Spin-On Film Planarization for Uniform Lithography Thickness
Solution Overview
Problem
The challenge in semiconductor fabrication is the non-planar topography of substrates, which causes thickness variations in spin-on films like photoresist, affecting the critical dimension resolution and integrity of lithography processes due to interactions with varying heights and geometries.
Innovation Solution
A method involving the deposition of a solubility-shifting agent layer on the substrate, followed by exposure to a patterned actinic radiation to change solubility based on topography, allowing for selective removal of soluble portions and subsequent deposition of a more planar second layer using spin-on deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spin-on deposition is used to deposit photoresist on a substrate with non-planar topography, then the deposition process is simple and fast, but the film thickness becomes non-uniform due to interactions with varying heights
Solution Approach 1:
A planarization layer is deposited beforehand on the substrate with non-planar topography to create a planar surface before photoresist deposition. This preliminary action eliminates the topography-induced thickness variations while allowing the subsequent spin-on process to proceed at high speed without compromising film uniformity.
2Ease of manufacture
If conventional lithography is used on substrates with varying topography, then the process is straightforward, but critical dimension resolution deteriorates due to focus variations
Solution Approach 1:
The substrate surface is planarized before lithography by depositing a planarization layer that compensates for topography variations. This preliminary surface preparation maintains focus uniformity across the wafer during conventional lithography, preserving critical dimension resolution while keeping the lithography process itself simple and straightforward.
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 improves the planarity of the substrate surface, reducing height differences and enhancing the uniformity of film thickness, thereby improving the critical dimension resolution and integrity of lithographic patterns.
Implementation Method 1
exposing the first layer to a first pattern of actinic radiation, the first pattern of actinic radiation changing a solubility of the first layer
Implementation Method 2
depositing a first layer on the working surface of the substrate by spin-on deposition
Data Source
AI summary
A method for planarizing a substrate includes: receiving a substrate having microfabricated structures that differ in height across the working surface of the substrate that define a non-planar topography, depositing a first layer that includes a solubility-shifting agent on the working surface of the substrate by spin-on deposition in a non-planar fashion, exposing the first layer to a first pattern of actinic radiation based on the topography, developing the first layer using a predetermined solvent, and depositing a second layer over the working surface of the substrate that has a greater planarity as compared to the first layer prior to developing the first layer. The first pattern of radiation changes a solubility of the first layer such that upper regions of the non-planar topography of the first layer are soluble to the predetermined solvent.