Using Scheduling For Constraint Management
Talk
Title
in
Semiconductor
Manufacturing
Speaker
Name
Dilip
Gopi and
Roland Schelasin
Speaker Title
Industrial Engineering, Texas Instruments, Maine
Outline
• Wafer Fabrication Process Overview
• TI Maine Fab Overview
• Scheduling Methodology Overview
• Problem Statement
• Rule Definitions
• Benefits
2
© 2014 Texas Instruments Incorporated
TI Maine Fab Overview
3
© 2014 Texas Instruments Incorporated
Wafer Fabrication Process Overview
Wafer Fab
Re-Entrant Flow
Used with Permission from Clifford L. Henderson, GA Tech cliff.henderson@chbe.gatech.edu 404 385-0525
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© 2014 Texas Instruments Incorporated
TI Maine – Location
Aizu
Aizu Fab
Chengdu
Chengdu Fab
Miho
Miho Fab
Hiji
Hiji Fab
Hiji A/T
Portland
MFAB
Greenock
GFAB
Freising
FFAB
Taipei
TITL
Aguascalientes
TMX
Dallas
DFAB
DMOS5
DMOS6
SFAB
DHC
RFAB
DBump
Malaysia
TIM
TIEM
Baguio
Baguio
Stafford
HFAB
HBump
Color Management
Fab
Assembly & Test
Bump
© 2014 Texas Instruments Incorporated
Pampanga
Clark
MFAB – Maine – The Way Life Should Be!
Portland
© 2014 Texas Instruments Incorporated
TI Maine - Fab Overview
• 200mm SMIF w/Intercell Transport/Stockers
• 27 Technologies, 130-1500nm, 16-48 Masks
• 50,000 Reticles (10,000 In Fab)
• 700 Active Products
• 75k sq. ft. Clean Room
• In-House MES
• 7 x 24 Manufacturing with 4 Shifts
• Electronic Run Cards (STS):
Real Time Wafer Level Tracking
• Intelligent Stockers for Lot Dispatch
• Automatic Recipe Select/Downloading
• Automated “Feed Forward” Adjustment for
Advanced Process Control
© 2014 Texas Instruments Incorporated
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TI Maine – Mix and Capacity Overview
• Approximate Wafer Starts Mix
• 54% 350nm CMOS, Avg. 26 Patterns
• 26% 1500-130nm BiCMOS, 16-48 Patterns
• 20% 180nm CMOS, Avg. 31 Patterns
• Bottle Necks
• Design
– Photo
• Tactical
– EPI, Etch (Metal, Oxide), CMP, Diffusion (Clox)
– Technology + Process Module Sub-Capacities
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© 2014 Texas Instruments Incorporated
Scheduling Overview
• Scheduling is an important tool for
manufacturing and engineering since it can
have a major impact on the productivity of a
process.
• Helps minimize
– Production Time
– Costs
by explicitly telling the manufacturing
specialists what to run on which equipment.
• Production scheduling aims to maximize
efficiency of the operation
• The methodology presented uses scheduling
theory based on point allocation to dictate
lot-to-entity allocation and visualization for
one of the constraint modules in the factory
© 2014 Texas Instruments Incorporated
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Problem Statement
• 6 Chamber States (setup condition)
with 35 active production recipes
• In-flexibility to run everywhere
based on,
– Hardware
– Gas restrictions
– Recipe qualification on tools
• Chamber conditioning & test runs
needed when switching states
• Inability to meet required
productive hours results in cycle
time losses
 Chamber states are defined based on the gas
configuration used for Production
Chamber
State
Collector
As Lo
Emitter
As Hi
Collector
As Lo
Collector
Boron
Collector
As Lo
Collector
As Lo
Collector
As Lo
Collector
P
Collector
P
Collector
P
Collector
P
N Base
Base
P Base
Base
P Base
Base
Emitter
Base
N Collector
P
Collector
As Lo
N Base
Base
Emitter
As Hi
P Base
Base
N Base
Base
P Collector Boron
N Base
Base
Collector
Boron
Collector
Boron
Collector
Boron
Collector
P
Collector
P
Collector
P
Collector
Boron
Collector
Boron
Collector
Boron
Layer
EPI01
EPI02
Released Hardware
© 2014 Texas Instruments Incorporated
EPI03
In Qual
EPI04
EPI05
EPI06
States
Qualified
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
4
4
4
4
5
5
5
5
5
5
Not Qual'd As Hi Restrict
Week
Date
Week 1
Week 2
© 2014 Texas Instruments Incorporated
Week 3
1/9/13
Week 4
60
50
0
40
20
0
12
9
Down
33
( 6 Months Data)
18
11
Idle
10
7
Passing Lane
Run PCRC Qual
100
Running Qual
19
Idle - Down Qual
26
Idle
27
Down Process
150
Wait for Lot Clean
237
Idle - Wait for WIP
EPI06
Wait for Qual Data
17
Down Process
80
Chamber State Change
Re-Measure
Leakup PM
250
Down Maintenance
Goal
Hours/Week
EPI05
3/9/13
3/10/13
EPI04
3/11/13
3/12/13
EPI03
3/13/13
3/15/13
EPI02
3/14/13
EPI01
1/8/13
1/7/13
Productive Hours/Day
1/6/13
1/5/13
1/4/13
1/3/13
1/2/13
1/1/13
12/31/12
12/30/12
12/29/12
12/28/12
12/27/12
12/26/12
12/25/12
12/24/12
100
12/23/12
Sum120
of Time (Hrs)
12/22/12
E10 State
12/21/12
12/20/12
Productive Hours
Problem Statement (Contd.)
Tool
Average Hours/Week
200
Equivalent Loss of 1 Tool due to
Components of Chamber State Change
75
Qual
Proposed Model – Tools by State
4QCY12
1QCY13
2QCY13
# of Tools Assigned
4.0
# of Tools
3.0
• Reduce Chamber State
Changes
• Eliminate associated Idle time
with State Changes
2.0
• Use Passing Lanes to keep
recipes Qualified
1.0
0.0
As Hi
As Lo
Base
Boron
P Hi
P Lo
Preferred Tool Model
Primary Secondary
Tool
State
State
EPI01
As Lo
Boron
EPI02
As Hi
Base
EPI03
Base
Boron/P
EPI04
Base
As Lo /P
EPI05
Boron
Base
EPI06
Base
As Hi
© 2014 Texas Instruments Incorporated
• Each Tool to have a Primary
and Backup State
• EPI Scheduler to define State
Changes based on WIP and
Look ahead functions
• Reduce downtime associated
with state changes
What is a WIP Scheduler?
• The WIP Scheduler is used to schedule a lot to be loaded into the tool
• The WIP Scheduler uses a set of rules that have been set up for each
entity type
• The WIP Scheduler schedules a run by using the rules and other
factors on each tool
• The WIP Scheduler and Dispatch are Different!
– Dispatch only shows work, and the order is based on dispatching rules:
• Slack time
• Priority lot (Hot, Hand carry, etc.)
– The WIP Scheduler sees what can run on a tool and determines what lot or
group of lots (batch) should run next based on the rules
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© 2014 Texas Instruments Incorporated
Rule Definitions
• Points are assigned for each rule (Low, Med, High)
• Lot-based Rules
– Priority, Lateness, Static
• Lot / Entity Rules
– “Cost” of changing Chamber State
– How many tools can run the Recipe right now?
• Fewer tools means MORE points
– MTTD consideration for batches with inspectable lots
© 2014 Texas Instruments Incorporated
Maximization Function
Where Rules are defined based on,
• Lot Priority
• Lot Lateness
• Lot Slack Time
• Lot Inspection
• Tool Chamber State
• Tool Count
• Tool Ready
• Tool State, etc.
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© 2014 Texas Instruments Incorporated
EPI Rule Set
Type
Name
Min
Points
Mid
Points
Max
Points
Min Text
Mid Text
Max Text
BATCH
PRIORITY
0
300
500
no priority
Medium Priority
High Priority Lot
BATCH
LATENESS
100
200
300
3 days late
7 days late
>10 days late or push
it
BATCH
STATIC
100
300
500
24 - 48 hours
48-72 hours
>72 hours
BATCH
STATIC_HRS
0
0
1
BATCH
INSPECTION
100
300
500
Inspectable 50-125
Inspectable 125-500
Inspectable >500
ENTITY
TOOL_COUNT
0
0
300
3 tools
2 tools
1 tool
ENTITY
QUAL
EXPIRATION
100
300
500
>7-14 days
2-7 days
<2 days
ENTITY
RUNNABLE
0
300
500
Cannot Run
Allowed but must
Qual
Can run Now
ENTITY
STATE_CHANGE
0
0
0
© 2014 Texas Instruments Incorporated
hours static
Value from table
State Change Table
From
To
State
As Hi
As Lo
Base
Boron
P Hi
P Lo
As Hi
0
100
0
100
100
As Lo
5000
1000
100
100
100
Base
100
100
100
0
0
Boron
10000
100
100
100
100
P Hi
5000
100
100
100
0
Risk Levels
0
100
1000
10000
Just do it.
Can be handled with standard prep recipe (hours)
Extended chamber prep time and qualification (days)
Don't do it.
© 2014 Texas Instruments Incorporated
P Lo
5000
100
100
100
0
Scheduler Breakdown
Current
State
Projected time
when tool will
finish current
lot(s)
Points Score
based on Rule
Set
© 2014 Texas Instruments Incorporated
Benefits
• 34% increase in Productive Hours
• Chamber State Dedication
Helped,
–
–
–
–
Increased Availability
Increased Utilization
Increased Labor Productivity
Reduced number of State
Changes
– Reduced Quals
– Gas Savings
Scheduler Online
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© 2014 Texas Instruments Incorporated
Benefits (Contd.)
• Empowerment to the shop floor
• Engineering Productivity Improvement
• Gave the floor a better visibility of what needed to run next
• Look ahead of when the next lots are needed on what tool
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© 2014 Texas Instruments Incorporated
Q&A
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© 2014 Texas Instruments Incorporated