HB-LED Standardization Update – March 2012
By Paul Trio, SEMI Standards
The SEMI HB-LED Wafer and Equipment Automation Task Forces met on Thursday, February 9 in conjunction with Strategies in Light in Santa Clara, California. The objectives were to provide progress reports on ongoing standardization efforts as well as to solicit inputs from the attendees. The event drew over 25 participants including representatives from: OSRAM, Philips-Lumileds, Oxford Instruments, Rubicon, Aixtron, Veeco, Silian Sapphire, Monocrystal, Entegris, Brooks Automation, Novellus, MKS Instruments, and KLA Tencor.
Given the amount of technical items to be discussed, both the Wafer and Equipment Automation Task Forces held working sessions earlier in the week (Feb 7) at SEMI Headquarters in San Jose, CA.
HB-LED Wafer Task Force
The HB-LED Wafer Task Force completed its development work on SEMI Draft Document 5265, Specification for 150 mm Diameter Sapphire Wafers for HB-LED Applications. The document covers four specifications depending on fiducial type (flat/notch) and thickness (1,000 um/1,300 um). The ballot was issued for the Cycle 1 voting period and members of the SEMI HB-LED Technical Committee are requested to review the proposal and cast their votes.
The ballot proposal was presented at Strategies in Light where inputs received from the audience suggested several opportunities for improvement. Document 5265 will be adjudicated by the North America HB-LED Technical Committee on April 5 in conjunction with the NA Standards Spring 2012 meetings in San Jose, CA.
In addition to their work on the 150 mm sapphire specification, the task force is also preparing their proposal for 100 mm sapphire wafers for HB-LED applications. Depending on the outcome of the 5265 ballot, the task force may incorporate the 100 mm sapphire wafer specifications if the ballot fails and is sent back to the task force for rework. Otherwise, it will be incorporated as part of a revision ballot for when the 5265 is approved and published. Meanwhile, the task force is also gauging interest for an HB-LED standard for 200 mm sapphire wafers.
Finally, the task force has initiated a wafer marking experiment where wafers (100 mm flatted, 150 mm notched) with front and back-surface marks (i.e., data matrix and OCR) will be subjected to various surface modifications (e.g., slicing, grinding, polishing, GaN Ep). The goal of this experiment is to characterize mark survivability, mark width and depth.
HB-LED Equipment Automation Task Force
The HB-LED Equipment Automation Task Force is comprised of a Hardware Working Group (WG) and a Software WG.
The Hardware WG is developing a specification for 150 mm open cassette. The working group plans to keep as many existing standards and dimensions from silicon based standards as possible to utilize as much existing hardware & equipment that will transfer to LED. Therefore, exterior features and dimensions are kept the same. However, the pocket size will be larger due to thicker substrates and accommodations for automated handling. Similarly, the specifications developed by the Wafer Task Force are also used as inputs to the cassette specification.
At Strategies in Light, the task force announced that it will move forward with the 16 capacity proposal. The task force will still need to perform detailed analysis to confirm their pitch assumptions as well as solicit inputs from device makers on their worst-case assumptions for handling wafers at 1.30 mm thickness and 1.0 mm warp. Nevertheless, the task force will begin drafting their ballot document for both metal and plastic type cassettes using the existing SEMI E1 standard as a starting point.
The Hardware WG is also developing a load port specification for 150 mm open cassettes. The SEMI E15.1 standard will be used as a starting point and edited for HB-LED. The document is intended to be compatible with minienvironments on equipment. Other sizes will be considered based on industry feedback
The task force plans to have the first draft of the 150 mm open cassette proposal in time for the HB-LED face-to-face meetings in early April (in conjunction with the NA Standards Spring 2012 meetings). Based on the inputs received, the draft will be refined and then balloted for the Cycle 4 voting period where it will be adjudicated at SEMICON West. Meanwhile, the first draft of the load port proposal is expected to be completed in time for the NA Standards fall 2012 meetings in late October/early November.
The Software WG was organized to develop factory communications standards for HB-LED manufacturing. A survey was deployed in early fall 2011 to solicit industry feedback on functional requirements for software interface in HB-LED:
- Today (e.g., trace data collection of system variables, equipment control, process program management, event/alarm reporting, etc.)
- Future (e.g., process job/control job management, complex wafer tracking in cluster, support for advanced process control, support for Interface A, protection against virus attacks & data misusage, etc.)
At Strategies in Light, the task force reviewed and analyzed the results of the survey. The responses received suggested the following:
- No IT security requested
- Mid to long term no AMHS features required
- Material ID and tracking of wafers, cassettes and process trays required
- Automation for process tray or process tray cassettes(s) is not required
- Preventive maintenance information from equipment to host
- Run to Run control, wafer-to-wafer tuning, RTD feedback control during run is required
The working group will be reviewing existing factory communication standards in order to determine whether these can be used as is, revise as appropriate for HB-LED manufacturing, or develop a new set of standards. Furthermore, the group will continue to liaise with the Equipment Information System Security (EISS) Task Force which was chartered in December 2011 under the Japan Information & Control Committee.
New Task Force on Impurities & Defects
In fall 2011, the HB-LED committee authorized the formation of the Impurities & Defects in HB-LED Sapphire Wafers Task Force. While the task force did not meet during Strategies in Light, it has met a number of times beforehand via teleconference. To date, the TF has discussed and identified known defects and inspection techniques to determine whether:
- the defects are relevant or important to HB-LED manufacturing
- are the inspection techniques relevant and how they can be applied to identify, measure or prevent the identified defects, and how they can be applied to benefit the HB-LED industry
The following defects were identified: LAGB “Low Angle Grain Boundaries” | Bubbles - Size, Location (surface vs. bulk) | Crystal - Homogeneity (distortion magnitude), Twins, Purity | Surface Purity.
The following inspection techniques were identified:
- OHT Polarized Light Inspection (Optical Homogeneity Technique)
- High Intensity Light Inspection
- Polarized Light Microscopy
- GDMS (Glow Discharge Mass Spectroscopy)
- Surface Profilometers
- Laser Interferometry
- EPD “Etch Pit Density”
- Automated Laser Defect Inspection
- Atomic Force Microscopy
- Acoustic Microscopy
These are only lists of known defects and inspection identified and discussed by the TF and will not necessarily be included in the standard(s) to be developed.
To learn more and/or to participate in these HB-LED task forces, please contact Paul Trio (firstname.lastname@example.org) at SEMI.
Upcoming Standards Meetings
The next NA HB-LED committee and TF meetings will be held on April 5 in conjunction with the North America Standards Spring 2012 meetings in San Jose, CA. Adjudication of ballot 5265 will take place at the HB-LED Committee meeting on April 5.
Participation in SEMI Standards and Voting on Ballots
SEMI uses the balloting process to obtain comments and votes as a means of achieving industry consensus on a proposed standard. If all negatives and comments on the document are resolved to the satisfaction of the technical committee and within the limits defined by SEMI Standards Regulations, the ballot passes. If certain parameters need further discussion and require additional changes, the ballot can be failed, revised, and then reballoted for voting.
SEMI Standards activities are open to all interested parties, but registration for SEMI Standards Program membership is required in order to participate in meetings as well as to vote on ballots. Also, by registering for the HB-LED Committee as a Technical Committee Member, members will receive important announcements (including the availability of ballots for voting) that are related to this group.
The SEMI Standards Membership Application Form is available at: www.semi.org/standardsmembership
SEMI Standards Watch, March 2012