Online proceedings - EDA Publishing Association

11-13
May 2011, Aix-en-Provence, France
Micro probe array fabrication by using the microlens
array mask through proximity printing
Tsung-Hung Lin 1 , Hsiharng Yang 2 , Ching-Kong Chao 3
1 Graduate Institute of Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
2 Institute of Precision Engineering, National Chung Hsing University, Taichung, Taiwan 402
3 Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 106
Abstract- This study presents a novel and precision
process to fabricate an array of micro metal probes. The
process includes microlens array mask with the proximity
printing in ultraviolet (UV) lithography and Ni electroforming
technology. The tip formation of micro cone probe array
utilizes the microlens array mask through geometrical optics.
Due to the light pass through a microlens, a microlens has a
focal point. The simulated results of various focal lengths using
different diameter of microlenses, the different photoresist
microcone probe array molds can be fabricated. The micro
cone probe array will have great potential in the area of field
emission display applications.
I. INTRODUCTION
Recently, the microprobes play important roles in
many fields, such as probes used in scanning probe
microscopy (SPM) [1] and atomic force microscope (AFM)
[2], microprobes in field emission [3], probe cards [4] and
data storage [5], and so on. The semiconductor and MEMS
devices become smaller and testing process during their
production should follow such a high density trend. The
probe card provides the interface between test equipment
and IC device. In the probe card, controlled collapse chip
connection type probe is usually used and many groups have
developed different types of probe card like cantilever type
and vertical type. The cantilever type contact probe was
used for the linearly arranged electrode pad. In case of the
pads which are irregularly arranged on the entire area of a
chip, the cantilever type contact probe cannot satisfy the
requirement. The vertical type probe cards are required to
measure the controlled collapse chip connection type
devices which have an irregular arrangement. The primary
approach fabrication processes for the vertical probe tip was
bulk- micromachining using deep reactive ion etcher and
electro-plating with the material of Ni. In this study, the
fabrication of micro-cone vertical probe array is proposed
here to provide a novel method. The micro-cone vertical
probe tips with various angles were produced. The
microprobes can be fabricated using several manufacturing
processes, which create small mechanical structures of
silicon, polymer and metal. However, the probe tip can have
several shapes, such as, quadrilateral pyramid, and cone, etc.
There are four main approaches for fabrication of the
different material probe tips. The first is an etching
technique that includes chemical etching and plasma etching
[6, 7]. The silicon chemical etching uses silicon electrolytic
anodization in aqueous hydrofluoric acid, in combination
with light, to etch patterns onto the silicon. The chemical
etching based techniques can produce very sharp tips using
the under-cut control strategy. However, it is difficult to
obtain high density arrayed micro probes with well
controlled morphologies.
Because the etching rate is hard to control and the
working area is restricted by the wafer size, plasma etching
has the drawback of requiring expensive plasma-based
equipment. The second fabrication process to realize
all-metal probes is to use a focused ion or electron beam to
crack an organometallic gas. The resulting tips have a good
aspect ratio and radius of curvature, but this serial process is
slow and it is difficult control the shape of the tips [8]. The
third approach for fabricating tips-shaped polymer
microstructures with patterned metallic coatings has been
developed. This process involves three techniques including
micro-molding, patterned metal layer transfer, and
electrochemical-base sacrificial layer [9].
The fourth fabrication process for the probe tips is
bulk-micromachining using a deep reactive ion etcher or
multiple-exposure in ultraviolet (UV) lithographic and
electro-plating with Ni or Ni–Co material [10-12]. This
study presents a novel process for fabricating the micro
metal probe array. The proposed process will have great
potential in the area of field emission display applications.
The fabrication method of the micro-cone vertical probe
array is presented. The experimental results showed that
micro metal vertical probes with 45° and 60° tip angles. The
proposed method can precisely control the geometric profile
of vertical probe array. This work also offers the new
fabrication method for probe card fabrication.
II. Lithography characteristics
Microlens projection lithography is a kind of non-contact
projection lithography [13]. A plano-convex micorlens
comes in one of its surfaces plane (plano) and the other
convex. Plano convex microlenses have a positive focal
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