This paper reports on the passivating properties of PCVD silicon nitride obtained from the gas mixtures N.2 + Sill4 diluted in Ar (Sill JAr) and N2 + Sill4 diluted in He (SiHJHe). Ellipsometric data, Auger data, IR data, mechanical stress, pinholes, and electrical data are presented. The stability of the hydrogen bonds in the silicon nitride is evaluated by low temperature annealing. By comparison of the properties of nitrides made from N2 + SiH4/He and N2 + Sill JAr, it is concluded that the former one yields more uniform films, less critical to deposition temperature, while the latter process behaves better for passivating purposes. On the other hand, it is shown that the carrier gas (He or Ar) has a marked influence on the properties of the films, especially on the hydrogen content. It is found that both PCVD nitrides are best described as SixN,H~Ot.Undoubtedly, the major advantage of PCVD techniques is the low temperature processing involved. Thus, the most important application of PCVD silicon nitride is the passivation of integrated circuits. In this application, the deposition temperature is at most 350~ Therefore, we examined silicon nitride films deposited at 150 ~ 200 ~ and 300~ A capacitively coupled parallel plate PCVD reactor, manufactured by L.F.E., Incorporated (Model PND-301), has been used for the depositions. A schematic diagram of this apparatus has been given elsewhere (1).Among the different possible gas mixtures, we used diluted silane (as a safety precaution) and nitrogen. Nitrogen was preferred to ammonia, because it leads to silicon nitride films with a lower hydrogen content. Sill4 was diluted up to 1.75% in commonly used Ar (SiHJAr) or in He (SiHJHe). He was used because it was mentioned in the literature (2) that films deposited with SiHJHe show more uniform properties.A review of the literature on PCVD silicon nitrides shows that a major part of the work has been done on nitride films deposited by mixtures of Sill4 and NH3. It is also found that the properties of the nitride films not only depend on the gases, but also on the actual reactor configuration used. This explains why some of the results reported here are not fully comparable to previous work on a L.F.E. reactor reported by Dun et al. (3). Dun premixes the gases SiH~ and N~, while our equipment configuration consists of a separated gas inlet system. We found, for both SiH4/Ar and SiHJHe gas mixtures, the resulting nitride films to be Si rich and become even more Si rich as deposition temperature increases. This is in agreement with results obtained by Maeda et al.(1) in the same L.F.E. reactor. However, Maeda did not examine the influence of different carrier gases. This Si dependency on deposition temperature will be explained by the fact that PCVD silicon nitrides have no fixed st0ichiome-try, so that they are best described as Si~N,HzO~. From this formula, a consistent definition for the Si/N ratio will be derived.As our goal was the investigation of the dependence of the passivation properties of silicon nitride on the d...

Analytical thermomechanical models have been developed in order to calculate the thermally induced stresses in leadless solder interconnection systems. Two different analytical models are highlighted: the peripheral and area array thermomechanical model which describe the thermally induced stresses for two components connected to each other with a peripheral, respectively, area array of joints. The analytical models are based on structural mechanics and have the ability to characterize the nature and estimate the magnitude of the joint stresses. Using these models, structural design optimization of interconnection systems can be performed very quickly in order to reduce time consuming experiments and finite element simulations. It is found that the largest stresses in the solder joints of flip chip assemblies are at the top and bottom surface of the connection and that they are especially caused by bending moments subjected to the joints. Comparisons with finite element simulations have proved a good accuracy of the thermomechanical models.

The embedding of passive components such as resistors, capacitors and inductors within printed circuit boards (PCBs) is motivated, to a large extent, by the desire for increased miniaturisation of electronic goods. However, resistors and, to a lesser extent, inductors are heat generating devices, and the temperature developed within PCBs as the result of the operation of embedded passives is a significant aspect of the design of a multilayer PCB. Here we investigate, by simulation, temperature fields associated with operation of embedded resistors. It is shown that for board dimensions less than 2cm × 2cm temperatures achieved are higher than those associated with larger boards having identical structures and identical resistor heat generation. Detailed simulations are used to investigate the sensitivity of the temperature rises associated with embedded resistors to copper track coverage and to thermal coupling of the PCB to ambient on its upper and lower surfaces. The implications of these findings are discussed both in the context of the design of real PCBs and in the context of thermal simulation.

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