W. L. Wilson

An Integrated CAD Framework Linking VLSI Layout Editors and Process Simulators

As feature sizes in VLSI circuits extend into the far sub-micron range, new process techniques, such as using phase shifted masks for photolithography, will be needed. Under these conditions, the only means for the circuit designer to design compact and efficient circuits with good yield capabilities is to be able to see the effect of different design approaches on manufactured silicon, instead of solely relying on conservative general design rules. The integrated CAD framework accomplishes this by providing a link between a layout editor (Magic), advanced photolithographic techniques such as phase shifted masks, and a process simulator (Depict). This paper discusses some applications of this tool. A non- conventional process technique involving interferometric phase shifting and off-axis illumination has been evaluated using the tool. Also, a feature of the CAD framework which allows representation of a phase shifted mask, together with its layout analysis capability has been used to compact a piece of layout by inserting phase shifted elements into it.

A triatomic Xe2Cl excimer laser in the visible

A new triatomic rare‐gas halide laser using the molecular exciplex Xe2Cl is described. Laser emission centered at 518 nm with a special bandwidth of 30 nm and peak power of about 2 kW was obtained from an electron‐beam‐excited high‐density Ar/Xe/CCl4 mixture.

Excimer laser photoablation of silicon

The ultraviolet and visible emission spectra from excimer laser‐produced silicon plasmas were studied and the ablation rate measured as a function of laser energy density and wavelength. A spectroscopic investigation of the laser‐produced plasma showed Si i, Si ii, and Si iii spectral lines with higher laser intensity causing a higher degree of ionization in the plasma. Both time‐integrated and time‐resolved spectroscopic studies showed electronic transitions superimposed on a weak continuum over the entire range from 250 to 640 nm. The photoablation rate of Si was independent of laser wavelength (193 or 248 nm), and had an energy density threshold of ≊1.3 J/cm2. The threshold was almost independent of the buffer gas pressure between vacuum and 1000 Torr. These results are described in the framework recently developed for excimer laser ablation of metals.

Efficient XeF(C→A) laser oscillation using electron‐beam excitation

Significantly improved XeF(C→A) laser energy density and efficiency have been obtained using electron‐beam excited Ar‐Xe gas mixtures at pressures up to 10 atm which contain both NF3 and F2. Maximum blue‐green laser pulse energy density in excess of 1.0 J/liter was obtained, corresponding to an intrinsic electrical‐optical energy conversion efficiency estimated to be in the 0.5%–1.0% range. Comprehensive, time‐resolved absolute measurements of XeF(C→A) fluorescence, laser energy, and gain were carried out for a wide variety of experimental conditions. Analysis of these data has resulted in identification of the dominant transient absorbing species in the laser medium. For the laser mixtures investigated in this work, the primary blue/green absorption processes have been identified as photoionization of the 4p, 3d, and higher lying states of Ar, and of the Xe 6p and 5d states, and photodissociation of Ar2(3∑+u) and Ar+3.

Electron beam pumped broad-band diatomic and triatomic excimer lasers

The spontaneous and stimulated emission characteristics of three recently reported broad-band blue-green rare gas-halide excimers, XeF ( C \rightarrow A ) at 486 nm, Xe 2 Cl at 518 nm, and Kr 2 F centered at 436 nm, are reviewed. The influence of different halogen donors and buffer gases as well as optimization of both the gas mixture and optical resonator configuration for wavelength tuning were studied. The kinetic mechanisms which describe the formation and quenching of Xe 2 Cl* are discussed. Problems with achieving optimum gain as well as understanding both molecular and atomic absorptions in electron beam excited rare gas-halide mixtures are detailed.

Performance characteristics of an injection-controlled electron-beam pumped XeF(C to A) laser system

Characteristics of an injection-controlled electron-beam pumped XeF(C to A) laser are investigated with emphasis on efficient wideband tuning and scaling issues. Using a quasi-CW dye laser as an injection source, data are obtained that describe the laser characteristics over a wide parameter range. A high-Z electron-beam backscattering reflector inside the laser reaction cell improved the electron-beam energy deposition by 40%, resulting in an increase of the amplified laser output by more than a factor of four. Efficient and continuous wavelength tuning between 470 and 500 nm is achieved with an output energy density of approximately 1 J/l, and an intrinsic efficiency of approximately 1% throughout the entire tuning region. >

Laser gain measurements by means of amplified spontaneous emission

Laser gain determination by means of amplified spontaneous emission is discussed in terms of a rate-equation approach. Numerical solutions show that optical gain can be deduced only for a limited regime of experimental parameters. The theoretical analysis is examined with experimental gain data for organic dyes in the vapor phase and in liquid solution. In addition, the gain of electron-beam-excited Ar-N(2) and XeF laser mixtures has been studied.

Blue laser action by the rare‐gas halide trimer Kr2F

Blue Kr2F excimer laser emission centered at 430 nm has been achieved in electron‐beam‐pumped high‐density Ar/Kr/Nf3 mixtures. An output power of about 5 kW has been obtained. The spectral bandwidth is 25 nm for a simple two‐mirror resonator with a potential tuning range between 380 and 480 nm.

Kinetic processes of electron beam generated XeF* and Xe2F* excimers

Kinetic processes of XeF and Xe2F have been investigated experimentally in electron beam excited Ar/Xe/NF3 mixtures. In Xe/NF3 mixtures no vibrational relaxation was observed in the XeF(B, C) states due to the rapid two‐body quenching of XeF(C) by Xe. Two‐ and three‐body quenching constants of XeF(B, C) were measured for several collision partners. An investigation of the Xe2F production process showed that XeF(C) is the precursor of Xe2F. Formation and quenching rate constants for Xe2F have been determined. The kinetic processes of the XeF–Xe2F system can be described by a relatively simple kinetic model.

Characterization of an ultrahigh peak power XeF(C to A) excimer laser system

The gain characteristics of an electron-beam pumped XeF(C to A) excimer amplifier operating in the blue-green spectral region were investigated for several laser pulse lengths. Saturation energy densities of 50 and 80 mJ/cm/sup 2/ were measured for injected laser pulse durations of 250 fs and approximately 100 ps, respectively. A gain bandwidth of 60 nm was observed with approximately 100-ps pulse injection. Using an optimized unstable resonator design, the laser amplifier has produced 275-mJ pulses with a pulse duration of 250 fs and a 2.5 times diffraction-limited beam quality, making the XeF(C to A) amplifier the first compact laser system in the visible spectral region to reach peak powers at the terawatt level. >