Precharge Control for Semiconductor Wafer Inspection
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Solution Overview
Problem
Conventional methods for inspecting semiconductor wafers struggle to accurately determine the charged state of the surface, leading to reduced reliability in defect detection and increased time in setting optimal precharge conditions, which affects the sensitivity and stability of the inspection process.
Innovation Solution
A pattern inspection apparatus that includes an electron beam irradiation system, a detection system, and a charge formation mechanism using a second electron source to measure and adjust the current flowing through the substrate, ensuring a predetermined target value is achieved, thereby stabilizing the charge state and improving defect detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an operator visually determines precharge conditions by repeating electron beam irradiation, then the charge state can be adjusted, but the time required for setting precharge conditions increases significantly
Solution Approach 1:
The system automatically measures the absorption current and determines the charge state without operator intervention. The measurement unit continuously monitors the current flowing through the substrate during electron beam irradiation, and the control unit automatically adjusts precharge conditions based on measured values, eliminating the need for repeated manual visual inspection and significantly reducing setting time.
Solution Approach 2:
The system implements a feedback mechanism where the measurement unit measures the absorption current in real-time during electron beam irradiation, and the control unit uses this measured information to automatically adjust and determine optimal precharge conditions. This closed-loop feedback system replaces manual visual determination with automated measurement-based control.
2Reliability
If electron beam irradiation is performed multiple times to adjust precharge, then the charge state can be optimized, but the charge state changes due to repeated irradiation requiring waiting time
Solution Approach 1:
The measurement unit automatically and continuously monitors the absorption current during electron beam irradiation, providing real-time feedback on the charge state. This eliminates the need for operators to wait for charge relaxation between irradiation attempts, as the system continuously tracks charge state changes and determines optimal precharge conditions in a single continuous measurement process.
Solution Approach 2:
The measurement unit performs continuous absorption current measurement throughout the electron beam irradiation process without interruption. This continuous monitoring allows the system to track charge state evolution in real-time and determine optimal precharge conditions without requiring periodic waiting periods for charge relaxation, maintaining continuous productive action.
3Reliability
If precharge is performed on substrates with thick insulating films, then charge can be formed, but the image becomes saturated and white causing defect detection failure
Solution Approach 1:
The measurement unit measures the absorption current to determine the actual charge state of the substrate. The control unit uses this measured information to precisely control the precharge amount, stopping irradiation when the optimal charge state is reached. This feedback control prevents excessive charge accumulation that would cause image saturation, even on substrates with thick insulating films.
Solution Approach 2:
The system dynamically adjusts the precharge parameters (electron beam current, irradiation time, irradiation area) based on real-time absorption current measurements. By changing these parameters adaptively rather than using fixed precharge conditions, the system achieves optimal charge states without oversaturation, maintaining image quality for defect detection.
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
This configuration allows for the optimal setting of precharge conditions, enhancing defect detection sensitivity, ensuring reliable and stable inspections, and reducing the time required for fault countermeasures in semiconductor manufacturing.
Implementation Method 1
when an electron beam is irradiated onto a semiconductor wafer, a charge phenomenon depending on a pattern material of it occurs. A potential difference on a surface of the semiconductor wafer is reflected on a secondary electron emission efficiency
Implementation Method 2
with regard to precharge for irradiating electrons onto the semiconductor wafer before acquiring an inspection image, whether a precharge result becomes equal to a desired charge amount is required to be known
Implementation Method 3
a current measuring means to measure a value of a current flowing in the substrate while the charge is formed on a surface of the substrate by the charge formation means
Data Source
AI summary
Provided is a pattern inspection apparatus including: a charge formation means which forms charge on a surface of a substrate (7) by generating an electron beam from a second electron source (20) which is different from an electron source (1) which generates an electron beam before irradiating an electron beam (3), a current measuring means (34) which measures a value of current flowing in the substrate while the charge is formed on the surface of the substrate by the charge formation means; and an adjustment means (37) which adjusts the charge formed by the charge formation means so that the value of the current measured by the current measuring means is a predetermined target value. Provided is also a pattern inspection method which uses the pattern inspection apparatus. Thus, it is possible to easily set an optimal condition of precharge executed before inspection of a pattern formed by a semiconductor apparatus manufacturing process and automatically inspection whether the precharge is good. Then, the inspection result is fed back to the operation afterward. This prevents lowering of the reliability of the inspection result and always enables a stable inspection.