LED用图形化蓝宝石衬底的干法刻蚀工艺

近年来,图形化蓝宝石衬底(PSS)作为GaN基LED外延衬底材料被广泛应用。采用感应耦合等离子体(ICP)技术对涂覆有光刻胶阵列图案的蓝宝石衬底进行刻蚀。通过研究及优化不同ICP刻蚀工艺参数对刻蚀速率和选择比的影响,分别成功制备出蒙古包形和圆锥形图形化蓝宝石衬底片,并在其表面完成InGaN/GaN多量子阱外延及芯片工艺。借助光致发光和电致发光等手段测试其LED器件的光电学性能。实验结果发现圆锥形的图形化蓝宝石衬底拥有更强的光功率和更窄的半峰宽,说明这种形貌的衬底在GaN外延时有效减少了晶格失配造成的缺陷,提高了晶体质量,从而更有效地增加LED出光效率。     

Cl2基气体感应耦合等离子体刻蚀GaN的工艺

采用Cl2/He对GaN基片进行感应耦合等离子体刻蚀,并比较了相同条件下使用Cl2/He,Cl2/Ar对GaN基片进行刻蚀的优劣.实验中通过改变ICP功率、直流自偏压、气体总流量和气体组分等方式,讨论了这些因素对刻蚀速率和刻蚀后表面粗糙度的影响.实验结果表明,用Cl2/He气体刻蚀GaN材料可以获得较高的刻蚀速率,最高可达420nm/min.同时刻蚀后GaN材料的表面形貌也较为平整,均方根粗糙度(RMS)可达1nm以下.SEM图像显示刻蚀后表面光洁,刻蚀端面陡直.最后比较了相同条件下使用Cl2/He,Cl2/Ar刻蚀GaN基片的刻蚀速率、表面形貌,以及制作n型电极后的比接触电阻.     

Cl2基气体感应耦合等离子体刻蚀GaN的工艺

采用Cl2/He对GaN基片进行感应耦合等离子体刻蚀,并比较了相同条件下使用Cl2/He,Cl2/Ar对GaN基片进行刻蚀的优劣.实验中通过改变ICP功率、直流自偏压、气体总流量和气体组分等方式,讨论了这些因素对刻蚀速率和刻蚀后表面粗糙度的影响.实验结果表明,用Cl2/He气体刻蚀GaN材料可以获得较高的刻蚀速率,最高可达420nm/min.同时刻蚀后GaN材料的表面形貌也较为平整,均方根粗糙度(RMS)可达1nm以下.SEM图像显示刻蚀后表面光洁,刻蚀端面陡直.最后比较了相同条件下使用Cl2/He,Cl2/Ar刻蚀GaN基片的刻蚀速率、表面形貌,以及制作n型电极后的比接触电阻.     

ICP刻蚀p-GaN表面微结构GaN基蓝光LED

采用基于Cl2/Ar/BCl3气体的感应耦合等离子体(ICP)刻蚀技术制作了p-GaN表面具有直径3 μm、周期6 μm的二维圆孔微结构GaN基蓝光LED,研究了刻蚀深度对光荧光(PL)和发光二极管(LED)光电特性的影响.结果表明,刻蚀深度为25 nm的表面微结构,与传统平面结构相比,其PL增强了42.8%;而采用ITO作为透明电极的LED,在20 mA注入电流下,正面出光增强了38%、背面出光增强了10.6%,同时前向电压降低了0.6 V,反向漏电流基本不变.     

干法刻蚀InSb时Ar气含量的选取

感应耦合等离子体(ICP)刻蚀技术是目前国际制备InSb台面结型焦平面阵列技术的主流技术之一。文章研究采用ICP刻蚀技术,以CH4/H2/Ar刻蚀气体体系对InSb材料进行干法刻蚀时刻蚀气体体系中Ar气体积组分对材料刻蚀形貌及器件性能的影响。实验方案设置为在控制其他实验变量相同的情况下设置不同Ar气体积分数的刻蚀气体体系对InSb材料进行台面蚀刻,通过扫描电子显微镜(SEM)、激光共聚焦显微镜考察台面刻蚀形貌,通过I-V测试得到的器件性能结果考察刻蚀损伤情况。从实验结果得到,Ar体积占据总气体体积的30%～35%时台面刻蚀形貌良好,表面损伤轻,器件性能良好,刻蚀工艺满足要求。     

ICP刻蚀对光刻胶掩模及刻蚀图形侧壁的影响

采用AZ1500光刻胶作为掩模对GaAs和InP进行ICP刻蚀,研究了刻蚀参数对光刻胶掩模及刻蚀图形侧壁的影响。结果表明,光刻胶的碳化变性与等离子体的轰击相关,压强、ICP功率和RF功率的增加以及Cl2比例的减小都会加速光刻胶的碳化变性,Cl2/Ar比Cl2/BCl3更易使光刻胶发生变性。对于GaAs样品刻蚀,刻蚀气体中Cl2含量越高,刻蚀图形侧壁的横向刻蚀越严重。Cl2/BCl3对GaAs的刻蚀速率比Cl2/Ar慢,但刻蚀后样品的表面粗糙度比Cl2/Ar小。刻蚀InP时的刻蚀速率比GaAs样品慢,且存在图形侧壁倾斜现象。该工作有助于推动在器件制备工艺中以光刻胶作为掩模进行ICP刻蚀,从而提高器件制备效率。     

Cl_2/BCl_3ICP刻蚀GaN基LED的规律研究

研究了用Cl2/BCl3刻蚀GaN基LED中,工艺参数对GaN刻蚀速率、刻蚀侧壁和GaN与SiO2刻蚀选择比的影响。研究结果表明,刻蚀速率随着ICP功率和压强的增大先增大继而减小,随RF功率的增大单调增大;刻蚀选择比随ICP功率增大单调减小,随压强增大而增大。还研究了刻蚀速率和选择比与气体比例变化的关系。刻蚀SEM图表明,压强和RF功率增大会使刻蚀垂直度增大。     

Cl2/H2刻蚀优化及其在1.55μDFB激光器制作中的应用

采用特别设计的InGaAsP/InP多量子阱结构(MQW),研究了Cl2/H2电感耦合等离子体(ICP)刻蚀损伤,优化了低损伤ICP刻蚀的关键工艺参数,得到了一种低损伤、形貌良好的Bragg光栅的制作方法.结合优化的InP材料金属有机物化学气相沉积(MOCVD)外延生长工艺,制作出1.55μm分布反馈(DFB)激光器,端面镀膜前其阈值电流和斜率效率分别为15 mA和0.3 mW/mA,边模抑制比大于45 dB.寿命加速老化实验结果显示,该器件40℃的中值寿命超过2×106 h,表明了本文ICP光栅刻蚀工艺的可靠性.     

GaN/SiO_2刻蚀选择比的研究

在干法刻蚀GaN时使用SiO2作为掩蔽物,为了在较快的GaN刻蚀速率下获得良好的GaN/SiO2刻蚀选择比,使用电感耦合等离子刻蚀机(ICP),运用Cl2和Ar作为刻蚀气体,改变ICP功率、直流自偏压、气体总流量、气体组分等工艺条件,并讨论了这些因素对GaN/SiO2刻蚀选择比以及对GaN刻蚀速率的影响。实验结果获得了GaN在刻蚀速率为165nm/min时的GaN/SiO2选择比为8∶1。设备验收时GaN刻蚀速率为70nm/min,GaN/SiO2选择比为3.5∶1,可以应用于实际生产。     

纳米柱InGaN/GaN多量子阱的干法刻蚀制备技术

纳米柱GaN基多量子阱(MQW)拥有量子尺寸效应以及应变释放等特性,对于提高GaN基发光二极管(LED)的发光效率具有重要意义.采用快速热退火(RTA)形成的自组装Ni纳米颗粒作为刻蚀掩膜,利用电感耦合等离子体反应离子刻蚀(ICP-RIE)制备纳米柱InGaN/GaN MQW.通过改变RTA温度发现在800℃以上才能有效形成Ni纳米颗粒掩膜.不同的ICP和射频(RF)功率条件下制备的纳米柱MQW光致发光强度相比于相同结构的平面MQW会发生显著变化.通过优化ICP-RIE的刻蚀条件,可以获得发光强度显著提高的纳米柱MQW结构.同时,纳米柱MQW中压电极化场的减弱会形成光致发光峰位蓝移.     

InAs/GaSb II类超晶格红外焦平面台面的 ICP 刻蚀研究

本文报道了采用Cl2/N2电感耦合等离子（ICP）组合体刻蚀工艺在InAs/GaSb II类超晶格红外焦平面台面加工过程中的研究结果,实验采用分子束外延技术在GaSb衬底上生长的PIN型超晶格材料。结果表明,气体流量比例直接对刻蚀速率和刻蚀形貌产生影响,氯气含量越高,刻蚀速率越大,当氮气含量增加,刻蚀速率降低并趋于一定值。当氯气和氮气的流量比例和等离子腔体内压力等参数一定时,随着温度升高,刻蚀速率和选择比在有限范围内同时线性增大,台面的倾角趋于直角,台面轮廓层状纹理逐渐消失,但沟道内变得粗糙不平,并出现坑点。在实验研究范围内,电感耦合等离子源的ICP功率和RF功率对刻蚀结果产生的影响较小。     

Corrosion at the Grain Boundary and a Fluorine-Related Passivation Layer on Etched Al-Cu (1%) Alloy Surfaces

After etching Al-Cu alloy films using SiCl4/Cl2/He/CHF3 mixed gas plasma, the corrosion phenomenon at the grain boundary of the etched surface and a passivation layer on the etched surface with an SF6 plasma treatment subsequent to the etching were studied. In Al-Cu alloy system, corrosion occurs rapidly on the etched surface by residual chlorine atoms, and it occurs dominantly at the grain boundaries rather than the crystalline surfaces. To prevent corrosion, the SF6 gas plasma treatment subsequent to etching was carried out. The passivation layer is composed of fluorine-related compounds on the etched Al-Cu surface after the SF6 treatment, and it suppresses effectively corrosion on the surface as the SF6 treatment pressure increases. Corrosion could be suppressed successfully with the SF6 treatment at a total pressure of 300 mTorr. To investigate the reason why corrosion could be suppressed with the SF6 treatment, behaviors of chlorine and fluorine were studied by various analysis techniques. It was also found that the residual chlorine incorporated at the grain boundary of the etched surface accelerates corrosion and could not be removed after the SF6 plasma treatment.     

Improved Light Extraction of Nitride-Based Flip-Chip Light-Emitting Diodes Via Sapphire Shaping and Texturing

A novel flip-chip structure of GaN-sapphire light-emitting diodes (LEDs) was developed to improve the external quantum efficiency, where the sapphire substrate was textured and shaped with beveled sidewalls using a wet etching technique. The forward voltage of the conventional flip-chip and shaped flip-chip GaN LEDs were 2.84 and 2.85 V at 20 mA, respectively. This indicates that the GaN LED was not destroyed during the sapphire wet etching process. It was found that the output power increased from 9.3 to 14.2 mW, corresponding to about 52% increases in the external quantum efficiency. The results agree well with the simulation data that the shaped flip-chip GaN LED can provide better light extraction efficiency than that of the conventional flip-chip sample     

利用CH4/H2/Ar及Cl2高密度等离子体对InSb的高速率刻蚀研究（英文）

利用感应耦合等离子体(ICP)进行了InSb刻蚀研究。为了实现高的刻蚀速率同时保证光滑的刻蚀表面,研究中在CH4/H2/Ar气氛中引入了Cl2。研究发现,对InSb的刻蚀速率随Cl2含量及ICP功率的升高而线性增加。当Cl2含量增加到超过12%或ICP功率大于900 W时,刻蚀表面变得粗糙,而易引起刻蚀损伤的直流偏压随ICP功率的升高而降低。此现象归因于刻蚀副产物InCl3在样品表面的聚集进而妨碍均匀刻蚀反应所致。当样品温度从20℃提高到120℃,刻蚀速率及表面粗糙度无明显变化。通过试验研究,实现了对InSb的高速率、高垂直度刻蚀,刻蚀速率大于500 nm/min,对SiO2掩模刻蚀选择比大于6,刻蚀表面光洁,刻蚀垂直度可达80°。     

Plasma parameters and mechanisms of GaAs reactive plasma etching in mixtures of HCl with argon and chlorine

The plasma parameters and mechanisms of gallium arsenide (GaAs) reactive plasma etching in HCl-Ar and HCl-Cl₂ mixtures under constant-current glow discharge conditions were investigated. The mathematical simulation of plasma helped to establish that the dilution of HCl with argon or chlorine results in opposite changes in the flux densities of chlorine atoms and ions. It was shown that variation in the GaAs etching rate in the HCl-Ar mixture corresponds to a change in the density of the chlorine atomic flux density on the surface. It was suggested that the nonmonotonic dependence of the etch rate upon the HCl-Cl₂ mixture composition is caused by a change of the etching regime (its limiting stage) when the degree of coverage of the processed surface with the interaction of products varies.     

Light-output enhancement in a nitride-based light-emitting diode with 22/spl deg/ undercut sidewalls

We successfully fabricated nitride-based light-emitting diodes (LEDs) with /spl sim/22/spl deg/ undercut sidewalls. The /spl sim/22/spl deg/ etching undercut sidewalls were achieved by controllable inductively coupled plasma reactive ion etching. With a 20-mA current injection, the output powers of the LED with /spl sim/22/spl deg/ undercut sidewalls and standard LED were 5.1 and 3 mW, respectively-a factor of 1.7 times enhancement. It was found that such undercut sidewalls could enhance the probability of escaping the photons outside from the LED in the near horizontal and in-plane directions. This simple and controllable method is beneficial to fabricate brighter LEDs.     

`Flip-chip' transfer of ZnSSe/ZnSe/CdZnSe LED films

A ZnSSe/ZnSe/CdZnSe light-emitting diode (LED) film grown on GaAs by molecular beam epitaxy (MBE) has been successfully transferred from a GaAs substrate to a silicon substrate by combining both mechanical polishing and chemical wet etching techniques. The external quantum efficiency of the LED was enhanced by more than a factor of 2 via insertion of a reflector layer beneath the device structure. The device can be implemented in hybrid quasimonolithic integration. Technology applications include fabrication of LEDs with enhanced external quantum efficiency and II-VI surface emitting lasers     

无机钙钛矿白光LED及可见光通信研究进展（特邀）

在现代社会中,白光发光二极管（LED）在照明和显示背板等诸多领域都有着重要的基础性作用。为了获得具有优异性能的白光LED,首先需要获得满足白光LED发光需要的高性能的发光材料。而作为一类新兴的半导体材料,无机钙钛矿（CsPbX₃, X = Cl, Br, I）由于其具有的高发光量子产率、发光波长可调、色纯度高和稳定性好等优点,在发光应用特别是白光LED领域展现出了巨大的潜力。文中将首先分别从光致白光LED和电致白光LED两个方面出发,综述近期在基于无机钙钛矿的白光LED方面所取得的研究进展,随后分别介绍以上两个体系中改性后的无机钙钛矿发光材料与其他发光材料复合形成白光以及无机钙钛矿单组分白光的代表性成果。最后,对钙钛矿白光LED在可见光通信方面所取得的最新进展进行介绍,并且对白光LED以及可见光通信的研究发展趋势与挑战进行了总结和展望。