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실험계획법을 이용한 대구경용 코발트 박막의 스퍼터 조건 최적화
정성희(Seong Hwee Cheong),송오성(Oh Sung Song) 한국자기학회 2002 韓國磁氣學會誌 Vol.12 No.6
The statistical experiment method is employed to optimize the deposition condition of Co film with DC magnetron sputtering process. The statistical treatment results showed the significance value below 0.05, low RMS error and R-sq value close to 1, which implied that our experiment and design were very reliable. We found that the sheet resistance decreased to -1.83 Ω/□ with the deposition temperature, increased to +1.17 Ω/□ with the deposition pressure, and decreased into -0.65 Ω/□ with the DC power. We also confirmed that the sheet resistance uniformity was mainly influenced by the deposition temperature as it decreased -4.04% at the temperature range of 25℃~147℃. Finally, we report that the optimum condition of Co film using our statistical method of design of experiment is the deposition temperature of 25℃, the deposition pressure of 12 mTorr, and the DC power of 1500W.
정성희,송오성,Cheong, Seong-Hwee,Song, Oh-Sung 한국재료학회 2002 한국재료학회지 Vol.12 No.11
We investigated the void formation in composite-titanium silicide($TiSi_2$) process. We varied the process conditions of polycrystalline/amorphous silicon substrate, composite $TiSi_2$ deposition temperature, and silicidation annealing temperature. We report that the main reason for void formation is the mass transport flux discrepancy of amorphous silicon substrate and titanium in composite layer. Sheet resistance in composite $TiSi_2$ without patterns is mainly affected by silicidation rapid thermal annealing (RTA) temperature. In addition, sheet resistance does not depend on the void defect density. Sheet resistance with sub-0.5 $\mu\textrm{m}$ patterns increase abnormally above $850^{\circ}C$ due to agglomeration. Our results imply that $sub-750^{\circ}C$ annealing is appropriate for sub 0.5 $\mu\textrm{m}$ composite X$sub-750_2$ process.
정성희,송오성,Cheong, Seong-Hwee,Song, Oh-Sung 한국재료학회 2003 한국재료학회지 Vol.13 No.5
The $CoSi_2$ process is widely employed in a salicide as well as an ohmic layer process. In this experiment, we investigated the characteristics of $CoSi_2$ films by combinations of I-type (TiN 100$\AA$/Co 150$\AA$), II-type(TiN 100$\AA$/Co 150$\AA$/Ti 50$\AA$), III-type(Ti 100$\AA$/Co 150$\AA$/Ti 50$\AA$), and IV-type(Ti 100$\AA$/Co 150$\AA$/Ti 100$\AA$). Sheet resistances of $CoSi_2$ show the lowest resistance with 2.9 $\Omega$/sq. in a TiN/Co condition and much higher resistances in conditions simultaneously applying Ti capping layers and Ti interlayers. Though we couldn't observe a $CoSi_2$roughness dependence on the film stacks from RMS values, Ti capping layers turned into 78∼94$\AA$ thick TiN layers of (200) preferred orientation at $N_2$ambient. In addition, Ti interlayers helped to form the epitaxial $CoSi_2$with (200) preferred orientation and ternary compounds of Co-Ti-Si. We propose that film structures of II-type and III-type may be appropriate in the salicide process and the ohmic layer process from the viewpoint of Co diffusion kinetics and the CoSi$_2$epitaxy.
통계적 실험 방법을 이용한 티타늄실리사이드의 열적안정성 연구
정성희,송오성,Cheong, Seong-Hwee,Song, Oh-Sung 한국재료학회 2003 한국재료학회지 Vol.13 No.3
A statistical experiment method was employed to investigate the window of the thermal stability of $TiSi_2$films which are popular for Ti-salicide and ohmic layers. The statistical experimental results showed that the first order term of $TiSi_2$thickness and annealing temperature was acceptable as a function of $\Delta$resistivity by 95% reliability criteria, and R-sq value implying a fit accuracy of the model also showed a high value of 93.80%. We found that $\Delta$resistivity of the $TiSi_2$film annealed at $700^{\circ}C$ for 1 hr changed from 3.35 to $0.379\mu$$\Omega$$\cdot$cm with increasing thickness from 185 to $703\AA$, and $\Delta$resistivity of the $TiSi_2$film with a fixed thickness of 444 $\AA$ changed from 0.074 to 17.12 $\mu$$\Omega$$\cdot$cm with increasing temperature increase from 600 to $800^{\circ}C$. From these results, we report that the process conditions of$ 692^{\circ}C$-1 hr, $715^{\circ}C$-1 hr, and 73$0^{\circ}C$-1 hr for $TiSi_2$($400 \AA$) are stable by the criteria of 1, 2, and 3 $\mu$$\Omega$$\cdot$cm of $\Delta$resistivity, respectively.
티타늄과 코발트 박막의 산화규소 스페이서에 대한 열적안정성
정성희,송오성,김민성,Cheong, Seong-Hwee,Song, Oh-Sung,Kim, Min-Sung 한국재료학회 2002 한국재료학회지 Vol.12 No.11
We investigated the reaction stability of titanium, cobalt and their bilayer films with side-wall spacer materials of SiO$_2$ for the salicide process. We prepared Ti 350 $\AA$, Co 150 $\AA$, Co 150 $\AA$/Ti 100 $\AA$ and Ti 100 $\AA$/Co 150 $\AA$ films on 1000 $\AA$-thick thermally grown SiO$_2$ substrates, respectively. Then the samples were rapid thermal annealed at the temperatures of $500^{\circ}C$, $600^{\circ}C$, and $700^{\circ}C$ for 20 seconds. We characterized the sheet resistance of the metallic layers with a four-point probe, surface roughness with scanning probe microscope, residual phases with an Auger depth profilometer, phase identification with a X-ray diffractometer, and cross-sectional microstructure evolution with a transmission electron microscope, respectively. We report that Ti reacted with silicon dioxide spacers above $700^{\circ}C$, Co agglomerated at $600^{\circ}C$, and Co/Ti, Ti/Co formed CoTi compound requiring a special wet process.
소오스/드레인 영역의 도펀트 양의 증가에 따른 코발트실리사이드의 물성변화
정성희,송오성,김민성,Cheong, Seong-Hwee,Song, Oh-Sung,Kim, Min-Sung 한국재료학회 2003 한국재료학회지 Vol.13 No.1
As and BF$_2$dopants are implanted for the formation of source/drain with dose of 1${\times}$10$^{15}$ ions/$\textrm{cm}^2$∼5${\times}$10$^{15}$ ions/$\textrm{cm}^2$ then formed cobalt disilicide with Co/Ti deposition and doubly rapid thermal annealing. Appropriate ion implantation and cobalt salicide process are employed to meet the sub-0.13 $\mu\textrm{m}$ CMOS devices. We investigated the process results of sheet resistance, dopant redistribution, and surface-interface microstructure with a four-point probe, a secondary ion mass spectroscope(SIMS), a scanning probe microscope (SPM), and a cross sectional transmission electron microscope(TEM), respectively. Sheet resistance increased to 8%∼12% as dose increased in $CoSi_2$$n^{+}$ and $CoSi_2$$p^{V}$ , while sheet resistance uniformity showed very little variation. SIMS depth profiling revealed that the diffusion of As and B was enhanced as dose increased in $CoSi_2$$n^{+}$ and $CoSi_2$$p^{+}$ . The surface roughness of root mean square(RMS) values measured by a SPM decreased as dose increased in $CoSi_2$$n^{+}$ , while little variation was observed in $CoSi_2$$p^{+}$ . Cross sectional TEM images showed that the spikes of 30 nm∼50 nm-depth were formed at the interfaces of $CoSi_2$$n^{+}$ / and $CoSi_2$/$p^{+}$, which indicate the possible leakage current source. Our result implied that Co/Ti cobalt salicide was compatible with high dose sub-0.13$\mu\textrm{m}$ process.
코발트/니켈 복합실리사이드의 실리사이드온도에 따른 면저항과 미세구조 변화
정영순,정성희,송오성,Jung Young-soon,Cheong Seong-hwee,Song Oh-sung 한국재료학회 2004 한국재료학회지 Vol.14 No.6
The silicide layer used as a diffusion barrier in microelectronics is typically required to be below 50 nm-thick and, the same time, the silicides also need to have low contact resistance without agglomeration at high processing temperatures. We fabricated Si(100)/15 nm-Ni/15 nm-Co samples with a thermal evaporator, and annealed the samples for 40 seconds at temperatures ranging from $700^{\circ}C$ to $1100^{\circ}C$ using rapid thermal annealing. We investigated microstructural and compositional changes during annealing using transmission electron microscopy and auger electron spectroscopy. Sheet resistance of the annealed sample stack was measured with a four point probe. The sheet resistance measurements for our proposed Co/Ni composite silicide was below 8 $\Omega$/sq. even after annealing $1100^{\circ}C$, while conventional nickel-monosilicide showed abrupt phase transformation at $700^{\circ}C$. Microstructure and auger depth profiling showed that the silicides in our sample consisted of intermixed phases of $CoNiSi_{x}$ and NiSi. It was noticed that NiSi grew rapidly at the silicon interface with increasing annealing temperature without transforming into $NiSi_2$. Our results imply that Co/Ni composite silicide should have excellent high temperature stability even in post-silicidation processes.
복합 코발트 실리사이드 공정에 따른 게이트 산화막의 특성변화
송오성,정성희,이상돈,이기영,류지호,Song, Oh-sung,Cheong, Seong-hwee,Yi, Sang-don,Lee, Ki-yung,Ryu, Ji-ho 한국재료학회 2003 한국재료학회지 Vol.13 No.11
Gate length, height, and silicide thickness have all been shrinking linearly as device density has progressively increased over the years. We investigated the effect of the cobalt diffusion during the silicide formation process on the 60$\AA$-thick gate oxide lying underneath the Ti/Co and Co/Ti bilayers. We prepared four different cobalt silicides, which have similar sheet resistance, made from the film structure of Co/Ti(interlayer), and Ti(capping layer)/Co, and peformed the current-voltage, time-to-break down, and capacitance-voltage measurements. Our result revealed that the cobalt silicide process without the Ti capping layer allowed cobalt atoms to diffuse into the upper interface of gate oxides. We propose that 100$\AA$-thick titanium interlayer may lessen the diffusion of cobalt to gate oxides in 1500-$\AA$ height polysilicon gates.