Back Alignment Mark Detection Using Infrared Light
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Solution Overview
Problem
Conventional semiconductor manufacturing methods face challenges in achieving high alignment accuracy and flexibility due to limitations in back alignment mark detection, particularly when patterns are dense or have similar shapes, leading to reduced chip yield and increased ineffective region area.
Innovation Solution
A method involving the formation of a back alignment mark on a semiconductor substrate using a step created by trenches or a groove in a stacked film, with infrared light detection to improve alignment accuracy without increasing mark size or ineffective region area, allowing for flexible layout design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of the back alignment mark is increased to improve detection accuracy, then the detection accuracy is improved, but the ineffective region area increases
Solution Approach 1:
The patent changes the detection parameter from visible light to infrared light, which enables high-contrast detection of the back alignment mark without requiring an increase in mark size. This parameter change resolves the contradiction by improving detection accuracy through wavelength selection rather than through increasing the physical dimensions of the alignment mark.
2Ease of manufacture
If conventional detection methods are used for dense patterns, then the manufacturing process is simple, but the alignment accuracy decreases
Solution Approach 1:
The patent employs infrared light detection to enhance alignment accuracy for dense patterns while preserving the simplicity of the manufacturing process. The infrared detection method provides high contrast for dense patterns without adding complex manufacturing steps, thus resolving the contradiction between ease of manufacture and measurement precision.
3Measurement precision
If the ineffective region area is increased to accommodate larger alignment marks, then the detection accuracy is improved, but the chip yield decreases
Solution Approach 1:
By changing the detection wavelength to infrared, the patent achieves high detection accuracy with a compact alignment mark, thereby maintaining chip yield. The infrared detection method allows for accurate alignment mark detection within a smaller area, preventing the need to expand the ineffective region and preserving productive wafer area for chip fabrication.
4Device complexity
If visible light detection is used for alignment, then the detection system is simple, but the alignment accuracy is insufficient for dense patterns
Solution Approach 1:
The patent transitions from visible light to infrared light detection, which provides superior alignment accuracy for dense patterns. While this changes the detection parameter, the overall system complexity remains manageable as it primarily involves selecting appropriate infrared light sources and detectors, without requiring fundamentally new detection system architectures.
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
Enhances detection accuracy of the back alignment mark, maintaining chip yield while allowing for flexible layout design by using infrared light to detect the mark's position without enlarging the mark or widening the ineffective region.
Implementation Method 1
irradiating light having a wavelength in a predetermined wavelength region, the light being irradiated on the semiconductor substrate, from the second main surface of the semiconductor substrate, and detecting reflected light or transmitted light of the light by a detector disposed at a predetermined position
Implementation Method 2
detecting reflected light or transmitted light of the light by a detector disposed at a predetermined position
Data Source
AI summary
A back alignment mark on a surface of a semiconductor substrate is detected and a resist mask patterned into a circuit pattern corresponding to a surface element structure is formed on a back of the semiconductor substrate. Detection of the back alignment mark is performed by using a detector opposing the back of the semiconductor substrate and measuring contrast based on the intensity of reflected infrared light irradiated from the back of the semiconductor substrate. The back alignment mark is configured by a step formed by the surface of the semiconductor substrate and bottoms of trenches formed from the surface of the semiconductor substrate. A polysilicon film is embedded in the trenches. The back alignment mark has, for example, a cross-shaped planar layout in which three or more trenches are disposed in a direction parallel to the surface of the semiconductor substrate.