Variable Thickness Etch Mask for Film Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor fabrication processes face challenges in achieving uniform film thickness, leading to variations in device performance due to process variations, which are costly and time-consuming to correct through post-processing methods like laser trimming or electrical fusing.
Innovation Solution
A method involving the measurement of film thickness to create a two-dimensional contour map, followed by selective patterning of an etch mask layer using a reticleless exposure system to adjust the film thickness uniformly across a semiconductor body, allowing for in-situ etching to achieve nominal thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photolithographic and etching steps are used to integrate MIM capacitors, then device performance can be adjusted, but process complexity and manufacturing time increase
Solution Approach 1:
The patent combines multiple photolithographic and etching steps into a single etching step by using a variable thickness mask layer that encodes thickness variation information. The mask layer is formed in one deposition step and then patterned in one photolithography step, followed by a single etching step that uses the mask's variable thickness to automatically compensate for film thickness variations across the wafer.
Solution Approach 2:
The patent performs preliminary measurement of film thickness across the wafer and uses this information to create a contour map. This contour map is then used to guide the formation of the mask layer with spatially varying thickness, so that the mask is prepared in advance with the exact thickness profile needed to compensate for anticipated etching variations.
2Manufacturing precision
If post fabrication adjustments are made to correct device specifications, then device performance can be optimized, but manufacturing time and cost increase
Solution Approach 1:
The patent performs all necessary thickness compensation during the main fabrication process rather than as a post-fabrication adjustment. The variable thickness mask is created and used during the etching step itself, so that the correct thickness is achieved in-situ without requiring subsequent laser trimming or electrical fusing operations.
Solution Approach 2:
The mask layer serves dual purposes: it defines the pattern to be etched and simultaneously provides the thickness compensation information. The variable thickness of the mask layer automatically adjusts the etching depth in different regions, so the process self-corrects for film thickness variations without requiring external intervention or additional adjustment steps.
3Ease of manufacture
If uniform film deposition is attempted across the entire wafer, then manufacturing simplicity is maintained, but film thickness uniformity deteriorates due to process variations
Solution Approach 1:
The patent applies local quality by creating a mask layer with spatially varying thickness that is tailored to the specific thickness variations present in different regions of the wafer. The mask thickness is locally optimized based on the contour map, so that each region receives the appropriate amount of etching protection to achieve uniform final thickness, while the deposition process itself remains simple and uniform across the entire wafer.
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 results in improved process control and reduced variability in film thickness, enhancing device performance and reducing the need for costly post-processing adjustments, thereby optimizing semiconductor chip production.
Implementation Method 1
The selective patterning comprises subjecting different regions of the etch mask layer to varying exposure times or levels dependent upon the thickness of the underlying adjustable film layer
Implementation Method 2
The semiconductor body, comprising the adjustable film layer and etch mask layer, is then etched
Data Source
AI summary
The present invention relates to a method of performing a variable film etch using a variable thickness photomask material. Essentially, a thickness of an adjustable film layer is measured and converted into a contour map of film thickness over a region of a semiconductor body (e.g., wafer). An etch mask layer (e.g., photoresist) is then formed above the adjustable film layer and is selectively patterned by a reticleless exposure system (e.g., DMD exposure system). The selective patterning subjects different regions of the etch mask layer to varying exposure times dependent upon the thickness of the underlying adjustable film. The more etching needed to provide the underlying film to a nominal thickness, the longer the exposure of the etch mask. Therefore, the resultant etch mask, after exposure, comprises a topology allowing for various degrees of selective etching of the underlying film resulting in a uniform film.