JP2000260702A - Alignment of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the alignment accuracy when aligning a third layer with a first layer and with a second layer by simultaneously conducting the alignment of the first aligned layer and the third aligned layer and the alignment of the second aligned layer and the third aligned layer. SOLUTION: Based on the coordinate values for the measured deviations in the X direction and in the Y direction between a first layer and a third layer and for the measurement positions, the deviations in the X direction and in the Y direction between the first layer and the third layer are modeled to find out correction parameters. In like manner, based on the coordinate values for the measured deviations in the X direction and in the Y direction between a second layer and the third layer and for the measurement positions, the deviations in the X direction and in the Y direction between the second layer and the third layer are modeled to find out correction parameters. Based on these correction parameters, the deviations in the X direction and in the Y direction between the first and the third layer and the deviations in the X direction and in the Y direction between the first and the third layer are corrected, and then the alignment of the first and the third layer and the alignment of the second and the third layer are simultaneously conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alignment method for aligning a third layer with both a first layer and a second layer when patterning a third layer in a patterning process having three or more layers. In particular, the present invention relates to a semiconductor device alignment method that satisfies both conditions when the directions of alignment of the third layer and the first layer and the alignment direction of the third layer and the second layer are orthogonal.

[0002]

2. Description of the Related Art When patterning three or more layers of a first layer A, a second layer B, and a third layer C on a semiconductor substrate in this order, the third layer C is composed of the first layer A and the second layer B. It may be necessary to align both layers. In such a case, conventionally, for example, first layer A and second layer B are aligned, then first layer A and third layer C are aligned, and second layer B and third layer B are aligned.
For the layer C, there was a method of indirectly controlling the alignment. Alternatively, refer to the document "SPIE96 Metrology, Inspecti
on, and Process Control for Microlithography XISBN
0-81924-2101-4 “Performance of New Overlay Measu
As described in rement Mark "PP.424-435",
When the alignment direction of the first layer A and the third layer C is orthogonal to the alignment direction of the second layer B and the third layer C,
There is a method of measuring the amount of misalignment and performing alignment.

In the former case, the second layer B and the third layer C
Is an indirect alignment, so in order to guarantee misalignment specifications, it was necessary to apply more severe alignment specifications than direct alignment. On the other hand, in the latter case, the amount of misalignment is measured, but only the layer targeted for the amount of misalignment in the X and Y directions is measured. The displacement amount can be measured because it is independent in the X direction and the Y direction. However, since rotation and orthogonality errors cannot be measured, they cannot be corrected.

[0004] The alignment method of the current exposure apparatus, for example, the exposure apparatus such as a batch exposure type, a scanner type for partially exposing, or a one-stroke type such as an electron beam, uses the following parameters to describe the situation of misalignment. It is modeled using.

(A) Average misalignment: offset
X and Y directions. (B) Magnification error (scaling) from center (wafer center or exposure center): misalignment in proportion to distance from center,
At present, the amount of deviation from the center of the wafer is corrected by exposing the exposure position (adding an offset toward the outer peripheral portion of the wafer), and further correcting the deviation from the center within the exposure (field). Since the magnification error may have different values in the X and Y directions, the X and Y directions are respectively corrected. (C) Rotational deviation (the rotation axis is the center of the wafer and the center of the exposure): This also adjusts the exposure position with respect to the rotation of the center of the wafer and corrects the rotation amount within the exposure (field). (D) orthogonality shift.

[0006] With these parameters, in (a) and (b) above, for example, to obtain an offset in the X direction, the amount of misalignment in the Y direction is not necessary, and the X and Y directions are independent. On the other hand, in the above (c) and (d), for example, in order to obtain the amount of rotation, the amount of misalignment in both the X and Y directions is required. Therefore, the rotation amount cannot be obtained by measuring only one direction of a certain layer in the X direction or the Y direction, so that the rotation and the orthogonality cannot be corrected.

[0007] As such a conventional technique, for example, Japanese Patent Application No. 2591746 (Japanese Patent Application No. 62-125133) discloses
The X-direction alignment target formed on the first pattern layer on the substrate is detected by a detector that photoelectrically converts the one-dimensional direction coordinate detection signal light, and the one-dimensional coordinate detection signal output by the detector is one-dimensionally detected. The signal is supplied to the coordinate signal processing means, and the one-dimensional coordinate signal processing means calculates and calculates the amount of displacement in the X direction by a signal processing algorithm, and aligns the third pattern layer with the first pattern layer. And detecting a Y-direction alignment target formed on the second pattern layer formed above or below the first pattern layer with a detector provided separately from the detector. The output one-dimensional coordinate detection signal is supplied to the one-dimensional coordinate signal processing means, and the amount of displacement in the Y direction is calculated by a signal processing algorithm different from the signal processing algorithm. Aligning the third pattern layer with the pattern layer, and moving the stage to a predetermined moving position based on the X-direction data and the Y-direction data obtained by the calculation. Has been described. In such an invention, when the third pattern layer is aligned with the first pattern layer, the amount of displacement only in the X direction is used, and the third pattern layer is aligned with the second pattern layer. Occasionally, since the displacement amount only in the Y direction is used, the same problem as described above occurs.

[0008]

As described above,
In one conventional alignment method for aligning the third layer with both the first layer and the second layer, since the alignment is indirect, it is necessary to employ more severe specifications than the direct alignment. , Alignment was extremely difficult. Further, in other conventional alignment methods, alignment is not performed in consideration of parameters that cause a shift, such as rotation or orthogonality, where the shift amounts in the X and Y directions are not independent of each other. This causes a problem that it is difficult to increase the alignment accuracy.

Accordingly, the present invention has been made in view of the above, and an object of the present invention is to improve the alignment accuracy when aligning a third layer with both a first layer and a second layer. To provide a semiconductor device alignment method.

[0010]

In order to achieve the above object, a first means for solving the problem is to provide a first and a second mating layer formed on a semiconductor substrate with a third mating layer. When aligning the first and third layers, the amounts of displacement of the first and third layers before and after exposure in the X and Y directions are measured, and the second and third layers are aligned with each other. The displacement amounts of the alignment layers in the X direction and the Y direction before exposure are measured, and based on the measured deviation amounts in the X direction and the Y direction of the first and third layers and the coordinate values thereof,
Calculating a correction parameter modeling a shift amount in the X direction and the Y direction between the first mating layer and the third mating layer;
On the basis of the measured shift amounts in the X and Y directions of the second and third mating layers and the coordinate values thereof,
A correction parameter is obtained by modeling the amount of displacement in the X direction and the Y direction between the first layer and the third layer, based on the obtained correction parameters.
Of the second and third layers to be corrected in the X and Y directions, and the first and second layers to be corrected. Third
And the alignment of the second layer and the third layer is performed simultaneously.

The second means is provided for aligning the third layer with the first layer and the second layer to be formed on the semiconductor substrate. The amount of displacement in the X and Y directions of the third mating layer is measured, and the amount of displacement in the X and Y directions of the second and third mating layers is measured. Based on the measured displacements of the first and third layers in the X and Y directions and their coordinate values, the displacements of the first and third layers in the X and Y directions are modeled. The corrected parameters are obtained, and the second layer and the third layer are determined on the basis of the measured shift amounts of the second layer and the third layer in the X and Y directions and their coordinate values. Correction parameters that model the amount of displacement in the X and Y directions of the Therefore, the obtained correction parameters are averaged or weighted for each layer to correct the amounts of displacement in the X and Y directions between the first layer to be bonded and the third layer to be bonded. The shift amounts of the alignment layer and the third alignment layer in the X direction and the Y direction are corrected, and the first alignment layer and the third alignment layer and the second alignment layer and the third alignment layer are corrected. The alignment is performed simultaneously.

[0012] A third means is the first or second means, wherein the amount of deviation between the resist pattern after exposure and the base is measured, and the measured amount of deviation after exposure is replaced with the amount of deviation before exposure. In this manner, correction parameters are similarly obtained, and alignment is similarly performed using the obtained correction parameters.

[0013]

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

According to the present invention, when the first layer, the second layer, and the third layer are patterned in this order, the third layer is aligned with both the first layer and the second layer. In an alignment method in which the direction in which the first layer is desired to be aligned and the direction in which the third layer and the second layer are desired to be orthogonal to each other, as shown in the flowchart of FIG. After the alignment (Step S1), exposure is performed according to the alignment (Step S2) to form a desired pattern. In another embodiment, the amount of misalignment between the exposed resist pattern and the base is measured. (Step S3) The alignment is re-adjusted based on the data on the amount of misalignment of the measurement result, and exposure is performed.

First, in this embodiment, the amount of displacement between the first layer and the third layer in the X and Y directions is measured,
Measuring the amount of displacement between the layer and the third layer in the X and Y directions,
Based on the measured shift amounts of the first and third layers in the X and Y directions and the coordinate values indicating the measurement positions, the shift amounts of the first and third layers in the X and Y directions were modeled. A correction parameter is obtained, and the displacement between the second layer and the third layer in the X direction and the Y direction is determined based on the measured displacement in the X direction and the Y direction of the second layer and the third layer and the coordinate value indicating the measured position. A correction parameter modeling the amount is obtained, and based on the obtained correction parameter, the X direction or the Y direction of the first layer and the third layer is determined.
The amount of deviation in the direction is corrected, and the X direction or Y direction of the second layer and the third layer is corrected.
It is characterized in that the amount of deviation in the direction is corrected and the alignment of the first and third layers and the alignment of the second and third layers are performed simultaneously.

For example, as shown in FIG.
Assuming that the layer B and the third layer C are pattern-formed in this order, the amount of measurement deviation between the third layer C and the first layer A at the j-th position in the i-th chip on the wafer is the same as that at the same position. Of the third layer C
And the measurement deviation amount of the second layer B, respectively: the measurement deviation amount between the layers CA: △ Xc-a (ij), △ Yc-a (ij) The measurement deviation amount between the layers CB: △ Xc-b (ij) , △ Yc-b (ij). The measurement shift amount is obtained by measuring the shift of the base before exposure.

Next, the amount of measurement deviation is calculated as follows: wafer rotation: WR (ca), WR (cb), orthogonality: OR (ca), OR
(cb), X direction scaling: XM (ca), XM (cb),
Y direction scaling: YM (ca), YM (cb), X direction shift: XS (ca), XS (cb), Y direction shift: YS (c−
a), YS (cb) components (factors) are divided into correction parameters. Here, in the wafer rotation, the coordinate system rotates around the origin, and the rotation direction is arbitrary, and usually the counterclockwise direction is the positive direction. The orthogonality is
This shows a state in which the angle between the X direction and the Y direction of the coordinate system is shifted by more than 90 degrees, and the notation method differs depending on whether the reference is the X axis or the Y axis, but here, the X axis is the reference. The scaling is performed in the X direction or Y direction in the X, Y direction coordinate system.
This is the magnification in the direction, and the direction in which it is usually increased is defined as positive. The shift is a parallel shift (offset) from the ideal state of the origin. Normally, the horizontal right direction is positive in the X direction, and the vertical upward direction is positive in the Y direction. Using such correction parameters, the respective measurement deviation amounts are modeled by the following equations.

[0018]

１Xc-a (ij) = XM (ca) ・ Xc-a (ij)-(WR
(ca) + OR (ca)) · Yc−a (ij) + XS (ca) (1) ΔYc−a (ij) = WR (ca) · Xc−a (ij) + YM (ca) · Yc−
a (ij) + YS (ca) (2) ΔXc−b (ij) = XM (cb) · Xc−b (ij) − (WR (cb) + O
R (cb)) · Yc−b (ij) + XS (cb) (3) ΔYc−b (ij) = WR (cb) · Xc−b (ij) + YM (cb) · Yc−
b (ij) + YS (cb) (2) Here, for example, the first layer to be joined is a pattern 1 as shown in FIG. 3, and the second layer to be joined is a pattern as shown in FIG. 2, the third layer to be laid is a pattern 3 as shown in FIG. 5, and the respective patterns 1, 2, and 3 are superimposed and aligned in an arrangement as shown in FIG. In such an alignment, the alignment between the first and third layers is as shown in FIG. 7, and the alignment between the second and third layers is as shown in FIG. In the alignment of the first and third layers,
As shown in FIG. 7, the direction of arrow 4 shown in the figure (Y direction)
However, misalignment becomes severe. On the other hand, in the alignment of the second layer and the third layer, as shown in FIG. 8, the misalignment in the direction of arrow 5 (X direction) shown in the figure becomes severe.

In such a case, the above-mentioned respective correction parameters are obtained by, for example, the least square method or the like, and in the alignment of the first layer and the third layer, the correction parameters are canceled by the measurement deviation amount of the above equation (2). In the alignment between the second layer and the third layer, the amount of measurement deviation of the above equation (3) is corrected so as to cancel out the correction parameter so as to be minimized. It can be performed. When the misalignment in the X direction is severe in the alignment between the first layer and the third layer, the measured misalignment amount of the above equation (1) is similarly corrected to the minimum by using the correction parameter, and the second layer and the third layer are corrected. In the alignment of the layers, if the misalignment in the Y direction is severe, the measured misalignment amount of the above equation (4) may be similarly corrected using the correction parameter so as to be minimized.

In the above embodiment, when the first layer and the second layer need to be aligned in a direction perpendicular to the third layer, the alignment accuracy required for both can be satisfied at the same time. In particular, when the rotation and orthogonality are in the mating layers, the alignment accuracy is further improved.

Next, another embodiment of the present invention will be described.

The feature of this embodiment is shown in FIG.
The result obtained by carrying out step S3 in the flowchart of the above is fed back to the next exposure processing, and after performing alignment and exposure by the alignment method of the above embodiment, the exposure is performed by the overlay measurement device. In the above-described embodiment, the amount of misalignment representing the amount of misalignment between the subsequent resist pattern and the underlying layer is measured for the third layer to the first layer and the third layer to the second layer, and the measured misalignment is replaced by the measured amount of misalignment. A correction parameter is obtained in the same manner as in the above, and the amount of misalignment is corrected and minimized in the same manner as in the above-described embodiment using the obtained correction parameter. If the misalignment between the three layers is measured simultaneously when the misalignment is measured, the measurement time can be processed in the same time as the conventional measurement time between the two layers.

In this embodiment, the effect of the alignment of the above embodiment can be confirmed, and even if a certain offset occurs in the correction parameter, the offset can be corrected.

Next, still another embodiment of the present invention will be described.

The feature of this embodiment is shown in FIG.
In the case of performing the same three-layer alignment as in the above-described embodiment shown in FIG. 8 to FIG. 8, if it is assumed that the pattern 1 of the first layer has a misalignment of the rotation system as shown in FIG. 3 is first aligned with the first layer, that is, the first layer is aligned with the alignment direction of the first and third layers.
A coordinate system is determined so that the relative position of the pattern 3 of the third layer is aligned with the layer, alignment in a specific direction with respect to the second layer in the determined coordinate system is performed, and as shown in FIG. The coordinate system 8 of the third layer is determined with respect to the second coordinate system 7 and the second coordinate system 7 in consideration of the alignment direction, and the alignment is performed in accordance with the coordinate system 8. The correction parameters obtained in Equations (1) to (4) are simply averaged, or the correction parameters are obtained by weighting the third layer and the first layer and between the third layer and the second layer. ing.

In such an embodiment, the first layer,
Alignment with little misalignment can be performed simultaneously on both of the second layers. For example, as shown in FIG. 11, the misalignment between the first layer and the second layer within the specification range is increased, and the specification is deviated accordingly. The misalignment between the first layer and the third layer can be reduced, so that deterioration of the alignment accuracy with respect to a layer other than the specified specific layer can be avoided, and the overall alignment accuracy can be improved. Further, the alignment method according to the embodiment including this embodiment is suitable for a semiconductor device which requires a high integration by adopting a multilayer structure. It should be noted that this embodiment may be combined with the above-described embodiment in which the result obtained by measuring the amount of misalignment after exposure is fed back.

[0027]

As described above, according to the first aspect of the present invention, when the first layer and the second layer need to be aligned in the direction perpendicular to the third layer, the accuracy can be improved in both directions. The required alignment accuracy can be satisfied at the same time, and the alignment accuracy can be further improved especially when the rotation and orthogonality are in the layers to be aligned.

According to the second aspect of the present invention, it is possible to avoid deterioration of alignment accuracy with respect to a layer other than a specific layer on which alignment is performed, and to improve overall alignment accuracy.

According to the third aspect of the invention, the effect of the alignment obtained by the first or second aspect of the invention can be confirmed, and even when a certain offset occurs in the correction parameter, the offset is corrected. be able to.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a process flow when an alignment method for a semiconductor device according to an embodiment of the present invention is performed.

FIG. 2 is a diagram showing the concept of a three-layer structure.

FIG. 3 is a diagram showing an example of a pattern of a first layer.

FIG. 4 is a diagram showing an example of a pattern of a second layer.

FIG. 5 is a diagram showing an example of a pattern of a third layer.

FIG. 6 is a diagram showing a pattern when a first layer, a second layer, and a third layer overlap.

FIG. 7 is a diagram showing a positional relationship between patterns of a first layer and a third layer.

FIG. 8 is a diagram illustrating a positional relationship between patterns of a second layer and a third layer.

FIG. 9 is a diagram showing another pattern when the first layer, the second layer, and the third layer overlap.

FIG. 10 is a diagram showing a coordinate system of a first layer, a second layer, and a third layer.

FIG. 11 is a diagram showing a change in specifications before and after the correction of a shift amount.

[Explanation of symbols]

 A 1st layer B 2nd layer C 3rd layer 1 1st layer pattern 2 2nd layer pattern 3 3rd layer pattern 4 Alignment direction between 1st layer and 2nd layer 5 2nd layer and 3rd layer Alignment direction

Claims (3)

[Claims] When aligning a third mating layer with a first mating layer and a second mating layer formed on a semiconductor substrate, the first mating layer and the third mating layer are aligned. Measuring the amount of displacement of the layers in the X and Y directions before exposure, measuring the amount of displacement of the second and third layers in the X and Y directions before exposure, On the basis of the measured shift amounts in the X direction and the Y direction between the joining layer and the third layer to be joined and their coordinate values, the first
A correction parameter is obtained by modeling the amount of displacement in the X direction and the Y direction between the mating layer and the third mating layer, and measurement in the X direction and the Y direction of the second mating layer and the third mating layer Based on the deviation amount and the coordinate value, the second
A correction parameter modeling the amount of displacement in the X direction and the Y direction between the mating layer and the third mating layer is obtained, and the first mating layer and the third mating layer are determined based on the obtained correction parameters. Is corrected in the X direction and the Y direction, and the shift amount in the X direction and the Y direction between the second layer and the third layer is corrected, and the first layer and the third layer are corrected. A method for aligning a semiconductor device, comprising: simultaneously performing alignment of an alignment layer and a second alignment layer and a third alignment layer. 2. The method according to claim 1, further comprising the steps of: aligning the third layer with the first layer and the second layer formed on the semiconductor substrate; Measuring the amounts of displacement of the layers in the X and Y directions, measuring the amounts of displacement of the second and third layers in the X and Y directions, and comparing the first and third layers with each other Based on the measured shift amounts of the mating layers in the X and Y directions and their coordinate values, a first
A correction parameter is obtained by modeling the amount of displacement in the X direction and the Y direction between the mating layer and the third mating layer, and measurement in the X direction and the Y direction of the second mating layer and the third mating layer Based on the deviation amount and the coordinate value, the second
A correction parameter is obtained by modeling the amounts of shift in the X direction and the Y direction between the mating layer and the third mating layer, and the obtained correction parameters are averaged or weighted for each layer to obtain the first X of the mating layer and the third mating layer
The displacements in the X direction and the Y direction are corrected, and the displacements in the X direction and the Y direction between the second layer and the third layer are corrected. And an alignment method for a semiconductor device, wherein the alignment of the second and third layers is performed simultaneously. 3. A method for measuring a shift amount between a resist pattern after exposure and a base, calculating a correction parameter in the same manner as above, replacing the measured shift amount after exposure with the shift amount before exposure, and similarly using the obtained correction parameter. 3. The alignment method for a semiconductor device according to claim 1, wherein the alignment is performed.