Electron Beam Proximity Correction via Contrast Frames
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Solution Overview
Problem
Current electron beam lithography methods struggle to accurately control contrast and feature width for patterns with small critical dimensions due to the proximity effect, especially when feature sizes approach or exceed the alpha parameter of the Process Proximity Function (PPF), leading to inadequate imaging quality and limitations in semiconductor technology.
Innovation Solution
The method introduces geometrically induced dose correction by controlling contrast through a sizing parameter and utilizing a contrast stamp width, allowing for simultaneous control of contrast and critical dimensions during electron beam exposure, independent of traditional correction algorithms and calibration methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional proximity correction methods are used, then correction can be applied to patterns with larger critical dimensions, but imaging quality becomes inadequate for small critical dimensions (CDs < 1.3 times alpha parameter)
Solution Approach 1:
The patent applies parameter changes by modifying the correction algorithm to simultaneously control both contrast and critical dimensions. The new method introduces additional correction parameters beyond traditional dose adjustment, enabling independent control of contrast and CD for small features. This allows the system to achieve adequate imaging quality for CDs below 1.3 times the alpha parameter by adjusting multiple parameters in the correction function.
Solution Approach 2:
The correction process is segmented into distinct control components: one for contrast control and another for critical dimension control. This segmentation allows each aspect to be optimized independently and then combined, resolving the contradiction where traditional single-parameter correction cannot simultaneously satisfy both contrast and CD requirements for small features.
2Length of moving object
If feature sizes are reduced to meet semiconductor technology requirements, then smaller structures can be produced, but proximity effect distortion increases making patterns useless
Solution Approach 1:
The patent applies preliminary action by pre-calculating and applying proximity correction factors to each feature before exposure. The correction algorithm computes adjusted doses and geometry modifications in advance, compensating for expected proximity effect distortion. This allows small features to be exposed with pre-corrected parameters, ensuring accurate pattern formation despite the inherent proximity effect at small dimensions.
Solution Approach 2:
The correction method applies local quality by tailoring correction parameters to each individual feature's size, shape, and position relative to neighboring features. Instead of uniform correction, each small feature receives customized correction based on its specific proximity environment, enabling accurate reproduction of small structures while accounting for local dose distribution variations.
3Manufacturing precision
If dose control is applied to correct proximity effect, then critical dimensions can be maintained, but contrast control becomes insufficient for optimal imaging
Solution Approach 1:
The patent segments the correction function into distinct contrast control and critical dimension control components. This allows independent optimization of each aspect: dose adjustments for CD control and additional parameters for contrast control. The segmented approach ensures both CD accuracy and imaging reliability are achieved simultaneously, resolving the contradiction where single-parameter correction compromises one aspect for the other.
Solution Approach 2:
The method extends parameter control by introducing additional correction parameters beyond simple dose adjustment. These extra parameters enable independent control of contrast and CD, allowing the system to maintain optimal imaging reliability while preserving critical dimension accuracy. The enhanced parameter set provides the flexibility needed to satisfy both requirements simultaneously.
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 enables highly accurate imaging of patterns by maximizing contrast and maintaining consistent line widths, effectively extending the imaging limit beyond previous constraints, ensuring reliable production of small structures and preventing gap skipping in complex patterns.
Implementation Method 1
The exposure of a resist with an electron beam of a certain shape (Gaussian profile beam or shaped beam or multi-pixel beam) produces a dose distribution in the resist which does not correspond to the dose profile for the electron beam. The reason for that is the scattering of the electrons by the atoms or molecules of the resist and the substrate.
Implementation Method 2
The required pattern is broken down into small elementary figures and projected onto a layer of photosensitive dye
Data Source
AI summary
A method of electron beam lithography for producing wafers and masks. To reduce the impacts of the disturbing proximity effect, an expanded correction algorithm that enables a more accurate correction is used to control the electron beam. To create an improved correction method by means of which the contrast and the feature width (CD) of all figures of a pattern can be optimally controlled additional contrast frames (KR) and remaining figures (R) are produced using a geometric method for the purpose of contrast control with respect to all figures (F). Then smaller figures (KRsize-S and Rsize-S) are produced from the contrast frame figures (KR) and remaining figures (R) by means of a negative sizing operation, and subsequently figures (KRsize-S and Rsize-S) are transferred to the proximity correction algorithm with the condition that the resist threshold is reached at the edges of the figures (KR, R) by the dose assignment.