Stress-Balanced Film Stack for Semiconductor Substrate Flatness
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Solution Overview
Problem
Existing semiconductor fabrication methods face challenges in maintaining substrate flatness during processing, leading to adverse effects such as overlay errors in lithography patterning, as the complexity and miniaturization of ICs increase, necessitating a solution to reduce stress-induced non-flatness.
Innovation Solution
A stress-neutralized film stack is formed by depositing a pair of films with opposite types of stress, where the second film's stress intensity compensates for the first film's stress, minimizing flatness issues and overlay errors, using materials like tungsten layers with controlled thickness and deposition methods to achieve compressive and tensile stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single film is deposited over the substrate, then the film provides necessary stress and structural properties, but the substrate flatness deteriorates due to stress-induced non-flatness
Solution Approach 1:
A second film with opposite stress type (tensile stress) is deposited over the first film (compressive stress) to counterbalance the stress-induced non-flatness. The second film acts as a counterweight that compensates for the curvature caused by the first film, thereby maintaining substrate flatness while preserving the necessary stress properties.
Solution Approach 2:
The patent employs a composite film stack consisting of two different materials with opposite stress characteristics. The first film material provides compressive stress while the second film material provides tensile stress, creating a balanced composite structure that maintains both structural integrity and substrate flatness.
2Strength
If film stress is increased to improve structural properties, then film strength improves, but overlay errors increase due to greater stress-induced non-flatness
Solution Approach 1:
The second film with opposite stress type serves as a counterweight that compensates for the stress-induced non-flatness caused by the first film. This allows the first film to maintain high stress levels for structural strength while the second film counterbalances the resulting curvature, thereby preserving overlay accuracy in subsequent lithography patterning.
3Strength
If film thickness is increased to enhance structural properties, then film strength improves, but stress-induced non-flatness worsens
Solution Approach 1:
The second film with opposite stress type and controlled thickness acts as a counterweight that compensates for the stress-induced non-flatness caused by the first film. By adjusting the thickness of the second film, the patent balances the stress effects while maintaining enhanced structural properties from the increased overall film stack thickness.
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 method effectively reduces stress-induced adverse impacts on flatness, minimizing overlay errors and ensuring precise alignment and quality in subsequent semiconductor device processing, enhancing the reliability and yield of complex and miniaturized semiconductor devices.
Implementation Method 1
forming a first film having a first film stress type and a first film stress intensity over a substrate
Implementation Method 2
forming a second film having a second film stress type and a second film stress intensity over the first film, wherein the second film stress type is different than the first film stress type and the second film stress intensity is about same as the first film stress intensity
Implementation Method 3
using materials like tungsten layers with controlled thickness and deposition methods
Data Source
AI summary
A method of fabricating a semiconductor device includes forming a first film having a first film stress type and a first film stress intensity over a substrate and forming a second film having a second film stress type and a second film stress intensity over the first film. The second film stress type is different than the first film stress type. The second film stress intensity is about same as the first film stress intensity. The second film compensates stress induced effect of non-flatness of the substrate by the first film.