Wafer Surface Charge Control During CMP
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Solution Overview
Problem
The semiconductor industry faces challenges in controlling electrostatic charging effects during CMP processes, which affect CMP selectivity and uniformity, leading to non-uniform planarization and potential defects in integrated circuits, especially as device dimensions decrease below 20 nm.
Innovation Solution
A system and method that includes an on-board metrology module to characterize and adjust both global and local electrostatic charges on a semiconductor wafer using an immersion bath for global charge adjustment and a charge pencil for localized charge neutralization, ensuring uniform planarization by controlling the electric charge at the wafer surface before and during CMP operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CMP polishing is performed to planarize the wafer surface, then surface flatness is improved, but electrostatic charge accumulates on the wafer surface causing non-uniform planarization and hot spots
Solution Approach 1:
The patent applies corona discharge treatment to neutralize the electrostatic charge that accumulates during CMP polishing. The corona discharge unit generates ionized air that dissipates the harmful electrostatic charge, converting the harmful effect into a controllable parameter that can be managed through additional processing steps.
Solution Approach 2:
The patent introduces charge measurement and neutralization steps before and during the CMP polishing process to prevent charge accumulation from causing non-uniform planarization. By measuring surface charge with a surface potential meter and applying corona discharge treatment beforehand, the system prevents the development of hot spots rather than correcting them after they occur.
2Manufacturing precision
If slurry chemistry is optimized for high CMP selectivity, then removal rate control is improved, but local irregularities cause hot spots where non-uniform planarization occurs
Solution Approach 1:
The patent implements a feedback control system where surface charge is measured using a surface potential meter before and during CMP polishing. Based on the measured charge levels, corona discharge treatment is applied to neutralize charge, and the process is monitored continuously to maintain uniform planarization and prevent hot spot formation.
Solution Approach 2:
The patent controls the electrostatic charge parameter by applying corona discharge treatment at specific stages of the CMP process. By adjusting the charge neutralization parameter through controlled corona discharge, the system maintains optimal conditions for uniform planarization while preserving the selectivity benefits of optimized slurry chemistry.
3Productivity
If device dimensions are reduced below 20 nm, then device density is improved, but CMP selectivity has greater effect on device performance requiring stricter charge control
Solution Approach 1:
For sub-20 nm devices, the patent employs enhanced feedback control with surface potential measurements taken at multiple stages. The corona discharge treatment parameters are adjusted based on real-time charge measurements to maintain the strict selectivity control required for high-density device fabrication.
Solution Approach 2:
The patent applies corona discharge treatment and charge neutralization before CMP polishing of sub-20 nm devices to prevent charge accumulation from affecting the sensitive small-scale features. This preliminary charge control ensures that the reduced device dimensions do not suffer from exacerbated charge effects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves die and wafer yields, reduces manufacturing costs, and ensures consistent CMP selectivity and removal rates by neutralizing electrostatic charges, thereby preventing hot spots and defects in subsequent layers.
Implementation Method 1
an on-board metrology module to characterize and adjust both global and local electrostatic charges on a semiconductor wafer using an immersion bath for global charge adjustment
Implementation Method 2
a charge pencil for localized charge neutralization... The charge pencil bears a tapered porous polymer tip that absorbs and applies an ionic solution to a localized region of the wafer surface
Implementation Method 3
The charge pencil bears a tapered porous polymer tip that absorbs and applies an ionic solution to a localized region of the wafer surface
Implementation Method 4
Surface charge tends to accumulate due to friction during CMP and during the subsequent brush cleaning step
Data Source
AI summary
CMP selectivity, removal rate, and uniformity are controlled both locally and globally by altering electric charge at the wafer surface. Surface charge characterization is performed by an on-board metrology module. Based on a charge profile map, the wafer can be treated in an immersion bath to impart a more positive or negative charge overall, or to neutralize the entire wafer before the CMP operation is performed. If charge hot spots are detected on the wafer, a charge pencil can be used to neutralize localized areas. One type of charge pencil bears a tapered porous polymer tip that is placed in close proximity to the wafer surface. Films present on the wafer absorb ions from, or surrender ions to, the charge pencil tip, by electrostatic forces. The charge pencil can be incorporated into a CMP system to provide an in-situ treatment prior to the planarization step or the slurry removal step.