A windowless excilamp, a xenon excilamp with the high specific power of radiation and an air-cooling KrCl excilamp
for microelectronic applications are described. The excilamps have the total radiating surface up to 900 cm2. The VUV
specific average power of a windowless excilamp is 3 mW/cm2 and 5 mW/cm2 for argon (λ ~ 126 nm) and krypton (λ~146 nm) accordingly at distance of 3 cm from the emitting surface. The xenon excilamp (λ ~ 172 nm) has 50 W of the average total VUV power and 120 mW/cm2 of density and the
large-aperture air-cooling KrCl (λ ~222 nm) excilamp has
30 mW/cm2 of the radiation density and the radiation homogeneity 12 %.
Emission characteristics of a nanosecond discharge in nitrogen, inert gases and its halogenides without preionization of
the gap from an auxiliary source have been investigated. A volume discharge, initiated by an avalanche electron beam
(VDIAEB) was realized at pressures up to 12 atm. It has been shown that at VDIAEB excitation no less than 90%
energy in the 120-850 nm range is emitted by Xe, Kr, Ar dimers. Xenon spectra in the range 120-850 nm and time-amplitude
characteristics have been recorded and analyzed for various excitation regimes. In xenon at pressure of 1.2
atm, the energy of spontaneous radiation in the full solid angle was ~ 45 mJ/cm3, and the FWHM of a radiation pulse
was ~ 110 ns. The spontaneous radiation power rise in xenon was observed at pressures up to 12 atm. Pulsed power
densities of radiation of inert gases halogenides excited by VDIAEB was ~ 4.5 kW/cm2 at efficiency up to 5.5 %.
Pre-production models of excilamps developed in the laboratory of optical
radiation are described; main characteristics of radiators and their power supplies,
portable UV-excilamps of the barrier or capacitive discharges, and also powerful VUV-excilamps
of the barrier discharge which can be used for cleaning or modifying material
surfaces are presented.
Efficient radiation of Xe2*, KrBr*, KrCl*, XeI*, Cl2, XeBr*, XeCl* molecules and Iodine atoms was obtained. Some types of UV and VUV excilamps with different discharge geometry excited by capacitive discharge, barrier discharge and glow discharge are presented.
A discharge in high-pressure xenon excilamps is studied experimentally and theoretically. In the absence of an additional source of xenon preionization, the volume discharge is produced in the form of a diffuse cloud or diffuse cones at pressures of several hundreds of torrs. Under these conditions, radiation is emitted with a high efficiency within the VUV spectral range. The results of simulations have shown that, at the pressure on the order of 100 Torr and the field voltage on the order of 10 kV/cm, the established near-cathode layer is on the order of several tens of microns, which is much less than the wire radius. The cathode layer, the potential drop in the near-cathode area is much lower than the voltage applied to the discharge gap. We put forward a hypothesis that the formation of the volume discharge is due to the presence of dense plasma in the near-cathode area, and this plasma plays the role of a plasma cathode.
Pulse repetitive generators with inductive energy storage unit and semiconductor opening switch were developed and used for pumping lasers on CO2, N2, Cu vapor laser and VUV Xe excilamp. For the first time, operation of the generators at pulse repetition rate up to 100 kHz has been realized. Improvement of the laser and excilamp output parameters were achieved.
At present time, excilamps excited by a barrier discharge are the simplest and perspective as the sources of UV and VUV radiation. Much research is devoted to such excilamps. Traditionally, sinusoidal oscillators are used as excitation sources. The present work devoted to study the impact of excitation pulse form and other conditions on efficiency of a barrier KrCl and XeCl excilamps. The main results of the work performed are the following. The most high specific radiation power values were obtained at the excitation at the excilamp by voltage pulses of different polarity at maximum pulsed repetition rate (p.r.r) of 100 kHz, and made depending on operating conditions of excilamp, up to 120 mW/cm3. From the oscilloscope traces of voltage pulses, current and radiation it is seen that radiation is being registered within the whole current pulse duration. The most high values of average radiation power and efficiency were achieved, correspondingly, 100 W and 13%. Influence of pulse repetition rate of excitation of different temporal mode on the type of formed discharge, as well as efficiency and output parameters of Xe-Cl2 barrier discharge excilamp were studied. It has been found that at pulsed repetition rate of about 1 kHz and higher there are brightly glowing microdischarges - filaments observed in the discharge plasma. With this, the efficiency of excilamp practically keeps unchanged in the frequency range <EQ 1 kHz and monotonously decays either at further increase of excitation p.r.r. or at excitation power increase for the fixed frequency of excitation pulses.
In the present paper, Iodine XeI*, XeCl*, KrCl barrier, glow and capacitive discharge excilamps have been studied. Xe-I2 or Xe-He-I2 excilamps emit at iodine monatomic resonance lines in the range of 180-210 nm, and on XeI molecule band. Besides that, by varying pressure and mixture composition, it is possible to control relation between iodine monatomic lines and XeI* molecule band radiation intensity. The efficiency level is up to 12 percent. The lifetime in sealed-off excilamps was more 1000 h. It is shown that at barrier KrCl and XeCl excilamps excitation by short unipolar or bipolar voltage pulse the efficiency is higher than by sine pulses excitation. Output at (lambda) approximately 222 nm up to 100 W and at 308 nm up to 75 W from barrier discharge excilamps was obtained. Presence of filaments occurs to be a necessary condition to obtain high efficiency since in that case a demanded level of excitation specific power is being achieved. Radiation pulse delay relatively to excitation in the conditions of homogeneous discharge probably demonstrates low efficiency of KrCl* and XeCl* molecules formation at a low level of excitation power. Output at (lambda) approximately 222 nm up to 190 W and at 308 nm up to 91 W from glow discharge excilamps was demonstrated.
The paper is devoted to experimental study of discharge and radiation characteristics taking place in Xe one-barrier excilamps at broad variations of excitation pulse parameters and gas fill-pressures. The B-X band of the molecule Xe2* dominates the lamp spectrum and has high efficiency. Radiation of monatomic lines and luminescence of the lamp bulb can be observed too. The molecule Xe2* band B-X radiation of luminescence time dependence and luminescence of the lamp bulb quartz are similar, at the same time the radiation of Xe monatomic line (lambda) equals 467 nm has obviously some other form. Depending on excitation conditions, i.e. power, duration and excitation impulse form, a gas discharge Xe excilamp, different by homogeneity level and radiation efficiency types of discharge can be realized. Formation of discharge homogeneity is the necessary condition to obtain high efficiencies of excimer radiation in this type of lamp. In one-barrier xenon excilamps with internal small curvature of an electrode, a homogeneous discharge forms at pressures up to 300 Torr.
Excitation pulse form and power and some other discharge parameters influence on barrier discharge KrC1 excilamp efficiency was studied in present paper. It is shown that at barrier KrC1 excilamp excitation by short (2÷2,5 µs) unipolar or bipolar voltage pulses the efficiency is higher than by sine pulses excitation. Presence of filaments occurs to be a necessary condition to obtain high efficiency since in that case a demanded level of excitation specific power is being achieved. Radiation pulse delay relatively to excitation in the conditions of homogeneous discharge probably demonstrates low efficiency of KrCl* molecules formation at a low level of excitation power.
Power characteristics of four excilamps with short-pulse duration discharge plasma radiation have been investigated experimentally. At mixture pressure of 30 Torr the radiation pulse power density has made at (lambda) approximately 222 nm 0.2 kW/cm2, 0.15 kW/cm2, 0.09 kW/cm2 for I-, H- and L-type excilamps, respectively. The maximal radiation pulse power density was received for modernized I-type excilamp and it has made 0.3 kW/cm2. It has been revealed that pulse radiation output is mostly determined by excilamp voltage value, discharge geometry, value of peaking capacitance, and gas medium density.
The possibility of creation of capacitive discharge excilamps with short pulse duration was studied. There were three types of pulsed excilamps in experiments: cylindrical glow discharge lamp, capacitive discharge lamp, high pressure volume discharge planar lamp with UV-preionization of discharge gap. In capacitive discharge cylindrical KrCl-excilamp, at (lambda) approximately 222 nm the radiation pulse power through the end face of a lamp up to 2.5 kW has been obtained. Powerful radiation pulses of 50 ns in duration were obtained at pulse repetition rate of 1 kHz. In case of high pressure volume discharge at operating pressure of several atmospheres the radiation peak power density values were as much as 5 kW/cm2 at (lambda) approximately 250 nm, and 3.5 kW/cm2 at (lambda) approximately 222 nm and at (lambda) approximately 308 nm. In cylindrical longitudinal excilamp with inner electrodes with Xe- I2 mixture the total pulse power of 75 kW has been obtained. The first experiments with harnessing of inductive energy stores for excilamp excitation have been carried out.
Investigation was made ofthe characteristics ofXeCl (λ ~ 308 nm), KrC1 (λ ~ 222 nm) and Xci (λ ~ 253 nm) capacitive discharge excilamps. High efficiency of exciplex molecules and simple design have been obtained under capacitive HF discharge excitation. Cylindrical excilamps with radiation output through side surface ofthe cylinder and through one or two windows placed on the tube ends have been developed. High UV radiation power and electrical power deposition to fluorescence conversion resulted in efficiencies of up
to 12%. The study of XeC1, KrCl and XeI excilamps have shown, that it is possible to create sealed-off samples with lifetime more than 1000 hours. The stability of output parameters ofthe capacitive discharge excilamps is studied and the mechanism of chlorine losses in low pressure halogencontaimng excilamps made of quartz was determined.
The possibility of creation of capacitive discharge excilamps with short pulse duration was studied. In capacitive discharge cylindrical KrClexcilamp, at λ~222 nm the radiation pulse power up to 2.5 kW was obtained. Powerful radiation pulses 50 ns in duration were obtained at pulse repetition rate of 1 kHz.