Elevated Substrate Support for Double-Sided PECVD Passivation
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Solution Overview
Problem
Current methods for depositing an electrical passivation layer on silicon wafers for power semiconductors require a two-step process, risking contamination and reduced yield due to manual flipping and inadequate coverage of both bevels in a single-sided deposition.
Innovation Solution
A single-step Plasma Enhanced Chemical Vapor Deposition (PECVD) method using an elevated substrate support in a plasma reactor, allowing both sides of the silicon wafer to be exposed to the plasma, combined with an improved cooling mechanism to maintain optimal substrate temperature and uniform deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a recess substrate holder is used for single-sided deposition, then the substrate can be held securely with good thermal contact, but only one side of the wafer can be coated requiring manual flipping and multiple process steps
Solution Approach 1:
The patent inverts the conventional recess substrate holder design by using a protruding substrate holder. This inversion allows the wafer to be positioned vertically with both bevels exposed to the plasma, enabling double-sided deposition in a single process step without manual flipping, thereby improving productivity while maintaining secure substrate holding and thermal contact.
2Reliability
If manual flipping is required between deposition steps, then single-sided deposition can be completed, but the unprotected bevel is at high risk of contamination reducing blocking yield
Solution Approach 1:
By inverting the substrate holder from recess to protrusion, the patent enables both bevels to be coated simultaneously in one process step. This eliminates the manual flipping operation that exposes the unprotected bevel to contamination, thereby improving reliability and blocking yield while maintaining process efficiency.
3Productivity
If an elevated substrate support is used for double-sided exposure, then both bevels can be coated simultaneously, but thermal contact and heat dissipation must be maintained
Solution Approach 1:
The inverted protruding substrate holder design positions the wafer vertically with both bevels exposed to plasma for simultaneous coating. The protrusion geometry maintains adequate thermal contact between the substrate and holder, enabling effective heat dissipation while achieving the temperature control needed for single-step double-sided deposition.
Solution Approach 2:
The patent modifies the substrate holder geometry from a recess to a protrusion, changing the physical parameters of the holding structure. This parameter change enables vertical wafer positioning that exposes both bevels to plasma while maintaining sufficient thermal contact area for heat dissipation during the deposition process.
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
Enables simultaneous double-sided deposition of a homogeneous amorphous hydrogenated carbon layer on silicon wafers in a single process step, reducing contamination risks and ensuring uniform electrical properties while maintaining effective heat dissipation.
Implementation Method 1
One of the currently used state of the art passivation materials is amorphous hydrogenated carbon (a-C:H, also known as Diamond-like carbon DLC) which is typically deposited in a Plasma Enhanced Chemical Vapor Deposition (PECVD) process
Implementation Method 2
The hydrocarbon precursor gas (e.g., methane, acetylene) enters the reaction chamber of the plasma reactor through openings in the first, upper electrode, is ionized by radiofrequency, and forms the bulk plasma
Implementation Method 3
The edge plasma layer is the space where the plasma ions get accelerated into the direction of the substrate and substrate carrier plate due to a DC bias voltage applied between the two electrodes
Implementation Method 4
The substrate carrier plate does not only act as a holder for the silicon wafers (substrate), it also establishes the disc's thermal and electrical contacts to the actively cooled second (lower) electrode in the reaction chamber
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A substrate (4) is mounted onto an elevated substrate support (31) of a substrate carrier plate (3). The substrate carrier plate with the substrate is then placed in a plasma reactor (8). Due to the elevated substrate support, both opposite sides of the substrate are exposed to the plasma (6) and are therefore coated with an electrical passivation layer (7).