JPS60102738A - Baking and exposure device for semiconductor - Google Patents

Abstract

PURPOSE:To improve the accuracy of positioning by measuring all of a plurality of alignment marks, calculating the quantity of positional displacement and correcting positional informations from the alignment marks as one part by the quantity of positional displacement when baking and exposing a semiconductor. CONSTITUTION:When a plurality of alignment marks are all measured, the quantity of positional displacement is calculated, and the quantity of pitch error is memorized. When the quantity of positional displacement within a tolerance is decided and the quantity extends outside the tolerance, a position is corrected. When one part of a plurality of alignment marks are measured, the quantity of pitch error is corrected on the basis of the quantity of pitch error in the case when a plurality of alignment marks are all measured, and a semiconductor is positioned. Positioning with high precision is enabled even in positioning using one part of alignment marks because the quantity of pitch error is made approximately constant in neighboring shots.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a semiconductor printing exposure apparatus for transferring integrated circuit nomiturns onto a photoresist layer of a wafer, particularly a stepper that performs stepwise exposure of a wafer. This relates to automatic alignment of the wafer and the mask (hereinafter both will be collectively referred to as the mask) and the wafer.

[Prior art]

Semiconductor exposure equipment has made remarkable progress in line with the development of semiconductor integration technology, and its mechanism has changed to include equipment that performs close-contact or extremely close-up printing, equipment that performs 1x printing using a lens or mirror system, or equipment that performs reduced projection images on a wafer. There is a wide variety of devices such as steppers that print directly.

One of the methods for aligning the mask and wafer in a stepper is the TTL Gui-Pie-Die alignment method in which the mask and wafer are aligned for each shot through a projection lens. This method has the advantage that highly accurate positioning can be achieved because alignment is performed for each shot.

Incidentally, in order to save time, it is usual to bake a plurality of chips at once per shot. However, a part of the chip is out of place at the periphery of the wafer, so when the mask-side alignment mark is located in that part, there is no corresponding wafer-side mark, so alignment is impossible and the chip is not aligned inside the wafer. Other chips that could be included were sacrificed. Regarding this, an exposure apparatus has been proposed in which the number of chips obtained is improved by providing means for selecting only a portion of a plurality of alignment marks per shot (Japanese Patent Application No. 58-151024).

Furthermore, there are cases where alignment marks are missing inside the wafer, making alignment impossible; however, exposure equipment has been proposed to solve this problem (
Patent application Sho 58-14089 (S).

However, there are pitch errors due to misalignment between the wafer and the mask, such as expansion and contraction of the wafer, etc., which cannot be obtained from measurement information of a portion of the plurality of alignment marks (one of the alignment marks or one half of each mark).

[Purpose of the invention]

The present invention has been proposed in view of the above, and an object of the present invention is to provide a semiconductor exposure apparatus that can improve alignment accuracy when aligning using some alignment marks.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1(A) shows the main structure of a stepper equipped with an alignment mark detection system.

In the figure, 1 is a mask provided with an integrated circuit pattern and alignment marks, and is held on a mask stage 24. 6 is a reduction projection lens, 4 is a wafer provided with a photosensitive layer, and provided with alignment marks. 5
is a wafer stage, which holds the wafer 4. The mask stage 24 and the wafer stage 5 are arranged in the plane (X direction, Y direction) and in the rotational direction (θ
direction).

For example, first, the wafer stage 5 is moved in the XY directions to perform a step-and-repeat motion, and the mask stage 24 is moved in the XYθ directions to initially set the mask 1 in the apparatus.

Next, the mask stage 24 is moved in the XY directions, and the wafer stage 5 is moved in the θ direction to align the mask 1 and the wafer 4.

However, alignment may be performed by moving the mask stage for both XYθ, or conversely, alignment may be performed by moving only the mask stage. Incidentally, the step movement of the wafer stage 5 is executed according to the shot arrangement stored in the storage section M of the control device.

Also, 20 and 20' are alignment marks of mask 1, 2
1 and 21' are alignment marks of Weno 1-4. In the figure, the alignment mark of wafer 4 is shown as 1 for convenience.
It is assumed that the number of sets is actually the same as the number of shots to be exposed.

Note that the alignment marks on the mask 1 and the alignment marks on the wafer are arranged so that when a system other than the same-magnification projection system is used, the dimensions of both alignment marks do not change even if the projection or back projection is performed. The dimensions are set to be different, and in this case, the reduction ratio is set so that the dimension of the alignment mark on the wafer is divided by the dimension of the alignment mark on the mask.

28 is a rotating polygon mirror that rotates around a rotation axis 29. The light beam emitted from the laser light source 22 is converged by the lens 26 to a point 61 on the surface of the rotating polygon mirror 28 .

Lenses 32, 33, and 34 are lenses for relaying light beams, and 65 is a triangular prism, and since the apex of the triangular prism 65 coincides with the optical axis, the laser beam can be scanned once. It can be divided into Reference numeral 69 denotes a prism block for converting laser light scanning in the direction in the drawing to scanning in the direction perpendicular to the drawing, and is configured in a shape as shown in FIG. 1(B), for example.

42 is a half mirror forming the photoelectric detection system (43, 4j, 45, 46), 46 is a mirror, 44 is a lens, 45
is a spatial filter, 46 is a condenser lens, 4
7 is a photodetector. 48°49.50.51 is a total reflection mirror, 52 is a prism, and 56 is an f-θ objective lens.

Further, 57 is a condenser lens, and 58 is a photodetector for detecting a synchronization signal. A part of the laser light incident on the semi-transparent mirror 42 is condensed by the condenser lens 57 and is incident on the photodetector 58. The photodetector 58 therefore serves to detect the start and end points of the laser beam scan.

As you can see from the figure, the signal detection system consists of completely symmetrical left and right systems.If the operator side is the front side of the paper, the system shown with a dash is the one on the right, and the system without a dash is on the left. We call them systems, and the same parts are given the same number with a dash.

The relay lenses 32, 33, 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 56. Therefore, the note-shaped or spot-shaped laser beam is scanned over the mask and wafer by the rotation of the rotating polygon mirror 28.

In addition, in the objective lens system, the objective lens 56, the aperture 5
5. The mirror 51 and the prism 52 are movable in the XY directions by a moving means (not shown), and the measurement positions of the mask 1 and Weno-4 can be changed arbitrarily. For example, when moving in the X direction, when the mirror 51 moves in the direction indicated by arrow A in the figure, the objective lens 56 and the aperture 55 simultaneously move in the entrance direction, and the prism 52 also moves in the entrance direction to keep the optical path length constant. It moves by 1/2 of the movement amount of 51.

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

Since the objective lens system can be moved in this way,
Mark detection can be handled when the position of the alignment mark differs depending on the mask or when a mask setting mark is provided separately from the alignment mark.

100 However Stage 5 and Mask Stage 24
The details of its operation will be described later with reference to FIG. 6. C is a control circuit that controls operation;
Further, M is a storage circuit in which a predetermined shot arrangement and step order are stored, and the amount of correction for positional deviation will also be stored later.

A signal selection circuit S selects both or one of the detection signals from the photodetectors 47 and 47' according to the shot arrangement and step order determined by the memory circuit M. 0 is an arithmetic circuit that calculates X, which is necessary for alignment, from two columns of detection signals.
The amount of movement in the Y and 0 directions and the pitch error are calculated. Based on these, the mask and stage 24 are moved to the alignment position via the first drive circuit, and the pitch error is stored in the memory circuit M. When one of the detection signals is selected, the pitch error stored in the memory circuit M is read out and used to correct the calculation result of the alignment data obtained with one of the detection signals. D2 is a second drive circuit, which drives the wafer stage 5 in steps according to the shot arrangement and step order determined by the memory circuit M. Note that if the detection signal from the photodetector 47, 47' is not complete because it corresponds to only one side or a partial mark, the signal selection circuit S determines this and applies it to the appropriate arithmetic expression described later.

8- FIG. 2(A) is a diagram showing alignment marks on the mask surface. Mark 20 (FIG. 1) on mask 1 consists of orthogonal bars 75 and 76, and similarly mark 20' consists of bars 75' and 76'.

When the marks 21 and 21' on the shredded wafer are back-projected onto the mask 1 through the projection lens, the mark 21 consists of parallel bars 71, 72, 73, 74 that are perpendicular to each other; It consists of 72', 73', and 74'. Details of this alignment mark can be found in JP-A-53-90
872.

Here, the alignment mark is divided into two by the axis of symmetry and is called as follows.

Bar 71.72.75 marks the first part bar 73.7
4.76 second part mark par 72', 73'
, 76' to the sixth partial mark - 71', 72
', 75' is the fourth part mark laser beam is shown in Figure 2 (
A) As shown at 60 and 60', the left detection system scans the hair alignment mark in the Y direction from the front of the device (bottom of the page), and the right detection system scans the hair alignment mark in the minus Y direction from the back of the device (top of the page). FIG. 2(B) is an enlarged view of the left detection system mark in FIG. 2(A).

When the laser beam 60 scans the mark in FIG. 2(B),
The photodetectors 47 and 47' are equipped with the following components as shown in FIG. 2(C).
Signals 871 to 876 are obtained. S71, S72
°S73 is a signal corresponding to the marks 71, 72, 73, respectively.

Therefore, the detection signals 871, 875 . S72. S73,8
76.874 intervals w1. w2. w3. By measuring w4, the amount of misalignment between the mask and the wafer can be detected.

X of the first partial mark and second partial mark of the left signal system
The amount of deviation AXL, ΔYL in the direction and Y direction is ■T-= (
Wl-W2-W3+W4)/4 ・Formula (1) ΔYL −
(-Wi +W2 +W 3-W4 )/4 ・Formula (2
).

Also, the amount of deviation of the sixth partial mark and fourth partial mark of the right signal system, △XR, △YR, is 78XR-(-Wl'+
W 2'-1-W 3'-W 4') / 4 ・
Formula (3) △YR-(2W1'+W2'-W3'10W4
')/4 ・Equation (4) is obtained.

Therefore, the amount of deviation in the rotational direction △θ is △θi△YR-△YL)/□t'R-XL) ・Equation (5) However, XL and XR are the centers of gravity of the left mark and right mark from the center of the mask. This is the distance at position 1, and therefore (XR, -XL) is the distance between the left and right marks.

In addition, the amount of deviation in the X direction of the right detection system, AXR and the X of the left detection system
Amount of deviation in direction ■ Difference from L △XR - △X! , should originally be zero since the left and right mark spacing on the mask and the left and right mark spacing on the wafer should be equal. However, in reality, it may not become zero, and the difference in the amount of deviation in this direction (△XR - △XL)/2 is called a pitch error.

The main reasons why pitch errors occur are (a) wafer or mask expansion or contraction (1)) wafer warpage (C) mask accuracy (d) printing magnification error and distortion (
(e) lens effect of the resist layer, etc.

This amount of pitch error is included in the amount of deviation of the right detection system and the left detection system, respectively, and it is determined whether or not the amount of deviation is within the allowable range. This does not pose a problem in the execution of the .

On the other hand, auto-alignment i with partial marks to which the present invention is applied is performed using the following partial mark combinations in both cases of auto-alignment using one mark of a peripheral shot and auto-alignment due to missing alignment marks. . That is, ■ the first part mark and the second part mark.

■ 6th part mark and 4th part mark.

■ 1st part mark and 4th part mark.

■ There are four combinations of the second partial mark and the sixth partial mark.

The positional deviation amount △X, △Y for each combination is calculated as follows: In the case of ■...Equations (1) and (2) above.

In the case of ■... Equation (3) and Equation (4).

In the case of ■... △X-(Wl-W2+W3'-W4')/4...Formula (6) △Y-(-W1+W2-W3'+W4')/4
...Equation (7), and in the case of ■∆X-(-W1'+W2'-W6+W4)/4...
Formula (8) △y-(-w1'+w2'+w3-w4)/4
...Equation (9).

In either case, the difference (△XR - △XL)/2 between the amount of deviation in the X direction of the right detection system and the amount of deviation in the X direction of the left detection system cannot be detected, so if a pitch error occurs, If measurement is performed using a partial mark on a wafer that is currently in use, alignment errors will occur due to pitch errors.

The present invention focuses on this point, and makes it possible to perform positioning in consideration of the amount of pitch error even in the case of measurement using partial marks. In other words, since the pitch error amount is almost constant in shots near the shot of interest, alignment can be performed by correcting the pitch error amount of the neighboring shots to the amount of deviation △X in the X direction. good.

FIG. 3 is a flowchart for explaining the operation of the auto-alignment method of the semiconductor printing exposure apparatus according to the embodiment of the present invention. Auto alignment is step 601
When the star is 1, it is first determined in step 302 whether or not the measurement of the shot of interest is by both left and right marks.

In the case of measuring both marks, in step 606, the distance between the 12 auto-alignment marks is measured. When the interval measurement is completed, in step 304, the amount of deviation between the marks of the left and right rain detection systems is determined by (1), (21, (3), (4)).
Calculate by Also at this time, pitch error EP-(△X
R・−△XL)/2 is also calculated at the same time, and step 305
The pitch error EP is stored in the memory.

On the other hand, if both marks are not measured, the process branches from step 602 to step 606, and in step 306, one mark is measured. After the end of the measurement, in step 607, the amount of deviation is calculated using the formula (+1(2+) if the one mark is for the left detection system, and by formulas (3) and (4) when it is for the right detection system.

Next, in both cases of double mark measurement and single mark measurement,
At step 608, the pitch error value stored in the memory is read. Therefore, when measuring both marks, the pitch error value of the current shot is read, and when measuring one mark, the pitch error value when measuring both marks immediately before the current shot is read out. The amount of deviation in the X direction is corrected by the value of this pitch error, and the amount of deviation △XI- of the left detection system is △XL+EP.

For the deviation amount △XR of the right detection system, △X R, -+-E
It becomes P. In the case of a one-sided mark, a similar correction is made to the amount of deviation of either the left or right mark.

Next, in step 609, it is determined whether the corrected deviation amount is within an allowable range.

Assuming that the allowable range of alignment is sufficient for the amount of deviation to be within a square of length T, it can be expressed by the following equation.

△XL×EP≦T ・・Formula Oo) △XR−1−EP≦T ・・Formula (11) △YL ≦T
110 formula (12) △YR・≦T ... formula (13) The above formula can also be applied to the measurement of one-sided marks, and in the case of left marks, formula Cl0) and formula 02), In the case of a right mark, determination is made using equations (11) and (13).

If the amount of deviation is outside the allowable range, that is, equation (10), (II
), (12).

If (13) is not satisfied, the process branches to step 610, and in step 610 it is determined whether or not both marks are measured. When both marks are present, the amount of drive of the stage is calculated in step 611. The drive amounts DX and DY of the stage in the X and Y directions are expressed by the following equations.

DX=-(△XL+△X”)/2 ,, Formula (I4)D
Y=-(ΔYTJ+ΔYR·)/2 (+5) On the other hand, when a single mark is made, the process proceeds to step 612, and the stage drive amount is divided by the pitch error correction of the present invention. In other words, in the case of only the right mark, DX=-(△XR-
BP) ...Formula (16) DY=-△YR...Formula 07) In the case of only the left mark, DX=-(△xr, 10EP) ...Formula α8) DY-1△YL...・Equation (There will be one.

16- In this way, pitch error correction is performed even when alignment is performed by measuring one mark, so accurate alignment is achieved.

When the calculation of the drive amount is completed, the process proceeds to step 616, where the stage is driven, and the process returns to step 602, where measurement is performed. The above-mentioned loop is repeated until the amount of deviation falls within the allowable range, and if it falls within the allowable range, the process branches from step 609 to step 614, and the auto-alignment ends.

In FIG. 6, the present invention has been explained using an example of one-sided mark measurement using shot alignment, but pitch error correction can be performed in exactly the same way in the case of partial mark alignment when some marks cannot be detected as described above. Alignment can be performed by Further, as the pitch error correction value, in the embodiment, the pitch error value of both immediately preceding mark shots is used, but for example, the average value of the pitch errors of several previous shots may be used.

〔Effect of the invention〕

As explained above, according to the present invention, even when alignment is partially performed using alignment marks, alignment is performed by correcting pitch errors and rotational deviations, so that highly accurate alignment can be achieved. .

[Brief explanation of drawings]

FIG. 1(A) is a schematic configuration diagram of a semiconductor printing exposure apparatus according to an embodiment of the present invention, and FIG. 1(B) is a schematic diagram of a prism block used in a semiconductor printing exposure apparatus according to an embodiment of the present invention. Figure 2 (A) is a plan view of the mask alignment mark and the alignment mark on the mask surface, and Figure 2 (B) is an enlarged view of the alignment mark of the left detection system in Figure 2 (N). , FIG. 2(C) is an output signal diagram when the alignment mark shown in FIG. 2(B) is optically scanned, and FIG. 3 is a flowchart for explaining the operation of the semiconductor printing exposure apparatus according to the embodiment of the present invention. The figure is: 1...Mask 6...Reducing projection lens 4...Wafer 20.2α・Mask alignment mark 21.21'・
Wafer alignment mark 39.39'...Prism blocks 71-74...Left-hand wafer alignment mark 75
．． 76... Left-handed mask alignment marks 71' to 7
4'・Left-hand wafer alignment marks 75', 76
'... Left-hand mask alignment mark 100 Control device for wafer stage and mask stage. Figure 2 (A) Figure 2 (B) Figure 2 (C)

Claims (1)

[Claims] Either all or part of a plurality of alignment marks is selected for each shot, and the relative positional relationship between the mask and the wafer is detected using the selected alignment mark to align the mask and the wafer. A step-type semiconductor printing and exposure apparatus that performs a step-type semiconductor printing and exposure apparatus that performs a step-type semiconductor printing and exposure apparatus that performs a step-type semiconductor printing exposure apparatus that performs a step-type semiconductor printing exposure apparatus that performs a step-type semiconductor printing and exposure apparatus that performs a step-type semiconductor printing and exposure apparatus that includes: a calculation means for calculating the amount of positional deviation that is calculated only based on information obtained by measuring all of the plurality of alignment marks; 1. A semiconductor printing and exposure apparatus, comprising: means for correcting relative position information obtained by a portion of the image, based on the amount of positional deviation.