RF Impedance Matching Path for Stable ICP Plasma Ignition
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Solution Overview
Problem
In semiconductor plasma processing, impedance mismatch between the RF power supply and the process chamber leads to inefficient RF energy transmission, resulting in unstable plasma formation and inconsistent process results, especially during E-H mode transitions in ICP processes.
Innovation Solution
An impedance-matching method and device that adjusts the parameter value of an adjustable element, such as a capacitor, using a pre-stored optimal matching path and an automatic matching algorithm to achieve impedance matching, ensuring consistent plasma formation across different wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional automatic matching algorithm is used to adjust impedance matching parameters, then impedance matching can be achieved, but matching time varies for different wafers causing inconsistent process results
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal matching paths for different process conditions before actual wafer processing. The system divides the matching period into multiple time segments and pre-determines the adjustable element parameters for each segment, creating a lookup table of optimal paths. During operation, the system simply retrieves and executes the pre-calculated path corresponding to the current process state, eliminating the need for real-time iterative adjustment and ensuring consistent matching time across different wafers.
2Reliability
If impedance matching is performed during E-H mode transition in ICP process, then plasma can be formed, but the unstable state causes different and non-repetitive matching paths
Solution Approach 1:
The patent applies segmentation by dividing the impedance matching process into multiple discrete time segments during the plasma ignition period. Each time segment has pre-calculated optimal parameters for the adjustable element. This segmentation allows the system to navigate through the unstable E-H mode transition by following a predetermined sequence of parameter values, ensuring reproducible matching paths across different wafers despite the inherent plasma instability during ignition.
3Reliability
If RF energy is directly transmitted to process chamber without impedance matching, then device complexity is reduced, but RF energy reflection occurs and plasma cannot be formed
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the electrical parameters (capacitance or inductance values) of the adjustable element in the impedance-matching device during the matching process. The system changes these parameters according to pre-calculated optimal paths that correspond to different stages of plasma ignition and processing. This allows the relatively simple impedance-matching device structure to effectively achieve plasma formation by optimizing the electrical parameters rather than increasing structural 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 method improves the repetitiveness and stability of the semiconductor process, enhances the consistency of process results, and allows for precise adjustment of plasma impedance, particularly during transitions and in processes with short timescales.
Implementation Method 1
a radio frequency (RF) power supply transmits RF energy to a process chamber through an impedance-matching device to excite a process gas in the process chamber to form a plasma
Implementation Method 2
An impedance-matching device needs to be connected between the RF power supply and the process chamber to adjust the input impedance at the backend of the RF power supply to 50 ohms to normally transmit the RF energy, that is, realize the impedance matching
Data Source
AI summary
The present disclosure provides an impedance-matching method applied to a semiconductor process apparatus, an impedance-matching device, and the semiconductor process apparatus. The impedance-matching method includes adjusting a parameter value of an adjustable element of an impedance-matching device to a preset initial value at beginning of a process, when a radio frequency (RF) power supply is powered on, adjusting the parameter value of the adjustable element according to a pre-stored optimal matching path corresponding to the process, and adjusting the parameter value of the adjustable element using an automatic matching algorithm after reaching end time of the preset matching period until impedance-matching is achieved. The optimal matching path includes parameter values of the adjustable element corresponding to different moments in a preset matching period.