JPH03108315A - Wafer periphery exposing method - Google Patents

Abstract

PURPOSE:To improve exposure position precision by performing exposure while the shutter operation is controlled by the rotation angle of a rotary stage. CONSTITUTION:The photo current of a photodetector 62 which receices a light from a light emitting device 61 is amplified and then compared with a reference voltage by a comparator 82. The reference voltage thereof is previously set as the value of a photo current generated when a photo sensor 6 is so arranged that the optical axis H comes into contact with the periphery 1e. A position controlling mechanism 7 makes a sensor 6 retaining the photodetector 62 and the light emitting device 61 move rectilinearly toward the rotating center OT according to a signal from the comparator 82, and controls the sensor 6 so as to detect always the periphery 1e of a wafer 1. Position data of the sensor 6 are detected with a position detecting means 9 by utilizing a pulse counter used in a mechanism 7. The position data of the sensor 6 obtained by the means 9 and the rotation angle of the wafer 1 obtained by a rotation angle reading mechanism are stored in a storing means. The deviation amount between the center of the circumference of the wafer 1 and the center of rotation is obtained by calculation from the moving amount of a periphery detecting sensor, and exposure is performed while a correction angle is taken into account, thereby obtaining a highly precise exposure position.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to semiconductor wafers used for ICs, LSIs, and other electronic devices. This relates to an exposure method.

[Prior Art] In the manufacturing process of ICs, LSIs, etc., when forming fine patterns, a zero-order process is performed in which a resist is applied to the surface of a silicon wafer, etc., and then exposed and developed to form a resist pattern. Next, processes such as ion implantation, etching, and lift-off are performed using this resist pattern as a mask.

Usually, the resist is applied by a spin-to method. In the spin code method, resist is poured onto the center of the wafer surface and the resist is rotated.

Resist is applied to the entire surface of the wafer using centrifugal force.

However, the entire wafer surface is not used for processing; wafers coated with resist are transported and stored through various processing steps and in various ways, and the entire periphery or a portion of the wafer is used for holding. However, it is not possible to use the periphery very much, and in general, one circuit pattern is drawn distorted in the periphery, and the yield is poor.

By the way, if the resist is a positive resist, even after the exposure process for pattern formation, the resist in the peripheral area that is not used for pattern formation will remain, and the peripheral area of the wafer may be mechanically gripped and held, or the peripheral area of the wafer may be held. The parts may rub against the walls of storage containers such as wafer cassettes, creating a source of "dust". In the case of positive resists, unnecessary resist remaining on the periphery of the wafer becomes "dust" and reduces yields, which is a serious problem, especially now that integrated circuits are becoming more sophisticated and smaller. It has become.

Therefore, in order to remove the unnecessary resist around the wafer that remains after such development, it is necessary to perform a separate exposure to remove the unnecessary resist around the wafer in the development process, in addition to the exposure process for pattern formation. It is being done.

FIGS. 9A, 9B, and 9C are schematic illustrations of a conventional wafer peripheral exposure method for removing such unnecessary resist.

The wafer l is placed on the rotation stage 2 by a transport system (not shown).
is installed, the rotation stage 2 is rotated, the orientation flat If of the wafer l is detected by the sensor 72, and when the orientation flat if reaches approximately a predetermined position, one rotation is stopped, and then the orientation flat cover plate 74a and the pin Centering and positioning of the orientation flat If are performed by 74b, 74c, and 74d.

After the above positioning, while rotating the wafer I, light is irradiated from the output end 75 of the light guide fiber to expose the circumferential portion. In the exposure by this rotational movement (arrow 76a), the portion along the orientation flat 1f is not completely exposed because it is exposed as shown in FIG. 9(c), and the orientation flat If is stopped at a predetermined position.
Output end 75 parallel to orientation flat If
moving arrow 76b), it is necessary to expose.

[Problems to be Solved by the Invention] The conventional wafer peripheral exposure method described above exposes a constant width circumferentially from the edge of the wafer. However, when considering wafer utilization efficiency, it is desirable to use as much of the periphery as possible without causing a decrease in yield, or to hold only a few points where the holding claws come into contact and use the entire wafer area. There are also other requests.

Therefore, a technique is required to selectively expose only the portions of the wafer periphery that are in contact with the holding claws.

Here, it is technically quite difficult to select a predetermined location on the wafer periphery that is designated as a location to be contacted by the wafer holding claws.

In other words, when exposing a predetermined area around the wafer as described above while rotating the wafer, when the wafer rotates at a certain angle, the output end of the light guide fiber is brought to the irradiation position, or the shutter is opened or closed. Possible methods include controlling. The "certain angle" in this method is determined by a predetermined angle based on the design of the wafer, with some singular point as a reference. In this case, it is assumed that the center of rotation of the wafer and the center of the circumference coincide with each other, so it is necessary to perform an operation to make the center of rotation and the center of the circumference coincide with each other.

Therefore, selective exposure of a predetermined portion on the periphery of the wafer requires a wafer centering operation, which involves two rather complicated operations, resulting in a problem that the processing time becomes longer. Further, mechanical centering operation has a limit in terms of accuracy and cannot improve the accuracy of the exposure position.

The present invention was made to solve the above-mentioned problems, and its purpose is to provide a method for selectively exposing a predetermined location on the periphery of a wafer, which does not require a wafer centering operation or an a-structure, and has high exposure position accuracy. do.

[Means for Solving the Problems] In order to achieve the above object, the wafer peripheral exposure method of the present invention detects the rotation angle of the rotation stage while rotating the wafer with the rotation stage, and the rotation angle is determined by the exposure angle. 02
A wafer peripheral exposure method that exposes a predetermined area around the wafer to light by controlling the opening and closing of a shutter placed in an exposure light source etc. when the wafer is exposed to light, and detects the peripheral edge of the rotating wafer using a peripheral detection sensor At the same time, the peripheral edge detection sensor is integrally moved linearly toward the rotation axis for position control so that the peripheral edge detection sensor always detects the peripheral edge, and the position of the peripheral edge detection sensor where this position control is performed is controlled. According to the information,
A singular point on the wafer's periphery is detected, the amount of deviation between the center of rotation and the center of the wafer's circumference is calculated based on this singular point, and a correction angle α is determined based on the calculated amount of deviation, and a predetermined specified angle φ is calculated. Accordingly, the exposure angle θa is determined and the exposure is performed.

[Operation] By performing the above method, even if the center of the wafer and the center of rotation are misaligned, it is possible to accurately expose a predetermined location on the periphery of the wafer.

[Example] Next, the present invention will be explained in detail.

Each step of the wafer peripheral exposure method according to the embodiment of the present invention will be schematically explained below.

Step 2: While rotating the wafer once (360 degrees), the position of the sensor for detecting the periphery is controlled to follow the periphery of the wafer to detect the periphery.

Step (2): A singular point on the wafer's periphery is calculated from the position information of the periphery detection sensor whose position is being controlled.

Step m: Calculate the amount of deviation between the center of rotation and the center of the circumference based on the singular point, calculate the correction angle α from the calculated amount of deviation between the center of rotation and the center of the circumference, and calculate the correction angle α. The exposure angle θE is determined based on α and the specified angle φ input in advance.

Step (2): The wafer is rotated again, the shutter is controlled according to the determined exposure angle θE, and a predetermined portion on the periphery of the wafer is selectively exposed.

FIG. 1 is a schematic explanatory diagram of an apparatus for carrying out a wafer peripheral exposure method according to an embodiment of the present invention. In Figure 1, l is the wafer, tp is the wafer periphery, le is the wafer periphery, 2 is the rotation stage, 3 is the main controller, 4 is the stage drive mechanism, 5 is the rotation angle reading mechanism, and 6 is the sensor for detecting the periphery. 7 is a position control mechanism, 8 is a position control mechanism drive circuit, 9 is a position detection means for the peripheral edge detection sensor, IO is a sub-controller, 11 is a storage means, 12 is a calculation means, 13 is a A shutter drive mechanism, 14 a light guide fiber, 15 an emission section, and E an exposure light source section.

First, step (2) will be explained.

FIG. 2 is an explanatory diagram of position control of the photosensor 6 in the apparatus of FIG. 1. In FIG. 1, the photosensor 6
is controlled so as to always detect the peripheral edge 1e of the rotating wafer. That is, as shown in FIG. 2, the photocurrent of the photoreceiver 62 receiving light from one light emitter 61 is amplified by an amplifier 81 and compared by a comparator 82. The reference voltage of the comparator 82 is
It is preset as the value of the photocurrent generated when the photosensor 6 is arranged so that the optical axis H shown in FIG. 2 is in contact with the peripheral edge 1e. The output signal of the comparator 82 is sent to the position control mechanism 7, and the position control mechanism 7 uses the signal from the comparator 82 to move the photosensor 6, which holds the light emitter 61 and the light receiver 62 together, to the center of rotation OT. It is controlled so that the peripheral edge le of the wafer is always detected. Specifically, a servo motor is used as this position control mechanism 7.

Information on the position of the photosensor 6 when the position control mechanism 7 is performing position control is detected by the position detection means 9. As this position detecting means 9, for example, a pulse counter that counts the pulses of the servo motor used as the above-mentioned affJ control mechanism 7 is used. For example, the moving distance of the photosensor 6 for one pulse of the servo motor is known in advance. Therefore, depending on how many pulses the pulse counter counts at a certain rotation angle, the photo sensor 6
can detect the position of

Information on the position of the photosensor 6 detected by the position detection means 9 and the rotation angle of the wafer I read by the rotation angle reading mechanism 5 are sequentially sent to the storage means 11 and stored therein. In this way, the wafer 1 is rotated once (360 degrees), and data on the position of the photosensor 6 at each rotation angle is stored in the storage means 11. Storage means 1
1, an IC memory is used.

Next, step (2) will be explained.

In Figure 3, l is the wafer, oc is the center of the wafer's circumference, 1
f indicates an orientation flat, and o2 indicates an origin of the orientation flat as an example of a singular point.

The singular point is a reference point necessary for specifying a designated angle, determining an exposure angle, etc. Conventionally, the wafer l has been provided with an orientation flat if indicating the directionality of the crystal structure, and in this embodiment, this orientation flat if is detected and used as a reference point. However, since the orientation flat if has a length AB, the singular points are the intersection point 0 of the rotation center 0, the perpendicular line with a bow 1 to the orientation flat If, and the orientation flat If.
, and set point 02 as the origin of the orientation flat, that is, the singular point. In addition, wafers that have small notches on their periphery and are used for alignment, etc. are also being used recently, and in this case, this notch can be used as a singular point. Good.

FIG. 4 is an explanatory diagram of the relationship between the position of the photosensor and the rotation angle stored in the position detection means, of which (a) shows the actual measured values and (b) shows the differential values. It is.

The information on the position of the photosensor sent from the position detection means is the number of pulses of a servo motor used as a one-position control mechanism. This number of pulses n is the actual value of the information on the position of the photosensor, and this is taken as the vertical axis in FIG. 4(a). In addition, d n / d obtained by differentiating the number of pulses n with the rotation angle θ
θ corresponds to the displacement amount of the photosensor, and this displacement amount d n
/ dθ is the vertical axis in Figure 4 (b). Further, the horizontal axis in FIG. 4 is the rotation angle θ. Note that the rotation angle θ is determined by storing data of the rotational angular velocity (ω) of the rotation stage 2 in advance in the storage means 1 without using the data from the rotation angle reading mechanism 5 shown in FIG.
1, and the calculating means 12 may calculate 0=ωt and dθ=ωdt.

When the wafer starts to rotate and the photosensor moves to follow the change in the position of the periphery, the value of d n /dθ changes as shown by the dotted line in FIG. 4 (b).

Here, the region F where d n /dθ largely changes to the + side and the − side is considered to be the angular range in which the photosensor detects the orientation flat portion. Further, within the region F, dn/dθ=0. Since the displacement amount of the photosensor is O when the orientation flat is detected, this shows the state in which the photosensor 6 is closest to the rotation center 07. This state is as follows.
As shown in FIG. 3, the optical axis H of the photosensor 6 is at the origin O.
2, it is in contact with the periphery of the wafer, and by determining the 0°, it is possible to know the position of the origin OF. Therefore, in the operator stage 12 of FIG.
Rotation angle θ such that n/d O=O. Perform the calculation to find.

Next, step (2) will be explained.

FIGS. 5 and 6 are explanatory diagrams of calculation for determining the amount of deviation between the center of rotation and the center of the circumference from information on the position of the photosensor.

As shown in Fig. 5, based on the line segment drawn from the center of one rotation OT to the origin 02 of the orientation flat, θ,...
θE. θ3. θ4. θ5. The points on the periphery of the wafer when rotated by an angle of θ6 are A, A, and A, respectively, as shown in FIG.
Let C, B, A', C', B'.

Specifically, OI...45@02...90°θ3...135'θ4...zzs" 05...270@ 06...Fistfight...315'.θ4 = Or "+80", θS; θE÷
180" θ6 = 03 ÷ 180" and θ, = 00 + 90°
,03;0,+90'', θ1.θ3.θ
1. The angle of θ6 is not limited to the above angle. However, point A
, B' must not lie on the orientation flat.

In FIGS. 5 and 6, for example, consider a line segment AA' that passes through the center of rotation 0 and is perpendicular to the line segment BB' that passes through the center OC of the circumference. Let n(θl) be the number of pulses as information on the position of the photosensor when the foot sensor detects point A, and n(θ4) be the information on the position of the photosensor when it detects point A'. .

n (θ4) n (0+)= AOr −A'
Since the intersection point P is the midpoint of the line segment AAI', AP=A' If P=view, the amount of deviation OTP is OTP=AOT-intersection0AP=intersection-A'Or Therefore, OrP=54" AOT −A'Or=outskirts・
(n(θυ−n(('J)).

Therefore, the amount of movement n(Ot
), n (θ4), the distance of OtP can be determined. Also, n(θ4)−n(Ot)
By checking the sign of , it is possible to know the direction of the deviation. The values of a n (θ, ) and n (θ4) are stored in the storage means 11 of FIG. 1 as shown in FIG. 4 (a). Since it is in the data, the above θ1. The arithmetic means 12 may perform the above calculation by specifying θ4 and sampling.

Similarly, it is shown in FIG. The distance and direction of TQ are n(
From the data of θ3) and n(θ6), the distance and direction of the OAR are determined from the data of n(θ,) and n(θ5).

FIG. 7 is an explanatory diagram of the correction angle α. lpD indicates a predetermined location on the wafer periphery, φ indicates a designated angle, and α indicates a correction angle.

The angle that can be read by the rotation angle reading mechanism 5 shown in FIG. 1 is the rotation angle of the rotation stage 2, that is, the rotation angle with respect to the rotation center Oa. Therefore, for exposure in step (2) to be described later, it is necessary to specify the exposure angle θE based on a line segment connecting the rotation center OT and some singular point on the periphery.

Therefore, as shown in FIG. 7, the specified angle φ is specified in advance based on the line segment connecting the origin OF of the orientation flat as a singular point and the rotation center OA. This specified angle φ is specified according to the position of the wafer periphery where the wafer holder is held in a subsequent processing step, and is input in advance to the main controller as shown in FIG. Therefore, if the exposure angle θE is expressed by the specified angle φ and the correction angle α, then 02
=φ+α.

The correction angle α is obtained from the data in step ① by the calculation shown below.

FIG. 8 is a diagram for explaining the calculation for determining the correction angle α. O, P=a, OchoQ=b, 0aR=c in Figure 6
shall be.

In Figure 8, β=tan-'(c/V) y='iη1τiP, °, β=jan-'(c/a+b-c
) ...(1) Also, x cosa -a cos(180°-(β+φ))
=r+”+ x cosa + d cos(β+φ)
= r ””(2)d 5in(180°−(β
+φ))=x sinαdsin(β+φ)=xsin
α:, x = d 5in(β+φ)/sin a
...(3) Substituting (3) into (2), (dsin(β+φ)/sin αtocosa+d
cos(β+φ)=“(dsin(β+φ)/lan α)+dcos(β+
φ)=rLanα−5in(β+φ)(r/d
)−cos(β+φ))8α=tan−′(sin(β+φ)/((r/d)−
cos(β+φ)))...(4) Therefore, in the arithmetic means built in the main controller 3 in FIG.
After receiving the data, the calculation of equation (1) is performed, and then the calculation of equation (4) is performed to calculate the correction angle α.

Then, from the input φ and the calculated α, 02=φ+α
is calculated to obtain the exposure angle 02.

Next, step (2) will be explained.

In FIG. 1, the exposure light source section E includes a light source lamp El such as a short-arc type mercury lamp, an elliptical collector mirror E2 that focuses the light from the light source lamp El into the light guide fiber 14, and a plane mirror E3. It consists of shutter E4 etc. Light from the exposure light source section E is guided by a light guide fiber 14, and projected onto a predetermined location around the wafer by an output section 15 having a projection lens inside. Emitter 1
5 is attached to a photosensor 6 so as to expose a predetermined portion including a point on the peripheral edge le having an exposure angle θ6, which will be described later.

In FIG. 1, as the rotary stage 2 starts rotating again, the rotation angle is read by the five rotation angle reading mechanism 5, and a rotation angle monitor signal is sent to the main controller 3. When the main controller 3 receives a signal indicating that the rotation angle has reached the exposure angle θE, it sends a shutter drive signal to the shutter drive mechanism 13, and the shutter E4 is opened for a predetermined period of time to expose a predetermined area around the wafer. It will be done. It should be noted that the position of the emission unit 15 at the beginning of the rotation is not necessarily at the position that exposes the origin 02 of the orientation flat, which is the reference point, so one rotation (360 degrees) in step
Since the position of the origin 02 at the end of the process can be determined by calculating the singular point in step H, specifically, the rotation angle is θ by adding the above-mentioned θ0 to the exposure angle θE. When the time reaches 10, the shutter E4 is driven.

Further, the shutter opening time is determined in advance according to the length in the circumferential direction of a predetermined portion of the periphery of the wafer to be exposed, and is input to the main controller 3.

In addition, if circumferential exposure of a certain width from the peripheral edge 1e is required,
The shutter E4 may be opened during the rotation in step (2), and the exposure may follow the peripheral edge 1e of the wafer 1.

Further, in this embodiment, a transmission type photosensor 6 is used as a peripheral edge detection sensor, but the present invention is not limited to this, and various sensors such as a reflection type photosensor or a magnetic sensor can be used.

[Effects of the Invention] As explained above, according to the present invention, the amount of deviation between the center of the wafer's circumference and the center of rotation is calculated and determined from the amount of movement of the peripheral edge detection sensor, and the correction angle α is taken into account. Since exposure is performed, there is no need for a wafer centering mechanism or operation, and the wafer periphery exposure method provides high exposure position accuracy.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of an apparatus for carrying out a wafer peripheral exposure method according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of position control of the photosensor in the apparatus of FIG. 1. FIG. 3 is a diagram for explaining the singularity in the embodiment of the present invention. Figure 4 is an explanatory diagram of the relationship between the position information of the photosensor stored in the 1-position detection means and the rotation angle, of which (A) shows the actual measured value and (B) shows the differential value. It is something. FIGS. 5 and 6 are explanatory diagrams of calculations for determining the amount of deviation between the center of rotation and the center of the circumference from the data of the position information of the photosensor. FIG. 7 is an explanatory diagram of the correction angle α. FIG. 8 is a diagram for explaining the calculation for determining the correction angle α. FIGS. 9A, 9B, and 9C are schematic illustrations of a conventional wafer peripheral exposure method. In the figure. l Two-handed conductor wafer 2, rotating station Main controller Rotation angle reading mechanism Flex position control mechanism as a peripheral edge detection sensor Sub controller Rad sensor E: Exposure light source section E4: Shutter lpD: Predetermined location on the periphery of the sea urchin le : Periphery Oc: Center of circumference Or: Orientation as singular point Origin of flat OT = Center of rotation

Claims (1)

[Claims] While the wafer is being rotated by the rotary stage, the rotation angle of the rotary stage is detected, and when the rotation angle reaches the exposure angle θ_E, the opening and closing of a shutter disposed in the exposure light source section, etc. is controlled. , a wafer periphery exposure method for exposing a predetermined area on the wafer periphery, in which the periphery of the rotating wafer is detected by a periphery detection sensor, and the periphery detection sensor is arranged so that the periphery detection sensor always detects the periphery. The position of the wafer is controlled by linearly moving it toward the rotation axis, and the singular point on the periphery of the wafer is detected using the position information of the peripheral edge detection sensor that performs this position control, and the rotation is performed with this singular point as a reference. The method is characterized in that the amount of deviation between the center and the center of the circumference of the wafer is calculated, and the exposure angle θ_E is determined based on the correction angle α found based on the calculated amount of deviation and a predetermined specified angle φ, and the exposure is performed. Wafer peripheral exposure method.