奈秒脈衝Nd:YAG雷射系統於光電材料表面製程之應用與研究

Abstract

近年來透明導電材料、非球面玻璃透鏡和高複雜形狀玻璃基板廣泛應用於3C商品(如電腦、通訊和消耗性電子產品)，以滿足光電和半導體產業迅速發展。為了要增加生產速度、降低生產設備沈重投資和減少對環境化學傷害，目前微奈米雷射製程紛紛被廣泛使用，其技術包括雷射剝蝕、雷射銑削、雷射退火、雷射刻紋、雷射處理、雷射沈積等。新穎雷射直寫和雷射背寫技術也被開發應用於材料表面製程。 本研究目的係使用奈秒脈衝Nd:YAG雷射系統發展材料表面製程技術應用於光電產業，並瞭解雷射與材料加工之間交互作用關係。在觸控面板電極絕緣研究方面，使用1064 nm波長之Nd:YAG雷射於氧化銦錫薄膜進行劃線，其薄膜分別鍍製於鈉鈣玻璃(Soda-lime glass)、聚碳酸酯(PC)和環烯烴共聚物(COC)三種不同基板上，薄膜厚度分別為20 nm、30 nm和20 nm。最大雷射功率固定在2.2瓦，調整雷射照射時間從10 μs到100 μs，探討薄膜劃線後寬度、深度和導電特性。另外，藉由掃描式電子顯微鏡、三維共焦雷射掃描顯微鏡、原子力顯微鏡和四點探針量測薄膜表面形貌、表面交互作用、表面粗糙度、光學性質和導電性質。雷射劃線後氧化銦錫薄膜表面形貌量測結果顯示：當雷射照射時間在10 μs和20 μs時，雷射劃線路徑上仍有殘留氧化銦錫薄膜；當雷射照射時間在30 μs到60 μs間，可獲得較佳品質之雷射劃線；當雷射照射時間大於60 μs時，聚碳酸酯(PC)和環烯烴共聚物(COC)塑膠基板上雷射劃線薄膜會產生局部燒焦區域，且當雷射照射時間增加時，絕緣線寬度和薄膜電阻率也隨之增加。 矽基板表面粗糙圖案製程研究方面，係調整脈衝Nd:YAG雷射不同能量密度和脈衝作用時間，探討表面刻紋之微結構與表面粗糙度。掃描式電子顯微鏡和三維共焦雷射掃描顯微鏡分別用於量測雷射表面刻紋後之矽基板表面微形貌和表面粗糙度，FTA 188接觸角量測分析儀用於液珠與刻紋基板間接觸角量測。實驗結果指出：增加雷射密度和雷射脈衝作用時間，使得較多熔渣堆積在這些圖案周圍而形成微火山口，且會增加火山口高度和表面粗糙度。水滴在雷射刻紋後矽基板表面之典型例子顯示：水滴非常迅速攤開，幾乎在0.5167秒內就完全消失不見；相較於水滴在未經過雷射刻紋處理之表面，其接觸角為47.9度。另外，脈衝Nd:YAG雷射搭配雷射誘發背寫製程和雷射誘發電漿輔助剝蝕技術，用於鈉鈣玻璃表面加工粗糙陣列圖案。實驗結果顯示：隨雷射加工次數和單發雷射曝曬時間增加，加工後表面形成之火山口高度和深度也會增加。接著在雷射背寫加工後玻璃表面鍍製一層695 nm鐵氟龍薄膜後，其表面變成疏水特性。水滴在玻璃基板鍍製鐵氟龍薄膜表面之典型例子顯示：其水滴接觸角為118.6度；當水滴在環形溝槽樣板鍍製一層鐵氟龍薄膜，其水滴接觸角提高至131.3度。 Nd:YAG雷射表面處理技術應用於玻璃模造模仁保護膜方面研究，係使用離子源輔助磁控濺鍍系統鍍製不同合金薄膜成分，包括鉑(25%)-銥、鉑(50%)-銥、鉑(75%)-銥、鎳(25%)-銥、鎳(50%)-銥和鎳(75%)-銥合金。在合金薄膜與碳化鎢模仁表面間鍍製一層鉻膜當作緩衝層，接著Nd:YAG雷射直接應用於表面處理製程，探討合金膜於高溫環境下之表面性質。在雷射表面處理1500℃後，當鉑和鎳成分增加時，表面粗糙度也隨之增加。因薄膜受到高溫工作環境而產生氧化，這些薄膜表面是較粗糙、低微硬度和低彈性模數。因此，建議這些銥合金薄膜在真空環境和填充保護氣體操作對玻璃模造製程是有益的，可避免嚴重表面氧化和降低表面粗糙度值。

In recent years, transparency conductive materials, aspheric glass lenses, and glass plates of highly complex shape with fine edges were extensively used in 3C market products (i.e. computer, communication, and consumer electronics) to meet the rapid development of the electro-optical and semiconductor industry. In order to increase the processing speeds, to reduce the heavy investment of the processing equipment, and to decrease the chemical harm to the environment, current laser micro- or nano-machining processes employ techniques including laser ablation, laser milling, laser annealing, laser texturing, laser treatment, laser deposition, etc. Moreover, novel techniques, laser direct writing and laser backside writing methods, are also developed to use in the surface process of materials. The purposes of this dissertation aim to develop the surface processing techniques on materials used for the optoelectric applications by a nanosecond pulsed Nd:YAG laser system and to better understand the interaction between laser beam and materials. In the electrode isolation for touch panels, the Nd:YAG laser with wavelength of 1064 nm is used to scribe the indium tin oxide (ITO) thin films coated on three types of substrate materials, i.e. soda-lime glass, polycarbonate (PC), and cyclic-olefin-copolymer (COC) materials with thickness of 20 nm, 30 nm, and 20 nm, respectively. The effect of exposure time adjusted from 10 μs to 100 μs on the ablated mark width, depth, and electrical properties of the scribed film was investigated. The maximum laser power of 2.2 watts was used to scribe these thin films. In addition, the surface morphology, surface reaction, surface roughness, optical properties, and electrical conductivity properties were measured by a scanning electron microscope, a three-dimensional confocal laser scanning microscope, an atomic force microscope, and a four-point probe. After laser scribing, the measured results of surface morphology show that the residual ITO layer was produced on the scribed path with the laser exposure time at 10 μs and 20 μs. The better edge qualities of the scribed lines can be obtained when the exposure time extends from 30 μs to 60 μs. When the laser exposure time is longer than 60 μs, the partially burned areas of the scribed thin films on PC and COC substrates are observed. Moreover, the isolated line width and resistivity values increase when the laser exposure time increases. In a surface-texturing technique to create rough patterns on a silicon substrate by the pulsed Nd:YAG laser system, the different degrees of microstructure and surface roughness were adjusted by the laser fluence and laser pulse duration. A scanning electron microscope (SEM) and a 3D confocal laser scanning microscope are used to measure the surface micrograph and roughness of the patterns, respectively. The contact angle variations between droplets on the textured surface were measured using an FTA 188 video contact angle analyzer. The results indicate that increasing the values of laser fluence and laser pulse duration pushes more molten slag piled around these patterns to create micro-sized craters and leads to an increase in the crater height and surface roughness. A typical example of a droplet on a laser-textured surface shows that the droplet spreads very quickly and almost disappears within 0.5167 s, compared to a contact angle of 47.9° on an untextured surface. In addition, the pulsed Nd:YAG laser is also utilized to fabricate rough array-patterns on a soda-lime glass plate by a laser-induced backside writing (LIBW) process and a laser-induced plasma assisted ablation (LIPAA) technique. The measured results show that crater height and depth gradually increases with increasing number of passes and single-shot laser exposure time. After a 695 nm thick Teflon thin film is deposited on the glass plate, the micro-machined template surface becomes hydrophobic. The typical measured contact angle on a planar glass substrate coated with Teflon is 118.6°. The contact angle increases to 131.3° when the water drop is added on a round annular-grooved template coated with Teflon. In the Nd:YAG laser surface treatment technology for the protective coatings of glass-molding dies, a variety of alloy films, including Ir-25 at.% Pt, Ir-50 at.% Pt, Ir-75 at.% Pt, Ir-25 at.% Ni, Ir-50 at.% Ni, and Ir-75 at.% Ni compositions are deposited by the ion source assisted magnetron sputtering system (ISAMSS). A Cr layer that functioned as a buffer layer is deposited between the alloy film and die surface. After an alloy film and the buffer Cr layer were sequentially coated on tungsten carbide (WC) surface, Nd:YAG laser was directly applied in the surface treatment process. The temperature profile of the film stacks structure is simulated by ANSYS software. After laser surface treatment at 1500℃, the values of surface roughness are obviously increased as increasing concentrations of Pt or Ni. These surface films are high roughness, low microhardness and low reduced modulus because of the film oxidation occurred in high working temperature process. Therefore, these Ir-alloy coatings operated under the vacuum environment and filled with protective gas are useful in glass molding to avoid the severe surface oxidation and to reduce surface roughness.