A New Plasma Source for Large-Area Deposition of µc-Si

황두섭,Sang Jin Kim,Gil Jun Kim,Seung Yoon Lee,이헌민 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

This work describes the influences of the electrode-substrate distance and the inter-rod distance of the electrode on the film qualities in very-high-frequency plasma-enhanced deposition using a novel plasma source for silicon thin-film solar-cell applications. As the electrode-substrate distance decreased or the inter-rod distance of the electrode decreased, the crystallinity of the silicon film was improved. The crystalline volume fraction of the silicon film deposited under optimized conditions was 48 %. Also, the thickness distribution of the silicon films changed as a function of the electrodesubstrate distance. The effective area for silicon deposition was 1 m × 1 m, and the plasma excitation frequency was 80 MHz. The crystallinities of the silicon films were evaluated by using X-Ray diffraction and Raman spectroscopy. This work describes the influences of the electrode-substrate distance and the inter-rod distance of the electrode on the film qualities in very-high-frequency plasma-enhanced deposition using a novel plasma source for silicon thin-film solar-cell applications. As the electrode-substrate distance decreased or the inter-rod distance of the electrode decreased, the crystallinity of the silicon film was improved. The crystalline volume fraction of the silicon film deposited under optimized conditions was 48 %. Also, the thickness distribution of the silicon films changed as a function of the electrodesubstrate distance. The effective area for silicon deposition was 1 m × 1 m, and the plasma excitation frequency was 80 MHz. The crystallinities of the silicon films were evaluated by using X-Ray diffraction and Raman spectroscopy.

The Influences of Deposition Parameters on the Microcrystalline Silicon Single Junction Cell Efficiency in Large-area and High Rate Deposition

황두섭,이정훈,이준오,전창엽,임유봉,장철종,장우석 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

For the mass production of silicon thin film solar cell, it is a key issue to increase deposition rate of microcrystalline silicon film on a large area substrate. One of the most effective methods to increase deposition rate of the film is using high frequency and high power plasma. However, high frequency plasma leads to plasma non uniformity in large area deposition, and high power plasma induces substrate heating during deposition of microcrystalline silicon film and degrades the film quality. In this study, we developed a shaped electrode for spatially uniform plasma and a susceptor cooling system for preventing substrate heating by plasma. And also we investigated the influences of deposition parameters on the microcrystalline silicon single junction cell efficiency with high frequency and high power plasma. Glass substrate was 1.1 m × 1.3 m and plasma excitation frequency was 40 MHz. Capacitively coupled parallel plates RF reactor with concave shaped electrode was used. For the high deposition rate of the microcrystalline films, plasma powers of 0.8~1.1W/cm2 were used. The highest deposition rate of microcrystalline silicon was 2nm/s. The increases of temperature of susceptor were monitored by two thermocouples which were installed at center and outer side of the susceptor. The temperature increases were suppressed to almost zero with liquid cooling systems. Multiple step deposition was performed which means the higher H2/SiH2 ratio at the initial stage of film growth was used and the ratio gradually decreased during deposition in order to eliminate the amorphous layer at the interface between substrate and film. We also achieved microcrystalline single junction cell efficiencies above 6% on large area substrate at high deposition rate of 1.5nm/s.

Design of Cooling System for Large-Area and High-Rate Deposition of Hydrogenated Microcrystalline Silicon

임유봉,황두섭,이준오,이정훈,김훈희,장우석 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

We have developed a high frequency (40 MHz) plasma-enhanced chemical vapor deposition (PECVD) system for large-area and high-rate deposition of hydrogenated microcrystalline silicon (μc-Si:H). The large-area and high-rate deposition is known to be the key for mass production of silicon thin film solar cells, and the high-power operation made it possible to obtain deposition rates up to 1.8 nm/s. However, it was reported that there were several drawbacks, and temperature was typically concerned by many researchers. The temperature is one of the most important factors in μc-Si:H deposition processes using PECVD for the reason that temperature is in charge of the surface reaction and the growth kinetics. Without cooling, the temperature was observed to increase considerably during deposition of a thick intrinsic layer with thickness of 2 μm. In order to operate PECVD processes with constant temperature, it is required to design an efficient temperature control system. We have developed a cooling system which is designed for a susceptor and a showerhead. Susceptor cooling is performed in a direct cooling mode where a coolant is circulated through a tube inside a susceptor, and appropriate flow rates and temperatures of the coolant were calculated. Showerhead cooling system is designed to make use of an indirect cooling mode where there is efficient thermal radiation heat exchange between a showerhead and chamber wall. The efficiency was substantially improved by anodizing surface of a showerhead. This cooling system allows stable processes of large-area μc-Si:H deposition at high power.

$YBa_2Cu_3O_{7-x}$ 결정입계 접합을 이용한 마이크로파 감지소자

신중식,조창현,황두섭,김영근,위당문,천성순,신우석,배성준,홍승범,Sin, Jung-Sik,Jo, Chang-Hyeon,Hwang, Du-Seop,Kim, Yeong-Geun,Wi, Dang-Mun,Cheon, Seong-Sun,Sin, U-Seok,Bae, Seong-Jun,Hong, Seung-Beom 한국재료학회 1994 한국재료학회지 Vol.4 No.6

$YBa_{2}Cu_{3}O_{7-x}$결정입계 접합을 이용한 마이크로파 감지소자 $YBa_{2}Cu_{3}O_{7-x}$초전도체 박막을 화학증착법을 이용하여 $LaAIO_{3}$단결정 위에 증착하여 임계온도 90K이상 임계전류밀도 $10^5/A \textrm{cm}^2$(77K) 이상의 우수한 박막을 제작하였다. 이를 포토작업과 이온밀링을 실시하여 수 마이크로미터 크기의 브릿지 형태로 만든 후 이들의 전류전압 특성을 조사하였다. 브릿지에 입사된 마이크로파의 크기에 따라 브릿지 간의 임계전류값의 저하가 관찰되었으며 동시에 샤피로스텝을 관찰할 수 있었다. Microwave Detector Using $YBa_{2}Cu_{3}O_{7-x}$, Grain Boundary Junction $YBa_{2}Cu_{3}O_{7-x}$ superconductor thin films were deposited on $LaAIO_{3}$ (100) single crystal substrates using a metal organic chemical vapor deposition (MOCVD) method. These films showed the critical temperature of about 9OK and critical current density of over $10^5/A \textrm{cm}^2$at 77K. These films showed granular structure with 0.5~1.5$\mu \textrm{m}$ grains. Bridge-type junctions, 6$\mu \textrm{m}$ in width and 6pm in length, were fabricated using the photolithography and the Ar ion milling techniques. Current-voltage (I-V) characteristics of these junctions with the microwave irradiation at 77K were studied. The critical current densities decreased as the irradiated microwave power increased. When microwaves were irradiated on the bridge at 77K. the I-V charateristics showed constant voltage stcp(Shapiro steps) at $\Delta$=nho/2e.

2D fluid simulation of capacitively coupled plasma with cylindrical electrode for roll-to-roll processing

위성석,한문기,김동현,이해준,이호준,임종혁,전현수,황두섭,이영진 한국물리학회 2015 Current Applied Physics Vol.15 No.11

RF glow discharges are widely used in deposition, etching and surface treatments for semiconductor materials. Especially, roll-to-roll processing is necessary for flexible display or thin film solar cell modules. For a roll-to-roll thin film deposition processing, it is necessary to use cylindrical grounded electrode. The effects of electrode shapes on the plasma properties of capacitively coupled rf argon discharge at 13.56 MHz are investigated using self-consistent two-dimensional fluid simulation. The simulation model includes blocking capacitor and external circuit effects. Comprehensive analysis has been made in terms of time-varying currentevoltage characteristic, spatial distributions of plasma density and ion current density on the substrate. The effects of applied voltage (Vf = 200 ~ 800[V]) and gas pressure (p = 0:5 ~ 2 Torr) on the plasma properties are also investigated. We found that flat electrode has a little bit higher impedance than that of cylindrical ground electrode. However the difference between the two configurations is less than 5% therefore we may conclude that the shape of grounded electrode does not significantly affect current-voltage characteristics of the discharge system. For roll-to-roll reactor version, displacement current come from dielectric layer between electrodes reaches more than 75% of total displacement current. Large displacement current results in degradation of power factor and matching circuit efficiency. For the cylindrical electrode, increasing electrode gap length along lateral direction makes that the location of peak electron density moves toward center of the reactor. The effect of the cylindrical electrode on the plasma spatial structure is reflected in the ion current density at substrate (dielectric layer) on grounded electrode. At low voltage and low power condition, about 90% of input power is consumed for electron heating. The efficiency decreases with increasing power and decreasing pressure as a consequence of increasing power to drive ion current. Electron heating efficiency decreased with pressure. The increase of pressure mainly reduces the diffusive component of the loss rate for both charged and neutral species.