AMHS(Automated Material Handling System in FPD Fab

‘Automated Material Handling System in FPD Fab’ is followed by the first “Automated Material Handling System of 300mm semiconductor Fab”, the change in the Generation (Generation) of the TFT-FPD production line can be applied to the system, otherwise, the actual production line trend for the change was created mainly. Plan, design and simulation analysis of the Automated Material Handling System and Fab layout to be created in the next time, the overall flow and consideration for the configuration of the simulation techniques, statistical analysis and Fab for the optimization of the automatic conveying system in the semiconductor and FPD Fab is what this is written about.

1. Introduction
  Changes in the automatic transport system in the FPD Fab requires a different change compared to changing from 200mm to 300mm in the Semiconductor industry. Changes in the Automated Material Handling System in the conventional Semiconductor Fab which is only a change in the performance improvement and operating method of the automatic conveying system considering the efficiency in terms of production without changing the shape of the Fab layout required, in the case of FPD Fab is what are the corresponding system according to the Change of Generation of the FPD, and to configure an efficient layout when configured as such a system that the focus is aligned.
Changes in the FPD generation means a change in Glass size for FPD. The recent change in the AMHS for the generation of 10.5 G in the 4.5 generation line can be said to have been developed and executed annually. This sudden change is a challenge for the production equipment industry to respond to the production line and the development of the corresponding technology in the AMHS equipment industry in the shortest time. The production line in the FPD Fab has a similar feature to the Semiconductor, but in terms of processes, the production equipment side has a completely different feature. For Semiconductor production equipment, each production device has become a goal to develop a unique equipment model, in the case of FPD production process equipment, the size of the base material of the Glass production is larger, beyond the equipment development limited to productivity and reliability, the mechanism can be applied whether or not the verification period for the target yield is a very limited state. In this situation, each equipment industry is putting more cost and manpower into technology development. For the requirements for this short-term technology development and for the application of the actual production Fab each manufacturing equipment and the automatic conveying system, as the size of the Glass is larger in seconds, while not applying the conventional modular equipment form to be applied differently depending on the change of the layout of each Fab the flexibility of the equipment itself is greatly improved, while the verification period of the reliability is very small, securing the reliability that was for granted now has become a mandatory check.

The size and weight of the cassette for FPD to be transported to the automatic transport equipment according to this flow is not applicable from the basic automatic conveying system according to the diversification (non-standardized) for each Fab also appear. Efforts to minimize the buffer space in the clean room FPD Fab in accordance with the area that is used as compared to the quantity required to secure the transfer system of the buffer space is also applied in a different direction than the semiconductor.

[Figure 1] Size Difference of TFT-FPD According to Generation (Example)

2. Automated Material Handling System corresponding to Layout of TFT-FPD Fab
The layout of the FPD Fab corresponds to the size of the Glass, as shown in Figure 1, the recent production system is completed from 4.5 generation to 8.5 generations, but recently applied a mass production regime up to 10.5 generations, but because the TV market as the main goal of the TFT-LCD of magnitude competition can be mass production competitiveness has recently become the leading role of OLED new display industry.

The OLED (Lgid OLED or Flexible OLED) display is the current mass production equipment technology and yield in terms of production technology due to the difficulty of the size of the competition to raise more stable than the yield of the magnitude (6G Half, 1500 x 1800) to focus on planning and executing the production line. However, until recently, it has been understood as a poorly producted yield compared to the TFT-LCD situation. This change in size is not to apply the existing 6G system in terms of the automatic conveying system (Macro moves), rather than to apply the fine conveying system (Micro moves) granular to the new process and is actually applied.

By omitting the space and time for movement in-line in the process equipment buffer (Stocker) in order to eliminate this part in the overall layout as the moving passage between the production equipment and the buffer is required at least two to three times the space of the transport unit it was introduced a concept that can be obtained by improving the production efficiency of the two costs.

In particular, the Stocker in-line screen of the process equipment, such as a consistent process is made part and the inspection process has become an essential alternative in the TFT-FPD production line. [Figure 2] Not only in terms of simplification of inter-process logistics, the result is consistent with the ultimate purpose of the production line, minimizing the material between processes (WIP: Work In Process). However, this changes the efficiency of the Robot Crane in the Stocker used in the Buffer increases, if a specific length or more Stocker as an alternative to the breakdown when the operation of the two Robot, by operating the other one Robot during the meeting and failure of the required Cycle-Time was presented as an alternative to the case where the overall production line is stopped.

[Figure 2] Changing the concept of inline (In-Line) in the Bay concept

3. Stocker System and Inline in Process equipment
  Stocker system and the part that can be applied in-line of the process equipment is a large part of the inspection process, such as a certain or all Lot without the consistent work, only a portion of the logistics can be applied to the process. In this case, the Stocker system is responsible for the function of having a function of the characteristics and temporary storage of the logistics transfer equipment. Logistic transfer to the inline Stocker is used, such as the existing AGV, RGV, Conveyor or OHS. What system to choose will be selected in consideration of how to configure the main system in the structure of the overall Fab and the distance between the adjacent process and the arrangement of other equipment.

[Figure 3] In-line processing equipment in Stocker

The enlargement of the glass is not only affecting the Stocker system and the process equipment for the buffer, it is also subjected to In-line screen between the factory equipment. Although the characteristics of the TFT-FPD process is very simple compared to the Semiconductor, the actual repetition process is the same meaning that 4Mask the main process proceeds 4 times, the contents of the actual process may be the same. Therefore, a number of equipment may be used in line with the main process equipment and the cleaning process comprising a main process before and after. The layout of the production line of the TFT-FPD in this concept can be said that the range of many changes and applications are applied, depending on the system preferred for each production vendor out of the form of Interbay and Intrabay, such as Semiconductors.

[Figure 4] In-Line processing equipment in Stocker

[Figure 4] Below is a Stocker system that has an interface for the Stocker system and external logistics transfer, which is applied when necessary. Non-clean room located at the bottom of the clean room through the inside or outside of the Stocker system to secure the storage space on a limited layout according to the size of the buffer as compared to the number of buffers required in accordance with the large-sized disc Glass of FPD the utilization of the area (Sub Fab) was increased. In order to take advantage of the non-clean room area to protect from the fatal fine Dust (Particle) Glass to secure a partial cleanliness to act as a Clean room, such as cleaning Tunnel. In order to intermittent logistics feed between the close Stocker Upper connection Conveyor is widely used.

[Figure 5] Expansion with Peripheral Systems using the Stocker System

With respect to the interlayer utilization of the Fab Building can be installed in one Stocker system up to the bottom of the Stocker system, which has been considered sufficiently prior to the Sub Fab. The upper part of the system is located in the Clean room area, the bottom portion of the Robot is located in the non-clean room area. Therefore, the system should be designed with sufficient consideration of the flow of the system inside the tank and the maintenance of the medium against the bottom portion of the Stocker system.

[Figure 6] Extended Taller Stocker System to Sub Fab

4. Classification of Automated Material Handling System
Automatic conveying system can be classified as a sheet method for transporting a single sheet of Glass itself and the system for transporting the Cassette itself. Automated Material Handling System for transferring the cassette itself, but in terms of operating the Fab as a basic system has been used in the existing can be used without resetting the Fab operating software and processing of each production information that was used in the existing separately, if the transfer of the Glass to the sheet is to be different from the basic production information Lot management. The International Semiconductor Equipment Standardization Organization SEMI (Semiconductor Equipment and Materials International Standard), but the regulations on Lot tracking on the transfer of the sheet, the actual application is not yet widely applied.

Below is a Stocker system for the feed system OHS, and Overhead Conveyor systems, temporary storage and transfer to the installation and transfer to the clean room for AGV, RGV, MGV and the top of the clean room when the cassette to the transfer body it can be classified.

4.1 Cassette Conveying Method

These are the advantages and disadvantages for systems corresponding to cassette conveying methods.

AGV Transport Method
1. Characteristics

– Above-floor transporting method
– No attachment to the floor
2. Advantages
– Root for AGV transporting can easily be changed.
– Able to use multiple Vehicles to convey a large amount at a time
3. Disadvantages
– Need charging during the transporting process
– Need secure railway for AGV, requires flat surface
– Can affect air current inside the building
4. Operation Control
– Can drive both ways and prevent crashing
– Multi lane passing travel (high vehicle assignment)
– Operation of Battery charging station for quick charging

RGV Transport Method
1. Characteristics

– Above-floor transporting method
– Follows the rail that is attached to the floor
2. Advantages
– Transporting can be done very quickly.
– Short cycle time
– Can be used with the MGV in under-floor track
3. Disadvantages
– Cannot easily change Transport Root of the vehicle
– Need to construct rail on the floor
– Can affect air current inside the building

OHS Transport Method
1. Characteristics

– Ceiling transporting method
– The vehicle operates along the rail attached to the ceiling.
2. Advantages
– Can transport at a high speed, can easily add extra vehicles.
– Can be kept clean because it transports along the ceiling.
– Can use space effectively.
3. Disadvantages
– Need to secure the ceiling.
– Need to consider cleanliness of area under the transporting area.
– Need to consider vibration because it is attached to the ceiling.

Overhead Conveyor 및 Clean Tunnel Transport Method
1. Characteristics

– Used between specific equipment or between Stockers.
– In case of Clean Tunnel, it is a Under-floor transporting method.
2. Advantages
– In case of Overhead Conveyor System and upper Clean Tunnel, it can be placed in the non-clean room area at the lower part of the clean room, therefore the clean room can be used effectively.
3. Disadvantages
– Expensive.
– Needs an independent maintenance equipment to keep the Clean Tunnel clean.

MGV Transport Method
1. Characteristics

– Above-floor transporting method
– The cassette is transported to the next process by people
2. Advantages
– If a problem occurs in the Automated Material Handling System, the MGV Transport method is the backup method.
3. Disadvantages

– Restricted transporting route (Difficulties when using other systems simultaneously.
– Low efficiency
– Problem in maintaining cleanliness because it is carried by people

4.2 Substrate Transfer Methods
  By the vibration generated during operation due to the structural problems of the existing clean room weight increase according to the enlargement of the conventional AMHS when the glass is large, giving a lot of influence on some process equipment. In particular, to block the vibration of the outside of the process equipment installed in the dust-resistant, but essentially in accordance with the increase in weight of the AMHS and the large Glass cassette itself is increased to a few hundred kilograms has a tendency to become difficult to supplement books such as conventional.

The seventh generation after the sixth generation, more specific measures for the Substrate Transfer System has been proposed, but a portion embodied in a large part in some related industries, the application of the current production line is almost none, but the next generation of seventh generation it is seen to be seriously considered.

First, Minimalizing loading/unloading area problem (minimum constructing area)
Second, Small Lead Time
Third, from the original Job shop layout, it is considered to be a required condition about adapting the Flow shop layout, which results in making the clean room bigger.

Based on the three problems in the initial review of the Substance Transfer system was conducted research on the method of vertical transfer to complement the book. For the vertical transfer system, even though the amount of space required for the transfer systems is reduced, the overall factory equipment itself proceeds to the process horizontally without proceeding to the vertical process, so additional devices like many constraints on the interface between the processing equipment tray are needed as when performing the process is required vertical transfer method was considered limited.

Conveyor Transport Method
When Substrate transferring Glass, if using the original roller type or belt type conveyor, these need to be considered.

– Hanging out when glass is vertically positioned  If you put a roller in the middle to prevent flapping down, more area is touching each other.
– If glass is transferred with another equipment, more impact will occur at the edge of the glass
– Compared to the transferring of the cassette, the impact on the glass is absolutely necessary.
These problems result in less frequent use of this method.

Pneumatic Transport Method
As an answer to the problem of Substrate Transfer System, there are a lot of research going on about using air resistance to reduce glass friction, which is a seventh generation Transfer System. Seen as a focus on the market of FPD TV in recent generations, the larger of the Glass according to the large Panel of the followed by one, the superscreen of the Glass after the seventh and eighth generation is a lot of difficulty in whether the application of AMHS equipment of the overall process equipment it is expected to be.

– Tunnel-shaped Transfer route is connected to the processing equipment using fresh air.
– Glass is transferred using air resistance (floating)
– A thin layer of air is created between the bottom of the glass and the top of the transfer tunnel.
– There is no factor that can damage or pollute, enables quick transfer, also transferring in air does not delay.
– Similar structure and function to the Mini-environment which helps maintain cleanliness and reduces construction fee.
– Consists the control unit and the track unit.

The picture below is our Substrate Transfer System, the demo system of the FTS(Flat Panel Transport System) and it is made so that the sixth generation size glass can fit.

[Figure 7] FTS Demo System, the Sixth Generation Substance Transfer System

  In order to adapt our own Substrate Transfer System, we did a simulation about whether the Substrate Transfer System satisfies the capacity of the cassette transferring production line. The results were for the Substrate Transfer System to transfer the glass, less than 0.5M/sec was enough, further problems appeared in the interface and throughput of the equipment.

[Figure 8] FTS Simulation using the AutoModTM
[Figure 9] FTS and Process Equipment Combined

In order to adapt the FTS needs a lot of research, the interface technology with the process equipment and the lot tracking technology was tried from past Semiconductors.

[Figure 10] Substrate Transfer System’s SEMI 999 (Substrate Tracking Method)

5. Conclusion
The AMHS in the production of Fab doesn’t just work with a specific system. How the people want to configurate the Fab, by the results of favor between companies or the experience of using the system is changing.

The AMHS can respond to the requirements because it has flexibility of solutions that each conveying system has as well as a variety of interface technology.

The adaptable systems for AMHS in different generations corresponds to the size of the glass.
5th generation FPD Line: Stocker, AGV, RGV, OHS, Conveyor, Lifter
6th generation FPD Line: Stocker, AGV, RGV, Conveyor, Lifter
7th generation FPD Line: Stocker, Cassette Conveyor, Lifter, RGV, Substrate Conveyor (Partially)
8.5th generation FPD Line: Stocker, OHS, OHT, RGV, Full Flow shop layout using Conveyor

After the 5th generation, the research of Automated Material Handling System for the 8.5th generation should be done now, and this is not just for the AMHS, but the whole of Industrial Engineering OR(Operation Research) and Fab operation needs it as well.

JT Shin / CEO

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