Work in Progress

OSATs (outsourced assembly and test companies) currently handle the bulk of assembly and test activity for the worldwide semiconductor industry. These companies’ factories have a manual operation legacy: Decision-making is manual. Materials and WIP (work in process) movement is manual. Practically everything in these factories is done manually. In addition, OSAT factory environments typically present many physical constraints with respect to equipment layout, material carriers and storage. All of these constraints present challenges when trying to automate material handling in these factories. OSATs also operate with far smaller gross and operating profit margins than IDMs, yet the percentage of worldwide semiconductor product handled by OSATs is currently increasing from year to year while the IDM share is decreasing. The combination of increased business volume with lower margins encourages OSATs to automate their factories, but there are challenges that must be overcome. Technical challenges abound OSATs face many technical challenges when trying to automate production. First, installed legacy equipment in these factories is typically 25 to 30 years old. This older equipment was simply not designed to accommodate automated materials handlers. For example, access doors on older equipment make automated WIP delivery and pickup nearly impossible without significant modifications to the equipment. Second, these factories are not equipped with the infrastructure needed to support automation. To start with, most of this older equipment is not SECS/GEM compliant. (SECS/GEM is the semiconductor industry's standard equipment interface protocol for equipment-to-host data communications.) This capability must either be retrofitted to the existing equipment or some other means of extracting required data from the equipment – getting it from the PLCs controlling the equipment, for example – must be employed. Similarly, the WIP carriers currently in use – wafer carriers, trays, magazines, and the like – are not designed for automation. In contrast to the semiconductor wafer fab industry, it seems that almost every company in the OSAT domain has a different idea concerning what a carrier should look like. In particular, there’s no such thing as the standard 300mm FOUP (Front Opening Unified Pod), which carries wafers from one tool to the next inside of semiconductor fabs. The variations in carrier shapes, configurations, and even gripping handles in the OSAT domain thwarts progress in OSAT factory automation. How do you design a materials-handling robot with the grippers and flexibility needed to adapt to all of these different carriers? It’s a difficult question and an expensive proposition. OSAT facilities themselves are designed for human-based materials handling, not automated materials handling, simply because they were designed at a time when automation was not contemplated. As a result, the equipment in these facilities is packed very closely together (to reduce floor space costs), as shown in Figure 1. Figure 1: Equipment in a test facility is often tightly packed, which impedes the adoption of automated materials handling. It’s very difficult to add automated materials handling equipment at floor level or even at ceiling level in these OSAT factories, as is frequently done inside of a semiconductor wafer fab. You will not see AGVs (automated guided vehicles) moving around inside of legacy OSAT factories because there’s simply no room for them to move around. Tackling the challenges So, what can be done to handle these all of challenges? You must start by understanding the nature of the operations taking place inside of the factory. As stated above, most of these operations are currently performed manually. All of the decisions and the materials transport is performed by humans. There’s simply no way to transition from a fully manual operation to a fully automated operation in one jump. It’s too far a reach. A significant amount of work is needed just to reach the level where automated decision making is possible. Key systems must be added to enable this level of automation. Many companies tried and failed to automate assembly and test in OSAT facilities about 25 years ago. They failed because the required data could not be extracted from the equipment in use and, therefore, there was no data to drive good decision-making. Too many required systems were simply lacking. For example, when AGVs were added, one or two operators had to walk along with the AGV to tell it what to do. There was no benefit from the automation in this example. There was no successful path to automation at the time. Standards needed One of the major obstacles to automating assembly and test in OSAT facilities is a lack of standards for carriers, robotics, layout, and facilities. Many front-end standards exist. The SEMI-E82, SEMI-E84, and SEMI-E88 standards designed for semiconductor fab front ends might apply, but they need to be adapted to requirements for OSAT back-end facilities. In addition, OSATs have special needs that may demand new standards. This is a real opportunity for SEMI and its constituents. An architecture for full assembly and test automation involves four layers, as shown in Figure 2. Figure 2: Full automation for assembly and test involves four layers. Starting with the data layer at the top of Figure 2, a fully automated facility needs to have database systems in place that can supply all of the data needed for making smart scheduling and dispatch decisions. These databases then feed smart, automated scheduling and dispatch applications in the logic layer. The scheduling and dispatch applications then send control commands to the automated transport and materials controllers and the automated equipment handlers in the control layer. You need to start at the top of the diagram to put all of this automation in place. The automated equipment and equipment controllers need commands from the scheduling and dispatch applications, which in turn need data from the databases to make smart decisions. So it’s the data layer and the systems that feed data to this layer that constitute the starting point for the journey to full automation. A significant amount of simulation is needed to develop optimal facility workflows. These simulations are driven by data extracted from the databases. One of the frequently ignored facets of automation is the need for backup plans. For example, what is the backup plan when an AGV fails and cannot deliver material as scheduled? Simulation helps create contingency plans for such events. A case study Applied Materials has worked with assembly and test factories in deploying full automation. Towards this objective, the factories have worked on many modifications (physical and systems) to enable this automation. For example, a die-attach machine was retrofitted for automation by removing all of its equipment doors so that an AGV could load the machine and extract completed work. Additional modifications permitted the mounting of multiple magazines on the die-attach machine’s input and output to provide the buffering needed to smooth the flow of work through the machine. Finally, simple instrumentation and networking was added to the machine to aid in making WIP delivery and pickup decisions. These machine modifications addressed only the bottlenecks in this particular machine, but even these simple modifications helped to reduce the incidence of manual handling errors, such as the misalignment of magazines or trays. Modifications like these also reduce the need for human operators, which in turn reduces operating costs. Such types of incremental enhancements in automation capability have been implemented by leading-edge companies over the past few years. Conclusion Deploying full automation for assembly and test is not only feasible, it’s necessary for future profitability. OSATs must address the challenges of rising manufacturing volumes and thin margins by reducing manufacturing errors and increasing quality. (The quality requirement is increasingly driven by the automotive industry.) Trailblazing deployments have shown that it’s possible to automate these manufacturing lines successfully. While IDMs have a longer history for manufacturing automation, OSATs are now traveling along the same path due to their rising share of worldwide manufacturing volumes. On that path, they’ll need to develop experience and new standards tailored to their unique needs. Shekar Krishnaswamy is a senior manager at Applied Materials responsible for business development and pre-sales of factory automation products and solutions. He has over 27 years of experience in all aspects of semiconductor manufacturing including wafer fab manufacturing, bump, assembly and test. His specific areas of expertise are traditional industrial engineering methods as well as systems-related methodologies such as modeling, scheduling, dispatching and factory automation. Prior to Applied Materials, Shekar held senior technical and management positions at IBM, Motorola and AMD, including management of corporate operations research departments supporting factory and service groups. Shekar has a bachelor’s degree in mechanical engineering and a master’s degree in industrial engineering and operations research. Note: SEMI has a Smart Manufacturing Technology Community. For more information or to get involved, click here.

Part 1 of this article discussed the Memory Inventory Cycle Index and compared it with memory device sales and memory fab equipment investments. This article, the second of the two-part series, illustrates how the Memory Inventory Cycle Index starts to weaken before memory sales of the top three memory suppliers decline. It also shows how the Memory Inventory Cycle Index peaked in the fourth quarter of last year along with YoY growth rates for both memory sales and memory fab equipment investments.In addition to the weakening signaled by the Memory Inventory Cycle Index, memory suppliers are facing headwinds in the form of tariffs as mentioned in Micron’s most recent earnings call. The U.S.-China trade dispute could reduce Micron’s profitability; China granted a preliminary injunction to prevent Micron’s Chinese subsidiary from manufacturing and selling in China this July. However, it is very difficult to quantify the risk the tariffs pose to the future of the memory market.On the other hand, the YoY growth rate of semiconductor sales according to the World Semiconductor Trade Statistics is closely tied to China’s manufacturing sector as shown by the Purchasing Managers Index (PMI) New export orders and Orders in hand sub-indexes. Figure 3 shows that as the growth rate of new exports and order backlog slows, the YoY growth rate of semiconductor sales will be adversely impacted. As the largest consumer of semiconductors in the world, China will bear the brunt of the slowing market. Figure 3. Memory Inventory Cycle Index China manufacturing sector PMI’s sub-indices * RemarksChina PMI’s sub-indices are on the basis of the data published by NBS (National Bureau of Satistics of China). Also those data were calculated based on 12MMA (12-month moving average) to minimize seasonal fluctuation. The YoY growth rate of the 3-month moving average of semiconductor sales in China alone, China and Asia Pacific, and all regions showed additional declines in July (Figure 4). Monitoring the Orders in hand and New export orders sub-indices for China and China’s semiconductor consumption and WSTS sales revenue in China can help track the risk of trade disputes. Figure 4. YoY growth rate of semiconductor sales revenue in China and Asia Pacific * Remarks1) Regions as defined by WSTS’ Bluebook.2) Sales revenue were calculated based on 3MMA (3-month moving average value). A review of the relationship between the Memory Inventory Cycle Index, semiconductor sales, and memory fab equipment investment growth rates suggests we have passed the peak in the current cycle. However, bear in mind that the Work In Process (WIP) to Finished-goods inventory ratio has sharply increased since 2017 as shown in Figure 5. The increase in WIP inventory could be attributed to the increasing technical challenges associated with 3D NAND stacking and DRAM scaling. As a result, the proportion of finished-goods inventory in total inventory remained low until the second quarter of 2018, possibly implying that memory demand remained healthy in spite of the contraction modeled by the Memory Inventory Cycle Index. Figure 5. The proportion of finished-goods inventory in the total inventories * Remarks 1) All inventories data from 3 companies’ financial reports were calculated based on 4-quarter moving average.2) Total Inventory accounts for the sum of Finished-Goods, WIP, and Raw materials inventory.3) Company data complied by SEMI. The Memory Inventory Cycle Index has entered a period of contraction, which is supported by Micron’s weak guidance for its fiscal first quarter of 2019 (September to November). The outlook for memory sales and memory fab equipment investments reported by WSTS and SEMI, respectively, also suggests that a market correction is underway. While the low proportion of finished-goods inventory does not threaten the market yet, it should remind industry observers to view high WIP inventories with caution. Unlike past inventory cycles, the high inventory levels could burden the memory market in the absence of sustainable demand.Sungho Yoon is a senior market research analyst in Industry Research and Statistics at SEMI. SEMI China IC Ecosystem ReportLearn more about 30 new fab construction projects underway or planned in China in the newly released SEMI China IC Ecosystem Report. The research report is a comprehensive update and analysis of China's IC manufacturing ecosystem with charts, graphs, tables and maps.

Micron, one of the top three memory semiconductor companies, reported solid results for the fourth quarter of fiscal 2018 (June to August) to extend a multi-quarter string of strong growth. However, the company’s mediocre guidance for the current quarter has raised concerns that memory demand will start to slow.To shed light on this super memory cycle, which began in the second half of 2016, this article examines correlations among the top three memory suppliers’ sales revenue, quarterly inventory levels, World Semiconductor Trade Statistics (WSTS) market data, and memory fab equipment investments reported by SEMI.The Memory Inventory Cycle Index, which is based on financial data reported by Samsung, SK Hynix and Micron, is the difference between the year-over-year growth rates of sales (or shipments) and inventories. The index explains business cycle fluctuations such as expansions and contractions, trending up in expansions and declining in contractions. Figure 1 shows both historical Micron sales (blue dotted line) and the quarterly Memory Inventory Cycle Index (black solid line). To minimize seasonal fluctuations, both were calculated based on a four-quarter moving average of sales and inventories. Figure 1. Memory Inventory Cycle Index Compared to Memory Sales* Remarks1) Memory Inventory Cycle Index = YoY growth rate of memory sales revenues - YoY growth rate of memory total inventoris value on a four quarters moving average.2) Calculated memory sales and inventoris are based on Samsung, SK Hynix, and Micron public announcements.3) South Korea Won were converted to US$ based on the quaterly average value released by FRED.4) Companies’ sales data were calculated based on 4-quarter moving average.5) Company data complied by SEMI. As shown in Figure 1, the Memory Inventory Cycle Index has been declining since peaking in the fourth quarter of 2017, mirroring the previous two contractions – in 2010 and 2014 – in which memory sales slowed or stagnated after four quarters of the index decline. Accordingly, if this relationship holds between the Memory Inventory Cycle Index and sales, Micron’s sales will slow in the coming quarters and is consistent with Micron’s guidance for the current quarter. Moreover, the index suggests that the sum of three companies’ sales (the solid red line) will exhibit a similar trend of decreased growth in the coming quarters, which will impact the annual growth rate of global memory sales.WSTS recently increased its 2018 forecast for memory sales to 30.5%, up from 26.5% projected in June of this year. However, the 3-month moving average of memory sales shows that memory sales already increased by 48% YoY in the first half of the year, which means growth is expected to be lower in the second half of the year. Other signs pointing to a weaker end to the year include front-end equipment investments by the top three memory suppliers. SEMI is modeling an annual increase of only one percent for the year for these suppliers, with spending down 23% in the second half relative to the first half of the year.Figure 2 shows the historical trend of the Memory Inventory Cycle Index, the YoY growth rate of memory sales, and YoY memory fab equipment investments. The Memory Inventory Cycle Index increased faster than memory sales and fab equipment investments in the past two cycles. In the most recent memory cycle, these three indexes are moving in tandem, each peaking in the fourth quarter of 2017. Figure 2. Memory Inventory Cycle Index, Memory Sales and Memory Fab Equipment Investments* Remarks1) Both sales and memory fab equipment investments data were calculated based on 4-quarter moving average to minimize seasonal fluctuation.2) All data are from SEMI, except memory sales (WSTS) While overall memory sales continue to be strong this year, memory ASPs have shown signs of weakening right after the inventory index peak. NAND flash ASPs have been trending downward since the first quarter of 2018. With the recent inventory correction and short-term CPU shortage, DRAM ASPs are expected to soften in the fourth quarter of 2018. The looming memory market slowdown has memory makers adjusting their capacity expansion plans for the rest of this year. Some new capacity additions, especially for DRAM, have been pushed out to 2019. The memory inventory cycle index has to some extent foretold the slowdown of the memory market. In the second and final part of this article, we will discuss the correlation between the Memory Inventory Cycle Index and China’s semiconductor sales and Purchasing Managers Index. We will also look at the increasing level of memory inventory in the past few quarters and its composition including Work-in-Progress and Finished goods. Clark Tseng is director and Sungho Yoon is senior market research analyst in Industry Research and Statistics at SEMI. SEMI World Fab ForecastFor the latest worldwide memory fabs forecast including company details, please see the SEMI World Fab Forecast. The report includes quarter-to-quarter fab data from planning to production for both DRAM and NAND Flash companies.