Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1999-10-28
2003-10-14
Von Buhr, Maria N. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S100000, C705S002000
Reexamination Certificate
active
06633791
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to systems for controlling work flow in a manufacturing plant and more particularly to dispatching systems therefor.
2. Description of Related Art
Since the product mix and the process technology are complicated in a foundry comprising a semiconductor fabrication plant, different technologies are employed in different stages of the plant. Some of those stages can employ the same types of machines, i.e. equipment, for processing. Because of several factors, WIP (Work In Process) can easily pile up in a particular area on an occasional basis. For example, when one or more of the machines, in one or more of the stages, becomes unstable or where there is a resource arrangement bias that causes the production line to deteriorate into a non-linear status, losses result which comprise reduced wafer movement, increased cycle time, and delayed wafer delivery.
“Bottleneck Starvation Indicators for Shop Floor Control” IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING; VOL. 1., No. 1, (FEBRUARY 1988) pages, 147-153.
U.S. Pat. No. 5,396,432 of Saka et al. shows a production system and method of operating thereof.
U.S. Pat. No. 5,751,580 of Chi describes a fuzzy logic method and system for adjustment of priority rating of WIP in a production line.
U.S. Pat. No. 5,768,133 of Chen et al., which is commonly assigned, shows a WIP/Move management tool for a semiconductor manufacturing plant and a method of operation thereof.
U.S. Pat. No. 5,818,716, that is commonly assigned, of Chin et al. describes a dynamic lot dispatching required turn rate factory control system and a method of operation thereof for a semiconductor plant.
U.S. Pat. No. 5,826,238 of Chen et al., which is also commonly assigned, describes a method and a system for a daily target generation and machine allocation with priority.
SUMMARY OF THE INVENTION
Characteristics influencing the distribution of WIP are as follows: 1. variable product type; 2. manpower arrangement; 3. machine available time; and 4. dispatching
Indexes that are driven by dispatching of lot of work are as follows: 1. cycle time; 2. OTD (on-time delivery); and 3. wafer movement
Index of Dynamic Forward Loading (I
DFL
)
1. Using the Lever Principle, the remaining cycle time and consumed cycle time are used to generate the “Dynamically Forward Loading (DFL) Index (I
DFL
). The Intensity of the DFL Index (I
DFL
) is referred to as “&agr;”. There is a judgement factor used in making decisions pertaining to dispatching which is enhanced by use of &agr; and I
DFL
.
According to the “lever principle”, a lever is in a state of balance when the product of the right side force multiplied by the right side torque arm equals the left side force multiplied by the left side torque arm. Using an analogy to the “lever principle” and referring to
FIG. 5
, the elements are as follows:
Fulcrum of lever=Each specific lot/set of lots.
Force applied to right side Wafer quantity of each specific lot/set of lots.
Right side torque arm=Remaining scheduled cycle time counting back from the last stage, i.e. the QC-stage, to the current lot stage.
For example, referring again to
FIG. 5
, let us assume that there are two (2) lots remaining in production on the line. Those lots are L
3
and L
4
. Let us use a predefined comparison at stage ST
2
. The fulcrum of the lever separates the right and left sides=L
3
+L
4
.
A=Force applied to the right side=wafer quantity of sets of lots L
3
+L
4
B=Right side torque arm=Remaining scheduled cycle time counting from QC-stage to current lots L
3
+L
4
C=Force applied to left side=wafer quantity of sets of lots L
3
+L
4
D=Left side torque arm=Consumed scheduled cycle time counting from stage ST
2
to current L
3
and L
4
stages
Thus, when
(
A
×
B
)
(
C
×
D
)
=
1
,
the production system is balanced.
2. The I
DFL
Index immediately indicates any production dispatching bias caused by a factor such as an unstable machine or an inefficient deployment of manpower at each stage which would influence the scheduling and efficiency of the other stages in the manufacturing line.
A computer operated method is employed for determining the rate of dispatching lots for a stage on a production line. First, determine the weighted loading of work for each of the lots between the stage and a succeeding location on the production line by calculating a ratio of weighted progress of the lots as a product of time from dispatching of each lot and as a product of time to completion for each lot to produce an index for the stage. Then, adjust the rate of dispatching of the lots as a function of the Index.
In accordance with this invention the computer system calculates the WIP
i
for a stage ST
kk
for each lot Li in a queue of lots being processed in a production line between the stage ST
kk
and end point, where “i” is a positive integer representing the position of the lot Li in the queue, and where “kk” is a positive integer indicating the sequential position of the stage ST
kk
(location along the production line) from the beginning to the end of a predetermined portion of the production line. Calculate remaining scheduled cycle time (RCT
i
) for each lot Li. Calculate consumed scheduled cycle time (CST
i
) for each lot Li. Calculate (WIP
i
*RCT
i
) for each lot Li. Then, calculate (WIP*CST
i
) for each lot Li. Sum WIP
i
*RCT
i
for all lots Li of a stage. Sum WIP
i
*CST for all lots Li of a stage. Calculate the Index of Dynamic Forward Loading Intensity (I
DFL
) for each stage ST
kk
by dividing the (Sum WIP
i
*RCT
i
, for all lots of the stage) by the (Sum WIP
i
*CST
i
, for all lots of the stage) where kk is a positive integer indicating the location of the stage from the beginning to the end of the production line. Adjust the dispatching order of lots based on the rankings of the stages of the production I
DFL
line, with lowest I
DFL
ratings having priority.
REFERENCES:
patent: 3703725 (1972-11-01), Gomersall et al.
patent: 5396432 (1995-03-01), Saka et al.
patent: 5446671 (1995-08-01), Weaver et al.
patent: 5612886 (1997-03-01), Weng
patent: 5721686 (1998-02-01), Shahraray et al.
patent: 5748478 (1998-05-01), Pan et al.
patent: 5751580 (1998-05-01), Chi
patent: 5768133 (1998-06-01), Chen et al.
patent: 5818716 (1998-10-01), Chin et al.
patent: 5826238 (1998-10-01), Chen et al.
patent: 5838565 (1998-11-01), Hsieh et al.
patent: 5880960 (1999-03-01), Lin et al.
patent: 5889673 (1999-03-01), Pan et al.
Lozinski et al., “Bottleneck Starvation Indicators for Shop Floor Control,” IEEE Transactions on Semiconductor Manufacturing, vol. 1, No. 4, Nov, 1988, pp. 147-153.
Hsieh Chao-Yu
Hsu Fang-Jen
Lin Hsing-Chung
Lo Chiang-Chou
Ackerman Stephen B.
Jones II Graham S.
Rodriguez Paul
Saile George O.
Taiwan Semiconductor Manufacturing Company
LandOfFree
Dispatching system with dynamically forward loading (DFL)... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dispatching system with dynamically forward loading (DFL)..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dispatching system with dynamically forward loading (DFL)... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3167755