Semi-floating Gate Device Manufacturing Method for U-shaped Channel Yield
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Solution Overview
Problem
The existing methods for manufacturing semi-floating gate devices with U-shaped channels are complex and difficult to control, leading to challenges in ensuring the quality and yield of the semiconductor memory products.
Innovation Solution
A method involving the formation of a U-shaped groove, followed by the deposition and etching of polycrystalline silicon layers to create a floating gate and control gate, simplifies the process by reducing the number of steps required for forming the floating gate opening region, allowing for self-alignment and improved controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a floating gate opening region is formed in the first layer of insulating film on the side wall of the U-shaped groove close to the drain region, then the floating gate can be connected to the drain region, but the process becomes complex and difficult to control
Solution Approach 1:
The patent applies preliminary action by forming the floating gate before creating the opening in the gate insulating film. The floating gate is deposited to fill the U-shaped groove, then the gate insulating film is opened to expose and connect to the floating gate. This reverses the conventional sequence, simplifying the process by eliminating the need to form openings in the insulating film on the groove sidewalls.
Solution Approach 2:
The patent inverts the conventional manufacturing sequence by depositing the floating gate material first to fill the U-shaped groove, then opening the gate insulating film to expose the floating gate for connection to the drain region. This inversion transforms a complex multi-step process into a simpler sequence, improving controllability and product quality.
2Ease of manufacture
If multiple process steps are used to form the floating gate opening region, then the floating gate connection can be achieved, but manufacturing difficulty increases
Solution Approach 1:
The floating gate is formed in advance by depositing polycrystalline silicon to fill the U-shaped groove before any opening operations. This preliminary formation ensures precise positioning and simplifies subsequent steps, as the opening process only needs to expose the pre-formed floating gate rather than create it through complex patterning.
Solution Approach 2:
The floating gate structure serves its own positioning function by naturally filling the U-shaped groove during deposition. This self-alignment eliminates the need for additional alignment steps and complex photolithography patterning to define the floating gate position, reducing manufacturing difficulty while maintaining precision.
3Productivity
If the existing complex process is used, then the floating gate structure can be formed, but the yield of semi-floating gate devices decreases
Solution Approach 1:
By forming the floating gate before opening the gate insulating film, the patent eliminates multiple sequential steps and potential failure points. This preliminary formation approach ensures that the floating gate is already in place and properly positioned before any opening operations, reducing variability and improving device yield.
Solution Approach 2:
The patent merges the floating gate formation and positioning steps into a single deposition process where polycrystalline silicon fills the U-shaped groove. This consolidation of operations reduces the total number of process steps and minimizes alignment errors, directly improving manufacturing yield.
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 optimizes the manufacturing process, reduces complexity and costs, and enhances the yield of semi-floating gate devices with U-shaped channels by simplifying the formation of the floating gate and improving the reliability of the device fabrication.
Implementation Method 1
growing a third layer of insulating film on a surface of the U-shaped groove in Step 1
Implementation Method 2
depositing a first layer of polycrystalline silicon to cover the U-shaped groove, until the first layer of polycrystalline silicon fills up the U-shaped groove
Implementation Method 3
etching back the first layer of polycrystalline silicon, where a top of the remaining first layer of polycrystalline silicon after the etching is located between an upper surface of the second layer of insulating film and the bottom of the doped well
Implementation Method 4
etching away the second layer of insulating film, the first layer of insulating film, and the exposed third layer of insulating film
Data Source
AI summary
A manufacturing method for a semi-floating gate device, mainly comprising a manufacturing method for a floating gate and a floating gate opening area, and the specific process thereof is: reserving a hard mask layer after a U-shaped groove is formed, growing a gate dielectric layer on a surface of the formed U-shaped groove, depositing and etching back a first layer of polysilicon to protect the gate dielectric layer, etching away the exposed gate dielectric layer and hard mask layer, then covering a formed structure to deposit a second layer of polysilicon, then etching a formed polysilicon layer by a photoetching process and an etching process so as to form a floating gate, and forming a floating gate opening area in a self-aligning way. The manufacturing method can simplify the existing manufacturing process for a semi-floating gate device, reduce the difficulty in manufacturing the semi-floating gate device with a U-shaped channel, and improve the yield of the semi-floating-gate device.