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<title>Synchrotron Radiation: Progress of Lithography</title>
<h1>Synchrotron Radiation: Progress of Lithography</h1>
    Since the X-ray Lithography Station was put into operation in 1990, 
following the deep submicronic patterns down to 0.2 $\mu$m had been obtained 
by proximity X-ray lithography two years ago, more complicated patterns 
of microelectronic devices have been 
fabricated currently, including   
a mask and devices of SAWD(Surface Acoustic Wave Device) 
of 900 MHz 
frequency with 0.8$\mu$m pattern size, one of the key components for long 
distance communications(see Fig.1).<p>
   The test  of the prototype fabrication of SAWD shows that the central 
frequency response of 1.1 GHz is  achieved, but  the 
signal-to-noise ratio is low. More higher performance SAWD fabrication 
with centeral 
frequency of 1.3 GHz and thinner line width of 0.7 $\mu$m is underway.<p>
    Deep etching process for the fabrication with three dimensional 
microstructure such as components for micromechanics and micro-optics, 
 has enormous 
potential development in the near future. Deep etching lithography 
is the most important step in the 3-D fabrication.<p>
    To make a mask for deep etching technology, an  
absorbed pattern  of 1-2$\mu$m
 thickness has to be made at first using photolithography technology 
and electroplating. Then put it into the SR irradiation field for making 
the final mask with absorbed pattern of 10-20 $\mu$m thick. Recently  
polyamide as a mask membrane with thickness of 4$\mu$m and Gold as highly 
absorbed material with  thickness of 13 $\mu$m were 
obtained(see Fig.2).<p>

    Irradiation process was performed recently in the same chamber used 
for submicron in the beam line 3B1 of BSRF. Since the photon energy is rather 
low, a depth of more than 50 $\mu$m in PMMA is very difficult to reach. 
Higher penetration depth may needs harder X-rays.<p>

    Electroforming is the second major production step in the sequence of 
the LIGA technique. A metal structure with thickness of 32 $\mu$m
was showen in Fig.3.<p>
<author>Tang Esheng</author>
<p>
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February 1996 BEPC News<p>