Source: http://www.google.com/patents/US6891172?ie=ISO-8859-1
Timestamp: 2014-03-14 03:26:33
Document Index: 710317449

Matched Legal Cases: ['art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 310', 'art 310']

Patent US6891172 - Differential pumping system and exposure apparatus - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA differential pumping system includes a first chamber for storing a light source that emits pulsed light, a first exhaust unit for exhausting said first chamber, a second chamber being connectible to the first chamber to receive the pulsed light, a second exhaust unit for exhausting said second chamber,...http://www.google.com/patents/US6891172?utm_source=gb-gplus-sharePatent US6891172 - Differential pumping system and exposure apparatusAdvanced Patent SearchPublication numberUS6891172 B2Publication typeGrantApplication numberUS 10/652,690Publication dateMay 10, 2005Filing dateAug 28, 2003Priority dateSep 3, 2002Fee statusPaidAlso published asDE60334592D1, EP1396758A2, EP1396758A3, EP1396758B1, US20040046949Publication number10652690, 652690, US 6891172 B2, US 6891172B2, US-B2-6891172, US6891172 B2, US6891172B2InventorsNobuaki Ohgushi, Akira Miyake, Takayuki Hasegawa, Jun ItoOriginal AssigneeCanon Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (21), Non-Patent Citations (1), Referenced by (7), Classifications (21), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetDifferential pumping system and exposure apparatusUS 6891172 B2Abstract A differential pumping system includes a first chamber for storing a light source that emits pulsed light, a first exhaust unit for exhausting said first chamber, a second chamber being connectible to the first chamber to receive the pulsed light, a second exhaust unit for exhausting said second chamber, and a connection control mechanism between the first and second chambers for connecting the first chamber to the second chamber when the pulsed light emits, and for disconnecting the first chamber from the second chamber when the pulsed light does not emit.
BACKGROUND OF THE INVENTION The present invention relates to exposure apparatuses that exposes an object, such as a single crystal substrate for a semiconductor wafer, and a glass plate for a liquid crystal display (�LCD�). The present invention is particularly suitable, for example, for an exposure apparatus that uses ultraviolet light and extreme ultraviolet (�EUV�) light as a light source for exposure.
BRIEF SUMMARY OF THE INVENTION Accordingly, it is an exemplary object of the present invention to provide a differential pumping system and an exposure apparatus having the same, in which the use efficiency of the high pulsed light is compatible with the differential pumping having an intended pressure difference so as to maintain performance of an optical element, such as reflectivity.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to accompanying drawings, a description will now be given of a differential pumping system 1 of one embodiment according to the present invention. In each figure, the same element is designated by the same reference numeral, and a description thereof will be omitted. Here, FIG. 1 is a schematic structure of the differential pumping system 1.
C12≦10−3 (8) The conductance of the channel part 150 should be less than {fraction (1/1000)} times the pumping speed of the vacuum pump 202 connected to the illumination system chamber 200. The simplified equation of the conductance C12 is expressed by Equation 9 where the channel part 150 has a radius �a� (m) and a length L (m):
2a/L≧tan 15� (11) From Equations 10 and 11, a permissible range of the length L of the channel part 150 may be defined by the radius �a� of the channel part 150 as in Equation 12:
106 �a 3 ≦L≦2a/tan 15�=7.46a (12) FIG. 4 shows a range that suffices the inequality in Equation 12. The range in Equation 12 corresponds to an area A in FIG. 4 in which a=2.76 (mm) and L=21 (mm) where the radius �a� and the length L of the channel part 150 become maximum. This range makes the alignment of the optical axis difficult, and does not provide much tolerance to the beam size b12 of 0.8 (mm).
2.56�104 �a 3 ≦L≦2a/tan 15�=7.46a (14) FIG. 4 shows a range that suffices the inequality in Equation 14. The range in Equation 14 corresponds to an area B in FIG. 4 in which �a�=17.3 (mm) and L=129 (mm) where the radius �a� and the length L of the channel part 150 become maximum. Apparently, this range does not make the alignment of the optical axis difficult and has enough tolerance to the beam size b12 of 0.8 (mm). This may further reduce the conductance of the channel part 150 for a pressure difference of 103 Pa or greater, and lowers a reduced pumping speed to miniaturize the vacuum pumps 113 and 202. Here, FIG. 4 is a graph showing a relationship between the radius and length of the channel part 150, and FIG. 5 is an explanatory view of one design example of the disc 310.
A description will be given of a control method 2000 that controls a rotation of the disc 310 in the connection control mechanism 300 with reference to FIGS. 6 to 11. FIG. 6 is a flowchart for explaining the control method 2000 for controlling a rotation of a disc 310 in a connection control mechanism 300. FIG. 7 is a control block diagram for highly precise synchronization between light emissions of the EUV light 108 and a phase of the disc 310. Such a control method that adjusts a phase is generally referred to as a phase locked loop (�PLL�).
The reference clock is divided by the Nr divider 1004, and a reference signal of the disc 310 is generated (step 2002). A division ratio is determined within an operational range of the sensor 322 that detects set accuracy of a phase and an offset phase. As shown in FIG. 1, the sensor 322 monitors an aperture part 310 a that offsets by half-turn from an aperture part 310 through which the EUV light 108 passes, and an operational range of the sensor 322 is determined by an aperture diameter of the opening 310 a. The disc 310's rotation 1008 is monitored by an encoder 1009, and divided by an Ne divider 1010 that is set so that it has the same frequency as the reference signal. Two divided signals are input to a phase comparator 1011 for exclusive OR operations, providing a waveform shown in a fifth stage in FIG. 8. The duty ratio of this pulse waveform is phase difference information: When this signal passes through a low-pass filter (�LPF�), then a phase difference signal is obtained as shown in a sixth stage in FIG. 8 (step 2004). The phase difference signal is fed back, as shown in FIG. 7, and a deviation from a phase command value 1005 is calculated as a phase difference (step 2006). This embodiment sets the phase difference command to 90�, and the controller 320 that also serves as a phase controller 1006 controls so that the phase difference is the phase set value. The hardware of the controller 320 includes an analog circuit or DSP, and the analogue circuit uses Proportional Integral and Differential (�PID�) control for control operations, while the DSP uses a modern control, such as PID control, optimal regulator and H� control for control operations. The motor 314's driving 1007 is controlled in accordance with the control amount from the controller 320, or so that a phase difference is the phase set value (Step 2008).
When a command value is input to the exposure dose control 2102 from an exposure dose control value 2101 in the upper-stage control loop, the exposure dose control 2102 outputs a value corresponding to the command value. When the value is input into the voltage control oscillator (�VCO�) 2103, a reference clock (or frequency data in a first stage in FIG. 25) is output in synchronization with the exposure dose command value. The emission clock (in a second stage in FIG. 25) for emissions of the light source is generated from the Nt divider 2104 using the frequency data. The EUV light source 2105 emits at timing in synchronization with this emission clock, and is fed back, via a light integrate (�LI�) sensor 2106 that always detects the exposure dose (light energy amount or a corresponding value) in the illumination system and a LPF 2107, to an control operation 2113, which provides a PID control for desired exposure dose and highly precise light amount adjustment. A method to control oscillation timing of the pulsed light source is as described above in accordance with the exposure dose value.
The inventive exposure apparatus 800 is a projection exposure apparatus that uses EUV light with a wavelength of 13.4 nm as exposure light for step-and-scan or step-and-repeat exposure of a circuit pattern formed on the mask 820 onto an object 840 to be exposed. This exposure apparatus is suitable for a lithography process less than submicron or quarter micron, and the present embodiment uses the step-and-scan exposure apparatus (also referred to as a �scanner�) as an example.
The �step-and-scan�, as used herein, is an exposure method that exposes a mask pattern onto a wafer by continuously scanning the wafer relative to the mask, and by moving, after a shot of exposure, the wafer stepwise to the next exposure area to be shot. The �step-and-repeat� is another mode of exposure method that moves a wafer stepwise to an exposure area for the next shot every shot of cell projection onto the wafer.
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