In general, in semiconductor manufacturing devices, the development of photoresists facilitates the patterning of small-dimensioned electronic and optical devices. An example of such photoresists is deep ultra violet (DUV) photoresists. The dimensions of DUV photoresist patterns are considerably smaller than those of conventional photoresist patterns. A metal etching process requires the formation of metal lines having a space smaller than 0.25 μm therebetween.
However, since such photoresist is sensitive to the reflectance of the metal lines, the reflectance needs to be reduced in order to form a successful pattern of the photoresist. Therefore, an anti-reflective layer of oxide has been used on the metal lines.
In an in-situ etching of the anti-reflective layer in a metal etching chamber, a gas having fluorine, e.g., CHF3, has been commonly used. However, in the etching process, a process for forming an initial plasma using a gas having fluorine has a certain drawback in that a higher pressure is required to turn on plasma.
Therefore, as shown in Table 1 in conventional plasma ignition processes, a preceding step having a higher pressure than that of a succeeding step is introduced to turn on plasma. Those skilled in the art are able to understand that the values shown in table 1 may vary.
TABLE 1CHF3 flowPressureSourceBiasrateAr flow rate(mTorr)power(W)power(W)(sccm)(sccm)Preceding12˜20600˜1000100˜2005˜3050˜90stepSucceeding6˜8600˜1000100˜2005˜3050˜90step
However, such conventional processes have a problem in that an error may occur due to a difference in the pressure of a chamber between the preceding step and the succeeding step.