マグネトロンスパッタ法による薄膜太陽電池用AZO透明導電膜の作製

摘要

マグネトロンスパッタ法で作製するAl添加酸化亜鉛（AZO）透明導電膜を薄膜太陽電池用透明電極用途へ適合化することを目的として、使用するスパッタ成膜方式と得られる膜特性との関係を調べた。中型矩形ターゲットを用いるマグネトロンスパッタ装置を用いて、直流、高周波及び高周波重畳直流マグネトロンスパッタ成膜方式を使用して、ガラス基板上に基板温度200[℃]でAZO薄膜を作製し、その電気的及び光学的特性について検討すると共に、濃度0．1[mol／l]の塩酸溶液を用いた湿式エッチングにより形成する膜表面テクスチャ構造と光散乱・閉じ込め効果との関係について検討した。%In order to determine the influence of different types of MS depositions on the characteristics of AZO thin films appropriate for applications as transparent electrodes in thin-film solar cells , transparent conducting Al-doped ZnO (AZO) thin films were prepared on glass substrates at 200t by direct current (dc) magnetron sputtering (dc-MS), radio frequency (rf)-MS and rf power superimposed dc-MS (rf+dc-MS) depositions using a MS apparatus with the same AZO target. AZO thin films prepared by an rf+dc-MS deposition exhibited both a higher deposition rate than that found with rf-MS depositions and a lower resistivity or higher Hall mobility than those found with dc-MS. The lower dc sputter voltage featured in rf-MS and rf+dc-MS depositions resulted in lower damage depositions, producing smoother surface morphology and better crystallinity than obtained with dc-MS depositions. The light scattering characteristics of surface-textured AZO thin films prepared by various types of MS depositions were evaluated by observing the surface texture and measuring the optical transmittance and the diffusive component. The obtainable haze property in the range from visible to near infrared in AZO films prepared by an rf+dc-MS deposition was markedly better than that obtained with dc-MS depositions.