PVD Upper Shield with Raised Area for EUV Mask Blank Deposition
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Solution Overview
Problem
In multi-cathode physical vapor deposition (PVD) chambers, there is a need to reduce defect sources such as particles and cross-contamination between targets of different materials, particularly in the manufacture of EUV mask blanks where silicon and molybdenum layers are deposited, as cross-contamination can lead to defects in the final product.
Innovation Solution
A PVD chamber design featuring multiple cathode assemblies with an upper shield having strategically positioned shield holes and a raised area between them, allowing for alternate sputtering of materials from different targets without rotating the shield, which prevents contamination by maintaining a gap greater than the diameter of the shield holes and ensuring the raised area's height is over one centimeter, thereby preventing material deposition from one target onto another.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple cathode assemblies are used in a PVD chamber, then productivity is improved by depositing multilayer structures, but cross-contamination between targets occurs leading to defects
Solution Approach 1:
A shield structure is introduced as an intermediary element between multiple cathode assemblies. The shield includes shield holes positioned to expose only the intended target during sputtering, preventing material from one target from reaching another target. This mediator physically blocks the harmful cross-contamination pathway while allowing the useful deposition process to continue.
Solution Approach 2:
The shield structure creates locally differentiated exposure zones. Each shield hole is strategically positioned and sized to expose only its corresponding target to the plasma, while other targets remain shielded. This local quality control ensures that material deposition occurs only from the intended source at any given time, eliminating cross-contamination.
2Device complexity
If targets are closely positioned to increase chamber utilization, then device complexity is reduced, but particle generation increases due to material redeposition
Solution Approach 1:
The shield structure acts as a mediator that prevents material redeposition onto adjacent targets. By blocking the line of sight between targets, the shield stops sputtered material from traveling to neighboring targets where it could redeposit and form particles. This allows targets to be positioned closer together without increasing particle generation.
3Productivity
If high power density is applied to increase deposition rate, then productivity is improved, but target temperature rises causing defects
Solution Approach 1:
Heat is extracted from the target system through the shield structure. The shield, positioned between the plasma source and targets, provides a thermal barrier that prevents excessive heat accumulation on target surfaces. This allows high power density to be applied for fast deposition while the shield extracts excess heat, preventing target overheating and associated defects.
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 design effectively reduces particle generation and cross-contamination, enabling the deposition of alternating layers of materials like silicon and molybdenum without rotating the upper shield, thereby minimizing defects in the EUV mask blanks and improving the quality of the multilayer reflective stack.
Implementation Method 1
an upper shield below the plurality of cathode assemblies having a first shield hole having a diameter and positioned on the upper shield to expose the first cathode assembly and a second shield hole having a diameter and positioned on the upper shield to expose the second cathode assembly... a raised area in the region between the first shield hole and the second shield hole
Implementation Method 2
Sputtering, alternatively called physical vapor deposition (PVD), is used for the deposition of metals and related materials... the sputtering target is bombarded by energetic ions, such as a plasma, causing material to be displaced from the target and deposited as a film on a substrate
Data Source
AI summary
A physical vapor deposition (PVD) chamber and a method of operation thereof are disclosed. Chambers and methods are described that provide a chamber comprising an upper shield with two holes that are positioned to permit alternate sputtering from two targets.