JPS5989418A - Method for detection of pattern - Google Patents

Abstract

PURPOSE:To search for a positioning pattern in a short searching period by a method wherein the visual field of detection is relatively shifted in succession toward the circumferential part from the position initially set for an object. CONSTITUTION:A retrieval driving is performed here in such a manner that an objective lens system searches for a mark while it is being spirally shifted from the initially set position A on the mark in the order of points A P Q R S ... and so on, and the mark is detected on the route from points U to V. As the probability wherein the mark is present is generally high in the vicinity of point A, the time required for detection can be made short. Besides, at the starting point of operation, the objective lens system is to be set at the same position at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for aligning two objects, and in particular for aligning a mask and a wafer prior to printing a semiconductor integrated circuit pattern on the mask or reticle onto the wafer. Suitable for this equipment.

The semiconductor manufacturing process includes a step of sequentially transferring several patterns onto a wafer to form a semiconductor integrated circuit. In this case, in order to accurately position another pattern on the wafer onto which the previous pattern has already been transferred, it is necessary to align the mask with the pattern and the wafer with high precision. And this 9 alignment is
Normally, alignment marks written on the mask and wafer are photoelectrically detected and automatically achieved using the detected signals.

On the other hand, recently there has been a rise in the number of mask carriers that automatically attach the mask in the mask carrier to the mask set position.
A device equipped with a change mechanism is known. This mechanism requires a preliminary positioning function (referred to as mask alignment) to accurately set the mask at a predetermined position on the printing stage.

By the way, during alignment, if one alignment mark is not within the detection observation field of the detection device, first move the stage 1 holding the wafer or mask or the detection optical system so that the alignment mark is included in the detection field of view. Explore. The conventional method for this search is to move the stage or detection optical system to the boundary of the search range, and then sequentially search within the search range from there.

However, in this method, it takes time to move the stage or the detection optical system to the boundary position (for example, stages are excellent at fine movements for precise positioning, but are not suitable for rapid movements), and It takes time to search from the peripheral area where the probability of a mark existing is low (even if there is a mechanical setting error, the probability of a mark existing is higher the closer to the set position determined by design). There are some difficulties.

An object of the present invention is to search for an alignment pattern in a short search time when the alignment pattern does not exist within the detection field of view in an initial state.

Embodiments of the present invention will be described below with reference to the drawings, with FIG. 1 showing the external appearance. 1 is a mask with an integrated circuit pattern, and other mask alignment marks and mask/
It shall have a wafer alignment mark. Reference numeral 2 denotes a mask stage that holds the mask 1 and moves the mask 1 in a plane and in a rotational direction. 3 is a reduction projection lens, 4 is a wafer provided with a photosensitive layer, and is provided with a mask/wafer alignment mark and a wafer alignment mark. 5 is a wafer stage. The wafer stage 5 holds the wafer 4 and moves it in the plane and in the rotational direction, and it has one wafer stage.
Move between the printing position (inside the projection needle) and the TV/UNINO alignment position. 6 is the objective lens of the TV wafer alignment river detection device, 7? -J: p-tube or solid-state image sensor; 8 is a television receiver for video observation;

9 is a binocular unit that displays the wafer 4 through the projection lens 3;
useful for observing the surface of 10 is an upper unit that houses an illumination optical system for converging the mask illumination light emitted from the light source 10a and a detection device for mask/wafer alignment. The wafer stage 5 holds the wafer transported by a wafer transport means (not shown) at a predetermined position, and first moves to a position where the alignment mark on the wafer is within the field of view of the television wafer alignment objective lens 6. This 1 o'clock positional accuracy is due to mechanical alignment accuracy, and the field of view of the objective lens 6 is approximately 1 mm to 2 mm in diameter. The alignment mark in this field of view Wj is detected by the image pickup tube 7, and the alignment mark from there is detected using a reference mark for TV/wafer alignment (described later) provided in the optical system for TV/wafer alignment as a reference. A coordinate position t is detected. On the other hand, since the detection position for auto alignment of the projection optical system and the position of the reference mark for TV/wafer alignment mentioned above are set in advance, the auto alignment position can be determined from the coordinate position of these two points and the TV/wafer alignment mark. The infeed leaf of wafer stage 5 is determined.

Position detection accuracy for TV/wafer alignment is ±5μ
It is approximately ±10 μm even when taking into consideration the error caused by the movement of the wafer stage from the TV/wafer alignment position to the mask/wafer alignment position.

Therefore, alignment only needs to be performed within a range of approximately ±10μ,
This range is less than 1/1oo of the field of view of conventional alignment, and alignment can be performed faster than conventional alignment. The TV/wafer alignment will be explained later.

FIG. 2 t, t shows an embodiment for achieving mask alignment and mask-to-wafer alignment. In the figure,
The mask 1, the reduction projection lens 3, the wafer 4, and the wafer stage 5 are generally υ in FIG. ] The shadow lens 3t is shown schematically as an anchor for convenience. 11 and 11' i, t mask alignment marks, which are carved in immovable locations such as lens barrels or parts of the device.

On the other hand, at the position indicated by 20.2σ on the mask 1, there is a 45"
An alignment mark in the form of a line or slit arranged at an angle is provided. Also, 21 on wafer 4
．． The positions indicated by 2r are numbered 71, 72, 73 in Figure 3.
, 74 are provided in the form of lines or slits, which are arranged at an angle of 45 degrees with respect to the running staff line 60. Normally, positioning is performed using signals from both the left and right observation systems.

Note that the alignment mark on the mask L and the alignment mark on the wafer do not change in size even if a system other than the same-magnification projection system is used, even when projected or L back-projected. The size of the alignment mark is changed in advance, and the size is set so that the reduction magnification is obtained by dividing the size of the wafer alignment mark by the size of the alignment mark of the t mask.

Returning to FIG. 2, 22 is a laser beam, and 23 is an optical deflector such as an acousto-optic device. Optical deflector 23 The direction of light emission is switched between upward, horizontal, and downward in response to a switching signal from outside. Reference numerals 24 and 25 each designate a convergent cylindrical lens, which are arranged so that their fJ helixes are perpendicular to each other, and have the function of converting the cross-sectional shape of the laser beam into a linear shape.

26 and 27 are trapezoidal prisms, which have the function of refracting the light deflected upward and downward by the optical deflector 23 in opposite directions. 2
It is a rotating polygon mirror (polygon) that rotates around 8-digit rotation I (29).

The laser beam 30 emitted from the laser light source 22 becomes a slit-shaped light IQ 30 a that travels through the cylindrical lens 24 and the prism 26 depending on the state of the optical deflector 23.
, a slit-like line 30b1 passing through the cylindrical lens 25 and the prism 27, or a straight spot-like nine-line line 30c, but in any case, a point on the surface of the rotating polygon mirror 28 It converges to 31. 32.3
3. 34 is an intermediate lens, 35 is an optical path splitting mirror, 36 is a no-f mirror that forms the visual observation and observation system 37, 3B,
Lens 37 is an eyepiece that forms an image of the unino 1-plane. 39 is a half mirror forming an illumination system 40 and 41 that does not require visual observation, 40 is a condenser lens, and 41 is a lamp. 42 is a photoelectric detection system 43, 44, 45.4
A half mirror forming 6, 43F-1 mirror, 44
is a lens, 45 is a spatial filter, 46 is a condenser lens, and 47 is a photodetector. 48.49°50
．． 51 is a total reflection mirror, 52 is a prism, and 53 is f-θ
It is an objective lens. 5. These are the positions of the 7 alignment patterns for mask alignment provided on the N'i mask 1.

As shown in Figure 2, the No. 1EI detection system consists of completely symmetrical left and right systems.If the operator side is on the front side of the page, the system shown with a dash will detect signals on the right, and the system without a dash will detect signals on the left. Let's call it a system.

The intermediate lenses 32, 33, and 34 form the origin of the deflection from the rotating polygon mirror 28 at the pupil 56 in the aperture position 55 of the objective lens 53. Therefore, the laser beam scans the mask and the wafer by the rotation of the rotating polygon mirror 28. Also, in the objective lens system, the objective lens 53, the aperture υ55
, the mirror 51 and the prism 52 are movable in the XY directions by a moving means (not shown), and the observation and measurement positions of the mask 1 and wafer 4 can be changed arbitrarily. For example, when the mirror 51 moves in the direction indicated by arrow A in the X direction, the objective lens 53 and the aperture 55 simultaneously move in the A direction, and in order to keep the optical path length constant, the prism 52 also moves in the A direction. The mirror 51 is moved by 1/2 of the amount of movement.

On the other hand, when moving in the Y direction, the entire optical system for observation and position detection moves in the Y direction (direction perpendicular to the plane of the paper).

The scanning beam 61 of the optical path 30a that reds and whites the cylindrical lens 24 forms an angle θ=45'' with respect to the scanning axis 6o,
It is parallel to the mark 71, 72, 75. When scanning in this state, the photodetectors 47 and 47' are shown in Figure 3 (''3).
S, 1°S as shown in ? S+ sty signal is obtained O By+ I sts I 8? ! are signals corresponding to the alignment marks 71 and 75172, respectively.

Further, even if there is minute dust on the scanning surface, unlike the case of a spot beam, it is averaged and is not practically detected as an output.

On the other hand, the optical path 30b passing through the cylindrical lens 25
Since the scanning beam 62 is inclined θ=-45'' with respect to the scanning axis 60 and is parallel to the marks 73, 74, and 76, the detection signal becomes S5°S?11+S?4 in FIG.

Therefore, the detection signal 871 t 89!1 + stt t
By measuring the interval sys + 5ell r s, it is possible to detect - in the misalignment between the mask and the wafer, and when they match, the intervals of the detection signals become equal.

Incidentally, the present applicant has proposed Japanese Patent Application Laid-Open No. 53-90872 or Special RAll'B53-91754J14', t-) Ajiiment.

The alignment of the alignment mark 20 on the mask 1 and the 7 alignment mark 21 on the wafer surface, that is, the mask-wafer alignment, has been explained above using the Y62 diagram and FIG. With an optical system and an alignment mark of the same shape, the alignment mark 54 on the first surface of the mask and the mask reference mark 11 supported by means not shown in the lens mirror #3 are aligned, that is, the mask alignment is performed. be. In this case, as described above, the objective lens 53.111155 and the mirror 51
, and the prisms 52t and i move in the incoming direction to the mask reference mark 110 [in FIG. 2] to perform alignment.

The pattern for mask alignment is the pattern shown in the third numbering 71, 72° 73.74 for the mask reference mark 11, and the pattern shown as U number 75° 76 in Figure 3 for the alignment mark 54 of the mask 1. Alignment marks are provided.

Therefore, in mask alignment, the mask and mask reference mark are aligned in exactly the same way as mask-wafer alignment, and the mask is set at a predetermined position with respect to the lens 3.

In the case of mask alignment, since the reduction projection lens 3 is not used, the alignment mark 54 and the mask reference mark 11 on the mask surface may be patterns with the same magnification.

Since a reduction projection optical system is used in the one-sided printing process using a stepper and a wafer, it is usually the mask stage (which holds the mask) that moves for positioning during wafer alignment. Figure 1 2)
It is. On the other hand, also in mask alignment, the mask stage moves to perform positioning. Therefore, in any case, the shifting mask 11) is provided with a two-line pattern 75, 76, but this is only one embodiment of the present invention, and a four-line pattern is provided on the mask side. Pattern 71.72
, 73, 74 may be provided, and the number of patterns on the mask may be different between mask alignment and wafer alignment, and there is no limitation on pattern selection.

Next, the method of mask alignment will be explained in detail.

In mask alignment, the mask is transported from the mask change mechanism to the mask stage by means not shown,
(W is held, but at this time (valve setting), since it is done mechanically, the degree of control is low, and an error of several 100 μm occurs.

1. When the field of view of the objective lens is narrowed, it is not always the case that the mask alignment mark will be placed within the field of view, that is, within the scanning range of the laser beam. Even if it is at the end, the alignment mark on the mask may fall out of the field of view due to an error when setting the mask. In that case, the number 41M-sy+ I S in Figure 2■3 (I())
□, S□+5tab not detected NE)yv l 8
18 signals are not detected, so auto-alignment is not achieved.

In such a case, a process of searching for the mark on the mask is required, but in the conventional example, the stage holding the mask moves from the 1st wafer to the 1st wafer, and the stage holding the mask moves while repeating so-called imitation driving. I've been searching for Mark.

In order to make the explanation of 11.
An example of lIb will be explained with reference to FIG.

The figure depicts the locus of the objective lens when searching for an alignment mark on a mask or wafer surface. However, in reality, instead of moving the objective lens in the X and Y directions, it is preferable to move the stage holding the mask or wafer, but for convenience of explanation, the objective lens is moved here. It is assumed that the lens is transported to position A (FIG. 4), which is approximately below the objective lens 53, by the transport means (position A is referred to as the initial setting position).

However, if there is an error in the mask settings and the length of the beam scanning range and the length T (see Figure 3) are not large enough to include the setting error, mark M at the position of
is not detected, the objective lens moves to the boundary of the groping drive range, starts groping drive from point B, and moves from B-+C to D.
Search for marks while moving →E... In this example, mark M is detected during the third round trip to J-.

The following difficulties can be pointed out in the conventional example described above.

(1) Even though the probability that the mark exists is high near point A, it moves to point B in the boundary area where the probability of existence Q is low, and the search starts from point B, so it takes a long time to detect the mark. .

(2) Since the stage is generally driven at low speed and with high precision, when searching for an alignment mark for alignment of a mask, etc., it takes time to move the stage and the detection time becomes long.

In the embodiment described later, the following configuration is adopted, so that the mark detection time can be shortened.

(1) A search is performed from the periphery of the initially set position of the objective lens toward the boundary area.

(2) More preferably, during the groping drive, the stage is identified, the objective lens in the X direction, the aperture, and the optical
The prism 52 constituting the trombone is moved, and the entire scanning optical system 22 to 55 is moved in the Y direction. Generally, the stage is required to have the most precise positioning, so the transport mechanism must have a structure that meets this requirement. Therefore, it is not suitable for moving the stage at high speed.

FIG. 4 Tl3) t shows the trajectory of the frugal drive according to the embodiment of the present invention. Here, the objective lens system moves from the initial setting position A over the mask A −+ p −+ Q→R→S→...
Search for the mark while moving in a spiral pattern, in this example, from U to ■
Mark M is detected on the route to . Since the probability of the presence of a mark is generally higher near point A, there is an advantage that the time required for detection is short. Furthermore, at the starting point of operation,
It is assumed that the objective lens system is always set at the same position.

FIG. 5 shows a flow diagram showing movement of the objective lens system. When the groping drive starts at 501, an X-direction movement counter and a Y-direction movement counter are first cleared at 502. These two counters are counters that determine the amount of movement of the objective lens in the X and Y directions (the X and Y directions are shown in FIG. 4 (3)). Next, in step 503, a limit check is performed to determine whether the boundary in the X direction of the groping drive has been reached, and if it is within the limit, the content N of the X direction movement counter is incremented in step 504.

If the limit is reached through the wound or this loose, as described later, 504 is jumped and 503 to 505 is reached.
Move to. In step 505, movement is performed in the positive direction of X, and the amount of movement at this time is, for example, Fj:, , T x N.

(T is the laser scan IJ as shown in Figure 3)
Here, in the first loop, in Figure 4 (Il
A movement from A to P, indicated by l, is performed.

If a predetermined amount of movement has been performed in the X direction, then (c) a limit check is performed in the Y direction at 506, and if it is within the limit, the content of the Y direction movement zb counter is checked at 507, as in the X direction. is incremented, and if the limit has been reached, the process in step 507 is jumped and step 508 is performed. 508 is (
→Move in the Y direction by an amount of 1,×M (Ll-j: laser scan length shown in Figure 3) 0 Same 4.・To p←) Process 509.5]0.511 in the X direction, then process 512%513.514 in the Y direction. Next, it is checked in 515 whether the limit of the groping drive has been reached in both the EX direction and the Y direction, and if it has been reached, the process ends in 516, and if there is still some drive area left, the process jumps to 503 again, and as described above. Repeat the loop until it reaches the limit 0 Here, the amount of movement in the X and Y directions is explained using the symbols in Figure 4 (B).・・・
・Ashi, again, candy is twice as bad as bad, and W is three times as bad as bad. Therefore, AP is applied once each in the X direction and Y direction,
The amount increases by PQ, and this amount is counted by an X-direction movement counter and a Y-direction movement counter. Furthermore, the amounts of R and PQ depend on the laser scan width T and laser scan length, respectively.

W, the situation in which any direction in Figure 4 (■3) has reached the limit is, for example, taking the (-) Y direction as an example, W-+ in the figure.
In the state indicated by Z, the amount of movement is the same as the previous movement W→2. This step corresponds to performing the process 70- from 506 to 507 by skipping the process 507 in the flow diagram of FIG.

Note that the example explained here is a method of searching in which two alignment patterns 75 and 76 on the mask are always detected. For example, after first detecting one of the above-mentioned patterns, If you find a way to detect books, the pitch of the groping drive may be rough. That is, the length and length may be longer than T and L, respectively, and therefore the amount of movement of the groping drive is not particularly limited to the amount described above.

Next, the interlocking and independent driving of the right objective lens system and the left objective lens system, which are other advantages of the present invention, will be described.

The explanation of the operation in Figures 3 and 4 was given for the objective lens system on one side, but in reality, as shown in Figure 2, the alignment mark groping drive is performed using both the left and right objective lens systems. . In this case, there are two modes: a mode in which the objective lens systems on both sides are driven in conjunction with each other, and a mode in which they are driven independently, and the desired one of both modes can be selected.In the case of 〇, the time to detect the alignment mark will be explained later. Although the length is slightly longer on average than in the case of independent drive, the operation of the objective lens system and its control are linked, so the apparatus itself is simple.

On the other hand, in the case of independent drive, for example, the objective lens on one side is driven clockwise as shown in Figure 4 (FBl), and the other objective lens system is driven as shown in Figure 4 (C). By performing the groping drive in a counterclockwise direction, the operation is slightly more complicated than the interlocking drive, but the average time to detect the alignment mark is shortened.

The present invention resides in that the interlocking drive mode and the independent drive mode can be selected as necessary. An example of a combination of these is a method in which first, interlocking driving is performed near the initial position of the objective lens system, and independent driving is performed toward the periphery.

Another example is a method in which interlocking driving is performed until one pattern of alignment marks is detected, and then independent driving is performed after detection, so that both objective lens systems detect four patterns. . This method is particularly effective when the drive pitch of the aforementioned groping drive is rough, or when there is a shift in the mask in the θ direction.

Next, we will discuss the selection and use of the beam shape of the Sugyan beam. As explained in FIG. 2, the laser beam 3o does not pass through the cylindrical lenses 24, 25, but uses the optical path 30c in which it travels directly if. In the case of rays, the beam t does not have the inclination characteristic like the so-called spot-like 'fL cislit ray, so the pattern 71.72.7
Signals can be obtained for any of 3.74.75.76. In particular, this method requires sufficient light intensity and
Although this method is effective in mask alignment with a good S ratio, it can also be used in mask-wafer alignment without being limited thereto. Alternatively, for example, in mask alignment, a spot beam is used until 4 lines on the mask, or a total of 6 lines of 4 trees and two reference marks on the mask are detected, and then a slit beam is used for scanning. You may also use a method of switching in the middle of the process.

By doing so, complicated control is not required, and highly accurate alignment can be achieved using the sheet-shaped beam.

The advantage of Tsumasinin's method is that it provides a structure that generates both sheet-like beams and spot-like beams, and that they can be selected depending on the object.

Next, the positioning of the mask after the objective lens is groped will be described using FIG. 4 (13).

When the mask alignment mark on the mask is detected by the groping drive as described above, the objective lens position M can be easily determined from, for example, the movement of the reference mark 51 degrees from the position A.

Therefore, next, the objective lens system (52 to 53) is returned from position M to position KA, and the mask stage 2 is also moved from M to direction A. When the movement is completed, both the i-frame reference mark and the mask alignment mark can be observed within the congratulatory needle of the objective lens, resulting in the state shown in FIG. 3(A). In this state, 6 alignment signals can be detected, so 6 alignment signals can be detected.
Alignment can be performed with the 4F1 interval of the book on the needle side. Next, the detection device for TV/wafer alignment will be explained using FIG. 6.

In the figure, a reduction projection lens 3, a wafer 4, an objective lens 6,
The image pickup tube 7 is the same as in FIG. On the other hand, the 91 illumination light source uses, for example, a halogen lamp. 92 is a condenser lens.

93A and 93B are a bright field diaphragm and a dark field diaphragm that can be attached and detached interchangeably, and in the figure, the bright field diaphragm 93A is installed in the optical path. Condenser lens 92 images light source 11 onto a bright field aperture. 94 is a relay lens for illumination, and 95 is a cemented prism.The cemented prism 95 has a function of making the optical axis of the illumination system and the optical axis of the light receiving system coaxial, and includes an inner reflective surface 95a and a transflective surface 1fii 95b. I can do it. Jinkode light source 91
, condenser lens 92, bright or dark field iJ 93A
and 93B1 illumination relay lens 94, cemented prism 95
, the objective lens 6 is an illumination system)'It L, the speed of light exiting the objective lens 6 epi-illuminates the wafer 6.

1 stamp Next, 96 is a relay lens, and 97t is a mirror that passes the optical path.

98 is a glass plate having a reference mark for TV/wafer alignment, and the reference mark has the function of providing the origin of coordinates. Therefore, the wafer 1 alignment mark is
It will be detected as a coordinate value and a Y coordinate value. 9
Reference numeral 9 denotes an imaging lens, which includes the above-mentioned cemented lens 95, relay lens 96, fi 97, glass plate 98, and f-elephant lens 9.
9 constitutes a light receiving system together with the image pickup tube 7, and an objective lens 6
The optical path passing through is reflected by the inner reflective surface 95a of the cemented prism, is reflected by the semi-transparent surface 95b, and is reflected again by the inner reflective surface N5a toward the relay lens 96. The wafer alignment mark image on the wafer 4 is transferred to the image pickup tube 7 together with the IA quasi-mark image formed on the glass plate 98 having the fiducial mark.
The image is formed on the imaging plane.

←Explain the effect. The luminous flux from the illumination light source 91 is converged by the condenser lens 12, illuminates the aperture of the bright field diaphragm 93A or the dark field diaphragm 93B, further passes through the illumination relay lens 94, and is transmitted through the semi-transparent surface 95b of the cemented prism. The light is reflected by the reflective surface 95a and illuminates the wafer 4 through the objective lens 6.

The light beam reflected from the surface iii of the wafer 4 is subjected to an imaging action by the objective lens 6, enters the cemented prism 15, and is reflected by the reflecting surface 9.
5a, then reflected by the semi-transparent surface 95b1 reflecting surface 15a and emitted, relayed by the relay lens 96, reflected by the bell 97, imaged on the glass plate 98, and then imaged by the imaging lens 99. An image is formed on tube 7. At that time, as described above, with the bright field number 93A inserted, the moth is imaged of the reference mark on the glass plate 98, and using that image, the points to be added to the camphor tree are determined, and then the number is switched to the dark field number 1. The wafer alignment mark image is made clearly visible, and the position of the wafer alignment mark φ is detected by capturing the image. Then, depending on the presence of the wafer alignment mark detected by electrical processing, the wafer stage 5 moves and stops so that the wafer 4 occupies a prescribed position 4' in the projection field of the projection lens 30.

The wafer 4 may be once aligned in a standard position and then moved into the projection center.

As described above, the present invention eliminates the need for search preparation time and allows the search work to proceed effectively, reducing wasted work time. The place that benefits you is the dog.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an apparatus according to an embodiment of the present invention. figure. FIG. 4) is a plan view for explaining the operation of the conventional example. FIGS. 4(F3) and 4(C') are plan views for explaining the operation of the embodiment. FIG. 5 is a flow diagram showing the operation of the groping drive. Fig. 6 (Co-Wafer Alignment) 4-point view showing 1. In the figure, 1 is a mask, 2 is a mask stage, 4 is a reduction projection lens, 4 is a wafer 1.5 is a wafer stage,
6 is an objective lens, 7 is an image pickup tube, 8 is a television receiver, 11
is a fixed mask alignment mark, 22 is a laser light source, 23 is a light director, 24 and 25 are cylindrical lenses, 26 and 27 are prisms, 2B is a rotating polygon mirror, 5 is an objective lens, 52 is a prism, 71・72・76・7
4 is a process for configuring the wafer side alignment mark/
1, 75 and 76 are elements constituting mask-side alignment marks, a person is an initial setting position, and M is an alignment mark. Applicant Canon Co., Ltd. Mi11 Tsuroza

Claims (1)

[Claims] (1) In a device comprising a detection means having a predetermined detection field of view and a means for moving an object having a predetermined pattern, the detection field and the object having the pattern are relatively moved. A pattern detection method characterized in that when a pattern is included in a detection field of view, the detection field of view is sequentially moved relative to the object from a position initially set toward the periphery. Q) The pattern detection method according to claim 1, wherein the locus of sequential relative movement is spiral. (6) The pattern detection method according to claim 1, wherein the object having the predetermined pattern is fixed and the detection field of view is moved.