Visualize a personal computer condensed to the size of a candy bar, and the complexity that structure would need to accomplish the same functions. That's essentially what's happening in the world of semiconductor manufacturing. Feature sizes are shrinking under 5 nanometers (nm) — with 2nm and 1nm chips on the near horizon — requiring more advanced metrology tools.

Below, you can review the essential role metrology plays in semiconductor manufacturing, explore current challenges and new developments, and see how precision motion control stages are set to change the landscape of semiconductor metrology. 

The Growing Importance of Metrology in Semiconductor Manufacturing

Semiconductor manufacturing is experiencing a large movement toward smaller feature sizes. Integrated circuits (ICs) are being produced at the nanometer scale, making precision and accuracy more important than ever. Additionally, the complexity of 3D chip architecture and advanced packaging requires solutions for greater quality control at every stage of the manufacturing process.

Metrology in semiconductor manufacturing is the process of measuring and inspecting semiconductor chips at every manufacturing stage. Even the smallest of flaws can lead to errors, and when working at nanometer scale under the tightest manufacturing tolerances, anything but absolute accuracy and precision results in failure.

Semiconductor metrology systems reinforce quality control at every stage, ensuring:

• Higher yields
• Faster time to market
• Reduced defects
• Greater process optimization
• Less waste
• Lower production costs
• Compliance with strict industry standards and regulations

Impact of Positioning Errors on Measurement Reliability

Positioning errors in semiconductor manufacturing metrology tools can significantly affect the reliability of the measurements. Without reliable and accurate metrology measurements, the manufacturing process can encounter significant challenges, such as:

• Inaccuracies: The most common result of incorrect chip or wafer positioning is inaccurate measurements of dimensions, surface roughness, and composition. If the position isn't accurate, the equipment is likely measuring the wrong location on the sample.
• Distorted images: Positioning errors can cause distortions in the images. For scanning electron microscopy and atomic force microscopy, this can inhibit the ability to accurately interpret data.
• Lower resolution: Metrology relies on precise positioning to detect small features and defects, and incorrect positioning can hamper the resolution and affect analysis.
• Misalignment: Incorrect chip positioning, particularly in overlay metrology, can lead to uncaught defects in the alignment of different layers, impacting device performance.
• Nonrepeatability: Measurements that vary, even slightly, make it difficult to track changes and accurately analyze samples.

The Evolving Challenges of Semiconductor Metrology

Semiconductor manufacturing is rapidly evolving alongside advancements in nanotechnology. Modern chip architectures require defect detection at nanometer and atomic scales. Semiconductor metrology equipment is facing the following challenges:

• Shrinking feature sizes: Sub-5nm nodes, including the new 3nm and the upcoming development of 2nm and possibly 1nm chips, require absolute precision. Certain metrology techniques, like optical and electrical probing, may not be able to accurately measure dimensions and features, requiring the development of new techniques and equipment.
• Greater complexity: Along with smaller feature sizes, modern chips are becoming increasingly complex with 3D structures and new materials. Using 2D measurement techniques may not be enough to get an accurate analysis.
• More intricate packaging schema: New packaging schemes like 3D-ICs involve complex stacking and connections. Metrology techniques need to adapt to these new structures to ensure accuracy and reliability.

Precision Motion Control Stages: The Answer to Growing Semiconductor Complexity

Advanced motion stages are enabling next-generation semiconductor inspections. Precision motion control systems represent the highest level of motion control, capable of running along multiple axes. Key features of these systems include accuracy, repeatability, resolution, and stability.

By automating the chip inspection process, precision motion control stages can achieve advanced precision and repeatability at the micron and sub-micron levels. This is essential for semiconductor manufacturers looking to accelerate inspection times, increase yields, and improve quality control.

The five main motion control stages are:

1. Linear Stages

Linear stages handle precision requirements along a single axis. They operate on linear bearing guideways with assorted actuator methods, meaning they can operate faster and produce minimal vibrations compared to other drive systems. In semiconductor manufacturing, linear stages can be used for scanning samples, positioning probes, and moving optical elements.

The benefits of linear stages include: 

• Precise wafer positioning
• Minimized runout
• Consistency and repeatability
• Higher productivity

2. XY Stages

XY stages supply 2D mapping requirements, allowing for two degrees of freedom (2-DOF). The dual orthogonal axes translate to greater accuracy and coverage in wafer defect detection and surface mapping. Flat movement along the X and Y planes is facilitated by different kinds of motion mechanisms:

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• Rollers: While offering lower accuracy, rollers are the simplest and most cost-effective motion mechanism.
• Crossed rollers: These rollers use crossed bearings for greater reliability and stability.
• Ball bearings: Ball bearings are favored for their versatility, and they operate well in low- and high-speed applications.

3. Rotary Stages

Rotary stages enable rotational movement along a single axis. A bearing system controls the rotor movement, generating minimal friction and vibration. Advanced rotor motion control is highly accurate up to fractions of a degree, lending unmatched precision to sample positioning, surface topography and composition inspection, and lithography.

4. Z-Axis and Lift Stages

Operating over a single DOF, the Z-axis stage is a vertical lift that offers precise vertical motion. Considerations when choosing Z-axis and lift stages include:

• Travel ranges and motion profile requirements
• Required load capacity
• Speed
• Force resistance

In semiconductor manufacturing, these stages can assist in stacking samples and precision alignment during production. Manufacturers can combine Z-axis and XY-axis stages to create a custom multi-axis positioning system.

5. Air Bearing Stages

Air bearing stages use air for frictionless motion, eliminating metal-on-metal contact, reducing wear, friction, and vibrations. Other benefits include:

• Cleanliness: Air bearing stages are suitable for cleanroom applications.
• Less wear and tear: This stage requires minimal maintenance and upkeep.
• Consistency: Air bearing stages come with extremely low margins of error during motion.

Because air bearing stages offer ultra-high precision measurements, they are perfect for extra-sensitive metrology that requires nano or micronewton force control. Their contactless nature makes them perfect for applications that require high repeatability and stability, like wafer scanning.

The Critical Role of Precision Motion Control Systems in Modern Metrology Equipment

With accuracy and precision more important than ever — and more challenging to achieve — precision motion control systems are the ideal solution for modern semiconductor metrology.

Motion control stages offer the following for semiconductor metrology:

• Accuracy: Motion control systems enable the most accurate positioning of samples and measurement tools to minimize errors and improve data quality.
• Repeatability: The repeatability of a motion system references its precision and ability to replicate results without deviations or inconsistencies. This is essential to reduce errors in the manufacturing and inspection process.
• Resolution: Identifying defects in modern chips requires extremely high resolution, which is made possible by the enhanced positioning of precision motion control systems.
• Stability: When dealing with smaller, complex features, the stability provided by precision motion control stages makes ultra-high accuracy and precision more achievable.
• Speed and throughput: In most manufacturing contexts, there's an interplay between process speed and accuracy. Motion control systems that maintain high levels of accuracy even in high-speed applications can empower faster measurement times in high-volume manufacturing.

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Choose Reliant Systems, Inc. for Precision Automation Systems

As semiconductor manufacturing trends evolve, precision motion control stages will be essential in manufacturing and metrology applications. Reliant Systems, Inc. brings expertise in precision motion control solutions for semiconductor industry applications. We specialize in high-precision motion systems and can build innovative, custom solutions for your needs.  

To learn more about our contract manufacturing and custom motion solutions, reach out to us today.