Positive Photoresist Patterning via Partial and Flood Exposure
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Solution Overview
Problem
The existing methods for patterning positive photoresist in integrated circuit fabrication are time-consuming due to the need for precise and lengthy exposure processes using expensive equipment, which limits the throughput of lithographic tools.
Innovation Solution
A method combining a patterned exposure with a dose below the Dose To Critical Dimension (Dose To CD) followed by a flood exposure at a dose below Dose To Clear (E0), allowing for reduced exposure times and increased efficiency in patterning positive photoresist, potentially using the same or different tools for these exposures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional photolithography exposure methods are used to pattern photoresist, then pattern resolution and manufacturing precision are achieved, but exposure time increases and productivity decreases
Solution Approach 1:
The exposure process is segmented into two distinct stages: a patterned exposure stage using a reticle to define the pattern, and a flood exposure stage to complete the dosing. This segmentation allows the patterned exposure to be performed at high speed with full pattern definition, while the flood exposure completes the process quickly, thereby reducing total exposure time while maintaining pattern resolution.
Solution Approach 2:
The patterned exposure is performed first as a preliminary action, establishing the pattern definition at a dose below Dose To CD. This preliminary patterning is followed by a flood exposure that completes the dosing to Dose To Clear. By performing the pattern-defining action first at optimized dose levels, the overall process time is reduced while maintaining resolution.
2Manufacturing precision
If full dose exposure is applied to pattern photoresist, then pattern definition is achieved, but exposure time increases
Solution Approach 1:
The method applies partial action by using a patterned exposure dose below Dose To CD (not full dose) to establish the pattern definition. This partial dosing is then completed by a flood exposure to reach Dose To Clear. This approach reduces the time required for patterned exposure while still achieving complete pattern definition through the combination of both exposure stages.
3Manufacturing precision
If expensive lithographic equipment is used for precise patterning, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The flood exposure stage can be performed using the same lithographic equipment that performed the patterned exposure, or potentially different equipment. This multi-functionality approach allows the system to handle both patterned and flood exposure tasks, reducing the need for specialized separate equipment and thereby reducing overall device complexity while maintaining patterning accuracy.
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 reduces the time required for each patterning step, enhancing the throughput of lithographic tools and potentially lowering costs by allowing larger areas to be exposed in a flood mode, while maintaining pattern resolution and usability of the photoresist as a mask.
Implementation Method 1
A method of patterning positive photoresist combines a patterned exposure with a dose below a Dose To Critical Dimension (Dose To CD) with a flood exposure at a dose below Dose To Clear (E0)
Implementation Method 2
the area is subjected to a flood exposing to activating radiation at a dose below E0
Data Source
AI summary
A method of patterning positive photoresist includes providing positive photoresist over a substrate. An area of the positive photoresist is exposed to a pattern of activating radiation at a dose which is below the Dose To CD of the pattern with the positive photoresist. The area of the positive photoresist is flood exposed to activating radiation at a dose from 1% to 75% of E0. A sum of the flood dose and the pattern dose is less than the Dose To CD yet effective to resolve the pattern in the positive photoresist upon develop. After exposing the area to the flood dose and the pattern dose, the area of the positive photoresist is developed to resolve the pattern in the positive photoresist. Other embodiments are contemplated.