Planetary Wafer Stage Tilt and Oscillation for Uniform Thin Film
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Solution Overview
Problem
Existing wafer processing systems face challenges in achieving uniform thin film thickness and symmetry due to beam divergence and shadow asymmetry, particularly when processing larger wafers, which leads to variations in deposition and etching rates across different facets and locations on the wafer.
Innovation Solution
A planetary scan wafer stage with a tilt actuator, oscillating planetary arm, and slit support plate allows for coordinated rotation and oscillatory motion along an arcuate path, ensuring uniform exposure of the wafer to the beam, reducing variations in film thickness and asymmetry by tilting and rotating the wafer while scanning it across a stationary slit support plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a beam with larger diameter is used to process larger wafers, then beam divergence effects are reduced, but ion source size, weight, cost, and complexity increase
Solution Approach 1:
The patent applies dynamic motion to the wafer stage, implementing coordinated wafer rotation, tilt, and linear scan movements. This dynamic approach allows a smaller ion source to achieve uniform processing across large wafers by continuously changing the relative geometry between the beam and wafer surface, compensating for beam divergence without requiring a larger ion source.
Solution Approach 2:
The patent introduces multiple dimensional movements (rotation around wafer normal axis, tilting around two orthogonal axes, and linear scan along an arcuate path) to solve the problem of beam divergence. By adding these dimensional degrees of freedom, the system achieves uniform thin film deposition without increasing ion source diameter.
2Manufacturing precision
If wafer rotation, tilt, and linear scan are combined to improve uniformity, then thin film thickness uniformity improves in some directions, but shadow asymmetry and position-dependent variations still occur
Solution Approach 1:
The patent deliberately employs asymmetric motion parameters, including a non-zero tilt angle and an arcuate scan path that is offset from the wafer center. This controlled asymmetry, combined with coordinated rotation, compensates for beam divergence and creates symmetric thin film thickness distribution across the wafer surface, eliminating shadow asymmetry effects.
Solution Approach 2:
The system uses coordinated control of multiple motion axes (rotation, tilt, and scan) with precisely controlled timing and synchronization. This feedback-controlled coordinated motion ensures that the wafer position and orientation are continuously adjusted to maintain uniform beam exposure across all facets, eliminating position-dependent thickness variations.
3Manufacturing precision
If beam collimation is used to reduce beam divergence, then radial variations in deposition rate are reduced, but collimation is difficult and expensive to implement with required accuracy
Solution Approach 1:
The patent replaces the mechanical collimation system with a motion-based solution. Instead of using complex mechanical collimators to physically restrict and directionalize the beam, the system uses coordinated wafer motion (rotation, tilt, and scan) to achieve uniform exposure. This substitutes a relatively simple motion control system for a complex and expensive mechanical collimation system.
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 enables more uniform and symmetrical thin film structures across all facets of the wafer, even for sub-micron-sized features, using a smaller, less expensive ion source and improving yield by minimizing beam divergence effects.
Implementation Method 1
a tilt actuator for rotating the planetary arm and slit support plate together to a selected tilt angle relative to a propagation direction for a beam of particles incident upon the wafer
Implementation Method 2
the planetary arm is movable along an arcuate path by the planetary scan actuator
Implementation Method 3
Rotating a wafer during deposition and etching operations has been used to improve uniformity in rates of deposition or etching for all exposed facets
Implementation Method 4
During deposition, a beam from an ion source removes material from a target placed in the beam's path
Implementation Method 5
During etching, a beam of energetic particles emitted from an ion source is incident upon the wafer, leading to removal of material from those parts of the wafer exposed to the beam
Implementation Method 6
Some of the material removed from the target by the beam deposits on the wafer to form structures on the wafer's surface
Data Source
AI summary
A planetary arm coupled to a tilt actuator moves a wafer in oscillatory motion along an arcuate path to expose a surface of the wafer to an incident ion beam for deposition and/or etching processing of thin film structures on the surface of the wafer. A wafer holder on an end of the planetary arm may be driven in rotation while the planetary arm executes oscillatory motion at a selected tilt angle relative to an incident ion beam. A slit support plate provides controllable exposure of the wafer to the incident beam. Embodiments are suitable for use in wafer deposition machines and/or wafer etching machines.