KR102703369B1 - Exposure device, measurement device, and alignment method - Google Patents

Abstract

In a projection exposure device, a mask pattern is precisely transferred onto a substrate while improving throughput. The positions of alignment marks of chips arranged in a matrix on a substrate (W) are measured in advance by a measuring device (15) independent of a projection exposure device (10), and the unique positional deviation amount unique to each chip is obtained. Then, the projection exposure device (10) measures the alignment mark for GA and calculates the positional deviation amount of each chip with linearity. Then, based on the unique positional deviation amount and the linear positional deviation amount, the positions of the alignment marks of each chip are calculated in a situation where the substrate (W) is mounted on the exposure device (10), and alignment exposure is performed.

Description

{EXPOSURE DEVICE, MEASUREMENT DEVICE, AND ALIGNMENT METHOD}

The present invention relates to an exposure device for forming a pattern on a substrate, and more particularly, to alignment (positioning) for a substrate.

In exposure equipment, high-precision alignment is required along with pattern miniaturization. Therefore, alignment marks formed on the substrate are not only marks installed at the four corners of the substrate to measure deformation of the entire substrate, but also alignment marks are formed to match the exposure area of one shot.

Detecting the positions of a large number of alignment marks installed on a substrate in this way requires a large amount of time, which reduces throughput. Therefore, a configuration is known in which a measuring device is provided that measures the positions of alignment marks independently of an exposure device (see Patent Document 1).

There, prior to alignment adjustment by the exposure device main body, the position of the alignment mark in a predetermined exposure area is detected by the measuring device. Then, in the exposure device, only the position of the alignment mark related to the entire substrate is detected by the GA method or the like, and alignment is performed using the position information of the alignment mark detected in advance.

Japanese Patent Publication No. 10-64804

For example, in the case of a FO-WLP (fan-out wafer level package) substrate that mounts silicon chips on a carrier, random chip arrangement errors occur due to chip mounting precision. Meanwhile, expansion and deformation of the substrate occur with each process, and the degree of expansion and deformation is different.

For this reason, the position of the alignment mark measured before the exposure device may be different when the alignment is measured by the subsequent exposure device, resulting in a positioning error during alignment of the exposure process. In particular, in a process that repeats the exposure process of transferring the pattern by overlapping it in multiple layers, the positioning error becomes significant.

Therefore, when measuring the position of an alignment mark prior to alignment by an exposure device, it is required to be able to realize high-precision alignment.

The exposure apparatus of the present invention is an exposure apparatus capable of exposing a plurality of chips on a substrate and communicating with an independent measuring apparatus that measures positional information of alignment marks formed for each chip, and has a measuring unit that measures the position of an alignment mark for GA (global alignment) installed on the substrate. Then, alignment is performed based on the unique positional deviation amount of each chip obtained from the alignment mark positional information of each chip and the positional information of the alignment mark for GA measured by the measuring unit. Here, the unique positional deviation amount does not mean an error that has linearity such as deformation or expansion of the entire substrate and can be considered common between chips, but indicates an error component unique to each chip.

With regard to alignment, it is possible to obtain a unique positional deviation amount in an exposure device, and the exposure device may be provided with a calculation unit that obtains a die shift amount obtained by excluding a deformation amount related to the entire substrate from alignment mark position information of each chip as the unique positional deviation amount. For example, the calculation unit obtains the die shift amount by excluding a deformation amount of a linear component from alignment mark position information.

Meanwhile, it is also possible to obtain the unique position deviation amount from an independent measuring device. Another aspect of the present invention, a measuring device, comprises an alignment mark measuring unit that measures the position information of alignment marks formed on each chip, obtains the unique position deviation amount of each chip obtained from the alignment mark position information of each chip, and transmits the data of the unique position deviation amount to an exposure device.

In another aspect of the present invention, an alignment method comprises: measuring the alignment mark positions of each chip installed on a substrate having a plurality of chips arranged two-dimensionally by a measuring device independent of an exposure device that measures the positions of alignment marks; measuring the positions of alignment marks for GA (global alignment) installed on the substrate by a measuring unit installed in the exposure device; and performing alignment based on a unique positional deviation amount of each chip obtained from alignment mark position information of each chip by the measuring device or the exposure device and the positional information of the alignment mark for GA measured by the measuring unit.

According to the present invention, in a projection exposure device, a mask pattern can be precisely transferred onto a substrate while improving throughput.

[Figure 1] This is a schematic block diagram of a projection exposure device according to the present embodiment.
[Figure 2] This is a drawing showing a short array formed on a substrate (W).
[Figure 3] This is a diagram showing the short array error divided into components.
[Figure 4] This is a drawing showing a flow chart of chip-specific arrangement error calculation processing executed in a measuring device (15).
[Figure 5] This is a drawing showing an exposure process including alignment performed in a projection exposure device (10).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic block diagram of a projection exposure device according to the present embodiment. Here, an exposure process is performed to repeatedly form a pattern in multiple layers.

A projection exposure device (10) is an exposure device that transfers a mask pattern formed on a reticle (R) as a photomask to a substrate (work substrate) (W) according to a step & repeat method, and is equipped with a light source (20) such as a discharge lamp and a projection optical system (34). The reticle (R) is made of quartz material or the like, and a mask pattern having a light-shielding area is formed. Here, a substrate (e.g., an interposer substrate) made of silicon, ceramics, glass or resin is applied as the substrate (W).

The illumination light emitted from the light source (20) enters the integrator (24) through the mirror (22), and the amount of illumination light becomes uniform. The uniform illumination light enters the collimator lens (28) through the mirror (26). Accordingly, parallel light enters the reticle (R). The light source (20) is controlled by the lamp driving unit (21).

The reticle (R) is mounted on a reticle stage (30) so that the mask pattern becomes the light source-side focal position of the projection optical system (34). The stage (30) mounting the reticle (R) and the stage (40) mounting the substrate (W) have three-axis coordinate systems of X-Y-Z orthogonal to each other defined. The stage (30) is movable in the X-Y direction to move the reticle (R) along the focal plane, and is driven by a stage drive unit (32). In addition, the stage (30) is also rotatable in the X-Y coordinate plane. The position coordinates of the stage (30) are measured here by a laser interferometer or a linear encoder (not shown).

Light passing through the area where the mask pattern of the reticle (R) is formed is projected as pattern light onto the substrate (W) by the projection optical system (34). The substrate (W) is mounted on a substrate stage (40) so that its exposure surface matches the image-side focus position of the projection optical system (34).

The stage (40) is movable in the X-Y direction to move the substrate (W) along the focal plane, and is driven by the stage driving unit (42). In addition, the stage (40) is movable in the Z-axis direction (optical axis direction of the projection optical system (34)) perpendicular to the focal plane (X-Y direction), and furthermore, is rotatable in the X-Y coordinate plane. The position coordinates of the stage (40) are measured by a laser interferometer or linear encoder (not shown).

The control unit (50) controls the stage driving unit (32, 42) to determine the positions of the reticle (R) and the substrate (W), and at the same time, controls the lamp driving unit (21). Then, an exposure operation based on the step & repeat method is executed. A memory (not shown) installed in the control unit (50) stores the mask pattern position coordinates of the reticle (R), the design position coordinates of the shot area formed on the substrate (W), the step movement amount, and the like.

The alignment mark imaging unit (36) is a camera or microscope that captures an alignment mark formed on a substrate (W), and captures an alignment mark installed on the substrate (W) by driving the stage driving unit (42) to move the stage (40) before exposure. The image processing unit (38) detects the position coordinates of the alignment mark based on the image signal sent from the alignment mark imaging unit (36). Here, the positions of alignment marks for GA (global alignment) installed at the four corners of the substrate (W) are detected.

The control unit (50) sequentially transfers the mask pattern of the reticle (R) to each shot area formed on the substrate (W) according to the step & repeat method. That is, the control unit (50) intermittently moves the stage (40) according to the shot area interval, and when the shot area to be exposed is positioned at the projection position of the mask pattern, the control unit (50) drives the light source (20) to project pattern light onto the shot area.

The measuring device (15) is a device for measuring an alignment mark installed on a substrate (W), and is equipped with an alignment mark measuring section (15A) and is connected to the projection exposure device (10) so as to enable mutual data communication. The substrate (W) is configured as a FO-WLP substrate here, and a large number (for example, 10,000) of silicon chips are arranged in a matrix shape on a carrier substrate. In addition, the substrate is not limited to a FO-WLP substrate, and may be a general wafer substrate or a printed wiring board, etc. The chips do not have to be of the same type, and a plurality of types of chips may be arranged. In addition, it may be a substrate in which a large number of circuit patterns (called units) of a small area compared to the substrate are arranged in a matrix shape, and alignment may be performed based on the units and exposure may be performed. There may be one or more chips inside the unit. The measuring device (15) measures the position of the alignment mark installed on each chip at a stage prior to patterning by the projection exposure device (10).

The measuring device (15) comprises a substrate stage for placing a substrate (W), a camera for capturing an alignment mark, a scanning mechanism for moving the substrate relative to the camera, a measuring unit for measuring the amount of relative movement of the substrate, an image processing unit for measuring the position of the alignment mark from an image obtained by capturing with the camera, a data management unit for recording position information of the measured alignment mark as a file, and a controller for controlling these (not all shown here).

The measuring device (15) transmits a file regarding the position information of the alignment mark of each chip to the data server (60). The data server (60) records and manages the file in relation to the ID of the substrate (W) that is the subject of measurement.

The projection exposure device (10) performs alignment when transferring (exposing) a mask pattern for each layer. That is, it detects a positioning error, which is an arrangement error of the shot area, and performs positioning alignment between the shot area of the substrate (W) and the projection area of the mask pattern in advance.

In this embodiment, the projection exposure device (10) calculates a positional deviation amount unique to each chip from the position of the alignment mark of each chip measured by the measuring device (15), and, using this positional deviation amount and the position of the alignment mark for GA measured by the alignment mark imaging unit (36), obtains the exposure position of each chip during the exposure process. The projection exposure device (10) performs alignment exposure according to the die-by-die (hereinafter, D/D) method according to the obtained exposure position of each chip. This will be described in detail below.

Fig. 2 is a drawing illustrating a shot array formed on a substrate (W). Fig. 3 is a drawing illustrating distortion of a shot array caused by deformation of the substrate (W), etc.

As illustrated in Fig. 2, a lower pattern is formed on the substrate (W) in which chips (CP) are arranged in a matrix shape at regular intervals according to a grid defined by an X-Y coordinate system. Here, each chip (CP) corresponds to a shot area, and a mask pattern formed on a reticle (R) is formed by overlapping it on the chip (CP) (hereinafter also referred to as a shot area). In addition, an alignment mark (AM) for position alignment is formed at an arbitrary position (the center position of the left and right ends in Fig. 2) according to the arrangement of the shot area (CP). The alignment mark (AM) for position alignment may be installed at a position near the shot area (CP) (for example, on a scribe line). In addition, a part of the alignment mark (AM) for position alignment may also be used as an alignment mark for GA.

Fig. 3 shows a state where the line of the short region (CP) is collapsing due to deformation of the substrate (W). If the substrate (W) is a wafer, the deformation amount is not that large, but it becomes a size that cannot be ignored when compared to the allowable error range in polymerization with the lower layer pattern. In addition, if the substrate (W) is a printed circuit board or an interposer board, the deformation of the substrate (W) becomes even larger. Therefore, the position of each chip (CP) deviates from the design position.

In the case of the substrate (W) being a FO-WLP substrate, a random chip arrangement error (called a die shift) occurs due to chip mount precision. Meanwhile, the substrate (W) undergoes stretching and deformation (collectively called substrate deformation) each time it goes through a process. Therefore, the position of the alignment mark (AM) of each chip (CP) at the time of exposure is different from the position of the alignment mark (AM) when measured by the measuring device (15).

In particular, when patterning is performed on multiple layers, each time exposure and the processes before and after (exposure, etching, heat treatment, etc.) are repeated, the degree of elasticity and deformation of the substrate (W) changes, and the positional deviation from the alignment mark (AM) measured by the measuring device (15) increases.

Fig. 3 is a diagram illustrating the shot alignment error divided into components. The chip alignment error component due to the die shift (defined as the die shift amount) has no correlation or regularity with the error amount between chips (CP). This alignment error without correlation or regularity is defined as an inherent positional deviation amount. The inherent positional deviation amount can be regarded as a nonlinear error component that has no linearity (nonlinearity) regardless of the deformation or expansion of the entire substrate (W). On the other hand, the chip alignment error component due to the deformation or expansion of the substrate (W) can be regarded as a linear error component because it is an alignment error that occurs with a common regularity between chips (CP) depending on the degree of deformation of the entire substrate (W).

Therefore, among the chip arrangement errors between the positions of the alignment marks (AM) of each chip (CP) measured by the measuring device (15) and the design positions, the linear arrangement error amount is excluded and the unique positional deviation amount of each chip is extracted. Then, in the projection exposure device (10), the linear chip arrangement error amount obtained from the alignment mark for GA is obtained and the unique positional deviation amount of each chip is combined to estimate the exposure position of each chip during the exposure process.

Fig. 4 is a drawing illustrating a flow chart of chip-specific arrangement error calculation processing executed in a measuring device (15).

When the positions of alignment marks installed on each chip of the substrate (W) are measured (S101), the difference (X, Y, θ) between the positional information of the alignment marks on each chip and the positional information in the design is calculated (S102). Then, from the obtained chip arrangement error amount, a linear component is extracted using the least squares method or the like (S103), and by removing it, the X, Y, and θ components, which are the unique positional deviation amounts of each chip, are obtained (S104).

Fig. 5 is a drawing illustrating an exposure process including alignment performed in a projection exposure device (10).

The positions of alignment marks for GA installed on the substrate (W) (for example, the positions of alignment marks installed at the four corners of the substrate) are measured, and the difference from the designed position is calculated by dividing it into X component, Y component, and θ component (S201). Meanwhile, data on the unique positional deviation amount of each chip obtained by the measuring device (15) is read out from the data server (60) (S202).

Since the positional deviation of the alignment mark for GA measured by the projection exposure device (10) can be regarded as a linear positional deviation (i.e., the sum of the deviations of X, Y, and θ when the substrate is placed in the exposure device, or the deformation such as substrate elongation or change in orthogonality), the deformation of the entire substrate (W) in the exposure process can be calculated from this. Then, according to the GA alignment technique, the positional deviation of the X, Y, and θ components at the exposure position of each chip obtained from the deformation of the entire substrate (W) can be calculated (the positional deviation at the exposure position of each chip obtained from the deformation of the entire substrate (W) is defined as the linear positional deviation). However, it is assumed that the deformation and elongation of the substrate (W) occur almost uniformly over the entire substrate or with respect to the exposure target area.

And, based on the linear position deviation amount and the unique position deviation amount of each chip, the exposure position of each chip is calculated (S203). That is, by adding the linear position deviation amount and the unique position deviation amount to the exposure position in the design, the exposure position (exposure map) of each chip during the exposure process is calculated. In the projection exposure device (10), the alignment mark of each chip is not measured, but the exposure position of each chip is estimated by this operation, and exposure is performed using the die-by-die method (S204).

In this way, according to the present embodiment, the positions of alignment marks of chips arranged in a matrix on a substrate (W) are measured in advance by a measuring device (15) independent of the projection exposure device (10), and the unique positional deviation amount unique to each chip is obtained. Then, the projection exposure device (10) measures the alignment mark for GA, and calculates the positional deviation amount of each chip with linearity. Then, based on the unique positional deviation amount and the linear positional deviation amount, the exposure position of each chip is calculated and exposure is performed in a situation where the substrate (W) is mounted on the projection exposure device (10).

In this way, by calculating the positional deviation amount with linearity that changes along with the process during the exposure process, and calculating the unique positional deviation amount that occurs during the initial chip mounting and does not change through the process before using the exposure device, proper alignment can be performed. In particular, proper alignment can be performed even when a repeating pattern is superimposed on the substrate (W). This can also be applied to a substrate in which elements other than chips are arranged in two dimensions.

Instead of the measuring device (15) calculating the positional deviation amount unique to the chip and outputting it to the projection exposure device (10), the data server (60) or the projection exposure device (10) may calculate the positional deviation amount unique to the chip. In addition, the alignment mark for GA is not limited to being formed at a specific location on the substrate (W), and a linear positional deviation amount may be calculated by selecting a predetermined alignment mark. In addition, it is also possible to apply it to a maskless exposure device instead of a projection exposure device. In this case, the exposure data may be corrected based on the position of the unique positional deviation amount of each chip that has been calculated.

In addition, when exposing a given layer of the substrate (W), the measuring device (15) may calculate the positional deviation amount unique to the chip and output it to the projection exposure device (10), and when exposing a layer higher than that layer, alignment may be performed using the already calculated positional deviation amount unique to the chip.

10: Projection exposure device
40: Stage
42: Stage drive unit
50: Control Unit
W: substrate
AM: Alignment Mark
R: Reticle

Claims (5)

An exposure device capable of exposing a plurality of chips arranged in a matrix form on a substrate, capable of aligning the chips to the substrate, and capable of communicating with an independent measuring device that measures positional information of alignment marks formed on each chip,
A measuring unit that measures the position of an alignment mark for GA (global alignment) installed on a substrate in which multiple chips are arranged in a matrix form when the substrate is mounted on a stage during an exposure process;
An operation unit for obtaining the die shift amount of each chip by removing the amount of linear component deformation related to the entire substrate from the difference between the exposure position of each chip in the above substrate design and the alignment mark position information of each chip of the substrate measured by the above measuring device, and
A calculation means for calculating the exposure position of each chip during the exposure process by adding the die shift amount and the linear position deviation amount obtained from the position information of the alignment mark for GA measured by the measuring unit during the exposure process to the exposure position of each chip in the design.
An exposure device characterized by comprising: The alignment mark position of each chip is measured by a measuring device independent of the exposure device, which is installed on a substrate in which multiple chips are arranged in a matrix form.
By the measuring unit installed in the above exposure device, the position of the alignment mark for GA (global alignment) installed on the substrate is measured when the substrate is mounted on the stage during the exposure process.
An alignment method characterized in that the amount of deformation of a linear component related to the entire substrate is removed from the difference between the exposure position of each chip in the substrate design and the alignment mark position information of each chip of the substrate measured by the measuring device by the measuring device, by the measuring device or the exposure device, thereby obtaining the amount of die shift of each chip, and then calculating the exposure position of each chip in the exposure process by adding the die shift amount and the linear position deviation amount obtained from the position information of the alignment mark for GA measured by the measuring unit during the exposure process to the exposure position of each chip in the design, and aligning. delete delete delete

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