Fabrication of high-aspect-ratio microgrooves with laser-assisted wet etching for micro heat pipe

2006 ◽  
Author(s):  
Kwang H. Oh ◽  
M. K. Lee ◽  
S. J. Kwon ◽  
S. H. Jeong
Keyword(s):  
Aspect Ratio ◽  
Heat Pipe ◽  
High Aspect Ratio ◽  
Wet Etching ◽  
Micro Heat Pipe

Design and Fabrication of a Metallic Micro Heat Pipe Based on High-Aspect-Ratio Microchannels

2006 ◽  
Author(s):  
K. H. Oh ◽  
M. K. Lee ◽  
S. H. Jeong
Keyword(s):  
Aspect Ratio ◽  
Heat Pipe ◽  
Capillary Pressure ◽  
High Aspect Ratio ◽  
Scanning Speed ◽  
Cooling Capacity ◽  
Wet Etching ◽  
Direct Writing ◽  
Etching Technique ◽  
Micro Heat Pipe

The cooling capacity of a micro heat pipe is mainly governed by the magnitude of capillary pressure induced in the wick structure. For microchannel wicks, a higher capillary pressure is achievable for narrower and deeper channels. In this study, a metallic micro heat pipe adopting high-aspect-ratio microchannel wicks is fabricated. The micromachining of high-aspect-ratio microchannels is done using the laser-induced wet etching technique in which a focused laser beam irradiates the workpiece placed in a liquid etchant along a desired channel pattern. Because of the direct writing characteristic of the laser-induced wet etching method, no mask is necessary and the fabrication procedure is relatively simple. Deep microchannels of an aspect ratio close to 10 can be readily fabricated with little heat damage of the workpiece. The laser-induced wet etching process for the fabrication of high-aspect-ratio microchannels in 0.5mm thick stainless steel foil is presented in detail. The shape and size variations of microchannels with respect to the process variables, such as laser power, scanning speed, number of scans, and etchant concentration are closely examined. Also, the fabrication of a flat micro heat pipe based on the high-aspect-ratio microchannels is demonstrated.

Topology Optimization of Micromachined Structures With the Manufacturing Constraints of KOH Etching of (110) Silicon

2008 ◽  
Author(s):  
Sudarshan Hegde ◽  
G. K. Ananthasuresh
Keyword(s):  
Topology Optimization ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Cost Effective ◽  
Wet Etching ◽  
Minimum Length ◽  
The Cost ◽  
Design Parameterization ◽  
Koh Etching ◽  
Si Wafer

The focus of this paper is on designing useful compliant micro-mechanisms of high-aspect-ratio which can be microfabricated by the cost-effective wet etching of (110) orientation silicon (Si) wafers. Wet etching of (110) Si imposes constraints on the geometry of the realized mechanisms because it allows only etch-through in the form of slots parallel to the wafer’s flat with a certain minimum length. In this paper, we incorporate this constraint in the topology optimization and obtain compliant designs that meet the specifications on the desired motion for given input forces. Using this design technique and wet etching, we show that we can realize high-aspect-ratio compliant micro-mechanisms. For a (110) Si wafer of 250 μm thickness, the minimum length of the etch opening to get a slot is found to be 866 μm. The minimum achievable width of the slot is limited by the resolution of the lithography process and this can be a very small value. This is studied by conducting trials with different mask layouts on a (110) Si wafer. These constraints are taken care of by using a suitable design parameterization rather than by imposing the constraints explicitly. Topology optimization, as is well known, gives designs using only the essential design specifications. In this work, we show that our technique also gives manufacturable mechanism designs along with lithography mask layouts. Some designs obtained are transferred to lithography masks and mechanisms are fabricated on (110) Si wafers.

Drying of High Aspect Ratio Structures: A Comparison of Drying Techniques via Electrical Stiction Analysis

2009 ◽  
Vol 145-146 ◽  
pp. 87-90 ◽  
Author(s):  
Antoine Pacco ◽  
Masayuki Wada ◽  
Twan Bearda ◽  
Paul W. Mertens
Keyword(s):  
Aspect Ratio ◽  
Surface Area ◽  
High Aspect Ratio ◽  
Wet Etching ◽  
Large Surface Area ◽  
Defect Inspection ◽  
Feature Size ◽  
Aspect Ratios ◽  
Drying Techniques

Nanostructures with high aspect ratios, HAR, (ratio of height to lateral feature size) are of interest for many applications. One of the immediate advantages is the large surface area of these structures. In the field of DRAM manufacturing for example, the capacitance of cylindrical DRAM capacitors increases linearly with height. Wet etching and drying of these fragile high aspect ratio structures without lateral collapse (stiction) is a big challenge for the fabrication of DRAM capacitors. The problem with HAR structures is stiction during drying [1]. In order to reduce stiction by improvement of drying techniques, a good metric to quantify the occurrence of stiction is needed. However, currently used methods like SEM or brightfield defect inspection are extremely time-consuming.

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