Measuring Critical Parameters of Perfluoroelastomers Used in HVM at Advanced Process Nodes

By Paul Trio, SEMI

The Semiconductor Components, Instruments, and Subsystems (SCIS) is a SEMI technology community chartered to address process-critical components challenges to meet the demands of high-volume manufacturing (HVM) at advanced process nodes. SCIS brings together all stakeholders that are driving yield improvements through the very last frontier of component and hardware defect reduction.

At both strategic and tactical levels, SCIS focuses on mitigating excursion events and improving measurement standards for known excursion risks. Its activities are structured around characterizing important parameters affecting processes and impacting yields and developing test methodologies to measure them. Each key parameter addressed are agreed upon by all stakeholders and must be traceable in reducing defects.

SCIS brings together all stakeholders that are driving yield improvements through the very last frontier of component and hardware defect reduction.

These test methodologies provide a measurable way of holding stakeholders accountable. Focused on defining consistent methodologies for measuring defects, SCIS activities are inherently pre-competitive in nature and therefore do not necessitate discussion or disclosure of any sensitive IP.

Critical Components and Traceability

Six (6) SCIS subteams develop defect parameters for the following components: seals and valves, RF generators, showerheads, dry pumps, gas delivery, and liquid delivery systems. A seventh (7) SCIS subteam is developing an information exchange model that would enable an industry-standard parts traceability process.

 

Due to certain interdependencies between seals and valves, the SCIS Seals and Valves teams jointly focus on these components but also carry on their separate activities.

Seal Leak Rate

Seal failure can generate defects through atmospheric leaks into process environments or from degraded seal material. Therefore, a standardized way to measure a seal’s ability to hold vacuum when exposed to elevated temperatures and/or process and clean chemistries needs to be developed.   

 

The Seals team is approaching the problem by developing a method to effectively measure leak rate that is then performed on a test jig.  The test jig attempts to simulate the environment that the perfluoroelastomer is subjected to while the proposed test method itself attempts to simulate the process conditions the seal is exposed to. The test jig, which is also being spec’d by the SCIS team, will help ensure that the test is repeatable and achieves consistent results while giving seal manufacturers the freedom to determine the type of seal material to use depending on the customer application.

 

Seal Test Jig

 

Once the preliminary measurement recipe has been detailed, the group will move into validation of the proposed method and test jig in partnership with a test lab or testing organization. Ultimately, the seal leak rate test method and test jig spec will be transitioned as formal SEMI Standards development efforts.

Valve Marathon Testing for CIP Elastomers

Currently, there is no marathon testing of valve performance after new elastomer material types are introduced to an already designed marathon-tested valve. This is a valve measurement gap today.

Currently, there is no marathon testing of valve performance after new elastomer material types are introduced to an already designed marathon-tested valve. This is a valve measurement gap today.

The Valves team is working to improve current marathon testing of new design valves by valve suppliers and to introduce marathon testing for elastomer-based CIP (continuous improvement process) valve redesign that is applicable for all elastomer types.

The proposed method will apply to wafer transfer valves, isolation valves, and pressure control valves.  While not addressed in the initial iteration, the group will eventually include considerations for exposure to harsh chemistries. The proposed method will not address marathon testing in OEM development cleanrooms and/or fabs, but would be considered as part of future work.

Similar to the test method being developed by the Seals group, the proposed test method for valve marathon testing for CIP elastomers will ultimately make its way to the SEMI Standards space for formal standards development.

Completed Standardization Efforts on Perfluorelastomers

The leak rate and marathon testing methods are not the SCIS Seals and Valves group’s first forays into standardization.  The group has already published two seal-related efforts into the SEMI F51 Standard.

The Seals group completed its work on total organic testing (TOC), surface extractable metal contamination, and ash metal analysis. The work led to the major revision to SEMI F51, Guide for Elastomeric Sealing Technology, which took effect in the November 2015 version of the standard.

The group then shifted its focus on cleaning, packaging, and handling of seals. While process controls are established to ensure dimensional accuracy and specification, there were no industry standards on how seals are cleaned, packaged, and handled after they are manufactured. The lack of industry alignment on these final production steps often results in the introduction of contaminants into the wafer manufacturing process. The Seals group worked to update F51 by provide industry guidance on best known methods for seal cleaning, packaging, and handling.

While process controls are established to ensure dimensional accuracy and specification, there were no industry standards on how seals are cleaned, packaged, and handled after they are manufactured.

The updates introduced guidance on seal information provided in the packaging labels (e.g., material, dimensions, production/cure date) as well as the bag (e.g., inner vs outer bag) in which certain label information should be placed. The updates also addressed the gaps in handling and storage conditions to help prevent the seals from being compromised during and after shipment to customer sites. Finally, the group incorporated measurement methods for seal cleanliness during handling and packaging. These updates went into effect in the September 2017 version of SEMI F51.

Standardization of SCIS Activities

SCIS development efforts have been seals-centric.  However, many other SCIS groups have completed their preliminary test method development and are now in the midst of ushering their activities into the SEMI Standards space for formal development.

 

RF Generator Transient Response

The SCIS RF group was chartered to focus on defectivity parameters related to RF generators. The group has been focused on measuring the transient response of RF generators used in semiconductor equipment. The SEMI E135 Standard already provides a test method for RF generator transient response. However, the SCIS RF group determined that the Standard needed significant updates to reflect real-world conditions and help determine the RF generator’s worst-case condition response time.

The SCIS RF group determined that the Standard needed significant updates to reflect real-world conditions and help determine the RF generator’s worst-case condition response time.

SCIS RF efforts were transitioned to SEMI Standards for formal development when the RF Measurements Task Force was created in early 2017. Under the North America Chapter of the Metrics Technical Committee, the task force developed ballot 6184, which resulted in a major revision of SEMI E135. The ballot proposal draft was completed in late 2017, with support from the Japan RF Measurement Liaison Task Force, and passed technical committee review in April 2018.  Because there were additional technical and editorial modifications to the original proposal, a Ratification Ballot will be issued as part of the SEMI Standards process. Subsequent procedural reviews are planned. If cleared, the updated version of SEMI E135 could be published by SEMICON West 2018.

 

Pulse Testing of Gas Valves

When valves used in gas supply lines and tools are switched several times, the switches generate particles that contribute to contamination. Therefore, the number of particles added per switch needs to be determined. The SEMI F70 standard provides a solid foundation for determining particle contribution of gas delivery systems from a system-level perspective. However, from a component perspective, because the current method does not measure contamination during switching, the particles generated during switching may be undetected. The SCIS Gas Delivery group is developing a proposal that addresses this gap and will lead to the creation of a new subordinate document to SEMI F70.

 

Effects of Switching in Gas Lines

 

Prior to pulse testing activity, the SCIS Gas Delivery group completed its work on measuring metal and hydrocarbon elements in gas delivery systems. Driven by the Filters & Purifiers Task Force, under the North America Chapter of the Gases Technical Committee, ballots 6290 and 6291 were issued for voting in late 2017. Based on inputs received on the ballot in spring 2018, the task force will continue to refine the proposals and resubmit for voting by SEMICON West 2018 (July).

 

Sound Level Measurements of Dry Pumps

Noise is characteristic of dry pumps. Manufacturers generally offer ways to suppress or attenuate noise depending on customer requirements or applications. However, noise can also indicate a defective pump or an impending pump failure. Therefore, a standardized way to measure pump sound levels can help determine whether a pump is operating in accordance with supplier specifications.

A standardized way to measure pump sound levels can help determine whether a pump is operating in accordance with supplier specifications

The SCIS Dry Pumps group recently completed a preliminary measurement method proposal that would provide benchmarks for measuring and reporting sound levels, enabling pump customers (e.g., capital equipment OEMs, device makers) to better compare and evaluate pumps supplied by various manufacturers and select the appropriate pump for their intended process application. While certain existing standards can be leveraged to address the issue, additional parameters need to be considered to ensure repeatable results and consistent reporting. The proposal from the Dry Pumps group has been distributed to the larger SCIS community for review and feedback. Any additional refinements received will be incorporated into the document and then be transitioned to SEMI Standards for formal development.

Other SCIS groups are similarly furthering current efforts with the end goal of developing into standards:

  • The Critical Chamber Components group is drafting its proposed test method for measuring metals contamination through ICP-MS of showerheads used in semiconductor wafer processing.
  • The Liquid Delivery group is working to validate its proposed test method for measuring organic extractables in liquid delivery systems.
  • The Traceable Verification group has started drafting its information exchange model that will enable an industry standard parts traceability process. The resulting proposal will address the following elements: Label Barcode Method, Quality System Label Content (External, Stored), Template Format, Data Transport Method, Storage Location and Ownership, Secure Access Requirements, Encryption Requirements, Data Backup and Storage.

Opportunities for Engagement

SEMI SCIS is open to all SEMI Members. There will be an SCIS face-to-face meeting in conjunction with the Advanced Semiconductor Manufacturing Conference (May 3) in Saratoga Springs, New York. After this event, SCIS will reconvene in July at SEMICON West 2018. SCIS groups meet regularly via teleconference in between face-to-face meetings. For more information or to join SCIS, please contact Paul Trio at SEMI (ptrio@semi.org).

Engaging SEMI Technology Communities

SEMI technology communities enable SEMI members to connect, collaborate, and develop solutions to industry-critical issues. These SEMI communities provide members a collaborative platform and a collective voice within the electronic industry globally; allow SEMI members access to information on parts of the extended electronic supply chain; and, the SEMI standards and requirements platform to develop the community’s worldwide capability. SEMI has strategically chartered technology communities for: electronic materials, smart manufacturing, automated test equipment, MEMS & sensors, FHE, fab owners, and many others.

Global Update
SEMI
www.semi.org
April 24, 2018