Dual Magnetron Plasma Sputtering Target Cleaning
Solution Overview
Problem
In plasma sputtering, the redeposition of sputtered atoms on the target leads to thickening films that do not adhere well, causing particle generation and defects in integrated circuits, especially in high aspect-ratio holes, due to the diffusion of ions towards the target center, resulting in yield loss and reliability issues.
Innovation Solution
The use of two dissimilar magnetrons, a small, strong source magnetron and a larger, weaker auxiliary magnetron, positioned at different radii and moved in complementary radial directions to control sputtering and cleaning phases, with the source magnetron near the periphery during deposition and the auxiliary magnetron near the center during cleaning, to manage plasma distribution and prevent redeposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a small magnetron is rotated near the periphery of the target to create high-density plasma and increase sputtering rate, then the sputtering rate and ionization fraction are improved, but redeposition of sputtered atoms on the target center occurs causing film thickening and poor adhesion
Solution Approach 1:
The invention divides the single magnetron function into two separate magnetrons: a source magnetron for creating high-density plasma and an auxiliary magnetron for controlling ion distribution and preventing redeposition. This segmentation allows each magnetron to be optimized for its specific function, resolving the contradiction between high sputtering rate and film uniformity.
Solution Approach 2:
The auxiliary magnetron acts as an intermediary component that modifies the plasma environment created by the source magnetron. By generating additional magnetic fields, the auxiliary magnetron controls ion diffusion paths and prevents excessive ion accumulation at the target center, thereby preventing redeposition while maintaining the high sputtering rate generated by the source magnetron.
2Reliability
If the target is cleaned by sputtering the center area, then redeposited film is removed, but cleaning time increases and system productivity is impacted
Solution Approach 1:
The auxiliary magnetron enables the target cleaning function to be performed more efficiently by providing focused magnetic field control at the target center. This allows cleaning to be accomplished with the magnetron positioned optimally for center-area cleaning, reducing the time required compared to using a peripherally positioned magnetron that would require longer operation to achieve the same cleaning effect.
3Device complexity
If a single magnetron is used for both sputter deposition and target cleaning, then device complexity is reduced, but the magnetron must be small and peripherally located which limits cleaning effectiveness
Solution Approach 1:
The invention achieves multi-functionality by having two magnetrons that can perform different functions: the source magnetron primarily handles sputter deposition while the auxiliary magnetron handles both deposition assistance and target cleaning. This universal design allows the system to maintain low complexity while achieving effective cleaning, as the auxiliary magnetron can be positioned and operated optimally for cleaning operations.
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 configuration enhances sputter deposition uniformity, reduces particle generation, and allows for efficient target cleaning without increasing chamber complexity or cost, thereby improving the quality and reliability of integrated circuits.
Implementation Method 1
a small magnetron is rotated about the target center near its periphery to project a strong magnetic field adjacent the sputtering face of the target to create a high-density plasma
Implementation Method 2
The two magnetrons move in complementary radial directions
Implementation Method 3
the ions tend to diffuse towards the center and sputter deposit across the entire wafer
Implementation Method 4
Sputtering, alternatively called physical vapor deposition (PVD), is the most prevalent method of depositing layers of metals and related materials
Data Source
AI summary
A dual magnetron for plasma sputtering including a source magnetron and an auxiliary magnetron, each of which rotate about the center of the target at respective radii. The positions of the magnetron can be moved in complementary radial directions between sputter deposition and target cleaning. The magnetrons have different characteristics of size, strength, and imbalance. The source magnetron is smaller, stronger, and unbalanced source magnetron and is positioned near the edge of the wafer in sputter deposition and etching. The auxiliary magnetron is larger, weak, and more balanced and used for cleaning the center of the target and guiding sputter ions from the source magnetron in sputter deposition. Each magnetron may have its plasma shorted out in its radially outer position.