Lateral probing method and monolithically fabricated probes for minimization of damage on the solder of fine pitch micro-bumps

Abstract

In this study, we propose a new method of probing micro-bump electrodes at once, which is dense and compact as the technology develops in the wafer testing stage, where semiconductor chips inspect defective products before expensive packaging processes. The probing of the conventional vertical contact method causes the increase in the force due to the displacement to occur continuously when probing the micro-bump array with the height error, so that the contact with the bump is incomplete and the solder part of the bump damages. In order to solve this problem, a conventional vertically-contact type probe tip structure widely used has a very long aspect ratio structure in order to reduce a force increase due to a displacement for the low damage of the solder. It is impossible to manufacture based on a semiconductor process which has advantages in economical efficiency and mass production, and since the probe tip must be manufactured manually by a possible method, economical efficiency and mass productivity are remarkably deteriorated. Also, fabrication by monolithic MEMS process is complicated and requires a lot of repetitive work, which is also low cost and mass productivity. The shape and contact method of the monolithic MEMS probe tip proposed in this study is a method of laterally contacting the side of the micro-bump, and it is very easy to evaluate the electrical defect of the device with a relatively simple influence on the height deviation of the micro-bumps. This makes it possible to test electrical performance reliability of the micro-bumps with probe arrays made using monolithic MEMS processes when testing for dense, non-flat areas such as micro-bumps found in semiconductor devices or package structures. The proposed probes were fabricated in a monolithic process through low cost probe tip fabrication, which verified side contact probes that do not damage the solder of the bump. As a result, more than 5,000 probe arrays were fabricated and verified. The bump-probe contact shows no damage on the solder and contact resistance was less than 1.13 $omega$. The probe was mechanically driven 100,000 times without breakage, 2 $omega$ or less.