(A) study on the thin film deposition and inherent properties of TiCl4-based TiN, TiSix, and TiSixN using the (CH3)3CCl inhibitor

다국어 초록 (Multilingual Abstract)

Owing to the increase in demand for the shrinkage of semiconductor design rules and the advent of the three-dimensional structure of semiconductor devices, atomic layer deposition (ALD) has emerged as an attractive alternative to conventional chemical vapor deposition techniques. Although the development of precursors and characterization of ALD films have been widely studied, few studies have been conducted on the modification of ALD parameters and optimization of the ALD process. In this study, an advanced ALD titanium nitride (TiN) system was designed using a pumping and purging simulation. Based on the computational fluid dynamics (CFD) simulation results, adopted a carrier pulse purge method, where TiCl4 fed, purge N2, pulse purge N2, purge N2, NH3 fed, purge N2, pulse purge N2, and purge N2 were alternatively injected into the chamber in the ALD cycle. Compared to the conventional purge method, the carrier pulse purge method can reduce the ALD cycle time by 18.27 % and yields a high-quality (high step coverage, 98 %) TiN film with lower electrical resistivity and chlorine impurity. This carrier pulse purge method can ultimately lead to improved throughput and productivity in the semiconductor industry by reducing the ALD cycle time. Initial calculations and density functional theor (DFT) simulations were performed to investigate the possible mechanisms. The proposed approach exhibited promising results for depositing high-quality TiN thin films using the (CH3)3CCl (tert-Butyl Chloride or t-BCl) in the ALD process. The step coverage of the ALD TiN thin film was improved by the (CH3)3CCl, and Si atoms were added during TiN deposition to form a TiSixN thin film. By ALD, 4 to 8 cycles of the (CH3)3CCl/TiCl4/NH3 gas formed the TiN layer, and then one to two cycles of the SiH4/NH3 gas added Si atoms and formed the TiSixN layer. The ALD process was repeated to form a TiSixN 150 Å ((TiN) 80 Å+(SixN) 70 Å, by-layer) thin film while adjusting the amount of (CH3)3CCl and SiH4. The step coverage improved to 99.9 % compared to the conventional ALD TiN when using the (CH3)3CCl. Additionally, the effect of (CH3)3CCl was more effective at low temperatures (460 °C compared to 530 °C), and the effect of (CH3)3CCl flow rate was saturated above 300 sccm. As the amount of (CH3)3CCl increases, the growth per cycle (GPC) decreases from 0.29 Å/cycle to 0.15 Å/cycle. The addition of Si to the TiN film helps in leakage gain by increasing the difference in the work function (Φm) between the electrode and the capacitor material but may have a side effect of pillar bending due to a decrease in crystallinity and hardness. Verified that the x-ray diffraction (XRD) (200)/ (111) pattern decreased as Si increased. As a result, the optimal conditions for electrode TiSixN were confirmed as follows: 300 sccm (CH3)3CCl TiN, SiH4 10 sccm SixN combination. Furthermore, a method for forming high-quality TiSix layers by cyclic pulse chemical vapor deposition (CP CVD) using double frequency modulation was developed. The CP CVD (450 kHz + 13.56 MHz) dual method produced a high step coverage and low-chlorine impurity Ti film in this study. This developed method is superior to the conventional single LF method. The CP CVD Ti deposition created a uniform and stable TiSix layer with an ohmic contact.

국문 초록 (Abstract)

DRAM 커패시터 전극 기술은 점차 한계에 다다르고 있으며 반도체 디바이스 설계 디자인 룰의 미세화에 대한 요청과 반도체 소자의 3 차원 구조 출현으로인해, 원자층 증착(ALD)방식은 기존 화학 기상 증착(CVD) 기술의 매력적인 대안으로 부상했습니다. 새로운 전구체의 개발과 ALD thin film 의 특성화에 대하여 널리 연구되었지만, ALD 공정 파라미터의 수정과 메탈 ALD 공정용 챕버 최적화에 대한 연구는 많은 연구가 수행되지 않았습니다.
본 연구에서는 ALD 공정의 펌핑 및 퍼징 시뮬레이션을 진행하여고 퀄리티 ALD 티타늄 나이트라이드(TiN, TiSixN)증착용 시스템 챔버을 설계했습니다. CFD 시뮬레이션 결과를 바탕으로 만드어진 캐리어 펄스 퍼지 방법을 채택했으며, 이과정은 TiCl4 피딩, 퍼지 N2, 펄스 퍼지 N2, 퍼지 N2, NH3 피딩, 퍼지 N2, 펄스 퍼지 N2 및 마지막 퍼지 N2 가 ALD 사이클 방식으로 챔버에 교대로 주입되는 방법을 사용하였습니다.
기존의 퍼지 방법에 비해 캐리어 펄스 퍼지 방법은 ALD 사이클 시간을 18.27% 단축할 수 있었으며, 박막의 저항과 염소 불순물이 낮은 고품질, High stepcoverage (98%)의 TiN 필름을 증착할수 있었습니다. 이러한 캐리어 펄스 퍼지 방법은 궁극적으로 ALD 사이클 시간을 줄임으로써 반도체 웨이퍼 처리량과 시스템 생산성 향상으로 이어질 수 있습니다.
스텝 커버리지 개선을하기위한 IA ALD (Inhibitor Assisted ALD)증착 메커니즘을 조사하기 위해서 초기 계산(DOE 실험) 및 DFT 시뮬레이션이 수행되었으며, 본 논문에서 제안된 접근법은 ALD 공정에서 tert-Butyl Chloride (t-BCl, (CH3)3CCl))를 사용하여 고품질 capacitor 일렉트로드 TiN 박막을 증착하는 데 유의미한 결과를 확보하였습니다
(GPC 가 0.352 Å 에서 0.146 Å 으로 감소). 인히비터(CH3)3CCl)에 의해 ALD TiN 박막의 스텝 커버리지가 향상되었고, TiN 증착 동안 Si 원자를 추가로 첨가하여 TiSixN 박막을 증착 하였습니다. ALD TiSixN 박막은(CH3)3CCl/TiCl4/NH3 가스를 4~8 사이클이 TiN 층을 형성한 후, SiH4/NH3 가스는 1~2 사이클이 Si 원자가 첨가하여 TiSixN 층을 형성되게 하였습니다(XPS 와 SIMS 를 이용한 원소분석 결과 흡착된 (CH3)3CCl 분자는 증착막에 남아있지 않고 제거된 것으로 나타났다). 이러한 ALD 과정을 반복하여 (CH3)3CCl 및 SiH4 의 양을 조절하면서 TiSixN 150Å((TiN) 80Å+(SixN) 70Å) 박막을 형성했습니다. 스텝 커버리지는 (CH3)3CCl 을 사용할 때 기존의 ALD TiN 에 비해 99.9%으로 향상되었습니다. 또한, (CH3)3CCl 의 효과는 저온(530℃ 대비 460℃)에서 더 효과적이었고, (CH3)3CCl 유량의 효과는 300 sccm 이상에서 포화되었습니다. (CH3)3CCl 의 피딩 량이 증가함에 따라, 사이클당 성장(GPC)은 0.29 Å/cycle 에서 0.15 Å/cycle 로 감소하여 인히비터의 효과 (화학적 반응이 아닌 물리적 흡착에 의한 인히비터 역할)를 확인 할수 있었습니다.
TiN 막에 Si 을 첨가하면 일레트로드 전극과 커패시터 재료의 일함수(Φm) 차이를 증가시켜 누설전류 감소 개선에 도움이 되지만, 12wt. % 이상이 되면 과도한 결정성 및 경도의 감소로 인해 커패시터 일렉트로드의 필라 구조의 휘는 리닝 부작용이 발생할 수 있습니다. Si 이 증가함에 따라 XRD(111)/(200) 피크 비율이 감소하는 것을 확인했습니다. 그 결과 전극 TiSixN 의 최적 조건은 다음과 같이 확인되었습니다. 최적화 조건은 300 sccm ((CH3)3CCl TiN, SiH4 10 sccm) SixN 조합으로 형성된 TiSixN 막 조성은 Ti: 40 ~ 47 at. %, N: 40 ~ 45 at. %, Si: 8.9 ~ 10 at. %으로 확인되었습니다.
또한, 설계된 챔버의 확장성을 확인 하기위하여 이중 주파수 변조를 이용한 순환 펄스 화학 기상 증착법(CP CVD)에 의해 고품질의 TiSix 층을 형성하는 방법을 개발하였습니다. 본 연구에서는 CP CVD (450 kHz + 13.56 MHz) 듀얼 주파수 방법을 통해 높은 스텝 커버리지와 저염소불순물 Ti 막을 생성하여 TiSix 형성에 기여하였습니다. 이렇게 개발된 방법은 기존의 단일 LF (혹은 HF) 주파수 방법보다 컨택내부의 실리사이드 형성에 유리합니다. CP CVD Ti 증착법은 오믹 접촉을 갖는 균일하고 안정적인 TiSix 층을 생성됨을 EELS 를 통하여 확인하였습니다.

목차 (Table of Contents)

• CONTENTS.........................................................................................................................i
• List of figures....................................................................................................................vii
• List of tables......................................................................................................................xii
• Abstract.............................................................................................................................xiii
• Chapter 1. Introduction................................................................................................ 1
• 1.1. General Overview ................................................................................................... 4
• 1.1.1 Historical overview ........................................................................................ 4
• 1.1.2 ALD windows ................................................................................................ 6
• 1.2. Motivation……...…………………….…………………………………..………10
• 1.2.1 Changes in capacitor structure and breakthrough of process………………10
• 1.2.2 DRAM capacitance of the capacitor……………………………………..…13
• 1.2.3 Spherical capacitor………………...……………………………………..…13
• 1.2.4 Cylindrical capacitor……………………………………………………..…15
• 1.3. Materials Characterization for the TiCl4 and (CH3)3CCl .................................... 18
• 1.4. Dissertation Overview…………..…………………………………….………….23
• 1.5. Reference .............................................................................................................. 26
• Chapter 2. Experiment Details................................................................................... 31
• 2.1. Sample Preperation……………………………………………………………....31
• 2.2. CFD and DFT Simulation Studies ........................................................................ 35
• 2.2.1 CFD preparation ………………………………..………………….….……35
• 2.2.2 DFT preparation ........................................................................................... 37
• 2.3. Reaction Mechanism………………………………………………………....…42
• 2.3.1 ALD TiN reaction mechanism…………………………………….…….….42
• 2.3.2 ABC-type ALD TiN reaction mechanism using (CH3)3CCl inhibitor..….…47
• 2.4. Metallic System ALD and PECVD……….…………………..…..…………….51
• 2.5. Reference .............................................................................................................. 52
• Chapter 3. Characterization of TiN Layer Deposition Using a (CH3)3CCl Growth
• Inhibitor.................................................................................................... 58
• 3.1. Introduction........................................................................................................... 58
• 3.2. Experimental Details............................................................................................ .61
• 3.2.1 Preparation for chamber CFD simulation……….......................................61
• 3.2.2 Preparation of DFT simulation using the(CH3)3CCl………….…………61
• 3.3. CFD Simulation for the Reaction Chamber and Gas Flow………………………63
• 3.3.1 Simulation of chamber pumping models...................................................... 63
• i
• 3.3.2 CFD simulation of the change in the concentration of molecules................ 65
• 3.4. DFT Simulation for the (CH3)3CCl Inhibitor ...................................................... 70
• 3.4.1 Adsorption and desorption mechanism [39-41]……….……..…………70
• 3.4.2 Reaction state of (CH3)3CCl on both the TiN and SiO2 surface……..…75
• 3.4.3 Non interaction between (CH3)3CCl on both the TiN and SiO2 surface..77
• 3.4.4 Sample preparation for carrier pulse purge TiN…………..….…...……80
• 3.5. Film Characteristics for TiN.................................................................................. 82
• 3.5.1 D/R saturation condition............................................................................... 82
• 3.5.2 TiN film grows at different stage heater temperatures ................................. 85
• 3.5.3 GPC, resistivity and Cl impurity ................................................................. .88
• 3.5.4 Surface roughness and film stress.……………………….….……...…...89
• 3.5.5 Step coverage…………………………………………….…….……….96
• 3.5.6 Studied of potential for (CH3)3CCl interaction….……….…….….……99
• 3.5.7 Inhibitor-assisted atomic layer deposition reaction scheme……............105
• 3.6. Film Characteistics for Inhibitor TiN Films........................................................ 108
• 3.6.1 Sample preparation of IA ALD using the inhibitor……….…...............108
• 3.6.2 Film characterization tool……………………………………...............109
• v
• 3.6.3 Diagram of the ABC-type cycle inhibitor TiN process…………................110
• 3.6.4 D/R saturation condition………………………………….……................118
• 3.6.5 Film impurity for ALD TiN film using (CH3)3CCl………….…................123
• 3.6.6 XPS depth profile of inhibitor TiN………………………….…................124
• 3.6.7 SIMS depth profile of inhibitor TiN……………………………................127
• 3.6.8 Film conformality……………………………………….......…................130
• 3.7. Conclusions......................................................................................................... 136
• 3.8. Reference ............................................................................................................ 137
• Chapter 4. Characterization of TiSixN Layer Deposition Using (CH3)3CCl Growth
• Inhibitor.................................................................................................. 145
• 4.1. Introduction......................................................................................................... 145
• 4.2. Experimental Details........................................................................................... 148
• 4.3. Growth of ALD TiN using (CH3)3CCl Inhibitor..................................................152
• 4.3.1 Self-limiting growth and GPC………………….........................................152
• 4.4. Film Charaterics of Step Coverage, Electric resistivity, and Mechanical Properties
• of Films.............................................................................................................155
• 4.4.1 XRD spectra pattern composition and charactics for the TiN and
• TiSixN....................................................................................................................155
• v
• 4.4.2 FIB, SAED, and EELS scan analysis………………………………….......161
• 4.4.3 Film surface roughness and incubation layer………………………….......166
• 4.4.4 Cross sectional view of bottom electrode a capacitor and filled……….....169
• 4.5. Conclusions..........................................................................................................173
• 4.6 Reference.............................................................................................................174
• Chapter 5. Characterization of TiSix Layer Deposition Using a (CH3)3CCl Growth
• Inhibitor……………………………….…………..…………….….…..182
• 5.1. Introduction …………………………………………………………………….182
• 5.2. Experimental Details........................................................................................... 183
• 5.2.1 Expected vertical structure for future 3-D DRAM………………………183
• 5.3. Dual-frequency Modulation and Reaction Mechanism…………………...…... 187
• 5.3.1 The effect of variable frequency.……………………………………….…187
• 5.3.2 Preparation of TiSix thin film………………………………………..….…188
• 5.4. Film Charateistics of D/R, Electrical Resistivity, and Mechanical Properties vs.
• Different RF Frequencies.................................................................................... 189
• 5.4.1 TiSix film deposition rate and resistivity for variable RF power..................189
• 5.4.2 TiSix film formation by CP CVD……………..……………………...........194
• 5.4.3 MCFD function and diagram with FCMS………………………................197
• 5.4.4 Preparation of thin film with CP CVD……..……………………................198
• 5.4.5 Composition TiSix thickness (tTi) between the via contact bottom and top
• area…………………….………………………………………………………....199
• 5.4.6 Step coverage……………………………………...………………………201
• 5.4.7 TiSix film formation……………………….……………………................203
• 5.4.8 TEM, EELS, and AFM analysis………...………………………................206
• 5.4.9 SIMS for the profile of chlorine (Cl) impurities………………………….214
• 5.5. Conclusions........................................................................................................... 217
• 5.6 Reference.............................................................................................................218
• Chapter 6. Summary………………………………………….…………………….226
• Abstract in Korean …..…………………………………..……………………………229