Triple-Layered Bit Line Spacers for DRAM Parasitic Capacitance
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Solution Overview
Problem
In highly integrated semiconductor devices, such as DRAM, misalignment during photolithography can lead to exposure and over-etching of nitride/oxide/nitride (NON) spacers, increasing the probability of electrical shorts between storage node contact plugs and bit lines due to differential etch rates, which reduces sensing margins and device performance.
Innovation Solution
The implementation of triple-layered bit line spacers with a nitride layer as the first and third spacers and an oxide layer with a lower dielectric constant as the second spacer, where the oxide layer is formed using radical or wet oxidation processes, helps to reduce parasitic capacitance and prevent electrical shorts by maintaining spacer integrity during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If NON spacers are formed to reduce parasitic capacitance, then bit line capacitance is reduced, but misalignment during photolithography causes exposure and over-etching of the oxide layer, increasing the probability of electrical shorts
Solution Approach 1:
The spacer structure is segmented into three distinct layers (inner nitride layer, oxide layer, outer nitride layer) where each layer serves a specific function. The inner and outer nitride layers protect the oxide layer from over-etching, while the oxide layer provides low dielectric constant to reduce parasitic capacitance. This segmentation resolves the contradiction by protecting the capacitance-reducing oxide layer from the harmful effects of misalignment and over-etching.
Solution Approach 2:
The NON spacer combines three different materials (nitride and oxide) with complementary properties. The nitride layers provide etch resistance and structural integrity, while the oxide layer provides low dielectric constant. This composite structure allows the spacer to simultaneously reduce parasitic capacitance and prevent electrical shorts despite photolithography misalignment.
2Loss of energy
If the oxide layer is made thinner to reduce parasitic capacitance further, then bit line capacitance is reduced, but the oxide layer becomes more susceptible to complete removal during etching, increasing electrical short risk
Solution Approach 1:
The inner and outer nitride layers act as protective cushions that prevent complete removal of the oxide layer during etching processes. Even if the oxide layer is made thin to reduce parasitic capacitance, the nitride layers provide a safety margin that prevents electrical shorts by maintaining spacer integrity throughout the manufacturing process.
3Device complexity
If alignment tolerance is increased to simplify photolithography, then manufacturing complexity is reduced, but misalignment causes exposure of NON spacers and electrical shorts
Solution Approach 1:
The nitride layers are strategically positioned at critical locations (inner and outer surfaces of the oxide layer) where protection is most needed. This local quality approach ensures that the most vulnerable parts of the spacer structure receive enhanced protection, allowing the device to tolerate larger alignment variations without electrical shorts.
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 configuration effectively reduces parasitic capacitance and minimizes the risk of electrical shorts, enhancing the operational performance and reliability of semiconductor devices by maintaining spacer integrity and reducing the impact of misalignment during the photolithography process.
Implementation Method 1
oxidizing the nitride layer to form an oxide layer having a lower dielectric constant than the nitride layer
Data Source
AI summary
Semiconductor devices are provided that include spacers on sidewalls of conductive lines, as well as methods for manufacturing the same. A method for manufacturing a semiconductor device includes forming bit lines on a semiconductor substrate. Triple-layered bit line spacers are formed on respective sidewalls of the bit lines. An interlayer insulation layer is formed on the bit lines and the triple-layered bit line spacers. Storage node contact plugs that penetrate the interlayer insulation layer are formed between the bit lines. Portions of the triple-layered bit line spacers are etched to form recessed regions. An insulation layer is formed on the substrate including the recessed regions. Storage node electrodes electrically connected to the storage node contact plugs are formed.