CN108345177B - Device and method for measuring lamination error - Google Patents

Abstract

The present disclosure provides a stacking error measurement device and method. The device includes a light source, an optical system, an objective lens and a detector. The light source is used to generate measurement light. The optical system is used to guide the measurement light into the objective lens. The objective lens is used to guide the measurement light onto a stacking mark, and at the same time collect the positive main pole diffraction light and the negative main pole diffraction light diffracted from the stacking mark onto the pupil plane of the objective lens. The detector is arranged on the pupil plane of the objective lens, and is used to detect the light intensity distribution of the positive and negative main pole diffraction lights, and obtain a stacking error signal of the stacking mark by subtracting the light intensity distribution of the positive and negative main pole diffraction lights. Among them, the optical system includes an aperture, which has at least one light-transmitting area, and its position, size and/or shape are adjustable according to the position of the noise in the stacking error signal. The stacking error measurement device provided by the present disclosure can improve the quality of the stacking error signal and improve the accuracy of stacking error detection.

Description

Lamination error measuring device and method

technical field

Embodiments of the present disclosure relate to a semiconductor manufacturing technology, and in particular, to a device and method for measuring an overlay error.

Background technique

In semiconductor manufacturing, the lithography process can be said to be a very critical step, which is directly related to the limit of the minimum feature size. Alignment and exposure are the most important techniques in the lithography process, where the purpose of alignment is to enable the correct transfer of the mask pattern to the photoresist layer, because semiconductor components (such as IC dies) are composed of many structures The layers are stacked, so if the exposure position is not aligned correctly, the patterns between the layers cannot closely match the pattern of the original circuit design, resulting in defects such as short circuits, open circuits and poor electrical properties, resulting in lower product yields , and increase production costs.

The error in the overlay position of the pattern between the aforementioned layers is also called an overlay error. As the integration of components becomes higher and higher, the number and complexity of lithography continue to increase, and the tolerance of stacking errors is significantly reduced, so the accuracy requirements for measuring stacking errors become more stringent. Due to the limitation of the imaging resolution limit, the traditional image-based overlay (IBO) technology based on imaging and image recognition has gradually been unable to meet the accuracy requirements of the current industry for measuring the overlay error. Diffraction-based overlay (DBO for short) is becoming the main method for measuring overlay errors.

Although the current DBO measurement technology has met the general measurement accuracy requirements, it still cannot meet all aspects. Therefore, there is a need to provide an improved solution for a diffractive layered error measurement device and method.

SUMMARY OF THE INVENTION

Some embodiments of the present disclosure provide a stacking error measurement device, including: an objective lens; a light source for generating a measurement light; an optical system for guiding the measurement light into an objective lens, and the objective lens is used for measuring the light Guided to the layer-by-layer mark, while collecting the positive main-pole diffracted light and the negative main-pole diffracted light from the layer-by-layer mark to a pupil surface of the objective lens; and a detector arranged on the pupil of the objective lens On the surface, it is used to detect the light intensity distribution of the above-mentioned positive and negative main pole diffracted light, and use the positive and negative main pole diffracted light to subtract the light intensity distribution to obtain the layered error signal of the layered mark; wherein, The aforementioned optical system includes an aperture having at least one light-transmitting region, and the position, size and/or shape of the light-transmitting region can be adjusted according to the position of noise in the stacking error signal.

Some embodiments of the present disclosure provide a stacking error measuring apparatus, including: an optical system for guiding a measurement light from a light source into an objective lens for guiding the measurement light to a stacking mark , simultaneously collect the positive main pole diffracted light and the negative main pole diffracted light diffracted from the laminated mark, wherein the optical system includes an aperture, which has at least one light-transmitting area and at least one non-transmitting area; and a detector, It is used for subtracting the light intensity distribution of the aforementioned positive main pole diffracted light and negative main pole diffracted light to obtain a stacking error signal of the stacking mark, and adjusting the aforementioned at least one of the aperture according to the position of the noise in the stacking error signal. The position, size and/or shape of a light-transmitting area and at least one non-light-transmitting area.

Some embodiments of the present disclosure provide a method for measuring a stacking error, including: emitting a measuring light through a light source; guiding the measuring light into an objective lens through an optical system; and guiding the measuring light to a stacked mark through the objective lens and collect the diffracted light of the positive main pole and the diffracted light of the negative main pole from the layered mark to a pupil surface of the objective lens; detect the light intensity distribution of the above-mentioned positive and negative main pole diffracted light by a detector, And use the light intensity distributions of the positive and negative main pole diffracted lights to be subtracted to obtain a reference stacking error signal of the stacking mark; according to the position of the noise in the reference stacking error signal, the detector modulates the optical The position, size and/or shape of at least one light-transmitting area of an aperture in the system; and detecting the light intensity distribution of the above-mentioned positive and negative main pole diffracted light by a detector, and using the said positive and negative main pole diffracted light The light intensity distributions are subtracted to obtain a formal stacking error signal of the stacking marks.

Description of drawings

FIG. 1 shows a schematic structural diagram of a layer-by-layer error detection apparatus according to some embodiments.

FIG. 2 shows a schematic cross-sectional structure diagram of the stacked marker in FIG. 1 .

FIG. 3 shows a schematic front view of the aperture in FIG. 1 .

FIG. 4 shows a light intensity distribution diagram of positive or negative 1st order diffracted light detected by the detector in FIG. 1 .

5 shows a graph of stacked error signals obtained by subtracting the light intensity distributions of positive and negative first-order diffracted light according to some embodiments.

FIG. 6 shows a schematic diagram of using an active matrix liquid crystal module as an aperture according to some embodiments.

7A and 7B are schematic diagrams showing the structure of each liquid crystal cell of the active matrix liquid crystal module in FIG. 6 , and a schematic diagram of the working principle of allowing or not allowing light to pass therethrough.

8 shows a block diagram of a control system consisting of a detector and an aperture (active matrix liquid crystal module) according to some embodiments.

FIG. 9 shows a schematic structural diagram of each micro-lens unit when the micro-lens array module is used as the aperture according to some embodiments.

10 shows a flowchart of a method for stacking error detection according to some embodiments.

Description of reference numbers:

10～Lamination error detection device;

11 ~ light source;

12～Optical system;

13~ collimating lens;

14～Filter;

15～Aperture;

15A～Transparent part;

15B ~ peripheral part;

16～polarizer;

17~ the first lens;

18～Field diaphragm;

19 ~ the second lens;

20～spectroscope;

21～objective lens;

22～Lens group;

23～Detector;

23A～processing unit;

71 ~ the first polarizer;

72～the first electrode;

72A～alignment film;

73 ~ liquid crystal layer;

74 ~ the second electrode;

74A～alignment film;

75～Second polarizer;

80～Location data;

91～Micro lens;

92 ~ support piece;

93～Control circuit;

151～Panel unit;

152～sequence controller;

153～scanning drive unit;

154～data drive unit;

200～Lamination error detection method;

201～206～steps;

B ~ test light;

B1～light;

d～position error;

D ₁ ～Dn～data drive signal;

G1 ~ lower grating structure;

G2 ~ upper grating structure;

L1~front layer;

L2 ~ on the floor;

L3～intermediate material layer;

M～layer mark;

R1～transparent area;

R2～non-transparent area;

S ~ base material;

S ₁ ～Sm～scanning drive signal;

Sd～data control signal;

Ss ~ scan control signal;

T～tilt angle;

U ~ liquid crystal cell;

U'～micro lens unit;

V～Voltage.

Detailed ways

The following disclosure provides many different embodiments or examples for implementing different features of the present disclosure. The following disclosure describes specific examples of various components and their arrangements to simplify the description. Of course, these specific examples are not intended to be limiting. For example, if the embodiment describes that a first feature is formed on or above a second feature, it means that it may include the situation that the first feature and the second feature are in direct contact, and may also include additional features Formed between the first feature and the second feature so that the first feature and the second feature are not in direct contact.

Spatially relative terms such as "below," "below," "lower," "above," "upper," and similar terms are used hereinafter to facilitate description of an element in an illustration The relationship between a feature or feature and another element or feature(s). In addition to the orientation shown in the figures, these spatially relative terms are also intended to mean that the devices in the figures may be used or operated in different orientations.

The same element numbers and/or words may be repeatedly used in different embodiments below, and these repetitions are for the purpose of simplicity and clarity, and are not intended to limit the specific relationship between the different embodiments and/or structures discussed.

Terms such as first and second used in the following are only for the purpose of clearly explaining them, and are not used to correspond to and limit the claims. In addition, the terms such as the first feature and the second feature are not limited to the same or different features.

In the drawings, the shape or thickness of structures may be exaggerated for simplicity or ease of representation. It must be understood that elements not specifically described or illustrated may exist in various forms well known to those skilled in the art.

Please refer to FIG. 1 , which shows a schematic structural diagram of a layer-by-layer error detection apparatus 10 according to some embodiments of the present disclosure. It should be noted first that the stacking error detecting device 10 is a diffraction-based stacking error measuring device, which is used for detecting the error in the pattern overlay position between the layers of the semiconductor element. For example, when the uppermost material layer (also referred to as the current layer) on a semiconductor substrate (such as a silicon wafer) is subjected to, for example, a lithography process, the stacking error detection device 10 can pass diffracted light Detect at least one overlay mark (overlay mark) formed on the current layer and a certain material layer below (also known as the previous layer) at the same time, thereby interpreting the layer between the current layer and the pattern of the previous layer iteration error.

As can be seen from FIG. 1 , the stacking error detection device 10 includes a light source 11 , an optical system 12 , an objective lens 21 and a detector 23 .

The light source 11 is used to generate a measurement light. In some embodiments, the light source 11 may be a white light source, a broadband light source, or a composite light source composed of a plurality of monochromatic lights. In some embodiments, the white light source can be selected, for example, as an Xe light source, and the broadband refers to generating light including ultraviolet light, visible light, infrared light waveband or a combination of the above wavebands, and the composite light source can be composed of multiple laser beams of different wavelengths through frequency mixing get.

The optical system 12 is used to guide the measurement light emitted by the light source 11 into the objective lens 21 . Specifically, the optical system 12 may sequentially include a collimating lens 13 , a filter 14 , a polarizer 16 , a first lens 17 , a second lens 19 and a beam splitter 20 along the propagation direction of the measurement light. . The collimating lens 13 is used for collimating the measurement light. The filter 14 is used to pass light of a single wavelength. In some embodiments, the filter 14 is monochromatic, but not limited thereto. In addition, when the light source 11 uses a laser light source, the filter 14 can also be omitted. The polarizer 16 is used to generate linearly polarized light. In some embodiments, a polarizing beamsplitter can also be used instead of the polarizer 16 . The first and second lenses 17 and 19 are, for example, focusing lenses for condensing light. The beam splitter 20 is used to guide and incident the measurement light into the objective lens 21 , and in some embodiments, the beam splitter 20 may be a prism, a grating, or a combination of a prism and a grating. In addition, the optical system 12 may further include a lens group 22 for condensing light between the objective lens 21 and the detector 23 .

Furthermore, the optical system 12 further includes an aperture 15 and a field diaphragm 18 , both of which are used to adjust the measurement light into incident light that is symmetrical with respect to the center of the optical axis of the objective lens 21 . Specifically, in the parallel light system, the aperture 15 (also called aperture diaphragm) is arranged in front of the polarizer 16 to generate a light spot that meets the shape requirements of the objective lens 21 for incident light, that is, to determine the shape of the image. In some embodiments, the light-transmitting portion 15A of the aperture 15 may be designed as a circle (as shown in FIG. 3 ), a square, a rectangle, a slit or an arbitrary polygon. The field diaphragm 18 is disposed between the first lens 17 and the second lens 19, and is used to generate a light spot that meets the requirements for the size of the incident light, that is, to determine the imaging range.

Please refer to FIG. 1 and FIG. 2 together, the objective lens 21 is used to guide the measurement light B to the layer-by-layer mark M. As shown in FIG. In some embodiments, the stacked mark M consists of an upper and lower two-layer grating structure fabricated on a semiconductor substrate S (as shown in FIG. 2 ). Here, the grating structure refers to a periodic structure known in the art. The lower grating structure G1 can be formed on a certain material layer (also referred to as the front layer L1 ) on the semiconductor substrate S through processes such as exposure, development, and etching. The front layer L1 is not limited to be located directly on the semiconductor substrate S, and other structural layers may also be formed therebetween. The upper grating structure G2 is usually formed on the uppermost material layer (also referred to as the current layer L2 ) after the current process such as exposure, development, and etching. In addition, there is at least one intermediate material layer L3 between the upper and lower grating structures G1 and G2. The stacking error refers to the position error d between the upper and lower grating structures G1 and G2 (as shown in FIG. 2 ). By detecting the stacking error of the stacking mark M, the error in the overlay position of the pattern between the current layer L2 and the previous layer L1 can be judged.

It should be understood that, in order to detect the stacking error between the corresponding graphics of the current layer L2 and the previous layer L1, the stacking mark M usually includes a plurality of groups along the first direction (for example, the X direction) and the second direction ( For example, a two-layer grating structure arranged in the Y direction perpendicular to the X direction).

Please continue to refer to FIG. 1 , the measurement light can be diffracted on the laminated mark M, and the objective lens 21 can collect the diffracted light from the laminated mark M, especially the diffracted light of each main pole except the central main pole diffracted light (also called the central main pole diffracted light). That is, the diffracted light of the positive main pole and the diffracted light of the negative main pole, for example, the diffracted light of the positive 1st order, the diffracted light of the negative 1st order, the diffracted light of the positive 2nd order, the diffracted light of the negative 2nd order, etc.), and collect these diffracted lights to the on the pupil plane (not shown).

The detector 23 is disposed on the pupil surface of the objective lens 21, and is used for detecting the light signals of the positive main pole diffracted light and the negative main pole diffracted light from the stacked mark M. In some embodiments, the detector 23 may employ a photo-coupled element (CCD) or a complementary metal-oxide-semiconductor (CMOS).

It should be noted that, in the embodiments introduced in this paper, the stacking error of the stacking mark M can be calculated only by detecting the optical signals of the positive 1st-order diffracted light and the negative 1st-order diffracted light (two beams as shown in FIG. 1 ). , but the diffracted light of higher order (ie, above 2nd order) can also be used to detect stacking errors.

Please refer to FIG. 4 , the optical signals of the positive first-order diffracted light and the negative first-order diffracted light detected by the detector 23 each have a circular light intensity distribution, the shape of which is corresponding to the shape of the light-transmitting portion 15A of the aperture 15 .

When the position error d between the upper and lower grating structures G1 and G2 of the stacked mark M is 0, the optical signals of the positive first-order diffracted light and the negative first-order diffracted light detected by the detector 23 can have the same light Intensity distribution; relatively, when the position error d between the upper and lower grating structures G1 and G2 of the stacked mark M is not 0, the difference between the positive first-order diffracted light and the negative first-order diffracted light detected by the detector 23 is The light intensity distribution of the light signal is different. In this way, by comparing the difference in the light intensity distribution of the positive 1st-order diffracted light and the negative 1st-order diffracted light (that is, using the result of subtracting the light intensity distribution of the positive 1st-order diffracted light and the negative 1st-order diffracted light), the detector 23 The stacking error signal of the stacking mark M can be obtained. Then, by analyzing the light intensity distribution of the stacking error signal (as shown in FIG. 5 ) by, for example, a processing unit (not shown) in the detector 23 , the stacking error of the stacking mark M can be calculated.

However, as can be seen from Fig. 5, some noise N (or very low intensity) may appear in some areas of the above-mentioned stacked error signal (the area circled in the figure, also called bad area). signal), which will interfere with the interpretation of the stacking error signal and cause the accuracy of stacking error detection to be affected.

After research, it is found that these noises N mainly originate from the light incident on the stacked mark M at a specific angle, which is prone to total reflection in the intermediate material layer L3 between the upper and lower grating structures G1 and G2 (as shown in FIG. 2 ). The light B1)) shown is either absorbed in energy and cannot be detected well by the detector 23 . Therefore, if part of the test light that generates noise N can be directly blocked by the aperture 15, the noise N in the stacking error signal can be effectively removed, so as to prevent it from interfering with the interpretation of the stacking error signal, thereby improving the stacking performance. The accuracy of error detection.

In order to achieve the above-mentioned purpose, some embodiments of the present disclosure employ special apertures 15 as shown in FIGS. 6 , 7A to 7B and 9 . In some embodiments, the aperture 15 may have at least one light-transmitting area, and the position, size and/or shape of the light-transmitting area may be adjustable according to the position of the noise N in the stacking error signal.

It should be noted that, since the shape (circle, see FIG. 5 ) of the light intensity distribution of the stacking error signal detected by the detector 23 corresponds to the shape of the light-transmitting portion 15A of the aperture 15 , the The position of the noise N may also correspond to the relative position within the light-transmitting portion 15A of the aperture 15 (ie, have a mapping relationship).

With this feature, the position, size and/or shape of at least one light-transmitting region of the aperture 15 (within the range of the light-transmitting portion 15A) can be adjusted according to the position of the noise N in the stacking error signal (or the aperture can be adjusted). position, size and/or shape of at least one non-transmissive area of 15 ), so that part of the test light that would generate noise N is directly blocked by aperture 15 and the noise N in the stacking error signal can be removed.

Please refer to FIGS. 6 , 7A and 7B together. In some embodiments, the aperture 15 is an active matrix liquid crystal module having a plurality of liquid crystal cells U arranged in a matrix.

Each liquid crystal unit U sequentially includes: a first polarizer 71 , a first electrode 72 , a liquid crystal layer 73 , a second electrode 74 and a second polarizer 75 along the direction in which the measurement light passes through the aperture 15 . More specifically, the liquid crystal layer 73 is disposed between the first and second electrodes 72 and 74 , and alignment films 72A and 74A are formed on the inner sides of the first and second electrodes 72 and 74 , respectively. The alignment grooves of the alignment film 72A and the alignment film 74A are perpendicular to each other, so that the alignment direction of the liquid crystal molecules in the liquid crystal layer 73 (in the absence of an electric field) can be twisted by 90 degrees from the end of the alignment film 72A to the end of the alignment film 74A (as shown in Figure 7A). The first polarizer 71 and the second polarizer 75 are disposed on the outer sides of the first and second electrodes 72 and 74, respectively, and their polarization directions are perpendicular to each other. In addition, each liquid crystal unit U includes a thin film transistor (TFT) substrate (not shown) for outputting a voltage V to control the alignment direction of the liquid crystal molecules.

As can be seen from FIG. 7A, when no voltage is applied between the first and second electrodes 72 and 74, the measurement light passing through the liquid crystal layer 73 can rotate 90 degrees with the twist of the liquid crystal molecules, and pass through the liquid crystal layer 73. The first and second polarizers 71 and 75 are vertical. It can be seen from FIG. 7B that when a voltage V is applied between the first and second electrodes 72 and 74, the liquid crystal molecules (such as positive liquid crystal molecules) in the liquid crystal layer 73 can be aligned along the direction of the electric field. Therefore, the rotation will not occur, and the second polarizer 75 cannot be passed through.

It should be understood that the structure and control method of each liquid crystal unit U of the aperture 15 are not limited by the above embodiments. For example, in some embodiments, the polarization directions of the first and second polarizers 71 and 75 can also be parallel to each other, and when no voltage is applied between the first and second electrodes 72 and 74 , with the liquid crystal molecules The measurement light rotated by 90 degrees cannot pass through the second polarizer 75 , but when the voltage V is applied between the first and second electrodes 72 and 74 , the measurement light can pass through the second polarizer 75 .

Therefore, by controlling the voltage applied between the first and second electrodes 72 and 74 through the TFT substrate, the direction of the liquid crystal molecules in each liquid crystal cell U can be controlled to allow or not allow light to pass through. In this way, the position, size and/or shape of at least one light-transmitting region R1 and at least one non-light-transmitting region R2 within the light-transmitting portion 15A of the aperture 15 (inside the dotted circle) can be (arbitrarily) adjustable , wherein the light-transmitting region R1 corresponds to the state in which the liquid crystal cell U allows light to pass through (as shown in FIG. 7A ), and the non-light-transmitting region R2 corresponds to the state in which the liquid crystal cell U does not allow light to pass through (as shown in FIG. 7B ).

It is worth mentioning that the liquid crystal unit U of the peripheral portion 15B of the aperture 15 (ie, the portion outside the light-transmitting portion 15A) can be normally adjusted to a state that does not allow light to pass through (as shown in FIG. 7B ). Alternatively, in some embodiments, only the light-transmitting portion 15A of the aperture 15 is an active matrix liquid crystal module, and the peripheral portion 15B of the aperture 15 can be changed to a mechanical light baffle to save energy consumption.

Further, in some embodiments, the detector 23 can control and modulate at least one light-transmitting region R1 of the aperture 15 (active matrix liquid crystal module) and the The position, size and/or shape of at least one non-transparent region R2.

Please refer to FIG. 8 , which shows a block diagram of a control system composed of the detector 23 and the aperture 15 according to some embodiments. For example, when the detector 23 detects the stacking error signal (light intensity distribution) of the stacking mark M, a processing unit 23A in the detector 23 can obtain the distribution position of the noise by analyzing the stacking error signal. For example, the processing unit 23A of the detector 23 can obtain the position coordinates where the light intensity is higher and lower than a certain value by stacking the light intensity distribution of the error signal (as shown in FIG. 5 ), that is, obtaining the stacking error signal The position coordinates of the normal signal part and the noise in . Next, the processing unit 23A can generate a position data 80 including the position coordinates corresponding to the light-transmitting region R1 and the non-light-transmitting region R2 of the aperture 15 through arithmetic conversion.

The detector 23 is electrically connected to the aperture 15 (active matrix liquid crystal module) by wire (eg wire, cable or optical fiber) or wireless (eg Bluetooth, wifi or near field communication (NFC) transmission). The aperture 15 includes a panel unit 151 , a timing controller (TCON) 152 , a scan driving unit 153 and a data driving unit 154 . In some embodiments, the panel unit 151 has liquid crystal cells (also called display cells) arranged in multiple columns and rows, and the structure of each liquid crystal cell can be referred to, for example, as shown in FIGS. 7A and 7B . The timing controller 152 is used for receiving the position data 80 generated by the processing unit 23A of the detector 23 , and providing a scan control signal Ss and a data control signal Sd to the scan driving unit 153 and the data driving unit 154 respectively. The scan driving unit 153 and the data driving unit 154 are used to generate driving signals according to the above control signals to control the operation of the panel unit 151 by, for example, writing voltage data of thin film transistors (TFTs) to the liquid crystal cells of the panel unit 151 .

More specifically, in some embodiments, the scan driving unit 153 may apply the scan driving signals S ₁ ˜Sm generated based on the scan control signal Ss to each liquid crystal cell according to a certain column scan sequence in a period of time Column scanlines. As described above, the scan driving signals S ₁ ˜Sm are applied to the gate (not shown) of the TFT corresponding to each liquid crystal cell, so as to turn on the corresponding TFT by applying a gate voltage, so that the voltage corresponding to the liquid crystal cell is Data can be written by the data drive unit 154 .

In addition, in some embodiments, the data driving unit 154 is configured to write voltage data into the liquid crystal cell array based on the data control signal Sd in each time period. For example, the data driving unit 154 can simultaneously apply the data driving signals D ₁ ˜Dn to the data lines of the rows of the liquid crystal cells, thereby controlling the magnitude or time of the voltage applied to the source of each TFT.

As described above, the embodiments of FIGS. 6 to 8 can correspondingly control each liquid crystal cell U to allow or not allow light to pass through based on the noise position in the stacking error signal (as shown in FIGS. 7A and 7B ). Show). For example, when the processing unit 23A of the detector 23 obtains the distribution position of the noise by analyzing the stacking error signal, it can then obtain a light-transmitting region R1 and a non-light-transmitting region R2 corresponding to the aperture 15 through arithmetic conversion. The position data 80 of the position coordinates. Thus, the detector 23 can further control the light-transmitting or non-light-transmitting state of each liquid crystal cell U of the aperture 15 based on the position data 80 (by applying or not applying a voltage), and make the aperture 15 (within the range of the light-transmitting portion 15A) ) of the light-transmitting region R1 and the non-light-transmitting region R2 respectively correspond to the positions of the normal signal and noise in the stacking error signal, so that part of the test light that may generate noise is directly blocked by the aperture 15 . In this way, noise in the stacking error signal can be removed automatically and accurately, so as to improve the quality of the stacking error signal and improve the accuracy of stacking error detection.

In some embodiments, the aperture 15 can also be a micro-lens array module having a plurality of micro-lens units arranged in a matrix. As can be seen from FIG. 9 , each micro lens unit U' includes a micro lens 91 , a support member 92 for supporting and allowing the micro lens 91 to move, and a control circuit 93 electrically connected to the support member 92 . The support member 92 is an actuating member, and can change the inclination angle T of the microlens 91 according to the magnitude of the voltage applied by the control circuit 93 . When the inclination angle T of the microlens 91 exceeds a certain angle, the traveling direction of the light can be changed so that the light will not pass through the micromirror unit U' (as shown in the figure). That is to say, by changing the inclination angle T of the micro-lens 91, the effect of allowing or not allowing light to pass through the micro-lens unit U' can also be achieved.

Therefore, in some embodiments, the aperture 15 in the embodiments shown in FIG. 6 to FIG. 8 can also be changed to a micro-lens array module, and by controlling the micro-lens in each micro-lens unit U' of the micro-lens array module The inclination angle T of 91 allows or does not allow light to pass through, so that the position, size and/or shape of the light-transmitting area and the non-light-transmitting area of the aperture 15 can be modulated, thereby achieving the effect of removing noise in the stacking error signal. Purpose.

FIG. 10 shows a flowchart of a method 200 for stacking error detection according to some embodiments. In step 201, a measurement light is emitted by a light source. In step 202, the measurement light is guided into an objective lens by an optical system. In step 203 , the measurement light is guided to the layer-by-layer mark through the objective lens, and the positive and negative main-pole diffracted light diffracted from the layer-by-layer mark is collected on a pupil plane of the objective lens. In step 204, a detector is used to detect the light intensity distribution of the positive and negative main pole diffracted lights, and the light intensity distributions of the positive and negative main pole diffracted lights are subtracted to obtain a reference layer of the laminated mark. overlapping error signal. In step 205, the detector modulates the position, size and/or shape of at least one light-transmitting area of an aperture in the optical system according to the position of the noise in the referenced stacking error signal. In step 206, the light intensity distribution of the positive and negative main pole diffracted light is detected by the detector, and the light intensity distribution of the positive and negative main pole diffracted light is subtracted to obtain a formal layered layer of the layered mark. error signal.

It should be understood that the steps of the stacking error detection method described above are only examples, and the stacking error detection method in some embodiments may also include other steps and sequence of steps.

To sum up, the embodiments of the present disclosure have the following advantages: since the diaphragm (aperture stop) in the optical system has at least one light-transmitting area, and the position, size and/or shape of the light-transmitting area are based on the layer detected by the detector The position of the noise in the stacking error signal is adjustable. Therefore, by adjusting the position, size and/or shape of the light-transmitting area (or the non-light-transmitting area) of the aperture, the amount of test light incident on the stacking mark can be changed. angle, and further removes noise from the stacked error signal. In this way, the quality of the stacking error signal can be improved, and the accuracy of stacking error detection can be improved.

According to some embodiments, a stacking error measuring apparatus is provided, which includes an objective lens, a light source, an optical system and a detector. The light source is used to generate a measurement light. The optical system is used to guide the measurement light into the objective. The objective lens is used to guide the measuring light to the stacked marks, and at the same time collects the positive main pole diffracted light and the negative main polar diffracted light diffracted from the stacked marks to a pupil plane of the objective lens. The detector is arranged on the pupil surface of the objective lens, and is used to detect the light intensity distribution of the above-mentioned positive and negative main pole diffracted light, and use the positive and negative main pole diffracted light to subtract the light intensity distribution to obtain the layered mark. Layer-by-layer error signal. Wherein, the aforementioned optical system includes an aperture having at least one light-transmitting region, and the position, size and/or shape of the light-transmitting region can be adjusted according to the position of noise in the stacking error signal.

According to some embodiments, the stacking error signal has a light intensity distribution whose shape corresponds to the shape of a light-transmitting portion of the aperture.

According to some embodiments, the detector is electrically connected to the aperture, and adjusts the position, size and/or shape of at least one light-transmitting region and at least one non-light-transmitting region of the aperture according to the position of the noise in the stacking error signal.

According to some embodiments, the aperture is an active matrix liquid crystal module. By controlling the direction of liquid crystal molecules in at least one liquid crystal cell of the active matrix liquid crystal module to allow or not allow light to pass through, at least one light-transmitting area of the adjustable aperture is connected to The position, size and/or shape of at least one non-transparent area.

According to some embodiments, the aperture is a micro-lens array module, and by controlling the inclination angle of the micro-lens in at least one micro-lens unit of the micro-lens array module to allow or not allow light to pass through, at least one light-transmitting area of the adjustable aperture is connected to The position, size and/or shape of at least one non-transparent area.

According to some embodiments, the optical system sequentially includes: a collimating lens, a filter, an aperture, a first lens, a field stop, a second lens, and a beam splitter along the propagation direction of the measurement light.

According to some embodiments, the positive main pole diffracted light and the negative main pole diffracted light are positive 1st order diffracted light and negative 1st order diffracted light.

According to some embodiments, the stacked mark consists of a two-layer grating structure of a current layer and a front layer on a substrate.

According to some embodiments, a stacking error measuring apparatus is provided, which includes an optical system and a detector. The optical system is used to guide a measurement light from a light source into an objective lens, and the objective lens is used to guide the measurement light to the layer-by-layer mark, while collecting the positive main-pole diffracted light and the negative The main pole diffracted light, wherein the optical system includes an aperture, which has at least one light-transmitting area and at least one non-light-transmitting area. The detector is used for subtracting the light intensity distributions of the above-mentioned positive main pole diffracted light and negative main pole diffracted light to obtain a laminated error signal of the laminated mark, and modulates at least the aperture of the aperture according to the position of the noise in the laminated error signal. The position, size and/or shape of a light-transmitting area and at least one non-light-transmitting area.

According to some embodiments, a method for measuring stacking errors is provided, comprising: emitting a measurement light through a light source; guiding the measurement light into an objective lens through an optical system; guiding the measurement light to a stack mark through the objective lens and collect the diffracted light of the positive main pole and the diffracted light of the negative main pole from the layered mark to a pupil surface of the objective lens; detect the light intensity distribution of the above-mentioned positive and negative main pole diffracted light by a detector, And use the light intensity distributions of the positive and negative main pole diffracted lights to be subtracted to obtain a reference stacking error signal of the stacking mark; according to the position of the noise in the reference stacking error signal, the detector modulates the optical The position, size and/or shape of at least one light-transmitting area of an aperture in the system; and detecting the light intensity distribution of the above-mentioned positive and negative main pole diffracted light by a detector, and using the said positive and negative main pole diffracted light The light intensity distributions are subtracted to obtain a formal stacking error signal of the stacking marks.

Although the present disclosure is disclosed above with the aforementioned embodiments, it is not intended to limit the present disclosure. Those skilled in the art to which the present disclosure pertains may make slight changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure should be determined by what is defined by the claims.

Claims (10)

1. a stacking error measuring device, is characterized in that, comprises: an objective lens; a light source for generating a measurement light; an optical system for guiding the measurement light into the objective lens for guiding the measurement light onto the stacked mark, while the positive principal pole diffracted light diffracted from the stacked mark and the The negative main pole diffracted light is collected on a pupil plane of the objective; and a detector, arranged on the pupil surface of the objective lens, for detecting the light intensity distribution of the diffracted light of the positive main pole and the diffracted light of the negative main pole, and utilizing the diffracted light of the positive main pole and the diffracted light of the negative main pole The light intensity distribution of the incident light is subtracted to obtain a layer-by-layer error signal of the layer-by-layer mark; Wherein, the optical system includes an aperture, the aperture has at least one light-transmitting area, and the position, size and/or shape of the light-transmitting area are adjustable according to the position of noise in the stacking error signal. 2 . The stacking error measuring device of claim 1 , wherein the stacking error signal has a light intensity distribution, the shape of which corresponds to the shape of a light-transmitting portion of the aperture. 3 . 3. The stacking error measuring device as claimed in claim 1 or 2, wherein the detector is electrically connected to the aperture, and modulates the at least one light-transmitting area of the aperture according to the position of noise in the stacking error signal and the position, size and/or shape of at least one non-transmissive region. 4. The stacking error measuring device as claimed in claim 3, wherein the aperture is an active matrix liquid crystal module, and the direction of liquid crystal molecules in at least one liquid crystal cell of the active matrix liquid crystal module is controlled to allow or disallow light. Through this, the position, size and/or shape of the at least one light-transmitting area and the at least one non-light-transmitting area of the aperture can be adjusted. 5 . The stacking error measuring device of claim 3 , wherein the aperture is a micro-lens array module, and the inclination angle of the micro-lens in at least one micro-lens unit of the micro-lens array module is controlled to allow or disallow light. 6 . Through this, the position, size and/or shape of the at least one light-transmitting area and the at least one non-light-transmitting area of the aperture can be adjusted. 6. The stacking error measuring device according to claim 1 or 2, wherein the optical system sequentially comprises: a collimating lens, a filter, the aperture, a first lens, a Field diaphragm, a second lens and a beam splitter. 7 . The stacking error measuring device according to claim 1 , wherein the positive main-pole diffracted light and the negative main-pole diffracted light are positive first-order diffracted light and negative first-order diffracted light. 8 . 8. The stacking error measuring device as claimed in claim 1 or 2, wherein the stacking mark is composed of a two-layer grating structure of a current layer and a front layer on a substrate. 9. A stacking error measuring device, comprising: an optical system for guiding a measurement light from a light source into an objective lens for guiding the measurement light onto a layered mark while collecting the positive principal diffracted from the layered mark polar diffracted light and negative main polar diffracted light, wherein the optical system includes an aperture, and the aperture has at least one light-transmitting area and at least one non-light-transmitting area; and a detector for subtracting the light intensity distributions of the diffracted light from the positive main pole and the diffracted light from the negative main pole to obtain a layer-by-layer error signal of the layer-by-layer mark; The position, size and/or shape of the at least one light-transmitting area and the at least one non-light-transmitting area of the aperture are adjusted by position. 10. A method for measuring stacking errors, comprising: emit a measurement light through a light source; Guide the measurement light into an objective lens through an optical system; The measurement light is guided to the layered mark by the objective lens, and the positive main pole diffracted light and the negative main pole diffracted light diffracted from the layered mark are collected on a pupil surface of the objective lens; The light intensity distribution of the diffracted light from the positive main pole and the diffracted light from the negative main pole is detected by a detector, and the layer is obtained by subtracting the intensity distribution of the diffracted light from the positive main pole and the diffracted light from the negative main pole. a reference stacking error signal of the stacking mark; modulate the position, size and/or shape of at least one light-transmitting region of an aperture in the optical system by the detector according to the position of the noise in the reference stacking error signal; and The detector detects the light intensity distribution of the diffracted light from the positive main pole and the diffracted light from the negative main pole, and uses the light intensity distribution of the diffracted light from the positive main pole and the diffracted light from the negative main pole to subtract the light intensity distribution to obtain the layer. A formal stacking error signal for stacking marks.

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