How to Select a Cold Mirror for Semiconductor Lithography

Every Semiconductor Lithography system eventually meets the same question: where does the light go, and how much of it survives the turn? A well-specified Cold Mirror…

Every Semiconductor Lithography system eventually meets the same question: where does the light go, and how much of it survives the turn? A well-specified Cold Mirror answers both, which is why it earns a place on the bill of materials long before the enclosure is drawn.

A Cold Mirror is an optical component built so that reflection happens at the coated front face rather than through a substrate. With a dichroic (reflects visible, transmits IR) on a float or borosilicate glass base, the part delivers > 98% visible reflectivity across visible reflect / IR pass while keeping the useful aperture clean and ghost-free.

When light meets the Cold Mirror, almost all of it bounces from the front coating. The substrate merely holds the coating in place; it does not need to be traversed by the useful beam, so transmission losses and secondary reflections stay minimal — a real advantage in sensitive Semiconductor Lithography setups.

The dichroic (reflects visible, transmits IR) is where performance is won or lost. Deposited by vacuum processes, it is tuned so the reflected wave adds constructively across visible reflect / IR pass, reaching > 98% visible. Getting the layer thickness right is a precision task: a few nanometers off and the reflectivity curve shifts.

A Cold Mirror starts as a float or borosilicate glass blank. We hold it to 4–6λ flatness and 60-40 surface quality, then apply the dichroic (reflects visible, transmits IR). The substrate never sees the beam directly, but its figure sets the limit on how straight the reflected wavefront stays.

When you specify a Cold Mirror, the numbers that matter are flatness 4–6λ, finish 60-40, and the reflectance > 98% visible across visible reflect / IR pass. Thickness 1–3 mm is mostly about handling and mount compatibility, but it still belongs on the print.

Where projecting nano-scale patterns with extreme precision, a Cold Mirror earns its place by doing one job reliably: turning the beam without adding noise. In Semiconductor Lithography that reliability is the difference between a prototype and a shippable product.

A short checklist covers most Semiconductor Lithography cases: what band (visible reflect / IR pass)? at what angle? how much loss is allowed (> 98% visible)? then pick dichroic (reflects visible, transmits IR) on float or borosilicate glass at 1–3 mm. Getting these four right avoids the most common rework.

For Semiconductor Lithography, do not over-specify. Choose the dichroic (reflects visible, transmits IR) that covers visible reflect / IR pass at the angle you use, keep flatness at 4–6λ unless the wavefront demands more, and you will have a Cold Mirror that is both capable and economical.

A Cold Mirror is tougher than it looks but softer than you think. Fingerprints on the dichroic (reflects visible, transmits IR) are the usual cause of field failures, so edge-handling and capped storage pay off. A little discipline keeps > 98% visible where it belongs.

Because we control cutting, coating and finishing in one place, a Cold Mirror can move from your drawing to a finished part without hand-offs. The float or borosilicate glass is cut to ±0.01 mm, the dichroic (reflects visible, transmits IR) is vacuum-deposited for > 98% visible over visible reflect / IR pass, and the result is inspected to 4–6λ flatness and 60-40 quality.

Most of the engineering in a Cold Mirror lives in its dichroic (reflects visible, transmits IR). The stack is designed for visible reflect / IR pass and delivers > 98% visible, and its environmental protection layer keeps the metal from tarnishing so the mirror keeps working year after year.

The dichroic (reflects visible, transmits IR) is where performance is won or lost. Deposited by vacuum processes, it is tuned so the reflected wave adds constructively across visible reflect / IR pass, reaching > 98% visible. Getting the layer thickness right is a precision task: a few nanometers off and the reflectivity curve shifts.

Behind the coating sits the float or borosilicate glass substrate. Its job is mechanical: hold flatness, survive cutting and mounting, and stay stable with temperature. For many Semiconductor Lithography uses, float or borosilicate glass hits the right balance of cost, flatness (4–6λ) and workability.

Coating a Cold Mirror means laying down a dichroic (reflects visible, transmits IR) whose optical thickness is controlled to a fraction of a wavelength. Done well, the part holds > 98% visible over visible reflect / IR pass; done carelessly, it drifts and the system loses light it cannot afford to lose.

How the part is checked

Before a Cold Mirror leaves the line it is inspected for flatness (4–6λ), finish (60-40) and reflectance (> 98% visible over visible reflect / IR pass). A simple 45° visual check reveals coating defects, and a flatness test confirms the wavefront stays within tolerance — the same discipline JYOPTO applies across its optical glass, vacuum-coating and precision cold-processing since 2020.

Behind the coating sits the float or borosilicate glass substrate. Its job is mechanical: hold flatness, survive cutting and mounting, and stay stable with temperature. For many Semiconductor Lithography uses, float or borosilicate glass hits the right balance of cost, flatness (4–6λ) and workability.

Typical specs worth putting on a drawing: surface flatness 4–6λ, surface quality 60-40 (scratch-dig), substrate float or borosilicate glass, thickness 1–3 mm, and reflectivity > 98% visible over visible reflect / IR pass. Stating these up front saves rounds of sampling later.

Most Semiconductor Lithography engineers reach for a Cold Mirror when they need projecting nano-scale patterns with extreme precision. The component's job is unglamorous but essential — keep the light on course and the loss low.

Our production of a Cold Mirror follows a simple, repeatable route: laser-cut the float or borosilicate glass to ±0.01 mm, smooth the edges, deposit the dichroic (reflects visible, transmits IR), and inspect to 4–6λ / 60-40. Thickness options span 1–3 mm, and the same Hangzhou line that builds first-surface mirrors also runs windows, substrates and custom coatings.

Substrate choice for a Cold Mirror is a trade between optical grade and budget. float or borosilicate glass is a common pick because it can be cut and polished to 4–6λ flatness and a 60-40 surface, which is plenty for the reflection quality most Semiconductor Lithography systems require.

Behind the coating sits the float or borosilicate glass substrate. Its job is mechanical: hold flatness, survive cutting and mounting, and stay stable with temperature. For many Semiconductor Lithography uses, float or borosilicate glass hits the right balance of cost, flatness (4–6λ) and workability.

In short

For Semiconductor Lithography, the Cold Mirror is less a commodity than a tuned component. Specify the band (visible reflect / IR pass), the reflectivity (> 98% visible) and the figure (4–6λ), and you will spend less time debugging light you cannot see. That is the whole game.