CASE STUDY

Meet the Digital Micromirror Device

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A DMD chip from Texas Instruments packs over a million individually addressable micromirrors onto a single die.

The chip is mounted on a circuit board that converts incoming image data into digital signals the mirrors respond to.

A high-resolution DMD can hold more than a million mirrors — each one its own pixel.

HOW A PIXEL WORKS

On, or off

Each mirror has exactly two stable positions. Depending on which one it's tilted to, incident light from a collimated source is either reflected toward the projection lens, or deflected away from it entirely.

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A DMD is fundamentally a binary switch. Brightness is created by how long each mirror stays "on" within a frame, not by tilting to in-between angles.

WHY IT WORKS SO WELL

Bright, compact, and sharp

Advantages High brightness and contrast, compact, low weight and power

DLP 1080p Over 2 million pixels (1920 × 1080)

Latest DLP Up to 4096 × 2160 resolution

Millions of mirrors, each simply on or off, is enough to reproduce a full-color, high-resolution image.

INSIDE ONE MIRROR

The anatomy of a DMD pixel

Mirror support H-shaped structure suspended above the substrate

Torsion beam A thin torsional spring the support hangs from

Central post Elevates the mirror above the support plane

Actuation electrodes Beneath the support, tip it about the torsion axis

Landing pads Prevent the tilted mirror from short-circuiting

Five simple parts, working together, are all it takes to flip a mirror thousands of times a second.

DMD BY THE NUMBERS

A chip built to last

Moving parts 0.5 to 1.2 million per chip

Mechanical motion Discrete contacts, or "landings"

Lifetime requirement 450 billion contacts per moving part

Address voltage Limited by 5-volt CMOS technology

Mechanical elements Aluminum

Every single mirror has to survive hundreds of billions of landings without wearing out.

FABRICATION

Building a DMD

Process Low-temperature sputter deposition and plasma etch

Sacrificial layer Organic, dry-etched, removed at the wafer level

Die separation After the sacrificial layer is removed

Package Optical, hermetic, with thermal vias

Testing High-speed electro-optical, before die separation

The same deposit-pattern-release sequence you already know from earlier units — just built on aluminum instead of polysilicon.

UNIT 22 STUDY COMPLETE

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Ready for the Fab Challenges?

You've covered Inside TI's DMD.