Image sensors with sinusoidal reset, noise cancellation, and nonpulsed charge transfer for inspection and metrology

A system configured for determining information for a sample, comprising:

• an illumination subsystem configured for directing light generated by an illumination source to the sample;
• and
• an image sensor positioned in a path of light from the sample and comprising:
• a silicon layer configured to generate electron-hole pairs based on the light from the sample being incident on a light-sensitive area of the silicon layer;
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise at least one channel and first gate electrodes configured to control electron accumulation in the at least one channel in response to generation of the electron-hole pairs;
• and
• a plurality of sensing nodes, wherein each of the plurality of sensing nodes is electrically connected to at least one circuit of the plurality of circuits, wherein the plurality of sensing nodes are formed on the first side of the silicon layer adjacent to the plurality of circuits, wherein each of the plurality of sensing nodes comprise:
• a floating diffusion structure connected to one of the at least one channel of the plurality of circuits and an output circuit of the image sensor;
• a charge reset structure configured to remove a charge from the floating diffusion structure,
• wherein the floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the floating diffusion structure,
• wherein the output circuit is configured to generate output responsive to the voltage output by the floating diffusion structure;
• a noise-cancellation gate electrode, adjacent to the floating diffusion structure and configured to be driven by a noise-cancellation signal;
• a circuit configured to drive the noise-cancellation gate electrode with such noise-cancellation signal;
• and
• a controller configured for determining the information for the sample based on the output.

A method of inspecting a sample, the method comprising:

• directing and focusing light onto the sample;
• receiving light from the sample and directing the light to an image sensor, the image sensor comprising:
• a silicon layer configured to generate electron-hole pairs based on the light from the sample being incident on a light-sensitive area of the silicon layer;
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise at least one channel and first gate electrodes configured to control electron accumulation in the at least one channel in response to generation of the electron-hole pairs;
• and
• a plurality of sensing nodes, wherein each of the plurality of sensing nodes is electrically connected to at least one circuit of the plurality of circuits, wherein the plurality of sensing nodes are formed on the first side of the silicon layer adjacent to the plurality of circuits, wherein each of the plurality of sensing nodes comprise:
• a floating diffusion structure connected to one of the at least one channel of the plurality of circuits and an output circuit of the image sensor;
• a charge reset structure configured to remove a charge from the floating diffusion structure,
• wherein the floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the floating diffusion structure,
• wherein the output circuit is configured to generate output responsive to the voltage output by the floating diffusion structure;
• and
• a noise-cancellation gate electrode, adjacent to the floating diffusion structure and configured to be driven by a noise-cancellation signal;
• moving the sample relative to the light simultaneously with the receiving;
• driving the first gate electrodes with charge transfer clock signals that are synchronized to the moving of the sample relative to the light, the charge transfer clock signals causing the electron accumulation to be transferred from the first gate electrodes to the plurality of sensing nodes;
• driving the charge reset structure of each sensing node with a reset clock signal that causes the electron accumulation to be removed from the floating diffusion structure of each sensing node;
• driving the noise-cancellation gate electrode of each sensing node with the noise-cancellation signal;
• and
• utilizing a readout circuit including an Analog-to-Digital Converter (ADC) coupled to the output circuit electrically connected to the floating diffusion structure of each sensing node and configured to convert the voltage output by each sensing node to a digital number.

A system configured for determining information for a sample, comprising:

• an illumination subsystem configured for directing light generated by an illumination source to the sample;
• and
• an image sensor positioned in a path of light from the sample and comprising:
• a silicon layer configured to generate electron-hole pairs based on the light from the sample being incident on a light-sensitive area of the silicon layer;
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise at least one channel and first gate electrodes configured to control electron accumulation in the at least one channel in response to generation of the electron-hole pairs;
• and
• a plurality of sensing nodes, wherein each of the plurality of sensing nodes is electrically connected to at least one circuit of the plurality of circuits, wherein the plurality of sensing nodes are formed on the first side of the silicon layer adjacent to the plurality of circuits, wherein each of the plurality of sensing nodes comprise:
• a floating diffusion structure connected to one of the at least one channel of the plurality of circuits and an output circuit of the image sensor;
• a charge reset structure configured to remove a charge from the floating diffusion structure,
• wherein the floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the floating diffusion structure,
• wherein the output circuit is configured to generate output responsive to the voltage output by the floating diffusion structure;
• a noise-cancellation gate electrode, adjacent to the floating diffusion structure and configured to be driven by a noise-cancellation signal;
• at least one Analog-to-Digital Converter (ADC) configured to generate digital image data values by digitizing corresponding voltage outputs generated on the plurality of sensing nodes;
• at least one Digital Signal Processor (DSP) configured to receive and evaluate the digital image data values;
• and
• a timing generator configured to generate charge transfer clock, reset clock, and the noise-cancellation signal utilized to drive the image sensor,
• wherein the at least one DSP is configured to analyze the digital image data values to extract their frequency components and an amplitude of the frequency components,
• wherein the timing generator is configured to vary each noise-cancellation signal applied to each noise-cancellation gate electrode of each of the plurality of sensing nodes based on the frequency components and the amplitude of the frequency components received by the at least one DSP, to cancel a feedthrough caused on the voltage outputs generated on the plurality of sensing nodes.

An image sensor, comprising:

• a silicon layer configured to generate electron-hole pairs when light is incident on a light-sensitive area of the silicon layer;
• and
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise:
• a first channel and first gate electrodes configured to control electron accumulation in the first channel in response to generation of the electron-hole pairs;
• a resistive gate electrode, formed on the first side of the silicon layer adjacent to the first gate electrodes and outside of the light-sensitive area, and formed by a resistive gate structure, wherein the resistive gate structure comprises:
• a channel electrically connected to the first channel of the plurality of circuits and to a first sensing node of the image sensor;
• and
• electrical connections configured to control a voltage in the channel of the resistive gate electrode to direct the electron accumulation from the channel of the resistive gate electrode near the first gate electrodes to the channel near the first sensing node;
• and
• the first sensing node, formed on the first side of the silicon layer adjacent to the resistive gate electrode, wherein the first sensing node comprises:
• a first floating diffusion structure connected to the first channel of the plurality of circuits and a first output circuit of the image sensor;
• and
• a first charge reset structure configured to remove a charge from the first floating diffusion structure,
• wherein the first floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the first floating diffusion structure,
• wherein the first output circuit is configured to generate output responsive to the voltage output by the first floating diffusion structure.

A system configured for determining information for a sample, comprising:

• an illumination subsystem configured for directing light generated by an illumination source to the sample;
• an image sensor positioned in a path of light from the sample and comprising:
• a silicon layer configured to generate electron-hole pairs when the light from the sample is incident on a light-sensitive area of the silicon layer;
• and
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise:
• a first channel and first gate electrodes configured to control electron accumulation in the first channel in response to generation of the electron-hole pairs;
• a resistive gate electrode, formed on the first side of the silicon layer adjacent to the first gate electrodes and outside of the light-sensitive area, and formed by a resistive gate structure, wherein the resistive gate structure comprises:
• a channel electrically connected to the first channel of the plurality of circuits and to a first sensing node of the image sensor;
• and
• electrical connections configured to control a voltage in the channel of the resistive gate electrode to direct the electron accumulation from the channel of the resistive gate electrode near the first gate electrodes to the channel near the first sensing node;
• and
• the first sensing node, formed on the first side of the silicon layer adjacent to the resistive gate electrode, wherein the first sensing node comprises:
• a first floating diffusion structure connected to the first channel of the plurality of circuits and a first output circuit of the image sensor;
• and
• a first charge reset structure configured to remove a charge from the first floating diffusion structure,
• wherein the first floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the first floating diffusion structure,
• wherein the first output circuit is configured to generate output responsive to the voltage output by the first floating diffusion structure;
• and
• a controller configured for determining the information for the sample based on the output.

A method of inspecting a sample, the method comprising:

• directing and focusing light onto the sample;
• receiving light from the sample and directing received light to an image sensor, the image sensor comprising:
• a silicon layer configured to generate electron-hole pairs when the light from the sample is incident on a light-sensitive area of the silicon layer;
• and
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise:
• a first channel and first gate electrodes configured to control electron accumulation in the first channel in response to generation of the electron-hole pairs;
• a resistive gate electrode, formed on the first side of the silicon layer adjacent to the first gate electrodes and outside of the light-sensitive area, and formed by a resistive gate structure, wherein the resistive gate structure comprises:
• a channel electrically connected to the first channel of the first gate electrodes and to a first sensing node of the image sensor;
• and
• electrical connections configured to control a voltage in the channel of the resistive gate electrode to direct the electron accumulation from the channel of the resistive gate electrode near the first gate electrodes to the channel near the first sensing node;
• and
• the first sensing node, formed on the first side of the silicon layer adjacent to the resistive gate electrode, wherein the first sensing node comprises:
• a first floating diffusion structure connected to the first channel of the plurality of circuits and a first output circuit of the image sensor;
• and
• a first charge reset structure configured to remove a charge from the first floating diffusion structure,
• wherein the first floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the first floating diffusion structure,
• wherein the first output circuit is configured to generate output responsive to the voltage output by the first floating diffusion structure;
• moving the sample relative to the light simultaneously with the receiving;
• driving the first gate electrodes with charge transfer clock signals that are synchronized to the moving of the sample relative to the light, the charge transfer clock signals causing the electron accumulation to be transferred from one of the first gate electrodes to an adjacent first gate electrode and to the resistive gate electrode electrically connected to the first gate electrodes;
• driving the resistive gate electrode with constant voltages, wherein the resistive gate electrode is provided with a more positive voltage near the first sensing node compared to near the first gate electrodes, the constant voltages causing the electron accumulation to be transferred from the channel of the resistive gate electrode near the first gate electrodes to the channel near the first sensing node, and to the first sensing node adjacent to the resistive gate electrode;
• and
• utilizing a first readout circuit including an analog-to-digital converter (ADC) coupled to the first output circuit electrically connected to the first sensing node and configured to convert the voltage output by the first sensing node to a digital number.

A system configured for determining information for a sample, comprising:

• an illumination subsystem configured for directing light generated by an illumination source to the sample;
• and
• an image sensor positioned in a path of light from the sample and comprising:
• a silicon layer configured to generate electron-hole pairs based on the light from the sample being incident on a light-sensitive area of the silicon layer;
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise at least one channel and first gate electrodes configured to control electron accumulation in the at least one channel in response to generation of the electron-hole pairs;
• and
• a plurality of sensing nodes, wherein each of the plurality of sensing nodes is electrically connected to at least one circuit of the plurality of circuits, formed on the first side of the silicon layer adjacent to the plurality of circuits, wherein each of the plurality of sensing nodes comprise:
• a floating diffusion structure connected to one of the at least one channel of the plurality of circuits and an output circuit of the image sensor;
• a charge reset structure configured to remove a charge from the floating diffusion structure,
• wherein the floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the floating diffusion structure,
• wherein the output circuit is configured to generate output responsive to the voltage output by the floating diffusion structure;
• a timing generator configured to drive the charge reset structure with a sinusoidal reset clock signal;
• and
• a controller configured for determining the information for the sample based on the output.

A method of inspecting a sample, the method comprising:

• directing and focusing light onto the sample;
• receiving light from the sample and directing the light to an image sensor, the image sensor comprising:
• a silicon layer configured to generate electron-hole pairs based on the light from the sample being incident on a light-sensitive area of the silicon layer;
• a plurality of circuits formed on a first side of the silicon layer, wherein the plurality of circuits comprise at least one channel and first gate electrodes configured to control electron accumulation in the at least one channel in response to generation of the electron-hole pairs;
• and
• a plurality of sensing nodes, wherein each of the plurality of sensing nodes is electrically connected to at least one circuit of the plurality of circuits, formed on the first side of the silicon layer adjacent to the plurality of circuits, wherein each of the plurality of sensing nodes comprise:
• a floating diffusion structure connected to one of the at least one channel of the plurality of circuits and an output circuit of the image sensor;
• and
• a charge reset structure configured to remove a charge from the floating diffusion structure,
• wherein the floating diffusion structure is configured to convert the charge responsive to the electron accumulation to a voltage proportional to an amount of the charge and dependent on a capacitance of the floating diffusion structure,
• wherein the output circuit is configured to generate output responsive to the voltage output by the floating diffusion structure;
• moving the sample relative to the light simultaneously with the receiving;
• driving the first gate electrodes with charge transfer clock signals that are synchronized to the moving of the sample relative to the light, the charge transfer clock signals causing the electron accumulation to be transferred from the first gate electrodes to the plurality of sensing nodes;
• driving the charge reset structure of each sensing node with a reset clock signal that causes the electron accumulation to be removed from the floating diffusion structure of each sensing node,
• wherein the reset clock signal comprises a sinusoidal reset clock signal;
• and
• utilizing a readout circuit including an Analog-to-Digital Converter (ADC) coupled to the output circuit electrically connected to the floating diffusion structure of each sensing node and configured to convert the voltage output by each sensing node to a digital number.