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การประชุมวิชาการดานการวิจัยดําเนินงานแหงชาติ ประจําป 2554
วันที่
8-9 กันยายน 2554 ณ โรงแรม เอส ดี อเวนิว กรุงเทพฯ
Meandering Improvement of Stealth Laser Dicing Process via
Mixed Integer Linear Constrained Response Surface Optimization Model
Wanwisa Sayrasang 1 and Pongchanun Luangpaiboon 2
1, 2
Industrial Statistics and Operational Research Unit (ISO-RU),
Department of Industrial Engineering, Faculty of Engineering, Thammasat University, Pathumthani, Thailand
Tel: 025643002-9 Ext 3081 Fax: 025643017 E-mail: 1 swanwisa@windowslive.com, 2 lpongch@engr.tu.ac.th
Abstract
This paper presents a collection of experimental design and
mathematical programming techniques for meandering quality
improvement in the stealth laser dicing process. The customer
specification of the tolerance of meandering data has to be less than five
microns with the target of zero microns. Currently the meandering data
is slightly higher than the customer specification. This situation leads to
a quality inspection with a large sample size with a high frequency. This
brings the high level of production cost and also time and labors.
Firstly, the 2 k factorial design was applied to preliminarily study the
effects of those five process variables. The multiple regression models
of those responses were then developed from only significant variables
affecting the process response. Finally, the regression model in forms of
the path of steepest descent was placed as the objective function of the
linear constrained response surface optimizations model to meet the
meandering target subject to the limitation from feasible ranges of
significant variables. However, in this study there are some qualitative
variables that need to be in forms of integer whereas the remains are
quantitative. This mixed integer linear constrained response surface
optimizations model provides the new operating conditions. The
experimental results showed that it brings the meandering close to the
target when compared or from 5.90 microns to 3.16 microns.
Keywords: Stealth Laser Dicing Process, Meandering, Response
Surface Methodology, Multiple Regression, Steepest
Descent
1. INTRODUCTION
Dicing process is the process by which die are separated
from a semiconductor wafer following the wafer processing. Chip
carriers encapsulate individual silicon chips from the dicing process to
use in building electronic devices. When wafers are diced, they are
typically mounted on dicing tape to be able to hold the wafer on a thin
sheet metal frame. Silicon wafers dicing may be performed by a laserbased
technique or the stealth laser dicing process (SLDP). There are
two stages on the process. Firstly, the beam from a pulsed laser with
specific wavelengths is scanned along intended cutting lines. Defect
regions are then introduced into the wafer with different depths.
Secondly, an underlying carrier membrane is radically expanded to
induce fracture. The cleavage initiates at the bottom. It advances to the
surface and provides a high distortion density at the bottom.
There some advantages of the stealth dicing process. Firstly,
there is no requirement of a cooling liquid. Secondly, stealth dicing
process hardly generates debris and it is possible to improve the wafer
surface exploitation with a few level of loss when compared to wafer
sawing. On the SLDP, the current level of meandering is still the main
problem. The meandering measures are slightly higher than the
customer specification. This situation leads to a quality inspection with
a large sample size with a high frequency. This brings the high level of
production cost and also time and labor. Therefore, the meandering
quality in the SLDP needs to improve. With high technology machine,
the problem has still existed. It is found that the process performance of
defects is still quite high, as shown in Fig 1. In this case, the deep detail
of stealth dicing process should be investigated so that the optimum
working condition would be determined. Consequently, the problem of
interest would be dissolved