MEMS Electrode Deposition via BEOL Passivation
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Solution Overview
Problem
MEMS devices face accuracy issues due to out-gassing from ILD layers and difficulty in controlling etch processes, which affect the predetermined pressure within the cavity and the distance between the soft mechanical structure and sensing electrodes.
Innovation Solution
A method of forming electrodes over a BEOL stack using a deposition process, avoiding etching of the BEOL stack, and depositing a passivation layer to reduce out-gassing and improve control over electrode positions and dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching process is used to form electrodes, then electrode positioning is achieved, but manufacturing precision deteriorates due to difficulty in controlling etch processes
Solution Approach 1:
Instead of using etching to remove material to form electrodes, the patent uses deposition to add material and form electrodes. This inverts the conventional approach from subtractive manufacturing to additive manufacturing, achieving precise electrode positioning through controlled deposition processes rather than difficult-to-control etching processes.
Solution Approach 2:
The patent replaces the etching process (chemical removal mechanism) with a deposition process (physical or chemical addition mechanism). This substitution changes the fundamental mechanism from material removal to material addition, enabling better control over electrode position and dimensions through deposition parameters.
2Measurement precision
If ILD layers are present in the cavity, then structural support is provided, but out-gassing occurs affecting pressure accuracy
Solution Approach 1:
The patent removes the ILD layers from the cavity structure, extracting the source of out-gassing. By eliminating the ILD layers that were previously used for structural support, the patent prevents out-gassing into the cavity and maintains accurate pressure measurements, accepting the trade-off of needing alternative structural support.
Solution Approach 2:
The patent converts the harmful out-gassing effect into a benefit by using the deposition process to form electrodes directly without requiring ILD layers. The same deposition technology that forms the electrodes also creates a structure that prevents out-gassing, turning the potential harm into a beneficial outcome.
3Measurement precision
If sensing gap is reduced to increase sensitivity, then measurement sensitivity improves, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent replaces etching-based gap formation with deposition-based gap formation. The deposition process allows for more precise control over the sensing gap dimensions through control of deposition thickness, enabling reduced gap sizes for higher sensitivity while maintaining manufacturing precision through deposition parameter control.
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 approach mitigates out-gassing, enhances the accuracy of pressure control within the cavity, and increases the sensitivity of MEMS devices by reducing the sensing gap, leading to more precise measurements.
Implementation Method 1
out-gassing from ILD layers
Implementation Method 2
A method of forming electrodes over a BEOL stack using a deposition process
Data Source
AI summary
The present disclosure relates to a method of forming an integrated chip structure. The method includes forming a plurality of interconnect layers within a dielectric structure over a substrate. A dielectric layer arranged along a top of the dielectric structure is patterned to define a via hole exposing an uppermost one of the plurality of interconnect layers. An extension via is formed within the via hole and one or more conductive materials are formed over the dielectric layer and the extension via. The one or more conductive materials are patterned to define a sensing electrode over and electrically coupled to the extension via. A microelectromechanical systems (MEMS) substrate is bonded to the substrate. The MEMs substrate is vertically separated from the sensing electrode.