High Bumps Research Articles

特集／電子部品の表面処理 ソルダ・インジェクション法による高密度基板用バンプの作製

特集／電子部品の表面処理 ソルダ・インジェクション法による高密度基板用バンプの作製

STM studies of Si(100)-2×1 oxidation: defect chemistry and Si ejection

The initial stages of oxidation of the Si(100)-2×1 surface have been studied using STM and STS. In contrast to the Si(111)-7×7 surface, which has a metallic density of states (DOS), the dangling bonds of the Si dimers on the 2×1 surface are paired, leading to the formation of a surface gap and a vanishing DOS near E F. We observe a reduced reactivity of Si dimers towards O 2 compared to that of Si adatoms on Si(111)-7x7, consistent with the reduced DOS near E F. Defects on the Si(100)-2×1 surface which have a metallic DOS dominate the reactivity towards O 2 in the early stages of the reaction. Among the new sites generated by the exposure to O 2 are 1.4 Å high bumps on top of the surface. Upon annealing of the O 2-exposed surface or upon O 2 exposure at an elevated temperature these bumps form elongated islands. Evidence is presented suggesting that the bumps and islands likely are due to silicon ejected to the surface by the oxidation reaction. Possible mechanisms and implications are discussed.

Si ejection and regrowth during the initial stages of Si(001) oxidation

The initial stages of oxidation of the Si(001)-2×1 surface have been studied using scanning tunneling microscopy and spectroscopy. Among the new sites generated by the exposure of this surface to O2 are 1.4 Å high bumps on top of the surface. Upon annealing the O2-exposed surface, or upon O2 exposure at an elevated temperature, these bumps form highly anisotropic islands. Evidence is presented that these bumps and islands are made up of silicon ejected from the surface by the oxidation reaction.

Tape automated bonding inner lead bonding with a laser for high performance applications

Since 1985, MCC has been developing the use of flashlamp pulsed Nd:YAG (YAG) laser technology to bond tape automated bonding (TAB) leads to I/O pads on integrated circuits (ICs). The I/O pads have 22 micron high gold bumps and the leads are copper plated, in the case described here, with electroless tin. As a result of the work presented here, a methodology has been developed that will result in a high throughput, reliable bonding process that overcomes the limitations of conventional thermocompression (T/C) and thermosonic (T/S) bonding technologies. In addition, because the position of the laser beam is software controlled, the process is very desirable for applications where a broad range of different IC form factors and sizes are to be bonded. Laser bonded devices have been exposed to degrading environments without failure, indicating the long term reliability of the process.

Straight Wall Bumps for High Lead Count Devices: Photolithography and Physical Properties.

AbstractThis paper will report on a novel photolithographic process suitable for the fabrication of gold bumps on high lead count devices. Utilizing a photosensitive polyimide, straight wall bumps are grown completely recessed within the polyimide layer to a typical height of 25 microns.The photolithographic step of the bumping process will be described. Good layer uniformity in conjunction with exposure in vacuum hard contact mode leads to practically vertical walls of the opening in the polyimide layer after develop.Straight wall gold bumps have been electroplated in 30 micron wide openings with a 50 micron centerline spacing. This density is beyond the present spacing capability of TAB in production. The bumping process is no longer the limiting factor in high lead count device fabrication.Potential residues in the polyimide openings would result in bad bump adhesion strength and high bump contact resistance to the underlying metallization. These two parameters were used for the process optimization.

Can quantum-bumps in photoreceptors be reconstructed from noise-data?

The method of reconstructing quantum bumps in photoreceptor cells from noise data by making use of shot noise theory is critically reviewed. The application of this method produces results irrespective of whether the conditions for reconstructing bumps by the method are satisfied or not and even irrespective of whether at high stimulus intensities quantum bumps exist or not. We argue that at high intensities the concept of quantum bumps indeed becomes physically meaningless and degenerates to a purely mathematical concept. In order to investigate the meaning of the results of the reconstruction method, we submit it to a test model for which bumps and single channel opening events can be evaluated analytically. By comparing the analytical results of the test model with that of the reconstruction method applied to the test model we find: (1) even at low intensities, the reconstructed bump values deviate from the analytical results by up to an order of magnitude due to the variability of the bumps, (2) at high intensities, the reconstruction method produces single channel opening events rather than anything like a quantum bump. We also find, however, that there is no continuous transition from a bump at low intensities to a single channel event at high intensities.