Litho-Litho-Etch Double Patterning Single Resist Layer
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Solution Overview
Problem
Current double patterning methods for semiconductor devices, such as LELE, are expensive due to doubled process steps in the lithography flow, and methods like SADP and SAQP have limited design flexibility and are not suitable for complex metal layers or hole-type patterns.
Innovation Solution
A double patterning method involving a sole resist layer with increased solubility in positive developers upon exposure to a first radiant energy density of UV rays and decreased solubility in negative developers upon exposure to a higher second radiant energy density, allowing for a single resist coating step, two exposure steps, and two development steps, which simplifies the lithography flow and enhances design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LELE double patterning is used to achieve pitch reduction and complex pattern formation, then manufacturing precision is improved, but device complexity and cost increase due to doubled process steps
Solution Approach 1:
The patent combines two separate resist coating steps into a single resist coating step, where one resist layer serves dual purposes for both exposure steps. This merging reduces the number of process steps while maintaining the ability to achieve pitch reduction and complex pattern formation through sequential exposures at different energy densities.
Solution Approach 2:
The single resist layer formed in the patent serves multiple functions: it acts as the resist for both the first exposure at lower energy density and the second exposure at higher energy density. This multi-functional resist layer eliminates the need for separate resist coatings, thereby reducing process complexity while maintaining manufacturing precision.
2Device complexity
If SADP or SAQP is used to simplify the lithography flow, then device complexity is reduced, but adaptability and design flexibility are limited for complex metal layers and hole-type patterns
Solution Approach 1:
The patent employs dynamic control of exposure energy densities, using a first lower energy density for the initial exposure and a second higher energy density for the subsequent exposure. This dynamic approach allows the same resist layer to respond differently to each exposure, enabling complex pattern formation and hole-type patterns while maintaining a simplified single-coating lithography flow.
Solution Approach 2:
The patent changes the exposure parameter (energy density) between the two exposure steps. The first exposure uses a lower energy density to form initial patterns, while the second exposure uses a higher energy density to create additional features and holes. This parameter change enables the process to achieve high adaptability and design flexibility without requiring multiple resist coatings.
3Manufacturing precision
If multiple resist coating steps are used in LELE, then manufacturing precision is maintained, but productivity decreases due to increased process time
Solution Approach 1:
The patent merges two separate resist coating operations into a single coating step, directly reducing the total process time and improving productivity. The single resist layer is then used for both exposure steps, maintaining pattern formation accuracy while eliminating the time penalty associated with multiple coating cycles.
Solution Approach 2:
The patent performs a preliminary single resist coating that prepares the resist layer for both subsequent exposure steps. This preliminary action ensures that the resist is optimally prepared before either exposure, maintaining manufacturing precision while avoiding the need for a second coating operation, thereby improving overall process speed.
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 complexity and cost of the lithography process, achieves uniform acid distribution, and allows for the creation of both unidirectional and multidirectional resist features with critical dimensions below 28 nanometers, offering improved design flexibility and reduced resist layer thickness loss.
Implementation Method 1
solubility of the resist composition in a positive developer increases upon irradiation with ultraviolet (UV) rays of a first radiant energy density and solubility of the resist composition in a negative developer decreases upon irradiation with UV rays of a second radiant energy density
Data Source
AI summary
A litho-litho-etch double patterning method including forming a resist layer by coating a substrate with a resist composition; exposing the resist layer to a first radiant energy density of UV rays; forming a first pattern in the resist layer by developing the resist layer with a positive developer; exposing the resist layer to a second radiant energy density of UV rays; and forming a second pattern in the resist layer by developing the resist layer with a negative developer, the second pattern including one or more features of the first pattern.