Anti-Spacer Process for Sub-Resolution Semiconductor Features
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Solution Overview
Problem
Conventional photolithography techniques have limitations in forming features with dimensions below a certain critical size due to optics limitations and radiation wavelength constraints, making it difficult to achieve sub-resolution features in semiconductor devices.
Innovation Solution
The anti-spacer process is used to form features by chemically modifying the outer portions of a photosensitive material, removing them to create trenches and openings, and then using additional mask materials to expose the substrate, allowing for the formation of features with sizes and pitches below the resolution limits of conventional photolithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography techniques are used, then features can be formed with standard dimensions, but features with critical dimensions below 37.5 nm cannot be reliably formed due to optics limitations and radiation wavelength constraints
Solution Approach 1:
The process segments feature formation into multiple steps: first forming a mandrel pattern at a larger pitch, then forming spacers on mandrel sidewalls, removing mandrels, and repeating the process to achieve sub-37.5 nm critical dimensions. This segmentation allows each step to operate within reliable photolithography limits while achieving smaller final dimensions
Solution Approach 2:
The invention uses the vertical dimension by forming three-dimensional spacer structures on mandrel sidewalls. The spacer thickness, controlled by conformal deposition, defines the final feature dimension, transitioning from two-dimensional planar lithography to three-dimensional structure-based dimensioning
2Manufacturing precision
If pitch multiplication techniques are used to form features smaller than photolithography limits, then sub-resolution features can be achieved, but the process complexity and number of process acts increase significantly
Solution Approach 1:
The invention merges multiple functions into single process acts where possible. For example, the same spacer formation and mandrel removal process is used for both pitch doubling and pitch quadrupling, and the chemically amplified resist serves both as the initial pattern definition and as the material from which spacers are formed
Solution Approach 2:
The process uses parameter changes in the chemically amplified resist - specifically, changing its solubility state through chemical amplification - to enable selective removal of mandrels while preserving spacers. The resist transitions from an insoluble state during spacer formation to a soluble state for mandrel removal, reducing process complexity
3Productivity
If the number of features per area is increased to increase device capacity, then device capacity increases, but the pitch between features must be reduced below conventional photolithography limits
Solution Approach 1:
The invention performs preliminary action by first forming mandrels at a larger, photolithography-friendly pitch, then using spacer formation to multiply the feature count. This preliminary patterning at relaxed dimensions enables subsequent high-density feature formation without directly lithographing the final small-pitch pattern
Solution Approach 2:
The mandrel structures serve as intermediaries that enable the formation of final features at smaller pitches. The mandrels are formed at larger dimensions using conventional photolithography, then act as templates for spacer formation, ultimately allowing high-density feature patterns to be achieved through the intermediary mandrel-spacer relationship
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 reduces the complexity and cost of forming sub-resolution features compared to conventional pitch multiplication techniques, enabling the creation of features with critical dimensions as small as 25 to 30 nm and pitches between 30 to 80 nm, which are not achievable with standard photolithography.
Implementation Method 1
photolithography is performed by forming a photosensitive material (e.g., a photoresist) over another material. Using a so-called 'positive tone' photosensitive material, radiation of an appropriate wavelength is directed onto portions of the photosensitive material that are to be removed. The radiation chemically alters the photosensitive material to enable the photosensitive material to be soluble in and removed by a solution
Implementation Method 2
The chemically active species may be applied by conventional techniques, such as by spin-coating a solution of the chemically active species over the structure. The chemically active species may be diffused into the outer portion, such as by application of heat for a predetermined amount of time
Data Source
AI summary
Methods of forming semiconductor devices and features in semiconductor device structures include conducting an anti-spacer process to remove portions of a first mask material to form first openings extending in a first direction. Another anti-spacer process is conducted to remove portions of the first mask material to form second openings extending in a second direction at an angle to the first direction. Portions of a second mask material underlying the first mask material at intersections of the first openings and second openings are removed to form holes in the second mask material and to expose a substrate underlying the second mask material.