Data processing: financial – business practice – management – or co – For cost/price
Reexamination Certificate
1998-09-22
2001-06-19
Cosimano, Edward R. (Department: 2161)
Data processing: financial, business practice, management, or co
For cost/price
C705S007380
Reexamination Certificate
active
06249776
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to methods for allocating cost and more particularly to a causal methodology for costing product processing.
2. Description of the Related Art
The spiraling cost of semiconductor production has driven the industry to pursue greater economies of scale. This trend has forced a move from smaller, single partnumber fabricators to bigger, multiple partnumber, multiple technology fabricators. Costing is easy in a single partnumber fabricator and involves simply dividing total spending by the total units produced. Difficulties arise in costing wafer processing not as a result of complex processing or advanced tooling requirements, but rather as a result of diverse and extensive product offerings. Multiple partnumber, multiple technology fabricators must develop methodologies for costing different products. Traditional accounting systems track cost by department, not by partnumber, so developing a methodology which accurately assigns cost by partnumber becomes a key concern. Conventional cost-of-ownership models provide detailed cost data of equipment assets but not wafer processing costs. What is needed is a cost model that goes beyond classical cost-of-ownership data to provide accurate processing costs for such items as semiconductor wafers.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a structure and method for a wafer processing cost model. The inventive cost-of-processing model provides wafer processing cost data from raw wafer through final passivation and parametric testing. This new model goes beyond conventional cost-of-ownership data and captures more than just equipment costs because process, product, and fabricator costs are also captured. These costs are then causally spread to wafers via various methodologies. In order to do this, some historical cost problems had to be addressed, such as how to properly weight equipment usage and account for dedicated equipment requirements, deal with measurement sampling, incorporate idle time and contingency, and account for different photolithographic field sizes. Output from the model was fully validated against actual spending and tied to accounting data in order to assure a full dollar capture.
More specifically, one embodiment of the invention comprises a method of, computer system for, and computer program product for causally relating costs to products. The invention includes relating costs to a wafer having semiconductor chips comprising identifying resource costs for manufacturing the wafer including identifying equipment costs, computing load factors for each of the resource costs (the computing load factors for the equipment costs comprising determining a number of exposure fields on the wafer, computing a raw processing time for the wafer based on the number of exposure fields, and determining a percentage the raw processing time represents of a manufacturing time period on an equipment element, the equipment element having the equipment costs), producing weighted resource costs based on the resource costs and the load factors, (the producing weighted resource costs for the equipment costs comprising multiplying the equipment costs by the percentage), summing the weighted resource costs for the wafer, determining a volume of the wafer manufactured, and dividing the weighted resource costs by the volume to produce a weighted cost per wafer.
The process of identifying resource costs further comprises identifying partnumber costs, identifying technology costs and identifying factory costs.
Similarly, the process of identifying equipment costs comprises assigning costs of one or more of depreciation, spare parts, operator staffing, maintenance support, and vendor service contracts to the equipment element, and rolling up costs of related peripheral equipment to the equipment element. Also, the process of computing load factors for the equipment costs further comprises allocating indirect equipment costs, including at least one of power, deionized water, bulk chemical usage, air filtration, air purification, hoods, transfer equipment, air showers, minienvironments, gas-isolation boxes and other peripheral equipment to the equipment element. The process of computing load factors for the partnumber costs comprises allocating a portion of costs of one or more of yield analysis, systems setup, mask-set qualification, process tailoring, raw materials and engineering activities to the wafer based on an age of the wafer.
The process of computing load factors for the technology costs comprises allocating a portion of costs of one or more of process qualification, routing creation, recipe creation, process window definition, design of process controls and yield planning to the wafer based on an age of the wafer. Similarly, the process of computing load factors for the factory costs comprises allocating a portion of costs of one or more of administrative services, data processing, garment rooms, break areas and systems support to said wafer.
The process of identifying resource costs includes determining optional process costs, and the computing load factors includes computing load factors for at least one optional process based on a volume of the wafers subjected to the optional process.
The process of determining a volume of the wafer manufactured comprises substituting a predetermined full capacity volume for the volume of the wafer manufactured. Further, the process of determining a volume of the wafer manufactured comprises subtracting an amount of rework and scrap from the volume of the wafer manufactured. Also, the process of further comprising verifying the weighted cost per wafer.
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Bajuk Stanislav P.
Blouin Cathy L.
Blunt Gregory A.
Boldman Gary D.
Juba Robert C.
Cosimano Edward R.
International Business Machines - Corporation
Kotulak, Esq. Richard
McGinn & Gibb PLLC
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