System for directly measuring the depth of a high aspect ratio etched feature on a wafer
First Claim
1. A system for directly measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said system comprising:
- a) a reflectometer that is positioned to face the non-etched surface of the wafer, wherein said reflectometer having means for producing a focused incident light that is applied to the non-etched surface of the wafer, and means for receiving and processing a reflected light that is also applied from the non-etched surface of the wafer, wherein the output of said reflectometer is an analog spectrum optical frequency signal,b) an analog-to-digital (ADC) converter that converts the analog spectrum optical frequency signal to a corresponding digital data signal,c) a computer, that in combination with software, has means for processing the digital data signal applied from said ADC and to display the depth of the high aspect ratio etched surface of the wafer.
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Accused Products
Abstract
A system (10) for directly measuring the depth of a high aspect ratio etched feature on a wafer (80) that includes an etched surface (82) and a non-etched surface (84). The system (10) utilizes an infrared reflectometer (12) that in a preferred embodiment includes a swept laser (14), a fiber circulator (16), a photodetector (22) and a combination collimator (18) and an objective lens (20). From the objective lens (20) a focused incident light (23) is produced that is applied to the non-etched surface (84) of the wafer (80). From the wafer (80) is produced a reflected light (25) that is processed through the reflectometer (12) and applied to an ADC (24) where a corresponding digital data signal (29) is produced. The digital data signal (29) is applied to a computer (30) that, in combination with software (32), measures the depth of the etched feature that is then viewed on a display (34).
31 Citations
20 Claims
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1. A system for directly measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said system comprising:
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a) a reflectometer that is positioned to face the non-etched surface of the wafer, wherein said reflectometer having means for producing a focused incident light that is applied to the non-etched surface of the wafer, and means for receiving and processing a reflected light that is also applied from the non-etched surface of the wafer, wherein the output of said reflectometer is an analog spectrum optical frequency signal, b) an analog-to-digital (ADC) converter that converts the analog spectrum optical frequency signal to a corresponding digital data signal, c) a computer, that in combination with software, has means for processing the digital data signal applied from said ADC and to display the depth of the high aspect ratio etched surface of the wafer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for directly measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said system comprising;
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a) an infrared reflectrometer comprising; (1) a swept laser having means for producing a wavelength that is swept in time across a range of wavelengths, a trigger signal and a clock signal, (2) a fiber circulator having a first input that is applied the wavelengths from said swept laser, a second input, a first light output and a second light output, (3) a collimator that is applied the second light output from said fiber circulator and that produces a collimated light output that is applied to the second input on said fiber circulator, (4) an objective lens that interfaces with the collimator and that is positioned to face the non-etched surface of the wafer, wherein from the lens is emitted a focused incident light that is applied to the non-etched surface of the wafer, wherefrom the wafer is emitted a reflected light that is applied to said objective lens, (5) a photodetector that is applied the first light output from said fiber circulator and that produces an analog spectrum optical frequency signal, b) an analog to digital converter (ADC) that functions as a data acquisition device, said ADC having a first input and a second input that are applied respectively the trigger signal and the clock signal from the swept laser, wherein said ADC further having a third input that is applied the analog spectrum optical frequency signal that is applied from the photodetector, wherein said ADC produces a corresponding digital data signal, c) a computer, in combination with software, having means for processing the digital data signal applied from the ADC and to produce a display signal that portrays on a display the depth of the high aspect ratio etched feature on the wafer, and d) a wafer holding fixture having means for being laterally displaced and means for positioning the non-etched surface of the wafer facing the objective lens on said infrared reflectometer. - View Dependent Claims (11, 12, 13, 14)
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15. A system for directly measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said system comprising:
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a) a broadband incoherent infrared source (BIIS) having means for producing an incoherent light source, b) a fiber circulator having a first input that is applied the incoherent light signal from said BIIS, a second input, a first light output and a second light output, c) a collimator that is applied the second light output from said fiber circulator and that produces a collimated light output that is applied to the second input on said fiber circulator, d) an objective lens that interfaces with the collimator and that is positioned to face the non-etched surface of the wafer, wherein from the lens is emitted a focused incident light that is applied to the non-etched surface of the wafer, wherefrom the wafer is emitted a reflected light that is applied to said objective lens, e) a spectrometer that is applied the light signal from said fiber circulator and that produces a light distribution signal, f) a computer, in combination with software, having means for processing the light distribution signal applied from said spectrometer and to produce a digital data signal that portrays on a display the depth of the high aspect ratio etched feature on the wafer, and g) a wafer holding fixture having means for being laterally displaced and means for positioning the non-etched surface of the wafer facing the objective lens. - View Dependent Claims (16)
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17. A first method for measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said first method comprising the following steps:
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a) position a reflectometer facing the non-etched surface of the wafer, b) measure the thickness of the wafer at a location where it is not etched, c) measure the thickness of the wafer at a location where it is etched, and d) subtract the two measurements to determine the depth of the etched feature. - View Dependent Claims (18)
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19. A second method for measuring the depth of a high aspect ratio etched feature on a wafer having an etched surface and a non-etched surface, said second method comprising the following steps:
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a) position a reflectometer facing the non-etched surface of the Wafer, b) simultaneously illuminate both the etched feature and the etched surface adjacent to the etched feature, c) measure the interference between the reflections from the etched surface and the etched feature, and d) calculate the depth of the etched feature. - View Dependent Claims (20)
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Specification