Adequate annual productivity improvements are not achievable by merely assessing fab efficiencies - particular in introducing 300mm wafer production. Driving lean operations through the whole supply chain is indeed a growing need. IC companies cannot wait and operational excellence practices must be integrated into the entire value chain to include the product development cycle, say Eli Peleg and Ben Scheiner of Tefen Europe. Further, tried and tested manufacturing excellence techniques need to be integrated into the R&D cycle...

In 1996, the first discussions on how to operate a 300mm fab were initiated. The primary goal was to keep productivity improvement within the industry to 25% per year while driving the cost per die down. With yields driven almost to perfection, feature and wafer sizes along with operational efficiencies were the main productivity drivers. While IC annual sales in 2002 are back to 1996 levels of around $150 billion, unit sales have grown by 60% to some 29 billion - in short, the pressure to minimise price per die is immense.

The period from 1996-2000 also saw an immense transfer of manufacturing capacity from integrated device manufacturers (IDMs) in the US and Europe to Asia Pacific (mainly Taiwan) - largely due to the "Foundry Phenomenon". The primary motivation for this shift, from the operational perspective, was cost: how cheap and in what volumes manufacturers can produce? One result of this boom-time tactic is dramatic - US fab capacity has dropped from first in 1996 to fourth in 2002. While feature size decreases are not considered anymore to be limiting factors (there is a clear roadmap about how the industry will get to 45nm and even 30nm (2000/2001 ITRS) processing), it is not clear what deliverables and methods are needed to sufficiently increase operational efficiencies. What is clear is that a 25% annual productivity improvement is not achievable by looking only at fab efficiencies, challenging as they may be.

Drivers

It is calculated that a company is required to have at least $4 billion in revenues to build a $1.6 billion 300mm fab. Yet, this will not stop the increase in 300mm production: as fab utilisation increases, there will be the construction of more and more 300mm fabs. Relative fab productivity therefore will remain important. Automation/computer-integrated manufacturing (CIM), advanced process control (APC), equipment performance and facility management remain, as always, part of the drive and challenge to achieve the required efficiencies.

Production at 300mm presents both new manufacturing opportunities and challenges to increase fab productivity. On the positive side, a major leap has been made with the introduction of 300mm production in terms of increasing the wafer area and die per wafer - including better use of the edge of the wafer - thereby enabling much greater output for a similar input. In a marked comparison with 200mm fabs, the design criteria for 300mm fabs were defined in a uniform manner. Automation was the key driver resulting in

* uniform carriers - Front Opening Uniform Pods (FOUPs) to provide a standard, consistent environment for the wafers

* interbay-intrabay transport as standard

* material identification and handling to reduce misprocessing

The most important factor is the need for full integration between the tool, the automated material handling system (AMHS) and the manufacturing execution system (MES). Along with the fab issues, new challenges have arisen regarding the toolset, automation and operations.

The new 300mm toolset is untried, will typically have teething problems and takes longer to reach the required uptime than it would with 200mm tools which have been tried and tested. Additionally, the cost of 300mm tools is higher due to the development of new tools and this cost is passed on to the IC producers. The cost of running a fab increases as tool depreciation becomes an even greater cost contributor. Although the toolset is designed for automation, the timeline for full and comprehensive automation is usually longer than the timeline for full ramp up. Therefore, the tools will be installed and running in the fab before the fab automation system has the ability to deliver the lot from the stocker to the tools. Additionally, tools will be loaded manually, sometimes for several years. If the fab is to achieve good cycle time and throughput in the short and long terms, the tool design must incorporate the ability for manual loading and staging as well as for an automated set up. These criteria can conflict.

Fab automation at 300mm will include lot selection, lot dispatching from stocker to stocker and from stocker to tool, automatic recipe download and running the lot. It also means full reporting and data collection. Because of the increased weight and value of the FOUPs compared to 200mm wafers, the automation has to be comprehensive and cover all aspects of selection, dispatching, transporting and loading the lots. Thus, fab automation becomes a critical factor in the running of the fab - if the automation system goes down - the fab goes down.

Full automation encompasses a range of systems that need to be linked and integrated to achieve the full advantages. These include the manufacturing execution systems (MES), real-time dispatching, data warehousing and reporting systems, process data collection, APC data collection and key performance indicator (KPI) systems. The complexity derived from these comprehensive and integrated systems is significant and can be both an enabler for manufacturing excellence and a severe drain on IT resources and fab productivity.

Another challenge is cost. Because the system is so comprehensive, the cost is much higher than for 200mm fabs. This is both in terms of the cost of setting up and maintaining the system. Moreover, the standards that were set up for 300mm defined a new concept in automation. As for the new tools, lot delivery requires increased testing and qualification until the level required for a ramped fab can be reached. This is in contrast to 150/200mm fabs, some of which have been running full automation for several years.

New style operations bring a host of other challenges, principally:

* Ergonomics: a full FOUP weighs over 8kg. While legal in the European Union (EU), an individual carrying this kind of weight throughout a shift can make mistakes due to fatigue. This provides additional justification for automation. In addition - one FOUP could easily contain several hundred thousand of Euros worth of wafers.

* Maintenance: the new tools require new maintenance programmes. The cost of tools requires quicker reaction times.

* Operator scope of work: in the short term, the operator is required to interact heavily with the tools and the lots. Interim systems need to be developed and implemented to enable successful and easy operations in the short term. Due to the cost of the tools - operator efficiency is as vital if not more so than in 150/200mm fabs. In the longer term, little or no interaction will be required.

* Number of tools: due to the larger size of the wafers, the number of tools required is smaller. This creates challenges in scheduling and dedication of the tools.

Supply chain

Whether the foundry phenomenon will continue or not is uncertain. IDMs are using another operational strategy to enable them to move to 300mm fabrication - joint ventures (JVs). The main drivers - beyond the financial considerations - are risk and cost. As depreciation is the biggest factor in a new fab cost structure, moving to a foundry solution or JV can improve the IDM's bottom line. The downside is that both ways drive operations far beyond fab efficiencies.

The "B" cycle in Figure 1 illustrates the different drivers of the manufacturing cycle. Integrating several remote manufacturing facilities and the effectiveness of managing the supply chain is becoming one of the most difficult challenges in the industry. A lean supply chain becomes an important player in operation excellence.

Fig.1: The manufacturing cycle

The complexity of managing a multiple location supply chain process resides in the need to manage and control three dimensions:

* The overall chain capacity/capabilities and material flow

* The information flow

* The knowledge flow

The key word for a successful integration of all three into an efficient supply chain is "synchronicity" (synchronisation and simplification).

The objective of an efficient supply chain is to deliver products of the highest quality in less time and lower costs than anywhere else in the world. This may be termed the product delivery system (PDS). The five main rules of PDS are:

* Start with the customer - define and understand the market needs, the delivery requirements, the demand at the point of sale and the flexible response required to answer these needs.

* Deliver on demand - simplify ordering and enable direct shipment to cut delays between the customer and the company. Implement a Kanban pull system to increase on-time delivery and reduce stockouts and ensure lean warehouse operations to reduce inventory and logistics costs.

* Build what you sold, using rate base planning and scheduling to ensure alignment of manufacturing to demand and implement lean production and process capabilities that ensure cost effective and agile supply.

* Supply what is consumed by investing in supplier relationships to achieve daily deliveries and a short supplier response time. Implement a Kanban system with the suppliers and audit and certify supplier quality so that it can be relied on.

* Enable a flexible balanced flow so that the customer demand 'pulls' the rate of delivery, production and supply.

What is required from IC companies to manage their supply chain is therefore to create a simplified flow, to minimise scrap and inventory, to eliminate walls between factories, to eliminate waste throughout the system, to synchronise the entire production system and to integrate suppliers (foundries) and resources (JVs).

Sematech is proposing eManufacturing as a main engine for supply chain productivity and it may indeed be necessary as long as lean practices are implemented across the supply chain in parallel. The key differentiator in eManufacturing is the ability to integrate the suppliers as well as the customers into information systems, creating a "virtual organisation" or virtual execution system (VES). There is no doubt that today's Internet technology is indeed an enabling technology for VES and extremely useful - but not the solution in itself.

R&D

The important factor in every company's success was - and still is - time to market. From an operations point of view, it is not only manufacturing cycle time nor overall supply chain effectiveness, but efficient product and process development cycles illustrated as the "A" cycle in Figure 1. R&D efficiencies, rapid prototyping and fast process development are growing factors of semiconductor operations excellence.

Some of the challenges in achieving efficient R&D processes include

* late introduction to market which shortens development time

* quality problems and long integration processes

* lack of a good development methodology and a dependency on individuals' knowledge ("tribal knowledge") in many companies

* difficulty in making firm commitments to customers

* frequent design changes which require additional design cycles

* problematic transfer to manufacturing due to lack of manufacturing readiness or a long transfer lead time from design to manufacturing (fab and assembly/test process development).

All of the above will result in schedule delays, quality problems, unplanned costs. Increasing R&D efficiencies will require a dual approach as illustrated in Figure 2 covering project management and R&D management.

Fig.2: Optimisation of the development system - Tefen's experience

The project management processes are aimed at optimising a single project through better resourcing, scheduling and budget management. Project management systems and procedures are commonly used in the industry although KPIs and control are far behind the level of utilisation in the wider manufacturing environment. This is not the case when we look at the overall R&D management process. The nature of creativity and innovation within the R&D process contradicts the need to follow procedures, measure performance and share knowledge.

Management of the R&D process becomes harder when companies try to integrate process development into high volume fabs and assembly/test sites. This raises a variety of issues in tool utilisation, operator efficiency, bottleneck management, cycle time management and layout.

Loss of tool utilisation is caused by frequent changeovers between manufacturing and engineering lots, extra cleans and tests, difficulties in tool dedication and the need for multiple tool models. Operators lose efficiency due to communication issues, conflicts of responsibilities and an imbalance between their capabilities and requirements.

Bottleneck management is more complicated as production tool capacity is affected by hard-to-forecast R&D loops. These create high numbers of process flows and metrology tool capacity is impacted by unbalanced usage. Line bottlenecks constantly shift unpredictably.

Cycle time is adversely affected due to unbalanced work in process (WIP), excessive amounts of lots on hold, a high number of lots in the fab, a higher number of changeovers and longer waiting times for test results. Layouts are required to be flexible enough to manage unknown processes, unknown tool sets, potential contamination issues and so on, which can result in a sub optimal fab tool layout.

Introducing 'operation style' solutions to the R&D process is a must in combating these issues. The basics of any solution will include a robust development procedure implementation, enabling information technology and measurement and control.

Overall development procedures

The first step in improving the efficiency of the R&D process is for the R&D organisation to adopt and implement an overall product/process development methodology. This methodology should enable the provision of documentation and deliverables easily and enable knowledge management and retrieval. An owner-customer system for deliverables management will enable the department to better control timely delivery and a structured method for setting milestones and gates (required criteria) per project type will enable better control. The organisational structure should be changed to better service the deliverables and areas of responsibility should be clarified.

An enabling information system should include the development of a database for each individual project including all required development procedures and outputs but limiting the deliverable list length per project size to ensure focus (Figure 3). The system should include identification of the customer-owner for each deliverable and allow budget and due-date setting for each deliverable.

Fig.3: Creating the required infrastructure

The system will provide an archive for development outputs and versions and will enable visibility of development outputs, early development versions, examples and mock-ups to all managers and participants of the project. The system should have a reporting function that will define the readiness status for each deliverable, allow generation of follow up/status reports and will send automatic reminders and alerts.

The third component to ensure efficiencies and better product development cycle time requires semiconductor IDMs to monitor their R&D processes to the same level of detail as for manufacturing processes.

A number of measures are needed for specification, system design, quality and reliability. Specification measurements would cover changes, requirements document approval date vs. plan, number or percentage of 'to be decided' (TBD) requirements, percentage of requirements verified and final release content vs. plan. System design measurements could include number or percentage of design review changes, number or percentage of iterations between design and test parties, number of open bugs/failures, repeat bugs/failures, first silicon success rate, number of engineering changes, number or percentage of design reviews vs. plan, project and timeline. Quality and reliability data could include percentage of testable requirements, dead on arrival (DOA), mean time between failure (MTBF) actual vs. predicted, system availability, field failure rate and product yield.

AngelTech Live III: Join us on 12 April 2021!

AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST) and will feature online versions of the market-leading physical events: CS International and PIC International PLUS a brand new Silicon Semiconductor International Track!

Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.

2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.

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We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.

Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.

Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.

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