Gretchen M. Adema

Passivation schemes for copper/polymer thin film interconnections used in multichip modules

The use of thin inorganic dielectric films as barrier layers between copper and polyimide was examined. Emphasis was placed on discovering the effectiveness of the barrier layers in preventing copper/polyimide interaction and determining its impact on the high-frequency electrical performance of transmission line structures. The integrity of the inorganic dielectric layers as diffusion barriers for the copper was analyzed using transmission electron microscopy. These effects were studied by depositing thin layers of Si/sub 3/N/sub 4/, SiO/sub 2/, and SiO/sub x/N/sub y/ between chromium/copper/chromium lines and either Dow benzocyclobutene or Dupont 2525 polyimide. Both sputtered Si/sub 3/N/sub 4/ and PECVD SiO/sub x/N/sub y/ behaved as diffusion barriers, which resulted in improved performance at very high frequencies over unprotected transmission lines.<<ETX>>

Effects of polymer/metal interaction in thin-film multichip module applications

An investigation was conducted to examine the effects of different polyimide/metal combinations on structures similar to those used in thin-film multichip module applications. Three different metal structures and three commercially available spin-on polyimide materials which possess different molecular structures were examined. Transmission electron microscopy was used to study the polyimide/metal interfaces. Measurements of the transmission characteristics of line structures fabricated using the different metal/polyimide combinations were compared. It was found that the extent of interaction of polyimide with copper is dependent upon the type of polyimide used. Dupont 2611D polyimide showed the least amount of interaction with only a small band of precipitates present approximately 5 kAA from the copper/polyimide interface, which do not affect the electrical transmission characteristics of lines spaced 22 mu m a part. The use of an electrodes nickel layer on copper to retard copper/polyimide interaction from occurring during the curing cycle of the polyimide was found to be effective. However, increased loss of transmission at high frequencies and narrow spacing was seen for nickel-clad lines embedded in Dupont 2611D polyimide. Since nickel is a magnetic material, this increase in loss may be due to natural inductance from the nickel present in neighboring lines.<<ETX>>

Benzocyclobutene as a dielectric for multichip module fabrication

Data compiled for an experimental nonsilicon-containing benzocyclobutene (BCBII) are presented. The results are compared with those obtained from the standard silicon-containing benzocyclobutene (BCBI). The comparison is based on results obtained from studies of properties such as planarization, stress, adhesion, and pinhole density on both spin and spray coatings of the BCB materials. Planarization studies were performed using a test pattern containing a variety of linewidth and space dimensions. A single-beam laser deflection method was utilized for the measurement of stress. Adhesion properties were determined using a Sebastian III adherence tester. A summary of these results and their implications for the use of BCB as a dielectric material for multichip module (MCM) fabrication is presented.<<ETX>>

Design and process impact on thin-film interconnection performance

The performance of thin-film interconnections is influenced by the manner in which material selection and design rules interact with process capabilities. To understand this influence analysis of predicted and measured interconnection performance was correlated to design and process attributes. The models employed to predict propagation delay and noise are described and compared to experimental results. Attributes which contribute significantly to successful implementation of this technology are identified and accommodations in process controls and design rules are suggested.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.