Polysilicon Conductive Layer With Electric-Field Relaxing Layers
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Solution Overview
Problem
Semiconductor integrated circuits using polycrystalline silicon layers are prone to electrical breakdown due to voltage distribution issues, particularly at the ends of the polysilicon film, leading to increased manufacturing costs when thicker insulating films are used to prevent breakdown.
Innovation Solution
A semiconductor integrated circuit design featuring a conductive layer with a polycrystalline p-type layer and electric-field relaxing layers with lower specific resistivity on both sides, connected to high- and low-potential electrodes, which helps to relax electrical field crowding and prevent breakdown by distributing voltage more evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the insulating film is increased to prevent electrical breakdown, then the reliability of the insulating film is improved, but the manufacturing cost increases
Solution Approach 1:
The patent applies local quality by creating electric-field relaxing layers with different impurity concentrations at specific locations (end portions) of the polysilicon film. These layers have higher impurity concentrations than the central region, forming localized regions with different electrical properties. This allows the insulating film thickness to be reduced overall while maintaining reliability at critical breakdown-prone locations through localized field relaxation.
Solution Approach 2:
The patent changes the impurity concentration parameter of the polysilicon film by forming regions with different impurity levels. The electric-field relaxing layers have higher impurity concentrations than the central region, which changes the electrical conductivity and electric field distribution. This parameter change enables the system to prevent breakdown with thinner insulating films by controlling the electrical properties at critical locations.
2Ease of manufacture
If the insulating film thickness is reduced to lower manufacturing cost, then the manufacturing cost decreases, but electrical breakdown occurs more easily
Solution Approach 1:
By concentrating the electric field relaxation function in localized regions at the end portions of the polysilicon film, the patent enables use of thinner insulating films in non-critical areas while maintaining reliability at critical breakdown locations. The electric-field relaxing layers are positioned only at end portions where breakdown is most likely to occur, allowing cost reduction through overall thickness reduction without sacrificing reliability.
Solution Approach 2:
The electric-field relaxing layers act as intermediary structures between the polysilicon film and the insulating film. These intermediate layers with specific impurity concentrations modify the electric field distribution, preventing direct breakdown through the insulating film by redistributing the electrical stress. This intermediary structure enables thinner insulating films to function reliably.
3Reliability
If electric-field relaxing layers with lower specific resistivity are added on both sides of the conductive layer, then the electrical field crowding is relaxed and breakdown is prevented, but the device complexity increases
Solution Approach 1:
The patent segments the polysilicon film into regions with different impurity concentrations: a central region with lower impurity concentration and end portions with higher impurity concentrations forming electric-field relaxing layers. This segmentation allows the structure to perform multiple functions - the central region provides the primary conductive path while the segmented end portions provide field relaxation. The segmentation is achieved through selective ion implantation processes that treat different regions differently.
Solution Approach 2:
The patent addresses the breakdown problem by transitioning from a one-dimensional thickness solution to a two-dimensional solution involving lateral positioning and impurity concentration gradients. Instead of uniformly increasing insulating film thickness throughout, the electric-field relaxing layers are positioned laterally at specific locations (end portions) and extend vertically. This dimensional approach allows localized field control without uniformly increasing overall device complexity.
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
The design effectively prevents electrical breakdown of the insulating film between the semiconductor monocrystalline region and the polycrystalline layer, reducing manufacturing costs and improving the reliability of semiconductor elements.
Implementation Method 1
electric-field relaxing layers having a lower specific resistivity than the conductive layer and each including a polycrystalline layer of n-type so as to be arranged on both sides of the conductive layer in a direction perpendicular to a current-flowing direction
Implementation Method 2
When a current flows through the polysilicon film, a voltage distribution is substantially uniform in the width direction of the polysilicon film perpendicular to the current-flowing direction
Data Source
AI summary
A semiconductor integrated circuit includes: a semiconductor monocrystalline region; an insulating film provided on a main surface of the semiconductor monocrystalline region; a conductive layer having a rectangular shape provided on the insulating film and including at least a polycrystalline layer of p-type; electric-field relaxing layers having a lower specific resistivity than the conductive layer and each including a polycrystalline layer of n-type so as to be arranged on both sides of the conductive layer in a direction perpendicular to a current-flowing direction; a high-potential-side electrode in ohmic contact with the conductive layer at one end of the conductive layer in the current-flowing direction; and a low-potential-side electrode in ohmic contact with the conductive layer and the respective electric-field relaxing layers at another end of the conductive layer opposed to the one end in the current-flowing direction, and having a lower potential than the high-potential-side electrode.