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Emission spectrum diagnosis of the reaction process temperature of the plasma cleaning system

Emission spectrum diagnosis of the reaction process temperature of the plasma cleaning system

Emission spectrum diagnosis of the reaction process: There are many chemical reactions in atmospheric plasma of plasma cleaning system. These chemical reactions can be used to synthesize high value-added chemical raw materials, modify the surface of materials and degrade environmental pollutants. Chemical reactions vary, but they are essentially recombinations of atoms or groups of atoms into products. The electrons, ions, excited atoms, molecules and free radicals in plasma are very active reaction species, which can change the chemical reaction path effectively in the process of chemical reaction. Spectroscopic diagnosis can directly obtain the type and intensity of the active species in the plasma and provide experimental basis for revealing the chemical reaction mechanism.   The main product of CH4 in atmospheric pressure DC discharge plasma is C2H2. CH3, CH, H, C2 and C active species can be found in the CH4 plasma from the emission spectrometric diagram of CH in the atmospheric pressure DC discharge plasma. According to the spectral detection results, C-H fracture of CH4 directly occurs in the plasma, and CH active species is the main reaction intermediate species.   Emission spectrum diagnosis of system temperature:   In atmospheric plasma, the electron temperature of plasma is difficult to be measured due to the interference of probe and other diagnostic techniques. However, the temperature of plasma system at atmospheric pressure can be achieved by studying the rotational temperature of gas molecules. It is a convenient and feasible method to collect the plasma gas temperature data by emission spectrum, which will not affect the discharge process and can obtain the discharge temperature accurately. High gas density in the atmospheric pressure plasma, frequent collision of gas molecules and ions, not only makes the ion balance the number of particles on the rotational level, and translational temperature reach equilibrium with the gas molecules and the rotation of the molecules can reach thermal equilibrium and the translational energy of the particles of relaxation time is very short, it is generally believed rotational temperature and gas temperature in the process of discharging is close to equal, therefore plasma cleaning system can be calculated by measuring the high rotation spectrum of rotational temperature, so as to estimate the gas temperature of plasma.   Spcair is a software that calculates the isomeric spectrum based on the particle number distribution on the energy level satisfying boltzmann distribution. Since its characteristic parameters include each characteristic temperature of the plasma, the plasma temperature at atmospheric pressure can be easily obtained by comparing the actual measured spectrum and the calculated spectrum of the plasma.   To determine plasma temperatures, the oscillatory and rotational temperatures of chlorine molecules were determined by spectrometric measurements of the second positive N2(C3π) emission spectra compared with those simulated using Speair. The second positive band N2(C3π) emission spectra of nitrogen molecules and the second positive band emission spectra of ammonia molecules were obtained by dielectric barrier discharge at atmospheric pressure at discharge voltage 25.4kV, discharge frequency 13.8kHz and flow rate of N2 at 100ml/min. It can be seen from the result diagram that the fitting spectrum is very consistent with the experimental spectrum. Specair can directly obtain that the rotation temperature of the gas under the above experimental conditions is 520K, and the plasma temperature is also 520K. When the discharge voltage is 30kV and 33kV respectively at the same discharge frequency, the plasma temperature is 580K and 600K.

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PCB plasma etcher Introduction

PCB plasma etcher Introduction

Traditionally, PCB manufacturers have used corrosive solvents, such as strong acids, to etch and clean holes in printed circuit boards. Many different chemicals are used to clean the holes, but all of these chemicals can cause harm to the environment and can easily harm workers.   Etching with chemical reagents:   The traditional PCB board manufacturing method is chemical etching. Some parts of the copper foil are protected by an etching inhibitor consisting of tin, tin, and lead, while the rest of the copper is etched away. The process USES an ammonia-etched solution to remove the copper, which does not corrode tin or lead, so the copper remains a "conductor" beneath the tin, or a path for electrons to travel along the entire circuit board. The quality of the chemical etching can be defined by the integrity of the copper removal that is not protected by the anticorrosion agent. The quality also refers to the straightness of the trace edge and the degree of etched bottom cutting.   Etching bottom is caused by non-directional etching of chemicals. Once downward etching occurs, lateral etching is allowed. The smaller the bottom cutting is, the better the quality will be. These base cuts are measured and called "etching factors". All the steps of the etching process are linked together, and the quality of the etching can be the result of the etching solution or the anticorrosive agent used. Chemical etching USES many harmful chemicals and is not an environmentally friendly etching process.   Use plasma for etching:   Plasma etching is an environmentally friendly etching method popular in the 1980s to remove gum residue from PCB holes. A plasma formed in a vacuum by ionizing gas particles using a radio frequency of 13.56MHz is the fourth state of matter. Plasma PCB technology can improve the quality of etching and the removal effect of through hole pollutants. As its name suggests, PCB plasma etcher is an etching technique that produces plasma under strict conditions and is used to clean the residue from drilling holes in the PCB.   To fully understand PCB etching technology, it is necessary to master the working principle of plasma etching machine. The plasma etcher is composed of two electrodes to generate RF and a ground electrode. Generally there are four gas inlets, oxygen, CF4 or some other etched gas coming into the system through these gas inlets. Depending on the etching material, the mixture of gases is required to treat the different materials. Radio frequency ionized gas particles are applied during gas entry into the system. 13.56MHz is considered as the standard frequency of plasma formation. Rf excitations excite gaseous electrons and change their state, and the machine generates high-speed plasma pulses to etch the material. In the process of chemical reaction, PCB plasma etching system will produce volatile compounds as by-products, and it usually takes little time for the plasma to clean the hole residue on the circuit board.   Plasma is also commonly used in the lead frame of the cleaning chip package. The lead frame transmits electrical signals to the outside of the package. All organic matter must be removed before it can be added to the package.   According to the type of material to be etched, the nature of the gas used and the required type of etch, there are many types of plasma etch on PCB. The working temperature and pressure also play an important role in plasma etching. Small changes in working temperature and pressure can significantly change the electron collision frequency. RIE(reactive ion etching) USES physical and chemical mechanisms to achieve unidirectional high level surface etching. Because the RIE process combines physical and chemical processes, it is faster than plasma etching alone. High-energy ion collisions strip electrons from the plasma and allow the use of positively charged plasma for surface treatment.

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Conversion of low carbon alkane in plasma at atmospheric pressure

Conversion of low carbon alkane in plasma at atmospheric pressure

Low carbon alkanes (C1~C4) are very rich carbon hydrocarbon resources, widely exist in natural gas, oilfield gas, coalbed methane and catalytic cracking gas. With the depletion of petroleum resources in the world, it is particularly important to prepare high value-added chemical raw materials from natural gas, oilfield gas and coalbed methane. Due to low carbon alkane chemical inertness is stronger, in the early days of the low carbon alkane in olefins reaction adopts highly active oxidant O2 and N2O (such as 1982 Keller precursors of sex work oxidative coupling of methane to olefin response), these highly reactive oxidants in relatively high low carbon alkane conversion rate at the same time, also caused the product further oxidation, so difficult to achieve the desired purpose product selectivity. Since the 1990s, people began to explore plasma activation method and plasma-catalyzed co-activation method to carry out the conversion reaction of low carbon alkanes.   Methane conversion reaction in low-temperature plasma at atmospheric pressure:   Methane (CH4) is the main component of natural gas, accounting for more than 90% of total natural gas. Natural gas reserves are very rich. In 2015, the world's proven natural gas reserves were 1.97x10^21m3, and the recoverable natural gas reserves in China were 4.94x10^18m3. Broken less in recent years, with the oil resource, natural gas, for a total of considerable reserves become the 21st century is one of the promising substitute energy and chemical raw materials but at the moment, the effective utilization of natural gas is still quite low, the main reason is that the main components of the gas methane is very stable organic small molecule structure, four C - H average keys for 414 kj/mol, CH3 - H key in the key for 435 kj/mol, difficult to activate. How to convert methane into liquid fuel easily transported and chemical products with high added value is one of the research hotspots.

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Application of plasma cleaning machine in packaging plasma coating process

Application of plasma cleaning machine in packaging plasma coating process

Silica can be obtained by oxidizing silica vapor in an oxygen plasma. The anodic arc process USES consumable silicon metal placed in a furnace as the anode for the vacuum arc. If a DC voltage of 20~30V is applied between the metal cathode and the furnace, continuous arc discharge will occur between the cathode and anode as long as there is a vapor mass in front of the cathode. This discharge can produce a highly active plasma in a vacuum furnace, at which point the silicon atoms in the highly excited state are vaporized and move towards the packaging substrate, which rotates continuously on the upper part of the vapor cloud. At this point, if oxygen is added to the steam, a layer of silica will be deposited on the surface of the encapsulated substrate.   The polymerization process is the process of forming organic or inorganic polymer coating on the substrate. The process belongs to the category of plasma enhanced chemical vapor deposition. In the PECVD process, the vapor containing the required components is introduced into the plasma. The electrons in the plasma ionize the molecules or decompose them into free radicals. The generated active molecules can undergo chemical reactions on the surface or in the gas phase environment and form thin films through deposition. The nucleation process depends on the appearance of the material surface and whether there are foreign atoms on the surface. The dense film produced by the above process is hydrophobic and has no pores. However, in order to produce high quality films in a short time, process parameters must be optimized, especially in the application of barrier layers. Organosilicon films can be obtained by cracking organosilicon resins in a plasma environment. If the silicon atoms react with oxygen, nitrogen or their mixture of gases, silica, silicon oxide or silicon nitride films can be deposited. Organic gases such as acetylene are used as the precursor reactants of diamond-like carbon films.   Compared with the traditional chemical vapor deposition (CVD) process, the plasma pulsed CVD process is an improved one. Pulsed plasma can be generated by applying a pulsed signal to a power source (usually a radio frequency or microwave power source). Pulsed plasma allows ions to have lower energy in the packaging coating process. The coating is gradually thickened through a series of small-scale treatments to form a highly dense and uniform coating. In addition, the chemical composition of the reaction mixture can be changed between the two pulses. Therefore, multiple layers of different properties can be coated in the same process operation, resulting in customized multi-layer coating systems. Using plasma chemical vapor deposition of silicon dioxide and titanium dioxide prepared by coating technology has been widely used in all kinds of plastic surface modification, terephthalic acid glycol polyester (PET) and poly (methyl methacrylate (PMMA), polycarbonate (PC), copolymerization cyclic olefin (COC), polypropylene (PP) and high-density polyethylene (HDPE)) of the surface modification.

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Conversion reaction of pure methane under plasma action

Conversion reaction of pure methane under plasma action

As early as the 1930s, Huels, a German company, began to study the pyrolysis of methane thermal plasma to produce acetylene. Methane is discharged in an electric field and transformed into black carbon, acetylene (C2H2), and hydrogen (H2). The key to this process is to make acetylene form and cool to the stable temperature of acetylene in a very short time. Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences has also carried out an amplification test of acetylene produced by natural gas plasma pyrolysis, with a production capacity of over 100T /a. Bao Weiren et al. used arc plasma to pyrolysis methane to produce acetylene, and obtained a small energy consumption of 9.68kW ·h/kg. The use of plasma low pressure cold plasmas for methane dehydrogenation to C2 hydrocarbon began in the early 1990s. Suib and Zerger applied microwave plasma technology to methane coupling reactions.   Methane can be converted to ethane (C2H6), ethylene (C2H4) and acetylene (C2H2) at system pressure of 4x102-6.7 x104Pa, plasma injection power of 40~ 80W, and gas flow rate of 50~500 mL /min. The conversion rate of methane was between 4% and 55%. The selectivity of ethane, ethylene and acetylene was 54%~ 75%, 13%~25% and 0~25%, respectively. Wang Baowei et al. from Tianjin University used asymmetric plasma technology to study the direct conversion of methane into C2 hydrocarbon (the mixture of C2H6, C2H4 and C2H2), and systematically investigated the influence of electrode structure, discharge voltage and reaction gas velocity on the reaction.   The atmospheric pressure DC pulse power supply USES the energy storage capacitor to discharge to the load through the rotating spark gap to generate the pulse high voltage, which has the characteristics of steep rising edge and narrow pulse width, so that the energy can be effectively injected into the reactor, and the energy consumption of the power supply is small. In the study of methane conversion reaction using pulsed corona discharge plasma, the main factors influencing methane conversion rate (Xcu4), C2 hydrocarbon selectivity (Sc2) and yield (Yc1) are plasma pulse peak voltage, electrode spacing and methane gas velocity.

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Use of semiconductor plasma cleaning equipment in semiconductor wafer industry

Use of semiconductor plasma cleaning equipment in semiconductor wafer industry

In the semiconductor industry chain, plasma cleaning equipment is an important link, it applies to raw materials and semi-finished products on every step possible impurity cleaning, in order to avoid impurity affecting the product quality and the performance of the downstream products, plasma cleaning equipment for monocrystalline silicon production, lithography, etching, deposition and other key process and packaging process of using are indispensable.   There are two cleaning technologies commonly used: wet cleaning and dry cleaning. At present, wet cleaning is still the mainstream in the industry, accounting for more than 90% of the cleaning steps. Wet production is to spray, scrub, etch and dissolve silicon wafers with chemical solvents to make the impurities on the surface react with the solvent to produce soluble substances and gases or fall off directly. Then, ultra-pure water is used to clean the surface of silicon wafers to make them dry and meet the requirements of cleanliness. In order to improve the cleaning effect of silicon chip, ultrasonic, heating, vacuum and other auxiliary technologies can be used. Wet cleaning includes pure solution dipping, mechanical wiping, ultrasonic/Meg cleaning, rotating spray, etc. Relatively speaking, dry cleaning refers to the cleaning technology that does not depend on chemical agents, including plasma cleaning, gas phase cleaning, beam cleaning, etc.   Due to the different technology and application conditions, there are obvious differences in the semiconductor cleaning equipment in the market. At present, the main cleaning equipment in the market is single wafer cleaning equipment, automatic cleaning table and washing machine equipment. From the 21st century to now, to single wafer cleaning equipment, automatic cleaning table, washing machine as the main cleaning equipment.   Semiconductor single wafer cleaning equipment is a kind of equipment that USES rotary spray to clean single wafer by chemical spray. Compared with automatic cleaning equipment, the cleaning efficiency is lower, but it has extremely high treatment environment control ability and particle removal ability. Automatic cleaning table, also known as slot automatic cleaning equipment, refers to the equipment cleaning multiple wafers at one time. Its advantage is strong cleaning ability, suitable for mass production, but can not reach the cleaning precision of single piece of cleaning equipment, it is difficult to meet the current technical advanced requirements of the whole process parameters. And because many pieces are cleaned at the same time, the automatic cleaning table cannot avoid the disadvantage of cross contamination. The washer adopts rotary spray, with mechanical wiping, high pressure, soft spray and other adjustable modes, suitable for deionized water cleaning process, including saw wafer, wafer wafer thinning, polishing, CVD, etc., especially plays an important role in the cleaning after wafer polishing.   There is no significant difference between the single wafer cleaning equipment and the automatic cleaning platform device in the use process. The main difference lies in the cleaning method and precision requirements, and the key dividing point lies in the semiconductor 45 nanometer process. In short, the automatic cleaning platform is multi-chip simultaneous cleaning, which has the advantage of mature equipment and high productivity, while the single-chip cleaning equipment is piece-by-piece cleaning, which has the advantage of high cleaning accuracy, can effectively clean the back side, slope and edge, while avoiding cross contamination between wafers. Before 45nm, the automatic cleaning table can meet the cleaning requirements. When it is below 45nm, the cleaning precision is achieved by relying on the single wafer cleaning equipment. With the number of post-semiconductor process nodes decreasing, single wafer cleaning equipment has become the main cleaning equipment under the predictable technology.   Process points reduce extrusion yield and increase the demand for cleaning equipment. Due to the reduction of process nodes, economic benefits require semiconductor enterprises to make continuous breakthroughs in cleaning technology and improve the requirements of cleaning equipment process parameters. Effective non-destructive cleaning will be a major challenge for manufacturers, especially for 10nm chips, 7nm chips and even smaller chips. To popularize Moore's Law, chip makers must be able to eliminate not only small, random defects on flat wafer surfaces, but also to adapt to more complex, fine-grained 3D chip structures that do not cause damage or material loss.

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