Programmable ROM Contact Layer Traces for SoC Fabrication
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Solution Overview
Problem
The existing system on a chip (SoC) fabrication process is inefficient due to the need to halt production and discard partially fabricated devices when firmware changes are required, leading to significant opportunity costs and production downtime.
Innovation Solution
The implementation of programmable ROM circuits with bit-cells that can be programmed using only the contact layer, allowing for quicker design turnaround and reconfiguration without altering the active layer traces, enabling the reuse of partially fabricated SoCs and reducing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If firmware changes are required during SoC fabrication, then the ROM design must be updated, but production must be halted and partially fabricated devices discarded
Solution Approach 1:
The ROM bit-cell structure is segmented into two independent layers: the active layer (containing transistors and word lines) and the contact layer (containing contact points). This segmentation allows the contact layer to be modified independently to program different ROM values without affecting the active layer or requiring complete device re-fabrication.
Solution Approach 2:
The active layer is fabricated first and remains fixed, while the contact layer is deposited later to program the desired ROM values. This preliminary action of creating the active layer structure enables subsequent flexible programming of different firmware versions by simply altering the contact layer pattern.
2Adaptability or versatility
If firmware changes are required during SoC fabrication, then a new ROM design is needed, but significant opportunity costs and production downtime occur
Solution Approach 1:
The active layer is prepared in advance with all necessary transistor structures and word lines, enabling rapid firmware updates by only modifying the contact layer pattern subsequently. This eliminates time-consuming re-fabrication steps.
Solution Approach 2:
The ROM programming is achieved by changing the spatial arrangement parameters of the contact layer (contact point positions and patterns) rather than modifying the active layer structure. This parameter change approach allows quick reconfiguration for different firmware versions.
3Adaptability or versatility
If traditional ROM fabrication is used, then the entire device must be re-fabricated for firmware changes, but this leads to significant waste of materials and discarded devices
Solution Approach 1:
By dividing the ROM into active layer and contact layer components, only the contact layer material needs to be deposited and patterned for firmware changes, while the active layer materials are reused. This significantly reduces material waste compared to complete re-fabrication.
Solution Approach 2:
The active layer structure is preserved and recovered for reuse across multiple firmware versions, while only the contact layer is discarded and re-deposited with new patterns. This selective recovery approach minimizes material waste.
Data Source
AI summary
A device includes a programmable ROM circuit, an address circuit, and a processor. The programmable ROM circuit includes multiple physically contiguous pairs of bit-cells, each pair of bit-cells includes an active layer trace extending continuously across both of the bit-cells, each pair of bit-cells comprises a shared contact layer point when the pair of bit-cells is programmed to a value of one and no shared contact layer point when the pair of bit-cells is programmed to a value of zero. The address circuit is coupled to the programmable ROM circuit and configured to address only a first bit-cell of each pair of bit-cells. The processor is coupled to the address circuit and the programmable ROM circuit and configured to use the address circuit to read data from one or more pairs of bit-cells of the programmable ROM circuit.