3D Photonic Structures by Sol-Gel Imprint Lithography
- PDF / 3,223,072 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 229 Views
1002-N03-05
3D Photonic Structures by Sol-Gel Imprint Lithography Marc Verschuuren, and Hans van Sprang Philips Research, High Tech Campus 4 (mailstop 12), 5656 AE, Eindhoven, Netherlands
ABSTRACT We present a new and relatively simple process to manufacture three-dimensional submicron structures over square centimeter areas using a soft stamp imprinting process. The roomtemperature replication process shows excellent quality in transferring features directly into inorganic silica material with pattern distortion smaller than 0.03% over an area of 15x15mm2. Using a self assembly planarization method the imprinting process can be repeated to form threedimensional structures. As a demonstration, a multilayer stack of four crossed gratings is shown. INTRODUCTION Two-dimensional photonic crystals are being applied to increase or modify the light extraction from high-index inorganic LED materials such as GaP and GaN. They can also be applied as in photonic integrated circuits to act as wavelength selective channel splitters or filters.1,2 Three-dimensional photonic crystals are foreseen in applications to enhance the light extraction and directionality of LEDs and lasers and may also find applications in (bio)sensors. The fabrication of two-dimensional photonic crystals can be done using optical -, electron beam lithography or imprint techniques.3,4 The fabrication of 3D photonic crystals is more complex as multiple layers must be aligned and patterned on top of each other to form the crystal structure. An example of such a three dimensional photonic crystal is a so-called “woodpile” structure, which consists of stacked layers of aligned gratings. A woodpile unit cell consists of four layers, where the third and fourth layer are shifted half a gating period with respect to first and second layer. (inset figure 1D). Woodpile crystals are interesting as calculations show that a full photonic bandgap will already open if the bars have an index of refraction of 2.2 and are surrounded by air.5 In this article we present a new method to fabricate multi-layer sub-micron structures using direct patterning of an inorganic imprint resist, combined with a self-assembly method for grating planarization. The process has been simplified and reduced to 8 steps that have to be executed repeatedly to create a woodpile type open 3-D structure (see figure 1C). PROCESS FLOW In figure 1 the process flow used to obtain a woodpile crystal structure is shown. First a rubber stamp is fabricated from a master and an inorganic imprint resist is prepared (1A). In 1B master and resist are then used in process steps 1 to 8 fabricate a grating layer. This cycle is repeated until the desired number of grating layers is reached. After printing a stack of grating layers the structure is calcined. As an example, a four-layer stack of gratings is shown in figure 1C. Each process step that was used to fabricate this structure will be discussed in this paper.
B.
A.
C.
Master by E-beam 2. Imprint grating
3. Cure
D.
4. Breakthrough RIE etch
Rubber s
Data Loading...
