Mechanical Chuck Segmentation for Plasma Resputter Rate
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Solution Overview
Problem
Conventional mechanical chucks used in plasma processing for through silicon via manufacturing have a reduced resputter rate due to a larger capacitor area, which results in a lower negative bias voltage, and increasing RF power leads to increased costs and chamber temperature, affecting process quality.
Innovation Solution
A mechanical chuck with a fixing assembly comprising a locking ring, insulation ring, and spacer ring, where the insulation ring electrically insulates the spacer ring from the locking ring, reducing the capacitor area and allowing increased negative bias voltage without increasing RF power, by using ceramic or quartz for the insulation ring and metal or insulation material for the spacer ring, and incorporating grooves to prevent plasma deposition on the insulation ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base, wafer and locking ring are electrically connected to avoid sparking, then the mechanical chuck can be operated safely, but the capacitor area increases and the negative bias voltage decreases
Solution Approach 1:
The locking ring is divided into two electrically isolated parts: a lower locking ring in electrical contact with the base for mechanical clamping and grounding, and an upper locking ring electrically isolated by an insulation ring for plasma exposure. This segmentation allows the lower ring to prevent sparking while the upper ring excludes plasma from the insulation ring surface, maintaining capacitor area and negative bias voltage.
Solution Approach 2:
An insulation ring made of electrically insulating material (e.g., ceramic, quartz) is introduced as an intermediary between the lower and upper locking rings. This insulation ring prevents electrical connection between the two rings, allowing the upper ring to be electrically isolated from the base while still providing mechanical support and positioning.
2Power
If RF power is increased to compensate for reduced negative bias voltage, then the negative bias voltage can be maintained, but the chamber temperature increases and process quality deteriorates
Solution Approach 1:
The design converts the potentially harmful effect of plasma deposition on the insulation ring into a beneficial feature by deliberately excluding plasma from the insulation ring surface through the groove structure. This prevents unwanted deposition that would compromise electrical insulation, while maintaining the desired negative bias voltage without requiring increased RF power that would raise chamber temperature.
3Power
If the capacitor area is reduced to increase negative bias voltage, then the resputter rate improves, but the mechanical chuck structure becomes more complex
Solution Approach 1:
The locking ring is segmented into lower and upper portions separated by an insulation ring, with the upper locking ring positioned to exclude plasma from the insulation ring surface. This segmentation effectively reduces the capacitor area to only the wafer surface, increasing negative bias voltage and resputter rate while maintaining a relatively simple overall structure.
Solution Approach 2:
The solution addresses the capacitor area issue by introducing a vertical dimension through the stacked arrangement of lower and upper locking rings separated by the insulation ring. This three-dimensional configuration allows plasma exclusion from the insulation ring surface, effectively reducing the horizontal capacitor area without requiring complex lateral modifications.
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
The solution increases the negative bias voltage on the workpiece surface, enhancing the resputter rate without increasing RF power, thereby improving the filling of through silicon vias while maintaining process quality and reducing costs.
Implementation Method 1
the insulation ring is used for electrically insulating the locking ring from the spacer ring
Implementation Method 2
RF power is applied to the base 11 by the RF power supply 15 to form a negative bias voltage on an upper surface of the wafer 12, which can attract the sputtered metal atoms
Implementation Method 3
a negative bias voltage is applied to the target material 14 by the DC power supply to excite a process gas in the reaction chamber 10 to form plasma, and attract energetic particles in the plasma to bombard the target material 14, so as to allow metal atoms on a surface of the target material 14 to escape and be deposited on the wafer 12
Data Source
AI summary
Embodiments of the invention provide a mechanical chuck and a plasma processing apparatus. According to at least one embodiment, the mechanical chuck includes a base and a fixing assembly including a locking ring, an insulation ring and an spacer ring, wherein the locking ring is configured to press an edge region of the workpiece to be processed so as to fix the same onto the base; an orthogonal projection of the spacer ring on an upper surface of the locking ring overlaps with the upper surface of the locking ring; and the insulation ring electrically insulates the spacer ring from the locking ring, an inner circumferential wall of the insulation ring, a portion of the upper surface of the locking ring inside the inner circumferential wall and a portion of a lower surface of the spacer ring inside the inner circumferential wall form a first groove, and an outer circumferential wall of the insulation ring, a portion of the upper surface of the locking ring outside the outer circumferential wall and a portion of the lower surface of the spacer ring outside the outer circumferential wall form a second groove.