JPH11288867A - Alignment method, formation of alignment mark, and aligner and method for exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the throughput, when the position alignment is performed by using the alignment marks, which are formed at respectively different layers in the X-direction and the Y-direction. SOLUTION: An X-direction alignment mark 40a and a Y-direction alignment mark 41a are formed in close proximity, so as to enter the same image-pickup region at the different layers on a substrate. The X-direction measurement and the Y-direction measurement are performed at the same time. Thus even when the position alignment is performed by the use of the alignment marks, which are formed on the different layers in the X-direction and the Y-direction, simultaneous X and Y measurements can be made, and improvement in the throughput can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, an exposure method, an alignment method at the time of exposure, and a method of forming an alignment mark used for manufacturing a semiconductor element, a liquid crystal display element and the like.

[0002]

2. Description of the Related Art In the manufacture of semiconductor elements and liquid crystal display elements, a fine pattern image formed on a photomask or a reticle (hereinafter referred to as a reticle) is coated with a photosensitive agent such as a photoresist using an exposure apparatus. Projection exposure is performed on a substrate (hereinafter, referred to as a substrate) such as a substrate or a glass plate. For the reticle pattern, for example, using a step-and-repeat type exposure apparatus, the reticle and the substrate are aligned with high accuracy (alignment).
Then, it is projected and exposed in a manner superimposed on a pattern already formed on the substrate.

In the alignment in the exposure apparatus, the circuit pattern (layer A) exposed in step A has a fine pattern in the vertical direction (Y direction), and the circuit pattern (layer B) exposed in step B is horizontal. In the case of having a fine pattern in the direction (X direction), it is preferable that the circuit pattern (C layer) in step C to be exposed next is adjusted to the A layer in the X direction and to the B layer in the Y direction. A registration method responding to such a demand is disclosed in Japanese Patent No. 2591746.
For example, as shown in FIG. 8, an X direction alignment mark 38a is formed on the A layer, and a Y direction alignment mark 38b is formed on the B layer.
By measuring 8b, the positioning of the C layer is optimized with respect to both the A and B layers.

[0004]

However, since the X-direction alignment mark 38a and the Y-direction alignment mark 38b are formed at spatially separated positions,
In order to detect the X direction alignment mark 38a and the Y direction alignment mark 38b on the substrate, it is necessary to move the substrate stage. Therefore, it hinders an improvement in throughput. The present invention has been made in view of such a problem of the related art. Even when the X direction and the Y direction are aligned using alignment marks formed on separate layers, the X and Y directions can be simultaneously adjusted. It is an object of the present invention to provide a method that enables measurement and can improve throughput.

[0005]

SUMMARY OF THE INVENTION A positioning method according to the present invention detects an alignment mark formed on a substrate in a first direction and an alignment mark formed in a second direction orthogonal to the first direction. In the alignment method for performing alignment, the alignment mark in the first direction and the alignment mark in the second direction are formed in different layers on the substrate and are close to each other so as to be within the same imaging range,
The alignment of the substrate is performed by detecting the alignment mark in the first direction and the alignment mark in the second direction. In this alignment method, the alignment marks in the first direction and the alignment marks in the second direction are formed in different layers on the substrate, and are formed close to each other so as to be within the same imaging range. The alignment measurement in the direction and the alignment measurement in the second direction can be performed simultaneously.

For example, an image of an alignment mark in a first direction and an image of an alignment mark in a second direction are captured by one image pickup device, and detection of the alignment marks in the first and second directions is performed by the same image signal. By doing so, the alignment measurement in the first direction and the alignment measurement in the second direction can be performed simultaneously. Also,
The alignment measurement in the first direction and the alignment measurement in the second direction are performed simultaneously by sequentially capturing the image of the alignment mark in the first direction and the image of the alignment mark in the second direction by one imaging device. It becomes possible. Further, when the imaging device sequentially captures the alignment mark in the first direction and the alignment mark in the second direction, the imaging device separates the alignment mark in the first direction and the alignment mark in the second direction into different gains and / or offsets. , The accuracy of the alignment measurement in the first direction and the alignment measurement in the second direction can be improved.

The method of forming an alignment mark according to the present invention comprises the steps of forming an alignment mark in a first direction on a predetermined layer on a substrate and an area without a pattern adjacent to the alignment mark; Are on different layers,
Forming an alignment mark in a second direction orthogonal to the first direction at a position overlapping a region of the predetermined layer where there is no pattern. According to this alignment mark forming method, the alignment marks in the first and second directions can be formed close to each other on the same plane. Further, when forming an alignment mark in the second direction at a position overlapping a region without a pattern of a predetermined layer, by forming an area without a pattern at a position overlapping the alignment mark of the predetermined layer in the first direction. As a result, it is possible to reliably secure the mutual alignment mark detection area.

In the exposure apparatus according to the present invention, the alignment mark in the first direction formed on the first layer on the substrate is formed on a second layer different from the first layer on the substrate. An imaging device is provided for imaging an alignment mark in a second direction orthogonal to the first direction via an objective lens. In this exposure apparatus, the alignment marks in the first direction and the second direction are captured on the same optical axis, thereby capturing the alignment marks in the first direction and the alignment marks formed in different layers. Since the substrate does not need to be moved in the X and Y directions, the throughput can be improved.

An exposure method according to the present invention comprises the steps of forming an alignment mark in a first direction on a first layer on a substrate and a region having no pattern adjacent to the alignment mark, Forming an alignment mark in the second layer in a second direction orthogonal to the first direction at a position overlapping with the pattern-free region of the first layer; and forming a third layer above the second layer. When forming, the alignment of the substrate is performed by imaging the alignment mark in the first direction and the alignment mark in the second direction through the objective lens by the imaging device. According to this exposure method, since the alignment marks in the first direction and the alignment marks in the second direction formed on different layers can be imaged without moving the substrate, the alignment marks in the first direction and the second direction can be taken. The time required for alignment can be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an example of an exposure apparatus used for the alignment method according to the present invention. Illumination light emitted from a light source 1 such as an ultra-high pressure mercury lamp or an excimer laser is reflected by a reflecting mirror 4 to a wavelength selection filter 5 side. The wavelength selection filter 5 allows only light having a wavelength necessary for exposure to pass therethrough.
Is adjusted by the fly-eye lens 6 into a light beam having a uniform intensity distribution, and reaches the reticle blind 7. The reticle blind 7 changes the size of the opening S to adjust the illumination range on the reticle 10 by the illumination light.

The illumination light having passed through the opening S of the reticle blind 7 is reflected by a reflecting mirror 8 and enters a lens system 9. The lens system 9 forms an image of the opening S of the reticle blind 7 on the reticle 10, and illuminates a desired area of the reticle 10. An image of a shot pattern or an alignment mark existing in the illumination range of the reticle 10 is formed on the substrate 12 coated with a resist by the projection optical system 11, whereby a pattern image of the reticle 10 is formed on a specific region of the substrate 12. Exposed. The substrate 12 is held on a substrate stage 13 by vacuum suction. The substrate stage 13 has a well-known structure in which a pair of blocks movable in directions orthogonal to each other are overlapped, and the substrate stage movement coordinates of a short position on the substrate 12 overlapping the exposure field of view of the projection optical system 11. Adjustment in the system is performed by substrate stage driving means 21 such as a motor. The position of the substrate stage 13 in the substrate stage movement coordinate system is detected by a laser interferometer 20 directed to a movable mirror 14 fixed to the substrate stage 13. The measured value of the laser interferometer 20 is the substrate stage control system 3
6 and the substrate stage control system 36 controls the substrate stage driving means 21 based on the information. Further, the laser interferometer 2 is transmitted from the substrate stage control system 36 to the main control system 37.
The information of the measured value from 0 is supplied and the main control system 37
Controls the substrate stage control system 36 based on the information.

The projection exposure apparatus includes, for example, a reticle alignment sensor 31 of a TTR (through the reticle) system and a substrate alignment sensor 32 of an off-axis system in order to align the reticle 10 with the substrate 12. Have been. The alignment method of the reticle alignment sensor 31 of the TTR method includes He-
An LSA method and an LIA method using a Ne laser or the like, or an exposure light alignment method using exposure light is desirable. In particular, when the projection optical system 11 for KrF (krypton fluoride) or ArF (argon fluoride) excimer laser is adopted, the wavelength of the He-Ne laser is significantly different from that of the KrF or ArF excimer laser. In order to avoid the influence of chromatic aberration of the system 11, an exposure light alignment method is preferable. In addition, when the exposure light alignment method is used, there is an advantage that there is no need to consider an offset and there is no need to manage a so-called baseline.

The reticle alignment sensor 31 determines the positional relationship (shift amount) between the alignment mark formed on the reticle 10 and a reference mark on the reference mark member 33 or the substrate 12 observed through the projection optical system 11. It is to measure. In the exposure light alignment method, the positional relationship can be directly observed by displaying the image on a monitor using an image sensor (CCD). As the alignment method of the off-axis type substrate alignment sensor 32, an FIA method is adopted. At the time of alignment, the position of the alignment mark formed on the substrate 12 is detected by using one of these alignment sensors 31 and 32, and based on the detection result, the alignment mark formed in the shot area of the substrate 12 in the previous step is formed. The pattern and the pattern on the reticle can be accurately aligned. The detection signals from these alignment sensors 31 and 32 are transmitted to the main control system 3.
The processing is performed by an alignment control system 35 controlled by the control unit 7.

On the substrate stage 13, the substrate 12
The reference mark member 33, which is flush with the reference mark member 33, is fixed,
A mark serving as a reference for alignment is formed on the surface of the reference mark member 33. By measuring this mark, the reference position of both alignment sensors 31, 32 can be determined. The substrate stage control system 36 receives the alignment result from the main control system 37, controls the substrate stage driving means 21 based on the result, and exposes the shot. Next, a method for forming a substrate alignment mark used for alignment according to the present invention will be described.

FIG. 2 is a diagram showing an example of an alignment mark for implementing the present invention. The mark shown in FIG. 2A is an X measurement mark 4 formed on the substrate 12 of FIG.
0, which is composed of an alignment mark 40a in the X direction and a region 40b having no pattern. These are formed at the same time as the pattern formation of the layer A in the step A shown in FIG. 3, for example. The mark shown in FIG. 2B is a Y measurement mark 41 on the substrate 12, and is composed of an alignment mark 41a in the Y direction and an area 41b having no pattern. These are formed at the same time as the pattern formation of the layer B in the step B shown in FIG. 3, for example. And
The pattern of the C layer in the process C is the X layer formed on the A layer.
The X- and Y-direction alignment (alignment) is performed using the X-direction alignment mark 40a of the measurement mark 40 and the Y-direction alignment mark 41a of the Y measurement mark 41 formed on the B layer, and then exposure is performed.

Here, the area 40b of the pattern X of the X measurement mark 40 formed on the layer A in the step A is located immediately below the Y direction alignment mark 41a of the Y measurement mark 41 formed on the layer B thereon. I do. Therefore, B
Since the Y-direction alignment mark 41a of the layer is formed above the pattern-free region 40b of the layer A, it is not affected by the pattern shape formed on the layer A, and it is possible to form a mark without distortion. it can.

The X measurement mark 40 formed on the A layer
Immediately above the X-direction alignment mark 40a, an area 41b where there is no pattern of the Y measurement mark 41 of the B layer is located. Therefore, the X direction alignment mark 40 of the A layer
a is not processed and crushed by the process for forming a pattern on the B layer. To elaborate,
The resist (photosensitive agent) applied on the substrate 12 includes a positive resist in which exposed portions are removed by development and a negative resist in which unexposed portions are removed by development. Blank portion of alignment mark formed on reticle 10 [blank portion of FIG. 2 (a) or FIG. 2 (b)]
Is performed so that the resist remains on the substrate 12 as exposure or non-exposure depending on the type of the resist. By doing so, it is possible to prevent the X-direction alignment mark 40a formed of the layer A from being processed by etching, vapor deposition, or the like. In addition, if no resist remains in the blank part due to the type of processing process, a protective film is formed on that part, and when processing is performed later, a reticle that removes the resist without processing the mark Is used. Thus, the mark formed in the previous step can be protected.

These X-direction alignment marks 40a
And the Y-direction alignment mark 41a are formed close to each other in the X-direction.
2 can be simultaneously entered into the field of view and measured simultaneously. FIG. 4 is a diagram showing another example of the alignment mark according to the present invention. In this example, the X-direction alignment marks 40a are located on both sides of the Y-direction alignment marks 41a as two spatially separated marks. The X-direction alignment marks 40a on both sides of the Y-direction alignment marks 41a are, for example, formed on the layer A in FIG.
1a is formed in the layer B of FIG. Thus, the X-direction alignment mark 40
The “a” and the Y-direction alignment marks 41 a are formed in separate layers so that the entirety is within the field of view of the substrate alignment sensor 32.

Also in the example shown in FIG. 4, Y formed in the B layer
A region of the layer A overlapping the direction alignment mark 41a, that is, a region between two X-direction alignment marks 40a of the layer A formed separately is a region having no pattern. Similarly, a region of the layer B overlapping the X-direction alignment mark 40a formed on the layer A, that is, a region on both sides in the X direction of the Y-direction alignment mark 41a is a region having no pattern. In this way, by setting the position of the other layer overlapping with the respective alignment marks 40a and 41a as a region without a pattern, the alignment patterns 40a and 41a formed on separate layers can be used for processing other layers. Collapse is prevented.

In FIG. 4, the lengths and numbers of the X-direction alignment marks 40a and the Y-direction alignment marks 41a are the same for convenience of explanation, but the lengths and numbers can be changed as appropriate. Furthermore, the case where the X-direction alignment mark 40a is divided so as to be positioned on both sides of the Y-direction alignment mark 41a is described.
It can be located on both sides of the direction alignment mark 40a. Further, the dividing position is not limited to the left and right as in this example, but may be the upper and lower positions.

Returning to FIG. 1, the substrate alignment sensor 3
The X-direction alignment mark 40a and the Y-direction alignment mark 41a are simultaneously captured by one of the two CCD cameras 2 and image-processed, whereby the X-direction position and the Y-direction position of the substrate 12 can be known. At this time,
The X-direction alignment mark 40a and the Y-direction alignment mark 41a may be captured and detected at the same time, but two types of marks, such as capturing the X-direction alignment mark 40a first and then capturing the Y-direction alignment mark 41a, may be used. Can be sequentially captured and processed. When two types of marks are sequentially taken in, the gain and offset of the signal processing system can be separately set when detecting each of the marks 40a and 41a, so that more accurate detection becomes possible.

FIG. 5 is a schematic view showing another example of the exposure apparatus according to the present invention. In this exposure apparatus, the X-direction alignment mark 40a and the Y-direction alignment mark 41a are taken in by different CCD cameras 50 and 51 to perform alignment. In FIG. 5, portions having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and detailed description thereof will be omitted. The illumination light from the off-axis microscope illumination system 52 is reflected by the half mirror 54 and applied to the X measurement mark 40 and the Y measurement mark 41 on the substrate 12. The reflected light of the X measurement mark 40 from the X direction alignment mark 40a is guided to the X measurement CCD camera 50 side, and the X direction alignment mark 40a is imaged and detected. Is reflected by the half mirror 53 and is reflected by the CC for Y measurement.
Guided by the D camera 51, the Y-direction alignment mark 41
a is detected.

At this time, the focusing of the two CCD cameras 50 and 51 is performed as follows. First, for example, a CCD camera 50 for imaging the X-direction alignment mark 40a
Is in the best focus state and the X direction alignment mark 4
The substrate stage 13 is moved in the Z direction so that 0a can be detected. Next, while the Z-direction position of the substrate stage 13 is fixed, the CCD camera 51 for imaging the Y-direction alignment mark 41a is moved in the optical axis direction so that the Y-direction alignment mark 41a can be detected in the best focus state. Move and adjust. By adjusting the focus of the two CCD cameras 50 and 51 in this manner, the detection of the X measurement mark 40a and the Y measurement mark 41
a can be detected with high accuracy.

FIG. 6 is a block diagram showing an example of a control system of the CCD camera 50 for X measurement and the CCD camera 51 for Y measurement in the substrate alignment sensor 32. CCD camera 50 for X measurement and CCD camera 5 for Y measurement
1 is provided with CCDs (image pickup devices) 50a and 51a, respectively. The operation of capturing the patterns by the CCDs 50a and 51a is controlled by the control unit 58.
As described with reference to FIG. 3, since the X-direction alignment marks 40a are provided on separate layers such as the A-layer and the Y-direction alignment marks 41a are provided on separate layers, the reflectivity of each layer is different. CCD50
Light intensity and contrast of the images formed on a and 51a may be different. Therefore, the gains of the AGC circuits 50c and 51c provided after the CCDs 50a and 51a are separately set.

The analog image signal whose gain is controlled by each of the AGC circuits 50c and 51c is A / A
The signal is converted into a digital signal by the D converter 55. The image signal, which is a digital signal,
Only frames are accumulated. When the image signal stored in the memory 56 is subjected to image processing by the image processing unit 57, the control unit 58 measures the X-direction alignment mark 40a or the Y-direction alignment mark 41a.
The control unit 58 performs feedback control on the operations of the AGC circuits 50c and 51c, and always sets the AGC circuits 50c and 51c in an optimal state.

Here, the X direction alignment mark 40a or the Y direction alignment mark 41a
The mark measurement accuracy can be improved by using different algorithms for measuring the X direction alignment mark 40a and the Y direction alignment mark 41a. For example, when detecting the position of the X-direction alignment mark 40a or the Y-direction alignment mark 41a, when performing edge processing on the one-dimensional signal integrated in the non-measurement direction, the slice level and the slice level of the first derivative are changed. Different values can be used for the X measurement and the Y measurement, or different templates can be used when performing the correlation processing.

Here, the substrate stage 13 and the CC
By moving the D camera 51, the CCD cameras 50 and 51 are moved.
Was adjusted, but if the CCD cameras 50 and 51 themselves have a focus adjustment function,
By independently adjusting the focus of the camera, the X-direction alignment mark 40a and the Y-direction alignment mark 41a formed on different layers can be detected in the best focus state.

FIG. 7 is a block diagram showing a control system of the CCD camera 50 for X measurement and the CCD camera 51 for Y measurement in that case. The control system shown in FIG.
b, 50c, and the controller 58 controls the focus circuit 50
It differs from the control system of FIG. 6 in that the control of b and 50c is performed.
As described above, the X-direction alignment marks 40a and the Y-direction alignment marks 41a are provided on different layers, and have different focal lengths for each mark. In this example, focus circuits 50b and 51b controlled by the control unit 58 are provided to adjust the focus. Therefore, the X-direction alignment mark 40a and the Y-direction alignment mark 41a can be respectively detected in the best focus state.

[0029]

According to the present invention, simultaneous X and Y measurement can be performed even when the X direction and the Y direction are aligned using alignment marks formed on different layers, respectively, and the throughput can be reduced. Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an exposure apparatus according to the present invention.

FIG. 2 is a diagram illustrating an example of a method for forming a substrate alignment mark used for alignment according to the present invention.

FIG. 3 is a schematic sectional view showing an example of a method for forming a substrate alignment mark used for alignment according to the present invention.

FIG. 4 is a diagram showing another example of a method for forming a substrate alignment mark used for alignment according to the present invention.

FIG. 5 is a schematic view showing another example of the exposure apparatus according to the present invention.

FIG. 6 is a block diagram showing an example of a control system of the substrate alignment sensor.

FIG. 7 is a block diagram showing another example of the control system of the substrate alignment sensor.

FIG. 8 is a schematic cross-sectional view showing a state of forming a conventional X, Y alignment mark.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source, 4 ... Reflection mirror, 5 ... Wavelength selection filter, 6 ... Fly eye integrator, 7 ... Reticle blind, 8
... reflecting mirror, 9 ... lens system, 10 ... reticle, 11 ... projection optical system, 12 ... substrate, 13 ... substrate stage, 14 ... moving mirror, 21 ... substrate stage driving means, 20 ... laser interferometer, 31 ... reticle Alignment sensor, 32: substrate alignment sensor, 36: substrate stage control system, 37
... Main control system, 40... X measurement mark, 40 a... X direction alignment mark, 40 b.
Y measurement mark, 41a... Y direction alignment mark, 4
1b: area without pattern, 50: CCD camera for X measurement, 50a, 50b: CCD (imaging device), 50b,
51b: focus circuit, 50c, 51c: AGC circuit, 51: CCD camera for Y measurement, 52: illumination system for off-axis microscope, 55: A / D converter, 56: memory, 57: image processing unit, 58 ... Control unit

Claims (8)

[Claims] 1. An alignment method for aligning a substrate by detecting an alignment mark formed on a substrate in a first direction and an alignment mark in a second direction orthogonal to the first direction, the method comprising: The alignment mark in the first direction and the alignment mark in the second direction are formed on different layers on the substrate and are close to each other so as to be within the same imaging range, and are aligned with the alignment mark in the first direction. The second
The alignment of the substrate by detecting an alignment mark in the direction of (b). 2. An image of the alignment mark in the first direction and the alignment mark in the second direction is captured by one imaging device, and the alignment marks in the first direction and the second direction are received by the same image signal. 2. The positioning method according to claim 1, further comprising: 3. An image of the alignment mark in the first direction and an image of the alignment mark in the second direction are defined as one image.
2. An image pickup device according to claim 1,
The alignment method described. 4. The image pickup apparatus according to claim 1, wherein when sequentially taking the alignment mark in the first direction and the alignment mark in the second direction, the alignment mark in the first direction and the alignment mark in the second direction. 4. The method according to claim 3, wherein imaging is performed with different gains and / or offsets. 5. A step of forming, in a predetermined layer on a substrate, an alignment mark in a first direction and an area without a pattern adjacent to the alignment mark, and forming the alignment mark on a layer different from the predetermined layer. Forming an alignment mark in a second direction orthogonal to the first direction at a position overlapping a region where the pattern does not exist in the layer. 6. When forming an alignment mark in the second direction at a position overlapping the region without the pattern on the predetermined layer, a pattern is formed at a position overlapping the alignment mark in the first direction on the predetermined layer. 6. The method according to claim 5, wherein a region having no gap is formed. 7. An alignment mark in a first direction formed on a first layer on a substrate, and a first direction formed on a second layer different from the first layer on the substrate. An exposure apparatus comprising: an image pickup device that picks up an alignment mark in a second direction orthogonal to an image via an objective lens. 8. A step of forming an alignment mark in a first direction and a region without a pattern adjacent to the alignment mark on a first layer on a substrate, and forming a second layer different from the first layer on the second layer. Forming an alignment mark in a second direction orthogonal to the first direction at a position overlapping with the pattern-free area of the first layer; and forming a third layer above the second layer. When forming, the alignment mark in the first direction and the second
An exposure method characterized in that the substrate is aligned by imaging an alignment mark in the direction of (1) through an objective lens.