Coherent light generators – Particular active media – Gas
Reexamination Certificate
2002-09-26
2004-03-02
Scott, Jr., Leon (Department: 2828)
Coherent light generators
Particular active media
Gas
Reexamination Certificate
active
06700916
ABSTRACT:
BACKGROUND
1. Field of the Invention
Software control systems and software are described below, and particularly control systems that facilitate exposure radiation control software development for R & D stage exposure sources, increase exposure radiation source system uptimes, provide reliable spectra for monitoring exposure radiation parameters and/or reduce control system software development time and costs.
2. Description of the Related Art
Semiconductor manufacturers are currently using deep ultraviolet (DUV) lithography tools based on KrF-excimer laser systems operating around 248 nm, as well as the following generation of ArF-excimer laser systems operating around 193 nm. Vacuum UV (VUV) will use the F
2
-laser operating around 157 nm. Extreme UV (EUV) will likely use exposure radiation sources generating radiation beams at wavelength between 11 nm and 15 nm.
The short wavelengths are advantageous for photolithography applications because the critical dimension (CD), which represents the smallest resolvable feature size producible using photolithography, is proportional to the wavelength. This permits smaller and faster microprocessors and larger capacity DRAMs in a smaller package. The high photon energy (i.e., 7.9 eV) is also readily absorbed in high band gap materials like quartz, synthetic quartz (SiO
2
), Teflon (PTFE), and silicone, among others, such that the excimer and molecular fluorine lasers have great usefulness presently and even greater potential in a wide variety of materials processing applications.
Higher energy, higher stability, and higher efficiency excimer and molecular fluorine lasers are being developed as lithographic exposure tools for producing very small structures as chip manufacturing proceeds into the 0.18 micron regime and beyond. Specific characteristics of laser systems sought to be improved upon particularly for the lithography market include higher repetition rates, increased energy stability and dose control, increased percentage of system uptime, narrower output emission bandwidths, improved wavelength and bandwidth accuracy, and improved compatibility with stepper/scanner imaging systems.
Various components and tasks relating to today's lithography laser systems are increasingly designed to be computer- or processor-controlled. The processors are programmed to receive various inputs from components within the laser system, and to signal those components and others to perform adjustments such as gas mixture replenishment, discharge voltage control, burst control, alignment of resonator optics for energy, linewidth or wavelength adjustments, among others.
Many of the control procedures that the processors of these laser systems are involved in are “feedback” subroutines. That is, a parameter is monitored and the same or a different parameter is controlled by processor commands to system components based on the value of the monitored parameter. Often the processor commands that control the controlled parameter also affect the monitored parameter, they are the same parameter, and thus the feedback subroutines are continuously monitoring and adjusting the system.
It is recognized in the present invention, that there is a difficulty with developing software control programs particularly for feedback subroutines for use with laser systems that are still in the R & D stage and not yet fully operational. That is, input parameters cannot be received by the processor from a fully operational laser system, which is the intended purpose of the feedback control software being developed, until a working laser is actually up and running. At the same time, it presents an undesirable delay in the marketing of new, improved lasers when software development for the processor control of the new lasers is undertaken only after the laser hardware package is otherwise fully developed. It is desired to have a way to develop processor control software for next generation industrial lasers in parallel with the development of the lasers themselves.
Both the chip production processing and the operation of the laser system require some specifically ascribed downtime periods. For the chip processing, maybe the masks or reticles need to be aligned or changed, the substrate sheets changed or the imaging optics adjusted. For the laser system, maybe a new gas fill or partial gas replacement, or scheduled service on the optics or electrical system is required, or beam alignment or wavelength calibration requiring some offline servicing is expected.
The imaging system and/or chip manufacturer typically informs the laser manufacturer what the processing schedule (time schedule for periods of exposure and non-exposure, or uptimes and downtimes) will be for a particular customer order. It is recognized in the present invention that both the laser system and chip processing downtime periods work against the overall goal of maximizing the uptime of the overall system. While some downtime may be unavoidable due to scheduled or unexpected servicing needs of the system, it is desired to have a system where only the minimum amount of downtime is incurred for scheduled servicing of the system.
Each customer who orders a lithography laser system typically supplies a list of commands or command sequences corresponding to various functions required of the laser that are input to the control processor of the laser from an external controller, e.g., at the fab. Each customer typically assigns a different command or command sequence to common functions of the laser system. Software packages including unique laser control modules for each different customer's command/command sequence list are conventionally created consuming a large amount of software development time and cost. In addition, different components of lithography lasers or exposure radiation sources systems may use different software programs and/or protocols or communication hardware and/or software packages. It is desired to reduce software development time and cost, particularly for facilitating communications between monitor computer systems and different components of the laser or exposure radiation systems and/or with different customer stepper/scanner computer systems.
It is important for their respective applications to the field of sub-quarter micron silicon processing that each of the above laser systems become capable of emitting a narrow spectral band of known bandwidth and around a very precisely determined and finely adjustable absolute wavelength. Techniques for reducing bandwidths by special resonator designs to less than 100 pm for use with all-reflective optical imaging systems, and for catadioptric imaging systems to less than 0.6 pm, are being continuously improved upon. Depending on the laser application and imaging system for which the laser is to be used, line-selection and/or line-narrowing techniques are described at U.S. patent applications Ser. Nos. 09/317,695, 09/317,527, 09/130,277, 09/244,554, 09/452,353, 09/602,184, 09/599,130 and 09/629,256, and U.S. Pat. Nos. 5,761,236, 6,081,542, 6,061,382 and 5,946,337, each of which is assigned to the same assignee as the present application, and U.S. Pat. Nos. 5,095,492, 5,684,822, 5,835,520, 5,852,627, 5,856,991, 5,898,725, 5,901,163, 5,917,849, 5,970,082, 5,404,366, 4,975,919, 5,142,543, 5,596,596, 5,802,094, 4,856,018, and 4,829,536, all of which are hereby incorporated by reference. Some of the line selection and/or line narrowing techniques set forth in these patents and patent applications may be used in combination.
Techniques are also available for tuning and controlling central wavelengths of emission. Absolute wavelength calibration techniques use a known absorption or emission line around the wavelength of interest as a reference (see U.S. Pat. Nos. 4,905,243, 4,926,428, 5,450,207, 5,373,515, 5,978,391, 5,978,394 and 4,823,354, and F. Babin et al., Opt. Lett., v. 12, p. 486 (1987), and R. B. Green et al., Appl. Phys. Lett., v. 29, p. 727 (1976), as well as U.S. patent applications Ser. Nos. 09/416,344 and 09/271,020 (each applicati
Kleinschmidt Juergen
Kramer Matthias
Nowinski Günter
Serwazi Marcus
Jr. Leon Scott
Lambda Physik AG
Stallman & Pollock LLP
LandOfFree
E-diagnostic, laser simulator, automated testing and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with E-diagnostic, laser simulator, automated testing and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and E-diagnostic, laser simulator, automated testing and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3224930