CN-122029487-A - Overlay measurement device, focus control method for an overlay measurement device for tool-induced displacement measurement, and focus control program for an overlay measurement device for tool-induced displacement measurement

CN122029487ACN 122029487 ACN122029487 ACN 122029487ACN-122029487-A

Abstract

The invention provides a focus control method of an overlay measurement device, which is used for tool induced displacement measurement, and comprises the steps of acquiring a first signal which is a signal from an automatic focusing device when focusing on a corresponding point according to each point of a reference field of a reference wafer in an unrotated state, acquiring a second signal which is a signal from the automatic focusing device when focusing on the corresponding point according to each point of the reference field after rotating the reference wafer by 180 degrees, matching and storing the first signal and the second signal with the corresponding point, positioning a measurement object point of a measurement object wafer in a field of view of the overlay measurement device, and focusing according to the first signal matched with the measurement object point when the measurement object wafer is in the unrotated state, and focusing according to the second signal matched with the measurement object point when the measurement object wafer is in a 180-degree rotating state.

Inventors

Mou Xiuyan
Gao Zhengshan
Cui shengrun
AN SHIXUAN

Assignees

奥路丝科技有限公司

Dates

Publication Date: 20260512
Application Date: 20240729
Priority Date: 20230925

Claims (8)

1. A focus control method of an overlay measurement apparatus for tool-induced displacement measurement, the focus control method of the overlay measurement apparatus comprising: A step of acquiring a first signal as a signal from an automatic focusing device when focusing on a corresponding point, for each point of a reference field of a reference wafer in an unrotated state, wherein illumination of the automatic focusing device is illumination having a longer length deviated from an overlay mark formed on the point; a step of acquiring a second signal, which is a signal from the automatic focusing device when focusing on a corresponding point, for each point of the reference field after rotating the reference wafer by 180 degrees, wherein illumination of the automatic focusing device is illumination that is longer than a length of an overlay mark formed on the point; matching and storing the first signal and the second signal with corresponding point positions; a step of locating the measurement target point of the measurement target wafer in the field of view of the overlay measurement apparatus, and Focusing according to the first signal matched with the point position of the measuring object when the measuring object wafer is in an unrotated state, and focusing according to the second signal matched with the point position of the measuring object when the measuring object wafer is in a 180-degree rotation state.
2. The method for controlling a focus of an overlay measurement apparatus according to claim 1, The autofocus device is a phase difference detection autofocus system, and the first signal and the second signal are phase difference based signals.
3. The method for controlling a focus of an overlay measurement apparatus according to claim 1, The measurement target point location is a point location of the reference field of the reference wafer or a field different from the reference field.
4. The method for controlling a focus of an overlay measurement apparatus according to claim 1, The measurement target wafer is the reference wafer or another wafer belonging to the same lot as the reference wafer.
5. The method for controlling a focus of an overlay measurement apparatus according to claim 1, And confirming whether the wafer to be measured rotates or not according to the position of the flat area or the notch of the wafer.
6. The method for controlling a focus of an overlay measurement apparatus according to claim 1, The first signal matching the measurement object point location is a first signal acquired at a point location within the reference field that is the same as a position within the field of the measurement object point location.
7. An overlay measurement apparatus, comprising: an objective lens; a lens focus actuator configured to move the objective lens to adjust a distance between a wafer and the objective lens; an auto-focusing device outputting a signal corresponding to a distance between the objective lens and the wafer, and A controller communicably coupled to the lens focus actuator and the autofocus device, The controller includes a memory storing instructions and a processor configured to execute the instructions, the instructions cause the processor to perform the steps of: a step of acquiring a first signal as a signal from the automatic focusing device when focusing on a corresponding point, for each point of a reference field of a reference wafer in an unrotated state, wherein illumination of the automatic focusing device is illumination having a longer length deviated from an overlay mark formed on the point; a step of acquiring a second signal, which is a signal from the automatic focusing device when focusing on a corresponding point, for each point of the reference field after rotating the reference wafer by 180 degrees, wherein illumination of the automatic focusing device is illumination that is longer than a length of an overlay mark formed on the point; matching and storing the first signal and the second signal with corresponding point positions; a step of locating the measurement target point of the measurement target wafer in the field of view of the overlay measurement apparatus, and And moving the objective lens according to the first signal matched with the point position of the measuring object to focus when the wafer of the measuring object is in an unrotated state, and moving the objective lens according to the second signal matched with the point position of the measuring object to focus when the wafer of the measuring object is in a 180-degree rotation state.
8. A program for controlling a focus of an overlay measurement apparatus, which is stored in a storage medium for executing a method of controlling a focus of an overlay measurement apparatus using a computing apparatus, the program for controlling a focus of an overlay measurement apparatus characterized by causing the computing apparatus to execute the steps of: A step of acquiring a first signal as a signal from an automatic focusing device when focusing on a corresponding point, for each point of a reference field of a reference wafer in an unrotated state, wherein illumination of the automatic focusing device is illumination having a longer length deviated from an overlay mark formed on the point; a step of acquiring a second signal, which is a signal from the automatic focusing device when focusing on a corresponding point, for each point of the reference field after rotating the reference wafer by 180 degrees, wherein illumination of the automatic focusing device is illumination that is longer than a length of an overlay mark formed on the point; matching and storing the first signal and the second signal with corresponding point positions; a step of locating the measurement target point of the measurement target wafer in the field of view of the overlay measurement apparatus, and Focusing according to the first signal matched with the point position of the measuring object when the measuring object wafer is in an unrotated state, and focusing according to the second signal matched with the point position of the measuring object when the measuring object wafer is in a 180-degree rotation state.

Description

Overlay measurement device, focus control method for an overlay measurement device for tool-induced displacement measurement, and focus control program for an overlay measurement device for tool-induced displacement measurement Technical Field The present invention relates to an alignment measurement device, a focus control method of the alignment measurement device for tool-induced displacement measurement, and a focus control program of the alignment measurement device for tool-induced displacement measurement. Background A plurality of pattern layers are sequentially formed on a semiconductor substrate. Further, by double patterning or the like, a circuit of one layer is also formed by dividing it into two patterns. The desired semiconductor device can be manufactured only when these pattern layers or a plurality of patterns of one layer are precisely formed at predetermined positions. Therefore, in order to confirm whether the pattern layer is accurately aligned, an overlay mark formed simultaneously with the pattern layer is used. The method of measuring overlay using overlay marks is as follows. First, a structure as a part of the overlay mark is formed on the pattern layer formed in the previous step, for example, the etching step, simultaneously with the formation of the pattern layer. Then, in the latter process, for example, a photolithography process, the remaining structure of the overlay mark is formed on the photoresist. Then, an overlay structure of the pattern layer formed in the previous process (an image is obtained through the photoresist layer) and an image of the overlay structure of the photoresist layer are obtained by an overlay measurement device, and a displacement value between centers of these images is measured, thereby measuring an overlay error value. More specifically, japanese laid-open patent 2020-112807 discloses a method of capturing an image of an overlay mark formed on a substrate, selecting a plurality of working areas in the captured image, forming a signal with information for each selected working area, and comparing the signals, thereby determining the relative misalignment between different layers or different patterns. Fig. 1 is a plan view of an example of an overlay mark. The overlay mark 1 shown in fig. 1 comprises four Working Zone (Working Zone) groups 4, 5, 6, 7. In addition, each work area group 4, 5, 6, 7 comprises two work areas arranged diagonally to each other. Each work area group 4, 5, 6, 7 is used to measure overlay error in the X-axis or Y-axis direction of the pattern layer formed with the corresponding work area group. In order to prevent the occurrence of the interference phenomenon, the structure 2 formed with the first pattern layer and the structure 3 formed with the second pattern layer are arranged so as not to overlap each other. Each working area includes a stripe arranged at a constant pitch from the center of the overlay mark 1 to the outline of the overlay mark 1. Thus, with the overlay measurement apparatus, the periodic signals as shown in fig. 2 can be acquired from the two working areas belonging to the working area groups 4, 5, 6, 7, respectively. The diagram of fig. 2 can be obtained, for example, from the partial region 8 selected in fig. 1. In the graph of fig. 2, the peak appears at the portion where the bar is arranged. The conventional overlay mark 1 is configured by the stripe periodicity, and the acquired signal is periodic. In addition, overlay error is measured by performing correlation analysis (correlation) on two periodic signals acquired from the two selected regions 8, 8'. Such overlay error measurement requires high quality overlay measurement apparatus in order to meet the demands of the increased lithographic process. In measuring overlay errors, defects (e.g., aberrations) in the optical elements that make up the overlay measurement device may cause Tool-induced Shift (TIS). The optical imperfections of such overlay measurement devices may result in a displacement between the actual overlay error and the measured overlay error. Tool-induced displacement measurements require repeated overlay error measurements in the non-rotated state and 180 degree rotated state of the wafer. The tool-induced displacement may be the sum of the overlay error value in the non-rotated state of the wafer and the overlay error value in the 180 degree rotated state divided by 2. In an ideal case, the tool induced displacement is zero because the overlay error value in the non-rotated state is equal in magnitude and opposite in sign to the overlay error value in the 180 degree rotated state. Overlay error measurements for tool-induced displacement measurements are made at a plurality of points (overlay marks) located within the reference field. Fig. 3 is a diagram showing an example of a wafer. As shown in fig. 3, the semiconductor wafer includes a plurality of fields F. There are a plurality of (4 in fig. 3) points S 1、S2、S3、S4 in one