Oxide Semiconductor Memory Device UV Light Writing
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Solution Overview
Problem
Current methods for manufacturing semiconductor memory devices, such as mask ROM and organic memory, are complex and costly, with high equipment expenses and long processing times, and they face challenges in erasing information from IC chips after use.
Innovation Solution
A semiconductor memory device using a thin film transistor with an oxide semiconductor, featuring a specific structure with a back gate electrode layer and ultraviolet light writing capability, allowing for efficient data writing and erasure without the need for expensive equipment or complex processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mask ROM method is used to form memory device, then identification number can be written during manufacturing, but manufacturing steps become complex and cost increases
Solution Approach 1:
The patent replaces complex mechanical photolithography systems with a simple UV light irradiation system. Instead of using electron beam exposure apparatuses and complex photomask systems, the invention uses UV light to directly modify the oxide semiconductor layer, achieving data writing through a much simpler optical process that eliminates multiple manufacturing steps.
Solution Approach 2:
The patent changes the physical state of the oxide semiconductor layer by irradiating it with UV light, which modifies the electrical characteristics of the material. This parameter change approach allows data to be written by altering the resistance state of the oxide semiconductor, replacing the need for complex physical patterning processes.
2Adaptability or versatility
If electron beam exposure apparatus is used to print different identification numbers, then custom data can be written, but processing time increases and throughput decreases
Solution Approach 1:
The patent replaces the slow mechanical electron beam scanning system with a fast UV light irradiation system. The UV light can be applied simultaneously across the entire substrate or selective regions, eliminating the sequential scanning process and dramatically increasing throughput while maintaining the ability to write custom identification data.
Solution Approach 2:
The patent prepares the oxide semiconductor layer in advance during the standard thin film transistor manufacturing process, so that the material is already in the correct state to receive UV light writing. This preliminary preparation eliminates the need for separate complex exposure steps and allows direct UV writing of custom data.
3Adaptability or versatility
If photomask is moved and light exposure is repeated for each IC chip pattern, then different identification numbers can be formed, but manufacturing time becomes extremely long
Solution Approach 1:
The patent replaces the mechanical photomask movement and repeated exposure process with a single UV light irradiation step. By using UV light's ability to modify the oxide semiconductor material directly, the system eliminates the need for physical mask repositioning and sequential processing, achieving individual chip customization in a single fast operation.
4Ease of manufacture
If organic memory is used with electrical field application, then information can be written after manufacturing, but special probe equipment is required and erasure is difficult
Solution Approach 1:
The patent replaces the need for special probe equipment with simple UV light irradiation. Instead of requiring complex electrical field application apparatuses and contact probes, the invention uses non-contact UV light to write data, significantly simplifying the equipment requirements while enabling post-manufacturing data writing.
Solution Approach 2:
The patent uses UV light irradiation to change the physical and electrical parameters of the oxide semiconductor layer, creating stable threshold shifts that represent data. This parameter change mechanism is achieved through simple light exposure rather than complex electrical field application, making the process easier to implement.
5Reliability
If thin film transistor with oxide semiconductor is irradiated with ultraviolet light, then memory characteristic is obtained, but threshold voltage shifts to negative side making normally-on characteristic difficult to control
Solution Approach 1:
The patent carefully controls the UV light irradiation parameters such as wavelength, intensity, and duration to achieve the desired threshold voltage shift for memory operation. By optimizing these parameters, the system achieves reliable memory characteristics while controlling the threshold shift to avoid excessive negative shifts that would create normally-on characteristics.
Solution Approach 2:
The patent applies UV light irradiation in a controlled partial manner, targeting only specific regions or applying limited doses to achieve the minimum necessary threshold shift for memory operation without excessive negative shifts. This partial action approach maintains proper transistor control while achieving memory functionality.
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 solution enables faster, more cost-effective data writing and erasure in semiconductor memory devices, reducing manufacturing complexity and ensuring secure data handling by utilizing simple equipment and stable threshold characteristics.
Implementation Method 1
a characteristic that is obtained when a thin film transistor including an oxide semiconductor is irradiated with ultraviolet light
Data Source
AI summary
To provide a semiconductor memory device including an oxide semiconductor that can deal with instability of a threshold characteristic, in which writing is possible by a simple method. The semiconductor memory device functions by utilizing a characteristic that a threshold shifts when a thin film transistor including an oxide semiconductor is irradiated with ultraviolet light. Readout can be performed by setting a readout voltage between the threshold before the ultraviolet light irradiation and the threshold after irradiation. The threshold characteristic of an initial characteristic can be controlled by providing a back gate or by using two thin film transistors.