Photomask Design & Fabrication
Microfabrication Mask Layout

LayoutEditor | Laser Lithography | Multi-Project Mask Design

        🎯 Project Type: Microfabrication Enabling Technology

        🛠️ Software: LayoutEditor (Free Version)

        🔬 Fabrication: μPG 101 Laser Mask Writer (405 nm wavelength)

        📅 Period: 2019 – 2024 (Throughout Ph.D.)

        🎭 Role: Sole mask designer for multiple device fabrication projects

MEMS Frontside Mask — Mask 1: Frontside Mask for MEMS Pressure Sensor

Strain Spatial Mask — Mask 2: Mask for Strain Sensor with Spatial Orientations

1D Strain Sensor Mask — Mask 3: Mask for 1D Strain Sensor

Micropyramid Mask — Mask 4: Mask for micropyramid silicon micromachining mold

Project Overview

Photomask design is a critical enabling technology for microfabrication. This project encompasses the complete workflow of designing and fabricating photomasks for various MEMS and microdevice applications using LayoutEditor software and laser lithography (μPG 101). I have designed multiple masks for different devices including MEMS pressure sensors (frontside and backside masks), microsupercapacitors with interdigitated electrodes, strain sensors with serpentine patterns, and micropyramid molds for PDMS casting.

Why Photomasks Matter

Photomasks are the master templates used in photolithography to transfer circuit patterns onto semiconductor wafers. Every microfabricated device - from MEMS sensors to integrated circuits - begins with a carefully designed photomask. The quality and precision of mask design directly determines the resolution, alignment accuracy, and yield of the final devices.

Mask Design & Fabrication Workflow

Step 1: Layout Design (LayoutEditor)

Design patterns using LayoutEditor free version. Key features used: layer management, DRC (Design Rule Checking), Boolean operations, array generation, GDSII export.

Step 2: Mask Writing (Laser Lithography)

μPG 101 laser mask writer (405 nm wavelength) exposes pattern onto photoresist-coated blank mask. Parameters: 4.8 mW laser power, optimized focus.

Step 3: Development

AZ400K developer (1:4 with water) removes exposed photoresist, revealing chromium layer according to designed pattern.

Step 4: Chromium Etching

Chromium Etch 1020 AC (nitric acid + ceric ammonium nitrate) removes exposed chromium for 3 minutes.

Step 5: Final Cleaning

Oxygen plasma RIE removes remaining photoresist, leaving only the chromium pattern on glass.

Tools & Equipment Used

LayoutEditor (Free Version)
μPG 101 Laser Mask Writer (405 nm)
AZ400K Developer (1:4 dilution)
Chromium Etch 1020 AC
OAI Mask Aligner (for inspection)
Reactive Ion Etching (RIE) for cleaning
Optical Microscope (pattern verification)

Mask Specifications

Parameter	Specification
Mask Substrate	Glass with Cr layer + positive photoresist
Laser Wavelength	405 nm
Laser Power	4.8 mW
Developer	AZ400K (1:4 with water)
Cr Etch Time	3 minutes
Minimum Feature Size	~2 μm (limited by laser writer)
Alignment Accuracy	±5 μm (double-side alignment)

Skills Acquired

LayoutEditor Proficiency GDSII File Format Design Rule Checking (DRC) Layer Management Boolean Operations Array Generation Double-Side Alignment Design Mask-to-Mask Alignment Marks Laser Lithography Operation Photoresist Development Wet Etching (Chromium) Mask Inspection (Microscopy)

Downloads

Devices Enabled by These Masks

MEMS Wheatstone Bridge Pressure Sensor: Frontside and backside masks enabled complete device fabrication (EGN5013C course project)
Microsupercapacitors: Interdigitated electrode mask for on-chip energy storage (C-MEMS training)
Wearable Strain Sensors: Serpentine pattern for flexible electronics applications
Piezoresistive Pressure Sensors: Micropyramid mold for PDMS texturing (used in dual piezoresistive sensor work)

Connection to My Research

Photomask design is foundational to all my microfabrication work:

MEMS Pressure Sensor: My frontside/backside masks were used to fabricate the Wheatstone bridge device for the Nanofabrication course
C-MEMS Training: Masks for SU-8 patterning enabled 3D carbon microstructure fabrication
Sensor Projects: IDE masks for electrochemical characterization of pressure sensors
Published Papers: Mask designs from this work contributed to multiple co-authored publications (Micromachines 2022, etc.)

Mask Design Examples

Design Detail — LayoutEditor workspace showing mask design

Alignment Marks — Double-side alignment marks for front-to-back alignment

Conclusion

This project demonstrates comprehensive photomask design and fabrication capability using LayoutEditor software and laser lithography. Multiple masks were successfully designed and fabricated for MEMS pressure sensors (frontside and backside), microsupercapacitors (interdigitated electrodes), strain sensors (serpentine patterns), and micropyramid molds. These masks enabled numerous device fabrication projects throughout my Ph.D., including the MEMS Wheatstone bridge pressure sensor for the Nanofabrication course, C-MEMS structures for energy storage, and textured PDMS layers for piezoresistive sensors. The skills acquired - LayoutEditor proficiency, DRC, double-side alignment design, and laser lithography operation - are essential for any microfabrication engineer and directly support all my device fabrication work.

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