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SEMI PR9-0705 © SEMI 2005 2 5.2.9 Wafer Level Sealing — bonding of wafers by anodic, silicon di rect, eutectic, or adhesive means. 5.2.10 Macrosealing — sealin g on com ponents at the macroscale. 5.2.11 Static Se als — s…

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SEMI PR9-0705 © SEMI 2005 1
SEMI PR9-0705
PROPOSED GUIDE FOR STANDARD PERFORMANCE, PRACTICES,
AND ASSEMBLY FOR ULTRA HIGH PURITY MICROSCALE FLUIDIC
SYSTEMS FOR USE IN SCALABLE PROCESS ENVIRONMENTS
This proposed guide was technically approved by the global MEMS Committee. This edition was approved
for publication by the global Audits and Reviews Subcommittee on April 17, 2005. It was available at
www.semi.org in June 2005 and on CD-ROM in July 2005.
1 Purpose
1.1 This document provides guidelines for generic fluidic I/O design and fabrication that can reduce redundant
engineering effort and lead to improved design, manufacturability, testing and operation.
2 Scope
2.1 This includes guidance for performance, practices, and assembly of microscale fluidic components. This
document will provide guidance to users involved in design and development of standard fluidic interfaces.
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish appropriate safety and health practices and determine the
applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 This guide is a work in progress. Some sections require further development. Suggestions for improvement are
welcome.
4 Referenced Standards and Documents
4.1 SEMI Standards
SEMI F1 — Specification for Leak Integrity of High-Purity Gas Piping Systems and Components
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
(Refer to SEMI’s Compilation of Terms (COT) for a list of the most current terms and their definitions.)
5.1 Abbreviations and Acronyms
5.1.1 MEMS— Microelectromechanical systems
5.1.2 TLA — Three Letter Acronym
5.2 Definitions
5.2.1 Microscale — 10
6
meters.
5.2.2 Microfluidics — fluid transport, physics, and chemistry on microscale dimensions.
5.2.3 Micro Sealing Dimensions — flow channel cross sections having an effective diameter of <25 micrometers;
optionally flow channel cross sections having an effective diameter of 25 to 100 micrometers.
5.2.4 Macro Sealing Dimensions — flow channel cross sections having an effective diameter of >100 micrometers.
5.2.5 Microfluidic Components — fluidic components functioning at the scale of 1-100 micrometers. Examples:
micro flow channels, microvalves, micro pumps.
5.2.6 Microsealing Systems
5.2.7 Macro to Micro Sealing — sealing that connects the micro regime with the macro regime.
5.2.8 Microsealing — sealing on components at the microscale.
SEMI PR9-0705 © SEMI 2005 2
5.2.9 Wafer Level Sealing — bonding of wafers by anodic, silicon direct, eutectic, or adhesive means.
5.2.10 Macrosealing — sealing on components at the macroscale.
5.2.11 Static Seals — seals that operate with non-moving surfaces.
5.2.12 Dynamic Seals — seals that operate with moving surfaces.
5.2.13 high-purity — of a system, subsystem, or component used for the control of chemicals (gases or liquids),
designed and constructed in such a manner that it does not introduce significant impurities, particulate or molecular,
into the flow stream it controls or regulates.
NOTE 1: Such systems, subsystems, or components are designed and constructed such that, if an impurity is introduced into the
flow path, it can be readily purged to an insignificant level.
5.3 leak — a path (or paths) in a sealed system that will pass tracer gas when a pressure differential, a concentration
differential, or diffusion path exists. There are two leak mechanisms: a mechanical passage and a material through
which gas can diffuse or permeate. A leak may have both mechanisms operating in parallel.
5.4 leakage, inboard — leakage from outside to inside occurring when the internal pressure is less than the external
pressure acting on a component or the concentrations of a given component are different inside and outside
generating a non-zero chemical potential. Inboard leakage is typically determined by introducing a tracer gas around
the exterior of the piping system or component under test.
NOTE 2: Inboard leak tests are easier tests to conduct to high sensitivity levels, but are typically not indicative of pressurized
operating conditions. It is difficult to correlate an inboard leak test to the performance of a component, subsystem, or system
when under internal pressure. Also, the internal collapsing forces created by external pressure may mask leaks which may exist
under pressurized operating conditions.
5.5 leakage, internal — leakage occurring within a component across a flow barrier, such as the seat of a closed
valve.
5.6 leakage, outboard — leakage from inside to outside occurring when the internal pressure is greater than the
external pressure acting on a component. Outboard leakage is typically determined by introducing a tracer gas into
the interior of the piping system or component under test.
5.7 Microfluidic Subsystesm — a “microfluidic subsystem” in a fluidic system may contain one or many MEMS
components. The subsystem contains control and signaling elements. The subsystem, in turn, is attached fluidically
to a larger system or subsequent process. e.g. mass flow controller for fluid delivery, lab-on-a-chip.
5.7.1 Fluidic Adapter — a physical interconnecter that fluidically links a microfluidic component to another micro-
or macro-scale fluidic device.
6 Design Guidelines
6.1 Purpose — Define basic design criteria for micro-fluidic interconnections, considering factors such as fluid
type, pressure, flow rate, surface conditions, materials and their compatibilities, etc. Establish a recommended
standard scaling rule for dimensions of such interconnections.
6.2 Scope — Micro-sealing connections as defined in ¶5.2.3 above, for applications in two pressure ranges: below
one atmosphere and 0–125 psig, and in three temperature ranges: <0 C, 0–100 C, and >100 C.
6.3 Define Design Parameters
6.3.1 Overall dimension and weight constraints: MEMS component, subsystems,
system, fittings, manifolds.
6.3.2 For different materials used to join parts check that the differences in thermal expansion coefficients are
acceptable for the temperature range that the component or system will be used in.
6.3.3 For different materials used to join parts check material chemical characteristics are compatible (see materials
§7 below).
6.3.4 Fluid types to be used with MEMS, define gases and liquids, reference SEMI F79 (Gas Compatibility with
Silicon). List all materials in wetted path.
6.3.5 Electrical configuration, digital or analog IEEE standards?
SEMI PR9-0705 © SEMI 2005 3
6.3.6 Volumes should be minimized (internal, connecting, interface/interconnection, dead volumes), give relation to
time and process response, give dry-down constraints.
6.3.7 Surface roughness requirements.
6.3.8 Design for shock and vibration criteria, Reference MIL-STD 810.
6.3.9 Leak integrity: permeability, across the seat, and inboard. Reference SEMI F1.
6.3.10 Accuracy, repeatability, control range requirements.
6.3.11 Purging capability, number of times of full scale should flow for purging, turnover requirement.
6.3.12 Direction of flow
6.3.13 Upstream filtration requirements, particle requirements, moisture, other contamination characteristics.
Reference SEMI E49 for high purity and ultrahigh purity systems.
6.3.14 Attitude constraints
6.3.15 Design for reliability requirements, MTTF, MTTR
6.3.16 Temperature limits
6.3.17 Pressure (proof, burst, inlet) limits
6.3.18 Flow ranges
6.3.19 Scaling rule for dimensions of interconnections
1
6.3.19.1 Consider scaling rule to be different for different industrial applications. For example gas and liquid
cannot use the same scaling rule.
6.3.20 Adapter guidelines for smooth transition from Macro to Micro. This is for the case the MEMS system is to
replace an existing device, and there is a mismatch of the dimensions. A flexible transition may be considered if
space is limited.
6.3.21 Surfaces that come into contact with samples, process gasses, or chemicals must not adsorb or react with
them. Select components or tubing that is: 1) inherently compatible, 2) can be treated (water rinsed, O
2
ashing, acid
clean...) or 3) coated (Teflon
®
, SiO
2
, ...), to be compatible. Consider protein materials where the quantity of
biomaterial sticking to surfaces will be dependent upon the wetted surface area and how well the fluid adsorbs to the
surface.
7 Materials Guidelines
7.1 Purpose — Provide a Matrix of Materials Compatibility for commonly used materials and provide examples of
applying the matrix to designs.
7.2 Scope — Use of this guide is limited to materials types known to be commonly used such as: silicon, polymers,
glass, metals, ceramics and plastics.
7.2.1 This guideline applies to materials which may be used in fluidic devices in large or small form factors. It is
assumed the material is in the wetted flow path as either a thin surface film or bulk material. Standard temperature
(0ºC) and pressure (1 atm) are conditions considered in this table unless otherwise stated. Physical, mechanical,
thermal, microstructural, and electrical properties of materials can be found in materials selection handbooks or
material supplier datasheets. Breadth of details for chemical compatibility and materials properties varies widely
within these literature and care must be taken to consider relevant information. unlikely that a single source of
information would be suitable.
7.2.2 The intended use of the compatibility matrix is to provide a general resource to the user. Detailed research
into materials compatibility with specific chemicals is an important part of any product development program. In
depth research into materials and fluid analysis are beyond the scope of this guide and will be required in most
circumstances.
1 Hsu, Tai-Ran; MEMS and Microsystems Design and Manufacture; McGraw-Hill, 2002 Section 6.7.