CMOS MEMS Oscillator Integration via Polysilicon Beam
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Solution Overview
Problem
Current semiconductor chip manufacturing processes based on CMOS technology face challenges in integrating crystal oscillators due to their discrete nature and incompatibility with MEMS technology, limiting the reduction of oscillator size and integration within the chip.
Innovation Solution
A MEMS oscillator manufacturing method that forms an oscillating beam on a substrate using CMOS-compatible materials and processes, including an interlayer dielectric layer, anode and cathode plugs, sacrifice layers, and an isolating layer, allowing for the creation of a compact oscillator structure that can be easily integrated into a semiconductor chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If crystal oscillators are encapsulated as discrete devices and arranged outside semiconductor chip, then the oscillation accuracy is maintained, but the size of integrated circuit cannot be reduced
Solution Approach 1:
The patent merges the crystal oscillator with the semiconductor chip by fabricating both using CMOS process. The oscillator is integrated within the chip structure, combining previously separate discrete devices into a unified integrated system, thereby reducing overall circuit size while maintaining functionality
Solution Approach 2:
The patent replaces traditional mechanical quartz crystal oscillators with a MEMS-based electromagnetic oscillation system. The oscillating beam is driven by electromagnetic forces from drive plates, substituting the mechanical resonance of quartz crystals with an electromagnetic-mechanical coupling system that is compatible with CMOS fabrication
2Volume of moving object
If MEMS technology is used to fabricate crystal oscillators, then the oscillator size is reduced, but compatibility with CMOS manufacturing process is lost
Solution Approach 1:
The patent creates a universal fabrication approach where the oscillator structure uses standard CMOS-compatible materials and processes. The oscillating beam can be made from polysilicon or other CMOS-compatible materials, allowing the same fabrication line to produce both logic circuits and oscillators, achieving multi-functionality of the manufacturing process
Solution Approach 2:
The patent changes the material parameters and structural parameters to achieve CMOS compatibility. Instead of using quartz crystals with specific mechanical properties, the oscillating beam uses polysilicon with appropriate thickness and doping parameters that can be controlled through standard CMOS fabrication parameters, enabling integration with existing CMOS processes
3Measurement precision
If traditional crystal oscillator structure is used, then oscillation accuracy is achieved, but fabrication complexity increases when integrating with semiconductor chip
Solution Approach 1:
The patent segments the oscillator into distinct functional layers: oscillating beam layer, drive plate layer, electrode layer, and encapsulation layer. Each layer is fabricated using standard CMOS process steps, allowing complex functionality to be achieved through simple, repeatable fabrication stages rather than complex monolithic structures
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 method enables the reduction of oscillator size, simplifies fabrication, and allows for seamless integration within a semiconductor chip, addressing the need for smaller, more densely packed circuit elements.
Implementation Method 1
The oscillating beam is driven by a drive plate and outputs oscillation signals through the anode and the cathode
Implementation Method 2
subject to the electric field, the oscillating crystal 1 generates regular oscillations
Data Source
AI summary
A crystal oscillator and manufacturing method thereof are provided. The crystal oscillator includes: a semiconductor substrate; an interlayer dielectric layer located on the surface of the semiconductor substrate, an excitation plate and a positive electrode plug and a negative electrode plug being formed inside the interlayer dielectric layer, and the positive electrode plug and the negative electrode plug being located at the both sides of the excitation plate; a bottom cavity on top of the excitation plate, located between the positive electrode plug and the negative electrode plug; a vibrating crystal located on the surface of the interlayer dielectric layer, across the bottom cavity and connected with the positive electrode plug and the negative plug, wherein the vibrating crystal connects the positive electrode plug and the negative electrode plug at its both sides and besides the other both sides are the free ends and do not contact with the surrounding objects; an isolating layer located on top of the interlayer dielectric layer, a gap between the isolating layer and the vibrating crystal thus forming a top cavity; a covering layer formed on the surface of the isolating layer. The crystal oscillator is manufactured based on Complementary Metal-Oxide-Semiconductor Transistor (CMOS) technology, and can be integrated into the semiconductor chip easily and can meet the requirement for the miniature components.