Amplifier circuit with enhanced dynamic range for use in a wafer inspection method or optical inspection tool

• US 20040016867A1
• Filed: 07/29/2002
• Published: 01/29/2004
• Est. Priority Date: 07/29/2002
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Milshtein, Erel, Naftali, Ron
• Granted Patent: US 7,109,463 B2
• Time in Patent Office: Days
• US Class Current: 250/207
• CPC Class Codes: H01J 43/30 Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for

Abstract

An amplifier circuit (200) having an amplifier chain comprising an input port (215) and an output port (235) with a plurality of interconnected gain stages (220-227) therebetween, where the output of one stage provides an input to the next stage within the amplifier chain, the output port (235) being operably coupled to the plurality of interconnected gain stages (220-227) such that the amplifier circuit output is generated from any one or more of the interconnected gain stages (220-227).

Preferably, the amplifier chain is a photomultiplier tube, where light is incident on a photocathode and output current is selected from one of a number of dynode outputs or an anode output port. In using a selection from a number of dynode outputs or an anode, the accuracy of the amplification process is improved and the dynamic range of the photomultiplier tube arrangement is increased, whilst retaining shot-noise-limited optical signal detection.

Claims

1. An amplifier circuit having an amplifier chain comprising an input port and an output port with a plurality of interconnected gain stages therebetween, where the output of one stage provides an input to the next stage within the amplifier chain, the output port being operably coupled to the plurality of interconnected gain stages such that the amplifier circuit output is generated from any one or more of the interconnected gain stages.

2. The amplifier circuit according to claim 1, wherein the amplifier chain is contained within a photomultiplier tube where the input port is a photocathode for receiving incoming light, the output port is an anode for providing one of a number of selectable output currents and the interconnected gain stages are a plurality of interconnected dynodes arranged such that the photomultiplier tube output is generated from any one or more of the interconnected dynode stages or anode.

3. The amplifier circuit according to claim 1, wherein the amplifier circuit includes a switching function operably coupled to the plurality of interconnected gain stages such that the amplifier circuit output is generated by said switching function switching said output between any one or more of the interconnected gain stages.

4. The amplifier circuit according to claim 3, wherein said switching operation between any one or more of the interconnected gain stages allows sampling of one or more output signals having a larger dynamic range than when using a single gain stage output.

5. The amplifier circuit according to claim 3, wherein said switching operation performs switching between a respective dynode output current or the anode dependent upon a time period that the anode output current is in a saturated state.

6. The amplifier circuit according to claim 1, wherein said amplifier circuit output is generated from a weighted summation of a number of the interconnected gain stages.

7. The amplifier circuit according to claim 2, wherein said amplifier circuit further comprises a series of voltage dividers operably coupled to respective dynodes and used to provide a variety of dynode currents in order to increase the dynamic range magnification and/or bandwidth.

8. The amplifier circuit according to claim 1, wherein said amplifier circuit further comprises a constant current source, operably coupled to the plurality of interconnected gain stages, such that said amplifier circuit output current is obtained from a deviation of output current from the constant current source.

9. The amplifier circuit according to claim 1, wherein said amplifier circuit further comprises a current clipping mechanism, operably coupled to the plurality of interconnected gain stages and arranged to clip each of the interconnected gain stage output currents to a respective maximum output current.

10. The amplifier circuit according to claim 9, wherein said amplifier circuit further comprises a combiner operably coupled to the current clipping mechanism to sum a number of clipped currents from a number of said interconnected gain stages.

11. The amplifier circuit according to claim 2, wherein said amplifier circuit further comprises an amplifier operably configured to receive inputs from sub-groups of said plurality of said dynodes, and amplifying a dynode current output from a sub-group to provide a rough tuning operation of the amplifier circuit output current.

12. The amplifier circuit according to claim 11, wherein said amplifier includes a reduction factor to clip the current output from the respective group of dynodes.

13. The amplifier circuit according to claim 1, the amplifier circuit further comprising a memory device operably coupled to the plurality of interconnected gain stages for selecting one or more gain stages to provide the output current for the amplifier circuit.

14. A method of optically inspecting interconnects or electrical connections in a manufactured wafer or semiconductors and interconnects using a scattering light process, where the optical inspection mechanism uses the photomultiplier tube arrangement of claim 2.

15. A photomultiplier tube arrangement for use in the amplifier circuit of claim 2.

16. An optical inspection tool adapted to use the photomultiplier arrangement of claim 2.

17. A storage medium storing processor-implementable instructions and/or data for controlling a processor to select an amplifier circuit output according to claim 1.