Novel technology of automatic macro inspection for 32-nm node and best focus detection

Abstract

As the semiconductor design rules shrink down, process margins are getting narrower, and thus, it is getting more important than ever to monitor pattern profile and detect minor structure variation. A breakthrough technology has been introduced as a solution to this concern. The new technology converts the fluctuation of polarization ingredient, which is caused by form birefringence, into light intensity variations as an optical image. This technology, which is called Pattern Edge Roughness (PER) inspection mode, is proved to be effective for 55nm production process. We also studied the possibility of the macro inspection method for half pitch 32nm technology node through FDTD method.

Accuracy of focus wedge mark measurement using fitting function for partially coherent illumination

“…Various focus measurement methods based on the evaluation of lithography-processed wafers have been studied. [6][7][8][9][10][11][12][13][14] Phase shift mask technology has been utilized as a method to achieve resolution enhancement and a larger depth of focus. 15,16) Because the periodic line and space (L&S) pattern on the phase shift mask realizes perfect twobeam interference in the case of coherent illumination, we can directly determine the best focus position from the image positional shift.…”

“…Another approach utilizes the diffracted lights from the periodic patterns on the processed wafer. [8][9][10][11][12][13][14] The best focus position can be determined under the practical manufacturing conditions because we only expose the measurement pattern, which has a geometrical scale similar to that of the actual circuit pattern under the actual illumination conditions. In this method, the focus estimation is not directly performed from the observed data.…”

“…In this method, the focus estimation is not directly performed from the observed data. Elaborate post-processing techniques, such as pattern analyzing [8][9][10] or a time-consuming iterative electromagnetic calculation, [11][12][13][14] are required.…”

Theoretical analysis of focus wedge mark for best-focus determination in photolithography

“…A number of researchers have reported various focus measurement methods based on an evaluation of lithographyprocessed wafers. [3][4][5][6][7][8][9][10][11] The big innovation of phase shift mask technology promoted photolithography as a method of achieving resolution enhancement and a larger depth of focus. 12,13) One application of the phase shift mask is to determine the focus shift directly from the image positional shift.…”

“…Another approach utilizes the light diffracted from the measurement pattern on the processed wafer. [5][6][7][8][9][10][11] The diffraction light is sensitive to tiny variations in the focus position when the dimensions of the measurement pattern are close to the resolution limit of the realistic manufacturing exposure process. However, an estimation of the focus requires pattern analyzing software [5][6][7] or an iterative timeconsuming electromagnetic calculation.…”