Fabrication of on-chip barium strontium titanate capacitors by metallo-organic decomposition

Metallo-organic thin film decomposition (MOD) was used in forming barium strontium titanate (BST) thin film capacitors on phosphorus doped polysilicon films deposited on 4 in. silicon wafers. A single step deposition process yielded highly uniform, crack-free BST films ranging up to 0.25 εm in thickness and having various step heights and dimensional area. Scanning electron microscopy (SEM) showed very good step coverage and planarization of the BST. The capacitors had capacitance densities above 200 nF/cm2, leakage current densities less than 1.55 εA/cm2 at a bias voltage of 10 V, and a dielectric breakdown field above 1 MVycm. Small temperature coefficients of capacitance and dissipation (tan δ) were also observed. Frequency response measurements were made using the BST capacitors and on-chip resistors in low pass and high pass circuit configurations. A plot of relative gain and phase angle versus frequency showed excellent agreement with predicted results.