potential is pulled down using a pull-down circuit, which may consist of a CMOS type inverter. In another embodiment, the sensor potential is pulled down by the bit line. Two ways in which the bit line may be pulled down are natural discharge, or by increasing the bias on the loading transistor. Two ways in which the bias on the loading transistor may be increased are a biasing circuit, or by using a pull-down transistor.Type: GrantFiled: December 14, 1999Date of Patent: April 27, 2004Assignee: OmniVision Technologies, Inc.Inventors: Tiemin Zhao, Xinping He, Qingwei Shan, Datong Chen
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Publication number: 20040026724Abstract: The active pixel includes a photodiode, a transfer gate, and a reset transistor. The photodiode is substantially covered with an overlying structure, thus protecting the entire surface of the photodiode from damage. This substantially eliminates potential leakage current sources, which result in dark current. In one embodiment, the photodiode is covered by a FOX region in combination with the transfer gate.Type: ApplicationFiled: August 7, 2003Publication date: February 12, 2004Inventors: Xinping He, Chih-Huei Wu, Tiemin Zhao
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Patent number: 6649950Abstract: The active pixel includes a photodiode, a transfer gate, and a reset transistor. The photodiode is substantially covered with an overlying structure, thus protecting the entire surface of the photodiode from damage. This substantially eliminates potential leakage current sources, which result in dark current. In one embodiment, the photodiode is covered by a FOX region in combination with the transfer gate.Type: GrantFiled: August 14, 2002Date of Patent: November 18, 2003Assignee: OmniVision Technologies, Inc.Inventors: Xinping He, Chih-huei Wu, Tiemin Zhao
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Publication number: 20030086011Abstract: A method for reducing dark current in a photodiode is disclosed. The photodiode comprises a N-well formed in a P-substrate. The method comprises doping the surface of said N-well with a nitrogen dopant. Alternatively, an oxygen or silicon dopant may be used. Still alternatively, a silicon oxynitride layer may be formed over the N-well.Type: ApplicationFiled: November 2, 2001Publication date: May 8, 2003Inventors: Chih-huei Wu, Tiemin Zhao, Xinping He
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Publication number: 20030085400Abstract: The active pixel includes a photodiode, a transfer gate, and a reset transistor. The photodiode is substantially covered with an overlying structure, thus protecting the entire surface of the photodiode from damage. This substantially eliminates potential leakage current sources, which result in dark current. In one embodiment, the photodiode is covered by a FOX region in combination with the transfer gate.Type: ApplicationFiled: August 14, 2002Publication date: May 8, 2003Applicant: OMNIVISION TECHNOLOGIES, INC.Inventors: Xinping He, Chih-Huei Wu, Tiemin Zhao
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Patent number: 6486521Abstract: A photodiode with an optimized floating P+ region for a CMOS image sensor. The photodiode is constructed with a P+/Nwell/Psub structure. The Nwell/Psub junction of the photodiode acts as a deep junction photodiode which offers high sensitivity. The P+ floating region passivates the silicon surface to reduce dark currents. Unlike a traditional pinned photodiode structure, the P+ region in the present invention is not connected to the Pwell or Psub regions, thus making the P+ region floating. This avoids the addition of extra capacitance to the cell. The photodiode may be included as part of an active pixel sensor cell, the layout of which is fully compatible with the standard CMOS fabrication process. This type of active pixel sensor cell includes the photodiode, and may be configured with a three transistor configuration for reading out the photodiode signals.Type: GrantFiled: October 2, 2001Date of Patent: November 26, 2002Assignee: OmniVision Technologies, Inc.Inventors: Tiemin Zhao, Xinping He, Datong Chen
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Patent number: 6462365Abstract: The active pixel includes a photodiode, a transfer gate, and a reset transistor. The photodiode is substantially covered with an overlying structure, thus protecting the entire surface of the photodiode from damage. This substantially eliminates potential leakage current sources, which result in dark current. In one embodiment, the photodiode is covered by a FOX region in combination with the transfer gate.Type: GrantFiled: November 6, 2001Date of Patent: October 8, 2002Assignee: OmniVision Technologies, Inc.Inventors: Xinping He, Chih-huei Wu, Tiemin Zhao
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Patent number: 6355965Abstract: An improved pixel structure for a logarithm response image sensor. The pixel structure and read-out sequence provides a method to get a signal free from offsets and gain mismatch due to nonuniformities in the device parameters. An additional transistor is added to a basic logarithmic response pixel structure in order to provide a means for producing a calibration signal level. The calibration transistor is either coupled within the pixel structure itself, or to an extra column line that is coupled to a voltage source. The calibration transistor is therefore not coupled to an extra column line with a calibration current source, and therefore does not have the additional circuitry, power consumption, or control issues associated with a calibration current source type method.Type: GrantFiled: March 29, 2000Date of Patent: March 12, 2002Assignee: Omnivision Technologies, Inc.Inventors: Xingping He, Tiemin Zhao
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Publication number: 20020017695Abstract: A photodiode with an optimized floating P+ region for a CMOS image sensor. The photodiode is constructed with a P+/Nwell/Psub structure. The Nwell/Psub junction of the photodiode acts as a deep junction photodiode which offers high sensitivity. The P+ floating region passivates the silicon surface to reduce dark currents. Unlike a traditional pinned photodiode structure, the P+ region in the present invention is not connected to the Pwell or Psub regions, thus making the P+ region floating. This avoids the addition of extra capacitance to the cell. The photodiode may be included as part of an active pixel sensor cell, the layout of which is fully compatible with the standard CMOS fabrication process. This type of active pixel sensor cell includes the photodiode, and may be configured with a three transistor configuration for reading out the photodiode signals.Type: ApplicationFiled: October 2, 2001Publication date: February 14, 2002Inventors: Tiemin Zhao, Xinping He, Datong Chen
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Patent number: 6339248Abstract: A photodiode with an optimized floating P+ region for a CMOS image sensor. The photodiode is constructed with a P+/Nwell/Psub structure. The Nwell/Psub junction of the photodiode acts as a deep junction photodiode which offers high sensitivity. The P+ floating region passivates the silicon surface to reduce dark currents. Unlike a traditional pinned photodiode structure, the P+ region in the present invention is not connected to the Pwell or Psub regions, thus making the P+ region floating. This avoids the addition of extra capacitance to the cell. The photodiode may be included as part of an active pixel sensor cell, the layout of which is fully compatible with the standard CMOS fabrication process. This type of active pixel sensor cell includes the photodiode, and may be configured with a three transistor configuration for reading out the photodiode signals.Type: GrantFiled: November 15, 1999Date of Patent: January 15, 2002Assignee: Omnivision Technologies, Inc.Inventors: Tiemin Zhao, Xinping He, Datong Chen
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Patent number: 5880620Abstract: A pass gate circuit includes a pass transistor and a body bias control circuit for biasing the body of the pass transistor to reduce body effect. The body bias control circuit includes one or more control transistors arranged to selectively connect the substrate (body) of the pass transistor to the drain or gate of the pass transistor when predetermined voltages are applied to the drain and gate of the pass transistor. As a result, the pass transistor exhibits a reduced body effect in the on-state. In one embodiment, the body bias control circuit includes a first control transistor having a drain and gate connected to the gate of the pass transistor, a gate connected to the drain of the pass transistor, and a source. The body bias control circuit also includes a second control transistor having a drain connected to the source of the first control transistor, a source connected to a body of the pass transistor, and a gate connected to the drain of the pass transistor.Type: GrantFiled: April 22, 1997Date of Patent: March 9, 1999Assignee: Xilinx, Inc.Inventors: Daniel Gitlin, Sheau-Suey Li, Martin L. Voogel, Tiemin Zhao