Output Current Control System of a High Voltage Electric Pulse Generator for Plasma Excitation

A control and pulse discharge current limiting system integrated into an AC/DC converter and pulse modulator of a high voltage pulse generator have been developed. The peculiarity of such system\textquotesingle s operation is the stabilization of the power supplied to the discharge and the correction of the width of output electric pulses towards decrease upon reaching the specified pulsed current amplitude value. The system enables the pulse generator to work in the modes close to the ``short circuited load'' mode. In this case the driving module of a composite IGBT key performs the correction of the working pulse width and blocks the pulse generator operation if needed. The suggested circuit design solutions allow using the generator in a wide range of electric plasma-forming parameters' modes and working with various types of vacuum gas discharge systems

Study of the Effect of Low-Temperature Plasma Exposure on Mould Fungi Colonizing Paper

The influence of radiofrequency cold plasma in ambient air at 200 Pa pressure on mould fungi of the genus Aspergillus was studied. It was shown that 20 min plasma treatment of paper with mould and contamination reduced the number of colony forming units but didn't lead to complete suppression of fungal viability. Strains of A. versicolor after plasma treatment lost the ability to excrete pink pigment to the environment. A. niger strains were more resistant and kept acidification ability. One of the possible plasma inactivation factors was formation of reactive hydroxyl (OH) radical

АНАЛИЗ УСЛОВИЙ ВОЗБУЖДЕНИЯ СВЧ-РАЗРЯДА НИЗКОГО ВАКУУМА В ПЛАЗМОТРОНЕ РЕЗОНАТОРНОГО ТИПА

The efficiency of a cavity microwave resonator using for getting large volume (more than 4000 cm3) low vacuum plasma for group treatment of products in the microelectronics technology has been evaluated. The results showed that the value of electric field breakdown intensity about E0 ≈ 110 V/cm in a resonator system for low vacuum can be already achieved at a microwave power higher than 50 W. As far as the conditions of exciting and maintaining the microwave plasma for technological application are concerned, the conditions of preserving resonating properties at exciting plasma with a volume of 9000 cm3 in resonator and in case of placing a various number of silicon wafers in the microwave discharge have been analyzed. The results of the calculations show that at the presence of plasma the quality factor of the cavity resonator change caused by its partial loading with semiconductor wafers leads to the decrease of resonator’s total quality factor by 2,5 times. In order to excite microwave discharge at total quality factor of loaded resonator Q ≈ 200, the value E0 ≈ 110 V/cm can be provided with using microwave magnetron of medium power level ( Pgen ≈ 650 W).Проведена оценка эффективности использования объемных СВЧ-резонаторов для создания плазмы большого объема (более 4000 см3) низкого вакуума для целей групповой обработки изделий в технологии микроэлектроники. Результаты показали, что в резонаторной системе величина пробивной напряженности электрического поля порядка E0 ≈ 110 QUOTE В/см для низкого вакуума может достигаться уже при СВЧ-мощностях свыше 50 Вт. Применительно к условиям возбуждения и поддержания СВЧ-плазмы технологического назначения проведен анализ условий сохранения резонатором резонирующих свойств при возбуждении в нем плазмы объемом около 9000 см3 и помещении в СВЧ-разряд разного количества кремниевых пластин. Результаты расчетов показывают, что изменение добротности объемного резонатора, обусловленной частичным заполнением его полупроводниковыми пластинами, приводит к уменьшению общей добротности нагруженного резонатора до 2,5 раз. При этом, к примеру, для возбуждения СВЧ-разряда при общей добротности нагруженного резонатора Q ≈ 200 величина QUOTE E0 ≈ 110 В/см обеспечивается использованием СВЧ-магнетрона среднего уровня мощности ( Pвозд ≈ 650 Вт)

Исследование влияния условий подачи озоно-воздушной смеси на процесс удаления фоторезиста с поверхности кремниевой пластины

The study is devoted to the research of the dependence of the processing results of photoresistive films on the silicon wafers surface in an ozone environment on the conditions and parameters of the process. The high oxidizing potential of ozone justifies the possibility of its use for removing organic films under atmospheric pressure. The experiments were carried out using the developed research bench, in which the mode and method of heating, as well as the method of supplying gas to the surface of the photoresist, were varied. Silicon wafers with a formed 1,35-μm thick masking photoresist film were used as experimental samples. It was found expedient that uniform heating of the plate over its entire surface can be achieved using a ceramic IR heater. When the ozone-air mixture was introduced into the center of the heated sample, the presence of the removed photoresist residues was observed, which was associated with a temperature drop in its surface area. To solve this problem, the computer models of the temperature regimes of the reaction volume elements were calculated. They showed that the scattering of the working gas flow over the surface of the silicon wafer would significantly increase the efficiency of photoresist removal, and with a good selection of the treatment regime it would ensure complete removal of the photoresist. The data obtained were experimentally confirmed by using an ozone-air mixture flow separator. Experiments were carried out to study the effect of the distance from the wafer surface to the working gas inlet on the photoresist removal rate. They showed that a decrease in the distance reduces the ozone loss due to thermal decomposition and, consequently, increases the material removal rate.Работа посвящена изучению зависимости результатов обработки фоторезистивных пленок на поверхности кремниевых пластин в среде озона от условий и параметров проведения процесса. Высокий окислительный потенциал озона обосновывает возможность его применения для удаления органических пленок в условиях атмосферного давления. Эксперименты выполнялись с использованием разработанного исследовательского стенда, в котором варьировался режим и способ нагрева пластины, а также способ подачи газа к поверхности фоторезиста. В качестве экспериментальных образцов выступали кремниевые пластины со сформированным слоем фоторезистивной маскирующей пленки толщиной 1,35 мкм. Было установлено, что для обеспечения равномерности нагрева пластины по всей ее поверхности целесообразным является использование керамического инфракрасного нагревателя. При подаче озоно-воздушной смеси в центр нагретого образца наблюдалось наличие остатков удаляемого фоторезиста, связанное с перепадом температуры в его приповерхностной области. Для решения данной проблемы были рассчитаны компьютерные модели температурных режимов элементов реакционного объема, которые показали, что рассеяние потока рабочего газа по поверхности кремниевой пластины позволяет значительно увеличить эффективность удаления фоторезиста, а при качественном подборе режима обработки обеспечивает полное снятие фоторезистивного материала. Полученные данные были экспериментально подтверждены путем использования сепаратора потока озоно-воздушной смеси. Проведены эксперименты по исследованию влияния расстояния от поверхности пластины до места ввода рабочего газа на скорость удаления фоторезиста, показавшие, что уменьшение расстояния способствует сокращению потерь озона в результате термического разложения и, соответственно, повышению скорости удаления материала

Исследовательский стенд для микроплазменной поверхностной обработки материалов в условиях атмосферного давления

A research stand for microplasma treatment of object surfaces with the ability to move the discharge zone along the object using a program-controlled linear stepper motor has been developed. The design of the stand allows the use of different types of plasma generation systems, as well as processing with feeding of various gases such as air, nitrogen, oxygen, etc. into the discharge zone. The research bench is equipped with measuring equipment for monitoring the electrical and physical characteristics of the discharge (digital oscilloscopes, optical emission spectrometer, air ion meter, etc.). A microhardness tester, goniometer, interference microscope, tribometer, tensile testing machine, etc. can be used to further evaluate the quality and characteristics of the treated surfaces. Examples of the electrical characteristics of discharge devices tested as part of the research stand, optical emission spectroscopy of plasma, and results of measurements of the contact angle of treated objects surfaces are given.Разработан исследовательский стенд для микроплазменной обработки поверхностей объектов с возможностью перемещения зоны разряда вдоль объекта с использованием программно управляемого линейного шагового двигателя. Конструкция стенда позволяет применять разные типы систем плазмообразования, а также проводить обработку с подачей в зону разряда различных газов, таких как воздух, азот, кислород и т. д. Исследовательский стенд оснащен измерительным оборудованием для контроля электрических и физических характеристик разряда (цифровые осциллографы, оптический эмиссионный спектрометр, аэроионометр и др.). Для последующей оценки качества и характеристик обработанных поверхностей могут использоваться микротвердомер, гониометр, интерференционный микроскоп, трибометр, разрывная машина и т. д. Приведены примеры электрических характеристик разрядных устройств, апробированных в составе исследовательского стенда, оптической эмиссионной спектроскопии плазмы, результатов измерений краевого угла смачивания поверхностей обработанных объектов

ВОЗДЕЙСТВИЕ НИЗКОТЕМПЕРАТУРНОЙ ГАЗОРАЗРЯДНОЙ ПЛАЗМЫ НА ГРИБЫ РОДА ASPERGILLUS, КОЛОНИЗИРУЮЩИЕ БУМАГУ

It was found that the exposure to low-temperature gas discharge plasma at atmospheric pressure is an effective way of paper cleaning from fungal spores. This effect is explained by the specific mechanisms of micro-discharges excitation and maintaining that ensure efficient (up to 90 %) reduction in the number of viable mould spores without local heating biopolymeric materials.Изучено влияние низкотемпературной плазмы ВЧ, СВЧ и барьерного разрядов на жизнеспособность грибов-колонизаторов бумаги рода Aspergillus. Выявлена высокая эффективность плазмы барьерного разряда по сравнению с другими типами разрядов для деконтаминации материалов на биополимерной основе

Theoretical analysis of low vacuum microwave discharge exciting and maintaining conditions in resonator type plasmatron

The efficiency of a cavity microwave resonator using for getting large volume (more than 4000 cm3) low vacuum plasma for group treatment of products in the microelectronics technology has been evaluated. The results showed that the value of electric field breakdown intensity about E0 ≈ 200 V/cm in a resonator system for low vacuum can be already achieved at a microwave power higher than 50 W. The conditions of preserving resonating properties at exciting plasma with a volume of 9000 cm3 in resonator and in case of placing a various number of silicon wafers in the microwave discharge have been analyzed

ANALYSIS OF LOW VACUUM MICROWAVE DISCHARGE EXCITING CONDITIONS IN RESONATOR TYPE PLASMATRON

The efficiency of a cavity microwave resonator using for getting large volume (more than 4000 cm3) low vacuum plasma for group treatment of products in the microelectronics technology has been evaluated. The results showed that the value of electric field breakdown intensity about E0 ≈ 110 V/cm in a resonator system for low vacuum can be already achieved at a microwave power higher than 50 W. As far as the conditions of exciting and maintaining the microwave plasma for technological application are concerned, the conditions of preserving resonating properties at exciting plasma with a volume of 9000 cm3 in resonator and in case of placing a various number of silicon wafers in the microwave discharge have been analyzed. The results of the calculations show that at the presence of plasma the quality factor of the cavity resonator change caused by its partial loading with semiconductor wafers leads to the decrease of resonator’s total quality factor by 2,5 times. In order to excite microwave discharge at total quality factor of loaded resonator Q ≈ 200, the value E0 ≈ 110 V/cm can be provided with using microwave magnetron of medium power level ( Pgen ≈ 650 W)

The DEVICE for DYNAMIC matching OF gas GLOW DISCHARGE PLASMA system AND output tract of Electric Pulse Generator

To reduce the reactivity of a glow pulse discharge, the device for stepwise matching of the communication channel of the power stage of electric pulses generator for exciting plasma and the plasma discharge as a dynamic load was developed and tested. The peculiarity of this device is the usage of a wide range software-controlled inductive element. The using of mixed analog and digital units circuitry provides stable regulation of inductance from 600 μH to 20 mH. Experimental testing of the device with the E-type and hollow cathode discharge systems at frequencies from 20 kHz to 60 kHz showed a decrease of the phase shift between the current and the discharge voltage pulses and the reduction of the spurious emissions on power pulses trajectories. It makes possible to increase the energy efficiency of plasma process and reliability of the operation of pulse generator with plasma as a load during plasma assisted process of sterilizing medical tools

Study of the influence of ozone-air mixture supply conditions on the process of the photoresist removal from the silicon wafer surface

The study is devoted to the research of the dependence of the processing results of photoresistive films on the silicon wafers surface in an ozone environment on the conditions and parameters of the process. The high oxidizing potential of ozone justifies the possibility of its use for removing organic films under atmospheric pressure. The experiments were carried out using the developed research bench, in which the mode and method of heating, as well as the method of supplying gas to the surface of the photoresist, were varied. Silicon wafers with a formed 1,35-μm thick masking photoresist film were used as experimental samples. It was found expedient that uniform heating of the plate over its entire surface can be achieved using a ceramic IR heater. When the ozone-air mixture was introduced into the center of the heated sample, the presence of the removed photoresist residues was observed, which was associated with a temperature drop in its surface area. To solve this problem, the computer models of the temperature regimes of the reaction volume elements were calculated. They showed that the scattering of the working gas flow over the surface of the silicon wafer would significantly increase the efficiency of photoresist removal, and with a good selection of the treatment regime it would ensure complete removal of the photoresist. The data obtained were experimentally confirmed by using an ozone-air mixture flow separator. Experiments were carried out to study the effect of the distance from the wafer surface to the working gas inlet on the photoresist removal rate. They showed that a decrease in the distance reduces the ozone loss due to thermal decomposition and, consequently, increases the material removal rate