Overlay Error Measuring Device, Measuring Method and Optimizing Method

Abstract

The invention belongs to the technical field related to lithography, and discloses an overlay error measurement device and its measurement method and optimization method. The device includes: an illumination system; It includes a polarizer, a first phase retarder, a second phase retarder and a first lens group in sequence; an analyzer arm arranged symmetrically with the polarizer arm along the normal line of the surface of the overlay sample to be measured, and the analyzer arm is arranged along the optical path It includes the second lens group, the third phase retarder, the fourth phase retarder and the polarizer in turn; the detection system arranged on the optical path of the polarizer arm, the detection system converges the beam demodulated by the polarizer arm and sends the beam to A data processing system. The data processing system converts the light beam into a Mueller matrix, and obtains an overlay error according to the Mueller matrix. The overlay marking period of the overlay sample to be tested in the application is not limited, the measurement speed is fast, the measurement result is not disturbed by moving devices, the measurement accuracy is high, the robustness is good, and the application range is wide.

Description

technical field [0001] The invention belongs to the technical field related to photolithography, and more specifically relates to an overlay error measurement device, a measurement method and an optimization method thereof. Background technique [0002] Integrated Circuit (IC) is an indispensable part of modern production and life, photolithography is a key process in the manufacture of integrated circuits, and overlay error (Overlay) is an important parameter in the photolithography process. Overlay error refers to the alignment error between the current layer (the pattern retained on the photoresist after exposure and development) and the reference layer (the existing pattern on the wafer) during exposure, that is, the relative to the design position of the current layer. Offset. Overlay accuracy is one of the three major indicators of lithography machines, and its size has a direct impact on device performance. Excessive overlay errors will lead to short circuits or open...

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Problems solved by technology

[0020] Although this device does not need to limit the period of the overlay mark when measuring the overlay error (using the zero-order diffracted light of the overlay mark, that is, the mirror reflection light to obtain its Mueller matrix, the reflection angle is not affected by the period of the overlay mark. influence), but the traditional Mueller matrix ellipsometer often has moving parts that interfere with the measurement results, and the measurement is time-consuming (usually takes several seconds), so its practical application in the field of overlay error measurement faces the dilemma of speed and accuracy

[0021] In addition, with the continuation of Moore's Law, semiconductor devices continue to develop towards the trend of miniaturization, and the requirements for the size of overlay marks are becoming more and more stringent, which poses a challenge to the existing measurement devices

On the other hand, semiconductor devices are changing from a two-dimensional structure to a three-dimensional structure (for example, the three-dimensional flash memory structure has been stacked to more than a hundred layers). Due to factors such as stress, it is difficult for the real overlay error of the device area to pass through the scribed groove. Accurate characterization of overlay marks in

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