Patent ID: 12244926

DETAILED DESCRIPTION

The above-described aspects, features and advantages are specifically described hereafter with reference to the accompanying drawings such that one having ordinary skill in the art to which the present disclosure pertains can embody the technical spirit of the disclosure easily. In the disclosure, detailed description of known technologies in relation to the subject matter of the disclosure is omitted if it is deemed to make the gist of the disclosure unnecessarily vague. Hereafter, preferred embodiments according to the disclosure are specifically described with reference to the accompanying drawings. In the drawings, identical reference numerals can denote identical or similar components.

The terms “first”, “second” and the like are used herein only to distinguish one component from another component. Thus, the components should not be limited by the terms. Certainly, a first component can be a second component, unless stated to the contrary.

When one component is described as being “in the upper portion (or lower portion)” or “on (or under)” another component, one component can be directly on (or under) another component, and an additional component can be interposed between the two components.

When any one component is described as being “connected”, “coupled”, or “connected” to another component, any one component can be directly connected or coupled to another component, but an additional component can be “interposed” between the two components or the two components can be “connected”, “coupled”, or “connected” by an additional component.

Throughout the disclosure, each component can be provided as a single one or a plurality of ones, unless explicitly stated to the contrary.

The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless explicitly indicated otherwise. It is to be further understood that the terms “comprise” or “include” and the like, set forth herein, are not interpreted as necessarily including all the stated components or steps but can be interpreted as excluding some of the stated components or steps or can be interpreted as including additional components or steps.

Throughout the disclosure, the terms “A and/or B” as used herein can denote A, B or A and B, and the terms “C to D” can denote C or greater and D or less, unless stated to the contrary.

Hereafter, described are an overlay measurement device and method for controlling a focus movement and a program storage medium therefor, in several embodiments.

FIG.1is a conceptual view showing an overlay measurement device in one embodiment.

Referring toFIG.1, the overlay measurement device100in one embodiment measures an error between a first overlay mark (OM1) and a second overlay mark OM2that are respectively formed in a different layer formed in a wafer140.

For example, the first overlay mark OM1may be an overlay mark that is formed in a previous layer, and the second overlay mark OM2is an overlay mark that is formed in a current layer. The overlay marks are formed in a scribe lane while forming a layer for forming a semiconductor device, in a die area. For example, the first overlay mark OM1may be formed together with an insulation layer pattern, and the second overlay mark OM2may be formed together with a photoresist pattern that is formed on the insulation layer pattern.

At this time, the first overlay mark OM1is covered by the photoresist layer, while the second overlay mark OM2is exposed to the outside, and the first overlay mark OM1is made of an oxide having optical properties that differ from those of the second overlay mark OM2comprised of a photoresist material. Additionally, although the physical position of the first overlay mark OM1and the physical position of the second overlay mark OM2are different from each other, the focal surface of the first overlay mark OM1and the focal surface of the second overlay mark OM2are identical with each other or different from each other.

The overlay measurement device100in one embodiment may comprise a light source110, a first beam splitter112, a first mirror113, a first spectrum filter (a color filter)114, a second spectrum filter115, a beam combiner116, a second mirror117, a relay lens118, a polarizing filter121, an aperture151, a second detector133, a focus actuator134, a zoom lens132, a first detector131, a second beam splitter130, an optical element127, a third beam splitter124, a lambda wave plate122, an objective lens120, a lens focus actuator125, an aperture151, an AF161, and a processor170. In the present disclosure, the first spectrum filter and the second spectrum filter may be replaced with various types of filters. Additionally, the spectrum filter may comprise at least one of a filter wheel, a linear translation device, and a flipper device.

For example, the first detector131, the second beam splitter130, the zoom lens132, the second detector133and the actuator134are configured to orient lighting toward an overlay measurement target, and may be referred to as a lighting part. The lighting part may orient lighting from at least one lighting source toward an overlay measurement target. The overlay measurement target may comprise a wafer, for example.

For example, the light source110, the first beam splitter112, the first mirror113, the first spectrum filter (a color filter)114, the second spectrum filter115, the beam combiner116, the second mirror117, the aperture151, the relay lens118, the polarizing filter121, the lambda wave plate122, and the third beam splitter124may be provided to obtain one or more images in relation to a focus in the target, and referred to as a collection part. The collection part may comprise an objective lens and a detector, for example.

FIG.1shows a configuration of the overlay measurement device100in one embodiment, and components of the overlay measurement device100are not limited to those of the embodiment illustrated inFIG.1. When necessary, some of the components can be added, changed or removed. For example, the overlay measurement device100may comprise a memory (not illustrated) that stores instructions, programs, logics and the like that enable the processor170to control the operation of each component of the overlay measurement device100.

In one embodiment, a halogen lamp, a xenon lamp, a supercontinuum laser, a light-emitting diode, a laser induced lamp and the like may be used as the light source110.

In one embodiment, the first beam splitter112splits a beam irradiated from the light source110into two beams. The first beam splitter112transmits some of the beam irradiated from the light source110, and reflects some of the beam irradiated from the light source110, to split the beam into two beams.

In one embodiment, the first mirror113is disposed between the first beam splitter112and the second spectrum filter115, and changes the path of the beam reflected by the first beam splitter112toward the second spectrum filter115.

In one embodiment, the first spectrum filter114adjusts the central wavelength and bandwidth of the beam having passed through the first beam splitter112, out of the beams split by the first beam splitter112, such that the central wavelength and bandwidth may be appropriate to obtain the image of the second overlay mark OM2formed in the current layer. Any one of a filter wheel, a linear translation device and a flipper device may be used as the spectrum filter.

In one embodiment, the second spectrum filter115adjusts the central wavelength and bandwidth of the beam reflected from the first beam splitter112, out of the beams split by the first beam splitter112, such that the central wavelength and bandwidth may be appropriate to obtain the image of the first overlay mark OM1formed in the previous layer.

In one embodiment, the beam combiner116combines the light having passed through the first spectrum filter114and the light having passed through the second spectrum filter115. The light having passed through the first spectrum filter114passes through the beam combiner116, and the beam having passed through the second spectrum filter115is reflected by the beam combiner116and is combined with the beam having passed through the beam combiner116, after its path is changed by the second mirror117toward the beam combiner116, and then passes through the aperture151.

In one embodiment, the aperture151(e.g., a pin hole) changes the beam having passed through the beam combiner such that the beam may be appropriate to photograph the first overlay mark OM1.

In one embodiment, the second detector133detects the beam reflected by the second beam splitter130. The second detector133is disposed at the focus actuator134, and a distance between the second beam splitter130and the second detector133is adjusted. The second detector133obtains the image of the first overlay mark OM1.

In one embodiment, the first detector131detects the beam having passed through the second beam splitter130. The first detector131may obtain the image of the second overlay mark OM2.

Alternatively, the first detector only may obtain the image of the first overlay mark OM1and the image of the second overlay mark OM2, while the second detector does not operate, depending on user settings.

In one embodiment, the zoom lens132is disposed between the second beam splitter130and the focus actuator134. The zoom lens132receives a position change value of the second detector133from the focus actuator134, and based on the position change value, matches the magnification of the image of the second overlay mark OM2and the magnification of the image of the first overlay mark OM1. Since an optical path distance between the second detector133and the second beam splitter130differs from an optical path distance between the first detector131and the second beam splitter130depending on a difference in the heights of the first overlay mark OM1and the second overlay mark OM2, the magnification of the image obtained by the first detector131and the magnification of the image obtained by the second detector133may differ. To measure an overlay error accurately, the magnifications need to be matched.

In one embodiment, the second beam splitter130splits the beam gathered by the objective lens120into two beams. The second beam splitter130may comprise a tube beam splitter and a dichroic filter. The dichroic filter transmits a beam of a specific wavelength. The beam gathered by the objective lens120passes through the lambda wave plate122, the third beam splitter124and the optical element127and is split into two beams by the second beam splitter130. That is, the beam gathered by the objective lens120splits into a beam appropriate to detect the first overlay mark OM1and a beam appropriate to detect the second overlay mark OM2.

In one embodiment, the optical element127may comprise a hot mirror and a cold mirror.

In one embodiment, the third beam splitter124splits the beam combined through the beam combiner116into two beams again. The beam combined through the beam combiner116is split into two beams by the third beam splitter124, through the relay lens118and the polarizing filter121, in a polarized state.

In one embodiment, the objective lens120concentrates the beam, being combined by the combiner116, being reflected by the third beam splitter124and then becoming one beam of polarized light, through the lambda wave plate122, on the measurement position of a wafer, and gathers a beam being reflected in the measurement position. The objective lens120is disposed at the lens focus actuator125.

In one embodiment, the lens focus actuator125adjusts a distance between the objective lens120and a wafer140such that a focal surface may be placed at the first overlay mark OM1or the second overlay mark OM2. The lens focus actuator125moves the objective lens120perpendicularly toward the wafer (e.g., in the Y direction), under the control of the processor170, to adjust a focal length.

In one embodiment, the optical element127is installed in a way that the optical element and the path of the beam having passed through the beam splitter form an angle of 45°, to send out the beam to an auto focus module, and is characterized by reflecting a long-wavelength beam and transmitting a short-wavelength beam, or reflecting a short-wavelength beam and transmitting a long-wavelength beam. The optical element may be comprised of one of a hot mirror or a cold mirror.

The auto focus sensor obtains a signal based on the position of a focus by using a reflected light reflected from the measurement area of a wafer, and to adjust the position of the focus, the actuator adjusting a distance between the measurement area of the wafer and the objective lens is adjusted.

At a time when a focus is scanned, the first detector131may obtain first images (e.g., reference images) at each measurement point. For example, the reference images may comprise one or more images of each focus.

In one embodiment, the processor170may obtain a focus graph (e.g., a first focus graph and a second focus graph) in relation to each of the two layers (e.g., a first layer and a second layer) of the first images (e.g., reference images), and identify one of a midpoint, a maximum value of each layer, and a maximum value out of minimums between the two layers as a reference focus in relation to the obtained focus graph. For example, the processor170may determine a focus (e.g., 395) corresponding to an average of a first maximum contrast index (e.g., 350) on the first focus graph and a second maximum contrast index (e.g., 440) on the second focus graph as the reference focus.

In one embodiment, as measurement images are obtained from the detector, the processor170may identify a contrast index, based on each of the focus graphs (e.g., a third focus graph and a fourth focus graph) of two layers (e.g., a third layer and a fourth layer) of the measurement images that are obtained based on the identified reference focus. The processor170may obtain an image corresponding to a current position of the objective lens120, through the detector. The processor170may obtain an image, based on the movement of a stage on which a wafer140is placed.

In one embodiment, the processor170may identify a reference focus (e.g., 500) by using a first focus graph of a first layer of a first image (e.g., a reference image) and a second focus graph of a second layer of the first image. Then the processor170may identify two third contrast indices in relation to the identified reference focus, based on a third focus graph of a second image (e.g., a measurement image), and identify two fourth contrast indices in relation to the identified reference focus, based on a fourth focus graph of the measurement image.

In one embodiment, the processor170may identify one third contrast index and one fourth contrast index that have a minimum focal length, out of the two third contrast indices and the two fourth contrast indices. Then the processor170may identify whether a focus value corresponding to one third contrast index identified is identical with a focus value corresponding to one fourth contrast index identified.

In one embodiment, the processor170may identify a focus corresponding to each contrast index that is identified through each of the two layers of a reference image, and calculate a difference (e.g., 50) between the reference focus (e.g., 500) and the identified focus550.

Then the processor170may move the objective lens120to a focus corresponding to the measurement image, based on the calculated difference. The processor170may adjust a focal length of the objective lens120by controlling the lens focus actuator125.

For example, the processor170deducts the calculated difference from the value of the reference focus, and operates the lens focus actuator125to move the objective lens120to a position corresponding to the deducted focus.

In one embodiment, the processor170may control the movement of the objective lens140, through the lens focus actuator125, based on the calculated difference, in relation to each measurement point of a wafer.

The processor170may be additionally provided in the overlay measurement device, or programmed and stored in another component.

FIG.2is a flowchart showing a method for controlling a focus movement of the overlay measurement device in one embodiment.FIG.3is an exemplary view showing focus graphs of two layers in one embodiment.FIG.4, (a) is an exemplary view showing focus graphs of two layers of a reference image in one embodiment, (b) is an exemplary view showing a contrast index in relation to a reference focus in two layers of an obtained image in one embodiment,4(c) is an exemplary view showing that a difference between the contrast indices obtained in (b) is applied to the focus graphs in relation to the image of (a), and4(d) is an exemplary view showing that a reference focus is adjusted based on a focus difference obtained in (c).

Hereafter, a method for controlling a focus movement of the overlay measurement device in one embodiment is described with reference toFIG.2,FIG.3, andFIG.4, (a) to (d).

In one embodiment, the processor170may identify whether the overlay measurement device starts measurement (S210). The processor170may determine whether the first detector starts to measure contrast in relation to a measurement point (e.g., a site).

In one embodiment, the processor170may obtain a focus graph in relation to each of the two layers of a reference image (S212). Confirming that an operation of measuring contrast in relation to a wafer starts, the processor170may obtain a focus graph of each of the two layers of the reference image from the memory (not illustrated).

Referring toFIG.3, one image may comprise a plurality of layers (e.g., two layers). In each of the layers, the contrast of each focus position may differ, and the processor170may identify a focus graph indicating the contrast of a corresponding layer, through a contrast index at each focus position.

For example, a first focus graph310indicates a contrast index in relation to a first layer (e.g., a previous layer), and a second focus graph320indicates a contrast index in relation to a second layer (e.g., a current layer).

For example, in the case of a first focus graph310, a focus has a maximum contrast index 35 at440, and in the case of a second focus graph320, a focus has a maximum contrast index 35 at350.

For example, two focuses440,520have the same contrast index (e.g., 19) in one focus graph (e.g., the first focus graph310).

Confirming that the operation of measuring contrast starts in relation to a wafer, the processor170, as described above, may obtain a focus graph in relation to each of the two layers of the reference image.

In one embodiment, the processor170may identify a reference focus in relation to the obtained focus graph (S214). The processor170may determine one of a midpoint, a maximum value of each layer, and a maximum value out of minimums between the two layers as the reference focus, by using a focus graph of each of the two layers in the reference image. The processor170may identify a focus position having a maximum contrast index through each focus graph.

Referring toFIG.4, (a), the processor170may obtain a reference image. Then the processor170may identify a focus (e.g., 460) having a maximum contrast index (e.g., 5) through a first focus graph411of the first layer (e.g., a previous layer) in the reference image. Additionally, the processor170may identify a focus (e.g., 540) having a maximum contrast index (e.g., 3) through a second focus graph412of the second layer (e.g., a current layer).

Then the processor170may identify a focus position (e.g., 500) of a reference focus413as a reference by using a focus position (e.g., 460, 540) corresponding to the maximum contrast index (e.g., 5, 3) in each of the layers (e.g., the first layer, the second layer).

For example, the processor170may determine an average of the focus position (e.g., 460, 540) having the maximum contrast index (e.g., 5, 3) as a focus position (e.g., 500) in relation to the reference focus413.

In one embodiment, the processor170may identify whether a measurement image is obtained (S216). The processor170may obtain a measurement image in relation to a wafer to be measured from the detector.

In one embodiment, the processor170may identify a contrast index, based on the reference focus and based on two layers of the measurement image (e.g., virtual focus graphs of two layers) (S218). As the measurement image in relation to the wafer is obtained, the processor170.

The processor170may identify a contrast index in relation to each of the two layers of the measurement image by using the reference focus413in the reference image.

Referring toFIG.4, (b), the processor170may identify a first contrast index (e.g., 1.75) based on the first focus graph421in relation to the first layer of the measurement image, and a second contrast index (e.g., 3) based on the second focus graph422in relation to the second layer of the measurement image, with respect to the reference focus413of the reference image.

For example, the first focus graph421and the second focus graph422are illustrated inFIG.4to describe the subject matter of the present disclosure. However, the processor170may not generate the first focus graph421in relation to the first layer and the second focus graph422in relation to the second layer. That is, as the measurement image is obtained, the processor170may identify the contrast indices of the two layers of the measurement image, based on the reference focus.

In one embodiment, the processor170may identify a focus corresponding to each of the contrast indices that are identified respectively in the two layers of the reference image (S220). The processor170may calculate a difference between the first contrast index (e.g., 1.75) and the second contrast index (e.g., 3) that are identified in the above process (S218), and identify an index having the same difference as the calculated difference through the two focus graphs of the reference image.

The processor170may calculate a contrast index difference (e.g., 3−1.75=1.25), based on the two focus graphs421,422of the measurement image, with respect to the reference focus413. Additionally, the processor170may determine a focus position corresponding to the calculated contrast index difference (e.g., 1.25) through the two focus graphs, in the reference image.

Referring toFIG.4, (c), the processor170may determine which focus has the same contrast index difference as the contrast index difference (e.g., 1.25) inFIG.4, (b).

For example, the processor170may determine that two points have a contrast index of 1.75 in the first focus graph411, and that two points have a contrast index of 3 in the second focus graph412. Then the processor170may identify points (e.g.,433,434) having the same focus, out of the two points on the first focus graph411and out of the two points on the second focus graph412.

The processor170, as described above, may determine that a first point434of the first focus graph411and a second point433of the second focus graph412are the points having the same contrast index difference as the contrast index difference (e.g., 1.25) inFIG.4, (b), and may determine the first point434and the second point433as an identified focus.

In one embodiment, the processor170may calculate a difference between the reference focus and the identified focus (S222). The processor170deducts the reference focus value (500) from the identified focus value (e.g., 550) to calculate a focus difference (e.g., 50).

In one embodiment, the processor170may move the objective lens to a focus corresponding to the measurement image, based on the calculated difference (S224). The processor170may determine a reference focus in the measurement image by using the focus difference.

Referring toFIG.4, (d), the processor170may control the lens focus actuator125to adjust a focal length of the objective lens120from the position (e.g., 500) of the reference focus413to the position (450) of the identified focus433.

In the present disclosure, a reference focus is identified through a focus graph in relation to each of the two layers of a reference image, and based on a difference between the identified reference focus and a focus identified through a measurement image, the focal length of the objective lens120is adjusted, to find a focus position of highest contrast in the measurement image, as described above.

Each of the above-described steps in the flowcharts may be performed regardless of the order illustrated, or performed at the same time. Further, in the present disclosure, at least one of the components, and at least one operation performed by at least one of the components can be embodied as hardware and/or software.

The embodiments are described above with reference to a number of illustrative embodiments thereof. However, embodiments are not limited to the embodiments and drawings set forth herein, and numerous other modifications and embodiments can be drawn by one skilled in the art within the technical scope of the disclosure. Further, the effects and predictable effects based on the configurations in the disclosure are to be included within the range of the disclosure though not explicitly described in the description of the embodiments.