Parallel Process Transferring System Ver. 2 Developed to Promote Post-Process Automation
DISCO Corporation (Head Office: Ota-ku; President Kazuma Sekiya) has upgraded the parallel process transferring system, which was exhibited as a reference at SEMICON Japan 2017, in order to make it easier to install in existing post-process equipment lines. This system promotes automation of post-processes while improving both the effective utilization of space and the transferring volume. Parallel Process Transferring System Ver. 2 will be exhibited at SEMICON Japan 2018 (December 12–14, Tokyo Big Sight.)
Automatic transferring* is popular in the front-end process, which performs processing on the entire wafer surface during semiconductor manufacturing, because the processing time is short and cassette used to store multiple wafers are transferred frequently. The post-process after dicing, which performs processing on individual die formed on the wafer, has a longer processing time than the front-end process. Thus, cassettes are usually transferred between processes by an operator.
As a proposal for the promotion of automation in the post-process, DISCO presented the Parallel Process Transferring System in 2017. This system allows for improved throughput, human error prevention, and a low-cost equipment operation rate improvement by adopting a method which enables the automatic transfer of wafers instead of cassettes. However, issues with the increased footprint due to the installation of on the backside of existing equipment and poor tracking performance for transfer volume fluctuations on the belt conveyor remained.
Those issues have been resolved in the Parallel Process Transferring System Ver. 2.
Figure 1. Parallel Process Transferring System Ver. 2
|AGV||：||Automatic Guided Vehicle
|Dedicated lane||：||Paths on which AGV runs
|Dedicated tray||：||Stores wafers during transfer
|Elevator unit||：||A unit takes each wafer from the cassette, loads/unloads them in the dedicated tray, and transports them to/from the AGV
|Processing equipment||：||Equipment that can be connected to the dedicated lane (Dicing saws, laser saws, etc.).
Features of Parallel Process Transferring System Ver. 2
- Utilization of Space Above the Equipment
- The footprint does not need to be increased beyond what the existing equipment requires because the lane for wafer transferring is installed above the equipment. Existing equipment can be retrofitted with this system. Thus, it can be installed to match the process and processing performance.
- Improved Tracking Performance for the Transfer Volume Fluctuations
- Because an AGV is used for wafer transferring, installation of the transfer path is more flexible than the belt conveyor system. By creating a layout which enables paths to cross or processes to be bypassed, transferring appropriate to the situation, such as processing high-priority wafers first, is achieved. In addition, transfer volume fluctuations can be controlled by the number of AGVs.
Advantages of Parallel Process Transferring System
- Improved Cassette Throughput
- Generally, the number of cut lines on the wafer surface increases for small chip dicing. Also, in order to decrease chipping, the cutting speed tends to be reduced. Thus, there are cases where it takes over six hours to process all the wafers in a ø300 mm/13-stack cassette using one dicing saw.
This system enables wafers from a single cassette to be processed using multiple dicing saws, leading to an improvement in the cassette throughput.
Fig. 2. Manual wafer distribution
Fig. 3. Conventional cassette processing
- Human Error Risk Reduction
- In order to minimize the processing time for one cassette, the operator is required to manually distribute the wafers from the cassette to multiple dicing saws. By automating the wafer distribution process using this system, it is possible to reduce the risk of human errors.
- Equipment Operation Rate Improvement
- Normally, one unit is responsible for processing one cassette. Using this system, single wafers can be distributed to multiple machines, allowing for parallel processing and making it possible to improve the equipment operation rate.
- Continuous Processing Using Multiple Processing Units
- The process for cutting wafers with Low-k film (a type of insulating film) involves the removal of the Low-k film using a laser saw, followed by a blade dicing process. By connecting both units to the dedicated lane, continuous processing can be achieved without the need for cassette transfer.
- No Additional Factory Construction Required
- Additional factory construction is unnecessary for installation because the system can be connected to the existing processing equipment.