TWI582428B - Pre-scan based track correction focusing leveling device and method - Google Patents

Description

Track correction focusing adjustment device and method based on pre-scan

The present invention relates to the field of photoetching, and more particularly to a pre-scan based trajectory correction focusing leveling apparatus and method for use in a photoetching machine.

In a projection photolithography apparatus, a cymbal focusing leveling detection device is typically used to achieve measurement of the height and slope of a particular area of the surface of the cymbal. The measuring device requires high precision and does not damage the cymbal during operation. Therefore, the focus measurement of the cymbal must be non-contact measurement. There are three commonly used non-contact focus measurement methods: optical measurement, capacitance measurement, and barometric measurement.

A focus leveling detecting apparatus and method are described in US Pat. No. 4,650,983, in which a scanning mirror is used to modulate a surface containing a measured object (such as a semiconductor substrate or a cymbal) with respect to a focal plane of a photoetching machine projection optical system. The optical signal of the defocus height information, and the optical signal modulated by the scanning mirror is converted into an analog electrical signal containing the information of the defocus height by the photosensitive detector, and finally from the analogy by the phase sensitive demodulation (PSD) circuit. The actual defocus height data is demodulated in the signal. In the triangulation method, the spot incident on the object to be tested is of a certain size and is related to the range of the focus leveling detecting device.

Traditional interferometers are also a non-contact device for measuring small spatial distances. Conventional interferometers generally use a single-color (or narrow-band) light source with a long coherence length, by detecting changes in the position, shape, and distance of the interference fringes. Accurately measure spatial distance. In this measurement method, the spot incident on the object to be measured can be regarded as a point.

In the case of an object such as a cymbal or a glass substrate, there may be periodic grooves on the surface, and the groove is not the position we want to measure. The period in which the grooves appear is generally on the order of millimeters (e.g., 3 mm), and the size of the grooves themselves is on the order of hundreds of microns (which may be 100 μm). This makes it possible for the measuring point to fall within the process trench when the spot is small, causing errors in the measurement. The invention provides a trajectory calibratable focusing and leveling device based on pre-scanning, which pre-scans each batch of objects to be measured, thereby adjusting the measurement trajectory to avoid measuring the position of the groove.

In view of the above problems, the present invention provides a pre-scan based trajectory correction focusing and leveling device, comprising a sensor array and a motion stage for carrying a measured object in a horizontal direction, the measured The object has a pattern extending in a first horizontal direction, the sensor array being arranged substantially in a second horizontal direction perpendicular to the first horizontal direction for sampling a plurality of sampling points of the surface of the object to be measured to obtain The sampling result, the focus leveling device further includes a controller, configured to fit the surface of the object according to the sampling result to obtain a fitting surface, and according to the sampling result and the fitting surface The deviation value ΔH controls the overall fine adjustment of the position of the sensor array in the second horizontal direction.

In view of the above problems, the present invention provides a pre-scan based trajectory correction focusing and leveling device, comprising a sensor array and a motion stage for carrying a measured object in a horizontal direction, the measured The object has a pattern extending in a first horizontal direction, the sensor array being arranged substantially in a second horizontal direction perpendicular to the first horizontal direction for sampling a plurality of sampling points of the surface of the object to be measured to obtain sampling As a result, the focus leveling device further includes a controller for fitting the surface of the object to be obtained according to the sampling result to obtain a fitting surface, and according to the sampling result and the fitting surface The deviation value ΔH controls the sensor in the sensor array that the deviation value ΔH exceeds the critical value to perform position fine adjustment in the second horizontal direction.

Wherein, each of the sensors in the sensor array can be finely adjusted in the second horizontal direction.

Wherein, the distance between adjacent sensors in the sensor array is smaller than the distance between adjacent patterns on the surface of the object to be tested.

The invention also provides a method for performing pre-scanning and trajectory correction by using the above device, comprising: step 1: determining an initial measurement position of the sensor array; and step 2: the sensor array is at the initial measurement position on the object to be tested The surface is measured, the measurement point height value of each sensor in the sensor array is obtained, and the measurement point height value is fitted to obtain a fitting surface; Step 3: calculating the height value of each measurement point and the The deviation value of the fitting surface is ΔH; Step 4: comparing the deviation value ΔH of each corresponding measuring point height value with a height threshold H ₀ , if all the deviation values ΔH are smaller than the height threshold H ₀ Then, go to step eight, otherwise go to step 5; step 5: determine whether the position of the sensor array is finely adjusted is less than the preset maximum fine tuning times, if yes, go to step 6, otherwise go to step 7; step 6: control the sensing The whole of the array is finely adjusted in the second horizontal direction and steps 2 to 4 are repeated; Step 7: selecting the maximum value of the deviation value ΔH measured after multiple position fine adjustment is the most A position corresponding to the position of the sensor array as a sample, and ends; and eight steps: determining the current position of the sensor array of sampling positions, and ends.

The present invention also provides another method for performing pre-scanning and trajectory correction using the above apparatus, comprising: Step 1: determining an initial measurement position of the sensor array; and step 2: the sensor array is measured at the initial measurement position Measuring the surface of the object, obtaining the measured point height value of each sensor in the sensor array and fitting the measuring point height value to obtain a fitting surface; Step 3: calculating the height value of each measuring point and calculating Deviation value ΔH of the joint surface; Step 4: Comparing the deviation value ΔH of the corresponding height value of the measurement point with a height threshold H ₀ , if all the deviation values ΔH are smaller than the height threshold H ₀ , Then enter step eight, otherwise go to step five; step five: determine whether the position of the sensor array is finely adjusted is less than the preset maximum fine-tuning times, if yes, go to step six, otherwise go to step seven; step six: fine-tune the sensor the array deviation values △ H exceeds the height position of the threshold value H ₀ of the sensor in a second horizontal direction of the step and repeat steps two to four; step seven: selecting a plurality of times after the measured position fine adjustment Maximum difference △ H is a minimum in a position corresponding to the position of the sensor array as a sample, and ends; and eight steps: determining the current position of the sensor array of sampling positions, and ends.

Wherein, in step 6, the positions of the sensors in the sensor array can be separately fine-tuned.

In the prior art, for example, triangulation based on luminous flux modulation. The spot size is generally 2~4mm in the non-measurement direction. It is difficult to evade the measured when the spot is large The groove of the surface of the object. With the apparatus and method according to the present invention, the measurement points can be finely adjusted along the non-measurement direction of the workpiece stage, and the retest is performed until a certain requirement is met. This can avoid the possibility that the measuring point falls within the groove to the greatest extent and improve the measurement accuracy.

S1-S9‧‧‧ sensor

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

Figure 1 is a schematic diagram of the cymbal and measuring point array; Figure 2 is a schematic diagram of the scribe groove of the sensor and the measured object; Figure 3 is a schematic view of the measuring and fitting surface; Figure 4 shows a certain A multi-point sampling map of the measuring point in the scribe groove; FIG. 5 is a schematic diagram showing the deviation of each sampling point from the fitting surface; FIG. 6 is a sampling position of the integrated sensor according to the first embodiment of the present invention. Pre-scan and trajectory correction flowchart; FIG. 7 is a schematic diagram of multi-point sampling after sampling position correction of the integrated sensor; FIG. 8 is a sampling of the independent tunable sensor according to the second embodiment of the present invention; Position pre-scan and trajectory correction flowchart; and FIG. 9 is a schematic diagram of multi-point sampling after sampling position correction of the independently adjustable sensor.

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[First Embodiment]

According to the first embodiment of the present invention, the process and the function of the pre-scan are introduced. In this embodiment, the arrangement of the plurality of sensors is integrated, that is, the sensors cannot move with each other, and the variation of the scan track is caused by The exercise station carrying the object to be tested is completed. This can achieve the purpose of pre-scanning and trajectory adjustment without increasing the complexity of the device.

In the present invention, the horizontal direction includes an x direction and a y direction, the x direction and the y direction are perpendicular to each other, and the horizontal motion stage carries the object to be moved in the y direction, and the horizontal motion stage and the sensor avoid the scribe groove in the x direction. Make fine adjustments.

Figure 1 shows a schematic diagram of the cymbal and measuring point array. It can be seen that there are periodic process lines on the surface of the actual object to be tested. During the measurement of the surface of the cymbal by the sensor array, if a sensor measurement spot falls within the scribe groove, the measured value of the point will be significantly different from the measured values of other sensors. After the plane fitting is performed, the residual value of the measured value of the sensor and the fitting surface is significantly larger than that of the other sensors.

FIG. 2 is an enlarged schematic view showing the scribe groove of the sensor and the measured object. In the actual measurement exposure process, the direction in which the scribe groove extends is generally coincident with the direction of movement of the motion table carrying the object to be tested, and this is also premised in the present invention. In the present embodiment, the period of the scribe groove is 3 mm, the scribe groove width and the depth are both 100 μm, and a plurality of sensors are arranged in a row. When the spot of a sensor falls within the scribe groove, the measurement position can be changed to avoid the influence of the scribe groove. Since the spot of the sensor is small, it is also possible to avoid the scheme of the scribe groove by moving the measurement position. In the existing scanning mirror type triangulation method, the size of the spot in the non-measurement direction is generally 2 to 4 mm, which is equivalent to the periodic interval in which the scribe groove appears, thereby moving the sensor to sample on the object to be measured. When the position is in place, it is difficult for the measuring point to avoid the scribe groove. When the spot of the sensor is not measured When the length of the measurement direction is greater than the interval of the scribe groove, the sampling point of the sensor cannot always avoid the scribe groove.

Figure 3 shows the multipoint measurement and fit surface. The focus leveling system obtains the measurement plane according to a multi-point measurement value of the sensor according to a certain fitting algorithm. Due to the difference in the position of the sampling points, the fitting plane also has a certain difference, such as the measuring surface 1 and the measuring surface 2 shown by the broken lines in the figure. The dashed line between the measuring surface 1 and the measuring surface 2 in the figure is the ideal plane, which is the fitting plane of all points in the range of the exposure field of view. In order to more accurately reflect the actual shape of the measured object, the sampling point should be avoided as much as possible in the place where the local surface shape changes greatly. In the measurement of the glass substrate, the scribe groove is a point where the local surface shape changes greatly.

Figure 4 shows a multi-point sampling diagram of a certain measuring point in the scribe groove; Figure 5 shows a deviation of each sampling point and the fitting surface in Figure 4. In Fig. 4, a plurality of sensors S1-S9 are arranged in a row, and a plurality of height values of the respective sensors to the surface of the object to be measured can be simultaneously measured. The spot of the sensor S8 is just inside the groove. When the horizontal moving table carries the object to be moved in the y direction, the sensor S8 always measures the bottom of the groove. Calculating the deviation between each sampling point and the fitting plane, it can be found that the measured deviation value ΔH of S8 is significantly larger. According to the actual situation, a height threshold H ₀ can be set. When the deviation value ΔH of a sampling point to the fitting surface exceeds the critical value, the sampling point of the sensor is considered to be the groove of the object to be tested. . At this time, the object to be measured can be finely adjusted in the x-direction (or negative direction) by the horizontal motion stage.

Figure 6 shows the sampling position pre-scan and trajectory correction flowchart of the integrated sensor. The method includes the following steps: Step 1: determining an initial measurement position; and step 2: performing measurement at the initial measurement position by using a sensor array to obtain a measurement point height value of each sensor and obtaining a fitting by fitting Step 3: Calculate the deviation value ΔH between the height value of each measuring point and the fitting surface; Step 4: Compare the deviation value ΔH of the height value of each measuring point with the height threshold H ₀ , if all the deviation values If △H is less than the height threshold H ₀ , proceed to step eight, otherwise go to step 5; step 5: judge the ith fine adjustment (i=1, 2, 3, ...) entering the sensor; step 6: Comparing i with a preset maximum adjustment number I. If less than 1, fine-tuning the position of the motion stage in the x direction causes the entire sensor array to move in the x direction, and repeats steps 2 to 6, otherwise the steps are entered. Step 7: Select the position where the minimum value of the maximum value of the deviation value ΔH in the multiple adjustment is the sampling position, and end; and Step 8: Determine the current position as the sampling position, and end.

In step four, when the deviation value ΔH of a certain sampling point to the fitting surface exceeds a critical value, it is considered that the sampling point of the sensor corresponds to the groove of the object to be tested. When the maximum deviation value △H<H ₀ , it means that all the measurement points are not in the groove of the object to be tested, and the test can be performed at this position. When the maximum deviation △ H> H _0, it indicates that there are measurement points within the trenches, the need to adjust the x-direction movement stage position until the maximum deviation △ H <far H _0. Considering some actual conditions, such as the particularity of the shape and the rationality of the selection of the critical value, the maximum deviation value △H<H ₀ cannot be satisfied after repeated fine adjustment of the position. At this time, in all the position adjustments, the position corresponding to the smallest one of the maximum deviation values ΔH is selected as the measurement position for measurement.

FIG. 7 is a schematic diagram of multi-point sampling after performing the above sampling position correction. In this embodiment, the overall measurement position of the sensor is adjusted.

[Second embodiment]

A pre-scanning process of the independently adjustable sensor according to the second embodiment of the present invention is different from the first embodiment in that the measurement position of any of the sensors in the horizontal direction in the pre-scanning process in this embodiment is It is adjustable, that is, the variation of the scan trajectory is accomplished by independent adjustment of the horizontal position of several sensors themselves. This increases the complexity of the device, but can be adjusted and circumvented on the scanning trajectory in a specific shape such as the groove position.

Figure 8 shows the sampling position pre-scan and trajectory correction flowchart for the independently adjustable sensor. The method includes the following steps: Step 1: Determine an initial measurement position; Step 2: Perform measurement at the initial measurement position by using a sensor array to obtain a measurement point height value of each sensor and obtain a simulation by fitting Face combination; Step 3: Calculate the deviation value ΔH between the height value of each measurement point and the fitting surface; Step 4: Compare the deviation value ΔH of the height value of each measurement point with the height threshold H ₀ , if all deviations If the value ΔH is less than the height threshold H ₀ , proceed to step eight, otherwise proceed to step five; step five: determine the ith fine adjustment (i=1, 2, 3, ...) entering the sensor; step six : comparing i with the preset maximum adjustment number I, if less than I, fine-tuning the position of the sensor corresponding to the critical value of the measured value ΔH in the x direction in the sensor array, and repeating step two to Step 6 otherwise, go to step 7; Step 7: Select the position where the minimum value of the maximum value of the deviation value ΔH is adjusted as the sampling position and end; and Step 8: Determine the current position as the sampling position And ended.

In step four, when the deviation value ΔH of a certain sampling point to the fitting surface exceeds a critical value, the sampling point of the sensor is considered to be a groove of the object to be tested. When the maximum deviation value △H<H ₀ , it means that all the measurement points are not in the groove of the object to be tested, and the test can be performed at this position. When there is a deviation value ΔH>H ₀ , it indicates that there is a measurement point in the groove, and it is necessary to adjust the position of the sensor corresponding to the x direction of the measurement point until the deviation value ΔH<H ₀ . Considering some actual conditions, such as the particularity of the shape and the rationality of the selection of the critical value, the deviation value △H<H ₀ cannot be satisfied after repeated fine adjustment of the position. At this time, in all the position adjustments, the position corresponding to the smallest deviation value ΔH is selected as the measurement position for measurement.

FIG. 9 is a schematic diagram of multi-point sampling after sampling position correction of the independently adjustable sensor. In this embodiment, only the measurement position of the sensor S8 is adjusted.

The description of the present invention is only a preferred embodiment of the present invention, and the above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit the present invention. Any technical solution that can be obtained by a person skilled in the art according to the idea of the present invention by logic analysis, reasoning or limited experimentation should be within the scope of the present invention.

Claims (7)

A pre-scan based trajectory correction focusing leveling device includes a sensor array and a motion stage for carrying a test object moving in a horizontal direction, the measured object having a first horizontal direction An extended pattern, the sensor array is arranged in a second horizontal direction perpendicular to the first horizontal direction for sampling a plurality of sampling points of the surface of the object to be tested to obtain a sampling result, the focusing adjustment The leveling device further includes a controller for fitting the surface of the object to be tested according to the sampling result to obtain a fitting surface, and controlling the deviation value ΔH according to the sampling result and the fitting surface The entirety of the sensor array is positionally fine tuned in the second horizontal direction. A pre-scan based trajectory correction focusing leveling device includes a sensor array and a motion stage for carrying a test object moving in a horizontal direction, the measured object having a first horizontal direction An extended pattern, the sensor array is arranged in a second horizontal direction perpendicular to the first horizontal direction for sampling a plurality of sampling points of the surface of the object to be measured to obtain a sampling result, and the focusing is leveled The device further includes a controller for fitting the surface of the object to be obtained according to the sampling result to obtain a fitting surface, and controlling the deviation value ΔH according to the sampling result and the fitting surface The sensor in the sensor array in which the deviation value ΔH exceeds a threshold value is positionally fine-tuned in the second horizontal direction. The device of claim 2, wherein each of the sensors in the array of sensors is positionally fine tunable in a second horizontal direction. The apparatus of any one of claims 1 to 3, wherein a distance between adjacent sensors in the sensor array is less than a distance between adjacent patterns on a surface of the object to be tested. A method for performing pre-scan and trajectory correction by using the device of claim 1, comprising the following steps: Step 1: determining an initial measurement position of a sensor array; and step 2: locating the sensor array at the initial measurement position Measuring the surface of the object to be measured, obtaining a measurement point height value of each sensor in the sensor array, and fitting the measurement point height value to obtain a fitting surface; Step 3: calculating each measurement a deviation value ΔH between the point height value and the fitting surface; Step 4: comparing the deviation value ΔH of each corresponding measurement point height value with a height threshold H ₀ , if all deviation values ΔH are smaller than The height threshold H ₀ is then entered in step eight, otherwise step 5 is entered; step 5: determining whether the position of the sensor array is finely adjusted is less than a preset maximum number of fine adjustments, and if yes, proceeding to step six, otherwise proceeding to step 7; Step 6: Control the whole of the sensor array to perform position fine adjustment in the second horizontal direction and repeat steps 2 to 4; Step 7: select the deviation value ΔH measured after multiple position fine adjustments The position of the sensor array corresponding to the smallest one of the maximum values is taken as the sampling position, and ends; Step 8: determining that the current position of the sensor array is the sampling position, and ending. A method for performing pre-scan and trajectory correction by using the device of claim 2, comprising the following steps: Step 1: determining an initial measurement position of a sensor array; and step 2: locating the sensor array at the initial measurement position Measuring the surface of the measured object to obtain a measured point height value of each sensor in the sensor array and fitting the measured point height value to obtain a fitting surface; Step 3: calculating each measuring point a deviation value ΔH between the height value and the fitting surface; Step 4: comparing the deviation value ΔH of the corresponding height value of the measurement point with a height threshold H ₀ , if all the deviation values ΔH are smaller than the height If the critical value H ₀ is reached, go to step 8. Otherwise, go to step 5. Step 5: Determine whether the position of the sensor array is less than a preset maximum number of fine adjustments. If yes, go to step 6. Otherwise, go to step 7; : fine-tuning the sensor array the deviation △ H exceeds the height position of the threshold value H ₀ of the sensor in a second horizontal direction of the step and repeat steps two to four; step seven: selecting multiple positions The position of the sensor array corresponding to the smallest one of the maximum values of the measured deviation values ΔH is taken as the sampling position, and ends; Step 8: determining the current position of the sensor array as the sampling position And ended. The method of claim 6, wherein in step 6, the positions of the sensors in the sensor array are individually fine-tuned.