AFM Cantilever & Micro-Probe Photolithography Vector Prepress Guide

Microfabrication prepress, Euler-Bernoulli cantilever design, crystal plane wet etching, and high-resolution phototool vector rules for scanning probe microscopy.

1. Micro-Cantilever Mechanics & Mode Selection

Atomic Force Microscopy (AFM) relies on micromachined cantilevers to operate across various scan modes: Contact Mode ($k = 0.01\text{--}0.5\text{ N/m}$), Tapping/Intermittent Contact Mode ($k = 10\text{--}50\text{ N/m}$, $f_0 = 150\text{--}350\text{ kHz}$), and High-Frequency Non-Contact Mode ($k > 40\text{ N/m}$, $f_0 > 300\text{ kHz}$). Selecting the proper beam geometry and thickness $t$ is vital to maximize signal-to-noise ratios while avoiding sample deformation.

2. KOH Wet Etching & 1-Bit Phototool Mask Prepress

Fabrication on Silicon-on-Insulator (SOI) wafers involves anisotropic wet chemical etching in 30% KOH or TMAH at 80°C. Etch rates along $\{100\}$ planes exceed $\{111\}$ planes by over 100:1, naturally forming pyramidal tips bounded by four $\{111\}$ crystal facets angled at $54.74^\circ$.

Vector prepress for AFM photolithography masks requires:

• Convex Corner Compensation: Adding corner square or octagonal serif geometries to the tip apex mask to prevent severe undercut rounding.
• Backside Alignment Windows: 1:1 aligned infrared through-wafer alignment crosses for membrane release etching.
• Reflective Metal Coating Margin: Inward gold/aluminum laser reflector zone choke on the cantilever backside to avoid bimetallic thermal curvature.