Photon-Assisted Plasma Evaluation for Semiconductor Wafer Uniformity
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Solution Overview
Problem
Current plasma measurement techniques, such as Heavy Ion Beam Probes and Langmuir probes, are inadequate for evaluating low-temperature plasmas and fail to provide accurate, consistent measurements across the dimensions of semiconductor wafers, leading to potential damage from plasma irregularities during manufacturing processes.
Innovation Solution
A system utilizing a photon source, like a laser, to ionize neutral atoms, which are then directed through a plasma, allowing for energy analysis to evaluate plasma characteristics, including potential and density, across the wafer dimension using an energy analyzer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Heavy Ion Beam Probe systems are used to measure plasma, then plasma potential and density can be measured, but the system cannot effectively measure low-temperature plasmas due to insufficient electron impact energy for second stage ionization
Solution Approach 1:
The invention changes the ionization mechanism from electron impact ionization to photon-assisted ionization. By introducing a photon source (laser) with energy exceeding the second ionization potential, the system can ionize atoms in low-temperature plasma where electron temperatures are insufficient for traditional heavy ion beam probe operation.
Solution Approach 2:
The invention introduces photons as an intermediary to facilitate ionization. The photon source (laser) acts as a mediator that provides the necessary energy for second stage ionization of atoms in the plasma, enabling the heavy ion beam probe to function in low-temperature plasma environments where direct electron impact is insufficient.
2Measurement precision
If Langmuir probes are inserted into plasma for measurement, then plasma characteristics can be measured, but the probe disrupts the plasma and measurements are only at a single point reducing accuracy
Solution Approach 1:
The invention replaces the mechanical Langmuir probe insertion method with a non-contact optical measurement system. A laser beam passes through the plasma without physical contact, eliminating plasma disruption while enabling measurement of plasma characteristics through photon-plasma interactions.
Solution Approach 2:
The invention transitions from point measurements (single dimension) to spatially-resolved measurements across the plasma. By scanning the laser beam or using a beam with spatial extent, the system can measure plasma characteristics across multiple points simultaneously, providing two-dimensional or three-dimensional plasma profiles.
3Productivity
If conventional plasma measurement techniques are used in semiconductor manufacturing, then deposition and etching operations can be monitored, but plasma irregularities and gradients across the wafer dimension cannot be detected leading to potential damage
Solution Approach 1:
The invention extends plasma measurement from single-point monitoring to spatially-resolved measurements across the wafer dimension. The laser beam can be scanned or configured to probe plasma characteristics at multiple locations simultaneously, detecting gradients and irregularities that affect deposition and etching uniformity across the semiconductor wafer.
Solution Approach 2:
The invention enables real-time monitoring of plasma characteristics across the wafer dimension, providing feedback information about plasma uniformity and irregularities. This feedback can be used to adjust plasma process parameters to maintain consistent deposition and etching operations, preventing defects and damage to semiconductor structures.
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 precise measurement of plasma characteristics, including plasma potential and density, across the wafer dimension, improving the consistency and accuracy of semiconductor manufacturing processes by effectively addressing the limitations of existing technologies.
Implementation Method 1
A beam of neutral atoms ("neutrals") will be directed toward the plasma, and some portion of those neutrals will be excited, and in some preferred examples ionized, through interaction with photons from a photon source such as, in some examples, a laser.
Implementation Method 2
The doubly ionized particles will then be deflected by the magnetized plasma, and detected by an energy analyzer which can then discern the energy gained by the ions, and from that energy data identify the electric potential of the plasma at the point of ionization.
Data Source
AI summary
Described are a method and apparatus for evaluating a least one characteristic of a plasma. The described method uses photons to raise the excitation state to or past the point of ionization of atoms which will traverse the plasma to be evaluated. The ionization of the atoms, followed by the measurement of the energy of any resulting secondary ions, facilitates the determining of one or more characteristics of the plasma. In one example, the photons are provided by a laser which directs a beam to intersect, and in some examples to be collinear with, a beam of atoms directed through the plasma.