Near-Infrared Absorptive Layer for Lithography Focus Accuracy
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Solution Overview
Problem
In optical lithography, the accuracy of focus detection is degraded due to infrared light transmission through the photoresist layer, leading to poor image contrast and pattern formation in semiconductor microfabrication, especially with the use of ArF excimer laser radiation.
Innovation Solution
A near-infrared absorptive layer is introduced beneath the photoresist layer, composed of a polymer with specific repeat units, an aromatic ring-containing polymer, and a near-infrared absorbing dye, which absorbs near-infrared light to prevent reflection and improve solvent resistance, allowing for accurate auto-focusing without modifying existing semiconductor manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photoresist layer is used in optical lithography, then the photoresist pattern can be formed, but infrared light is transmitted through the photoresist layer causing degraded focus detection accuracy
Solution Approach 1:
A near-infrared absorptive layer is introduced as an intermediary component between the substrate and the photoresist layer. This layer absorbs near-infrared light used for focus detection, preventing it from transmitting through the photoresist layer and reaching the substrate surface, thereby eliminating the harmful effect of transmitted infrared light on focus detection accuracy.
Solution Approach 2:
The system is segmented into distinct functional layers: the near-infrared absorptive layer is separated from the photoresist layer to perform the specific function of absorbing near-infrared light. This segmentation allows the photoresist layer to maintain its photoresist properties while the absorptive layer handles the infrared absorption, resolving the contradiction between pattern formation and infrared light transmission.
2Measurement precision
If a near-infrared absorbing dye is added to the photoresist layer, then focus detection accuracy is improved, but the resolution of the photoresist film is degraded
Solution Approach 1:
The near-infrared absorptive layer is segmented as a separate layer from the photoresist layer. This separation ensures that the near-infrared absorbing dye is not mixed with the photoresist material, thereby preventing any degradation of photoresist film resolution while still achieving improved focus detection accuracy through the dedicated absorptive layer.
Solution Approach 2:
The near-infrared absorptive layer serves as an intermediary that handles the near-infrared absorption function, allowing the photoresist layer to focus solely on its primary function of pattern formation with high resolution. This mediator approach eliminates the trade-off between focus detection accuracy and photoresist resolution.
3Ease of operation
If near-infrared light is used for focus detection, then the wafer position can be detected, but the transmitted light is reflected by the substrate surface causing degraded focus detection accuracy
Solution Approach 1:
The near-infrared absorptive layer converts the harmful effect of near-infrared light transmission into a beneficial outcome. By absorbing the near-infrared light, it prevents the light from reaching the substrate surface where it would be reflected and cause measurement errors. The absorbed light energy is converted into heat, which is then dissipated, transforming the potential harmful transmission and reflection into a useful absorption that improves focus detection accuracy.
4Adaptability or versatility
If the substrate has a multilayer structure with patterned metal and dielectric material, then the semiconductor device functionality is achieved, but the reflection of infrared light becomes complex making focus detection difficult
Solution Approach 1:
The near-infrared absorptive layer acts as an intermediary that simplifies the optical interaction with complex multilayer substrates. By absorbing near-infrared light before it reaches the complex patterned metal and dielectric material layers, it eliminates the complex reflections that would otherwise make focus detection difficult, while still allowing the substrate to maintain its required multilayer structure for semiconductor device functionality.
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 solution enhances the accuracy of optical auto-focusing and improves the contrast of the projected image, enabling better photoresist pattern formation by preventing near-infrared light from entering the focus detection system, thus addressing the degradation of focus detection accuracy.
Implementation Method 1
a near-infrared absorptive layer which is composed of a polymer comprising repeat units of formula (1) to (4), an aromatic ring-containing polymer, and a near-infrared absorbing dye
Implementation Method 2
the position of the top surface of the wafer is determined by reflecting infrared light on the wafer top surface and detecting the reflected light
Data Source
AI summary
A composition comprising a polymer comprising repeat units selected from formulae (1) to (4), an aromatic ring-containing polymer, a near-infrared absorbing dye, and a solvent is used to form a near-infrared absorptive film. R1, R7, R9, and R14 are H, methyl, fluorine or trifluoromethyl, R2 to R6 are H, F, trifluoromethyl, —C(CF3)2OR16, alkyl or alkoxy, at least one of R2 to R6 being F or a fluorinated group, R16, R8 and R13 are H or a monovalent organic group, L1 is a single bond or —C(═O)O—, m is 0 or 1, L2 is a di- or trivalent hydrocarbon group, n is 1 or 2, R10 to R12 are H, hydroxyl, halogen or a monovalent organic group, and R15 is a fluorinated C2-C15 hydrocarbon group.