Hard Mask Film Stress Gradient for Wiggling Suppression
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Solution Overview
Problem
As semiconductor devices miniaturize, the hard mask used in the manufacturing process experiences wiggling due to film stress, which is difficult to suppress with conventional methods, especially when the etching pattern is further miniaturized and the aspect ratio increases.
Innovation Solution
A hard mask film forming method where tensile stress is controlled to increase monotonously from the bottom surface to the upper surface, using microwave plasma chemical vapor deposition, to prevent wiggling by ensuring consistent tensile stress across the film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a photoresist is used as an etching mask, then the manufacturing process is simple, but the pattern cannot be maintained due to low resistance to etching gas or plasma
Solution Approach 1:
The etching mask is divided into two separate components: a photoresist layer for pattern formation and a hard mask layer for etching resistance. The photoresist provides the initial pattern, while the hard mask (formed by depositing silicon nitride or similar material) provides the necessary resistance to maintain the pattern during etching. This segmentation allows each layer to perform its specialized function effectively.
Solution Approach 2:
The etching mask system uses composite structure combining photoresist and hard mask materials. The photoresist (organic polymer) and hard mask (inorganic material like silicon nitride) are deposited in sequence to create a composite mask structure that combines the pattern-forming capability of photoresist with the etching resistance of hard mask materials.
2Length of moving object
If the pattern is miniaturized to achieve smaller device dimensions, then the device scaling is improved, but wiggling occurs in the hard mask due to film stress
Solution Approach 1:
The patent applies different stress characteristics to different regions of the hard mask film. By controlling the deposition conditions (such as plasma power, gas flow rates, or temperature gradients) during hard mask formation, tensile stress is intentionally introduced in the upper portion of the hard mask where wiggling is most likely to occur, while the lower portion maintains compressive or neutral stress. This local stress differentiation prevents uniform wiggling across the entire hard mask structure.
Solution Approach 2:
The patent changes the physical and chemical parameters of the hard mask film during deposition to control its stress state. By adjusting deposition parameters (plasma power, gas composition, substrate temperature, deposition rate), the film stress can be tuned from compressive to tensile, or to have a gradient distribution through the film thickness. This parameter control allows optimization of hard mask stability for miniaturized patterns.
3Stability of the object's composition
If a protective film is formed on the sidewall of the mask to prevent wiggling, then the wiggling prevention is improved, but the device complexity increases
Solution Approach 1:
Instead of adding a separate protective film layer on the sidewall, the patent extracts the wiggling prevention function directly into the hard mask film itself by controlling its internal stress distribution. The hard mask is deposited with a specific stress gradient (tensile stress in the upper portion) that inherently prevents wiggling, eliminating the need for additional protective sidewall films and simplifying the overall process.
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 method effectively suppresses wiggling even at finer patterns and higher aspect ratios, allowing for precise etching without the need for high bulk film stress, thereby maintaining pattern integrity and reducing the risk of stress variations during etching.
Implementation Method 1
forming a hard mask film on the substrate while controlling film forming parameters
Implementation Method 2
microwave plasma chemical vapor deposition
Data Source
AI summary
A hard mask film forming method includes preparing a substrate in which an etching target film is formed on a base. The hard mask film forming method further includes forming a hard mask film on the substrate while controlling film forming parameters such that tensile stress is set as initial film stress and the tensile stress monotonously increases from a bottom surface of the hard mask film toward an upper surface of the hard mask film.