Daniel L. Birx

EUV (13.5-nm) light generation using a dense plasma focus device

A dense plasma focus (DPF) device has been investigated as a source for EUV lithography. Initial characterizations have been made of a prototype DPF employing an all-solid-state pulse power drive. Using the results from a vacuum grating spectrometer combined with measurements with a silicon photo diode, it has been found that substantial amounts of radiation within the reflectance band of Mo/Si mirrors can be generated using the 13.5 nm emission line of doubly ionized Lithium. This prototype DPF converts 25J of stored electrical energy per pulse into approximately 0.76J of in- band 13.5nm radiation emitted into 4(pi) steradians. The pulse repetition rate performance of this device has been investigated up to its DC power supply limit of 200Hz. No significant reduction in EUV output was found up to this repetition rate. At 200Hz, the measured pulse-to-pulse energy stability was (sigma) equals 6 percent and no drop out pulses were observed. The electrical circuit and operation of this prototype DPF device is presented along with a description of several future modifications intended to improve stability and efficiency.

Development of an EUV (13.5 nm) light source employing a dense plasma focus in lithium vapor

Initial characterization efforts of Dense Plasma Focus (DPF) technology showed that efficient conversion of electrical energy into in-band emitted radiation could be achieved. Results previously reported showed that 25 J of electrical energy can be converted into 0.38 J of in-band, 13.5 nm radiation emitted into 2 (pi) steradians. This prototype configuration demonstrated a 1.5% conversion efficiency into 2 (pi) steradians, but exhibited several major drawbacks. The two greatest issues were excessively high stored energy per pulse and poor stability of the plasma size and position. Such high input energies would limit the maximum pulse repetition rate and poor plasma stability would lead to excessive electrode erosion and large integrated source size. Recent efforts have concentrated on reducing the required input energy while simultaneously improving stability. The result of these efforts is a DPF system that exhibits table operation with as little as 1.5 J of input energy and has demonstrated pulse repetition rates as high as 2500 Hz. Once a stable, low input energy DPF was achieved, this prototype DPF device was fitted with a simple Lithium vapor delivery system. Pinhole camera images of the Lithium vapor source show that it is stable with a size of less than 350 micrometer FWHM. In this technologys present state, the potential in-band collectable EUV optical power is estimated to be 6.9 W.

Performance characterization for an excimer laser solid-state pulsed power module (SSPPM) after 20B shots

An experiment has been designed to characterize a solid-state pulsed power module (SSPPM) during the initial manufacturing cycle and then repeat the same characterization measurements after the module has gone through several sequences of 10B shots of normal operation in an excimer laser. The goal of such an experiment is to determine what, if any, degradation occurs during these extended periods and to assist in the development of expected module lifetimes that can then be used to estimate the cost of operation of the overall excimer laser. Initial component and subassembly measurements include the capacitance and Q of energy storage capacitors; the inductance and Q of bias, charging, and energy recovery inductors; the B-H characteristics of magnetic cores; insulation breakdown strength; connection resistance; and the general physical appearance of the unit. Operational measurements also compare the efficiency of each pulse compression stage, the repeatability and accuracy of diagnostics, thermal management parameters, and the recovery and on-state characteristics of the silicon-controlled rectifiers (SCRs) and diodes. Each of these items is monitored before testing and after each sequence of 10B shots has been completed. Results of the experiment are described.