PVD Chamber Collimator for Phase Change Memory GST Deposition
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Solution Overview
Problem
Conventional sputtering techniques face challenges in depositing thick chalcogenide layers, such as Ge2Sb2Te5, in phase change memory devices, particularly in high aspect ratio trenches, leading to non-conformal deposition and the formation of keyholes due to arcing and wide angular distribution of sputtered ions.
Innovation Solution
A modified deposition chamber using a collimator to collimate the sputtered ions and a pulsed sputtering technique to prevent arcing, ensuring that only collimated ions with a desired direction reach the substrate, resulting in a smoother and more uniform deposition across the trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional sputtering techniques are used to deposit thick chalcogenide layers, then the deposition thickness can be increased, but the conformality of deposition deteriorates and keyholes form in high aspect ratio trenches
Solution Approach 1:
The deposition process is segmented into multiple pulsed cycles rather than continuous deposition. Each pulse deposits a thin layer, allowing the trench to be filled progressively from bottom to top while maintaining conformality. The process repeats in discrete steps, preventing the formation of keyholes that occur in continuous thick deposition.
Solution Approach 2:
The sputtering process uses periodic pulsed DC power application to the target, creating intermittent deposition bursts. This periodic action allows plasma to refresh between pulses, preventing arcing and maintaining uniform deposition throughout the trench structure, achieving both thick layers and high conformality.
2Device complexity
If conventional sputtering is used for chalcogenide deposition, then the process is simple, but arcing occurs leading to non-uniform deposition
Solution Approach 1:
The sputtering process uses periodic pulsed DC power application to the target, creating intermittent deposition bursts. This periodic action allows plasma to refresh between pulses, preventing arcing and maintaining uniform deposition throughout the trench structure, achieving both thick layers and high conformality.
Solution Approach 2:
The deposition parameters are changed by implementing pulsed power delivery with specific duty cycles and frequencies. The target power is modulated in time, creating periods of active deposition followed by brief intervals that prevent charge buildup and arcing, thereby maintaining process reliability.
3Area of stationary object
If sputtered ions have wide angular distribution, then deposition covers broader areas, but uniformity across trench structures deteriorates
Solution Approach 1:
The collimator structure creates local quality differences in the ion flux by providing geometric shielding. Regions directly behind collimator openings receive focused ion flux, while areas at angles are blocked. This spatial filtering ensures that only ions with the desired direction reach the substrate, creating uniform deposition in trench structures while maintaining adequate coverage.
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 approach achieves high conformality and improved bottom coverage of the GST layer, increasing the deposition efficiency and reproducibility, with a significant improvement in the morphology of both the GST layer and overlying cap layers, effectively addressing the issues of keyhole formation and non-uniform deposition.
Implementation Method 1
conventional sputtering techniques face challenges in depositing thick chalcogenide layers
Implementation Method 2
A modified deposition chamber using a collimator to collimate the sputtered ions
Implementation Method 3
a pulsed sputtering technique to prevent arcing
Implementation Method 4
PVD process and chamber for the pulsed deposition of a chalcogenide material layer
Data Source
Figure 1~3
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AI summary
A method for depositing a chalcogenide layer (35) in a phase change memory (1), whereby a chalcogenide layer (35) is deposited by physical vapour deposition in a deposition chamber (50), having a collimator (60). The collimator (60) is formed by a holed disk arranged in a space (58) delimited by the chamber walls (51) and the chamber cover (57). The target is biased by a pulsed voltage to avoid charging and arching. The method is used to manufacture a phase change memory cell (2), whereby a resistive heater element (22) is formed in a dielectric layer (20), a mold layer (27) is formed over the dielectric layer (20); an aperture (31) is formed in the mold layer over the resistive heater element (22); a chalcogenide layer (35) is conformally deposited in the aperture (31) to define a phase change portion (35a); and a select element (13-15) is formed in electrical contact with the phase change portion (35a).