JPS5914637A - Exposing apparatus - Google Patents

Abstract

PURPOSE:To obtain an excellent pattern by the step and repeat exposure by using a theta-angle adjusting mark among the reference mark and theta-angle adjusting mark given to the X and Y axes and the mask in such a shape directed to the connecting direction of reference mark. CONSTITUTION:Connection of marks 22a, 22b of mask 21 forms an angle of 45 degrees against the X axis and an angle adjusting mark 22b is crossed by the line elements 231 and 232. At the time of positioning, the line element 231' of the angle adjusting mark 22b' exists on the extension line of the reference mark 22a and mark 22b' because expansion occurs equally in each direction if the mask expands (21'). Therefore, if positioning is carried out by stacking the mark on the exposing base on the line element 231, any rotation does not occur before and after the expansion and thereby the reference and angle adjusting marks can be stacked on the same coordinate. As a result, there is no deviation of alignment at the area near the reference mark but the deviation increases as the area is more apart from the reference mark. But in the step and repeat exposure method, the coordinate of the center of transferred pattern can be controlled accurately to below submicron order or less. Therefore, according to this structure, deviation of alignment due to expansion and compression of mask can be reduced to a large extent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a wafer exposure apparatus, and more particularly to a reduction projection type step-and-repeat wafer exposure apparatus.

[Technical background of the invention]

As LSI integration progresses, microlithography is becoming increasingly important. The accuracy of microline graphs (accuracy greatly depends on the performance of the exposure equipment).The performance of recent exposure equipment has been remarkable, but projection type, especially reduced projection type, is especially suitable for fine line width lithography. A step-and-repeat exposure apparatus has been developed, and is seen as a promising machine for lithography with a line width of about 1 μm.

By the way, as a step-and-repeat type exposure apparatus, one having the structure shown in FIG. 1 is known. That is,
1 in the figure is a wafer chuck 2 that can be rotated by a motor etc.
This is a stage that can move freely in the X and Y directions. A region of the stage 1 other than the wafer chuck 2 is marked with a cross-shaped mark 3, for example, to be compared with a mark on a mask described later. Further, above the stage 1, a lens barrel 4 containing a built-in optical system for reducing the mask pattern is provided, and a light source 5 is provided on the lens barrel 4 at a predetermined distance. Furthermore, numeral 6 in the figure is an alignment mechanism disposed above the stage 1 in a fixed positional relationship with the lens barrel 4. This alignment mechanism 6 is attached to the main body 2 arranged in a fixed positional relationship with the lens barrel 4, and near the bottom of this main body 7,
Mark 8a to match with the alignment mark of Unino 1
, 8b, and microscopes 9m and 9b, which are provided on the main body 7 and are used to observe the alignment between the alignment marks on the wafer and the marks 8a and 8b.

Next, a method of exposing a wafer using the exposure apparatus described above will be explained.

First, a mask having a desired pattern (for example, for field formation) is placed on the lens barrel 4, but since the mask and the wafer are jointed indirectly, in order to sufficiently improve the matching accuracy, for example, the coordinates of the stage 1 are It is necessary to set the X-axis of the system so that it is parallel to the X-axis of the coordinates of the mask, and so that the Y-axis of the coordinate system of the stage 1 and the Y-axis of the coordinates of the mask are parallel. For this reason, in the conventional exposure apparatus, as shown in FIGS. 1 and 2, a point K on the X-axis that is off the mask pattern with the center point as a reference, for example, a cross-shaped reference mark 10a, is on the Y-axis that is off the mask pattern. A mask 11 having a cross-shaped θ angle adjustment mark 10b is also used at each location. Next, the mask 11 is placed on the lens barrel 4, the stage 1 is moved to move the mark 3 on the stage 1 to the original setting position 11 (always fixed coordinates), and then the mask 11 is moved to The reference mark 10a on the axis is aligned with the mark 3 on the stage 1. 8. Continuing, move stage 1 again and move its mark, ri 3
After moving the mask to the original setting position (also always fixed coordinates), move the mask 11 around the reference mark lOa on the X-axis.
is rotated to match the θ angle adjustment mark 10b on the other Y axis with the mark 3 on the stage 1. This operation aligns the mask.

Next, the wafer 12 fixed in advance on the Unino 1 chuck 2
By step-and-repeat exposure in the X and Y directions for each stage 1, and by irradiating the mask 11 with light from the light source 5 at each step and reducing the nolin for forming the feel P with the lens barrel 4, as shown in FIG. As shown in the figure, four field transfer turns 13 are formed on the unicorn 12. however,
In this transfer process, a predetermined area is transferred with 9 turns and 13
. . . and attach two cross-shaped alignment marks to each of them.

[Problems with background technology]

However, in exposure equipment that uses the above-mentioned mask, it is rare that the mask alignment is carried out perfectly, and even if stage 1 is perfectly positioned, the mask material strength is usually low. This causes misalignment. The amount of deviation when the mask 11 is expanded will be specifically shown below.

First, let's take the case of a 1/10 reduction exposure device as an example, and the size 10
Consider a case where a mask 11 having a size of 0 mm x'100- is extended by 10 μm. Here, the stretched mask 1 as shown in FIG.
1' reference mark (coordinates -50,005m, 0)
10 ', θ angle adjustment mark (coordinates 0, 50.00
5 m) as 10b'. In order to align the mask 11' with the stage 1, the reference mark zc>a' (IOa) is matched with the mark 3 of the stage 1 according to the procedure described above, and the mask 11' is aligned with the reference mark 10a' as the center.
is rotated by a desired angle and the θ angle adjustment mark 10b' is compared with the mark 3 which has been moved again to the set position on the stage 1, thereby aligning the mask 11'. At this time, since the mask is elongated, as shown in Figure 4, θ is
The mask is rotated by a certain rotation angle (α) at the position of the θ angle adjustment mark 10b' of the mask 11' which is elongated compared to the position of the angle adjustment mark 4ob. This α
When calculated, α=0.0057287°. If the amount of deviation in the Y-axis direction at a location 100 fins away in the X-axis direction is estimated from the α value, the amount of deviation will be approximately 10.000 μm. However, since it is a reduction exposure device, 1 on the wafer 12
Since the size is reduced to /10, the amount of deviation of one transfer pattern on the wafer 12 in the Y-axis direction is 1.0 μm. If the amount of stretch of the mask is 8 μm, the amount of deviation in the Y-axis direction at a location 100 m away on the wafer is 8710 μm.

By the way, based on the above-mentioned amount of deviation, consider the amount of alignment deviation when a large number of masks are used. First, the above-mentioned deviation amount is determined by the rotation of one transfer pattern of the mask during the first PEP process, and the pattern IJ'... transferred to the resist trap on the wafer 12 as shown in FIG. It will be a rotation. Next, alignment for the second layer (for example, formation of dirt electrodes) is performed on the base pattern. Normally, the distance between the two microscopes 9m and 9b in the alignment mechanism 6 shown in FIG.
Since the number of transfer patterns 13, etc. is determined as shown in FIG.
--- Two alignment marks 14@, 14b are respectively placed inside the predetermined two transcription marks J? The distance between the alignment mark 148 of one /l turn 131 of the turns 131 and 13n and the alignment mark 14b of the other 41 turn 13n is formed at the same time so as to match that between the microscopes 5'a*9b. There is. Normally, in the second PEP process, using these alignment marks 14m and 14b, the microscopes 9tr and 9b are
Since the second transfer is performed after positioning the wafer 12 in the X and Y directions in accordance with the VC, there is a difference between the second layer transfer pattern and the second layer transfer pattern, which did not occur during the first transfer pattern formation. Misalignment occurs. Rimashi,
As shown in FIG. 7, alignment mark 14b' visible on the right microscope 9b and alignment mark 14a visible on the left microscope 9a.
' is the transfer pattern I J,1.

Even though rotation has occurred within 13n, there is no need to rotate the wafer 12 in order to adjust the line connecting alignment marks 14 &'a14b' to be horizontal, and in the end rotation is required. become.

For example, if we consider that the mask extends by 10 μm and the mark positions are 10 degrees apart in an area of 10 degrees, this amount is calculated as follows.
As mentioned above, since the die rotation is 1.0 μm, when one mark (z4b) is used as a reference, the position of the other mark 14 m#'i is shifted by 1.0 μm in the Y-axis direction. As a result, when the distance between the microscopes 9a and 9b is 63.5cm and the diameter of the wafer 112 is 100fi, the total wafer rotation amount is
The difference between the two ends is 1.0 μm (X-L00 = 1.57 μm), which is a very large misalignment of 63.5 μm. Looking at the tabs, transferred holes and turns, the alignment of the chips at the transfer pattern 131' is good, but the alignment of the chips at the transfer pattern 13n', which is n spaces apart, is due to misalignment in the Y-axis direction. I will be visiting.

[・Purpose of the invention]

The present invention eliminates die p-chision in the first step-and-repeat exposure process and rotation of the transferred pattern with respect to the base pattern formed in the first time in the second and subsequent exposure processes, and improves IJ. ? The present invention aims to provide an exposure apparatus capable of forming turns.

[Summary of the invention]

The present invention provides reference marks attached on the X-axis and Y-axis and θ
Among the angle adjustment marks, use a mask in which the θ angle adjustment mark is oriented in the connection direction of the mark and the reference mark.Therefore, as the mask expands, the mask is displaced by a certain rotation angle. The main idea is to make it possible to always align to the stage in the desired state without having to adjust to the stage marks.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIG. It should be noted that each member of the exposure apparatus other than the mask has the same structure as that in FIG. 1, so a description thereof will be omitted.

21 in the figure is a mask built into the exposure apparatus. This mask 21 has a cross-shaped reference mark 22a and a cross-shaped θ angle adjustment mark 22b on the X-axis and the Y-axis, respectively. The connections between these marks 22a and 22b are at an angle of 45° with respect to the X-axis of the mask, and the θ angle adjustment mark 22b is connected to a line element 231 oriented in the connection direction and a line element perpendicular to this. It has a cross shape with an angle of 23 degrees.

Therefore, in order to match the mask 21 shown in FIG. 8 to the lens barrel 4 as shown in FIG. Then, the reference mark 22 on the X axis is aligned with the mark 3 on the stage 1. Next, after moving the stage 1 again and moving the mark to the original setting position, rotate the mask 21 with the reference mark 22a on the The mask 2) is aligned by comparing it with the mark 22bt□ of the stage 1. Consider a case where the mask 21 expands during such positioning and enters the state shown by the dotted line.

When the mask 21 expands, the expansion is in the same direction, and one line element 231 of the cross-shaped θ angle adjustment mark 22b of the mask 21 is aligned with the mark 22b and the reference mark 22m.
Because it is oriented in the wire connection direction, one line element 23 of the θ angle adjustment mark 22b' of the mask 21' after expansion
1' is the reference mark 22%' (22th) and the mark 22
It coincides with the extension line of the connection b'. However, the reference mark 2 of the mask 21' expanded in the same manner as described above
When aligning the reference mark 2a' (22m) with the mark 3 that has been moved again to the set position on the stage 1, the reference mark 22a' (22m) is
22&), rotate the mask 21' around stage 1.
The intersection of the cross-shaped mark 3 and the cross-shaped θ angle adjustment mark 22
If the intersection point of the mark 3 is positioned so that it overlaps one line element 231' of the cross-shaped θ angle adjustment mark 22b', instead of matching the intersection point of the mark 3 with the intersection point of The inflated mask 21' can be positioned with respect to the uninflated mask 2 without rotation.

Therefore, the reference marks and theta angle adjustment marks that align the X and Y axes of the mask can be set so that they overlap at the same coordinates even if the mask stretches, so the 4 turns of the exposed mask are There is no misalignment at a location extremely close to the mark for aligning the axis and Y axis, and the misalignment increases as the distance increases. However, with step-and-repeat exposure equipment, the coordinates of the center of the transfer pattern that is repeatedly exposed on the wafer can be precisely controlled down to submicron or less, making it possible to
It is possible to adjust the misalignment to zero at the center of each of the 'turn and its mother turn, and it is possible to significantly reduce the misalignment due to expansion and contraction of the mask. It is also possible to automatically calculate the amount of mask elongation and input that data into the exposure equipment's calculator.
The coordinates of the center of the mask and the center of the exposure area can be completely overlapped by moving the mask in the X-axis direction based on the extension and amount of deviation of the mask.

Note that the mask of the exposure apparatus according to the present invention is not limited to the case where the reference mark and the θ angle adjustment mark are arranged so that their connection is at 45 degrees with respect to the X axis as in the above embodiment. As shown in FIG. 9, the reference □ mark 22h and the θ angle adjustment mark 22b' may be arranged so that their connections form a predetermined angle (γ') with respect to the X axis. However, in this case as well, the θ angle adjustment mark 22b has an intersecting shape consisting of a line element 231 oriented in the connection direction and a line element 232 orthogonal thereto.

Also. The mark attached to the stage may have a shape consisting of a line element oriented in the connection direction of the reference mark of the mask and the θ angle adjustment mark, and another line element that intersects this line element. In this way, when aligning the ゛θ angle adjustment mark on the mask with the mark on the stage, align the reference mark on the mask so that one line element of the mark overlaps one line element of the θ angle adjustment mark. Since the masks can be aligned by rotating them around the center, the alignment operation can be made easier.

〔Effect of the invention〕

As described in detail above, according to the present invention, the gyrotation caused by the expansion pressure of the mask in the first step-and-repeat exposure process, and the removal of the base layer formed in the first time on the wafer in the second and subsequent exposure processes are performed. It is possible to provide an exposure apparatus that eliminates rotation of a transfer pattern for four turns and can form a good pattern.

[Brief explanation of the drawing]

Figure 1 is a schematic perspective view showing a step-and-repeat type exposure device, Figure 2 is a plan view showing a conventional mask used in the tight light exposure device shown in Figure 1, and Figure 3 is a schematic perspective view showing a step-and-repeat exposure device. A schematic perspective view showing the step-and-repeat exposure process on a wafer, Figure 4 is a plan view showing the alignment state when there is elongation in a conventional mask, and Figure 5 is a diagram showing wafer rotation when using a conventional mask. Fig. 6 is a plan view showing the relationship between the microscope of the alignment mechanism in the exposure equipment and the alignment mark on the wafer, and Fig. 7 is the microscope when the wafer is rotated. FIG. 8 is a plan view of a mask of an exposure apparatus showing one embodiment of the present invention, and FIG. 9 is a plan view of another embodiment of the present invention. FIG. 1...stage, 2...wafer chuck, 3...
Stage mark, 4... gun barrel, 5... light source, 6...
... Aligning mechanism, 9m, 9b...Microscope, 12...
Wafer, 14a, 14b... alignment mark, 21...
- Mask, 22t... Reference mark, 22b... θ angle adjustment mark, 23y, 23 Island... line element. Applicant's agent Patent attorney Takehiko Suzue 15 1st issue Figure 2 Figure 3 Figure 9

Claims (3)

[Claims] (1) A two-dimensionally movable stage on which a wafer is placed, and an l-) mark attached to this stage,
a lens barrel disposed above the stage; a reference mark placed on the lens barrel on the X coordinate, axis, or Y coordinate axis; and a reference mark θ placed on a coordinate axis different from the mark;
and a mask having an angle adjustment mark, after moving the mark on the stage to a set position under the lens barrel and aligning the reference mark on the mask with the mark on the stage,
In the exposure apparatus, the mark on the stage is moved to the set position again, the mask is rotated by applying central pressure to the reference mark, and the θ angle adjustment mark is aligned with the mark on the stage to align the mask. An exposure apparatus characterized by using a mask having a shape in which an angle adjustment mark is oriented in the connection direction between the mark and the reference mark. (2) The mark on the stage has the shape of crossing the line elements of 2'), the reference mark of the mask has the shape of crossing the two line elements, and the θ angle adjustment mark has the shape of crossing the two line elements. 2. The exposure apparatus according to claim 1, wherein the exposure apparatus has a shape in which the marks intersect and one line element extends long in the connection direction of the mark and the reference mark. (3) The exposure apparatus according to claim 1, wherein the stage is provided with a mark including a line element oriented in the connection direction of the reference mark of the mask and the θ angle adjustment mark.