JPH09186222A - Aligner and alignment method, and exposure apparatus and manufacture of device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable alignment of high accuracy regardless of misalignment between a mask and a wafer or misalignment of a projected beam in an aligner. SOLUTION: An aligner detects, by means 1, each of positions of center of gravity of mark position detection signal beams generated by irradiating marks on a first object and a second object with a light beam and reflecting or diffracting the light by the marks, then finds an alignment amount based on these positions of center of gravity, and performs alignment between the first object and the second object. In this aligner, means 2 is provided for finding a correction amount for the alignment amount based on the positional relation between the first object and the second object or the positional relation between the irradiation luminous flux and the first object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic alignment apparatus, for example, in an exposure apparatus for manufacturing a semiconductor element, when a fine electronic circuit pattern formed on the mask is transferred onto the wafer by exposure, The present invention relates to an alignment device that corrects a relative positional deviation with respect to.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a conventional alignment method using two grating lenses.

An alignment method is disclosed in Japanese Patent Laid-Open No. 2-1.
As proposed in Japanese Laid-Open Patent Publication No. 506, a grating lens pattern is arranged on each of a mask and a wafer, a light beam emitted from two grating lenses is received by a line sensor, and based on a difference in barycentric position of the spots. The amount of misalignment between the mask and the wafer is calculated. In addition, each spot is a sum of lights passing through two different optical paths (110 diffraction and 011 diffraction).

[0004]

However, in such a method, the distance between the mask and the wafer (hereinafter, referred to as
When the gap between the mask and the wafer changes due to the driving device that adjusts the gap) and the mechanical accuracy of the alignment head that incorporates the light projecting system and the light receiving system, the two diffracted lights (110) that form the respective spots are formed. The position of the center of gravity of the spot on the alignment sensor fluctuates due to the difference in magnification between diffraction and 011 diffraction) and the influence of interference, and the accuracy of the relative positional deviation amount between the mask and the wafer deteriorates. Further, even if the projected beam position fluctuates relative to the mask, the spot gravity center position also fluctuates, and the accuracy of the relative positional deviation amount between the mask and the wafer deteriorates. The contribution of the gap deviation and the projection beam position deviation to the alignment accuracy of the mask and the wafer is non-linear because the physical phenomenon of the optical system is complicated, and it is difficult to easily obtain the correction amount.

In view of the above problems of the prior art, an object of the present invention is to provide an alignment apparatus regardless of the positional deviation between the mask and the wafer and the positional deviation of the projection beam.
It is to enable more accurate alignment.

[0006]

In order to achieve this object, in an alignment apparatus and method of the present invention, and in an exposure apparatus and device manufacturing method to which they are applied, a first object such as a mask and a second object such as a wafer are provided. The upper mark is irradiated with a light flux, and the respective barycentric positions of the mark position detection signal light generated when the light beam is reflected or diffracted by those marks are detected, and the alignment amount is obtained based on these barycentric positions, and the first object and When performing alignment with the second object, a correction amount for the alignment amount is obtained based on the positional relationship between the first object and the second object or the positional relationship between the irradiation light beam and the first object. The correction amount can be obtained by, for example, fuzzy inference.

Further, the correction amount is represented by a linear function of the alignment amount, and its gain and offset are the gap deviation between the first object and the second object, the irradiation light flux, and the first light flux.
It can be determined by fuzzy reasoning based on the displacement between the marks of the object.

[0008]

In this structure, the alignment amount obtained based on the position of the center of gravity of the mark position detection light is determined by the first object and the second object.
Although it changes depending on the positional relationship between the objects and the positional relationship between the irradiation light flux and the first object, accurate alignment is performed by correcting the alignment amount with the correction amount obtained based on these positional relationships.

[0009]

The present invention will be described in more detail with reference to the drawings.

FIG. 1 is a block diagram showing an alignment apparatus according to an embodiment of the present invention.

This device is different from the conventional one in that a correction amount calculating means 2 is added to the conventional center of gravity calculating means 1 and a second alignment amount is obtained by an adding circuit 3.

FIG. 2 is a block diagram showing a detailed configuration of the correction amount calculation means 2 in the block diagram of FIG. In this apparatus, in the correction amount calculating means 2, for example, a gap deviation ΔG which is a deviation from a predetermined gap between the mask and the wafer and a relative position deviation M / P of the projection beam with respect to the mask are input as external signals, A correction amount is obtained using fuzzy inference, and the first alignment amount is corrected by the correction amount. At that time, the correction amount is a linear function of the own signal (here, the first alignment amount), and the gain a and the offset b of the correction straight line are inputted with the external signal (here, M / P, ΔG). It is decided by the fuzzy reasoning.

From the results of the analysis so far, it is possible to qualitatively grasp the tendency of the characteristic data of the first alignment amount between the mask and the wafer when the gap shift ΔG and the relative position shift M / P of the projection beam are changed. . Gap deviation ΔG
Further, the gain a and the offset b of the alignment correction straight line are determined by the relative position deviation M / P of the projected beam. The rule of thumb is expressed as rules (1) to (9).

(1) if ΔG = NB M / P = NB then a = a1 b = b1 (2) if ΔG = NB M / P = ZE then a = a2 b = b2 (3) if ΔG = NB M / P = PB then a = a3 b = b3 (4) if ΔG = ZE M / P = NB then a = a4 b = b4 (5) if ΔG = ZE M / P = ZE then a = a5 b = b5 (6 ) If ΔG = ZE M / P = PB then a = a6 b = b6 (7) if ΔG = PB M / P = NB then a = a7 b = b7 (8) if ΔG = PB M / P = ZE then a = A8 b = b8 (9) if ΔG = PB M / P = PB then a = a9 b = b9 Here, the rule (1) will be described as an example.

In the same rule, "if" to "the"
The part up to "n" is called the antecedent part, and the part after "then" is called the consequent part. PB, ZE expressed by the antecedent part
The symbols NB and NB mean a membership function in which PB: external signal is positive and fairly large, Z: external signal is near 0, and NB: external signal is negative and fairly large.

The contents of the antecedent part are shown in FIG.
It is stored as a membership function as shown in (A) to (C) and FIGS. 4 (A) to (C).

In FIG. 3A, the antecedent part shown above is ΔG = N.
In the case of B, the membership function is shown. The horizontal axis is the gap deviation ΔG between the mask and the wafer, the vertical axis is the degree (grade) used in the fuzzy set, and the members take values between 0 and 1. This is a concrete example of the ship function. Similarly, when ΔG = ZE and ΔG = PB, the membership functions as shown in FIGS. 3B and 3C are taken.

Similarly, FIGS. 4 (A) to 4 (C) show the membership function relating to the deviation M / P between the mask and the projection beam position in the antecedent part.

The consequent parts a1 to a9 and b1 to b
For 9, the value is read from the measurement data and stored in the signal processing unit.

In FIG. 5, as an example, using fuzzy reasoning, ΔG is g0 (g1 <g0 <g2) and M / P is β0.
It is a figure for demonstrating the inference method in the case of ((beta) 1 <(beta) 0 <(beta) 2). As shown in the figure, when ΔG is g0 and M / P is β0, the inference rule is the following rule (1),
(2), (4) and (5) apply.

(1) if ΔG = NB M / P = NB then a = a1 b = b1 (2) if ΔG = NB M / P = ZE then a = a2 b = b2 (4) if ΔG = ZE M / P = NB then a = a4 b = b4 (5) if ΔG = ZE M / P = ZE then a = a5 b = b5 First, regarding rule (1), in the antecedent part 2.2c, the gap g0 is The degree of belonging to NB is g0 and ΔG
From the intersection with the membership function NB of Similarly, the degree that β0 belongs to NB is h12 from the intersection of β0 and the membership function NB of M / P. The smaller one of them is defined as the goodness of fit h1 (h11∧h12) with the antecedent part of the rule (1).

Then, in the consequent processing unit 2.3c,
The heights of the consequent parts a1 and b1 are each multiplied by h1.

After repeating the same processing up to the rule (5), the final conclusion, that is, the gain a0 of the alignment correction line and the offset b0 are the weighted average portion 2.4c.
In, ai and bi are weighted averaged with the goodness of fit hi, and
It is calculated by a formula.

[0024]

[Equation 1] Therefore, the final correction amount ΔAA is given by the equation (2).

[0025]

[Equation 2] The detection accuracy of the alignment mark position obtained by the method of the present embodiment is shown in Table 1 in comparison with the conventional example.

[0026]

[Table 1] In this embodiment, it is not necessary to have all the correction amounts for ΔG or M / P in a table, and only the optimum values at some representative points are adjusted by trial and error,
The adjustment value is interpolated by the membership function. Compared with brute force adjustment of all points, this saves labor and is expected to have a better interface with engineers.

In the present embodiment, an example in which the min-max-centroid method is used when determining the degree (grade) of the consequent part has been described, but the present invention is not limited to this and the algebraic product-
Addition-centroid methods and the like can also be used. In the classification by the shape of the consequent part, in addition to the simplification method, the functional inference method and the fuzzy variable can be used.
Further, although the example in which the gap shift ΔG and the relative position shift M / P of the projection beams are used as the external signal input to the antecedent part has been described, the external signal is not limited to this, and may be, for example, a process-dependent signal. It is expected that even more accurate alignment will be performed by using the parameters and the like. In the output of the consequent part, it is expected that more accurate alignment can be performed by using a multi-dimensional function in addition to the correction straight line.

Next, a device manufacturing method using an exposure apparatus to which this alignment apparatus is applied will be described. Figure 7
FIG. 4 is a flowchart showing a method for manufacturing a microdevice (semiconductor chip such as IC or LSI, liquid crystal panel, CCD, thin film magnetic head, micromachine, etc.).

First, in step S1, the circuit of a semiconductor device is designed. Next, in step S2,
A mask having the circuit pattern designed in step S1 is manufactured.

On the other hand, in step S3, a wafer is manufactured using a material such as silicon. Next, step S4
In the (pre-process), an actual circuit is formed on the wafer by the lithography technique using the mask and the wafer prepared above. Next, in step S5 (called a post-process), the wafer manufactured in step S4 is used to form semiconductor chips. This step is an assembly process (dicing, bonding),
It includes a process such as a packaging process. Next, step S
In 6, an inspection such as an operation confirmation test and a durability test of the manufactured semiconductor device is performed. Through these steps, the semiconductor device is completed and shipped in step S7.

The wafer process step of FIG. 7 will be described in more detail with reference to FIG.

In step S11, the surface of the wafer is oxidized. In step S12, an insulating film is formed on the wafer surface. In step S13, electrodes are formed on the wafer by vapor deposition. In step S14, ions are implanted in the wafer. In step S15, a photosensitive material is applied to the wafer. In step S16, the circuit pattern of the mask is printed and exposed on the wafer by the exposure apparatus described above. Next, in step S17, the exposed wafer is developed. Next, in step S18, parts other than the developed resist image are scraped off, and finally, step S18.
At 19, the unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to easily manufacture a highly integrated semiconductor device which has been difficult to manufacture in the past.

[0034]

As described above, according to the present invention, the first alignment amount obtained from the barycentric position of the mark position detection light is the gap between the first object and the second object and the first object.
The second alignment amount is obtained by correcting the first alignment amount using the own signal and / or the external signal even if the object and the pick-up beam position are influenced by the variation in the direction perpendicular to the alignment detection direction. , The second alignment amount is used to enable highly accurate alignment.

Further, even in an object whose physical phenomenon is complicated and which is difficult to model, if a certain rule of thumb can be found in the rule base, the alignment accuracy can be improved without making a great improvement in the signal processing program. .

Even when the waveform distortion is significant in the center of gravity detection method, the gap deviation ΔG between the mask and the wafer and the relative positional deviation M / P between the projection beam and the mask.
When it is difficult to independently obtain the contribution rate to the positional deviation (AA error) between the mask and the wafer, the correction amount is calculated by adding both the gap deviation ΔG and the relative positional deviation M / P without separating them. Since it is sought, more accurate alignment can be performed.

Further, the correction covers the entire specification range of the relative displacement between the mask and the wafer, and the dynamic range for measuring the relative displacement between the mask and the wafer with higher accuracy is widened. Can be taken.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an alignment device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing in detail the correction amount calculation processing of FIG.

FIG. 3 is a diagram showing a membership function of FIG. 1.

FIG. 4 is a diagram showing a membership function of FIG. 1.

5 is a diagram showing a fuzzy inference method in FIG. 1. FIG.

FIG. 6 is a diagram showing a configuration of a conventional example.

FIG. 7 is a flowchart showing a method for manufacturing a semiconductor device.

FIG. 8 is a detailed flowchart of the wafer process step of FIG.

[Explanation of symbols]

 1: Center of gravity calculation, 2: Correction amount calculation, 3: Adder.

Claims (12)

[Claims] 1. A mark on a first object and a mark on a second object are irradiated with a light beam, and the respective barycentric positions of mark position detection signal light generated by reflecting or diffracting the light beam on these marks are detected, and these barycentric positions are detected. In the alignment apparatus that determines the alignment amount based on the above, and aligns the first object and the second object,
An alignment apparatus comprising: means for obtaining a correction amount for the alignment amount based on a positional relationship between objects or a positional relationship between the irradiation light flux and the first object. 2. The alignment apparatus according to claim 1, wherein the means for obtaining the correction amount is for obtaining the correction amount by fuzzy inference. 3. The correction amount is 1 of the alignment amount.
It is expressed by the following function, and its gain and offset are determined by the fuzzy inference based on the gap deviation between the first object and the second object and the positional deviation between the irradiation light beam and the mark of the first object. The alignment apparatus according to claim 2, wherein: 4. The first object is a mask and the second object is a mask.
The alignment apparatus according to claim 1, wherein the object is a wafer. 5. An exposure apparatus comprising the alignment apparatus according to any one of claims 1 to 4. 6. A device manufacturing method characterized by manufacturing a device using the exposure apparatus according to claim 5. 7. A mark on a first object and a mark on a second object is irradiated with a light beam, and the barycentric position of a mark position detection signal generated by reflecting or diffracting the light beam on these marks is detected, and these barycentric positions are detected. Based on the alignment amount,
In an alignment method for performing alignment between the first object and the second object, the alignment amount is based on a positional relationship between the first object and the second object or a positional relationship between the irradiation light flux and the first object. An alignment method comprising the step of obtaining a correction amount for 8. The alignment method according to claim 7, wherein the step of obtaining the correction amount includes the step of obtaining the correction amount by fuzzy inference. 9. The correction amount is 1 of the alignment amount.
It is expressed by the following function, and its gain and offset are determined by the fuzzy inference based on the gap shift between the first object and the second object and the positional shift between the irradiation light beam and the mark of the first object. 9. The alignment method according to claim 8, wherein: 10. The method according to claim 7, wherein the first object is a mask and the second object is a wafer.
Alignment method. 11. An exposure apparatus using the alignment method according to claim 7. 12. A device manufacturing method, wherein a device is manufactured using the exposure apparatus according to claim 11.