Publication: Optimization of plasma metal etching process paramaters for critical dimension control
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Date
2025-09-01
Authors
Naveena A/P, Subramaniam
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Abstract
Critical dimension (CD) control has become one of the most crucial aspects of
semiconductor devices to ensure the electrical performance and reliability. Poor control
of CD after etching can cause variations in metal line resistance and ultimately impacting
the device functionality. In this study, Taguchi L9 orthogonal array design was applied
to investigate the influence of key process parameters on post-etch CD and to determine
the optimized process recipe which will yield mean CD near to target (~ 0.95 µm). The
experiments were carried out on a LAM 2300 Versys metal etcher. The process
parameters involved were RF bias voltage (100, 200, 300 V), Cl2 gas flow (30, 50, 70
sccm), N2 gas flow (5, 10, 15 sccm), and chamber pressure (10, 20, 30 mTorr). The effect
of process parameters on response characteristics (CD, metal line resistance, etch profile)
were studied. It was observed that increasing RF bias voltage and Cl2 gas flow led to CD
shrinkage and sidewall damage. Conversely, moderate N2 addition enhanced the sidewall
passivation, minimizing the profile damage. Lower chamber pressure has improved the
anisotropy but also increased the possibility sidewall pitting under certain gas flows
combination. The optimal recipe based on main effect plot (A1B1C3D2) predicted mean
CD of 0.998 µm, whereas the nominal setting (Recipe 2- A1B2C2D2) achieved 0.949
µm, which is close to the 0.95 µm target value. Confirmation tests validated the Taguchi
model, demonstrating less deviation between experimental and predicted CDs. This study
not only delivers an optimized plasma etch recipe for CD control but also validates the
applicability of Taguchi DOE approach.