Solubility-Switch Fill Material for Deep Trench Lithography
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Solution Overview
Problem
Conventional methods for filling deep trenches or recessed topographies in semiconductor substrates are inefficient, requiring multiple coat/bake/develop steps and are unsuitable for recent processes, leading to throughput issues and resist peeling, cracking, or scumming.
Innovation Solution
A solubility-switching method using a fill composition that undergoes controlled solvent evaporation and crosslinking, allowing for selective deposition and removal of the fill material at different processing stages, including a soft bake to form a crosslinked material and a solubility switch to make it soluble again for photoresist application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DBARC is used to fill deep trenches before applying photoresist, then the topography is filled and photoresist can be applied, but multiple coat/bake/develop steps are required which substantially reduces throughput
Solution Approach 1:
The fill material undergoes a solubility parameter change through thermal treatment. Initially, the fill material is soluble and can be removed by developer solvent. After heating to a specific temperature range, the fill material becomes insoluble and resistant to developer solvent, allowing photoresist to be applied without peeling or cracking while eliminating the need for multiple DBARC steps
Solution Approach 2:
The fill material is applied and heated in advance to transform its solubility characteristics before photoresist application. This preliminary thermal treatment creates the necessary topographic fill with appropriate solubility properties, eliminating the need for subsequent DBARC removal steps and improving throughput
2Productivity
If photoresist is applied directly over deep trenches without filling, then throughput is maintained, but resist peeling, cracking, bending, or scumming occurs in the bottom of recessed areas
Solution Approach 1:
The fill material's solubility parameter is changed by thermal treatment to create an insoluble state that provides mechanical support for the photoresist layer. This prevents photoresist peeling, cracking, bending, or scumming in deep trenches while maintaining a simplified process that improves throughput
3Manufacturing precision
If multiple DBARC coat/bake/develop steps are used to fill deep topography, then the topography is adequately filled, but the process is complex and not suitable for recent deeper topographies
Solution Approach 1:
A single fill material application followed by thermal treatment changes the solubility parameter from soluble to insoluble, creating adequate topographic fill in one step. This eliminates the complexity of multiple DBARC coat/bake/develop steps while achieving the necessary fill quality for recent deeper topographies
Solution Approach 2:
The fill material is applied and thermally treated in advance to achieve the required fill depth and solubility transformation before photoresist application. This preliminary action consolidates multiple steps into one, reducing process complexity while maintaining fill quality
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 fills deep trenches with minimal strain on the photoresist, preventing cracking and deformation, and allows for efficient pattern transfer without plasma etching, enhancing throughput and substrate integrity.
Implementation Method 1
The fill composition is heated to about the evaporation temperature or higher, but lower than the crosslinking temperature, so as to remove at least some of the solvent system and form a dried composition
Implementation Method 2
heating the dried composition to the crosslinking temperature or higher so as to cause the component to crosslink and form a crosslinked fill material that is substantially insoluble in the developer solvent
Implementation Method 3
The crosslinked fill material is heated at a temperature that is about 10° C. or more above the crosslinking temperature for a sufficient time so as to cause the crosslinked fill material to become soluble in the developer solvent and form a soluble fill material
Data Source
AI summary
Materials and methods are described for filling deep trenches and other topography using a single coating of a topographic fill material and a single develop back step while maintaining a thickness that can be controlled and is sufficient to fill very deep topographies to the extent needed for lithographic patterning. The materials are designed for selective changes to their solubility, and the methods involve using this feature to achieve selective removal of desired amounts of the topographic fill material at various stages of the process. This allows more efficient processing and higher throughput for lithographic applications in which a photoresist is applied over deep topography while addressing the problems of resist cracking, bending, peeling, or scumming.