Mask Venting for High Topography Semiconductor Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for applying mask layers over substrates with high surface topography, such as MEMS sensors or TSVs, often result in gas trapped in cavities leading to mask rupture due to pressure differences during etching steps, which compromises the integrity of the mask layer and the etching process.
Innovation Solution
A method involving the application of a mask layer with strategically placed openings to allow gas trapped in cavities to escape, thereby balancing internal and external pressures and preventing mask rupture, utilizing dry film technology and lamination techniques to manage high aspect ratio topographies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mask layer is applied continuously over holes or trenches to cover the entire substrate surface, then the mask provides complete coverage and protection, but gas trapped in the cavities creates pressure differences that cause mask rupture
Solution Approach 1:
The mask layer is segmented by introducing discrete openings (vents) at specific locations away from the trenches. This segmentation allows the mask to maintain continuous coverage over the substrate while creating controlled pathways for gas escape, preventing pressure buildup that would cause rupture.
Solution Approach 2:
The openings in the mask layer act as intermediary elements between the trapped gas in the cavities and the external environment. These openings provide a controlled interface for gas to escape gradually, mediating the pressure difference that would otherwise cause sudden mask rupture.
2Reliability
If openings are created in the mask layer to allow gas escape, then pressure differences are balanced and mask rupture is prevented, but the mask coverage is reduced and etching precision may be compromised
Solution Approach 1:
The mask layer has different properties in different locations: continuous and dense over the trenches for precise etching protection, and with localized openings in specific areas away from the trenches for gas escape. This local quality differentiation allows the mask to simultaneously provide precise etching definition and pressure relief.
Solution Approach 2:
The mask is segmented into functional zones: continuous coverage regions for etching protection and discrete opening regions for pressure relief. The openings are strategically positioned away from the trench areas to be etched, ensuring they do not interfere with etching precision while still providing gas escape pathways.
3Ease of manufacture
If vacuum coating or spray coating is used to apply mask layers, then the mask can be applied conformally to complex topographies, but the process complexity and time consumption increase
Solution Approach 1:
The mask layer is applied as a complete planar layer covering the entire substrate surface before any openings are created. This preliminary continuous application simplifies the manufacturing process by using a single straightforward deposition step, avoiding the need for complex conformal coating techniques on the topography itself.
Solution Approach 2:
The openings in the mask layer are created by removing material from the previously applied continuous mask layer, rather than attempting to deposit the mask in a complex conformal pattern. This extraction approach simplifies the overall manufacturing process by separating the deposition and opening-creation steps.
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
Enables the processing of deep etched features up to 500 μm without mask rupture or delamination, ensuring high throughput and maintaining mask quality, even on critical topographies, by using venting features to manage sub-atmospheric pressure conditions.
Implementation Method 1
when the difference between the pressure exerted on the mask by the gas and a pressure exerted on the mask from outside the recess or trench is larger than a predefined value
Data Source
AI summary
The method comprises the steps of providing a semiconductor body or substrate (1) with a recess or trench (2) in a main surface (10), applying a mask (3) on the main surface, the mask covering the recess or trench, so that the walls and bottom of the recess or trench and the mask together enclose a cavity (4), which is filled with a gas, and forming at least one opening (5) in the mask at a distance from the recess or trench, the distance (6) being adapted to allow the gas to escape from the cavity via the opening when the gas pressure exceeds an external pressure.