1990년대 이후부터 지금까지 Cu는 배선 소재로써 사용되어왔다. 그러나 반도체 소자의 고집적화에 따라 배선의 선 폭이 감소하게 되었고, 금속 배선에 가해지는 전기적, 기계적 응력이 급속도로 증가하게 되었다. 따라서 배선에 가해지는 고 전류밀도 하에, Cu 원자 이동에 의해 발생하는 electromigration(EM) 문제, 공정 시 금속 배선에 유발되는 stress로 인해 생기는 배선의 stress migration(SM) 문제, 배선 과 유전체 사이의 barrier를 뚫고 Cu 원자가 diffusion하는 등의 신뢰성 문제가 발 생하고 있다. 이에 따라 Cu 전극을 대체할 수 있는 새로운 물질 개발이 필요하다. 차세대 배선 전극 용 소재로는 size effect에 둔감하며, 신뢰성 측면에서 우수한 특성을 갖는 물질이 필요하다. Scaling에 따른 비저항 증가 요인은 electron의 surface scattering과 grain boundary scattering이 존재한다. 특히 이 중에서도 grain boundary scattering 현상을 감소시키기 위해서는 mean free path(MFP)가 짧고 bulk resistivity가 낮아야 하며, 다시 말해 ρ0 x λ 이 작은 값을 갖는 물질 선정이 필 수적이다. 그러나 MAX phase 등 2차원으로 conduction이 되는 소재의 경우, ρ0 x λ 값으로 만 비저항 거동을 설명하는 데에 한계가 존재하기 때문에 ρ0 x λ 값 외에 rfilm 이라 는 새로운 파라미터를 도입하여 anisotropic 소재의 특성을 고려해, 비저항 거동을 예상하는 것이 필요하다. 본 연구에서는 우수한 rfilm 특성을 갖는 Ni-based intermetallic compound 중, NiCo 물질을 모델 시스템으로 사용하여 sputter로 박막 공정을 개발하고 두께에 따른 비저항 size effect 특성을 확인하였다. 특히, 결정 구조 제어와 결정성 향상을 위해 NixCo1-x seed layer를 도입하여 HCP 구조의 Ni0.4Co0.6 박막을 구현하였으며 그 결과, 높은 결정성을 갖는 epitaxial Ni0.4Co0.6 박막을 구현할 수 있었다. 이후, Ni0.4Co0.6 박막 두께가 감소함에 따른 비저항 특성을 확인하기 위해 박막 두께를 7nm까지 감소시켜 비저항 추이를 확인한 결과, 14.3μΩ·cm까지 확보하였다. 이는 bulk 비저항 대비 약 1.2배 정도로 증가한 결과로, 우수 한 size effect 특성을 확인할 수 있다. NiCo 물질을 실제 박막으로 구현한 것은 처음이며, 배선 소재로 연구된 바가 없는 새로운 소재라는 점과, TiN이나 Cu 대비 우수한 size effect 특성을 갖는 물질을 실험적으로 처음 구현한 결과이기 때문에 본 연구 결과에 큰 의의가 있다.|Cu has been used as an interconnect material since the 1990s. However, with the high integration of semiconductor devices, the line width of the wiring has decreased, and the electrical and mechanical stress applied to the copper interconnect has rapidly increased. _x000D_
<br>Therefore, under the high current density applied to the interconnect, there are Reliability problems, such as electromigration (EM) problems caused by Cu atom movement, stress migration (SM) problems caused by stress induced in the metal wiring during the process, and the problem of Cu atoms diffusing through the barrier that exists between wiring and dielectric are occurring._x000D_
<br>Accordingly, there is a need to develop new materials that can replace Cu electrodes. Materials for next-generation interconnect electrodes are required to be insensitive to size effects and have excellent reliability characteristics. Factors that increase resistivity due to scaling include surface scattering and grain boundary scattering of electrons. In particular, in order to reduce the grain boundary scattering phenomenon, the mean free path (MFP) must be short and the bulk resistivity must be low. In other words, it is essential to select a material with a small value of ρ0 x λ. However, in the case of materials with two-dimensional conduction, such as the MAX phase, there is a limit to explaining the resistivity behavior only with the ρ0 x λ value, so a new parameter called rfilm must be introduced in addition to the ρ0 x λ to predict the resistivity behavior about anisotropic material._x000D_
<br>In this study, among Ni-based intermetallic compounds with excellent rfilmproperties, NiCo material was used as a model system to develop a thin film using sputter deposition and confirm the resistivity size effect characteristics according to thickness decrease._x000D_
<br>In particular, to control the crystal structure and improve crystallinity, a NixCo1-x seed layer was introduced to implement a Ni0.4Co0.6 thin film with an HCP structure. As a result, an epitaxial Ni0.4Co0.6 thin film with high crystallinity was achieved._x000D_
<br>Afterwards, in order to check the resistivity characteristics as the thin film thickness decreases, the thin film thickness was reduced to 7nm and the resistivity trend was checked, and a value of 14.3μΩ·cm was obtained.This is a result of an increase of approximately 1.2 times compared to the bulk resistivity, confirming excellent size effect characteristics._x000D_
<br>This is the first time that NiCo material has been implemented as an actual thin film, it is a new material that has not been studied as a interconnect material. Furthermore, it is the first experimental implementation of a material with superior size effect characteristics compared to TiN or Cu. Thus the result of this study is great significance.
Alternative Abstract
Cu has been used as an interconnect material since the 1990s. However, with the high integration of semiconductor devices, the line width of the wiring has decreased, and the electrical and mechanical stress applied to the copper interconnect has rapidly increased. _x000D_
<br>Therefore, under the high current density applied to the interconnect, there are Reliability problems, such as electromigration (EM) problems caused by Cu atom movement, stress migration (SM) problems caused by stress induced in the metal wiring during the process, and the problem of Cu atoms diffusing through the barrier that exists between wiring and dielectric are occurring._x000D_
<br>Accordingly, there is a need to develop new materials that can replace Cu electrodes. Materials for next-generation interconnect electrodes are required to be insensitive to size effects and have excellent reliability characteristics. Factors that increase resistivity due to scaling include surface scattering and grain boundary scattering of electrons. In particular, in order to reduce the grain boundary scattering phenomenon, the mean free path (MFP) must be short and the bulk resistivity must be low. In other words, it is essential to select a material with a small value of ρ0 x λ. However, in the case of materials with two-dimensional conduction, such as the MAX phase, there is a limit to explaining the resistivity behavior only with the ρ0 x λ value, so a new parameter called rfilm must be introduced in addition to the ρ0 x λ to predict the resistivity behavior about anisotropic material._x000D_
<br>In this study, among Ni-based intermetallic compounds with excellent rfilmproperties, NiCo material was used as a model system to develop a thin film using sputter deposition and confirm the resistivity size effect characteristics according to thickness decrease._x000D_
<br>In particular, to control the crystal structure and improve crystallinity, a NixCo1-x seed layer was introduced to implement a Ni0.4Co0.6 thin film with an HCP structure. As a result, an epitaxial Ni0.4Co0.6 thin film with high crystallinity was achieved._x000D_
<br>Afterwards, in order to check the resistivity characteristics as the thin film thickness decreases, the thin film thickness was reduced to 7nm and the resistivity trend was checked, and a value of 14.3μΩ·cm was obtained.This is a result of an increase of approximately 1.2 times compared to the bulk resistivity, confirming excellent size effect characteristics._x000D_
<br>This is the first time that NiCo material has been implemented as an actual thin film, it is a new material that has not been studied as a interconnect material. Furthermore, it is the first experimental implementation of a material with superior size effect characteristics compared to TiN or Cu. Thus the result of this study is great significance.
