Integrated CMOS Sensor with Low-K Dielectric for Parasitic Reduction
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Solution Overview
Problem
The integration of microcontroller, A-to-D converter, EEPROM memory, RF transceiver, and sensor elements in a single CMOS chip is hindered by material processing incompatibilities and substrate parasitics, leading to difficulties in high-volume semiconductor production, especially for sensor applications requiring non-standard materials like platinum or gold coating.
Innovation Solution
An integrated sensor device using a Low-K dielectric with an organic polymer, such as polyimide, for the sensor dielectric, allowing for low-temperature deposition and integration with MOS interconnect levels, along with a hydrophobic nature for fast moisture egress, and a 18-bit A-to-D converter for high-resolution humidity sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensor elements are manufactured on ceramic or glass substrates, then sensor performance is improved, but integration with silicon CMOS circuits becomes difficult
Solution Approach 1:
The patent combines sensor elements, CMOS circuits, and RF transceivers onto a single silicon substrate. The sensor electrodes are formed using standard CMOS metallization layers, eliminating the need for separate ceramic or glass substrates and enabling full integration while maintaining sensor performance.
Solution Approach 2:
The silicon substrate serves multiple functions: it acts as the base for CMOS circuit fabrication, provides the platform for sensor element formation, and enables RF transceiver integration. This multi-functional approach replaces the traditional separate substrate requirements for each component type.
2Device complexity
If RF transceivers, EEPROM memories, and mixed-signal converter circuits are integrated on a single CMOS chip, then device integration is improved, but substrate parasitics and process incompatibilities increase
Solution Approach 1:
The patent employs different dielectric materials in different regions of the chip. Low-K dielectric materials are used in specific areas to reduce parasitic capacitance for RF circuits, while standard dielectrics are used elsewhere. This localized approach optimizes performance for each circuit type without compromising overall integration.
Solution Approach 2:
The patent uses composite dielectric structures combining multiple materials with different properties. Low-K dielectric materials are combined with standard CMOS dielectrics to achieve both high integration density and reduced parasitic effects, allowing RF transceivers and memory circuits to coexist on the same chip.
3Ease of manufacture
If aluminium metallisation is used in IC processing, then manufacturing simplicity is improved, but corrosion resistance deteriorates
Solution Approach 1:
The patent uses composite metallization structures where aluminium is combined with protective barrier layers. This composite approach maintains the manufacturing simplicity of aluminium deposition while adding corrosion protection through the barrier layers, solving both the ease of manufacture and reliability requirements.
4Productivity
If high-volume semiconductor processing is used, then productivity is improved, but specialization facilities and post-processing operations increase cost
Solution Approach 1:
The patent designs the sensor structure to be compatible with standard CMOS fabrication processes. The sensor electrodes are formed using the same metallization layers and processing steps as the CMOS circuits, allowing both components to be manufactured in the same high-volume facility without requiring specialized post-processing operations.
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
Enables the production of a fully integrated sensor chip with reduced parasitic capacitance, lower power consumption, and high-resolution humidity sensing, suitable for wireless sensor applications with improved manufacturability and reliability.
Implementation Method 1
In one embodiment, the insulating dielectric material is hydrophobic. This allows fast egress of the small quantity of gas or humidity which ingresses
Implementation Method 2
It has been found that such a dielectric allows sufficient ingress of gas or moisture and a good response characteristic
Data Source
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AI summary
A single chip wireless sensor (1) comprises a microcontroller (2) connected to a transmit/receive interface (3), which is coupled to a wireless antenna (4) by an L-C matching circuit. The sensor (1) senses gas or humidity and temperature. The device (1) is an integrated chip manufactured in a single process in which both the electronics and sensor components are manufactured using standard CMOS processing techniques, applied to achieve both electronic and sensing components in an integrated process. A Low-K material (57) with an organic polymer component is spun onto the wafer to form a top layer incorporating also sensing electrodes (60). This material is cured at 300°C, which is much lower than CVD temperatures. The polyimide when cured becomes thermoset, and the lower mass- to-volume ratio resulting in K, its dielectric constant, reducing to 2.9. The thermoset dielectric, while not regarded as porous in the conventional sense, has sufficient free space volume to admit enough gas or humidity for sensing.