JP2000150361A - Position measuring method and position measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position measuring method and a device by which the accurate position measurement of a mark for position measurement such as an alignment mark, etc., is possible even in the case that foreign matter such as dust or the like is caught between a wafer and a wafer chuck. SOLUTION: When retaining a water 1 where alignment marks 5 (5a, 5b,...) are made on the surface on a wafer chuck 2 which supports it with plural projections 3 (3a, 3b,...), the alignment marks 5 (5a, 5b,...) are arranged right above the projections 3 (3a,...) of the wafer chuck 2, and the position measurement in the direction parallel with the wafer 1 is performed. As a result, even in the case that foreign matter such as dust or the like intervenes between the wafer 1 and the projection 3, the alignment mark 5 never causes the dislocation within the plane of the wafer, and it is not affected by the existence of the dust, so it becomes possible to measure the position of the alignment mark 5 accurately, and this apparatus can prevent the deterioration of the accuracy in positioning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position measuring method and a position measuring device for a position measuring mark formed on a thin plate-like substrate such as a wafer, and more particularly to an alignment mark formed on a wafer in a semiconductor exposure apparatus. And a position measuring device.

[0002]

2. Description of the Related Art In a semiconductor exposure apparatus, in a process of aligning a circuit pattern formed on a reticle with a circuit pattern on a wafer and performing exposure, a positioning method is performed for each chip in the wafer. And a global method in which the chip arrangement coordinates in the wafer are obtained by measuring the alignment marks of a plurality of chips in the wafer and exposure is performed with stage accuracy in accordance with the obtained arrangement coordinates. At present, the global method is predominant from the viewpoint of throughput, but with the miniaturization of semiconductor elements, higher precision alignment is required.

Further, with the miniaturization of semiconductor elements, the depth of focus of a semiconductor exposure apparatus has been reduced to about 1 μm. With the decrease in the depth of focus, the problem of foreign matter entering between the wafer and the wafer chuck has become more important than ever. If dust having a size of 1 μm is interposed between the wafer and the wafer chuck, local swelling of the wafer occurs in the vicinity thereof, resulting in poor resolution due to defocus. With the miniaturization of semiconductor devices, the depth of focus will become increasingly shallower in the future, and pinching of smaller dust will also be a problem.

In order to reduce the decrease in yield due to such poor resolution, a method has been adopted in which the contact area between the front surface of the wafer chuck and the back surface of the wafer is made as small as possible. A pin chuck having a large number of the following cylindrical projections arranged on the chuck surface at intervals of about 5 mm or less is used.

[0005]

In the above-described pin chuck, it is ideal that the pin and the back surface of the wafer make point contact. However, it is difficult to sharpen the tip of the pin while maintaining the flatness of the chuck. It is technically difficult, and currently the minimum pin diameter is about 0.2 mm. Although the probability of pinching dirt can be greatly reduced by this in comparison with a chuck that holds a wafer on a flat surface, it is still nonetheless. As described above, when dust is caught between the wafer and the wafer chuck, a local swelling of the wafer occurs around the wafer chuck. As shown in FIG.
In (2), a local (non-linear) positional shift dx also occurs in the planar direction due to dust 17 sandwiched between the wafer 1 and the wafer chuck 2.

[0006] Such a displacement dx of the wafer surface is as follows.
For example, as shown in FIG. 4, when dust having a size of 1 μm is interposed, a position shift of about 65 nm occurs at a position about 2 mm from the dust on the wafer surface, and 0.2 μm In the case where dust having a size of is sandwiched, a displacement of about 20 nm occurs at a position about 1 mm from the dust on the wafer surface. FIG. 4 is a table showing the results of actual measurement of the positional shift dx of the wafer surface caused by dust sandwiched between the wafer and the wafer chuck in relation to the size of the dust and the distance x from the dust.

In the conventional position measuring method as described above,
Since the relative relationship between the position of the pin of the pin chuck and the position of the alignment mark on the wafer is not particularly taken into consideration, it is not possible to identify an alignment mark that has been displaced near the pin that has sandwiched dust, As a result of performing array measurement including the alignment mark,
There is a disadvantage that the non-linear error propagates to all chips in the wafer and deteriorates the overlay accuracy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art. It is an object of the present invention to provide a position measuring method and a position measuring device capable of accurately measuring the position of a position measuring mark such as an alignment mark even when the mark is sandwiched.

[0009]

In order to achieve the above object, a position measuring method according to the present invention holds a thin plate-like substrate having a position measuring mark formed on a surface thereof on a substrate holding device which supports the thin plate-like substrate by a plurality of projections. In this case, the position measurement mark of the thin plate-shaped substrate is arranged right above the projection, and the position is measured in a direction parallel to the thin plate-shaped substrate.

In the position measuring method according to the present invention, a plurality of protrusions adjacent to a protrusion of the substrate holding device below an arbitrary position measurement mark among a plurality of position measurement marks formed on the thin plate-like substrate. Measure the height in the direction perpendicular to the thin plate substrate at the position of the thin plate substrate above, and use the position measurement mark for position measurement when each measured value is within the allowable value and in the same plane. Is preferred.

Further, the position measuring device of the present invention comprises: a substrate holding device for supporting a thin plate-shaped substrate having a position measuring mark formed on a surface by a plurality of projections; a moving stage on which the substrate holding device is installed; In a position measuring device comprising measuring means for measuring the position of a position measuring mark on the thin substrate held by the substrate holding device, the position of the position measuring mark and the position of the projection are relatively measured. Means for holding the thin plate-shaped substrate on the substrate holding device so that the position measurement mark can be arranged right above the projection.

In the position measuring device according to the present invention, a plurality of projections adjacent to the projections of the substrate holding device below the predetermined position measurement mark are provided among the plurality of position measurement marks formed on the thin plate-like substrate. It is preferable that the apparatus further comprises a measuring means for measuring a height in a direction perpendicular to the thin plate substrate at a position of the thin plate substrate above.

Further, an exposure apparatus according to the present invention irradiates the position measuring apparatus according to claim 3 or 4 with exposure light to a thin plate-shaped substrate which is positioned by position measurement of a position measuring mark by the position measuring apparatus. An exposure means is provided.

[0014]

According to the position measuring method and the position measuring apparatus of the present invention, the projection of the substrate holding device such as a pin chuck is disposed immediately below the position measuring mark such as an alignment mark formed on a thin substrate such as a wafer. Therefore, even if foreign matter such as dust is sandwiched between the projection and the thin plate-shaped substrate, the position measurement mark does not shift in the substrate plane, and is not affected by the dust being sandwiched. It is possible to measure the position of the measurement mark with high accuracy, and it is possible to prevent deterioration in global alignment accuracy due to a non-linear error caused by dust trapping.

Further, even if dust is inserted between the projection adjacent to the projection immediately below the position measurement mark such as an alignment mark and the thin plate-shaped substrate, even if the position measurement mark is displaced, the position measurement mark is not removed. By measuring the height of the substrate at the position on the protrusion adjacent to the protrusion immediately below the mark and comparing the results, it is possible to confirm the presence or absence of dust entrapment, and perform accurate measurement at a position where there is no dust entrapment be able to.

[0016]

Embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are diagrams showing the relationship between a wafer alignment mark and a projection provided on the surface of a wafer chuck at the time of position measurement according to the present invention, wherein FIG. 1A is a plan view, and FIG. It is sectional drawing, (c) is an expansion schematic diagram which expands and shows a part. FIG. 2 is a schematic configuration diagram of a projection exposure apparatus that can execute the position measurement method of the present invention.

In FIG. 1, a wafer 1 which is a thin plate-shaped substrate is shown.
Is in a state in which an alignment mark 5 as a position measurement mark has already been formed thereon, and each exposure area 4 of the wafer 1 has two alignment marks as shown in FIG. 5 (5a and 5b) are respectively formed. Then, as shown in FIGS. 1 (b) and 1 (c), the wafer 1 at the time of position measurement according to the present invention has an alignment mark 5 (5a in FIG. 1 (c)) formed thereon. , 5b...) Are a plurality of projections 3 provided on the surface of a wafer chuck (substrate holding device) 2.
(In (c), 3a, 3b, 3c,...).
As described above, the position measurement according to the present invention is based on the premise that the alignment mark 5 has already been formed on the wafer 1, and is performed on the second and subsequent layers of the wafer 1.

Next, a projection exposure apparatus capable of implementing the position measuring method of the present invention will be described with reference to FIG. 2. A wafer chuck 2 for mounting a wafer 1 is mounted on a moving stage 7. The moving stage 7 includes a reflection mirror 8
And the laser interferometer 9 measure and position the position with high accuracy. The relative positional relationship between the projection 3 installed on the surface of the wafer chuck 2 and the moving stage 7 may be determined by mechanical accuracy by abutting when the wafer chuck 2 is mounted on the moving stage 7 or by a separately provided measuring device (not shown). ) Is measured in advance (with an accuracy of about 50 μm) and stored as position information. Note that the wafer chuck 2
Of the projections 3 of the alignment mark 5 of the wafer 1
In the case where the pitch of the alignment marks 5 changes depending on the stroke, a wafer chuck in which the pitch of the projections 3 is adjusted to correspond to the pitch of the alignment marks 5 is prepared.

Reference numeral 6 denotes a projection lens, and reference numerals 10 and 11
Denotes a stage surface plate and a base surface plate, and 12 denotes a pre-alignment device installed on the base surface plate 11,
A pre-alignment stage driving device 13, a pre-alignment stage 14, and a position sensor 15 are provided. Reference numeral 16 denotes a robot hand.

Next, the loading of the wafer into the projection exposure apparatus and the position measurement will be described.

The wafer 1 is placed on a pre-alignment stage 14 by a robot hand (not shown) from a wafer cassette (not shown). The pre-alignment stage 14 detects the orientation flat and the outer periphery of the wafer, and performs pre-alignment so that when the wafer 1 is mounted on the wafer chuck 2, the positions of the orientation flat and the outer periphery are accurately positioned at predetermined positions. Pre-alignment accuracy is
It can be reproduced with an alignment accuracy of about 20 to 60 μm.

The wafer 1 after the pre-alignment is
The wafer hand 2 is placed on the wafer chuck 2 at a predetermined position in advance by the robot hand 16. At this time, the position of the wafer 1 and the alignment mark 5 on the wafer 1 may be measured in advance by another measuring means outside the process or by installing another measuring means (not shown) in the pre-alignment apparatus 12. As a result, the alignment mark 5 is positioned on the projection 3 of the wafer chuck 2 as shown in FIG. 1 in accordance with the position of the projection 3 provided on the surface of the wafer chuck 2 and the relative positional relationship of the moving stage 7. Like wafer 1
Is placed. Here, it is not necessary that the projections 3 come under all the alignment marks 5 formed on the wafer 1, and at least the projections 3 come under the minimum necessary alignment marks 5 for position measurement. good.

After the wafer 1 is placed on the wafer chuck 2 as described above, the position of the predetermined alignment mark 5 is measured.

When the position of the alignment mark 5 is measured, if foreign matter such as dust is trapped between the wafer 1 and the projections 3, as described above, a positional shift occurs on the wafer surface according to the size of the dust. However, if the trapped dust is below the alignment mark 5, the alignment mark 5 itself does not have a position shift and the position can be measured without being affected by the dust, as is apparent from FIG. Therefore, although there is a possibility that the overlay accuracy may be slightly deteriorated in the chip area near the interposed dust, the error does not propagate to other chip areas due to global alignment. By positioning the projection 3 of the wafer chuck 2 immediately below the alignment mark 5 formed on the wafer 1, the projection 3
Even if dust is interposed between the wafer and the wafer 1, the alignment mark 5 does not shift in the wafer plane and is not affected by the dust, so that the position of the alignment mark 5 can be accurately determined. Measurement can be performed, and deterioration of global alignment accuracy due to a non-linear error due to dust trapping can be prevented.

Depending on the size of the dust and the pitch of the projections 3, for example, in FIG. 1C, the projection 3c on the right of the projection 3a below the alignment mark 5a and the wafer 1
When the dust is sandwiched between them, there is a possibility that the alignment mark 5a is misaligned. Therefore, in such a case, for example, the projections 3b, 3c, 3d adjacent to the projection 3a below the alignment mark 5a are provided by a multi-point automatic focusing device (not shown) provided in a conventional exposure apparatus. And the plane position is measured at four points on the wafer surface on 3e. As a result of this measurement,
If the points deviate from the plane determined by the remaining three points by an allowable value or more, there is a possibility that dust is sandwiched in any one of the four points, and the alignment mark 5a may be misaligned. is there. Therefore, it is possible to add a step of removing the alignment mark 5a from the measurement relating to the global alignment and, if necessary, selecting another alignment mark relating to the position measurement. As a result, it is possible to perform position measurement at a position where dust is not pinched, and more accurate position measurement is possible.
Global alignment accuracy can be improved.

It is to be noted that five points including the position of the alignment mark 5a (that is, the protrusion 3a below the alignment mark 5a and the protrusion 3b adjacent thereto in FIG.
If the same measurement is performed at (5 points on the wafer surface on 3c, 3d, and 3e), it is possible to detect the entrapment of dust under the alignment mark 5a. As described above, the pinching of dust between the projection below the alignment mark and the projection adjacent to the projection and the wafer can be detected. Therefore, when the pinching of dust is detected at the same position even when the wafer is changed, the projection of the wafer chuck is detected. There is also an effect that it is possible to know that dust has adhered, and to know the timing of cleaning the wafer chuck. In addition, since the size of dust and the like vary depending on the environment where the exposure apparatus is placed and the semiconductor manufacturing process, these processes can be appropriately adopted according to each environment and the semiconductor manufacturing process.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 5 shows a micro device (a semiconductor chip such as an IC or an LSI, a liquid crystal panel, a CC).
D, thin-film magnetic head, micromachine, etc.). In step S1 (circuit design), a device pattern is designed. In step S2 (mask production), a mask on which the designed pattern is formed is produced. on the other hand,
In step S3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step S4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step S5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step S4. including. Step S6 (inspection)
Then, inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step S5 are performed. Through these steps, a semiconductor device is completed and shipped (step S7).

FIG. 6 shows a detailed flow of the wafer process. In step S11 (oxidation), the surface of the wafer is oxidized. In step S12 (CVD), an insulating film is formed on the wafer surface. In step S13 (electrode formation), electrodes are formed on the wafer by vapor deposition. Step S1
In step 4 (ion implantation), ions are implanted into the wafer. In step S15 (resist processing), a resist is applied to the wafer. In step S16 (exposure), the circuit pattern of the mask is printed on a plurality of shot areas of the wafer by printing using the exposure apparatus described above. Step S17
In (development), the exposed wafer is developed. Step S1
In step 8 (etching), portions other than the developed resist image are removed. In step S19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using such a device manufacturing method, it is possible to manufacture a highly integrated device which has been conventionally difficult to manufacture at low cost.

[0031]

As described above, according to the present invention,
Since the projection of the substrate holding device such as a pin chuck is placed directly below the position measurement mark such as the alignment mark formed on the thin substrate such as a wafer, foreign matter such as dust is placed between the projection and the thin substrate. Even in the case of being pinched, the position measurement mark does not shift in the plane of the substrate and is not affected by dust, so that the position of the position measurement mark can be measured with high accuracy. Can be prevented from deteriorating the global alignment accuracy due to non-linear errors caused by pinching.

Further, even if dust is sandwiched between the projection adjacent to the projection immediately below the position measurement mark such as an alignment mark and the thin plate-shaped substrate, even if the position measurement mark is misaligned, The height of the substrate is measured at the position on the protrusion adjacent to the protrusion immediately below the mark, and the presence or absence of dust can be confirmed by comparing the heights of the substrates. The measurement can be performed at a position where no dust is trapped. . Furthermore, since the pinching of dust between the projection below the position measurement mark and the projection adjacent to the projection and the sheet-like substrate can be detected, when the pinching of dust is detected at the same position even when the sheet-like substrate is replaced, It can be seen that dust is attached to the projections of the substrate holding device such as the wafer chuck, and the time for cleaning the substrate holding device can be known.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a relationship between a wafer alignment mark and a projection provided on the surface of a wafer chuck at the time of position measurement according to the present invention, wherein FIG. 1A is a plan view and FIG. FIG. 4C is an enlarged schematic diagram showing a part of the structure.

FIG. 2 is a schematic configuration diagram of a projection exposure apparatus that can execute the position measurement method of the present invention.

FIG. 3 is a schematic diagram showing a state when foreign matter such as dust enters between a wafer and a wafer chuck.

FIG. 4 is a table showing a result of actually measuring a positional shift dx of a wafer surface caused by dust sandwiched between a wafer and a wafer chuck with respect to a distance x from the dust.

FIG. 5 is a flowchart showing a semiconductor device manufacturing process.

FIG. 6 is a flowchart showing a wafer process.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 wafer (thin plate-like substrate) 2 wafer chuck (substrate holding device) 3 projection 4 exposure area 5 alignment mark (position measurement mark) 6 projection lens 7 moving stage 8 reflection mirror 9 laser interferometer 10 stage base 11 base base 12 Pre-alignment device 13 Pre-alignment stage drive device 14 Pre-alignment stage 15 Position sensor 16 Robot hand 17 Dust (foreign matter)

Claims (5)

[Claims] When holding a thin substrate having a position measurement mark formed on a surface thereof on a substrate holding device that supports the plurality of projections, the position measurement mark on the thin plate substrate is fixed to the position of the projection. A position measurement method, wherein the position measurement is performed in a direction parallel to the thin plate substrate. 2. A plurality of position measurement marks formed on a thin plate-like substrate, wherein the plurality of position measurement marks are located on a plurality of protrusions adjacent to a protrusion of a substrate holding device below an arbitrary position measurement mark. A height of a position in a direction perpendicular to the thin substrate is measured, and the position measurement mark is used for position measurement when each measured value is within an allowable value and is on the same plane. 1. The position measuring method according to 1. 3. A substrate holding device for supporting a thin plate-shaped substrate having a position measurement mark formed on its surface by a plurality of projections, a moving stage on which the substrate holding device is installed, and a substrate held by the substrate holding device. A position measuring device comprising a measuring unit for measuring the position of the position measuring mark on the thin plate-shaped substrate, comprising: a unit for relatively measuring the position of the position measuring mark and the position of the projection; A position measuring device, characterized in that the position measuring mark is configured to be arranged directly above the projection when the substrate is held on the substrate holding device. 4. A plurality of position measurement marks formed on the thin plate-like substrate, wherein the plurality of position measurement marks of the thin plate-like substrate on a plurality of protrusions adjacent to a protrusion of the substrate holding device below a predetermined position measurement mark are provided. 4. The position measuring device according to claim 3, further comprising a measuring means for measuring a height in a direction perpendicular to the thin plate-shaped substrate at a position. 5. A position measuring device according to claim 3, further comprising: an exposing means for irradiating the thin plate-shaped substrate, which is positioned by the position measuring device with position measurement of the position measuring mark, with exposure light. Exposure equipment characterized.