Paul C. Melcher

Evaluation of nanocrystalline materials, amorphous metal alloys, and ferrites for magnetic pulse compression applications

A magnetic pulse compressor test stand was developed to evaluate the switching and loss properties of magnetic core materials that included ferrite and several alloys of nickel-iron, Metglas, and the nanocrystalline material Vitroperm. The test stand generated 1−cos(ωt) voltage pulses across the core under evaluation to simulate the magnetic excitation encountered in pulse compressors. Pulse amplitude and repetition rate were user controlled in order to vary the initial time to saturation while keeping magnetic core temperature constant. Switching losses were calculated directly as ∫(νi)dt, and an advanced figure of merit was utilized to compare test results. The test stand, data acquisition and analysis, and test results are discussed.

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.

IGBT and diode loss measurements in pulsed power operating conditions

High voltage IGBTs and series diodes are used in Cymers solid-state pulsed power commutator module. The IGBTs and series diode losses in the module affect the cooling system design and the energy transfer efficiency. It is difficult to estimate the IGBT and diode losses in the pulsed power operating condition. We have previously tried to measure the IGBT losses by measuring the voltage across the IGBT (using a high voltage differential probe) and the current through the IGBT. Since the voltage across the IGBT changes from the kilo-volt level to several volts, it is very difficult to measure the small on-state voltage accurately. Also very small internal package inductance can obscure the voltage measurement due to the high dl/dt level in the circuit. In this work, the IGBT and series diode losses were measured with a commutator module directly by measuring the water flow rate going through a cold-plate attached to the IGBT or diode and the temperature difference of the inlet and outlet water. Heat transfer through other means, such as free convection, was minimized by sealing the IGBT/diode inside a thermal isolation blanket and polyurethane foam. The loss measurement results on the dual package IGBT and dual package diode are presented in the paper

Low jitter and drift high voltage IGBT gate driver

The Cymer Master Oscillator Power Amplifier (MOPA)-based light source requires tight timing control over all operating repetition rates. The newly developed IGBT gate driver allows tight control of the IGBTs turn on/off timing jitter and drift. Its performance is significantly improved compared to the previous IGBT gate driver. Switching rate improvement of the new driver reduces the time spent in the IGBTs active switching region and therefore helps reduce losses. These improvements allow for better control of IGBT triggering and laser performance. This paper will provide the IGBT gate driver general development approaches, performance and high voltage IGBT switching test results. The new IGBT gate driver meets the requirements for Cymers MOPA-based laser systems.

Evaluation of Nanocrystalline Materials, Amorphous Alloys and Ferrites for Repetitive-Magnetic Pulse Compression Applications

Recent advances in nanocrystalline magnetic materials and core insulation techniques are believed to be superior to the current magnetic cores that are employed as saturable switches in solid-state, repetitive magnetic pulse compressors. Accordingly, a magnetic pulse compressor test stand has been constructed at the University of Missouri-Columbia (UMC) to evaluate the switching properties of candidate magnetic materials and insulation schemes that cover the wide parameter space requisite to magnetic modulators. Experimental measurements were utilized to analyze and compare a wide variety of magnetic materials consisting of nanocrystalline cores, amorphous metal alloys and ferrites. The dependence of the insulating material and the core construction techniques, e.g., type and thickness of the insulation and ferromagnetic material were included in a model along with the magnetic core loss measurements. An advanced figure of merit was utilized to down-select the cores for a particular application based on the measurements and the UMC database. Final test results were analyzed to determine which core material had the best switching properties for a specific operational regime. The test stand, data acquisition equipment and methods, data processing, magnetic core materials under examination and final test results are discussed.

A decade of solid state pulsed power development at Cymer Inc.

This paper will summarize over 10 years of solid state pulsed power development at Cymer Inc. associated with power systems for excimer and other light sources used in the application of semiconductor photolithography. Over eight different generations of power systems have been designed and implemented as the light source systems themselves have evolved over time. Each of these power systems includes a charging system and a solid-state switched magnetic pulse compressor. Specific technical challenges and accomplishments will be described for each iteration. In addition, application specific requirements will also be discussed including high volume manufacturing, high reliability, long lifetime, large operating range, compact size and weight, ease of troubleshooting, high efficiency and effective thermal management, low cost, safety, and third party approvals (UL and TUV)

Loss Estimation of Capacitor in High Rep-Rate Pulsed Power System

Capacitor loss in pulsed power systems has become an important issue for thermal management, especially when the operating rep-rate and energy per pulse are getting higher and higher. It is practical to analyze the loss of a capacitor using a capacitor series equivalent circuit model in this pulsed power application. The capacitor loss is directly related to the equivalent series resistance (ESR) of the capacitor. In the paper, the formula to estimate the capacitor loss is presented. It is proportional to the energy per pulse, rep-rate, and capacitor dissipation factor (tandelta) at the certain energy transfer frequency of the circuit. The charging and discharging frequencies of the capacitor might be different. Both of them will produce losses, and contribute to the total capacitor loss. The analysis of a capacitor bank with capacitors in parallel or in series is presented as well. Also in this work, the parameters of different types of capacitors were measured, including film capacitors and high voltage ceramic capacitors, using a Agilent 4285 A Precision LCR Meter up to 13 MHz. The influence of temperature on capacitance and dissipation factor was investigated by sinking the capacitor in oil under controlled temperatures. The results are very helpful to estimate the losses of capacitors in Cymers laser pulsed power systems, and to provide design guidelines to the next generation of 6 kHz laser power systems.

Timing and synchronization of solid state pulsed power modules (SSPPM) for excimer laser applications

In certain applications for excimer lasers, it is critical to maintain the timing of a solid state pulsed power module (SSPPM) such that the pulsed output of the laser can be synchronized to another external event. In some cases, this synchronization must be held to times in the order of 10 ns or less. Since the operating voltage range of these magnetic modulators must vary (by up to a factor of two) in order to adjust the laser output energy, the throughput delay can also vary significantly. This timing must also be maintained over other possible laser operating conditions and scenarios, including various repetition rates, duty cycles, etc. External factors, such as cooling water temperature and flow rate, air temperature, etc. can also impact the system timing. Data are presented detailing the contribution of each potential item in the timing sequence of these modulators as they impact the overall system timing jitter and drift. Design details are also discussed as to how these issues are mitigated and minimized so as to reduce their effect and meet the overall system timing requirements.

Lifetime and reliability data of commercial excimer laser power systems modules

Since 1996, CYMER has manufactured over 1500 excimer lasers for the application of integrated circuit photolithography. Because reliability and cost of operation (CoO) are critical in the semiconductor industry, it is extremely important to quantify these parameters for the laser and each of the primary modules. Lifetime and reliability data for the initial generation of solid state pulsed power module (SSPPM) units are presented from a number of sources, including more than 750 laser systems in the field in addition to a number of in-house module verification systems. Highly accelerated life test (HALT) experiments have also been implemented at CYMER to help quantify the design margins of these modules with respect to operating parameters such as temperature and voltage. In addition, results are updated from an experiment involving testing of a SSPPM to over 50B shots where the unit was characterized at several intervals in an attempt to detect any potential signs of degradation which might limit the operational lifetime or cause the unit to fail. To date, no such indications of degradation have been measured. The paper compares actual reliability and lifetime data from these various sources compared to the original lifetime estimates.

Performance of very high repetition rate ArF lasers

We report the performance of a very high repetition rate ArF laser optimized for next generation, high NA, high throughput scanner. The lasers repetition rate exceeds 4kHz, at 5mJ, and at bandwidths of less than 1.2 pm. We discuss the complexity of high power operation, and make some estimates about the robustness of this technology. In particular, we discuss the risks of scaling to this high repetition rate, and prospects of exceeding 4kHz to near 6kHz with 95 percent bandwidths of less than 1pm.