Electrostatic Substrate Holder with Integrated Heating Resistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrostatic substrate holders used in ion implantation processes face challenges in heating substrates to high temperatures while maintaining high voltage bias, as conventional heating methods are inefficient and can introduce contaminants, and existing solutions either fail to achieve high temperatures or risk damaging mechanical components.
Innovation Solution
An electrostatic substrate holder design featuring a conductive clamping flange, heat shields, and a temperature control system with a heating resistor, allowing for independent heating and high voltage biasing, along with a cooling network and gas conduit for efficient heat transfer, prevents contamination and mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If infrared lamps are used to heat the substrate, then heating is achieved, but parasitic deposits are created on the lamps which masks radiation and disturbs heating
Solution Approach 1:
The patent introduces a susceptor as an intermediary element between the infrared heating source and the substrate. The susceptor absorbs infrared radiation and transfers heat to the substrate through thermal conduction, preventing direct contact between infrared lamps and substrate that would cause parasitic deposits. This mediator approach allows heating to proceed without the harmful deposition issue.
Solution Approach 2:
The patent replaces direct infrared heating of the substrate with a thermal conduction-based heating system using a susceptor. Instead of relying on radiant heat transfer that causes deposits, the system uses a solid medium (susceptor) to transfer thermal energy, substituting the heating mechanism to eliminate the harmful effect.
2Temperature
If warm wall enclosures are used for heating, then substrate heating is achieved, but heat exchange is poor at low pressure and considerable radiation losses occur
Solution Approach 1:
The susceptor acts as a thermal mediator that efficiently couples the heating source to the substrate. By placing the susceptor in direct thermal contact with the substrate and positioning it within the infrared radiation field, the system creates an efficient heat transfer pathway that minimizes radiation losses to the enclosure walls.
Solution Approach 2:
The patent employs pulsed high voltage biasing during ion implantation, which creates periodic heating cycles. The substrate is heated during plasma discharge phases and cooled during idle phases, allowing temperature control without continuous high power input, thereby reducing overall energy losses.
3Temperature
If alternating positive voltage is applied to heat the substrate through electron attraction, then heating is achieved, but energetic electrons create defects reducing carrier lifetime
Solution Approach 1:
The susceptor serves as a thermal intermediary that decouples the heating function from the ion implantation function. Heating is achieved through infrared radiation absorbed by the susceptor and transferred to the substrate, while ion implantation occurs through controlled negative voltage pulses. This separation prevents electron-induced defects while maintaining heating capability.
Solution Approach 2:
The patent replaces electron-based heating (which causes defects) with infrared radiation-based heating through a susceptor. This substitution changes the heating mechanism from one that generates harmful electrons to one that uses thermal radiation and conduction, eliminating the defect creation problem.
4Loss of energy
If brazing is used to connect heating module to substrate holder, then thermal transport is optimized, but metal contaminants are introduced
Solution Approach 1:
The patent extracts the heating function from the substrate holder structure by using a separate, removable susceptor element. This separation eliminates the need for permanent brazed connections between heating elements and the substrate holder, thereby removing the source of metal contaminants while maintaining thermal transport efficiency through the susceptor-substrate interface.
Solution Approach 2:
The susceptor is designed as a disposable or easily replaceable component that can be discarded after use. This approach eliminates the need for permanent, contaminating connections - the susceptor is simply placed in position, used for heating, and then removed or replaced, avoiding any brazing or permanent attachment that would introduce metal contaminants.
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 efficient heating of substrates to high temperatures while maintaining high voltage bias, reducing the risk of contamination and mechanical stress, and improving the precision of ion implantation processes.
Implementation Method 1
document US Pat. No. 6,538,872 teaches an electrostatic substrate holder provided with a resistive heating means
Implementation Method 2
a cooling network and gas conduit for efficient heat transfer
Implementation Method 3
gas conduit for efficient heat transfer
Implementation Method 4
heat shields, and a temperature control system
Data Source
Figure 1
AI summary
The present invention relates to a bracket comprising an electrically conductive polarised table (10) which is connected to a high-voltage power supply (12) supported by an electrically insulating base (40), an electrically insulating substrate holder (20) which is cylindrical, the upper face thereof having a support plane for receiving a substrate (50), feet (15) which rest on the polarised table (10) in order to support the lower face of the substrate holder (20), at least one electrically conductive connection (201, 202, 203, 31, 30) for connecting the support plane to the polarised table (10). The bracket is characterized in that the substrate holder (20) incorporates a heating resistor (26).