Journal of Applied Science Studies - Ozean Publications
Journal of Applied Science Studies - Ozean Publications
Journal of Applied Science Studies - Ozean Publications
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<strong>Ozean</strong> <strong>Journal</strong> <strong>of</strong> <strong>Applied</strong> <strong>Science</strong>s 1(1), 2008<br />
Metal Layer<br />
Figure 2. Metalization on top <strong>of</strong> contact holes for electrical connections.<br />
BACKGROUND<br />
Normally, it was found that the intended square shape contact holes had become rounded due to the<br />
diffraction <strong>of</strong> light passing through large area <strong>of</strong> the photomask. Apart from this, the surface topology also<br />
affected the reflection paths as shown in figure 3. As a result, this phenomena will affect the uniformity <strong>of</strong><br />
linewidth throughout the wafers.<br />
E<br />
Thin film Interference<br />
Reflected light<br />
Reflective notchnig<br />
R top<br />
R Bottom<br />
Resist<br />
E 1<br />
E 3<br />
t1<br />
E 0<br />
E 2<br />
t2<br />
Substrate<br />
Figure 3. Reflection <strong>of</strong> light on uneven film’s surface.<br />
The reflection, due to surface topology, has the following relationship [2]:<br />
2 2<br />
1 ⎡sin ( I1 − I2) tan ( I1 − I2)<br />
⎤<br />
R = ⎢<br />
+<br />
2 2 ⎥<br />
2 ⎣sin ( I1 + I2) tan ( I1 + I2)<br />
⎦<br />
(1)<br />
48
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