CN105116691B - Method for determining optimal height of detector of workpiece table of photoetching machine - Google Patents

Abstract

The invention discloses a method for determining the optimal height of a workpiece table detector of a lithography machine. The workpiece table carries a photodetector to detect the light intensity along the direction of the optical axis at a specific light intensity position, and iteratively finds the minimum value of the light intensity. The corresponding position is the optimum height of the detector. The method controls the sampling interval of the workpiece table along the optical axis, so that the measurement accuracy can reach the micron level, and the measurement method is simple and fast, and the measurement accuracy is high.

Description

A Method for Determining Optimum Height of Workpiece Table Detector of Photolithography Machine

technical field

The invention relates to the technical field of semiconductors, in particular to a method for determining the optimum height of a workpiece table detector of a lithography machine.

Background technique

In the exposure system of a lithography machine, the characteristics of the system, such as stray light, field size, and uniformity of the field of view, have an impact on the imaging quality and resolution of the lithography machine, and testing and evaluation are required. In order to ensure measurement accuracy, Measurements need to be made near the best focal plane on the mask surface or silicon wafer surface, so it is necessary to determine the optimum detection height of the photodetector on the mask surface or silicon wafer surface.

Patent CN 102402139 A provides a method for determining the optimum height of the photoelectric sensor of the workpiece table of a lithography machine, and compares the advantages and disadvantages of different methods for determining the optimum height, and analyzes the shortcomings of the method given in the patent US005650840A. The main principle of the method proposed in this patent is to scan in the horizontal direction at different positions in the vertical direction, calculate the coordinates at a specific light intensity, draw the curve between the vertical position and the coordinates, and perform data processing to obtain the photoelectric sensor at the extreme value The position is the optimal height of the photoelectric sensor. In this method, the shorter the sampling interval in the vertical direction, the higher the measurement resolution will be, so the number of scans in the horizontal direction will also increase, and each horizontal scan data needs to be processed, the measurement time is long, and the resolution is also high. very limited.

Contents of the invention

The purpose of the present invention is: to overcome the defects of the prior art, the present invention provides a method for determining the optimal height of the photoelectric detector of the photoetching machine workpiece table, the method also performs light intensity scanning in the vertical and horizontal directions in the measurement light field plane , the difference from the prior art is that the present invention first scans the light intensity in the horizontal direction to find the position coordinates of a specific light intensity, and records the light intensity and detector coordinates in the vertical direction at this position, and processes the result to obtain The optimal height of the detector can be obtained by performing two or three iterative measurements on the position coordinates of the detector with a minimum value. The measurement resolution of this method can reach the order of microns, and the sampling interval in the vertical direction is reduced The number of measurements will be increased, and it is a high-precision, simple and fast method for determining the optimum height of the photodetector of the workpiece table of the lithography machine.

The technical solution adopted in the present invention is: a method for determining the optimum height of the workpiece table detector of a lithography machine, and the realization process includes steps:

Step (1): The workpiece table carries the photodetector and moves to a certain position z0 in the vertical direction;

Step (2): The workpiece table carries the photodetector to scan the light intensity along the horizontal direction, and records the light intensity information at different positions during the scanning process;

Step (3): draw the relative light intensity-horizontal position curve I(x,z0), and find the position x0 at a certain light intensity;

Step (4): Move the photodetector to the horizontal position x0 obtained in step (3), the workpiece table carries the photodetector to scan the light intensity along the vertical direction, and record the position of the detector at the same time;

Step (5): draw the light intensity-vertical position curve I(x0,z), and find the position z1 at the lowest light intensity;

Step (6): moving the photodetector to the vertical position z1 obtained in step (5);

Step (7): Determine whether the difference between the vertical position obtained in step (5) and the vertical position obtained the previous time is less than a specific error value, and then end the measurement when it is satisfied. The vertical position obtained in the last measurement is the best position, and if it is not satisfied It is required to continue to repeat steps (2) to (6).

Wherein, the optimal position determination method is obtained through an iterative method, so the difference in the initial vertical position in step (1) does not affect the final measurement result.

Wherein, the specific light intensity in step (3) is 10% to 50% of the relative light intensity. In a measurement process, the specific light intensity selected for each iteration is the same, and the specific light intensity can be changed for multiple optimal position measurements. , effectively improving the measurement accuracy.

Wherein, the method for finding the minimum light intensity in step (5) is a curve fitting method.

Wherein, the specific error value in step (7) is an arbitrary value set according to actual application conditions.

The advantage of the present invention compared with prior art is:

(1), the present invention has high measurement precision, through continuous scanning in the vertical direction, the measurement precision can reach micron or even submicron level;

(2) The measurement speed of the present invention is fast, and the determination of the optimum height is realized through iterative scanning in the vertical direction, the number of iterations is small, and the data processing method is simple and quick.

Description of drawings

Fig. 1 is the schematic diagram of the optimal height measuring device of the photoetching machine workpiece table photodetector of the present invention;

Fig. 2 is the scanning light intensity curve of photodetector horizontal direction of the present invention;

Fig. 3 is the photodetector of the present invention along the vertical direction scanning light intensity schematic diagram;

Fig. 4 is that the photodetector of the present invention scans the light intensity curve along the vertical direction;

Fig. 5 is a flow chart of the optimal height measurement of the photodetector of the workpiece stage of the lithography machine according to the present invention.

detailed description

A method for determining the optimal height of the workpiece stage detector of a lithography machine according to the present invention will be further described in detail below.

Fig. 1 is a schematic diagram of an optimal height measuring device for photodetectors on workpiece tables of lithography machines. The exposure system of the lithography machine is provided with an illumination system, a mask 1 with a light-transmitting area, a projection objective lens 2 and a workpiece table 3 in sequence along the optical axis. The illumination system illuminates the mask 1, and images the image on the workpiece table through the projection objective lens 2. The photodetector 4 is installed on the workpiece table. The workpiece table can perform three-dimensional scanning, and drives the photodetector to detect the transmitted light intensity signal.

For the device shown in Fig. 1, the method of applying the present invention to determine the optimum height of photodetector is as follows:

Step (1): The workpiece table carries the photodetector and moves to a certain position z0 in the vertical direction;

Step (2): The workpiece table carries the photodetector to scan the light intensity along the horizontal direction, and records the light intensity information at different positions during the scanning process;

Step (3): Draw the relative light intensity-horizontal position curve I(x, z0), and find the position x0 at a certain light intensity; for example, the 10% light intensity position shown in Figure 2;

Step (4): Move the photodetector to the horizontal position x0 obtained in step (3), and the workpiece table carries the photodetector to scan the light intensity along the vertical direction, as shown in Figure 3, and record the position of the detector at the same time;

Step (5): Draw the light intensity-vertical position curve I(x0,z), and find the position z1 at the lowest light intensity, as shown in Figure 4;

Step (6): moving the photodetector to the vertical position z1 obtained in step (5);

Step (7): Determine whether the difference between the vertical position obtained in step (5) and the vertical position obtained last time is less than a specific error value, such as 0.5mm, and end the cycle when it is satisfied, and the vertical position obtained in the last measurement is the best If the location does not meet the requirements, continue to repeat steps (2) to (6). The measurement flow chart of this method is shown in Figure 5.

Claims (4)

1. A method for determining the optimum height of a lithography machine workpiece table detector, is characterized in that: the method comprises the steps: Step (1): The workpiece table carries the photodetector and moves to a certain position z0 in the vertical direction; Step (2): The workpiece platform carries a photodetector to scan the light intensity along the horizontal direction, and records the light intensity information at different positions during the scanning process; Step (3): draw the relative light intensity-horizontal position curve I(x, z0), and find the position x0 of a certain light intensity; In the process, the specific light intensity selected for each iteration is the same, and the specific light intensity is changed to perform multiple optimal position measurements, which effectively improves the measurement accuracy; step (4): move the photodetector to the position obtained in step (3). At the horizontal position x0, the workpiece table carries the photodetector to scan the light intensity along the vertical direction, and record the position of the detector at the same time; Step (5): draw the light intensity-vertical position curve I(x0,z), and find the position z1 at the lowest light intensity; Step (6): moving the photodetector to the vertical position z1 obtained in step (5); Step (7): Determine whether the difference between the vertical position obtained in step (5) and the vertical position obtained the previous time is less than a specific error value, and then end the measurement when it is satisfied. The vertical position obtained in the last measurement is the best position, and if it is not satisfied It is required to continue to repeat steps (2) to (6). 2. The method for determining the optimal height of the photolithography machine workpiece table detector according to claim 1, characterized in that: the optimal position determination method is obtained by an iterative method, so the initial vertical position in step (1) is different Does not affect the final measurement result. 3. The method for determining the optimal height of the photolithography machine workpiece stage detector according to claim 1, characterized in that: the method for calculating the minimum light intensity in step (5) is a curve fitting method. 4. The method for determining the optimum height of the workpiece stage detector of a lithography machine according to claim 1, characterized in that: the specific error value in step (7) is an arbitrary value set according to actual application conditions.