Precision passive mechanical alignment of wafers

Abstract

A passive mechanical wafer alignment technique, capable of micron and better alignment accuracy, was developed, fabricated and tested. This technique is based on the principle of elastic averaging: It uses mating pyramid (convex) and groove (concave) elements, which have been previously patterned on the wafers, to passively align wafers to each other as they are stacked. The concave and convex elements were micro machined on 4-in (100) silicon wafers using wet anisotropic (KOH) etching and deep reactive ion etching. Submicron repeatability and accuracy on the order of one micron were shown through testing. Repeatability and accuracy were also measured as a function of the number of engaged elements. Submicrometer repeatability was achieved with as little as eight mating elements. Potential applications of this technique are precision alignment for bonding of multiwafer MEMS devices and three-dimensional (3-D) interconnect integrated circuits (ICs), as well as one-step alignment for simultaneous bonding of multiple wafer stacks. Future work will focus on minimizing the size of the elements.

Surgical Robotics and Instrumentation

“…Noce et al [2] present a marker-less texture based method using a 100 Hz camera. Sauvee et al [3] use a standard endoscope and passive patches attached to the heart surface. To our best knowledge, there is no work published in the area of heart surface tracking that meets aforementioned requirements.…”

“…Therefore, this field of research is open to new ideas. Development of prototypes has been going on since 15 years, based on the concept of inchworm-like movement [1,2,3,4]. The purpose of this study is to develop an alternative method of colonoscopy: a robot that, based on a screw-like movement, should be capable of locomoting autonomously from the rectum to the appendix in human body.…”

A novel method for nanoprecision alignment in wafer bonding applications

“…Such techniques are fundamentally limited by the wavelength of light and practically limited by the mechanical positioning systems required to match the two wafers. Inspired by LEGO TM which demonstrates remarkably accurate alignment (better than 3 µm) with very low tolerances between the individual building bricks, which are fabricated by low cost injection moulding, recently a mechanical passive wafer alignment method has been reported [9] exploiting kinematic and elastic averaging. However, the alignment accuracy was obtained by optically observing the alignment marks located on the nonbonded sides of the wafer pair.…”

Chemical strategies for die/wafer submicron alignment and bonding.

“…Alternative alignment methods have been proposed that are based on the surface tension of adhesives [7]; electrostatic forces [5]; and passive alignment based on the kinematic coupling and elastic averaging [8]. In Ref.…”

“…In Ref. 8, silicon wafers were KOH-etched with mating features (pyramids and v-trenches). An alignment accuracy of 1 m was achieved.…”