Self-Aligned Pad Mask Creation via Spacer Overlap in Double Patterning
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Solution Overview
Problem
The challenge in integrated circuit design is achieving accurate alignment of small, closely spaced features on a semiconductor substrate using multiple masks, particularly in double patterning technology, where misalignments can result in misconnections and shorts due to the limitations of photolithography processes.
Innovation Solution
The solution involves a self-aligned double patterning process that uses a core mask and a pad mask to ensure proper alignment of features, where the pad features are reduced on all sides by the minimum spacer width and included in the core mask, allowing them to overlap with the spacer material pattern, eliminating the need for exact alignment of the pad mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate masks are used for small features and larger features in double patterning, then feature diversity is achieved, but alignment precision deteriorates due to difficulty in exact alignment between masks
Solution Approach 1:
The patent merges the alignment function into the spacer formation process itself. The first mask defines mandrels that generate spacers, and the second mask aligns to these spacers rather than to features on the first mask. This combining of the alignment reference (spacers) with the patterning process resolves the contradiction by achieving both feature diversity through multiple masks and alignment precision through self-alignment to spacers.
Solution Approach 2:
The spacer acts as an intermediary element between the two masks. Instead of directly aligning the second mask to features on the first mask (which causes misalignment), the spacer serves as an intermediate reference structure that the second mask aligns to, thereby achieving precise alignment while maintaining feature diversity.
2Ease of manufacture
If photolithography process constraints are accepted, then manufacturing feasibility is maintained, but alignment accuracy deteriorates for small closely spaced features
Solution Approach 1:
The patent segments the patterning process into distinct stages: first mask defines mandrels, then spacers are formed around mandrels, and finally the second mask patterns based on spacer positions. This segmentation allows each step to be optimized independently, maintaining manufacturing feasibility while achieving high alignment accuracy through the spacer-mediated self-alignment process.
Solution Approach 2:
The spacer formation is performed as a preliminary action before the second mask patterning. By pre-forming spacers that serve as alignment references, the patent enables the second mask to be accurately positioned without requiring direct alignment to the first mask features, thereby overcoming photolithography alignment limitations while maintaining manufacturing feasibility.
Data Source
AI summary
A system and method provide semiconductor fabrication mask creation techniques that align the device features patterned with a first core mask with one or more pad features patterned with a subsequent pad mask. Shapes representing the pad features may be included in the core mask by reducing on all sides, the shape of the pad feature in the core mask by the width of the spacer material. A pad mask then may be created to include a shape of the pad feature that may overlap a portion of the spacer material pattern created by the shape of the pad feature in the core mask. Data sets may be generated from a circuit design to create the masks that may be fabricated with the described techniques.