Curved MEMS Reflective Layer for Broadband Infrared Absorption
Solution Overview
Problem
Existing microbolometers have limited infrared absorption across a wide band due to a fixed distance between the absorption plate and reflector, resulting in maximum absorption at a specific wavelength, which restricts their sensitivity and effectiveness.
Innovation Solution
A MEMS device with a reflective layer having a curved or stepped shape is designed, varying the distance between the reflective layer and the absorption plate to optimize infrared absorption across a wider wavelength range, enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed distance between the absorption plate and reflector is used, then the device structure is simple, but the infrared absorption is limited to a specific wavelength with reduced sensitivity
Solution Approach 1:
The reflective layer is designed with a curved surface instead of a flat surface, creating varying distances between the absorption plate and different regions of the reflective layer. This curvature enables the device to absorb infrared rays across a broader wavelength range by satisfying the quarter-wavelength condition for multiple wavelengths simultaneously, thereby resolving the contradiction between absorption efficiency and structural simplicity.
Solution Approach 2:
Different regions of the reflective layer are designed with different local properties - specifically, varying distances from the absorption plate. The curved reflective layer creates zones with different path lengths for infrared reflection, allowing each region to optimize absorption for specific wavelength ranges while collectively achieving broad-spectrum absorption.
2Adaptability or versatility
If the distance between the absorption plate and reflector is increased, then the absorption bandwidth is widened, but the device volume increases
Solution Approach 1:
The curved reflective layer allows the cavity to maintain a compact volume while creating varying reflection path lengths. By curving the reflective surface, the design achieves broad wavelength coverage without proportionally increasing the overall cavity volume, as the curvature efficiently utilizes the available space to create multiple optical path lengths within a confined region.
Solution Approach 2:
Instead of increasing the distance uniformly in one dimension, the invention introduces variation in the vertical dimension through curvature. This allows the device to achieve broadband absorption by utilizing the third dimension (height/depth) more effectively, creating varying path lengths without proportionally increasing the overall device footprint or volume.
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 MEMS device achieves increased absorption efficiency and improved sensitivity by adjusting the distance between the reflective layer and absorption plate, allowing for higher infrared absorption across a broader wavelength band.
Implementation Method 1
a reflective layer formed on the upper surface of the lower substrate and reflecting an infrared band
Implementation Method 2
an absorption plate formed to be spaced apart from an upper portion of the reflective layer and absorbing infrared rays to change resistance
Implementation Method 3
A bolometer is a type of infrared sensor. The bolometer absorbs incident infrared rays. When a temperature of an absorption plate of the bolometer is increased, a change in resistance of a resistive layer caused by the increase in temperature is detected and energy of infrared rays is measured from the change in resistance.
Data Source
AI summary
A MEMS device according to an example embodiment of the present disclosure includes: a lower substrate; an infrared sensor formed on the lower substrate; and a lower bonding pad disposed to cover the infrared sensor. The infrared sensor includes: a metal pad formed on an upper surface of the lower substrate and electrically connected to a detection circuit; a reflective layer formed on the upper surface of the lower substrate and reflecting an infrared band; an absorption plate disposed to be spaced apart from an upper portion of the reflective layer and absorbing infrared rays to change resistance; and an anchor formed on the metal pad to support the absorption plate and to electrically connect the metal pad and the absorption plate to each other. The reflective layer has a curved or stepped shape such that a distance between the reflective layer and the absorption plate varies depending on a position of the reflective layer.