Reynard Corporation has long been a global optical component supplier to the semiconductor industry and also offers optical sub-assembly design & support.
The process to manufacture semiconductor wafers is comprised of a mix of many high-precision process and inspection steps. Machine vision cameras are utilized in this process for many reasons, such as identifying wafer alignment and orientation, to identify and record defects, sorting wafers, and to provide feedback for the automated process steps. The needs of these machine vision systems vary greatly, depending on their purpose. Operation can be spectral waveband specific, such as ultraviolet (UV), visible (VIS), or infrared (IR), or be broadband, covering two or more of these bands. Additionally, various optical components are needed such as beamsplitters, mirrors, filters, patterns, and anti-reflection coatings on windows and lenses.
Bandpass filters can be used to filter out extraneous information for laser inspection. For example, a broadband detector can become noisy from the radiation of light outside of the wavelength band of interest. In these cases, a bandpass filter is added to the optical system that will block out light that is outside of the intended wavelength band.
Reynard custom BullseyeTM apodizers can be used to provide uniform illumination from an unbalanced light source. Typically a light source will have a gaussian type output distribution, causing non-uniformity in a viewing area. This BullseyeTM filter will help to flatten the illumation beam for a uniform viewing area.
The need for optical filters varies widely and can be customized for specific instruments. Examples of some filtering needs are:
- Longpass filters can be used for fluorescence inspection applications (e.g. dust and lint inspection).
- Shortpass and longpass filters can discriminate incoming laser light by arrival angle – allowing the user to create a bright-field or dark-field image with a single optical element
- Variable bandpass or edge filters combined with linear CCDs can be used for color and film thickness determination
- Neutral Density filters adjust a light source uniformly across a wide spectral range.