3D Memory and Driver Circuit Integration via Substrate Thinning
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Solution Overview
Problem
The integration of a three-dimensional memory device and a driver circuit on opposite sides of a single semiconductor substrate poses a challenge as high-temperature processing steps for the memory device can degrade the performance of the driver circuit devices, such as CMOS devices, by dopant out-diffusion and hydrogen diffusion, reducing input/output speed.
Innovation Solution
A method is developed to form the three-dimensional memory device on the front side of the substrate and the driver circuit on the backside, with the driver circuit devices being formed at a relatively low temperature after the memory device, thereby improving their performance and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If driver circuit devices are formed before the memory device, then the driver circuit can be integrated, but high-temperature processing degrades the driver circuit devices
Solution Approach 1:
The conventional sequence is inverted: instead of forming driver circuit devices first and then the memory device, the memory device is formed first on the front surface, the substrate is thinned and flipped, and then the driver circuit devices are formed on the back surface. This inversion ensures that the driver circuit devices are never exposed to high-temperature processing, as they are formed after the memory device is complete and the substrate has been cooled.
2Device complexity
If driver circuit devices are formed after the memory device on the same surface, then processing is simplified, but high-temperature steps still degrade the driver circuit
Solution Approach 1:
The substrate surface is segmented into a front surface for the memory device and a back surface for the driver circuit devices. This spatial segmentation physically separates the two device types, allowing the driver circuit devices to be formed in a low-temperature process after the memory device is complete, without being exposed to the high-temperature processing required for the memory device.
Solution Approach 2:
The solution uses the third dimension (the back surface of the substrate) to separate the driver circuit devices from the high-temperature processing zone. By thinning the substrate and flipping it, the driver circuit devices can be formed on the opposite surface from the memory device, effectively removing them from the thermal processing path while maintaining integration on a single substrate.
Data Source
AI summary
A method of forming a device structure includes forming a memory-level structure including a three-dimensional memory device over a front side surface of a semiconductor substrate, forming memory-side dielectric material layers over the memory-level structure, bonding a handle substrate to the memory-side dielectric material layers, thinning the semiconductor substrate while the handle substrate is attached to the memory-side dielectric material layers, forming a driver circuit including field effect transistors on a backside semiconductor surface of the semiconductor substrate after thinning the semiconductor substrate, and removing the handle substrate from the memory-side dielectric material layers.