Abstract
微波所產生的電漿較無線電波所產生的電漿有較高的密度與離子化比例. 另外,微波電漿也能有效的產生化學基和斷裂的分子. 然而,由於微波的波長短和它進入電漿的穿透深度小. 因此,難以產生大體積的均勻電漿來供給工業上的大面積製程使用. 同時,電漿的產生會大幅度的改變微波的傳輸性質而因此導致無法產生大面積電漿. 在本研究中,使用了兩個物理機制來克服上述的困難. 第一個是微波功率必須均勻分布在所要產生的電漿面積上. 第二個是微波前進的結構必須與電漿產生的區域分離. 由以上兩個機制可以產生三十公分乘六十公分大的電漿. 本研究使用的是一個十二週期的鋸齒狀慢波結構來形成一個操作在Pi模且共振在2.45GHz的可調式表面波共振腔. 上述平面形的共振腔放置在距離真空腔上方三公分的位置,且以兩塊石英玻璃作為真空腔和共振腔間的微波偶合介面. 由上述的安排,可以在真空腔中激發電漿的表面波. 在本研究中,電漿性質,如電漿的濃度,溫度,和空間的均勻度的量測均是由單靜電探針所完成.本研究主要針對Ar氣體產生的電漿,研究其在不同的氣壓和微波功率時的性質. 微波功率最高可達五千瓦,操作氣壓從0.005torr到40torr. 所得到的電漿密度超過1E10^12(#/cm^3),而電漿溫度是1.0eV. 本研究已產生一個三十公分乘六十公分大的均勻電漿. 本研究的結果可以直接被放大成為工業上的應用.Plasmas generated by microwave (2.45GHz) illustrate a higherplasma density and ionization ratio than radio frequencyplasmas (RF plasma). It also shows that chemical radicals andmolecule fragments can effectively be produced by microwave.Nevertheless, it is difficult to creat large volumehomogeneous microwave plasmas serviceable for large areamaterial processing due to the short microwave wavelength andsmall penetration depth of the microave into the plasma.Meanwhile, the appearance of the plasma can significantlychange the transmission property of the microwave and canresult in the failure of producing a large area plasma. In thisstudy, two physical schemes are employed to overcome thisissue. The first scheme is that the microwave power requiredfor discharge is distributedly coupled over the desiredplasma area. The second scheme is to separate the mainmicrowave propagation structure from the plasma productionregion. As a result, a large area plasma with an area of30cm X 60cm can be successfully produced. A12-period vane-type slow wave structure is constructedto form a tunable surface wave cavity which is operated atpi-mode and resonant at 2.45GHz. This planar cavity is locatedby 3cm distance to the top of the vacuum chamber where twoquartz plates (30cm X 30cm) are installed as couplingwindows to the microwave power. With this arrangement, asurface wave mode is excited in the plasma. Measurementsof plasma properties, i.e., plasma density, temperature, andspatial uniformity are undertaking by a Langmuir single probe.The source has been operated with a varity of pressure and powerand this study focuses on argon. Microwave power up to 5kW havebeen applied andthe pressure varied between 0.005torr and40torr. The plasma density inexcess of 1E12 #/cm^3 has beenobtained. The electron temperature is 1.0eV. An uniform plasmasource of 30cm X 60cm has been achieved. The results can beeasily scaled up to commercial use.