Planarizing Substrate Coatings via Vibration and Controlled Drying
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Solution Overview
Problem
Conformal coatings in semiconductor manufacturing often result in non-uniform thickness over topographically dense and isolated areas, leading to inconsistencies and errors in subsequent processing steps, such as poor focus leveling and non-uniform loading during chemical-mechanical polishing.
Innovation Solution
A method and apparatus for applying a planar substrate coating using a coating chamber with a platen that rotates and vibrates the wafer to ensure even distribution of the coating, followed by controlled drying to achieve a substantially planar top surface, utilizing a thickness monitor to measure and adjust the coating thickness, and potentially applying a second coating to compensate for variances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conformal coating is applied to substrates with topographical features, then complete coverage over all features is achieved, but non-uniform thickness and non-planar top surface result
Solution Approach 1:
The coating is applied in a liquid state before drying, allowing the coating material to flow and self-level over topographical features. This preliminary liquid state action enables the coating to conform to the substrate shape while maintaining thickness uniformity, which is then locked in during the drying process.
Solution Approach 2:
The patent controls the drying process parameters (temperature, time, atmosphere) to achieve planarization. By carefully managing the drying conditions, the coating transitions from a liquid state that conforms to topography to a solid state with a planar top surface, resolving the contradiction between coverage and planarity.
2Productivity
If spin-drying is used to dry the coating, then drying efficiency is improved, but coating uniformity and planarity deteriorate
Solution Approach 1:
The patent extracts the drying function from the spin-coating process. Instead of using spin-drying that creates centrifugal forces and thickness variations, the coating is dried in place using controlled environmental conditions, separating the coating application and drying operations to maintain uniformity.
Solution Approach 2:
The mechanical spin-drying system is replaced with a controlled thermal or atmospheric drying process. This substitution eliminates the centrifugal forces that cause non-uniformity while maintaining drying efficiency through controlled temperature and atmosphere conditions.
3Productivity
If high aspect ratio topographic features are present on the substrate, then device integration density is improved, but coating non-uniformity increases
Solution Approach 1:
The coating is applied in a liquid state that allows it to flow into and conform to high aspect ratio features before drying. This preliminary liquid application ensures complete coverage of dense topography, and the subsequent controlled drying preserves the uniform thickness achieved during the liquid state.
Solution Approach 2:
The patent modifies the drying parameters (temperature gradient, atmosphere composition, drying time) to prevent premature solidification that would trap non-uniformities. By controlling these parameters, the coating maintains its ability to conform to high aspect ratio features while achieving uniform final 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
This approach results in a more accurate and consistent coating process, reducing errors in photolithographic masking and post-passivation interconnect formation by maintaining a flat top surface, thereby improving the performance and accuracy of subsequent processing steps.
Implementation Method 1
a platen that rotates and vibrates the wafer to ensure even distribution of the coating
Implementation Method 2
A coating nozzle is disposed in the coating chamber and is configured to deliver a first coating to the wafer
Implementation Method 3
The coating chamber may be configured to dry the first coating on the wafer with a substantially planar top surface
Data Source
AI summary
A method of forming a coating, comprises applying a first coating to a substrate having a plurality of topographical features, planarizing a top surface of the first coating, and drying the first coating after planarizing the top surface. The first coating may be applied over the plurality of topographical features, and may be substantially liquid during application. The first coating may optionally be a conformal coating over topographical features of the substrate. The conformal coating may be dried prior to planarizing the top surface of the first coating. A solvent may be applied to the conformal coating, with the top surface of the conformal coating being substantially planar after application of the solvent. The first coating may have a planar surface prior to drying the first coating, and the first coating may be dried without substantial spin-drying by modifying an environment of the first coating.