Sensor with electrically controllable aperture for inspection and metrology systems

Patent metadata

Field	Value
Publication number	US-9860466-B2
Application number	US-201615153543-A
Country	US
Kind code	B2
Filing date	May 12, 2016
Priority date	May 14, 2015
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

Pixel aperture size adjustment in a linear sensor is achieved by applying more negative control voltages to central regions of the pixel's resistive control gate, and applying more positive control voltages to the gate's end portions. These control voltages cause the resistive control gate to generate an electric field that drives photoelectrons generated in a selected portion of the pixel's light sensitive region into a charge accumulation region for subsequent measurement, and drives photoelectrons generated in other portions of the pixel's light sensitive region away from the charge accumulation region for subsequent discard or simultaneous readout. A system utilizes optics to direct light received at different angles or locations from a sample into corresponding different portions of each pixel's light sensitive region. Multiple aperture control electrodes are selectively actuated to collect/measure light received from either narrow or wide ranges of angles or locations, thereby enabling rapid image data adjustment.

First claim

The invention claimed is:

1. A method of inspecting a sample, the method comprising:
directing and focusing radiation onto the sample;
directing radiation received from the sample to a line sensor, wherein the line sensor includes a plurality of pixels disposed on a substrate, each pixel including a resistive control gate attached to an upper surface of the substrate and disposed over an associated light sensitive region of the substrate, and wherein directing the received radiation includes causing the directed light to enter the associated light sensitive region of each of the plurality of pixels;
driving the resistive control gate of each said pixel using predetermined aperture control signals such that the resistive control gate generates an electric field in said associated light sensitive region that drives first photoelectrons generated by first light portions in a first light sensitive portion of each said pixel into a first charge accumulation region located adjacent to a first end portion of each said resistive control gate, and drives second photoelectrons generated by second light portions in a second light sensitive portion of each said pixel into a second charge accumulation region located adjacent to a second end portion of each said resistive control gate.

2. The method of claim 1 , further comprising measuring the first photoelectrons accumulated in the first charge accumulation region during a predetermined period.

3. The method of claim 2 , wherein directing the radiation further comprises generating a confocal image including first confocal image portions directed from said sample into a first light sensitive portion of said associated light sensitive region of each said pixel, and second confocal image portions directed from said sample into a second light sensitive portion of said associated light sensitive region of each said pixel.

4. The method of claim 2 , wherein directing the radiation further comprises directing first radiation portions disposed within a first range of angles from said sample into a first light sensitive portion of said associated light sensitive region of each said pixel, and directing second radiation portions disposed within a second range of angles from said sample into a second light sensitive portion of said associated light sensitive region of each said pixel.

5. The method of claim 1 , wherein driving the resistive control gate of each said pixel comprises generating first and second aperture control signals on first and second end electrodes that contact opposing end portions of each said resistive control gate and generating a third aperture control signal on at least one central electrode that contacts a central portion of each said resistive control gate.

6. The method of claim 5 , wherein driving the resistive control gate further comprises:
during a first time period, generating said first, second and third control signals such that said first and second aperture control signals are more positive than said third aperture control signal, and
during a second time period, generating said first, second and third control signals such that said first control signal is more positive than said second and third control signals.

7. The method of claim 1 , wherein driving the resistive control gate of each said pixel comprises generating first and second aperture control signals on first and second end electrodes that respectively contact corresponding end portions of each said resistive control gate, and generating third, fourth and fifth aperture control signals respectively on first, second and third central electrodes that respectively contact corresponding central portions of each said resistive control gate, wherein said first, second and fourth aperture control signals are more positive than said third and fifth aperture control signals, whereby said resistive control gate of each said pixel generates an electric field in said associated light sensitive region that drives said first photoelectrons into said first charge accumulation region, and drives said second photoelectrons into said second charge accumulation region, and drives third photoelectrons generated by third light portions in a third light sensitive portion of each said pixel into a third charge accumulation region located between said first and second charge accumulation regions.

8. The method of claim 7 , wherein directing the radiation further comprises directing first radiation portions disposed within a first range of angles from said sample into said first light sensitive portion of said associated light sensitive region of each said pixel, directing second radiation portions disposed within a second range of angles from said sample into said second light sensitive portion of said associated light sensitive region of each said pixel, and directing third radiation portions disposed within a third range of angles from said sample into said third light sensitive portion of said associated light sensitive region of each said pixel.

9. The method of claim 1 ,
wherein the line sensor includes a mechanical aperture structure disposed between a lower surface of the substrate and said sample, and
wherein driving the resistive control gate comprises adjusting said electric field to correct for misalignment of said mechanical aperture structure.

10. A sensor comprising:
a substrate having an upper surface and an opposing lower surface;
a plurality of pixels disposed on the substrate, each pixel including a resistive control gate attached to the upper surface and disposed over an associated light sensitive region of the substrate, a first transfer gate disposed adjacent to a first end portion of said resistive control gate, and a second transfer gate disposed adjacent to a second end portion of said resistive control gate;
a plurality of elongated aperture control electrodes extending in parallel across said resistive control gates of said plurality of pixels, said plurality of aperture control electrodes including a first end electrode contacting said first end portions of each said resistive control gate, a second end electrode contacting said second end portions of each said resistive control gate, and one or more central electrode contacting each said resistive control gate and disposed between said first and second end electrodes; and
a control circuit configured to simultaneously apply aperture control signals onto said resistive control gates of said plurality of pixels by way of said plurality of aperture control electrodes such that first and second aperture control signals applied to said first and second end electrodes are more positive than a third aperture control signal applied to said at least one central electrode, thereby causing each said resistive control gate to generate an electric field in said associated light sensitive region such that first photoelectrons generated by said first light portions in a first light sensitive portion of each said pixel are driven by said electric field into a first charge accumulation region located adjacent to said first end portion of each said resistive control gate, and such that second photoelectrons generated by second light portions in said second light sensitive portion of each said pixel are driven by said electric field into a second charge accumulation region located adjacent to said second end portion of each said resistive control gate.

11. The sensor of claim 10 , further comprising a readout circuit including a plurality of readout registers, each said readout register being operably coupled to said first transfer gate of an associated pixel of said plurality of pixels,
wherein said control circuit is further configured to

Assignees

• Kla Tencor Corp

Inventors

• Chuang Yung-Ho Alex
• Fielden John
• Brown David L
• Zhang Jingjing
• Lyon Keith
• Wang Mark Shi

Classifications

• H04N25/715 Primary

  using frame interline transfer [FIT] · CPC title

• G01N21/956

  Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} · CPC title

• G01N2201/12

  Circuits of general importance; Signal processing · CPC title

• G01B11/306

  for measuring evenness · CPC title

• G01N2021/1725

  Modulation of properties by light, e.g. photoreflectance · CPC title