TECHNICAL ALERT #5 FOR ALL USERS OF PRO COOL®

PRO COOL® vs. TWO COOL® Comparison
PRO COOL® process cost analysis software uses TWO COOL® cost of ownership analysis to estimate the cost of a sequence of process steps. TWO COOL® uses over 325 inputs to estimate the cost of operating a single process step. Manipulating this much information for a complete process is impractical, thus PRO COOL® uses the 13 TWO COOL® cost drivers, along with yield and production summaries for each process step. This simplification results in utilization driven differences between TWO COOL® COO estimates and PRO COOL® COO estimates for the same process step. In all cases, the difference is minimized for fully utilized process steps and increases as utilization decreases. The relative magnitude of these differences are illustrated in the following table:

 
PRO COOL®
Difference
TWO COOL®
Depreciation
 
=
 
ESH Preparation and Permits
 
=
 
Floor Space Costs
 
=
 
Labor
 
>
 
Maintenance
 
>
 
Material/Consumables
 
<
 
Moves & Rearrangements
 
=
 
Other Materials
 
<
 
Other Support Services
 
>
 
Scrap
 
=
 
Support Personnel
 
>
 
System Qualification Costs
 
=
 
Training
 
=
 

PRO COOL® treats these cost drivers in three different categories:

• Fixed costs are completely independent of production volume.
• Variable costs change depending on production volume.
• Time driven costs are variable costs that do not depend on production volume, but on    elapsed time.

Fixed costs include:

• Depreciation
• ESH Preparation and Permits
• Floor Space Costs
• Moves And Rearrangements
• System Qualification Costs
• Training

PRO COOL® treats these costs in the same way that TWO COOL® treats them and thus differences between these costs are negligible.

Variable costs include:

• Material/Consumables
• Other Materials
• Scrap

Scrap is also treated in the same way in PRO COOL® and TWO COOL® as a percentage of volume. Thus differences between these costs are negligible.

Materials costs may be underestimated by PRO COOL®, since annual material costs in TWO COOL® are defined as a cost per system. PRO COOL® converts these annual costs into a cost per wafer. In an underutilized tool group, PRO COOL® will pro-rate annual material costs but TWO COOL® will not. For example, if a tool processes 100,000 wafers per year and TWO COOL® annual material costs are $100,000 per system, PRO COOL® will treat that as $1 per wafer material costs with the following result:

Number Tools
Utilization
TWO COOL®
PRO COOL®
1
100%
$100,000
$1.00/wafer
$100,000
$1.00/wafer
1
50%
$100,000
$2.00/wafer
$50,000
$1.00/wafer
2
60%
$200,000
$1.67/wafer
$120,000
$1.00/wafer

Time driven costs include:

• Labor
• Maintenance
• Other Support Services
• Support Personnel

Some inputs in these categories are described in terms of hours per system. An example is scheduled maintenance. Others are calculated in terms of wafers per hour or hours per wafer, for example, total production hours. For hours per system type inputs, PRO COOL® may overestimate the per wafer cost impact, since it prorates the cost based on utilization, rather than number of systems.

This overestimate is illustrated in the following production labor example. In this case operating labor is a function of wafers processed, but production test is a function of number of tools used. We used both TWO COOL® and PRO COOL® methods to estimate production hours per week as a function of wafer volume, assuming that both operation and production test are done by the same individuals. The PRO COOL® method underestimates required production hours. This is illustrated in the following graph. In this figure, the points of agreement between the two curves are at full utilization.

required hours per week chart comparing TWO COOL® and PRO COOL®
Click Here to View Enlarged Image

Since the value of the cost driver for labor is fixed, the PRO COOL® method (which under estimates labor hours) prorates a higher cost per hour than TWO COOL®. Thus PRO COOL® overestimates labor cost for under utilized tools.

PRO COOL® vs. TWO COOL® Comparison Summary

Manipulating the 325 TWO COOL® inputs for each step in a complete process is impractical, thus PRO COOL® uses the 13 TWO COOL® cost drivers, along with yield and production summaries for each process step. This simplification may result in utilization driven differences between TWO COOL® COO estimates and PRO COOL® COO estimates for the same process step.

• PRO COOL® treats fixed costs in the same way that TWO COOL® treats them and thus    differences between these costs are negligible.
• Scrap is also treated in the same way in PRO COOL® and TWO COOL® as a percentage    of volume. Thus differences between these costs are negligible.
• Materials costs may be underestimated by PRO COOL® since it prorates annual material    costs by volume. This difference may be minimized by entering material, consumable,    and utility costs as a cost per wafer or cost per lot rather than as an annual cost.
• For time driven costs, hours per system type inputs, PRO COOL® may overestimate the    per wafer cost, since it prorates the cost based on utilization, rather than number of    systems.

In all cases, the difference is minimized for fully utilized process steps and increases as utilization decreases.

Techalert22-9810

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