Tunnel Insulating Layer Protection in Semiconductor Memory Fabrication
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Solution Overview
Problem
The conventional method of fabricating semiconductor memory devices often results in damage to the tunnel insulating layer during the etching and cleaning processes, leading to charge loss and degraded data retention characteristics.
Innovation Solution
A method where a conductive layer with a specific thickness is left on the tunnel insulating layer during gate pattern formation, mono-crystallized through ion implantation, and then converted into an insulating layer via oxidation to prevent exposure and damage during etching and cleaning processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the etching process is performed until the tunnel insulating layer is exposed to form gate patterns, then the gate patterns can be formed, but the tunnel insulating layer is damaged by overetching or cleaning process
Solution Approach 1:
A conductive layer is deposited on the tunnel insulating layer before the etching process to serve as a protective mask. This preliminary action prevents the etching process from directly exposing and damaging the tunnel insulating layer, while still allowing gate patterns to be formed through the conductive layer and dielectric layer.
Solution Approach 2:
The conductive layer acts as an intermediary between the etching process and the tunnel insulating layer. It absorbs the harmful etching effects that would otherwise directly damage the tunnel insulating layer, thereby protecting the underlying structure while enabling gate pattern formation.
2Ease of manufacture
If the tunnel insulating layer is exposed during etching and cleaning processes, then gate patterns can be formed, but charge loss occurs and data retention characteristic degrades
Solution Approach 1:
The conductive layer is deposited in advance on the tunnel insulating layer to prevent direct exposure during subsequent processing steps. This preliminary protective measure ensures that the tunnel insulating layer maintains its integrity and prevents charge loss that would otherwise occur during etching and cleaning processes.
Solution Approach 2:
The conductive layer, which would normally be a material to be removed, is instead utilized as a beneficial protective element. Its presence during etching and cleaning processes converts a potential harmful exposure into a protected state, and it is later removed or integrated as part of the gate structure.
3Reliability
If a conductive layer is left on the tunnel insulating layer during gate pattern formation, then etching damage is prevented, but additional processing steps are required
Solution Approach 1:
The conductive layer serves multiple functions: it acts as a protective mask during etching, provides the floating gate structure, and can be mono-crystallized to adjust resistance characteristics. By combining these functions into a single layer, the number of additional processing steps is minimized while achieving both protection and device functionality.
Solution Approach 2:
The resistance of the conductive layer is adjusted by controlling its thickness and performing mono-crystallization through ion implanting. This parameter change allows the same layer to serve both as a protective mask and as a functional floating gate with optimized electrical characteristics, reducing the need for additional protective layers.
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 effectively inhibits etching damage to the tunnel insulating layer, enhancing the electrical characteristics of the semiconductor memory device by maintaining the integrity of the layer and improving data retention.
Implementation Method 1
performing an ion implanting process to mono-crystallize the first conductive layer remaining on the tunnel insulating layer
Implementation Method 2
performing an oxidation process to form an oxide layer on top and side walls of the gate patterns and to convert the mono-crystallized first conductive layer into an insulating layer
Data Source
AI summary
A method of fabricating a semiconductor memory device to protect a tunneling insulating layer from etching-damage includes the steps of forming sequentially a tunnel insulating layer, a first conductive layer, a dielectric layer and a second conductive layer on a semiconductor substrate; etching the second conductive layer, the dielectric layer and the first conductive layer to form gate patterns, the first conductive layer remaining on the tunnel insulating layer between the gate patterns to prevent the tunnel insulating layer from being exposed; performing a cleaning process to remove impurities generated in the etching step; performing an ion implanting process to mono-crystallize the first conductive layer remaining on the tunnel insulating layer; and performing an oxidation process to form an oxide layer on top and side walls of the gate patterns and to convert the mono-crystallized first conductive layer into an insulating layer.