US6028880A — Automatic fluorine control system

Claim 1

Independent Claim 212 words

An excimer laser system comprising: A) a laser chamber containing: 1) two spaced apart elongated electrodes; 2) a laser gas comprising: a noble gas, fluorine, a buffer gas; B) a blower for flowing the laser gas between the two spaced apart electrodes; C) a high-pressure fluorine source comprising a gas mixture at high pressure, said mixture comprising fluorine, said noble gas and said buffer gas; D) a gas inject manifold including an inject bottle having a volume of at least 0.3 liters and providing gas flow communication between said fluorine source and said inject bottle and between said inject bottle and said laser chamber; E) a fluorine monitoring means for monitoring changes in fluorine concentration in the chamber substantially continuously at least during laser operation; and F) a fluorine feedback control system including at least one low flow fluorine inject flow control valve, said system being programmed to automatically control fluorine flow from said fluorine source into said inject bottle and to control fluorine injection flow from said inject bottle into said laser chamber at a continuous or a substantially continuous rate based on feedback information from said fluorine monitoring means in order to permit said laser to operate within a desired sweet spot determined by fluorine concentration in the laser chamber.

Claim 2

Dependent Claim 212 words

An excimer laser system comprising: A) a laser chamber containing: 1) two spaced apart elongated electrodes; 2) a laser gas comprising: a noble gas, fluorine, a buffer gas; B) a blower for flowing the laser gas between the two spaced apart electrodes; C) a high-pressure fluorine source comprising a gas mixture at high pressure, said mixture comprising fluorine, said noble gas and said buffer gas; D) a gas inject manifold including an inject bottle having a volume of at least 0.3 liters and providing gas flow communication between said fluorine source and said inject bottle and between said inject bottle and said laser chamber; E) a fluorine monitoring means for monitoring changes in fluorine concentration in the chamber substantially continuously at least during laser operation; and F) a fluorine feedback control system including at least one low flow fluorine inject flow control valve, said system being programmed to automatically control fluorine flow from said fluorine source into said inject bottle and to control fluorine injection flow from said inject bottle into said laser chamber at a continuous or a substantially continuous rate based on feedback information from said fluorine monitoring means in order to permit said laser to operate within a desired sweet spot determined by fluorine concentration in the laser chamber.

Claim 3

Dependent Claim 36 words

An excimer laser system as in claim 1 wherein said fluorine monitoring means comprises a voltage monitor for monitoring a voltage level in a high voltage power system providing high voltage pulses to said elongated electrodes.

Claim 4

Dependent Claim 107 words

An excimer laser system as in claim 1 wherein said fluorine and buffer gas in said laser gas in said chamber defines a fluorine-buffer gas chamber ratio and said noble gas and said buffer gas in said laser gas in said chamber defines a noble gas-buffer gas chamber ratio and said fluorine and buffer gas in said fluorine source defines a fluorine-buffer gas source ratio which is substantially greater than said fluorine-buffer gas chamber ratio and said noble gas and said buffer gas in said fluorine source defines a noble gas-buffer gas ratio which is equal to or approximately equal to said noble gas-buffer gas chamber ratio.

Claim 5

Dependent Claim 18 words

An excimer laser system as in claim 3 wherein said fluorine-buffer gas ratio is in excess of 5%.

Claim 6

Dependent Claim 21 words

An excimer laser system as in claim 3 wherein said fluorine-buffer gas ratio is a ratio corresponding to substantially 100% fluorine.

Claim 7

Dependent Claim 20 words

An excimer laser system as in claim 1 wherein the noble gas is krypton and said buffer gas is neon.

Claim 8

Dependent Claim 20 words

An excimer laser system as in claim 1 wherein the noble gas is argon and said buffer gas is neon.

Claim 9

Dependent Claim 34 words

An excimer laser system as in claim 1 wherein said feedback control system comprises temperature and pressure sensors and a processor programmed to adjust fluorine injection based on temperature deviations from a reference temperature.

Claim 10

Dependent Claim 25 words

An excimer laser system as in claim 1 wherein said sweet spot is defined by a slope of a voltage vs. F 2 concentration curve.

Claim 11

Dependent Claim 48 words

An excimer laser system as in claim 9 wherein said feedback control sytem is programmed to inject fluorine at intervals close enough together to simulate continuous injection in order to permit a voltage defined sweet spot no larger than about 2 percent of the nominal sweet spot voltage.

Claim 12

Dependent Claim 21 words

An excimer laser system as in claim 1 wherein said inject bottle has a gas volume of more than 0.5 liters.

Claim 13

Dependent Claim 22 words

An excimer laser system as in claim 1 and further comprising a bleed bottle having a volume of more than 0.3 liters.

Claim 14

Dependent Claim 43 words

An excimer laser system as in claim 1 and further comprising gas piping permitting gas flow from a relatively high pressure location of said chamber to said inject bottle and from said inject bottle to a relatively low pressure location of said chamber.

Claim 15

Dependent Claim 26 words

An excimer laser system as in claim 1 wherein said feedback fluorine control system is programmed to increase the chamber gas pressure as the chamber ages.

Claim 16

Dependent Claim 21 words

An excimer laser system as in claim 1 and further comprising multiple injection ports inside the laser chamber for injecting fluorine.

Claim 17

Dependent Claim 22 words

An excimer laser system as in claim 1 wherein said fluorine control system comprises a processor programmed with a slope seeking algorithm.

Claim 18

Dependent Claim 45 words

An excimer laser system as in claim 1 wherein said fluorine control system comprises a processor programmed with a program for injecting a precise quantity of fluorine, .increment.F 2 , when discharge voltages have increased by a predetermined increment, .increment.V from a predetermined discharge voltage.

Claim 19

Dependent Claim 19 words

An excimer laser system as in claim 17 wherein said discharge voltages are estimated using values of control voltages.

Claim 20

Dependent Claim 140 words

A process for controlling fluorine concentration in an excimer laser gas, comprised of at least two noble gases and fluorine, contained in a laser chamber comprising the steps of: A) monitoring the fluorine concentration with a real time or substantially real time monitor to provide a real time fluorine concentration value; B) periodically calibrating said real time or substantially real time fluorine monitor with a fluorine detector; C) providing precise fluorine injections from fluorine source, including fluorine, a noble gas and a buffer gas, through a manifold including an inject bottle into the laser chamber or a continuous or substantially continuous basis; D) controlling the fluorine injections with a control system to maintain fluorine concentration within a sweet spot; and E) discharging portions of said laser gas from the chamber in order to maintain approximately constant pressure in the chamber.

Claim 21

Dependent Claim 140 words

A process for controlling fluorine concentration in an excimer laser gas, comprised of at least two noble gases and fluorine, contained in a laser chamber comprising the steps of: A) monitoring the fluorine concentration with a real time or substantially real time monitor to provide a real time fluorine concentration value; B) periodically calibrating said real time or substantially real time fluorine monitor with a fluorine detector; C) providing precise fluorine injections from fluorine source, including fluorine, a noble gas and a buffer gas, through a manifold including an inject bottle into the laser chamber or a continuous or substantially continuous basis; D) controlling the fluorine injections with a control system to maintain fluorine concentration within a sweet spot; and E) discharging portions of said laser gas from the chamber in order to maintain approximately constant pressure in the chamber.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2003-02-21	2003-08-23	2004-02-22	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2007-02-21	2007-08-23	2008-02-22	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2011-02-21	2011-08-23	2012-02-22	$7700.00	Window Closed / Lapsed

Automatic fluorine control system

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