System and method of determining effective glow discharge lamp current
AssigneeLeco Corporation
InventorsTed J Casper, Sara K Casper, Kim Marshall
Life of this patent
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Abstract
The embodiments of the invention include a method for controlling plasma conditions of a glow discharge system using the integrated electron (or ion) pulse area extracted from the total lamp current. The method of using an integrated electron/ion pulse area for controlling plasma conditions allows for controlled analysis of conductive, non-conductive and layered materials without the need for estimation of plasma voltages. The method allows for control of sputter rates and plasma emissions that cannot be achieved using other methods such as capacitive divider calculations where actual thicknesses and dielectric constants are not known or predefined.
Claims17
A glow discharge lamp system comprising:
- a glow discharge lamp for ionizing a sample of a material to be analyzed in a plasma;
- an RF power supply for supplying RF power to the glow discharge lamp at a power level selected in response to an RF output control signal;
- a lamp current sensor for sensing a total lamp current and generating a total lamp current signal representative of the total lamp current over time;
- and
- a processor for receiving the total lamp current signal from said lamp current sensor and for supplying the RF output control signal to said RF power supply, wherein said processor determines an integrated pulse area of a pulse contained within the total lamp current signal and adjusts the RF power supplied to the glow discharge lamp in response to the integrated pulse area, wherein the pulse is one of an electron pulse and an ion pulse.
A method for controlling plasma conditions of a glow discharge lamp comprising:
- measuring a total lamp current of the glow discharge lamp;
- determining an integrated pulse area contained within the total lamp current using a processor;
- measuring an effective plasma power of the glow discharge lamp;
- and
- adjusting a pressure of the glow discharge lamp as to alter at least one of the effective plasma power and the integrated pulse area, wherein the integrated pulse area is one of an integrated electron pulse area and an integrated ion pulse area.
A method of calibrating an integrated pulse area from a total lamp current of a glow discharge lamp system to a quotient of effective plasma power divided by effective voltage, wherein the integrated pulse area is one of an integrated electron pulse area and an integrated ion pulse area, the method comprising:
- measuring effective plasma power, integrated pulse area, and effective voltage on a conductive sample at no fewer than one plasma operating point;
- controlling the at least one plasma operating point by varying at least one of a pressure of the glow discharge lamp system and the effective plasma power;
- using the quotient of effective plasma power divided by effective voltage to determine effective plasma current using a processor in communication with the glow discharge lamp system;
- and
- using the processor to create a mathematical function or table relating the integrated pulse area to the effective plasma current and storing the mathematical function or table in a memory device.
A method of calibrating an integrated pulse area from a total lamp current of a glow discharge lamp system to an effective plasma current, wherein the integrated pulse area is one of an integrated electron pulse area and an integrated ion pulse area, the method comprising:
- measuring effective plasma power, integrated pulse area, and effective voltage on a conductive sample at no fewer than one plasma operating point;
- controlling the at least one plasma operating point by varying at least one of a pressure of the glow discharge lamp system and the effective plasma power;
- using a quotient of effective plasma power divided by effective voltage to determine effective plasma current using a processor in communication with the glow discharge lamp system;
- and
- using the processor to create a mathematical function or table relating the integrated pulse area to the effective plasma current and storing the mathematical function or table in a memory device.
A method for determining an integrated pulse area of a pulse contained within a total lamp current signal of a glow discharge lamp, wherein the pulse is one of an electron pulse and an ion pulse, the method comprising:
- continuously calculating a sum of the total lamp current signal using a processor in communication with the glow discharge lamp;
- determining a start time of the pulse;
- determining an end time of the pulse;
- and
- determining the integrated pulse area using the processor by subtracting a value of the sum found at the start time of the pulse from a value of the sum found at the end time of the pulse.
Dependencies are inferred from the claim text.