Photomask Fabrication Using Segmented Resist Layers
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Solution Overview
Problem
Existing photomask fabrication processes face challenges in accurately forming light blocking and phase shifting patterns due to the difficulty in achieving sufficient resist layer thickness for precise patterning, which affects the accuracy of these patterns and makes it hard to minimize feature sizes in semiconductor devices.
Innovation Solution
A method involving a photomask blank with sequentially stacked layers including a phase shifting layer, multiple light blocking layers, and resist layers, where the resist patterns are used as etch masks to pattern the light blocking and phase shifting layers, allowing for selective removal of layers to achieve precise pattern formation with thinner resist layers for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the resist layer is increased to improve the accuracy of light blocking and phase shifting patterns, then the accuracy of pattern formation is improved, but it becomes more difficult to accurately pattern the resist layer
Solution Approach 1:
The patent divides the single resist layer into multiple resist layers (first resist layer and second resist layer) with different thicknesses. The second resist layer has a greater thickness to serve as an etch buffer, while the first resist layer has a smaller thickness to enable accurate patterning. This segmentation allows each layer to fulfill its specific function without compromise.
Solution Approach 2:
Different regions of the resist structure are assigned different thicknesses based on their functional requirements. The second resist layer (etch buffer) is made thicker to protect underlying layers during etching, while the first resist layer (patterning layer) is made thinner to achieve precise pattern definition. This local differentiation of quality resolves the contradiction between buffer thickness and patterning accuracy.
2Reliability
If a sufficient thickness of resist layer is used to accommodate etch processes, then the etch buffer function is improved, but the accuracy of resist pattern formation deteriorates
Solution Approach 1:
The resist system is segmented into two distinct layers: the first resist layer optimized for accurate pattern formation and the second resist layer optimized for etch buffering. This segmentation allows the etch buffer function to be fulfilled by the thicker second layer while the thinner first layer maintains high patterning accuracy.
Solution Approach 2:
The solution moves from a single-dimensional thickness parameter to a two-layer vertical structure. By adding the dimensional aspect of layer differentiation, the system can simultaneously optimize for both etch buffer thickness and patterning accuracy, which are conflicting requirements in a single-layer system.
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 enables the formation of accurate and fine patterns with controlled thickness, enhancing the precision of light blocking and phase shifting patterns, thereby improving the fabrication of photomasks for advanced semiconductor devices.
Implementation Method 1
The second light blocking patterns are formed by patterning the second light blocking layer using an etch process employing the second resist patterns as etch masks
Data Source
AI summary
A method of fabricating a photomask comprising providing a photomask blank including a phase shifting layer, a first light blocking layer, a first resist layer, a second light blocking layer and a second resist layer stacked sequentially in this order on a substrate, forming second resist patterns, forming second light blocking patterns, forming first resist patterns, forming first light blocking patterns and phase shifting patterns, removing the first resist patterns, and selectively removing at least one of the first light blocking patterns, wherein the second resist layer has a thickness such that all of the second resist layer is removed while the first resist layer is patterned for exposing the second light blocking layer.