Semiconductor Storage Device Impurity Diffusion via Isolation Film
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Solution Overview
Problem
The shrinking of semiconductor storage devices, such as NAND-type flash memory, poses challenges in ion implantation due to smaller channel widths of selection gate transistors, leading to difficulty in ion implantation and increased variation in implanted ions across memory cells, affecting device reliability and functionality.
Innovation Solution
A semiconductor storage device and manufacturing method involving the formation of a trench in a semiconductor layer with a device isolation/insulation film, where p-type impurities are implanted into the film and diffused towards device formation regions, resulting in a higher impurity concentration in the film compared to the regions, improving ion implantation precision and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If device size is shrunk to increase storage capacity, then storage density is improved, but ion implantation precision deteriorates due to smaller channel width
Solution Approach 1:
The device isolation film serves as an intermediary medium to deliver impurities to the channel region. Instead of directly implanting impurities into the small channel width, the patent uses the isolation film as a reservoir that releases impurities through thermal diffusion, thereby achieving precise impurity distribution even in miniaturized devices with reduced channel dimensions
Solution Approach 2:
The patent performs preliminary impurity implantation into the device isolation film before the final device formation. This preliminary action allows the impurities to be pre-positioned in the isolation film, which then serves as a controlled source for subsequent thermal diffusion into the channel region, ensuring precise impurity distribution in miniaturized devices
2Area of moving object
If channel width is reduced to shrink device size, then device density is improved, but ion implantation uniformity deteriorates
Solution Approach 1:
The device isolation film acts as an intermediary that ensures uniform impurity distribution across the channel width. By implanting impurities into the isolation film first and then using thermal diffusion, the system achieves uniform impurity concentration in the channel region, even when the channel width is reduced to increase device density
Solution Approach 2:
The patent changes the physical state and concentration parameters of impurities through controlled thermal diffusion. By adjusting temperature and time parameters during the thermal process, the impurities diffuse from the isolation film into the channel region with uniform distribution, maintaining manufacturing precision despite reduced device dimensions
3Manufacturing precision
If impurity concentration is increased in device isolation film, then impurity distribution uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the device isolation function with the impurity source function into a single structure. The device isolation film not only provides electrical isolation between devices but also serves as the impurity reservoir for channel doping. This merging reduces manufacturing complexity by eliminating the need for separate isolation and doping processes
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 approach enhances the uniformity of impurity concentration across memory cells, improving the reliability and functionality of semiconductor storage devices by reducing variations in ion implantation and maintaining consistent threshold voltage, thus addressing the challenges of smaller device sizes.
Implementation Method 1
implanting an impurity into the device isolation/insulation film
Implementation Method 2
diffusing the impurity from the device isolation/insulation film toward the device formation regions through a thermal process
Data Source
AI summary
A non-volatile semiconductor storage device includes: a semiconductor substrate; a semiconductor layer formed on the semiconductor substrate; a first device isolation/insulation film formed in a trench, the trench formed in the semiconductor layer, with a first direction taken as a longitudinal direction; a device formation region formed by separating the semiconductor layer by the first device isolation/insulation film with the first direction taken as a longitudinal direction; and a memory transistor disposed on the device formation region. The first device isolation/insulation film and the device formation region have an impurity of a first conductivity type. An impurity concentration of the impurity of the first conductivity type in the first device isolation/insulation film is higher than that in the device formation region.