Hyman Joseph Levinstein

Thermal stresses and cracking resistance of dielectric films (SiN, Si3N4, and SiO2) on Si substrates

In device‐manufacturing technology, it is important to understand why dielectric films crack. With this objective in mind, we have constructed an apparatus for measurement of thermal stresses in thin films (25–500 °C), obtained results on various reactively plasma deposited (RPD) Si‐N and CVD SiO2 films, and developed a model which quantifies the cracking resistance of different types of RPD Si‐N films. Measurements were made of the coefficient of thermal expansion α (T), which increases on going from SiO2→Si3N4→SiN→Si and the intrinsic stress, which is compressive for RPD Si3N4, nearly zero for thermal SiO2 and tensile for RPD SiN and CVD SiO2. The cracking resistance of Si‐N film at a given temperature is functionally related to its density, intrinsic stress, thermal mismatch with Si, and the deposition temperature.

Thin‐film interaction in aluminum and platinum

The interdiffusion and intermetallic formation in thin‐film sandwiches of platinum on preannealed aluminum has been investigated at temperatures in the range 200–500 °C. X‐ray diffractometer studies, sheet‐resistivity measurements, and microscopic studies were employed to follow the metallurgical reaction. It has been found that Al‐Pt interact very rapidly, leading to the formation of several intermetallics. In heat‐treated samples with thick aluminum (?6000 A), Pt2Al3, PtAl2, PtAl3, and PtAl4 were present. In others with 4000 A or less Al, platinum‐rich phases Pt5Al3 and Pt3Al2 were detected. After prolonged or high‐temperature anneals, phases comparatively richer in Al were found to grow at the expense of other phases formed earlier. The Al‐Pt interaction rate was found to be dependent on the annealing ambient, being significantly higher in forming gas, argon, or helium than in vacuum or air. Also, the intermetallic formation resulted in large stress changes in the composite Al‐Pt films due to a volume increase accompanying the formation of Al‐rich phases, which led to the loss of adhesion.

Oxidation of silicon without the formation of stacking faults

A new technique of eliminating oxidation‐induced surface stacking faults has been developed. It involves heating clean silicon wafers in an inert or HCl‐inert ambient in the same furnace where subsequent oxidation—wet or dry—will be carried out. Typical fault densities after oxidation without in situ cleaning are 1000–5000 and 50–500/cm2 for n‐ and p‐type wafers; these numbers are reduced to ∼10–100 and 0, respectively, when in situ cleaning is used.

Localized control of magnetization in LPE bubble garnet films

A new method of obtaining fine scale localized control of the magnetization, 4\piM , for defining bubble tracks in LPE garnet films is described. It involves the deposition of a thin film of silicon on the garnet surface and then annealing in oxygen, or inert gas, at moderate elevated temperatures. Under the silicon, 4\piM decreases by large amounts upon annealing. These reductions in 4\piM , together with photolithographic techniques, can be used to define tracks for bubble propagation. Bubble propagation bit rates up to 1 MHz have been obtained in tracks \sim6 \mu m wide. A mechanism to explain the effect is proposed involving a lowering of the relaxation time for transfer of gallium ions from octahedral to tetrahedral sites due to the presence of local oxygen defects, or Fe2+, produced in the garnet film by removal of oxygen at the heated garnet-silicon interface. In areas not covered by silicon, 4\piM remains unchanged.

Multilayer Garnet Films for Hard Bubble Suppression

The basic principles of multilayer epitaxial garnet films were discussed in an earlier paper.1 The most useful multilayer configuration consists of a relatively high moment outer garnet film epitaxially grown on a low moment inner film. At the operating bias field the inner layer fully saturates and bubbles are supported in the outer layer only. The interfacial domain walls thus produced provide an avenue whereby Bloch‐Neel transitions can unwind to convert hard bubbles into normal bubbles.2,3 Thus use of properly designed multilayer films provides the bubble circuit designer with one solution to the hard bubble problem.

CORRELATION OF DOMAIN WALL MOBILITY WITH GALLIUM CONCENTRATION IN BUBBLE GARNETS

Increased domain wall mobilities have been observed with increased gallium concentration in liquid phase epitaxial (LEE) films of Ga and/or Al substituted Eu3−xErxFe5012. As the total substitution is raised from about 0.7 to 1.8 of the 5 Fe ions, the Neel temperature, YN, decreases from 450 K to 320 K and the mobility rises from ∼25 to ∼450 cm/sec Oe. Reduced uniaxial anisotropy accounts for only a minor part of this increase in mobility. Reduction of the exchange energy by ∼25% in the low Neel temperature samples should give rise to a reduction of ∼13% in their mobilities, opposite to the observed change. Differences in thickness or magnetization between the samples do not correlate with the mobility changes. The coercivity decreases with TN, but this is probably not the cause of the increase in mobility. Variations of the g‐factor from ∼0.6 to >7 were observed in these materials but this increased g probably also does not account for the mobility increases. The relevant mechanisms could include reduced ...

Domain Wall Dislocation Interactions in RbFeF3

RbFeF3 is a transparent ferromagnet (below 87°K) with a large Faraday rotation which permits the direct observation of magnetic domain structures in bulk crystals. An etch‐pitting solution has been developed which reveals the dislocation configuration existing in the crystals, and it has been demonstrated that RbFeF3 exhibits sufficient plasticity so that arrays of dislocations can be put into crystals. The role of dislocation subboundaries and slip bands as nucleation sites for reversed magnetic domains will be demonstrated. The effectiveness of subboundaries and slip bands as pinning sites for domain walls when subjected to varying dc and ac magnetic fields are discussed.