금속 산화물 반도체(CMOS)의 지속적인 downscaling로 인해 capacitor층의 물리적인 두께가 한계치에 도달해있다. 충분한 물리적인 두께를 확보하기 위해 SiO2(k=3.9)보다 더 높은 유전상수를 갖는 물질의 도입이 필요하다. 이런 필요성에 따라 다양한 물질들이 개발되고 있는데 ZrO2와 HfO2가 high-k ...
금속 산화물 반도체(CMOS)의 지속적인 downscaling로 인해 capacitor층의 물리적인 두께가 한계치에 도달해있다. 충분한 물리적인 두께를 확보하기 위해 SiO2(k=3.9)보다 더 높은 유전상수를 갖는 물질의 도입이 필요하다. 이런 필요성에 따라 다양한 물질들이 개발되고 있는데 ZrO2와 HfO2가 high-k 유전체의 후보로 고려되고 있다. 이 논문은 Atomic Layer Deposition (ALD) 를 이용하여 high-k 물질인 ZrO2와 HfO2 박막에 Ga doping을 하여 유전상수를 증가시키는 연구를 하였다. ALD를 이용하여 증착된 Zr1-xGaxOy 및 Hf1-xGaxOy의 박막은 결정화도를 Grazing Incidence X-ray Diffraction (GI-XRD)를 통해 분석하였고, Ga의 concentration은 X-ray Photoelectron Spectroscopy (XPS)를 이용하여 분석하였다. 또한 전기적 분석을 진행하기 위해 Capacitance-Voltage measurement (C-V)와 Current-Voltage measurement (I-V)를 측정 하여 비교 하였다. Ga2O3의 조성에 따른 유전 특성 변화를 확인 하기 위해 ZrO2 또는 HfO2와 Ga2O3의 cycle ratio를 달리하여 박막을 증착하였다. 그리고 열처리의 영향을 확인하기 위해 Furance와 Rapid Thermal Process(RTP)를 이용하여 후속 열공정을 시행하여 결정성의 변화를 확인하고, 그에 따른 유전 특성을 확인하였다. 이 과정을 통해 측정한 결과, Zr1-xGaxOy 박막은Ga 함량 10 % 에서 annealing 후에, Hf1-xGaxOy 박막은 Ga 함량 12.5 %에서 annealing 후 tetragonal phase가 가장 많이 나타나 가장 높은 유전상수를 나타내는 것을 확인하였다.
금속 산화물 반도체(CMOS)의 지속적인 downscaling로 인해 capacitor층의 물리적인 두께가 한계치에 도달해있다. 충분한 물리적인 두께를 확보하기 위해 SiO2(k=3.9)보다 더 높은 유전상수를 갖는 물질의 도입이 필요하다. 이런 필요성에 따라 다양한 물질들이 개발되고 있는데 ZrO2와 HfO2가 high-k 유전체의 후보로 고려되고 있다. 이 논문은 Atomic Layer Deposition (ALD) 를 이용하여 high-k 물질인 ZrO2와 HfO2 박막에 Ga doping을 하여 유전상수를 증가시키는 연구를 하였다. ALD를 이용하여 증착된 Zr1-xGaxOy 및 Hf1-xGaxOy의 박막은 결정화도를 Grazing Incidence X-ray Diffraction (GI-XRD)를 통해 분석하였고, Ga의 concentration은 X-ray Photoelectron Spectroscopy (XPS)를 이용하여 분석하였다. 또한 전기적 분석을 진행하기 위해 Capacitance-Voltage measurement (C-V)와 Current-Voltage measurement (I-V)를 측정 하여 비교 하였다. Ga2O3의 조성에 따른 유전 특성 변화를 확인 하기 위해 ZrO2 또는 HfO2와 Ga2O3의 cycle ratio를 달리하여 박막을 증착하였다. 그리고 열처리의 영향을 확인하기 위해 Furance와 Rapid Thermal Process(RTP)를 이용하여 후속 열공정을 시행하여 결정성의 변화를 확인하고, 그에 따른 유전 특성을 확인하였다. 이 과정을 통해 측정한 결과, Zr1-xGaxOy 박막은Ga 함량 10 % 에서 annealing 후에, Hf1-xGaxOy 박막은 Ga 함량 12.5 %에서 annealing 후 tetragonal phase가 가장 많이 나타나 가장 높은 유전상수를 나타내는 것을 확인하였다.
As shrinkage of minimum feature size of DRAM, physical thickness of DRAM capacitors approach their limits. To obtain sufficient physical thickness and capacitance, invitation of high-k materials which have high dielectric constant and band gap is needed. Among various materials, ZrO2 and HfO2 is con...
As shrinkage of minimum feature size of DRAM, physical thickness of DRAM capacitors approach their limits. To obtain sufficient physical thickness and capacitance, invitation of high-k materials which have high dielectric constant and band gap is needed. Among various materials, ZrO2 and HfO2 is considered as promising candidate as a high-k dielectrics because of its wide band gap and high dielectric constant in tetragonal phase. Dielectric constant of both ZrO2 and HfO2 is depend on crystal structure. Tetragonal ZrO2 have the highest dielectric constant among ZrO2 phases. Also, tetragonal HfO2 have the highest dielectric constant among HfO2 phases. Undersize trivalent dopants such as Ga3+ are effective for the stabilization of tetragonal phases of ZrO2 and HfO2 at room temperature. The objective of this paper is increase dielectric constant of ZrO2 and HfO2 films by adding Ga3+ dopant. Atomic Layer Deposition is used to deposit thin films. Furnace is used to crystallize and confirm thermal stability of thin films. Crystal structure of Zr1-xGaxOy, Hf1-xGaxOy have been analyzed using Grazing Incidence X-ray Diffraction (GI-XRD). Also, electrical properties have been measure by capacitor-voltage measurement, current-voltage measurement, and polarization-voltage measurement. To determine the dependence by Ga concentration, Ga concentration is controlled 0 to 50 % by varying the cycle ratio of Ga2O3 and ZrO2. Zr1-xGaxOy films form tetragonal phase at Ga concentration 0 to 14%. Amorphous phases are formed with increasing Ga concentration above 17%. Highest dielectric constant 32.9 have been appeared at Ga concentration 10%, after 450oC, 30min furnace annealing. Keyword : ALD, DRAM capacitor, Dielectric constant, HfO2, ZrO2, Doping, Phase stabilization Same procedure progressed in Hf1-xGaxOy thin films, Ga concentration of Hf1-xGaxOy thin films are varied 0 to 46%. Hf1-xGaxOy thin films crystallized at only pure HfO2 before annealing. Both monoclinic and tetragonal phase appears in that condition. After annealing, tetragonal phase increases with increasing Ga concentrations between 0 to 12.5 %. Amorphous phases are formed with increasing Ga concentration above 18.4 %. Above all these conditions, highest dielectric constant 27.5 have been appeared at Ga concentration 12.5% after annealing because of its tetragonal phases. And also in Ga concentration x=9.1%, 12.5% condition which stabilized tetragonal phases shown in previous experiment, orthorhombic phases were obtained after rapid thermal annealing in N2 condition for 20 sec 600oC with TiN capping. Orthorhombic phases and ferroelectricity were not observed in as-doped HfO2 films. A maximum Pr value 16.1 μC/cm2 was shown in Ga concentration 9.1 %. Dielectric constant changes dominantly with phase transformation, and also smaller influence compare with phase transformation, volume change influences in dielectric constant. Pure ZrO2 thin films formed tetragonal phases without doping and annealing, therefore Ga doping influences largely in HfO2 thin films because its crystal structure have monoclinic phase at origin.
As shrinkage of minimum feature size of DRAM, physical thickness of DRAM capacitors approach their limits. To obtain sufficient physical thickness and capacitance, invitation of high-k materials which have high dielectric constant and band gap is needed. Among various materials, ZrO2 and HfO2 is considered as promising candidate as a high-k dielectrics because of its wide band gap and high dielectric constant in tetragonal phase. Dielectric constant of both ZrO2 and HfO2 is depend on crystal structure. Tetragonal ZrO2 have the highest dielectric constant among ZrO2 phases. Also, tetragonal HfO2 have the highest dielectric constant among HfO2 phases. Undersize trivalent dopants such as Ga3+ are effective for the stabilization of tetragonal phases of ZrO2 and HfO2 at room temperature. The objective of this paper is increase dielectric constant of ZrO2 and HfO2 films by adding Ga3+ dopant. Atomic Layer Deposition is used to deposit thin films. Furnace is used to crystallize and confirm thermal stability of thin films. Crystal structure of Zr1-xGaxOy, Hf1-xGaxOy have been analyzed using Grazing Incidence X-ray Diffraction (GI-XRD). Also, electrical properties have been measure by capacitor-voltage measurement, current-voltage measurement, and polarization-voltage measurement. To determine the dependence by Ga concentration, Ga concentration is controlled 0 to 50 % by varying the cycle ratio of Ga2O3 and ZrO2. Zr1-xGaxOy films form tetragonal phase at Ga concentration 0 to 14%. Amorphous phases are formed with increasing Ga concentration above 17%. Highest dielectric constant 32.9 have been appeared at Ga concentration 10%, after 450oC, 30min furnace annealing. Keyword : ALD, DRAM capacitor, Dielectric constant, HfO2, ZrO2, Doping, Phase stabilization Same procedure progressed in Hf1-xGaxOy thin films, Ga concentration of Hf1-xGaxOy thin films are varied 0 to 46%. Hf1-xGaxOy thin films crystallized at only pure HfO2 before annealing. Both monoclinic and tetragonal phase appears in that condition. After annealing, tetragonal phase increases with increasing Ga concentrations between 0 to 12.5 %. Amorphous phases are formed with increasing Ga concentration above 18.4 %. Above all these conditions, highest dielectric constant 27.5 have been appeared at Ga concentration 12.5% after annealing because of its tetragonal phases. And also in Ga concentration x=9.1%, 12.5% condition which stabilized tetragonal phases shown in previous experiment, orthorhombic phases were obtained after rapid thermal annealing in N2 condition for 20 sec 600oC with TiN capping. Orthorhombic phases and ferroelectricity were not observed in as-doped HfO2 films. A maximum Pr value 16.1 μC/cm2 was shown in Ga concentration 9.1 %. Dielectric constant changes dominantly with phase transformation, and also smaller influence compare with phase transformation, volume change influences in dielectric constant. Pure ZrO2 thin films formed tetragonal phases without doping and annealing, therefore Ga doping influences largely in HfO2 thin films because its crystal structure have monoclinic phase at origin.
주제어
#ALD DRAM capacitor dielectric constant HfO2 ZrO2 doping phase stabilization
학위논문 정보
저자
최지원
학위수여기관
연세대학교 대학원
학위구분
국내석사
학과
신소재공학과
지도교수
손현철
발행연도
2017
총페이지
xii, 109장
키워드
ALD DRAM capacitor dielectric constant HfO2 ZrO2 doping phase stabilization
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