| 摘要 |
<p>A method of detecting focus spots (10) during the exposure of semiconductor wafers (1) uses adjacent surface tilt (5) measurements of exposure fields (2) by means of level sensors (5), or focus channels. Adjacent measurements are compared and an error signal is generated in response to a tilt difference exceeding a threshold value. In response to the error signal (50), a data string is generated comprising the wafer identification, the exposure field position and, preferably, a layer currently structured. In a layer-to-layer comparison, a focus spot currently being detected and quickly identified with a possible occurrence of the same wafer and exposure field in a previous layer. A floodlight inspection and rework operation can then be skipped and, alternatively, the occurrence of a new focus spot (10) can be utilised in advanced process control, for e. g. terminating the exposure step of following wafers for investigating the root cause, e. g. contaminating particle problems. <IMAGE></p> |
