Three Magnifications, One Point of Focus, for Wafer Inspection
A UK semiconductor test equipment maker wanted to inspect wafers at three magnifications without changing objective or refocusing. They had the idea but not the route. We designed a three-channel optical system, with every channel aimed at the same point within 2 microns, then made and assembled it in Rye.
See the Whole Wafer, Then Zoom In Without Touching a Thing
Detail on a semiconductor wafer is very fine and complex. The customer wanted one channel to give a wide view of the wafer, and further channels to zoom in on finer detail, all without changing objective or refocusing.
Splitting the light into separate channels meant lining up a series of reflectors, and every channel had to aim at the same point on the wafer to within 2 microns.
The system also had to:
- Work with a Blackfly S BFS-U3-200S7C-C colour camera without vignetting
- Image in full colour under white light illumination
- Take Mitutoyo infinity-corrected objectives on a matching thread
The customer knew what they wanted the system to do, but not how it could be designed or built.
A quick feasibility study gave initial prices and the confidence to go ahead. We agreed the scope and backed ourselves to meet it in full, with nothing paid up front, so the customer carried no risk.
Three Problems, Solved as One System
- 01
Optical Channels
Three imaging channels, each at a different magnification, all sharing the same objective and the same point on the wafer.
- 02
Illumination
White light illumination for full-colour imaging, even across the field in every channel.
- 03
Mechanics and Reflectors
Reflectors that split and steer the light into each channel, held in one rigid housing.
A Rigid Box, and Focus Matched Across Channels
Holding three channels on the same point to within 2 microns needs a structure that will not move. We machined a large, rigid optical box from aluminium to house the whole system.
Each channel has its own focus adjustment, set so that all three focus at exactly the same place. Once the wafer is in focus in one channel, it is in focus in all of them, so the operator can switch magnification with no refocusing.
What Each Channel Sees
The same point on a wafer, imaged through each channel with a 2× objective, with no refocusing in between.
Made in Rye, Start to Finish
Design, lens manufacture, coating, metalwork and assembly were all carried out at our site in Rye, East Sussex, so one team was responsible for the whole system.
- Lens manufactureLenses for all three channels made on our Optotech CNC lines.
- Optical coatingCoated in house for full-colour white light imaging.
- MetalworkRigid aluminium optical box and mounts machined on site.
- AssemblyReflectors aligned and channel focus matched in house.
From Design Analysis to Approval on the Customer's Rig
- 01
Predicted in Design
Monte Carlo tolerance analysis confirmed the design would hold its performance once made.
- 02
Checked in Rye
Focus matched across all three channels, no vignetting, and even illumination across the field.
- 03
Approved on Their Rig
We took the finished system to the customer. It was tested on their rig for a day and approved.
A three-channel inspection system with every channel on the same point within 2 microns, switching magnification with no refocusing, and approved after one day on the customer's rig.
Have the Idea, but Not the Route to Build It?
Tell us what your system needs to do. We will carry out a quick feasibility study with initial prices, agree the scope with you, and back ourselves to meet it in full.
We reply within one working day. All projects can be handled under NDA.