Introduction to the SEMI E91 Standard
SEMI E91 defines the Prober Specific Equipment Model (PSEM), \a standardized framework governing how prober equipment communicates with factory automation systems in semiconductor manufacturing environments. Probers are critical tools used to perform electrical measurements on wafers and substrates, validating die performance before packaging and shipment.
Built on top of the foundational SEMI E30 (GEM) standard, SEMI E91 extends the Generic Equipment Model with prober-specific behaviors, interfaces, and operational models, enabling seamless, automated integration of probe test equipment into modern semiconductor factories.
Purpose of the SEMI E91 Standard
The primary purpose of SEMI E91 is to facilitate the integration of prober equipment into automated semiconductor factories by defining a consistent, predictable host interface and equipment operational model.
Specifically, SEMI E91:
- Establishes a standard SECS/GEM host interface for prober equipment, reducing integration complexity across different equipment suppliers
- Defines a Prober Job state model that governs when and how electrical measurements are initiated, managed, and reported
- Specifies remote commands that allow factory automation hosts to initiate and control Prober Jobs without manual intervention
- Standardizes process program requirements and data reporting so measurement results are delivered in a consistent, machine-readable format
- Applies specifically to prober equipment where wafers are returned to the same slot and carrier from which they were loaded — a common configuration in front-end wafer test
Key Concepts and Features of SEMI E91
SEMI E91 introduces several prober-specific extensions to the GEM standard that are essential for automated electrical test operations:
- Prober Specific Equipment Model (PSEM): A defined operational model describing equipment characteristics and behaviors required of all compliant prober equipment, beyond the baseline GEM requirements
- Prober Job State Model: A structured state machine defining valid Prober Job activities based on overall equipment state — ensuring automation systems can reliably predict and manage equipment behavior
- Remote Command Set: A suite of host-initiated commands enabling full remote control of Prober Job lifecycle — from job creation and execution to completion and abort
- Collection Events and Variable Data Items: Standardized events and data variables that must be reported by the equipment, enabling consistent data collection across multiple prober suppliers
- Process Program Management: Defined requirements for how measurement recipes and process programs are stored, selected, and executed on the prober
- Processing Scenarios: Detailed descriptions of specific operational workflows, including how the equipment behaves during normal processing, exception handling, and job transitions
Why SEMI E91 Is Important to the Industry
SEMI E91 is a critical enabler of automated, high-throughput wafer test operations — with benefits that extend across the semiconductor supply chain
For Equipment Suppliers:
- Provides a clear, authoritative specification for building GEM-compliant prober interfaces, reducing ambiguity and custom engineering per factory customer
- Enables faster customer qualifications by delivering a predictable, standards-based host interface out of the box
- Reduces long-term cost of support and integration across multiple fab environments
For Semiconductor Manufacturers (IDMs & Foundries):
- Enables plug-and-play integration of prober equipment into Manufacturing Execution Systems (MES), advanced process control (APC) systems, and other factory applications
- Standardized data reporting supports real-time yield monitoring and faster response to electrical test excursions
- Reduces factory integration time and cost when qualifying new prober equipment
- Supports multi-supplier flexibility — factories are not locked into proprietary interfaces for probe test automation
For Software and Automation Suppliers:
- Provides a well-defined interface contract, allowing automation software to support multiple prober platforms with a single integration framework
- Enables development of standardized MES connectors, data collection agents, and Prober Job management applications
- Facilitates interoperability testing and certification, improving software reliability
In Manufacturing:
- Supports fully lights-out automated wafer test, reducing operator touchpoints and associated variability
- Enables closed-loop process control by feeding standardized electrical test data back into yield management and process optimization systems
PDF Solutions Products That Support SEMI E91
PDF Solutions offers a portfolio of equipment connectivity and data infrastructure products designed to help equipment suppliers and their factory customers implement and leverage SEMI standards including SEMI E91:
- Cimetrix® CIMConnect — this industry-leading GEM/SECS connectivity toolkit supports implementation of SEMI E91 PSEM requirements on prober equipment, enabling suppliers to deliver compliant host interfaces with accelerated development timelines
- Cimetrix® EquipmentTest — testing and validation tool that enables equipment suppliers to verify standards compliance before delivery, reducing qualification risk at customer factories