Cu Annealing Atmosphere for Flash Memory Data Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for fabricating semiconductor memory devices, particularly flash memory devices, face challenges with data retention due to hydrogen ion contamination and diffusion, which affects charge loss and reliability, especially as device dimensions shrink into the deep sub-micron regime and when using copper interconnects.
Innovation Solution
The method involves annealing copper layers in a nitrogen atmosphere with reduced hydrogen content (0 to 1 vol. %) at lower temperatures (100° C. to 200° C.) to minimize hydrogen ion generation and diffusion, and conducting annealing before or after chemical mechanical polishing to ensure adequate adhesion of capping layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Cu interconnect methodology employing a diffusion barrier layer is used, then Cu diffusion is prevented, but adhesion of capping layers is inadequate due to oxides on the upper surface of inlaid Cu
Solution Approach 1:
The patent applies preliminary action by performing plasma treatment on the Cu surface before depositing the diffusion barrier layer. This preliminary plasma cleaning step removes oxides from the Cu surface, ensuring both adequate adhesion of the capping layer and prevention of Cu diffusion. The plasma treatment is conducted in-situ immediately before barrier layer deposition to maintain surface cleanliness.
2Stability of the object's composition
If Cu is annealed in a forming gas atmosphere with high hydrogen content, then grain growth and stress relief are achieved, but hydrogen ion diffusion into flash memory devices increases causing charge loss
Solution Approach 1:
The patent applies parameter changes by modifying the annealing atmosphere composition and temperature parameters. Instead of using conventional forming gas with high hydrogen content (e.g., 4 vol.% H2), the patent uses a reduced hydrogen atmosphere (0 to 1 vol.% H2) combined with lower annealing temperatures (100°C to 200°C). This parameter optimization achieves adequate grain growth and stress relief while minimizing hydrogen ion generation and diffusion, thereby preserving data retention in flash memory devices.
3Productivity
If device dimensions are reduced to deep sub-micron regime, then integration density is improved, but vulnerability to mobile ion contamination such as hydrogen degradation increases
Solution Approach 1:
The patent applies parameter changes by optimizing the annealing process parameters (reduced hydrogen atmosphere and lower temperature) to minimize hydrogen ion generation during Cu processing. This parameter optimization is particularly critical for deep sub-micron devices where the smaller dimensions make them more vulnerable to mobile ion contamination. The modified annealing parameters reduce hydrogen diffusion into the device, thereby maintaining reliability despite reduced device dimensions and higher integration density.
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 significantly reduces hydrogen ion diffusion, enhancing data retention and reliability of semiconductor memory devices by controlling the annealing conditions and improving the adhesion of capping layers, thereby maintaining charge integrity and device performance.
Implementation Method 1
annealing copper layers in a nitrogen atmosphere with reduced hydrogen content (0 to 1 vol. %) at lower temperatures (100° C. to 200° C.)
Implementation Method 2
minimize hydrogen ion generation and diffusion
Implementation Method 3
conducting annealing before or after chemical mechanical polishing
Data Source
AI summary
Data retention in flash memory devices, such as mirrorbit devices, is improved by reducing the generation and/or diffusion of hydrogen ions during back end processing, such as annealing inlaid Cu. Embodiments include annealing inlaid Cu in an N2 atmosphere containing low H2 or no H2, and at temperatures less than 200° C., e.g., 100° C. to 150° C.