CN109164603A - 一种基于转移打印在硅上低温集成石榴石薄膜的方法 - Google Patents

一种基于转移打印在硅上低温集成石榴石薄膜的方法 Download PDF

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CN109164603A
CN109164603A CN201810858214.0A CN201810858214A CN109164603A CN 109164603 A CN109164603 A CN 109164603A CN 201810858214 A CN201810858214 A CN 201810858214A CN 109164603 A CN109164603 A CN 109164603A
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毕磊
肖敏
王会丽
夏爽
康同同
邓龙江
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Abstract

本发明属于集成光学领域,具体涉及一种基于转移打印在硅上低温集成石榴石薄膜的方法。本发明中,利用化学自组装法在SiO2/Si基底上六角密排PS小球,再用氧等离子体轰击PS小球使小球直径缩小,用脉冲激光沉积法在室温下将磁光石榴石薄膜沉积到氧等离子体轰击后的PS小球上,用甲苯清洗PS小球使PS小球及其上的石榴石薄膜脱落,使得在SiO2/Si基底上留下孔洞状的石榴石薄膜,最终使得刻蚀速率大大提高,且减弱了石榴石薄膜被HF腐蚀的程度。刻蚀完全后,用PDMS印章取下悬空的石榴石薄膜,再把石榴石薄膜印制到硅基底上,实现了石榴石薄膜在硅基底上的低温集成。

Description

一种基于转移打印在硅上低温集成石榴石薄膜的方法
技术领域
本发明属于集成光学领域,具体涉及一种基于转移打印在硅上低温集成石榴石薄膜的方法。
背景技术
磁性非互易性光学器件如光隔离器,是实现光单向透过,避免激光频率和强度噪声的重要器件,是光通信领域里保障系统稳定、实现高效光学系统设计所不可或缺的元器件。商业化的隔离器是基于块体材料的法拉第旋转效应工作的,技术已经很成熟,但是其体积大,成本高,无法与其他半导体集成光学器件兼容。因此,对于片上集成磁光隔离器件的研究变得极其重要。磁光隔离器使用磁光材料的非互易性打破光传播的时间反演对称性,磁光材料的性能对于片上集成的磁光光隔离器的发展起到至关重要的作用。目前磁光隔离器中广泛运用的磁光材料是石榴石薄膜,但是石榴石薄膜材料很难在半导体基片上集成,主要有以下两个原因:一是石榴石结构的结构单元很大,对应的晶格常数相对于半导体材料大很多(如 ),无法在半导体材料上实现石榴石薄膜的外延生长;二是石榴石的热膨胀系数相对于半导体材料大很多(YIG:10.4×10-6/℃,Si:2.33×10-6/℃,GaAs:5.73×10-6/℃),要得到结晶石榴石薄膜需要进行高温处理。然而高温处理导致材料生长的热预算高,无法与半导体工艺兼容,限制了隔离器的进一步应用。
为了将离散的微米/纳米级元件大规模集成到任意衬底上,M.A.Meitl提出了一种转移打印(transfer printing)技术,并被广泛运用于各种无机薄膜,如GaAs、金刚石薄膜等柔性器件的制备工艺中。近年来,研究者们陆续采用改进的转移打印法将功能性氧化物薄膜转移到任意衬底上,如在SiO2/Si基底上生长VO2薄膜,通过BOE刻蚀液选择性刻蚀SiO2牺牲层,再用PDMS印章将VO2薄膜转移到柔性衬底上,但是其存在薄膜在转移过程中被刻蚀液腐蚀以及破裂严重的问题。
石榴石薄膜作为磁光材料在磁光隔离器中广泛运用,但石榴石薄膜在硅上集成的热预算过高限制了其进一步的应用,而关于石榴石薄膜在硅上低温集成的方法目前还没有。常规的采用BOE刻蚀液刻蚀SiO2牺牲层的转移方法刻蚀时间长,刻蚀液会严重腐蚀石榴石薄膜,且薄膜破裂严重,大大降低了薄膜的性能。
发明内容
针对上述存在问题或不足,为解决现有石榴石薄膜制备时存在热预算高,无法与半导体工艺兼容的问题;本发明提供了一种基于转移打印在硅上低温集成石榴石薄膜的方法。
本发明选用SiO2/Si基底,用化学自组装法在基底上排列Polystyrene(PS)小球,PS小球呈六角密排形式,用氧等离子体轰击PS小球缩小其直径,然后利用脉冲激光沉积(PLD)法在小球上室温生长石榴石薄膜如Y3Fe5O12(YIG)薄膜,再用甲苯清洗除去PS小球,得到孔洞状的YIG薄膜,随后退火使YIG薄膜结晶,将样品置于HF溶液中选择性刻蚀SiO2,使YIG悬空于Si基底上,用PDMS印章取下悬空的YIG薄膜,再把YIG薄膜印制到Si基底上实现YIG薄膜在硅基底上的低温集成。
具体包括以下步骤:
步骤1:采用化学自组装法在SiO2/Si基底上六角密排直径为0.5μm~1.2μm的PS小球。
步骤2:将步骤1中六角密排的PS小球置于加热板上烘干,再用氧等离子体轰击步骤2中的PS小球,使PS小球的直径缩小为0.2~0.8μm。
步骤3:采用脉冲激光沉积(PLD)法在步骤2所得的PS小球上室温沉积石榴石薄膜,如YIG。
步骤4:清洗步骤3中所得的样品,去除PS小球,便在SiO2/Si基底上获得孔洞状(孔洞直径为0.2~0.8μm,孔与孔之间的中心间距为0.5μm~1.2μm)的石榴石薄膜。
步骤5:将步骤4所得的孔洞状的石榴石薄膜退火使其结晶。
步骤6:刻蚀掉SiO2牺牲层,并且保留需要转印的石榴石薄膜,使石榴石薄膜悬空于Si衬底上。由于步骤4我们对石榴石薄膜完成了孔洞状结构的制备,在本步骤中,刻蚀速度将会极大提高,以至于刻蚀液刻蚀时对石榴石薄膜的影响极大减弱。
步骤7:用PDMS印章贴合于Si基底上的石榴石薄膜表面,通过范德瓦尔斯力作用,取下悬空的石榴石薄膜,再把石榴石薄膜印制到Si基底上,即完成在硅上低温集成石榴石薄膜。
进一步的,所述步骤6中的刻蚀具体为:对于SiO2/Si基底,SiO2作为牺牲层,使用去离子水稀释后的HF溶液(体积比HF:H2O=1:5~1:40)对SiO2牺牲层进行选择性刻蚀。
本发明中,利用化学自组装法在SiO2/Si基底上六角密排直径为0.5μm~1.2μm的PS小球,再用氧等离子体轰击PS小球使小球直径缩小,用脉冲激光沉积(PLD)法在室温下将磁光石榴石薄膜沉积到氧等离子体轰击后的PS小球上,用甲苯清洗PS小球使PS小球及其上的石榴石薄膜脱落,使得在SiO2/Si基底上留下孔洞状的石榴石薄膜。最后将石榴石薄膜置于HF溶液中刻蚀SiO2牺牲层时,HF进入孔洞,增大了HF与SiO2的接触面积,使得刻蚀速率大大提高,减弱了石榴石被HF腐蚀的程度。刻蚀完全后,用PDMS印章取下悬空的石榴石薄膜,再把石榴石薄膜印制到硅基底上,实现了石榴石薄膜在硅基底上的低温集成。
综上所述,本发明提供了一种基于转移打印在硅上低温集成石榴石薄膜的方法,解决了石榴石薄膜制备时存在热预算高和无法与半导体工艺兼容的问题,且制备的石榴石薄膜被腐蚀程度和破裂程度大大降低。
附图说明
图1.实验流程图;
图2.孔洞状结构YIG薄膜光学显微镜图;
图3.转移到PDMS印章上的孔洞状结构YIG薄膜光学显微镜图;
图4.转移到Si基底上的孔洞状结构YIG薄膜光学显微镜图。
具体实施方式
下面结合附图和实施例对本发明作进一步阐述。
如附图1所示,按照此流程图在硅上实现石榴石薄膜的低温集成。
实施例:
步骤1:采用化学自组装法在SiO2/Si基底上采用六角密排的形式排列直径为1μm的PS小球。
步骤2:将步骤1中六角密排形式的PS小球置于加热板上,104℃下加热20s烘干PS小球;然后再用氧等离子体轰击步骤2中的小球,使小球的直径缩小为0.5μm。
步骤3:采用脉冲激光沉积(PLD)法在步骤2最终制得的PS小球上室温沉积厚度为80nm的YIG薄膜,靶基距为5.5cm,激光频率为10Hz,氧分压为0.67Pa。
步骤4:用甲苯、酒精、去离子水依次超声清洗步骤3中所得的样品,去除其中的PS小球,便在SiO2/Si基底上获得孔洞结构的YIG薄膜。
步骤5:将步骤4所得的孔洞结构的YIG薄膜置于快速退火炉中进行退火使非晶YIG结晶,氧气压保持在2Torr,升温时间设置为50s,使样品从室温升温到850℃,在850℃保温5min,然后自然冷却至室温。
步骤6:通过刻蚀液的选择性刻蚀,去掉需要刻蚀掉的SiO2牺牲层,并且保留需要转印的YIG薄膜,使YIG薄膜悬空于Si衬底上。对于SiO2/Si基底,SiO2作为牺牲层,使用去离子水稀释后的HF溶液(体积比HF:H2O=1:10)对SiO2牺牲层进行选择性刻蚀。
步骤7:用PDMS印章,贴合于Si基底上的YIG薄膜表面,通过范德瓦尔斯力作用,取下悬空的YIG薄膜,再把YIG薄膜印制到Si基底上。
图2是去除六角密排的PS小球后孔洞状YIG薄膜的光学显微镜图,从图中可以看出,小孔均匀,且孔洞直径为0.5μm,孔与孔之间的中心间距为1μm。
图3是从步骤7中转移到PDMS印章上的孔洞状YIG薄膜的光学显微镜图。孔洞状的YIG薄膜形状并未发生变化,孔洞直径与孔间距与图2中保持一致。
图4是步骤7中转移到Si基底上的孔洞状YIG薄膜的光学显微镜图。孔洞状的YIG薄膜形状并未发生变化,孔洞直径与孔间距与图2中保持一致,且转移到Si基底上的YIG薄膜没有被刻蚀液严重腐蚀,无明显破裂情况。

Claims (2)

1.一种基于转移打印在硅上低温集成石榴石薄膜的方法,具体包括以下步骤:
步骤1:采用化学自组装法在SiO2/Si基底上六角密排直径为0.5μm~1.2μm的PS小球;
步骤2:将步骤1中六角密排的PS小球置于加热板上烘干,再用氧等离子体轰击步骤2中的PS小球,使PS小球的直径缩小为0.2~0.8μm;
步骤3:采用脉冲激光沉积PLD法在步骤2所得的PS小球上室温沉积石榴石薄膜;
步骤4:清洗步骤3中所得的样品,去除PS小球,即可在SiO2/Si基底上获得孔洞状的石榴石薄膜,孔洞直径为0.2~0.8μm,孔与孔之间的中心间距为0.5μm~1.2μm;
步骤5:将步骤4所得的孔洞状的石榴石薄膜退火使其结晶;
步骤6:刻蚀掉SiO2牺牲层,并且保留需要转印的石榴石薄膜,使石榴石薄膜悬空于Si衬底上;
步骤7:用PDMS印章贴合于Si基底上的石榴石薄膜表面,通过范德瓦尔斯力作用,取下悬空的石榴石薄膜,再把石榴石薄膜印制到Si基底上,即完成在硅上低温集成石榴石薄膜。
2.如权利要求1所述基于转移打印在硅上低温集成石榴石薄膜的方法,其特征在于:
所述步骤6中的刻蚀具体为:对于SiO2/Si基底,SiO2作为牺牲层,使用去离子水稀释后的HF溶液对SiO2牺牲层进行选择性刻蚀,其中体积比为HF:H2O=1:5~1:40。
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