Double Patterned Photoresist Formation via Single Exposure
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Solution Overview
Problem
Conventional methods for forming double patterned semiconductor structures, such as LELE and DDT processes, are complex and difficult to control, leading to increased processing complexity and cost, especially due to the need for multiple lithographic and etching processes.
Innovation Solution
A method involving the formation of a positive photoresist layer and a negative photoresist layer on a substrate, with a single exposure process using different intensity thresholds to create distinct exposure regions, followed by negative-tone and positive-tone development processes to form a double patterned structure, reducing the number of required processes and improving control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LELE process (two lithographic processes and two etching processes) is used to reduce pitch, then smaller pitch between neighboring components is achieved, but processing complexity increases
Solution Approach 1:
The patent combines two separate lithographic processes and two etching processes into a single integrated process. A multi-layer photoresist structure is formed where a first photoresist layer and a second photoresist layer are patterned simultaneously using one lithographic step, followed by a single etching process that uses both layers as masks to create the final double patterned structure. This merging reduces processing complexity while achieving the same pitch reduction.
Solution Approach 2:
The patent segments the photoresist system into multiple layers with different functions. The first photoresist layer serves as a primary mask while the second photoresist layer, formed with different solubility characteristics, serves as a secondary mask. This segmentation allows each layer to perform its specific function during the single lithographic and etching process, enabling complex patterning without requiring multiple separate process steps.
2Manufacturing precision
If DDT process (positive-tone development and negative-tone development) is used to form dual pattern, then pitch reduction is achieved, but process control becomes difficult
Solution Approach 1:
The patent applies local quality by creating a multi-layer photoresist structure where each layer has different solubility characteristics tailored to specific process steps. The first photoresist layer is designed to be soluble in a first developer but insoluble in a second developer, while the second photoresist layer exhibits the opposite solubility behavior. This localized differentiation of material properties allows each layer to be selectively removed or retained during sequential development steps, enabling precise pattern formation without the control issues of conventional DDT processes.
3Manufacturing precision
If multiple lithographic and etching processes are performed, then double patterned structure is formed, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple lithographic and etching processes into a single integrated process flow. By forming a multi-layer photoresist structure that can be patterned in one lithographic step and then etched in a single process using both layers as masks, the method eliminates the need for separate lithographic and etching steps required by conventional LELE processes, thereby reducing manufacturing cost while achieving the same double patterned structure.
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 method simplifies the formation of double patterned structures with improved accuracy and reduced manufacturing costs by using one exposure process and one photo mask, allowing for easy control of the development processes and achieving good topography.
Implementation Method 1
In the development process, portions of the photoresist are exposed by light penetrating through a photo mask and the chemical characteristics of the exposed portions of the photoresist layer may be changed.
Implementation Method 2
In a case that a positive photoresist layer is used, the exposed portions are altered from insoluble to soluble. In a case that a negative photoresist layer is used, the exposed portions are altered from soluble to insoluble.
Data Source
AI summary
A semiconductor structure including a double patterned structure and a method for forming the semiconductor structure are provided. A negative photoresist layer is formed on a positive photoresist layer, which is formed over a substrate. An exposure process is performed to form a first exposure region in the positive photoresist layer and to form a second exposure region in the negative photoresist layer in response to a first and a second intensity thresholds of the exposure energy. A negative-tone development process is performed to remove portions of the negative photoresist layer to form first opening(s). The positive photoresist layer is then etched along the first opening(s) to form second opening(s) therein. A positive-tone development process is performed to remove the first exposure region therefrom to form a double patterned positive photoresist layer.