Optical emission spectroscopy end point detection in plasma etching
First Claim
1. A method of etching a layer of material to end point, comprising the steps of:
- monitoring an intensity of emission of a species produced during an etching process;
detecting a time at which a change in such intensity of emission occurs;
calculating a time period extending in length from the time of said change to end point; and
terminating the etching process at the conclusion of said time period, whereby said layer of material is etched to end point.
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Abstract
A method for etching a batch of semiconductor wafers to end point using optical emission spectroscopy is described. The method is applicable to any form of dry plasma etching which produces an emission species capable of being monitored. In a preferred embodiment, as well as a first alternative embodiment, a computer simulation is performed using an algorithm describing the concentration of the monitored etch species within the etching chamber as a function of time. The simulation produces a time period for continuing the etching process past a detected time while monitoring the intensity of emission of the etch species. In a second alternative embodiment, this latter time period is calculated using mathematical distributions describing the parameters of the etching process. In all three embodiments, the actual time that end point of an etching process is reached is closely approximated. In this manner, all wafers in a batch of wafers being etched reach end point while at the same time, the amount of over etching is greatly minimized.
106 Citations
7 Claims
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1. A method of etching a layer of material to end point, comprising the steps of:
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monitoring an intensity of emission of a species produced during an etching process; detecting a time at which a change in such intensity of emission occurs; calculating a time period extending in length from the time of said change to end point; and terminating the etching process at the conclusion of said time period, whereby said layer of material is etched to end point.
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2. A method of etching to end point a layer of material on a plurality of semiconductor wafers, said plurality of semiconductor wafers having a substantially Gaussian thickness distribution, said method comprising the steps of:
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monitoring an intensity of emission of a species produced during an etching process; detecting a time at which a change in such intensity of emission occurs; calculating a time period extending in length from a time of theoretical end point on a first one of said plurality of semiconductor wafers to a time of theoretical end point on a second one of said plurality of semiconductor wafers, said first one having a layer thickness essentially equal to the minimum layer thickness in said substantially Gaussian thickness distribution and said second one having a layer thickness essentially equal to the maximum layer thickness in said substantially Gaussian thickness distribution; continuing the etching process past the time at which such change occurs for a length of time corresponding to said time period; and terminating the etching process at the conclusion of said time period, whereby said layer of material is etched to end point on substantially all of said plurality of semiconductor wafers. - View Dependent Claims (4)
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3. A method of etching to end point a layer of material on a plurality of semiconductor wafers in a chamber of the type having a pump for regulating pressure within the chamber, said plurality of semiconductor wafers having a substantially Gaussian thickness distribution, said method comprising the steps of:
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monitoring an intensity of emission of a species produced during an etching process; detecting a time at which an inflection point in such intensity of emission occurs; calculating a time period extending in length from a time of theoretical inflection point to a time at which theoretical end point occurs on one of said plurality of semiconductor wafers, said one having a layer thickness essentially equal to the maximum thickness in said substantially Gaussian thickness distribution; continuing the etching process past the time at which said inflection point is detected for a length of time corresponding to said time period; and terminating the etching process at the conclusion of said time period, whereby said layer of material is etched to end point on substantially all of said plurality of semiconductor wafers. - View Dependent Claims (5)
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6. A method of etching to end point a layer of material on a plurality of semiconductor wafers in a chamber of the type having a pump for regulating pressure within the chamber, said plurality of semiconductor wafers having a substantially Gaussian thickness distribution, said method comprising the steps of:
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monitoring an intensity of emission of a species produced during an etching process; detecting a first time at which end point occurs on a first one of said plurality of semiconductor wafers, said first one having a layer thickness essentially equal to the minimum thickness in said substantially Gaussian thickness distribution; detecting a second time at which an inflection point in such intensity of emission occurs; calculating a time period extending in length from the time of said inflection point to a time at which end point occurs on a second one of said plurality of semiconductor wafers, said second one having a layer thickness essentially equal to the maximum thickness in said substantially Gaussian thickness distribution; continuing the etching process past the time at which said inflection point is detected for a length of time corresponding to said time period; and terminating the etching process at the conclusion of said time period, whereby said layer of material is etched to end point on substantially all of said plurality of semiconductor wafers. - View Dependent Claims (7)
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Specification