Route planning for two wafer fabs with capacity-sharing mechanisms

Abstract

This paper formulates and solves a route planning problem for semiconductor manufacturing. In order to quickly respond to rising demand, a semiconductor company usually adopts a dual-fab strategy to expand capacity. That is, two fab sites are built as neighbours and can easily share capacity. Through the capacity-sharing design, a product may be produced by a cross-fab route. That is, some operations of a product are carried out in one fab and the other operations in the other fab. This leads to a routing planning problem, which involves two decisions -determining the cut-off point of the cross-fab route and the route ratio for each product -in order to maximise the throughput subject to a cycle time constraint. An LP-GA method is proposed to solve the route planning problem. We first use the LP module to make the cut-off point decisions, and proceed to use the GA module for making the decision on the route ratio. Experimental results show that the LP-GA method significantly outperforms other methods.Keywords: operations management; operations strategy; operations planning IntroductionThe semiconductor manufacturing industry has to consider the following three factors when expanding capacity. The equipment costs are very expensive, perhaps costing over one billion dollars for a 12 inch wafer fab. The lead time for equipment acquisition is quite long, ranging from 3 to 9 months. However, building the factory space is relatively inexpensive, but with a much longer lead time -taking about one to two years.In order to respond quickly to rising demand, a semiconductor company usually adopts a dual-fab strategy to expand capacity. That is, a large-scale factory space that can accommodate two fabs is established in advance. Then, the equipment for the two fabs is gradually moved into the space over time according to market demand. The two fabs, close to each other in location, support each other and should be managed in an integrated manner.In such a dual-fab configuration, a relatively easy way to manage is to manufacture each wafer job in one fab. That is, each fab is run separately, without any mutual support in capacity. Such a separated-operation paradigm usually leads to an underutilisation of equipment. To remedy the underutilisation issue, a cross-fab production paradigm is proposed. This means that a wafer job is partly manufactured in one fab and partly manufactured in the other fab.

An efficient approach to cross-fab route planning for wafer manufacturing

“…Numeric experiments indicated that solutions obtained by the enhanced approach are almost as good as that obtained by Wu et al (2008) yet requires much less computational efforts.…”

“…In order to efficiently solve the route planning problem, this paper presents an enhanced approach based on Wu et al (2008). Numeric experiments indicated that solutions obtained by the enhanced approach are almost as good as that obtained by Wu et al (2008) yet requires much less computational efforts.…”

“…To solve the dual-fab route planning problem, we adopted the solution framework proposed by Wu et al (2008), and developed several enhancements to their solution method in order to reduce computational efforts. As shown in Fig.…”

“…Numeric experiments indicated that the method proposed by Wu, Chen, and Shih (2008) could effectively increase equipment utilization and total throughput for a dual-fab scenario. However, their method may become computationally extensive in dealing with large scale cases.…”

“…Section 3 explains the route planning problem. Section 4 outlines the LP-GA solution framework proposed by Wu et al (2008). Section 5 presents the linear program (LP) and our enhancements to reduce computational time.…”