JPH0837148A - Patterning method by stepwise moving projection exposure apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] A long and narrow pattern can be projected and exposed at a sufficiently large reduction ratio, and therefore fine patterning can be performed with high accuracy. In a patterning method in which the same unit pattern 12 is successively exposed on a single wafer 2 by a sequential movement type projection exposure apparatus, one unit pattern is formed on a single photomask in a plurality of patterns. The divided patterns 12a and 12b are separately formed, and exposure is performed so that each divided pattern is adjacent and continuous to form one unit pattern on the wafer, whereby patterning for one unit is performed. At this time, the mark pattern 13 for measuring the positional deviation between the adjacent patterns is formed in the interconnection portion of each divided pattern.
a and 13b are included, the measurement mark 15 formed by the pattern is observed after development to measure the positional deviation, and the data is used to control the position of the sequential movement type projection exposure apparatus in the subsequent patterning step. Correction information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a patterning method by a sequential movement type projection exposure apparatus which is widely used in the manufacturing process of various microcircuits such as integrated circuits and thin film magnetic heads.

[0002]

2. Description of the Related Art In a manufacturing process of various microcircuits such as integrated circuits and thin film magnetic heads, a patterning process by a successive movement type projection exposure apparatus (called a stepper) is performed many times. The basis of such patterning is a process of exposing a circuit pattern or a mechanism pattern on a photoresist applied on a wafer by using an exposure device to develop it, and selectively removing the resist to obtain a resist film according to the exposure pattern. is there.

The successive-moving projection type exposure apparatus is an apparatus for exposing the same circuit pattern one after another while shifting the position on the same wafer, and reduces or reduces the size of the circuit pattern image of the photomask. It basically comprises an optical system for projecting onto the wafer and a numerically controlled positioning displacement mechanism for relatively precisely moving the position of the wafer.

Further, in order to form a fine pattern (including a circuit pattern and a mechanism pattern) on a wafer with high accuracy, it is better that the pattern size of the photomask is larger than the actual size of the pattern on the wafer ( The large enlargement ratio of the mask pattern with respect to the actual size is the same as the large reduction ratio during exposure). However, there is a limit to the size of the effective exposure area on the mask surface of the exposure apparatus, so use a photomask with a pattern expansion ratio as large as possible within the effective exposure area of the apparatus used to perform highly accurate patterning. I have to.

[0005]

The effective exposure area of the mask surface in a normal exposure apparatus is a square, and if the circuit pattern to be patterned is a square, the effective exposure area can be utilized without waste and the enlargement ratio as large as possible. A mask pattern can be designed. However, when exposing a pattern with a long and narrow external shape having a large aspect ratio, if the enlargement ratio of the mask pattern is made sufficiently large, the long side dimension of the long and narrow mask pattern will protrude from the square effective exposure area. Even if there is an unused area, the enlargement ratio of the mask pattern must be set small so that the long side dimension of the elongated mask pattern fits within the effective exposure area. Therefore, it is impossible to project and expose a long and narrow pattern at a sufficiently large reduction rate, and it is difficult to perform fine patterning with high accuracy.

The present invention has been made in view of the above background, and an object of the present invention is to solve the above problems and perform projection exposure of a long and narrow pattern at a sufficiently large reduction rate. To provide a patterning method by a sequential movement type projection exposure apparatus capable of performing fine patterning with high accuracy and further performing quality control during or after product production as needed. is there.

[0007]

In order to achieve the above object, in the patterning method by the sequential movement projection type exposure apparatus according to the present invention, the same unit pattern is formed on one wafer by the sequential movement projection type exposure apparatus. In the patterning method that exposes one after another while shifting the position above, 1
One unit pattern is divided into a plurality of divided patterns and formed on one photomask, and the divided patterns are exposed a plurality of times while shifting the positions so that the divided patterns are adjacent and continuous to form one unit pattern. By doing so, patterning for one unit is performed, and the interconnecting portion of each divided pattern is provided with a mark for measuring the positional deviation between the adjacent patterns, and the positional deviation between the adjacent patterns is measured by the mark after development. Then, the positional deviation data is used as correction information for position control of the sequential movement projection exposure apparatus in the subsequent patterning process.

As the position deviation measuring mark, for example, a double concentric mark composed of two adjacent division patterns can be used. Further, as another configuration, scale marks slightly different in pitch formed on two adjacent division patterns may be adjacent to each other.

[0009]

The unit pattern is divided into a plurality of divided patterns on the photomask. However, by sequentially exposing the images of the divided patterns while shifting the position of the wafer, the divided patterns are continuously adjacent to each other on the wafer. Then, the exposure of the target unit pattern is performed. At this time, it is important that each of the divided patterns is continuous with high precision on the wafer without misalignment with each other.
High accuracy can be realized by measuring the positional deviation of a certain work and using the data as correction information for position control at the time of patterning the next work.

Further, generally, the above-mentioned positional deviation is different at each unit pattern forming position on the wafer. Therefore, in order to perform more accurate position control (correction), all the pattern formation positions are actually exposed in advance by using a dummy wafer to manufacture a pattern, and the measurement marks formed at the same time are measured. The positional deviation of the exposure (shot) at each position on each wafer of the used exposure apparatus is obtained and stored. Then, the position control is performed using the correction value for each position.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a patterning method using a successive movement projection type exposure apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an example of an exposure apparatus for carrying out this embodiment. As shown in the figure, this exposure apparatus (stepper) places a wafer 2 on an XY stage 1 and is movable in a horizontal plane, and is moved in a predetermined direction by a predetermined step width. However, the mask pattern 4 formed on the mask 3 is transferred (exposed) to each position on the wafer 2. That is,
The light emitted from the light source 5 is made parallel and high-speed by the lens 6 and transmitted through the mask 3, and further passes through the reduction projection lens 7, whereby a reduced pattern similar to the pattern 4 formed on the mask 3 is formed on the wafer 2 A predetermined position of the resist applied above is irradiated and exposed.

Further, the XY stage 1 receives a control signal from the XY stage drive / control unit 8 and is moved by a predetermined pitch in a predetermined direction each time the above-mentioned one exposure process is completed. It has become. As a result, the exposure process is performed using the same mask 3 at all locations in the wafer-shaped pattern formation area, and the same pattern is formed.

By the way, XY in the above exposure apparatus
The movement distance of the stage 1 has an accuracy error of about ± 0.1 to 0.2 μm. Then, due to the accuracy error, a position shift occurs when the pattern is actually exposed on the wafer 2. However, according to what the present inventors have learned,
Such positional deviation is peculiar to the apparatus and is different at each position of the wafer 2. Further, it has been found that, although the positions are different at each place, the position deviation and the distance at the same place are almost the same every time.

Therefore, in the present invention, the XY stage drive
When the correction information memory 9 is connected to the control unit 8 and correction information based on the positional deviation at each place is stored and the XY stage 1 is moved for exposure processing, the correction information is stored. In consideration of this, drive control is performed so that the pattern can be exposed at the correct position on the wafer 2. Reference numeral 10 in the drawing is an input device, and the correction value is stored in the correction information memory 9. Further, the correction information memory 9 also needs to store the pattern formation position information corresponding to the correction value in a pair, which is also performed via the input device 10.

Next, a specific example will be described. Figure 2
In the example of (A), the square 3'is an effective exposure area on the mask surface in the exposure apparatus. Further, the rectangle of reference numeral 12 is a unit pattern of the photomask created with a desired enlargement ratio in terms of accuracy. Since the long-side dimension of the elongated unit pattern 12 is larger than the effective exposure area 3'and the pattern 12 protrudes from the area 3 ', patterning cannot be performed with this mask pattern enlargement ratio.
Therefore, conventionally, patterning is performed by reducing the enlargement ratio of the mask pattern.

However, in the present invention, as shown in FIG. 1B, the elongated unit pattern 12 having a large enlargement ratio.
Is divided into two into the divided patterns 12a and 12b from the center, and a photomask in which the divided pattern 12b is arranged under the divided pattern 12a is created so that the divided patterns 12a and 12b can be simultaneously accommodated in the square effective exposure area 3 '. To do.

Then, as illustrated in FIG. 1C, in order to pattern the unit pattern 12 on the wafer 2 once, first, the image of the divided pattern 12a is formed on the wafer 2 with the divided pattern 12b of the photomask shielded. The upper surface is exposed (the pattern formed on the wafer 2 by this exposure is referred to as an actual pattern 14a). Next, when the XY stage is moved in a predetermined direction in response to a control signal from the XY stage drive / control unit 9, the wafer 2 is two-dimensionally displaced by a predetermined amount. Then, the division pattern 12a of the photomask
The image of the divided pattern 12b is exposed on the wafer 2 in a state of being shielded from light (the pattern formed on the wafer 2 by this exposure is referred to as an actual pattern 14b). As a result, the actual patterns 14a and 14b are formed so as to be aligned in a straight line, and an elongated actual pattern corresponding to the unit pattern 12 is formed.

As described above, in this example, one unit pattern is formed on the wafer 2 by two exposure operations. Therefore, the same operation is performed successively while shifting the position of the wafer 2 as shown in FIG. As illustrated in FIG. 2, a large number of unit patterns including the real patterns 14a and 14b can be formed on the wafer 2.

What is important here is that the actual pattern 14a and the actual pattern 14b are accurately adjacent to each other and continuous, and the actual pattern corresponding to the above-mentioned unit pattern is accurately formed. For that purpose, it is necessary to accurately control the two-dimensional movement amount of the wafer 2 when shifting from the first exposure to the second exposure, which is one of the features of the present invention.

Therefore, the positioning control of the wafer 2 when forming one unit pattern by two exposure operations will be described in detail. First, two divided patterns 12 on the photomask
It is possible to calculate how much the wafer 2 must be moved in the second exposure from the arrangement dimensions of a and 12b, the dimensions of both divided patterns, the projection reduction rate, and the like.
A program for a numerical controller (actually, this numerical controller is built in the XY stage drive / control unit 9) is built in accordance with the calculation result. Then, the XY stage drive / control unit 9 moves the XY stage 1 in a predetermined direction based on the calculation result of the numerical controller, but sufficient accuracy is realized only by such open loop control. Since it is difficult to do so, the following correction control is also performed.

That is, as shown in FIG. 2B, mark patterns 13a and 13b for measuring the positional deviation between the adjacent patterns are formed in the interconnected portions of the divided patterns 12a and 12b. Then, when the patterning of a certain wafer 2 is completed and developed, a measurement mark 15 is formed on the boundary line between the two actual patterns 14a and 14b as shown in FIG. Then, after that, the actual pattern on the wafer 2 is observed with a microscope or the like, and the positional deviation between the adjacent patterns is measured by the measurement mark 15 included in the pattern. Then, from this measurement result, the wafer 2
The correction amount of the movement control is calculated and stored in the correction information memory 9 together with the position information via the input device 10.

In the next patterning step for the work, the numerical controller is operated with the correction amount added. Thus, by sequentially correcting the work movement amount based on the actual positional deviation, it is possible to realize highly accurate patterning. An example of the measurement mark 15 and a pattern for forming the measurement mark 15 is shown in FIG.

That is, as shown in FIG. 4A, a square pattern 1 is formed on the boundary line of one of the divided patterns 12a.
3a is formed, and a square-shaped pattern 13b is formed on the boundary line of the other divided pattern 12b. Then, each of the patterns 13a and 13b is line-symmetrical at each boundary line,
The boundary lines are formed so that their centers coincide with each other when they are connected to each other, that is, when they are exposed in a normal state. Further, the hatched portion in the figure is a portion shielded from light by a metal or the like.

The predetermined positions on the wafer 2 corresponding to the patterns 13a and 13b are exposed by two exposure operations, but the patterns 13a and 13b are located on the boundary line of the divided patterns 12a and 12b. ,
Eventually, a portion which has been subjected to multiple exposure and which has not been irradiated with light even once by the two exposure operations becomes the measurement mark 15.

As a result, a square double concentric mark formed by two adjacent divided patterns is formed after development, as shown in FIG. The outer contour line 15a is formed by the mark included in the divided pattern 12a, and the inner contour line 15b is formed by the mark included in the divided pattern 12b. If the actual pattern 14a of the divided pattern 12a and the actual pattern 14b of the divided pattern 12b are accurately continuous, the outer contour line 1
5a and the inner contour line 15b are accurately concentric. Therefore, by measuring the distance Dx in the X-axis direction and the distance Dy in the Y-axis direction between the contour lines 15a and 15b, the shift amount in the X-axis and Y-axis directions can be obtained.

Since the complement of the amount of deviation in each axial direction becomes the correction value, this value is stored in the correction information memory 9 via the input device 10 together with the measurement position (address). Then, in the memory, the data is stored and held in the form of a table as shown in FIG. 5, for example, and in the subsequent exposure processing, XY
The table drive / control section 8 makes an access based on the position (address) at which exposure is used, and the correction value paired therewith is read out.

Further, the positional deviation measuring mark is not limited to the above-mentioned one, and for example, a mark as shown in FIG. 6 can be used. In the example shown in the figure, the graduation marks with slightly different pitches, which are respectively formed in the two divided patterns, are arranged so as to be adjacent to each other on the wafer 2. That is, as shown in FIG. 7A, the X-axis scale mark patterns 17a and 17b and the Y-axis scale mark patterns 16a and 16b are formed at predetermined positions on the boundary between the divided patterns 12a and 12b. Also in this example, the hatched portion is a portion that is coated with metal and shielded from light. Then, the vicinity of the boundary line is subjected to multiple exposure, so that a predetermined mark is formed in a portion that has never been irradiated with light.

That is, the X-axis scale mark 19a included in the actual pattern 14a and the X-axis scale mark 19b included in the actual pattern 14b are adjacently opposed to each other, and both actual patterns 14a,
Y-axis scale marks 18a, 18b so as to straddle 14b
And are adjacent to each other. The pair of graduation marks functions similarly to a vernier caliper or micrometer graduation, and by observing the marks with a microscope or the like, even if there is no separate distance measuring graduation means, the object to be measured itself is used for distance measurement. Since there is a scale, the above-mentioned displacement measurement can be easily performed. In addition, each mark 18
The marks a, 18b, 19a, and 19b have at least the length of the mark at the reference position increased to clarify the zero point position.

FIG. 7 shows a specific example of a real pattern divided into two obtained by implementing the present invention. In this example,
An example of manufacturing a head element pattern of a thin film magnetic head is shown. As is well known, in the thin film magnetic head, each head element pattern 20 is formed in a predetermined number in a horizontal row.
Dummy marks 21 are formed at both ends of the dummy marks 21 as reference positions for cutting. Then, the dummy marks 21 at both ends are cut while monitoring the cutting state by visual observation with a microscope or by measuring resistance, so that parallel alignment is performed. As a result, the gap depth length of each head element pattern 20 can be made constant, but as a prerequisite for this, each head element pattern 20 must be aligned in the lateral direction.

Therefore, as in the present invention, the left half is exposed by one of the divided patterns 12a 'and the right half is exposed by the other divided pattern 12'b, and the pattern is manufactured based on the exposed half, and the divided portions are formed. Then, the positions of the four head element patterns and the dummy patterns are maintained with high accuracy by the photomask, and the actual patterns manufactured by the two divided patterns are also accurately positioned by the above correction process. Delivering is done.
Therefore, the positional accuracy of the head element patterns arranged side by side becomes accurate, and by performing parallel alignment with the dummy marks with high accuracy, the gap depth length of each head element pattern can be made equal. Reference numeral 22 in the figure is a measurement mark.

In addition, in each of the above-described embodiments and the like, an example is described in which each is divided into two, but in the present invention, of course, it may be divided into three or more.

[0032]

As described above, in the patterning method using the sequential movement type projection exposure apparatus according to the present invention, the unit pattern is divided into a plurality of divided patterns on the photomask, but the position of the wafer is shifted. By sequentially exposing the images of the divided patterns, the divided patterns are adjacent and continuous on the wafer, and the target unit pattern is exposed. At this time, it is important that each divided pattern continues on the wafer with high accuracy without misalignment, but the misalignment of a workpiece is measured using the misalignment measurement mark, and the data is By using it as correction information for position control at the time of patterning a work, high accuracy can be realized. That is, a long and narrow pattern can be projected and exposed with a sufficiently large reduction rate, and thus fine patterning can be performed with high accuracy.

Furthermore, by forming the above-mentioned measuring marks even during the actual production of the product, the dimensional accuracy can be inspected during or after the production of the final product. That is, it can also be used as a mark for quality control.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a patterning method of the present invention.

FIG. 2 is an explanatory diagram of a first embodiment of a position shift measuring mark according to the present invention.

FIG. 3 is an explanatory diagram of a second embodiment of the positional deviation measuring mark according to the present invention.

[Explanation of symbols]

2 wafer 3'effective exposure area on mask surface 12 unit pattern 12a, 12b division pattern 14a actual pattern by division pattern 12a 14b actual pattern by division pattern 12b 15a, 15b, 18a, 18b, 19a, 19b misalignment measurement mark

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[Procedure amendment]

[Submission date] March 10, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out a patterning method of the present invention.

FIG. 2 is a diagram illustrating a first embodiment of the present invention.

FIG. 3 is a diagram illustrating a first embodiment of the present invention.

FIG. 4 is an explanatory diagram of misalignment measurement marks used in the first embodiment of the present invention.

FIG. 5 is a diagram showing a memory structure of a correction information memory.

FIG. 6 is an explanatory diagram of misalignment measuring marks used in the second embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of an actual usage mode of the present invention.

[Explanation of Codes] 2 Wafer 3 ′ Effective Exposure Area on Mask Surface 12 Unit Pattern 12a, 12b Divided Pattern 14a Actual Pattern with Divided Pattern 12a 14b Actual Pattern with Divided Pattern 12b 15a, 15b, 18a, 18b, 19a, 19b Misalignment Measurement mark

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03F 9/00 H

Claims (3)

[Claims] 1. A patterning method in which the same unit pattern is exposed one after another while shifting the position on a single wafer by a sequential movement type projection exposure apparatus. The divided patterns are separately formed, and one unit of patterning is performed by exposing the divided patterns a plurality of times while shifting the positions so that the divided patterns form one continuous unit pattern adjacent to each other. , The interconnecting portion of each divided pattern includes a mark for measuring the positional deviation between the adjacent patterns, the positional deviation between the adjacent patterns is measured by the mark after development, and the positional deviation data is used in the subsequent patterning step. According to the sequential movement type projection exposure apparatus, which is used as correction information for position control of the sequential movement type projection exposure apparatus in Turning way. 2. The displacement measurement marks are adjacent to each other.
2. The patterning method by the sequential movement projection type exposure apparatus according to claim 1, wherein the pattern is a double concentric mark composed of one division pattern. 3. The misalignment measurement marks are adjacent to each other.
2. The patterning method according to claim 1, wherein the scale marks, which are formed on each of the divided patterns and have slightly different pitches, are adjacent to each other.