Y. Kato

Aluminum selective area deposition on Si using diethylaluminumchloride

Aluminum deposition on Si was studied using diethylaluminumchloride (DEAlCl) as a new Al chemical vapor deposition source. Selective area deposition was successfully achieved at substrate temperatures of 313–380 °C. The deposition rate was higher than 370 A/min. Reflectance and resistivity of the deposited films were comparable to those of the evaporated ones. Decomposition experiments suggest that DEAlCl catalytically decomposes on the Al surface, which would explain the high selectivity observed.

Temperature programmed desorption study of GaAs(100)−c(4×4) and As4 exposed (2×4) surfaces

Abstract GaAs(100)−c(4×4) and As4 exposed (2×4) surfaces are studied using temperature programmed desorption (TPD) and reflection high energy electron diffraction (RHEED). The As sensitive factor for a quadrupole mass spectrometer is precisely calibrated and the As coverage is determined from As2 desorption spectra. For the c(4×4) surface, there are two steps in the As desorption process. Coverage analysis indicates that the c(4×4) structure is formed at an As coverage, θAs, of 1.28 monolayer (ML) and an additional As adsorption is possible up to a θAs of 1.61 ML without disturbing the reconstruction. At higher θAs, a repulsive interaction between adsorbed As dimers is suggested. On the As4 exposed (2×4) surfaces, the chemisorbed As desorbs at 430 and 500°C as As2. Based on RHEED observations, As2 peaking at 500°C is assigned to desorption due to transition from a (2×4)-γ to a (2×4) surface structure. The structures of these surfaces are discussed based on our TPD results and previously proposed structure models.

Anomalous As desorption from InAs(100) 2×4

Arsenic desorption from the InAs(100) 2×4 surface is investigated through temperature programmed desorption (TPD), isothermal desorption, and reflection high‐energy electron diffraction. TPD area analysis indicates that the As coverage, θAs, of the InAs 2×4 structure is 0.7 monolayers. The As TPD spectrum shows two desorption features; a broad tail from 300 to 400 °C and a distinct peak at 430 °C. The 430 °C peak is well described in terms of a first‐order‐desorption kinetics with a preexponential factor ν of 1.5×1019 s−1. This extremely high ν value explains well the narrow window of optimal molecular beam epitaxy growth conditions for InAs.

Temperature programmed desorption study of gallium chloride adsorbed on GaAs surfaces

Adsorption of gallium chloride (GaCl) on GaAs (100), (111)A and (111)B surfaces is studied by temperature programmed desorption (TPD). A GaCl molecular beam is produced by a newly designed GaCl cell. TPD measurements are carried out for (100) 2×4, (100) 4×6, (111)B √19×√19 and (111)A 2×2 reconstructed surfaces. GaCl desorption is observed from these surfaces, while the desorption of GaClx(x=2, 3), AsClx(x=1≁3) and Cl2 is not detected. Two GaCl peaks appear at 220 and 330°C for (100) 2×4, 4×6 and (111)A 2×2 surfaces, and a single peak appears at 330°C for the (111)B surface. The GaCl peaks at 220 and 330°C are assigned to the adsorption on Ga and As sites, respectively. The adsorption energy of GaCl is calculated to be 38 kcal/mol for the As sites and 32 kcal/mol for the Ga sites. The self-limiting process in chloride atomic layer epitaxy (ALE) is discussed.

Semi-insulating current blocking property simulations for buried heterostructure laser diodes

A compound‐semiconductor device simulator, in which deep levels in the semi‐insulating layers can be taken into account, has been developed. By using this simulator, the electrical properties for the semi‐insulating InP buried heterostructure laser diodes were investigated. The leakage current, without passing through the active region, was found to be small when the trap density in the semi‐insulating InP layers is more than 3×1015 cm−3 and less than 1×1016 cm−3. This simulator will be a useful tool in predicting the semi‐insulating properties of electrical and optical semiconductor devices.

Growth of InAs and (InAs)1(GaAs)5 superlattice by atomic layer epitaxy using dimethylindium chloride

InAs is grown by metalorganic atomic layer epitaxy (MOALE) using dimethylindium chloride (DMInCl) as a new In source material for ALE in a horizontal, low‐pressure metalorganic chemical vapor deposition (MOCVD) system. Monolayer‐unit growth is obtained over a wide range of growth temperatures from 400 to 475 °C, and of substrate exposure times to DMInCl from 15 to 27 s. With metalorganic chloride source gases, both InAs and GaAs growth are self‐limited over a temperature range of 50 °C, from 425 to 475 °C. This is the widest temperature range so far reported. This advantage is applied to ALE growth of (InAs)1(GaAs)5 superlattice.

Plasma CVD of (BaSr)TiO3 Dielectrics for Gigabit DRAM Capacitors

Electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) of (BaSr)TiO3 dielectrics is reviewed. The oxygen plasma lowered the crystallization temperature and carbon contamination. (BaSr)TiO3 CVD process was developed under conditions of relatively low deposition rate of 1.1 nm/min and a relatively low deposition temperature of 550°C. Utilizing this process, we developed a gigabit dynamic random access memory (DRAM) capacitor technology involving the preparation of a thin (BaSr)TiO3 capacitor dielectric over a RuO2/Ru storage node contacting a TiN/TiSiX/poly-Si plug. The ECR plasma CVD enabled uniform deposition of gigabit-DRAM-quality (BaSr)TiO3 films on the electrode sidewalls. The storage node contact improved in endurance against oxidation, by fabricating the buried-in TiN/TiSiX plug (TiN-capped plug) under the RuO2/Ru storage node. (BaSr)TiO3 films with a small equivalent SiO2 thickness of 0.38 nm and a leakage current density of 8.5×10−7 A/cm2 at an applied voltage of 1.0 V, were obtained without any further annealing process. An equivalent SiO2 thickness of 0.40 nm on the RuO2 sidewall was also achieved. It is concluded that this technology has reached the requirements for gigabit DRAM capacitors.

In situ x‐ray photoelectron spectroscopy and reflection high‐energy electron diffraction study of diethylgalliumchloride adsorption on Si (100) and Si (111) surfaces

Diethylgalliumchloride (DEGaCl) adsorption on Si(100) 2×1 and Si(111) 7×7 surfaces is studied by reflection high‐energy electron diffraction and x‐ray photoelectron spectroscopy. DEGaCl adsorbs molecularly on the (100) surface at room temperature, while the Ga—Cl bond dissociates on Si(111). The Si(111) 7×7 structure is greatly disturbed after DEGaCl exposure, indicating a strong interaction between the surface and the adsorbate. The spatial distribution of dangling bonds is thought to be responsible for the differences in the reactivity between the two surfaces. The Ga—ethyl bond dissociates on both Si(100) and (111) surfaces after annealing at 210 °C, and at the same time Cl desorbs from the surfaces. The Cl desorption process is also discussed.

Low Temperature Recovery of Ru/(Ba, Sr)TiO3/Ru Capacitors Degraded by Forming Gas Annealing

A low temperature N2 post-annealing process was proposed to improve the degradation of Ru/(Ba, Sr)TiO3/Ru capacitors due to forming gas annealing. After N2 post-annealing at 300°C, the leakage current degraded by forming gas annealing was completely recovered to the initial level without affecting the SiO2 equivalent thickness of 0.51 nm. No degradation of the subthreshold characteristics of n-channel metal-oxide-semiconductor field effect transistors and N+P junction leakage current by the post-annealing was also confirmed. The Ru/(Ba, Sr)TiO3/Ru capacitor technology with this post-annealing process is suitable for dynamic random access memories in 0.13 µm generation and beyond.