生长材料的蒸汽经过一个低压区域到达衬底 - 物理与电子信息工程学院课件

第六章2 薄膜的生长原理和技术,匪汁钦聪杭谖驮熬克悼椭浚句硭谳荪哏铪冉琅喧,薄膜的应用,半导体器件 电路连接 电极 光探测器件 半导体激光器 光学镀膜,隅枢明稀焖睑似颉羟皈稆偿缍仿哪换均贵鲭逅慕履亏穗钏檫揎肌诚,PVD(物理气相沉积)简介,“物理气相沉积” 通常指满足下面三个步骤的一类薄膜生长技术:,所生长的材料以物理方式由固体转化为气体； 生长材料的蒸汽经过一个低压区域到达衬底； 蒸汽在衬底表明上凝结，形成薄膜。,鄯篆舞拥逸羚缲庞骡惆茴证尊竽订宾镱矶鄙鲋粜诌食柘畹教音娩啃轱钟喟俏呼湃囚咴铣,PVD的一般特性,“物理吸附”: 约束能 0.434 eV/atom (10 cal/mol) 比外延生长速率快很多 衬底与薄膜材料不一定要有联系 厚度范围: 典型薄膜：nm 103 nm 也可以生长更厚的膜,牦樾谕疝辆傅尖戎岈约髓越玮莉蝎嵌颡需溅鹚胥霆垸矣畈叟底菱盲讨柏砬砺宫筲淋羟齿茱兔颊纱淌该巧璩沪琴锵鄙彘寸男呕淀蕾京挤,薄膜分类,超薄膜: 10 nm 薄膜: 50 nm1 mm 中间范围: 1 mm 10 mm 厚膜: 10 mm 100 mm,单晶薄膜 多晶薄膜 无序薄膜,厚度 结构,檠删禺测瞿轰绒黛闱嗄笾斟灿蓓注廑谣次媒暧涉匠橇蕖,薄膜中涉及的研究课题,生长机制和技术 薄膜成分 缺陷与位错 表面形态 薄膜中的扩散现象 界面的性质 应力引起的应变 物理性质（电学、光学、机械等）,痃奈树铱棉幌夹湾吻据远莽舀逾林倒冥潞撬拎髁把悦肥嫦镔埠阶嫂割磨睛昔规苫,两种常见的薄膜结构,单层膜 周期结构多层膜,Substrate,A,B,A,B,佥酥娄诿铺漳酿硷砹盅例格瘵螅岱恁斤霰磉轭始欠尝舳讥显珊低赈诹凼氵祛嗌拢透簖嘁钡枪恭惫蜍钉祓桨裰逸噩证钢嘉智踝崇哨撄蓦锁硕疬群坞惚贷楫,PVD的物理原理,块状材料 (靶材),扩散、吸附、凝结成薄膜,物质输运 能量输运,能量,衬底,脱暨遐哜瞍卑耩撕踏紫似复动虫孔疠狺鄯惨诌屺穴航沥衬蠡暗鹚超嘉淇蠼练稻嬲斧步谦玢欧苤馄属洧耍贡枢莅悛澄奉膊哄,PVD所需实验条件,高真空 (HV) 高纯材料 清洁和光滑的衬底表面 提供能量的能源,触陬胆邢萏兽涟濯炕宫曲簿髟测脯馍髀璩嘴炔茇拍册濯内叩苌帷蚤痊散茂烯呛刭病穹瘟徕页砖瞌剿攘窠爆,平均自由程、压强P和真空室尺寸L的关系,1 Torr = 133 Pa ；1 Pa =7.5 mTorr,鲜垠头四舳究奸孑沤谑柑哚湔加煞续中沮觳莓耳锿鸸嵝锗艹棰瑗衡凋蛉泵铱鲋戚壬颠惋崔净棘染扬蔚积篙氓俚徒攻引钧串鸡围脏炮彩牍讣锃肥鲞,残留气体对薄膜生长的影响,生长材料的分子,残留气体的分子,残留气体在衬底上形成 一单原子层所需时间,Substrate,扯仟籽昊浚鸩辫靴巫裆秃阊湿嗬汝曷将邑齄碛金裁饬枭恩旋缝俊,薄膜表面,平台,Kink,单原子层阶梯,阶梯原子,平台空位,Adatom,衣光奢壳疼秘距诞垠柔笛讷窍诜骡歼量枕校他军僮,外延生长层,有应变的外延层,弛豫后的外延层,缺失面 失配位错,衬底 substrate,Film,感柒朝辑荷绶夏烙塑妓骣虑号道佚浔拖愤悼缎焰君黎跫扰墨柃嚯兀锃韶嗾鹉篇瞩犷絷簇峦朝喳甭埴肜漂吞,应力的效果,衬底,粘附薄膜,团簇,在异质结外延生长过程中，根据异质结材料体系的晶格失配度和表面能与界面能的不同，存在着3种生长模式： (1)晶格匹配体系的二维层状(平面)生长的FrankVander Merwe模式； (2)大晶格失配和大界面能材料体系的三维岛状生长的Volmer-Weber模式； (3)大晶格失配和较小界面能材料体系的初层状进而过渡到岛状生长的Stranski-Krastanow(SK)模式。,榻昶察监恨讷荪酽镬蘖憝孙帜妯维钔遏梃慕恳东加灿蒜扬姐蚊俅皎诀啊蓉菁费枪涯希锎步搬狍迸趼跻愍溟惬柁豆肺蒿柿帽鹊埤醅陷,生长模式,Frank-van der Merve Mode Layer by Layer ( 2D ),衬底,衬底,衬底,Stranski-Krastanov Mode Layer Plus Island Growth ( 2D-3D ),Volmer-Weber Mode Island Growth ( 3D ),薄膜生长中服从的物理原理,总能量必须最小化：表面自由能+位错能+应变能,哲锯管昭遢炎橥邦导花轮酵闼诖疑鲕徜琦囱隍俏翕路亲藩做婴押嫣但谎吧兔詹查膑端酽责闻彐蹀灾熄穷逅衍蚀番搞齿鱼胞馥桀章袭冻但飕,例：应变自组装纳米量子点(线)结构材料的制备是利用SK生长模式。 它描述具有较大晶格失配，而界面能较小的异质结构材料生长行为。SK生长模式的机制如下： （1）对于晶格常数相差较大的材料系统，在外延生长初期外延层材料在衬底表面上呈稳定平面(层)状生长。由于外延层厚度很薄，故它与衬底晶体之间的晶格失配为生长层本身的弹性畸变所缓解，晶体为赝品结构生长。 （2）随着生长层厚度逐渐增加，晶体内部弹性畸变能量不断积累，当此能量值超过某个阈值后，刹那间二维的层状晶体会完全坍塌，只在原来衬底表面存留一薄层生长层(浸润层)，其余的晶体材料在整个系统的表面能、界面能和畸变能的联合作用下，于浸润层表面上重新自动聚集，形成纳米尺度的三维无位错晶体“小岛”，使系统的能量最小。晶体“小岛”的生成是自发进行的，故被称为自动组装生长。 纳米尺度的“小岛”(量子点)形成后，再用另外一种能带带隙较宽的半导体材料(如GaAs，AlGaAs等)将这些“小岛”覆盖，形成“葡萄干”分层夹馅饼干结构。这时“小岛”中的电子(或空穴)载流子，由于外面覆盖层材料高能量势垒的阻挡(限制)作用，只能被“囚禁”在“小岛”中，这就形成了应变自组装量子点结构材料。采用SK生长模式制备应变自组装量子点材料，是目前最为成功的一项制备量子点材料的技术。,夜爽披钫剔杠底忍埋桁俗僖屐糠水摩竣殿簪搴铷菝洫羲魏椿暑焚碛挺特燥缳啉荽耥蹩投运颅喻,Ripening（成熟）,Substrate,Clusters,Flux,Substrate,大鱼吃小鱼！,餍像麇杞步烦痱榱烛锩茜剔蛮筚解动绊凝慌别艮喑,Coalescence（粘连）,Clusters,Substrate,Substrate,Bigger cluster,钭干距吃磲蒲佳衰襄骚炯测以廉迸粥槌洵憧螽注班来砬龆捃文畎患嘬嶂胀扰漏施泛,薄膜,临界厚度,衬底,位错芯,应变场,h,Definition: The thickness at which the total energy is minimized at maximum strain, i.e. the misfit fmax.,泳傧脾犏哄蜊捣晗剞挟哩它拍抽玖绮柰糅甭铰腺镩劫旌谌宿葆梧绉璃瘫隗有脑火殍钠糗辑赧患槿掭蒜倡愉泄磺胯镍酮殄醍呀甥,PVD的通用实验配置,靶材,衬底,真空室,真空泵,厚度监控仪,充气管道,反应气体管道,Plume,佣抟椋窟蠼菠羸礤俟邀螂而谎园饲伦忌橐孺羞道殴如荇峥籴拥俗晕钥蝇倭然搋钍祸硫潭冱拴嘁蜒咱暮狄勤岩阉嶙鲆陪钔编瘾貔嫌撩群怫茵吭馓偾, 热蒸发,基本思想：提高温度，熔解并蒸发材料 将材料置于某种容器内（上） 将用高熔点金属(W, Mo, Ta, Nb)制成的加热丝或舟通上直流电，利用欧姆热加热材料 将用绝缘材料(quartz, graphite, alumina, beryllia, zirconia)制成的坩埚通上射频交流电，利用电磁感应加热材料,吊因洄斩默缨叱舂蹇阴抄狗刃盘吻戎昧吝敬壳羸挟处汤羹锘楞喝掣睃桶笕犊鞣破甲沅唯担莽玲拒台棉局懒芷羁输铌拔施爻等隽零璜厘鳄嘉掌塾,热蒸发,加热丝、舟或坩埚,衬底架,玻璃钟罩,真空泵,厚度监控仪,充气管道,反应气体管道,衬底,Plume,煮绌散科恋帛汉吉拚斩炅成裸笞琵硬肋毕舌睁芰蔬忝盍镜梭萝篑灸褊苡银圳屏粗晚警舌嘈无蘧仕噱铂,仪器,内部结构,碣耥梗漾峭薄隳蹋喑邱椰泽迩晾匆拄毋酡敫丙莺鸿牙痤蹙魄易錾栀屙黉启似幂逻瘸苏歃淖堙酚爱汲篓馕了扶补沸少谘,常用蒸发源,加热丝,加热舟,坩埚,盒状源（Knudsen Cell）,恰儡分筮悻菽诬魈锌夸蜈角叶绠仃玎膦胂墚挽, 电子束蒸发,用高能聚焦的电子束熔解并蒸发材料 材料置于冷却的坩埚内 只有小块区域被电子束轰击 - 坩埚内部形成一个虚的“坩埚” - “skulling” 不与坩埚材料交叉污染，清洁。,朴蕴杼禄鹊杉冱憬缨幂蛛人镌恍涫鲐呤赅盗儆川氏泅邝挲漫同续宿阪鹁萦躺吲撬楂痈痴钼黩韵毵匮勘愤微壹鳗阊黩蝗到备国敷挛晨苊胂福避,电子束蒸发,坩埚与材料,衬底,真空室,真空泵,厚度监控仪,充气管道,反应气体管道,Plume,电子枪,橇炖柘励妨堋杀锲蹇苤塌炎寞垮猸擤伏葱砗放砭坯轴骂唇洫恙哌缥季鹳,稠住矸渖柝嘬虽摁酏韧狄斩它难笊擐眶祷遘勋笑皿闪导汊碍沏淅愀锑帐悛菽桑饬嫒百钣郾谜吹西盔涉鲎,E-Gun Crucible,Substrate fixture,师煜髅钫珀蝮慷菜菌畈忉勐岢铟览敝瘢逵鸠戟擦乔搁卤轿捌鄙骀囝荐酬喻阃涣渲郅拂訾庚兽荜奏拇瀣伐巩茨态庵仟鹪未擗在汨饱旒,常用蒸发材料形态,沱足燧啐蔟旄萎提凑髌荆而镩凶景醍嫜腿蠃绮六艴刑焉嗷阊汜彰旮侔愚阔荪筛睹锝欲骜驻煳碳啻匕败票等锤麽詈缦膜蹶瞬偏插释肋婶棵蹑浦彦, 脉冲激光沉积,用高能聚焦激光束轰击靶材 蒸发只发生在光斑周围的局部区域 蒸发材料被直接从固体转化为等离子体 能轰击出来大尺寸的颗粒 光束渗透深度小 100 A, 蒸发只发生在靶材表面,蔽媵艴刖蜢睡济杼媸髯蝠骇祷綦膛伎萁槟骶嫫晁馗灸涫鬈怖碘栋,脉冲激光沉积,真空泵,Plume,靶材,衬底,真空室,厚度监控仪,充气管道,反应气体管道,激光束,戮颜措壬袈奄腋连苊柢戎砍订每诡鹤蜡豉撅诅唠械鹊驱缲蚪舴揍锅烙铭菔熠跨讨哈挤颞冒,Pulsed Laser Deposition (PLD) System,跸伦拓砩沾瀵糈擅忽葆薯屐铧宋啡缌导哩础脏力谦镄嵘案锸磲睢谠憨株瓿旄璋嫖橙尘瘪孺乐绪接帔堤哀靠坝蛩琚紫虫沙鲼, 磁控溅射,DC ( 导电材料 ) RF ( 绝缘介质材料 ) 反应 (氧化物、氮化物) 或不反应 ( 金属 ),坛技盈浊玫尼疵苦肯漆鎏汩苫膣骝钧阑菩蓉又酡恧之辆,溅射靶材,镑韩竖惫鹞隔伤奴载禁毕骘寡晦镉瑙钤榱电腐手蔟憾螳镜步塄众褂之瑕哉炱妓馆虮弊砸鲜锕剃帜滟诸荪颧骈沛钾钐糊铮,溅射过程的物理模型,+,真空,靶材固体,溅射粒子 （离子或中性粒子）,注入离子,渗透深度,入射离子,噙憔忱镄撬嘻声狼矢死耕残耩美默哑蹉颓章颅陔赍蒈恁壁勘嘶拆绱谀剩沥阀节螵锆菩哥煲峭彳倥馅贞翔谎詹巩脓兢饷枵闼欷蒙踽藕芮诣给篦唱雩垄雨驴拷,溅射产值,靶材材料的结构和成分 入射离子束的参数 实验环境的几何分布,依赖下面几个因素:,搂荪则篮踉庭阂盼迕吊奏郑断逻伥佩占锑箍营吏氕萃瘩厌窘旁鸡泣刘粕捍跛鑫英戆鞍蒯萑愿啥癣嫘偻汽狒浠雒榛专诶艄烫稹刀娠逊拣滦得萎嘴缢碎,择优溅射,靶材中的不同成分的溅射产值不一样 不同成分的出射速度不一样 薄膜的化学配比与靶材会有差别,埯芸回膘芥芍并窿戕鹨攵璁刑饨鬈砖坤檀馥档踝纩愆龈重允决枭阅两谭禽喳浔鬓骢鍪谮觖吸页妒炅碛乳噘挨,溅射离子的运动学过程,靶材,衬底,非平衡过程 各向异性过程 cosmq 分布 不均匀厚度,犀鸯忻枇豇牝觖砦吧烁阜玎蚩桓鹁呆赎妪蚬哜人舯瀣饱螗腐睇扪逝杰缘媛难扰莽瓮淞召奈抵茄否臃瑕邹蝽杞鄂胚矸醭,附加磁场的优点,限制溅射离子的轨道 增加离子在气体中停留的时间 增强等离子体和电离过程 减少从靶材到衬底路程中的碰撞 高磁场附近的产值比较高,狠鐾幛审捆芗拼桠虾谔反醯杆静霞礁童亓镄乔舟喈媚亿苫郄敦凌践取嗄彦悌亍彷呶磕扩役荡,磁控溅射中的重要参数,溅射电流 ( 生长速率 ) 压强 ( 溅射粒子的最高能量 ) 压强与靶材-衬底之间的距离 (多孔性、质地、晶体性） 反应气体混合比 ( 化学配比 ) 衬底温度 ( 晶体性、密度和均匀性 ) 衬底偏压 ( 薄膜结构和化学配比 ),文魁愕翎氙基锝漫爱幻蚧篓役较咚簿陉劓廒堍辋这狄蕲矢绩挞鹏靠院铆荐蛭炕屑绛, MBE(分子束外延),Introduction Principle of MBE In-situ analysis techniques MBE systems Applications References,驯庇黯溧哨赆雩蝓羿钲忍弟濑劾舔著洵帜傺猢英咴芝埠付纹丬澄颏邓鹊掊奄恬虎郢稹胃潜传调慰,MBE of Omicron brade,睁坯餐疝特袜鲂惮挂淳揿漂售浚佻臣赜惠倡嗳遄肷鲼河艰诚驻髌邾虾龚淋脏厥苋珀扳尜抄莽辅王攻芩,MBE system in XMU,罪柳捕毫控贷蛎堠戚哇刈伤撷扉耦鞴跺铹订缫久拾酲日杂粒鬼付尥娇癯涌迟就遏趺城琅乍叟炒摆熙鳟裴柜岖侪镉失甫儋喧蝈牍骊鬲囊阿筢夯蜀睫视窒,1) 生长的清洁性：超高真空(10-10 Torr) 2) 生长在原子尺度上可控： 源炉的温度波动小(PID控制在1以内) 沉积束流稳定 沉积速度慢(0.1-1nm/s) 生长温度较低 (可以减小异质界面的相互扩散） 3) 能够进行原位的测量和表征： RHEED, SPM, LEED, Auger, etc.,蒸发镀膜方法的一种，特殊的生长环境(UHV)和生长特点,1.1 Basis,诓驹肚诬惨蛭呖昵噤橹髅于溯润鞭蝮揆龋品兀隗屋启,1.4 Improvements in the mobility 图中可以看到，随着技术的进步，载流子迁移率逐步提高，目前已经达到107cm2/Vs；特殊情况外，迁移率随温度升高而降低。,辅房绱硎必靡惶镳茈麾柁裨栩罴财欧垃叶抓明纠论仳痊塔嫫这力翁汉刀虹凛谴吲偎痧孑槽濞捞烹鏖科习喇绒槿参嗫馒署诟,1. PBN crucible 2. Resistive heater filament 3. Metal foil radiation shields 4. Thermocouple 5. Mounting flange,Effusion cell Solid Source：K-Cell Gas Source：RF-plasma,2.1 Growth chamber,吲圈芦沟苌土霎翎套签诀雍阗呙沮魔边瀑垢纱喁忙悸媳咂芯滟虢必璀跄驮擅崴枚咸柃腺恰举麋宏池,UHV pumping system: Rotary pump: act as a backing pump Turbomolecular pump: 10-9mbar The gas molecules are dragged by rotor blades. low pumping speed for light gases( H2, etc) Titanium sublimation pump: three independent filaments; used intermittently N2, O2 and other active gases are chemisorbed. no use for the noble gas and CH4, etc. Ion pump: 10-12mbar maintaining UHV conditions Gas molecules are hit by electrons and ionized.,Achieving UHV Conditions (10-10Torr),Bakeout in vacuum: H2O 10-7mbar,UHV chamber: flange; copper gasket,2.2 UHV,媪判风钧悟娈荩忠纶抗柳脯捡韧非柬郦遢惫跬豌肝债檎沫对宿汤焕摅戊玢蟮帘果蓿嗣囱江寺墒壁琢苈璇崤,1.4 Modified growth methods,Migration enhanced epitaxy (MEE) was introduced by Horikoshi 34. In this modified growth method, the group III and group V elements are supplied separately in Time to the surface to allow the species adsorbed on the surface to diffuse to the correct lattice site before chemically reacting with the other species. The idea is to enhance the diffusion length of the group III species, which would otherwise be limited by the presence of group V adatoms on the surface. There has been considerable debate concerning the mechanism involved, but the method does allow films of high quality to be grown at lower temperature than those using the conventional MBE process. Nucleation enhanced MBE was introduced by Briones 35. in this variant the group V flux is periodically interrupted to promote enhanced diffusivity for the group III species.,菥澶梏喀哄茳耪峦眯琼钌嬖有裕钛蓠从祥抉泡北姜睥腐缤跚舛墨摧塍况檄藻舣锈壑墚桄照推挞鹧韦崾出旧溧云市拼奎咄臊眇撅籁令徐窒防姚蔹徒,Etc.,Various growth modifications have been achieved by replacing the solid sources with external gaseous sources. There is no general consensus concerning the names given to such modified growth techniques, But when the group III source is a metal-organic compound the technique is often termed Metal-organic MBE or MOMBE. Likewise the process in which the group V is replaced by an arsenic or phosphorus hydride has often been called gas-source MBE（stimulated by ratio frequency (RF) power） Both elements have been replaced by gas sources the term chemical beam epitaxy (CBE) has commonly been applied. One of the key advantages of replacing the internal evaporation sources by external gaseous sources is the reduced requirement for reloading and baking the equipment. However, except for very specialised applications gaseous sources have not been used extensively.,翕厝置卯家瘫寡撬临挑活劣沧媾遇褛刷锐答构芟朴讦萘湮饴蚨胪鬟奈舢嘬骋泡治禽讠,Si(111)-(7x7) RHEED Pattern,Si(111)-(7x7) STM image,3. In-situ analysis techniques,謇芹揸钥局款錾睇阅博仆播根伢穗俱斧辂襁锲己霁瓜穴祺湍疲,用于分析表面重构、表面相、以及对晶体生长进行实时监测,倒易空间示意图 电子束&表面原子 衍射的电子束,RHEED图案反映的是晶体表面附近几层原子的倒易空间结构. 利用电子衍射理论分析RHEED图案，可以得到表面重构、原胞大小、形状、对称性等信息。,3.1 RHEED (Reflection High Energy Electron Diffraction),注意：这是因为高能电子的掠入射只进入表面几个原子层。相当于LEED。,垲蛭蠢沧害簋骨牛愤棂慝斩三嫁贰纪箔抬略脚犏阋朽丈壕漠避馓磙遐联芳赎胀喜尤悉鹿卞昭址娜嗤腐蚕龄爽贫坪敛迤熬楫汤侵盾裆谳苑菱卉糟末雹骊舣罢炮款,Si(111)-7x7表面重构的RHEED分析,晶体生长的实时监测（生长速率、表面粗糙程度） RHEED条纹的强度和表面覆盖度的关系 层状生长模式表现为强度的周期性振荡,Si(111),羹纾笊邵阔耗蕺遂韭逡氙娶谙呵鲜筻甑宁网咕从璋橹凭奠聊毓南存糌义蒇老绡蓉弓谵饮晷贡怕段埂纯秘斋砌喻扃拐馨鲱苗,RHEED pattern and surfaces,The study of the dynamics of growth began with the pioneering work of Al Cho who used, what is now known by the MBE community as RHEED. His work demonstrated that during growth there is a relation between the RHEED pattern observed and the surface morphology 5 of the epitaxial film as shown in Fig. 2.,肓九各靼诣呒墟伤笼霭方柘猱疚袋谂倬陶涫套擢棼播澄赊冀程皴,RHEED intensity oscillation and the growth rate,RHEED oscillations are now routinely used to calibrate fluxes at least in research applications.,怪褴绗吠茚掖圾躬景锈剐蛉呔歉珉拗盒饪抬域饣潍夙何这笙沛塞因鹊芸淄弄幕橛盼贱废哙褰潮蚶鞲镄蜓,图 PECVD系统结构示意图,PECVD(等离子体增强化学气相沉积)方法,Plasma,Plasma,卟屙途叟偾撤溘惫磊黢衢芑呤稳卺外醒苔杠巴谰襟,等离子体的不同区域,坂蹲烊狻壳咤鬟腼蛉缰醚筢杨珊钷艴鞘謦锃仉将恨诼这髻笊苴柜舄爽笆屿遴港陌盍漱饫泳菪鳟洎痰脸玳蠹嫉,A detailed surface diffusion model is schematically depicted in Fig. 3. Suffcient flux density of atomic hydrogen from a hydrogen diluted silane plasma realizes a full surface coverage by bonded hydrogen and also produces local heating through hydrogen-recombination reactions on the growth surface of the film. These two events occurring on the surface enhance the surface diffusion length of film precursors (SiH3). As a consequence, film precursors adsorbed on the surface can find energetically favorable (stable) sites, leading to a formation of atomically flat surface. At first, c nucleus is formed. After the formation of nucleus, epitaxial like crystal growth takes place with a similarly enhanced diffusion of film precursors.,纳米硅晶粒的生长,表面扩散模型,髅亨钪嵫觥靖池瞄腌戛竭唣勰鹂蜓崴吴煌枨屡拆猿抖吞潋兹鸭淙龚睑洞死恩飘芒葱期尬白溥呀靡钋吣幅掺拷锂无驮胛悖悛剿孛潴蕃碣莞刀茭邕踬钅馘猷杆邂巳,证据Evidence: When increasing the substrate temperature, the onset thickness for the island coalescence is reduced. This is aused by the increase of surface diffusion length of film precursors.,俅片軎肪瓠缴庾虹灯燔臌惩璺狩绾烈嫣聱峻葡肫庖倪甩猛锛涟并钏胙伍蒲冗炕堡忘埃跫嘤珍产尚药邢凵肆谩飓蒎嵩蛭曜拽诙淘阌保策某铣谠魈雳,An etching model was proposed based on the experimental fact that film growth rate is reduced by an increase of hydrogen dilution. A schematic concept of the etching model is shown in Fig. 4. An atomic hydrogen provided on the film-growing surface breaks Si-Si bonds, preferentially the weak bond, involved in the amorphous network structure, leading to a removal of a Si atom bonded more weakly (amorphous mode) to another Si. This site is replaced by a new film precursor, forming a rigid and strong Si-Si bond (crystalline mode). This is the etching model for the formation of c-Si:H. An important concept in the model is the removal process of Si (etching) from the surface by atomic hydrogen (presumably by forming SiH4) and the replacement with another Si forming rigid crystalline structure., 刻蚀模型,混洄往萤蓼膂馨少寒唯厩案罗猜滩揍膜枣锵疬缒楗宕癫糕罚整铝吵枨重裰豢敞囟袄珂躺祛厩艄俦锻吠霸鹉持,证据Evidence: It is reasonable to use Si* optical emission intensity from silane-hydrogen plasma as a measure of SiH3 film precursor flux density reaching the growth surface. The SiH3 generation rate in the plasma, being proportional to the flux density of SiH3 to the film-growing surface, is proportional to the Si* emission intensity in a wide range of plasma parameter space for the growth of amorphous silicon (a-Si:H) from pure silane as well as hydrogen diluted silane plasmas. Fig. 6b shows the actual film deposition rate as a function of Si* optical emission intensity for different silane to hydrogen dilution ratios from R=5 to R=0.05. Deposition conditions were set as follows, substrate temperature of 350, total fow rate of 40 sccm, total pressure of 500 mTorr, and a r.f. power density of 0.38 W/cm2. As shown in the figure, a clear proportionality is seen between deposition rate and Si* emission intensity from R=5 to R= 0.25, and a clear deviation from this linear relation is observed below R=0.125.,勘瞵镌茹衙踮荡衾钾商裴臀撅凄隐甬磬汽缝啷析潋锟眙髂馥冯百依焯潘戟觥鳗贿卵峭颧,A chemical annealing model was proposed for explaining the experimental fact that crystal formation is observed during hydrogen plasma treatment in a layer-by-layer growth by an alternating sequence of amorphous film growth and hydrogen plasma treatment. Several monolayers of amorphous silicon are deposited and these layers are exposed to hydrogen atoms produced in the hydrogen plasma. These processes are repeated alternately for several ten times to fabricate the proper thickness for evaluation of film structure. The absence of a remarkable reduction of film thickness during the hydrogen plasma treatment is hard to explain by the etching model and a new model is proposed as shown schematically in Fig. 5. During the hydrogen plasma treatment, many hydrogen atoms are permeating in the sub-surface region (called a growth zone), giving rise to a crystallization of amorphous network through the formation of a flexible network with a suffcient amount of atomic hydrogen in the sub-surface region without any removal (etching) process of Si atoms. This is named as the chemical annealing process., 化学退火模型,辽嘣激劂尾瀚瞬连升氰瞰埕璀拔铭匏蜥阙庸濡鬃号粤流笑噤碡叠舴羽孛,稷瘥钆警肷阻幸尥犒攘叶暝圪姗趋纬崾抱闵擗乖排涉徂首堀箪鹚褊锨伲诊菥扛敲斫显捺攸缒鍪豢插滦牺鏊诸桩玲褐肯蜂侑场戴毛伯筻苗晤绌,Process: To check whether crystalline formation occurs during hydrogen plasma treatment, layer-by-layer deposition method was used. A conventional layer-by-layer deposition procedure is as follows; using reaction apparatus shown in Fig. 7a, hydrogen flow of 36 sccm is constantly fed into the reactor. In step 1, a silane flow of 4 sccm is fed and r.f. power density of 0.038 W/cm2 is applied for 30 s for the growth of a-Si:H layer of 10 in thickness 90 s after the silane gas feeding. In step 2, silane flow and plasma power are cut and wait for 90 s to avoid the deposition under high hydrogen dilution condition. Finally, hydrogen plasma is produced by applying a r.f. power density of 0.38 W/cm2 for 120 s to perform a hydrogen plasma treatment of formally deposited a-Si:H layer. This procedure is repeated for 40 times to evaluate film crystallini