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High Power Impulse Magnetron Sputtering (HIPIMS or HiPIMS, also known as high-power pulsed magnetron sputtering, HPPMS) is a method for physical vapor deposition of thin films which is based on magnetron sputter deposition. HIPIMS utilises extremely high power densities of the order of kW⋅cm−2 in short pulses (impulses) of tens of microseconds at low duty cycle (on/off time ratio) of < 10%. Distinguishing features of HIPIMS are a high degree of ionisation of the sputtered metal and a high rate of molecular gas dissociation which result in high density of deposited films. The ionization and dissociation degree increase according to the peak cathode power. The limit is determined by the transition of the discharge from glow to arc phase. The peak power and the duty cycle are selected so as to maintain an average cathode power similar to conventional sputtering (1–10 W⋅cm−2). HIPIMS is used for: *adhesion enhancing pretreatment of the substrate prior to coating deposition (substrate etching) *deposition of thin films with high microstructure density == HIPIMS plasma discharge == HIPIMS plasma is generated by a glow discharge where the discharge current density can reach several A⋅cm−2, whilst the discharge voltage is maintained at several hundred volts.〔. 〕 The discharge is homogeneously distributed across the surface of the cathode (target) however above a certain threshold of current density it becomes concentrated in narrow ionization zones that move along a path known as the target erosion "racetrack". HIPIMS generates a high density plasma of the order of 1013 ions⋅cm−3〔 containing high fractions of target metal ions. The main ionisation mechanism is electron impact, which is balanced by charge exchange, diffusion, and plasma ejection in flares. The ionisation rates depend on the plasma density. The ionisation degree of the metal vapour is a strong function of the peak current density of the discharge. At high current densities, sputtered ions with charge 2+ and higher – up to 5+ for V – can be generated. The appearance of target ions with charge states higher than 1+ is responsible for a potential secondary electron emission process that has a higher emission coefficient than the kinetic secondary emission found in conventional glow discharges. The establishment of a potential secondary electron emission may enhance the current of the discharge. HIPIMS is typically operated in short pulse (impulse) mode with a low duty cycle in order to avoid overheating of the target and other system components. In every pulse the discharge goes through several stages:〔 *electrical breakdown *gas plasma *metal plasma *steady state, which may be reached if the metal plasma is dense enough to effectively dominate over the gas plasma. The negative voltage (bias voltage) applied to the substrate influences the energy and direction of motion of the positively charged particles that hit the substrate. The on-off cycle has a period on the order of milliseconds. Because the duty cycle is small (< 10%), only low average cathode power is the result (1–10 kW). The target can cool down during the “off time”, thereby maintaining process stability.〔Werner Kölker: ''Higher flexibility in coating design (PDF ).'' In: ''CemeCon Facts.'' Nr. 36, S. 14–15.〕 The discharge that maintains HIPIMS is a high-current glow discharge, which is ''transient'' or ''quasistationary''. Each pulse remains a glow up to a critical duration after which it transits to an arc discharge. If pulse length is kept below the critical, the discharge operates in a stable fashion indefinitely. Initial observations by fast camera imaging〔 in 2008 were recorded independently, demonstrated with better precision, and confirmed demonstrating that most ionization processes occur in spatially very limited ionization zones. The drift velocity was measured to be of the order of 104 m/s,〔 which is about only 10% of the electron drift velocity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「High-power impulse magnetron sputtering」の詳細全文を読む スポンサード リンク
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