Significant improvement in step coverage using bias sputtered aluminum

Abstract

The degree to which deposited metals cover steps over topography is important to the yield and reliability of devices in very large scale integrations. In evaporated and sputtered films the most difficult steps to cover are those with straight walls. This is especially true with aluminum and its alloys. Via step coverage has been studied as a function of bias sputtering parameters. It was found that 1.3 μm diam, straight-walled vias 1 μm deep, are planarized (100% step coverage) under the same conditions that 60% coverage is achieved in 2.8 μm vias. Unbiased deposition results in only 20% coverage. The effects of target power, bias voltage, and anode voltage on bias current and step coverage were studied. The low power delivered to the substrate under conditions for planarization is not consistent with a mechanism involving backsputtering of aluminum; no significant change in the measured deposition rate was found when bias was introduced. Cross-sectional microscopy suggests a mechanism involving forward scattering of surface atoms at the via edge under bombardment by bias ions.

Residue-free plasma etching of polyimide coatings for small pitch vias with improved step coverage

“…Techniques such as spray-coating, electrodeposition and bias sputtering have been reported to significantly improve the step coverage of resist 19 and aluminum 20 layers, respectively. These techniques however usually require extraprocessing steps and/or nonstandard tools.…”

Backside bonding for extremely narrow bezel at the bottom of flexible displays

“…As the TA decreased, the area occupied by the M‐CNT holes increased, leading to the wider bezel width. On the other hand, the TA close to 90° could result in abnormal deposition or cracks in the CM Layer and third barrier due to step coverage 8,9 . Therefore, it was important to optimize the TA through dry etching.…”

“…On the other hand, the TA close to 90 could result in abnormal deposition or cracks in the CM Layer and third barrier due to step coverage. 8,9 Therefore, it was important to optimize the TA through dry etching. The TA was measured depending on an oxygen plasma mixed with an additional gas under the conditions as shown in Figure 4.…”

Sputter Deposition Processes

“…Planarization of thin metal coatings and coverage of steps, such as vias a few microns in diameter, is required for precise pattern alignment and reliability in the realization of very large scale integration [93][94][95][96][97][98]. As the sizes of vias and contacts become smaller, the aspect ratio of steps becomes high.…”