Hong-Gui Jang

Cu films by partially ionized beam deposition for ultra large scale integration metallization

Highly (111) oriented Cu films with a thickness around 1800 A were prepared on Si(100) at room temperature by partially ionized beam deposition (PIBD) at pressure of 8 × 10 -7 -1 × 10 -6 Torr. Effects of acceleration voltage ( Va ) between 0 and 4 kV on such properties as crystallinity, surface roughness, resistivity, etc. of the films have been investigated. The Cu films deposited by PIBD had only (111) and (200) planes, and the relative intensity ratio, I (111)/ I (200) of the Cu films increased from 6.8 at V a = 0 kV to 37 at V a = 4 kV. There was no indication of impurities in the system from Auger electron spectroscopy (AES) analyses. A large increase in grain size of the films occurred with V a up to V a = 1 kV, but little increase occurred with V a > 1 kV. Surface roughness of the Cu films decreased with V a , and resistivity showed the same trends as that of the surface roughness. In the Cu films by PIBD, it is considered that changes of resistivity are mainly due to a surface scattering rather than a grain boundary scattering. The via holes, dimensions of which are 0.5 μm in diameter and 1.5 μm in depth, in the Cu films made at V a = 4 kV were completely filled without voids. Interface adhesion of the Cu film on Si(100) deposited at V a = 3 kV was five times greater than that of Cu film deposited at V a = 0 kV, as determined by a scratch test.

Design and tests of the new partially ionized beam source

We developed and evaluated a new partially ionized beam (PIB) source to deposit high quality Cu films. The novelty of the PIB source lies in the fact that the crucible and ionization parts are spaced in one cylindrical shell to make its structure compact and to get a uniform beam profile, but their electric circuits are not separated. In this article, we report the characteristics of the PIB source, such as voltage‐ampere characteristics of the crucible and ionization parts, Cu+ ion beam uniformity with a change of the ionization currents, and deposition rate.

The growth of tin oxide films by reactive ion-assisted deposition

Substoichiometric undoped SnOx (x<2) thin films were deposited on Si (100) substrate using reactive ion-assisted deposition. The effect of oxygen contents and heat treatment on the final crystalline structure of tin oxide films were investigated. Oxygen to Sn metal atomic ratios (NO/NSn) of the as-deposited thin films were changed from 1.14 to 1.91 by varying the relative arrival ratio (Γ) of oxygen ion to Sn metal, i.e., the average energy (Ea) impinging on each depositing Sn metal. Heat treatment was performed in two different ways; the first was post-annealing at 400∼600 °C in a vacuum ∼5×10−3 Torr and the second was in-situ substrate heating. In case of post-annealing, perfect oxidation of SnO2 was found at 600 °C annealing. And it was found that the oxidation from SnO and SnO2 was largely dependent on the initial oxygen contents and annealing temperature. Temperature of tin oxide formation could be reduced as low as 400 °C by assisting energetic oxygen ion through in-situ annealing. Surface microstru...

Thermal Stability of Cu Films on Tin/Ti/Si(100) by Partially Ionized Beam Deposition

Cu thin films with a thickness around 850 A were prepared on Ti 45 N 55 /Ti/Si(100) substrates at room temperature by partially ionized beam deposition (PIBD) with an ion energy of 3 keV at pressure of 8×10 −7 –1 × 10 −6 Torr. The Cu/Ti 45 N 55 /Ti/Si samples were annealed at 8× 10 −6 –1 × 10 −5 Torr with annealing temperature of 500 to 700 °C for 30 min.. Thermal stability of the PIB-Cu films was investigated with Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), Scanning electron microscopy (SEM), and X-ray diffraction (XRD). The as deposited Cu films had a (111) texture and there was no change of phase in annealed Cu films regardless of annealing temperature. Grain size of the annealed Cu films increased with annealing temperature. SEM studies show no hillock and no voiding on the Cu film surface up to annealing temperature of 700 °C. For PIB-Cu/Ti 45 N 55 /Ti/Si samples, all the layers were intact and there was no indication of interdiffusion by conventional depth profiling techniques (RBS, AES) up to 700 °C in vacuum for 30 minutes.

Electrical Resistivity of Copper Films by Partially Ionized Beam Deposition

Copper films on Si(100) were prepared by partially ionized beam at 0 kV and 3 kV acceleration voltages in order to investigate effects of ion energy on electrical property with thickness. X-ray diffraction (XRD) pattern analysis was used to investigate crystallinity of the copper films, microstructure by Scanning electron microscope (SEM) and surface roughness by atomic force microscopy (AFM). The crystallinity of the copper films grown at the 3 kV was more (111) textured than that at the 0 kV. The copper films grown at both conditions had nearly same grain size below a thickness of 1,000 {angstrom}. The 1,800 {angstrom} Cu film grown at the 3 kV was 3 times rough than that at the 0 kV. The resistivity of copper films increased due to surface and grain boundary scattering, and the change of resistivity was discussed in terms of surface roughness, grain size and film density assisted by average depositing energy.