JPH08274017A - Exposing method and device - Google Patents

Abstract

PURPOSE: To output the exposure pattern alignment or exposure pattern alignment precision as a history by a method wherein a substrate alignment is made according to the alignment mark in one lower layer in a pair relation defined by a previously specified alignment tree. CONSTITUTION: In order to form plural layers on a semiconductor wafer 10 using photolithography, an alignment tree previously defining the procedures of exposure pattern alignment is used. In order to make alignment for exposure pattern of upper layers, specific layers in a pair relation connected by hyphen in this alignment tree are selected as objective layers. The exposure pattern alignment slippage data on the whole combination with different layers besides the alignment tree, distance in design and others are stored in the memory part 34. Accordingly, the decline in throughput can be avoided while improving the positional precision in exposure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and exposure apparatus used in a plurality of lithography processes, and in particular,
The present invention relates to alignment of exposure patterns of upper and lower layers when exposing each of a plurality of layers.

[0002]

2. Description of the Related Art For example, in a semiconductor manufacturing process, a plurality of photolithography processes are performed to form a plurality of layers on a substrate. In each exposure step in this photolithography step, it is necessary to accurately align the exposure pattern of each layer.

For this reason, conventionally, alignment marks have been formed on the respective layers formed on the substrate to be processed. The alignment mark is formed through an exposure process and a phenomenon process for each layer formed on the substrate to be processed.

For example, when exposing the third layer,
Alignment marks are already formed on the first layer and the second layer, which are the lower layers. Therefore, in the exposure step of the third layer, the alignment of the exposure pattern for the third layer is performed with reference to the alignment marks of the first layer or the second layer. This first layer or second
Which of the layer alignment marks is used is determined in advance by the alignment tree. 8 and 9 show an example of this alignment tree.

FIG. 8 shows a series-shaped alignment tree for aligning the upper layer with the alignment mark of the layer immediately below when exposing the upper layer. For example, the third
In the layer exposure process, the alignment mark of the second layer is used as a reference.

Here, in the case where the alignment tree of FIG. 8 is adopted and the positional shift amounts in the X and Y directions between the respective layers are made equal to each other, a between the first layer and the third layer is obtained. The average amount of positional deviation in the X and Y directions is (a ² +
a ² ) ^1/2 . The positional shift between the first layer and the fourth layer is
(A ² + a ² + a ² ) ^1/2 . As described above, when the alignment tree of FIG. 8 is adopted, the positional deviation of each layer with respect to the first layer cumulatively increases.

Alternatively, the alignment tree shown in FIG. 9 may be adopted. According to the figure, when the fourth layer is exposed, the alignment mark of the second layer is used as a reference. Therefore, the positional deviation between the second layer and the fourth layer can be maintained at a, and the positional deviation between the first layer and the fourth layer can be (a
² + a ² ) ^1/2 can be reduced.

However, the maximum positional deviation between the first layer and the fifth layer is (a ² + a ² + a ² ) ^1/2 , and although the positional deviation amount is smaller than that in FIG. 8, the layers are separated from each other. The problem that the amount of misalignment increases to such an extent could not be solved.

On the other hand, the exposure position aligning methods described in Japanese Patent Laid-Open Nos. 1-282816 and 3-151626 are known.

In these methods, when exposing the uppermost layer formed on the substrate to be processed, all alignment marks in the lower layer are optically measured, and alignment is performed with reference to the plurality of alignment marks. Is.

For example, while the fourth layer is exposed, the alignment marks of the first layer, the second layer, and the third layer are used as alignment references. Further, according to the latter publication,
When a plurality of alignment marks are used as a reference, a layer having a particularly strong correlation is weighted to further improve the alignment accuracy.

However, according to the above-mentioned two methods, in order to expose a certain layer, all alignment marks existing in the layer under the exposed layer must be optically measured, and the alignment of the plurality of layers is performed. Optical measurements of the marks had to be repeated after each exposure of each layer. Therefore, there has been a problem that the throughput in the exposure process is reduced.

Therefore, the object of the present invention is to measure only one lower layer alignment mark having a pair relationship defined by the alignment tree in each exposure step, and It is an object of the present invention to provide an exposure method and an exposure apparatus capable of accurately performing exposure pattern alignment while taking account of exposure pattern alignment deviations from other layers that are not present.

Another object of the present invention is to provide an exposure method and an exposure apparatus capable of outputting the exposure pattern alignment between layers or the exposure pattern alignment accuracy as a history.

[0015]

According to a first aspect of the present invention, a plurality of layers are formed on a substrate by using an exposure process, and alignment marks are formed on each of the layers to form a second layer. In each of the subsequent exposure steps of the layer, in the exposure method for performing alignment of the substrate, based on the alignment marks of one lower layer that has a pair relationship defined in a predetermined alignment tree, the alignment tree A step of measuring and storing position information between the specific layers from each of the alignment marks of the specific layers having a pair relationship defined in, and position information between layers other than the specific layers are stored. Calculating and storing based on the position information between the specific layers.

According to the first aspect of the invention, it is possible to store the positional information between different layers based on the alignment marks formed on the respective layers. For example, in the case of the alignment tree shown in FIG. 4, the specific layers (first layer-second layer, second layer-) having a pair relationship defined in this tree.
Position information between the specific layers is measured and stored from the alignment marks of the third layer, the second layer-the fourth layer, and the fourth layer-the fifth layer). On the other hand, layers that do not have a pair relationship defined in the alignment tree (for example, the first layer-third layer,
The position information of the third layer to the fourth layer) is obtained by calculation based on the stored position information between the specific layers described above, and this is also stored in the same manner.

As described above, since the position information between all different layers can be stored, these information can be output as a history after the photolithography process of each layer is completed. Alternatively, as will be described later, it is possible to perform alignment for exposure in consideration of positional information between layers that are not in a pair relationship defined in the alignment tree,
More accurate positioning can be performed.

When the alignment marks are formed at a plurality of locations on each layer as described in claim 2, positional information between different layers is stored at a plurality of locations. Further, based on these stored information, as shown in claim 3, overlay accuracy information of different layers can be calculated and obtained.

According to a fourth aspect of the present invention, first to Nth layers (N is a natural number of 3 or more) are formed on the substrate using an exposure process, and the first to Nth layers are aligned with each other. In the exposure step of forming a mark and each layer after the second layer, based on the alignment mark of one layer of the lower layer which has a pair relationship defined in a predetermined alignment tree,
In the exposure method for aligning the substrate, a step of measuring and storing positional information between the specific layers from the alignment marks of each of the specific layers having a pair relationship defined in the alignment tree; Position information between layers other than layers, a step of calculating and storing based on the stored position information between the specific layers,
The exposure step of the third and subsequent layers, a first step of calculating alignment information of the substrate based on the alignment marks of one lower layer having a pair relationship defined in the alignment tree; A second step of calculating and obtaining position information between one or a plurality of lower layers that are not in the pair relationship defined in the alignment tree based on the stored position information and the alignment information;
And a third step of determining whether or not the alignment information is appropriate based on the position information obtained in the second step.

According to the invention of claim 4, based on the stored information shown in claim 1, the exposure process of the third and subsequent layers can be performed with higher accuracy. For example, when the alignment tree shown in FIG. 4 is used and the fourth layer is exposed, first, based on the alignment marks of the second layer having the pair relationship defined in the alignment tree, the processed object is processed. Substrate alignment information is calculated. Next, when it is desired to perform the exposure of the fourth layer also in consideration of the positional relationship with the third layer, the third layer and the fourth layer which are not in the pair relationship defined in the alignment tree are exposed. The position information of is calculated by calculation based on the above-mentioned stored information. Then, it is determined whether or not the alignment position of the substrate calculated based on the second alignment mark does not largely deviate from the exposure pattern of the third layer.

The exposure method defined in claim 4 can be suitably implemented using the exposure apparatus according to claim 8.

Further, as described in claim 5, for example, when the positional deviation allowable position between the third layer and the fourth layer is stored in advance, the fourth position calculated based on the alignment mark of the second layer. It is determined whether or not the position of the exposure pattern of the layer satisfies the positional deviation tolerance with respect to the third layer.

If the allowable value is not satisfied, the alignment position of the substrate to be processed can be corrected in a direction that satisfies the allowable value. This method can be suitably implemented by the exposure apparatus defined in claim 9.

Further, as described in claim 7, it is preferable to judge again whether or not the corrected alignment position satisfies the above-mentioned allowable value.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment to which the present invention is applied will be described.
This will be described with reference to the drawings.

FIG. 1 shows an example of an exposure apparatus to which the present invention is applied. In the figure, a substrate to be processed, for example, a semiconductor wafer 10 has two-dimensional directions of X and Y
It is supported by a wafer stage 12 which is rotatable around a Z axis which is orthogonal to the axis. An exposure source such as an excimer laser source 14 is arranged above the wafer stage 12. A reticle 16 and a projection lens 18 are arranged between the excimer laser source 14 and the semiconductor wafer 10. The exposure pattern formed on the reticle 16 is reduced and projected to, for example, ⅕ by passing through the projection lens 18 to form an image on the semiconductor wafer 10. Wafer stage 1
By driving 2 in a stepwise manner, it becomes possible to project the exposure pattern of the reticle 16 into each chip formed in large numbers on the semiconductor wafer 10.

On this semiconductor wafer 10, as shown in FIG. 2, alignment marks are formed at a plurality of positions on the periphery, for example, at each of 8 positions A to H. The alignment mark is formed for each layer formed on the semiconductor wafer 10 through a plurality of photolithography steps.

An example of this alignment mark is shown in FIG. As shown in FIG. 3A, a lower layer alignment mark 50 and an upper layer alignment mark 52 are formed in parallel with each other with a design value upper distance L1. In the same figure (A),
Each of the alignment marks 50 and 52 is formed of, for example, seven dots arranged at equal intervals along the Y direction, and each of the alignment marks 50 and 52 is arranged at a distance L1 in the X direction.

These two rows of alignment marks 50, 52
The output waveform shown in FIG. 3B can be obtained by irradiating the scanning beam 54 that is scanned in the X direction and receiving the reflected light, for example. Thereby, the distance L2 between the two peak points of this output waveform is measured. Therefore, the exposure pattern misalignment of the upper and lower layers in the X direction Δ
X is obtained from the following equation (1). ΔX = L1-L2 (1) Similarly, the alignment marks 50 and 52 of the upper and lower layers are formed.
Are arranged in the Y direction with a distance L1 therebetween, and these are measured in the same manner as described above, whereby the exposure pattern alignment deviation in the Y direction can be measured.

The detection of the exposure pattern misalignment of these upper and lower layers in the X and Y directions is carried out in 8 of the semiconductor wafer 10 shown in FIG.
This is performed for each of the points A to H. The amount of misalignment of the exposure pattern in each direction may be detected by image processing without using scan light, for example, after the images of both marks 50 and 52 are formed on the CCD, the amount of misalignment of both marks is detected by image processing. it can.

When a plurality of layers are formed on the semiconductor wafer 10 by the photolithography process, an alignment tree which defines a procedure for aligning an exposure pattern in advance is used. An example of this alignment tree is shown in FIG. In FIG. 4, when the alignment for the exposure pattern of the upper layer is performed, only the specific layers having a pair of hyphens in this alignment tree are targeted. For example, to expose the fourth layer, the exposure pattern is aligned with the second layer.

In this embodiment, the optical measurement of the exposure pattern alignment shift between the upper and lower layers shown in FIG.
This is done only for specific layers that have a pair relationship defined by the alignment tree shown in. That is,
The exposure pattern misalignment of each of the first layer-second layer, the second layer-third layer, the second layer-fourth layer, and the fourth layer-fifth layer is obtained by measurement. Pattern misalignment between layers that do not form a pair in this alignment tree, for example, the first layer-third layer, is calculated and obtained based on the information obtained by the above-described measurement.

Each configuration of the block diagram shown in FIG. 1 is for measuring and calculating the exposure pattern alignment deviation information and controlling the drive of the wafer stage 12 based on the measurement and calculation. In FIG. 1, TTL (Through The
A Lenss type alignment optical system 20 is provided, and a control unit 30 that controls the alignment operation based on the data collected via the alignment optical system 20 is provided.

The alignment optical system 20 has a half mirror 22 provided between the excimer laser source 14 and the reticle 16, and a measuring section 32 for measuring reflected light incident through the half mirror 22. When the alignment optical system 20 detects the upper and lower alignment marks 50 and 52 shown in FIG. 3, the alignment optical system 20 emits the light from the excimer laser source 14 and reflects the alignment marks 50 and 52 in the upper and lower layers on the semiconductor wafer 10. The light enters the measurement unit 32 via the half mirror 22. The measuring unit 32 measures the actual distance L2 between the alignment marks 50 and 52 based on the optical waveform shown in FIG.

The upper and lower alignment marks 50, 5
The detection of 2 is not necessarily limited to the exposure wavelength, and other light may be used. In this case, for example, the measurement unit 32 is provided with, for example, a helium-neon laser source, and light emission and light reception are performed by the measurement unit
It can also be done in 2. In addition, the upper and lower alignment marks 50 and 52 can be detected by an overlay deviation measuring device other than the exposure device.

A storage unit 34 and a calculation unit 36 are further connected to the control unit 30. The calculation unit 36 includes the measurement unit 32.
Based on the information input via, all the calculations for calculating the alignment position including the exposure pattern alignment deviation information of different layers are performed. In addition to the alignment tree shown in FIG. 4 and the designed distance L1 shown in FIG. 3A, the storage unit 34 stores exposure pattern alignment deviation information for all combinations of different layers. Among the exposure pattern alignment deviation information, the exposure pattern alignment deviation information in the X and Y directions of point A on the semiconductor wafer 10 shown in FIG. 2 is shown in Table 1 below.

[0037]

[Table 1]

In Table 1, specific layers having a pair relationship defined in the alignment tree shown in FIG. 4, that is, first layer-second layer, second layer-third layer, second layer-fourth layer
The numerical values of the exposure pattern alignment deviations in the X and Y directions between the first layer and the fourth layer to the fifth layer are as described above.
It is created based on the information measured through 0. Numerical values of the exposure pattern misalignment between layers other than this are all calculated.

In the storage unit 34, not only the exposure pattern alignment deviation information about the measurement point A shown in Table 1 but also the exposure pattern alignment deviation information about each of the other points B to H on the semiconductor wafer 10 shown in FIG. Remembered.

Further, the storage unit 34 can also store an exposure pattern alignment accuracy table shown in Table 2 below.

[0041]

[Table 2]

Table 2 shows the semiconductor wafer 10 shown in FIG.
For the measurement points A to H, the average value and standard deviation σ for each layer are calculated, and the average value + 3σ is used as the overlay accuracy. The data shown in Table 2 is effectively used as history information about the semiconductor wafer 10 after all the photolithography processes are completed.

To this end, the output section 42 is connected to the control section 30. The history information shown in Table 1 or Table 2 is displayed or printed out through the output unit 42.

The control unit 30 is further connected to the determination unit 38. The determination unit 38 determines that the alignment information created based on the alignment information between the layers having the pair relationship defined by the alignment tree shown in FIG. It is to determine whether or not the allowable value set by the above is satisfied. For example, it is determined whether or not the alignment information of the exposure pattern regarding the fourth layer obtained based on the alignment marks of the second layer in FIG. 4 satisfies a preset tolerance value between the third layer and the fourth layer. To be done. When the allowable value is not satisfied, the control unit 30 causes the calculating unit 36 to calculate the alignment information again, and then preferably the determining unit 38 again compares the alignment information with the allowable value. The allowable value is stored in the storage unit 34 in advance.

The alignment information thus obtained is output to the drive control unit 40 via the control unit 30, and the drive control unit 40 drives and controls the wafer stage 12 based on the alignment information. , The optimum position setting for exposure will be performed.

Next, a procedure for forming a MOS transistor by using the photolithography process a plurality of times using the exposure apparatus of FIG. 1 will be described with reference to FIG.

First Layer Photolithography Step This first layer photolithography step is used to form an N well region 62 and a P well region (not shown) on the silicon substrate 60. An oxide film and a nitride film, for example, are sequentially formed on the substrate 60 to form the N well region 62, and the exposure apparatus shown in FIG. 1 is used to remove a part of the nitride film corresponding to the N well region 62. The exposure process using is performed. After the photolithography process including the exposure process is completed, boron ions are implanted into a region corresponding to the N well region 62, so that N
The well region 62 will be formed.

Second Layer Photolithography Step This second photolithography is used for element isolation. Therefore, after the oxide film and the nitride film are removed from the substrate 60, the pad oxide film 6 is formed on the substrate 60.
4 and a nitride film (not shown) are formed. In order to remove the nitride film in the region corresponding to the N-type stopper region 66, as shown in FIG.
An exposure process using the exposure apparatus shown in is performed. The N-type stopper region 66 is formed by performing phosphorus ion implantation through the mask made of the nitride film obtained by the second layer photolithography process including the exposure process.

After that, by locally oxidizing the pad oxide film 64, LOCOS 6 as an element isolation film is formed.
8 are formed.

Third Layer Photolithography Step After the element isolation step is completed, a third layer photolithography step for forming the gate electrode 70 shown in FIG. 5 is performed. For this purpose, a polysilicon film is entirely coated on the silicon substrate 60, and an exposure process using the exposure apparatus shown in FIG. 1 is performed to remove the polysilicon film at a position corresponding to the gate electrode 70. After this photolithography process, the gate electrode 70 is formed by etching the polysilicon film.

After that, using the polysilicon region remaining after the etching process as a mask, ion implantation of, for example, As is performed to form a P-type diffusion region 72.

Fourth Layer Photolithography Step This fourth layer photolithography step is used to form the contract holes 76 provided in the oxide film 74.

Photolithography Step for Fifth Layer This photolithography step for the fifth layer is used for forming the wiring layer 78 of Al, for example.

FIG. 6 is a flow chart showing the photolithography process for each layer described above and the procedure for collecting the exposure pattern alignment deviation information for each layer. In the photolithography process of the first layer and the second layer shown in steps 1 and 2 in FIG. 6, the alignment marks of the first layer and the second layer are simultaneously formed on the respective layers. In the exposure step of the photolithography step for the second layer, the wafer 10 is aligned with the alignment mark of the first layer formed in advance as a reference. Then, in step 3, each alignment mark of the first layer and the second layer is measured by the alignment optical system 20. Then, the calculation unit 36 uses the above-described equation (1) to calculate the exposure pattern alignment deviation information between the first and second layers, and the information is stored in the storage unit 34.

In step 4 of FIG. 6, a photolithography process for the third layer is performed, and at the same time, alignment marks for the third layer are formed. Further, in order to carry out the exposure process of the third layer, the alignment position of the wafer 10 is determined based on the alignment mark of the second layer according to the alignment tree of the wafer 10 shown in FIG.

Thereafter, in step 5, the alignment marks of the second layer and the third layer are aligned with the alignment optical system 20.
And the exposure pattern alignment deviation information between the second layer and the third layer is stored in the storage unit 34 in the same manner as described above. Further, in step 6, the layers not in the pair relationship defined in the alignment tree, that is, the first layer
The exposure pattern alignment deviation information between the third layer and the third layer is calculated by the calculation unit 3.
6 is calculated and stored in the storage unit 34.

In step 7 of FIG. 6, a photolithography process for the fourth layer is performed, and at the same time, alignment marks for the fourth layer are formed. When performing the exposure process of the fourth layer, the alignment position of the wafer 10 is calculated based on the alignment mark formed on the second layer according to the alignment tree shown in FIG. Note that the determination of the alignment position of the fourth layer is performed with reference to FIG.
Will be described later.

After the photolithography process for the fourth layer is completed, in step 8, the layers which are not in a pair relation in the alignment tree shown in FIG. 4, that is, the first layer-the fourth layer, the third layer-the fourth layer are The exposure pattern alignment deviation information is calculated by the calculation unit 36 and stored in the storage unit 34.

Then, in step 10, a fifth layer photolithography process is performed, and at the same time, a fifth layer alignment mark is formed. In the exposure process for the fifth layer, the alignment position is calculated based on the alignment mark formed on the fourth layer according to the alignment tree shown in FIG.

Then, in step 11, the exposure pattern alignment information of the specific layers having a pair relationship defined by the alignment tree shown in FIG. 4, that is, the fourth layer to the fifth layer, is passed through the alignment optical system 20. Are measured and stored in the storage unit 34 in the same manner as described above. Furthermore, in step 12, layers that are not in a pair relationship in the alignment tree shown in FIG.
The exposure pattern alignment deviation information of each of the layers, the second layer-the fifth layer, and the third layer-the fifth layer is calculated by the calculation unit 36 and stored in the storage unit 34.

By the above procedure, all the exposure pattern alignment deviation information of different layers between the first layer to the fifth layer is stored in the storage section 34. Therefore, as shown in step 13 thereafter, the exposure pattern alignment deviation information between these layers can be displayed or printed as history information via the output unit 42 and output.

Next, the procedure for determining the alignment position of the wafer 10 in the exposure process for the fourth layer will be described with reference to the flowchart shown in FIG. In step 1 shown in FIG. 7, the second process is performed according to the alignment tree shown in FIG.
The alignment information for the exposure of the fourth layer will be calculated based on the alignment mark formed on the layer.

Then, in order to evaluate the alignment information obtained in step 1, step 2 to step 4
Is executed.

In step 2, the exposure pattern alignment deviation information between the second layer and the third layer and the exposure pattern alignment deviation allowable value of the third layer-the fourth layer are read from the storage unit 34. Next, in step 3, the alignment information obtained in step 1 and the second layer read in step 2
Based on the exposure pattern alignment deviation information of the third layer, the exposure pattern alignment deviation amount between the third layer and the fourth layer is calculated by the calculation unit 36. After that, in step 4, it is determined whether or not the exposure pattern alignment deviation amount between the third layer and the fourth layer obtained in step 3 is smaller than the allowable value read in step 2. If the determination in step 4 is YES, it is determined that the alignment position for exposure of the fourth layer obtained in step 1 is within the allowable range for both the second layer and the third layer, and step 1 The drive control of the wafer stage 12 is performed in accordance with the alignment position information obtained in step.

On the other hand, if the determination in step 4 is NO, the process proceeds to step 5, and the alignment position is corrected in the direction that satisfies the allowable value for the third layer. Then, preferably, steps 3 and 4 are performed again, and it is determined again whether or not the corrected alignment position satisfies the allowable value for the third layer. As long as the determination in step 4 is NO, steps 3 to 5 will be repeated.

By calculating the alignment position for the exposure of the fourth layer by the above method, when the exposure pattern alignment deviation allowable value in the X and Y directions between the respective layers is set to a,
The exposure pattern misalignment amount of the fourth layer with respect to the layer, the third layer, and the fifth layer can be set to a. First layer-
Each average value of the exposure pattern alignment shift amount between the fourth layers in the X and Y directions can be set to (a ² + a ² ) ^1/2 . When the exposure of the fourth layer is performed, it is possible to suppress the exposure pattern alignment deviation amount of the first layer to the fourth layer within the allowable value a by considering the positional relationship with the first layer. When considering exposure pattern misalignment with other layers or multiple layers that do not have a pair relationship defined in the alignment tree, weigh the misalignment tolerance with each layer to determine the suitability of the alignment. You can also

The present invention is not limited to the above embodiments, but various modifications can be made within the scope of the gist of the present invention.

For example, it is stored in the storage unit 34 and is output by the output unit 4
The history information output via 2 is not limited to the information shown in Tables 1 and 2, and various types of exposure pattern alignment deviation amounts between layers when a semiconductor wafer structure is subjected to defect analysis can be evaluated. It is possible to change to the data format of. For example, in the above-described embodiment, the history is output for each substrate to be processed, but the average of a large number of substrates to be processed in one lot can also be output as history information together with the history.

[0069]

According to each of the first to third aspects of the present invention, only the exposure pattern alignment deviation amount between the specific layers having the pair relationship defined by the alignment tree is measured, and the other layers are separated from each other. The exposure pattern alignment shift amount can be calculated. Therefore, the throughput does not decrease while the positional accuracy in the exposure process is improved.

According to each of the inventions of claims 4 to 9, not only the positional relationship between the characteristic layers having the pair relationship defined by the alignment tree, but also another layer or plural layers already formed. Since the alignment position in the exposure process can be determined in consideration of the positional relationship with the layer, the exposure accuracy can be further improved. By increasing the exposure accuracy, finer processing can be performed in the photolithography process including the exposure process.

[0071]

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of an exposure apparatus according to the present invention.

FIG. 2 is a schematic explanatory view for explaining positions of a plurality of alignment marks formed on a semiconductor wafer.

FIGS. 3A and 3B are schematic explanatory diagrams for explaining a scanning operation of alignment marks in upper and lower layers and an output waveform obtained by the scanning operation.

FIG. 4 is a schematic explanatory diagram showing an example of an alignment tree.

FIG. 5 is a cross-sectional view of a MOS transistor formed by using five photolithography processes.

FIG. 6 is a flowchart for explaining a photolithography process of each layer and an operation of collecting exposure pattern alignment deviation information between each layer.

FIG. 7 is a flowchart showing a procedure for determining an alignment position for exposing a fourth layer.

FIG. 8 is a schematic explanatory diagram for explaining an alignment tree and an exposure pattern alignment deviation amount caused thereby.

FIG. 9 is a schematic explanatory diagram showing another example of an alignment tree and an exposure pattern alignment deviation amount caused thereby.

[Explanation of symbols]

 10 substrate to be processed 12 wafer stage 14 excimer laser source 16 reticle 18 projection lens 20 alignment optical system 22 half mirror 30 control unit 32 measurement unit 34 storage unit 36 arithmetic unit 38 determination unit 40 drive control unit 42 output unit 50 lower layer alignment mark 52 Upper layer alignment mark

Claims (9)

[Claims] 1. A plurality of layers are formed on a substrate by using an exposure process, and an alignment mark is formed on each of the layers, and the exposure process of each of the second and subsequent layers is predetermined. Based on the alignment mark of one layer of the lower layer having a pair relationship defined in the alignment tree, in the exposure method for performing the alignment of the substrate, between the specific layers in the pair relationship defined in the alignment tree From each of the alignment marks, a step of measuring and storing position information between the specific layers, and position information between layers other than the specific layers are calculated and stored based on the stored position information between the specific layers. And an exposure method. 2. The alignment mark according to claim 1, wherein the alignment marks are formed at a plurality of locations on each layer, and the position information between the specific layers is based on measured values of the alignment marks formed at a plurality of locations. Position information between layers other than the specific layers is calculated for each position of the alignment marks formed at a plurality of positions based on the position information between the specific layers generated for each position. And an exposure method characterized by being obtained. 3. The overlay accuracy information between different layers is calculated and stored according to claim 2, based on the position information between the specific layers and the position information between layers other than the specific layers generated for each place. An exposure method comprising: 4. A first to Nth substrate is formed on a substrate by using an exposure process.
(N is a natural number of 3 or more), and each of the first to Nth layers is provided with an alignment mark,
In the exposure process of each layer after the second layer, in the exposure method of aligning the substrate based on the alignment mark of one lower layer that has a pair relationship defined in a predetermined alignment tree, the alignment tree A step of measuring and storing the positional information between the specific layers from each of the alignment marks of the specific layers having a pair relationship defined in, and the positional information between the layers other than the specific layers are stored. A step of calculating and storing based on position information between the specific layers, and the step of exposing the third and subsequent layers, wherein the step of exposing one of the lower layers in a pair relationship defined in the alignment tree A first step of calculating alignment information of the substrate based on an alignment mark, and the stored position information and alignment information Based on the position information obtained in the second step by calculating the second step by calculating the position information between one or a plurality of lower layers that are not in the pair relationship defined in the alignment tree. And a third step of determining suitability of the alignment information. 5. In the fourth step, in the third step, a positional deviation allowance value with respect to one or a plurality of lower layers that are not in the pair relationship defined in the alignment tree is stored in advance, An exposure method, wherein it is determined whether or not the position information obtained in the second step satisfies the allowable value. 6. The exposure method according to claim 5, further comprising a fourth step of correcting alignment information of the substrate in a direction satisfying the allowable value. 7. The exposure method according to claim 6, wherein the second step and the third step are performed again after the fourth step. 8. An exposure for aligning and exposing the uppermost layer of a plurality of layers sequentially formed on a substrate based on the mark of a specific layer among alignment marks formed in each layer below the uppermost layer. In the apparatus, means for optically measuring the alignment mark of the specific layer, and alignment information of the substrate for exposure of the uppermost layer are calculated and obtained based on position information of the alignment mark of the specific layer. An arithmetic unit, a storage unit that stores position information between the lower layers, and the alignment information and the position information between the layers stored in the storage unit, based on the position information between the layers, the layers other than the specific layer. An exposure apparatus comprising: a determination unit that determines whether or not the positional displacement of the uppermost layer is appropriate. 9. The operation unit according to claim 8, wherein when the determination unit determines that the top layer is not suitable, the arithmetic unit reduces the positional deviation of the uppermost layer with respect to layers other than the specific layer. An exposure apparatus for correcting alignment information of the substrate for exposure of the uppermost layer.