DE102005048359A1 - Optical radiation methods/devices for converting nano structures has nano structures for improving optical behavior in components/apparatus and/or improving behavior of sensors - Google Patents

Abstract

Nano structures (2; 4, 4a) improve the optical behavior of components and apparatus and/or improve the behavior of sensors. Produced via a special reactive icon etching process, a nano structure (2) can be modified regarding composition of its materials and can be provided with adequate coatings. The amount of material used for a base layer (3) can be reduced by supplying a buffer layer. Independent claims are also included for: (a) a sensor component formed by a nano structure with statistically distributed structure elements; (b) an optical coating structure for use in optical components or optical devices; (c) an optical device with a lining as a wide-band optical absorber; (d) a digital projector with mirror technology/digital light processing; (e) a device with the means of converting optical rays into heat independent of wave-length; (f) an optical element for emitting optical rays with a beam hole; (g) a reflecting reference device for determining low reflecting values; (h) a photo-electronic component with a low-reflecting layer in an optically active window area, made from silicon needles regularly distributed statistically and low in defective crystals; (i) an optical window with silicon and wide-band transparency in an infrared range; (j) a method for adapting a refraction index for an optically active window in a photoelectric component; (k) a method for protecting a layer that has needle-shaped structure elements with a large aspect ratio and is a component of a chemical sensor; (l) a method for rendering a surface with silicon passive for a semiconductor component; (m) a method for creating self-organized nano structures in the area of a window opening in an integrated switching circuit with an opto-electronic component or on a discrete opto-electronic component.

Description

silicon can be used as an IR window. At a wavelength of greater than 1000 nm, silicon begins to become transparent and absorbs less and less Light.

There the interface Air / silicon has a reflection of more than 30% and a window always two interfaces has, lets an untreated piece Silicon, despite its transparency in the infrared only about 50% of amount of light transmitted through, the other half is lost by reflection.

• 1. Die Schichtdicken müssen eng toleriert sein.
• 2. Die Entspiegelung gelingt nur für eine bestimmte Wellenlänge befriedigend, man findet auch andere Wellenlängen, die andere Interferenzordnungen darstellen, für die gut entspiegelt wird, diese sind aber nicht frei wählbar
• 3. Um die Reflexion in einem breiten Wellenlängenbereich auf nahe Null zu vermindern, versagt eine Entspiegelung durch einfache λ/4-Schichten. Es wären Materialien mit fein abgestuften Brechzahlen zwischen 1 und 3.4 notwendig. Solche sind aber in der konventionellen Halbleitertechnologie nicht verfügbar.
• 4. Die aufgebrachten Schichten müssen im verwendeten Wellenlängenbereich eine sehr geringe Absorption aufweisen.

Although there are possibilities to improve transparency through reflection-reducing layers, for example by means of λ / 4 layers, the following restrictions or disadvantages remain:

• 1. The layer thicknesses must be tightly tolerated.
• 2. The anti-reflection succeeds satisfactorily only for a certain wavelength, one also finds other wavelengths that represent other interference orders for which there is good anti-reflection, but these are not freely selectable
• 3. In order to reduce the reflection in a broad wavelength range to near zero, an antireflection by simple λ / 4 layers fails. It would be necessary materials with finely graded refractive indices between 1 and 3.4. However, such are not available in conventional semiconductor technology.
• 4. The applied layers must have a very low absorption in the wavelength range used.

Of the Invention is based on the object, an IR window made of silicon to create broadband transparency.

Is solved This object with the features stated in the characterizing part of claim 1.

Of the The subject of claim 1 has the advantages that by the RIE process generated self-assembled nanostructures form effective medium for that the steady transition the two material properties provides. This can be done in the infrared Range with the modification of the silicon surfaces reaches a transmission of over 90 become. The modified surface meets her Task by taking the interface properties between the silicon and air or vacuum changed so that between them no impedance jump occurs, but the different ones Impedances constantly merge into each other. Here is the material for the wished Wavelength range is not absorbent. The interface modification of Silicon is used for reflection suppression and thus the improved Transmission. Decisive here is the shape of the needle-shaped structures the surface. The structures form an effective medium for the steady transition the two material properties provides. A one-sided surface modification already achieves a transmission of about 70%.

In the 1 the transparency of a sample with one-sided modified surface is shown.

The diagram contains a theoretical ( 1 ) and a measured ( 2 ) Curve.

The Theory neglected the absorption of silicon for short wavelengths.

For infrared Light from 1200 nm, the theoretical values of 70% are well hit.

One Problem with a two-sided surface modification is the low mechanical strength of the structures produced, so that the handling of the window is difficult.

The surface modification can target certain types of photoresist masking techniques Be limited areas, so that mechanically stressed by optically transparent areas can be separated easily. In order to the disadvantage of difficult handling is eliminated, a stable, if necessary, also air, liquid or vacuum-tight installation of such a window is readily available possible.

Claims (4)

Optical window made of silicon with improved broadband transparency in the IR range, characterized in that both surfaces with the RIE method needle-like structures in nanodimensions with a high aspect ratio greater than 4: 1, using the working gases oxygen and SF ₆ without the use of additional funds have been self-organizing generated for targeted mask formation during the etching process in a single process step, as has already been proposed possess. Silicon optical window according to claim 1, characterized characterized in that the nanostructures are provided with an SOG (spin on glass) layer against mechanical destruction protected are. Optical window according to claim 2, characterized that the protection consists of hydrogen silsesquioxane (HSQ). Optical window according to claim 1, characterized in that the reflection-reduced nanos Restructuring by conventional masking technology is limited to certain areas of the window and thus untreated, mechanically stable and easily sealed against air, liquids and vacuum areas remain.