On the relationships between plasma chemistry, etching kinetics and etching residues in CF₄+C₄F₈+Ar and CF₄+CH₂F₂+Ar plasmas with various CF₄/C₄F₈ and CF<s

Lee, Jaemin,Efremov, Alexander,Kwon, Kwang-Ho Elsevier 2018 Vacuum Vol.148 No.-

<P><B>Abstract</B></P> <P>In this work, we investigated how the CF<SUB>4</SUB>/C<SUB>4</SUB>F<SUB>8</SUB> and CF<SUB>4</SUB>/CH<SUB>2</SUB>F<SUB>2</SUB> mixing ratios in CF<SUB>4</SUB>+C<SUB>4</SUB>F<SUB>8</SUB>+Ar and CF<SUB>4</SUB>+CH<SUB>2</SUB>F<SUB>2</SUB>+Ar inductively coupled plasmas influence plasma parameters, densities and fluxes of plasma active species and etching characteristics (process kinetics, etching rates and selectivities, etching residues) for both Si and SiO<SUB>2</SUB>. For this purpose, we employed surface diagnostics by x-ray photoelectron spectroscopy (XPS), plasma diagnostics by Langmuir probes and 0-dimensional plasma model. It was found that the substitution of CF<SUB>4</SUB> for CH<SUB>2</SUB>F<SUB>2</SUB> causes the stronger decreases in both F atom flux and ion energy flux compared with the effect of C<SUB>4</SUB>F<SUB>8</SUB>. Accordingly, the CF<SUB>4</SUB>+CH<SUB>2</SUB>F<SUB>2</SUB>+Ar mixture provides the deeper fall of both Si and SiO<SUB>2</SUB> etching rates, leaves the higher amount of the fluorocarbon polymer on the etched surface (especially in the case of Si) and results in a bit higher SiO<SUB>2</SUB>/Si etching selectivity. It was shown also that, in both gas systems, the etching process appears in the steady-state regime. The mechanisms influencing the etching/polymerization balance were discussed based on the correlation between Si and SiO<SUB>2</SUB> etching rates with fluxes of plasma active species.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Etching characteristics and residues for Si and SiO<SUB>2</SUB> surfaces are investigated. </LI> <LI> The differences in etching rates correspond to the differences in F atom fluxes. </LI> <LI> The higher polymerization ability is connected with the lower <SUB> Γ F </SUB> <SUB> Γ p o l </SUB> . </LI> </UL> </P>

The Dry Etching Properties of ZnO Thin Film in Cl2/BCl3/Ar Plasma

우종창,김창일 한국전기전자재료학회 2010 Transactions on Electrical and Electronic Material Vol.11 No.3

The etching characteristics of zinc oxide (ZnO) were investigated, including the etch rate and the selectivity of ZnO in a Cl2/BCl3/Ar plasma. It was found that the ZnO etch rate, the RF power, and the gas pressure showed non-monotonic behaviors with an increasing Cl2 fraction in the Cl2/BCl3/Ar plasma, a gas mixture of Cl2(3 sccm)/BCl3(16 sccm)/Ar (4 sccm) resulted in a maximum ZnO etch rate of 53 nm/min and a maximum etch selectivity of 0.89 for ZnO/SiO2. We used atomic force microscopy to determine the roughness of the surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the plasmas. Due to the relatively low volatility of the by-products formed during etching with Cl2/BCl3/Ar plasma, ion bombardment and physical sputtering were required to obtain the high ZnO etch rate. The chemical states of the etched surfaces were investigated using X-ray photoelectron spectroscopy (XPS). This data suggested that the ZnO etch mechanism was due to ion enhanced chemical etching.

The Dry Etching Properties of ZnO Thin Film in Cl₂/BCl₃/Ar Plasma

Woo, Jong-Chang,Kim, Chang-Il The Korean Institute of Electrical and Electronic 2010 Transactions on Electrical and Electronic Material Vol.11 No.3

The etching characteristics of zinc oxide (ZnO) were investigated, including the etch rate and the selectivity of ZnO in a $Cl_2/BCl_3$/Ar plasma. It was found that the ZnO etch rate, the RF power, and the gas pressure showed non-monotonic behaviors with an increasing Cl2 fraction in the $Cl_2/BCl_3$/Ar plasma, a gas mixture of $Cl_2$(3 sccm)/$BCl_3$(16 sccm)/Ar (4 sccm) resulted in a maximum ZnO etch rate of 53 nm/min and a maximum etch selectivity of 0.89 for ZnO/$SiO_2$. We used atomic force microscopy to determine the roughness of the surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the plasmas. Due to the relatively low volatility of the by-products formed during etching with $Cl_2/BCl_3$/Ar plasma, ion bombardment and physical sputtering were required to obtain the high ZnO etch rate. The chemical states of the etched surfaces were investigated using X-ray photoelectron spectroscopy (XPS). This data suggested that the ZnO etch mechanism was due to ion enhanced chemical etching.

Oxidation and etching behaviors of the InAs surface in various acidic and basic chemical solutions

Na, Jihoon,Lee, Seunghyo,Lim, Sangwoo Elsevier 2017 Surface science Vol.658 No.-

<P><B>Abstract</B></P> <P>Indium arsenide (InAs) is the candidate of choice as a new channel material for application in future technologies beyond the Si–based electronic devices because it has a much higher electron mobility than silicon. In this study, the oxidation and etching behaviors of InAs (100) in various acidic and basic solutions, such as HF, HCl, H<SUB>2</SUB>SO<SUB>4</SUB>, NaOH, KOH, and NH<SUB>4</SUB>OH, were investigated. In addition, the effect of pH on the oxidation and etching reactions taking place on the InAs surface was studied using solutions with a pH ranging from 1 to 13. It was observed that the oxidation of the InAs surface was hindered in acidic solutions, which was attributed to the dissolution of the oxidized surface layer. In particular, the treatment of the InAs surface using a strongly acidic solution with a pH of less than 3 produced an oxide–free surface due to the predominant etching of the InAs surface. The addition of H<SUB>2</SUB>O<SUB>2</SUB> to the acidic solutions greatly increased the etching rate of the InAs surface, which suggests that the oxidation process is the rate–limiting step in the sequence of reactions that occur during the etching of the InAs surface in acidic solutions. The etching of InAs was suppressed in neutral solutions, which resulted in the formation of a relatively thicker oxide layer on the surface, and mild etching of the InAs surface took place in basic solutions. However, in basic solutions, the addition of H<SUB>2</SUB>O<SUB>2</SUB> did not significantly contribute to the increase of the oxidation state of the InAs surface; thus, its effect on the etching rate of InAs was smaller than in acidic solutions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oxidation and etching behaviors of InAs was investigated in acidic and basic solutions. </LI> <LI> Oxide-free InAs surface could be prepared at the pH lower than 4. </LI> <LI> In the strong bases, relatively thin InAs oxide layer was present due to a mild etching. </LI> <LI> Oxidation of InAs is a rate limiting step in the overall etching process in strong acids. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

화학적 습식 에칭을 통한 AlN와 GaN의 결함 및 표면 특성 분석

홍윤표,박재화,박철우,김현미,오동근,최봉근,이성국,심광보,Hong, Yoon Pyo,Park, Jae Hwa,Park, Cheol Woo,Kim, Hyun Mi,Oh, Dong Keun,Choi, Bong Geun,Lee, Seong Kuk,Shim, Kwang Bo 한국결정성장학회 2014 한국결정성장학회지 Vol.24 No.5

화학적 습식 에칭을 통해 AlN와 GaN의 결함 및 표면 특성을 분석했다. 화학적 습식 에칭은 단결정의 결함을 선택적으로 에칭하기 때문에 결정의 품질을 평가하는 좋은 방법으로 주목 받고 있다. AlN와 GaN의 단결정은 NaOH/KOH 용융액을 이용하여 에칭을 했으며, 에칭 후 표면 특성을 알아보기 위해 주사전자현미경(SEM)과 원자힘 현미경(AFM)을 촬영했다. 에치 핏의 깊이를 측정하여 표면에 따른 에칭 속도를 계산했다. 그 결과 AlN와 GaN 표면에는 두 개의 다른 형태에 에치 핏이 형성 되었다. (0001)면의 metal-face(Al, Ga)는 육각 추를 뒤집어 놓은 형태를 갖는 반면 N-face는 육각형 형태의 소구 모양(hillock structure)을 하고 있었다. 에칭 속도는 N-face가 metal-face(Al, Ga)보다 각 각 약 109배(AlN)와 5배 정도 빨랐다. 에칭이 진행되는 동안 에치 핏은 일정한 크기로 증가하다 서로 이웃한 에치 핏들과 합쳐지는 것으로 보여졌다. 또한 AlN와 GaN의 에칭 공정을 화학적 메커니즘을 통해 알아 보았는데, 수산화 이온($OH^-$)과 질소의 dangling bond에 영향을 받아 metal-face(Al, Ga)와 N-face가 선택적으로 에칭되는 것으로 추론되었다. We investigated defects and surface polarity in AlN and GaN by using wet chemical etching. Therefore, the effectiveness and reliability of estimating the single crystals by defect selective etching in NaOH/KOH eutectic alloy have been successfully demonstrated. High-quality AlN and GaN single crystals were etched in molten NaOH/KOH eutectic alloy. The etching characteristics and surface morphologies were carried out by scanning electron microscope (SEM) and atomic force microscope (AFM). The etch rates of AlN and GaN surface were calculated by etching depth as a function of etching time. As a result, two-types of etch pits with different sizes were revealed on AlN and GaN surface, respectively. Etching produced hexagonal pits on the metal-face (Al, Ga) (0001) plane, while hexagonal hillocks formed on the N-face. On etching rate calibration, it was found that N-face had approximately 109 and 15 times higher etch rate than the metal-face of AlN and GaN, respectively. The size of etch pits increased with an increase of the etching time and they tend to merge together with a neighbouring etch pits. Also, the chemical mechanism of each etching process was discussed. It was found that hydroxide ion ($OH^-$) and the dangling bond of nitrogen play an important role in the selective etching of the metal-face and N-face.

Tungsten Silicide Gate Etching with Very High WSix to Poly-Si Selectivity and Low WSix Etch Rate Micro-Loading in the High Density Plasma

Yong Deuk Ko,Hui-Gon Chun,Jinhan Choi 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4

As the design rule of DRAM device decreases to less than 100 nm and the aspect ratio between gate electrode and space increases dramatically (3.5~ 4), it is coming difficult to fill the spaces with insulating materials. It is also becoming more preferable to reduce the thickness of poly-Si rather than to reduce WSix film because of reducing electrical resistivity. To meet these requirements, highly selective and anisotropic etching for WSix/poly-Si has been developed by fully utilizing a high density plasma source. In this study, O₂ and N₂ gases were added to achieve high selectivity in NF₃/Cl₂ gas process. The addition of O₂ increases WSix etch rate by forming W-oxyhalides and passivates poly-Si by forming Si-O layer. On the other hand, the addition of N₂ gas decreases both poly-Si and WSix, but it forms a sidewall protection layer (WN) on WSix, achieving an isotropic etching. The role of cathode temperature was found to not only increase WSix etch rate and the WSix /poly-Si selectivity but also provides a wider process margin for the production environment. As the design rule of DRAM device decreases to less than 100 nm and the aspect ratio between gate electrode and space increases dramatically (3.5~ 4), it is coming difficult to fill the spaces with insulating materials. It is also becoming more preferable to reduce the thickness of poly-Si rather than to reduce WSix film because of reducing electrical resistivity. To meet these requirements, highly selective and anisotropic etching for WSix/poly-Si has been developed by fully utilizing a high density plasma source. In this study, O₂ and N₂ gases were added to achieve high selectivity in NF₃/Cl₂ gas process. The addition of O₂ increases WSix etch rate by forming W-oxyhalides and passivates poly-Si by forming Si-O layer. On the other hand, the addition of N₂ gas decreases both poly-Si and WSix, but it forms a sidewall protection layer (WN) on WSix, achieving an isotropic etching. The role of cathode temperature was found to not only increase WSix etch rate and the WSix /poly-Si selectivity but also provides a wider process margin for the production environment.

Ultra-low rate dry etching conditions for fabricating normally-off field effect transistors on AlGaN/GaN heterostructures

Kim, Zin-Sig,Lee, Hyung-Seok,Na, Jeho,Bae, Sung-Bum,Nam, Eunsoo,Lim, Jong-Won Elsevier 2018 Solid-state electronics Vol.140 No.-

<P><B>Abstract</B></P> <P>Enhancement-mode transistors with uniform turn-on threshold voltage (V<SUB>th</SUB>) can be achieved using low damage and low rate gate recess etching techniques. In this work, dry etching conditions for a AlGaN/GaN heterostructure with an ultra-low etching rate of 1.5 nm/min were demonstrated and we succeeded the possibility to achieve a low etch rate of an AlGaN/GaN heterostructure in a Cl<SUB>2</SUB>/BCl<SUB>3</SUB> plasma using inductively coupled plasma (ICP). The etching development was successfully implemented in the achievement of a normally-off GaN/AlGaN based transistor. The optimal recess depth was determined after fabrication of various devices with different recess depth values and with various dry etching conditions and after examining the performances of fabricated devices various conditions, and determining the dependence of recess time. The optimized etching condition resulted in low damage and smooth morphology of the etched AlGaN/GaN surfaces. Fine control of the depth of the gate region recess was achieved for the AlGaN/GaN heterostructure without any etch-stop layer, and validated for the fabrication of field effect transistors (FETs) using conventional processes. The fabricated normally-off Al<SUB>2</SUB>O<SUB>3</SUB>/AlGaN/GaN MOSFETs delivered a high positive V<SUB>th</SUB> of +5.64 V with a low off-state leakage current of ∼10<SUP>−7</SUP> A/mm and lower current collapse.</P>

High density plasma etching of YSZ thin film in halogenbased inductively coupled plasmas

최병수,박종천,서준원,류수착,이희수,류정호,조현 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.8

Yttria-stabilized zirconia (YSZ) has a good potential as a gate dielectric in various metal-oxide-semiconductor field effecttransistor (MOSFET) devices for displays and a precise and anisotropic plasma etching is required for the integration of theYSZ gate structure. High density plasma etching of YSZ thin film was performed in halogen-based inductively coupledplasmas (ICPs) and the effect of process variables such as plasma composition, ICP source power and rf chuck power on theYSZ etch characteristics was examined. Higher YSZ etch rates were obtained in chlorine-based (10BCl3/5Ar and 10Cl2/5Ar)ICP discharges because of the higher volatilities of metal chloride etch products. Maximum etch rates of 1042.5 Å/min and796 Å/min were obtained in 10BCl3/5Ar and 10CF4/5Ar ICP discharges, respectively. 10CF4/5Ar discharges were found toprovide a very smooth surface morphology while a significant surface roughening has occurred after etching at high rf chuckpower conditions in 10BCl3/5Ar discharges. The YSZ surfaces etched in 10BCl3/5Ar and 10CF4/5Ar maintained thestoichiometry and highly anisotropic features were transferred into YSZ by 10CF4/5Ar ICP etching.

Ruthenium CMP에서 Cerium Ammonium Nitrate와 알루미나 연마 입자가 연마 거동에 미치는 영향

이상호,이승호,강영재,김인권,박진구,Lee, Sang-Ho,Lee, Sung-Ho,Kang, Young-Jae,Kim, In-Kwon,Park, Jin-Goo 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.9

Cerium ammonium nitrate (CAN) and nitric acid was used an etchant and an additive for Ru etching and polishing. pH and Eh values of the CAN and nitric acid added chemical solution satisfied the Ru etching condition. The etch rate increased linearly as the concentration of CAN increased. Nitric acid added solution had the high etch rate. But micro roughness of etched surfaces was not changed before and after etching, The removal rate of Ru film was the highest in $1wt\%$ abrasive added slurry, and not increased despite the concentration of alumina abrasive increased to $5wt\%$. Even Ru film was polished by only CAN solution due to the friction. The highest removal rate of 120nm/min was obtained in 1 M nitric acid and $1wt\%$ alumina abrasive particles added slurry. The lowest micro roughness value was observed in this slurry after polishing. From the XPS analysis of etched Ru surface, oxide layer was founded on the etched Ru surface. Therefore, Ru was polished by chemical etching of CAN solution and oxide layer abrasion by abrasive particles. From the result of removal rate without abrasive particle, the etching of CAN solution is more dominant to the Ru CMP.

GaN epitaxy 층의 식각특성에 미치는 공정변수의 영향

최병수,박해리,조현,Choi, Byoung Su,Park, Hae Li,Cho, Hyun 한국결정성장학회 2016 한국결정성장학회지 Vol.26 No.4

플라즈마 조성, ICP source power, rf chuck power 등의 공정변수가 GaN epitaxy층의 식각특성에 미치는 영향을 조사하였다. $GaF_x$ 화합물 보다 더 높은 휘발성을 가지는 $GaCl_x$ 식각 생성물 형성이 가능한 $Cl_2/Ar$ 플라즈마가 $SF_6/Ar$ 플라즈마보다 더 높은 식각속도를 나타내었다. 또한, $Cl_2/Ar$ 플라즈마에서 Ar 비중이 증가함에 따라 물리적 식각 기구 활성화로 인해 식각 이방성이 향상됨을 확인하였다. 두 가지 플라즈마 조성 모두에서 ICP source power와 rf chuck power가 증가함에 따라 식각속도가 지속적으로 증가함을 확인하였고, $13Cl_2/2Ar$, 750W ICP power, 400 W rf chuck power, 10 mTorr 조건에서 최고 251.9 nm/min의 식각속도를 확보하였다. The effect of process parameters such as plasma composition, ICP (Inductively Coupled Plasma) source power and rf chuck power on the etch characteristics of GaN epitaxy layer was studied. $Cl_2/Ar$ ICP discharges showed higher etch rates than $SF_6/Ar$ discharges because of the higher volatility of $GaCl_x$ etch products than $GaF_x$ compounds. As the Ar ratio increases in the $Cl_2/Ar$ ICP discharges, the etch anisotropy was enhanced due to the improved physical component of the etching. For both plasma chemistries, the GaN etch rate increased continuously as both the ICP source power and rf chuck power increased, and a maximum etch rate of 251.9 nm/min was obtained at $13Cl_2/2Ar$, 750W ICP power, 400W rf chuck power and 10 mTorr condition.