JPH1187229A - Aligning method, aligner and manufacture of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize a required sample shots for alingment with a plurality of reference layers by independently selecting the required numbers of shot positions per respective reference layer, in the case that the reference layers in the case of laminated exposure are plural numbers. SOLUTION: In order to specify a sample shot numbers and the sample shot positions per respective reference layers, a plurality of sample shot files for respective reference layers are prepared on an aligner. For example, in the case of two layers of A and B layers, the required alignment precisions with A and B layers are assumed respectively as a and b. Furthermore, the required sample shot numbers in the A and B layers are assumed respectively as Ma and Mb. Furthermore, assuming the total number of sample shots specified as the global alignment to be M, the required sample shot numbers are displayed in a formula, wherein the Max } represents a function which selects a maximum value which selects, while the Int } represents the integer function.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a device by precisely aligning an original plate such as a mask or a reticle with a substrate such as a semiconductor wafer. About.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and high integration of semiconductor integrated circuits such as ICs and LSIs, high alignment accuracy is required. Further, not only the accuracy but also the positioning with respect to one reference layer has conventionally been required, but now a high positioning accuracy is required for each of a plurality of reference layers. In response to this request, there has been proposed a method of measuring marks on a plurality of reference layers, weighing and averaging the measured values for each layer, and performing positioning based on the result (Japanese Patent Laid-Open No. 7-32012, etc.).

In the actual global alignment method, some of the marks provided at each shot position are selected as sample shots for each reference layer, and the alignment marks of each layer in each sample shot are selected. The displacement obtained from the measurement is weighted and averaged based on the positioning accuracy required for each layer.

In Japanese Patent Publication No. Hei 4-63534 and Japanese Patent Laid-Open Publication No. Hei 6-252027, many marks are measured on the first wafer of a lot (usually a group of 25 wafers of the same process). In the measurement of the second and subsequent wafers, a method is disclosed in which the number of marks to be measured is reduced to reduce the influence on the throughput at the time of exposure.

[0005]

However, in the above-described conventional alignment method, since the sample shots of the respective reference layers are the same, when measuring the sample shots, the marks made from the plurality of reference layers are respectively used. The measurement requires measurement time for the number of types of the reference layer, which affects the throughput at the time of exposure.

SUMMARY OF THE INVENTION An object of the present invention is to minimize the number of sample shots and improve the throughput of an exposure apparatus when positioning a plurality of reference layers by a global positioning method.

[0007]

In order to achieve the above object, a method according to the present invention comprises a method of superposing a pattern of an original onto a plurality of shot positions on a substrate and exposing a plurality of shot positions from a plurality of shot positions. The position of the alignment mark at a predetermined shot position is measured, and this measurement is repeatedly performed on the alignment marks on a plurality of types of predetermined reference layers that are overlaid and exposed, and a correction amount is obtained from statistical processing of the measured value. In the method for calculating and aligning the original plate and the substrate, when there are two or more reference layers at the time of overlay exposure, a required number of shot positions in each reference layer are independently selected for each reference layer. I do.

In the positioning method of the present invention, the required number of shot positions to be measured in each reference layer at the time of overlay exposure is usually set by a shot number setting step in which the alignment accuracy required in each reference layer is set in consideration. The shot positions to be measured by the set required number are selected from the shot positions which are set and measured by the alignment at the time of the exposure before the overlay exposure.

The number-of-shots setting step may be a step of calculating the number of measurement shots required for each reference layer from the alignment accuracy required for each reference layer and the total number of shot positions required for alignment. desirable.

Specifically, the number of measurement shots required for each reference layer can be set according to the following equation (1) (where Mai is the number of shot positions of each reference layer, and M is The total number of shot positions required during the overlay exposure, ai indicates the alignment accuracy required for each reference layer, n indicates the number of reference layers, Max 層 indicates a function for selecting the maximum value, and Int ｛｝ Represents an integer function).

[0011]

(Equation 2) As another method, the number of measurement shots required for each reference layer may be set based on a predetermined table representing the relationship between alignment accuracy, measurement accuracy, and the number of measurement shots.

Here, in the positioning method of the present invention, the shot position to be measured is independently selected in a plurality of reference layers, but it is of course possible to select the same shot position in a plurality of reference layers. is there.

When sequentially performing exposure processing of the same pattern on a plurality of substrates, the basic arrangement of the shot positions is created independently for each reference layer on the first sheet of the series of substrates (lots). However, in the measurement of the second and subsequent substrates, it is possible to further reduce the number of shots by selecting a necessary shot position from the created basic arrangement.

The exposure apparatus of the present invention is an exposure apparatus having the means for performing the above-described alignment, and the device manufacturing method of the present invention is a method of manufacturing a semiconductor device using the exposure apparatus of the present invention.

[0015]

【Example】

(First Embodiment) FIG. 4 shows an alignment apparatus according to the present invention. In FIG. 4, R is a reticle, W is a wafer,
1 is a projection lens, and S is an alignment optical system.
As components of S, 2 is an illumination device for alignment, 3 is a beam splitter, 4 is an alignment scope, and 5 is an imaging device.

Illumination light from the illumination device 2 for alignment illuminates a mark on the wafer W via the beam splitter 3 and the projection lens 1, and an image of the mark is projected on the projection lens 1, the beam splitter 3, and the alignment scope 4. An image is formed on the imaging device 5 via the camera. The A / D converter 6 converts the imaging signal from the imaging device 5 into a digital signal. After this digital signal is integrated by the integrating device 7, the position is detected by the position matching device 8 by the template matching method. The position detection device 8 has templates of α, β, and γ, and can switch processing at high speed according to the type of mark. The position measurement information of each mark is 9 CP
The data is statistically processed by U and converted into grid information indicating the position, magnification, and rotation of the entire wafer W. According to the grid information, ten stage driving devices drive eleven XY stages to move the wafer. Reference numeral 12 denotes a storage device for storing information necessary for processing.

FIG. 3 shows an example of an alignment mark arrangement according to the present invention. FIG. 3A is a plan layout view in a shot, and FIG. 3B shows a step structure of a mark. Reference numerals 13 and 15 represent marks formed on the reference layer A, and reference numerals 14 and 16 represent marks formed on the reference layer B.

FIG. 1 shows an example of a measurement shot arrangement at the time of global alignment. A1 to A8 in FIG.
Shows a sample shot for measuring the mark of
Reference numerals 1 to B4 denote sample shots for measuring the mark of the reference layer B. As described above, in the conventional case, the reference layer A
Since the sample shots of the reference layer B and the reference layer B were the same, a total of 16 mark measurements were necessary. In the present embodiment, however, the number of mark measurements of the reference layer B was halved. It is better to do mark measurement.

In this embodiment, in order to specify the number of sample shots and the position of the sample shot for each reference layer, a file of a plurality of sample shots for each reference layer is prepared on the exposure apparatus.

Next, how to determine the number of sample shots
The case of two layers, a layer and a layer B, will be described as an example. The required positioning accuracy with the A layer is a, and the required positioning accuracy with the B layer is b. The number of sample shots required for layer A is M
The number of sample shots required for the layers a and B is Mb. Further, assuming that the total number of sample shots designated as the global alignment is M, the number of sample shots to be obtained is represented by the following equation.

[0021]

(Equation 3) In the above equation, Max ｛｝ represents a function for selecting the maximum value, and InＩｎ
t ｛｝ represents an integer function.

As shown in FIG. 2, the mark of the reference layer A and the mark of the reference layer B may be selected from the same sample shot. In this case, the distance that the stage moves for the measurement between marks is reduced, so that the throughput is improved.

(Second Embodiment) The number of marks measured is closely related to the alignment accuracy. FIG. 5 shows a relationship between the number of measured marks (the number of sample shots) obtained from the simulation and the alignment accuracy. The number of marks to be measured can be determined from the accuracy required for each reference layer and, for example, simulation data as shown in FIG.
In this embodiment, the alignment accuracy for the reference layer A is 4
0 nm, alignment accuracy with reference layer B is 55 nm
It is assumed that Assuming that the measurement accuracy of each mark is 40 nm, it is understood that eight pieces are sufficient for the reference layer A and four pieces are sufficient for the reference layer B.

If the data shown in the graph of FIG. 5 is stored in the exposure apparatus, the number of shots can be determined only by inputting the required positioning accuracy for each reference layer.

(Third Embodiment) From the viewpoint of lot processing,
Many marks can be measured on the first wafer of a lot (usually a group of 25 wafers of the same process), and the measurement number of marks can be reduced in the measurement of the second and subsequent wafers. In this case, as described in Japanese Patent Publication No. Hei 4-63534, an array of shots for which the mark measurement is performed on the first lot of the lot is made, and the second and subsequent shots are used to perform global alignment from the measurement of a small number of marks. Do. Further on, as described in Japanese Patent Application Laid-Open No. 6-252027,
It is also conceivable that the non-linear component is stored as an error array in the measurement of the global alignment of the first image, and the error array stored after omitting the measurement of the non-linear component is reflected at the time of exposure for the second and subsequent images. In any case, in combination with these inventions, in the present embodiment, the basic array made on the first sheet is created for each of the reference layers A and B in the first embodiment, and the array in each reference layer is formed. Are independently applied to the second and subsequent sheets, and the weighted average is calculated at the stage of obtaining the final correction value.

(Fourth Embodiment) Next, a method for producing a device using an exposure apparatus having the above-described positioning means will be described.

FIG. 6 shows a flow of manufacturing micro devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin film magnetic heads, micro machines, etc.). Step 1
In (circuit design), a circuit of a semiconductor device is designed. Step 2 is a process for making a mask on the basis of the designed pattern. Step 3 (wafer manufacturing)
Then, a wafer is manufactured using a material such as silicon or glass. Step 4 (wafer process) is called a pre-process,
An actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. In step 6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 7 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern on the mask is printed and exposed on the wafer by the exposure apparatus having the above-described means for confirming the suitability of the exposure. Step 17 (development) develops the exposed wafer. Step 18 (etching)
Then, portions other than the developed resist image are scraped off. In step 19 (resist stripping), unnecessary resist after etching is removed. These steps 11-1
By repeating step 9, multiple circuit patterns are formed on the wafer.

In this embodiment, in each of the repetitive processes, as described above, during the exposure (step 16),
By performing the efficient alignment, the manufacturing efficiency of the semiconductor device can be improved.

[0030]

As described above, according to the present invention,
Alignment for a plurality of reference layers can be performed while minimizing the influence on the throughput of the exposure apparatus, and the manufacturing efficiency in manufacturing semiconductor devices can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a measurement shot at the time of global alignment according to the present invention.

FIG. 2 is a diagram showing an example of a measurement shot at the time of global alignment according to the present invention.

FIG. 3 is a view showing the arrangement of alignment marks according to the present invention.

FIG. 4 is a view showing an alignment apparatus according to the present invention.

FIG. 5 is a graph showing simulation data of the relationship between the number of sample shots (the number of measurement marks) and the alignment accuracy.

FIG. 6 is a flowchart showing a manufacturing process of a micro device.

FIG. 7 is a detailed flowchart of the wafer process of FIG. 6;

[Explanation of symbols]

1: Projection lens, 2: Illumination device, 3: Beam splitter, 4: Alignment scope, 5: Imaging device, 6: A
/ D converter, 7: integrating device, 8: position detecting device,
9: CPU, 10: stage driving device, 11: XY stage, 12: storage device, 13 to 16: alignment mark, R: reticle, W: wafer, S: optical system, α, β,
γ: template.

Claims (9)

[Claims] When overlaying a pattern of an original onto a plurality of shot positions on a substrate and performing exposure, the position of an alignment mark at a plurality of predetermined shot positions is measured from the plurality of shot positions, and the measurement is repeated. In a method of repeatedly performing alignment marks on a plurality of types of predetermined reference layers that have been subjected to alignment exposure, calculating a correction amount from statistical processing of measured values and performing alignment between the original plate and the substrate, the reference layer The number of shot positions in each reference layer is selected independently for each reference layer when there are two or more layers. 2. A shot number setting step of setting a required number of shot positions to be measured in each reference layer at the time of the overlay exposure in consideration of an alignment accuracy required in each reference layer. The positioning method according to claim 1, wherein a set number of shot positions are selected from shot positions measured in alignment at the time of exposure before exposure. 3. The number-of-shots setting step calculates the number of measurement shots required in each reference layer from the alignment accuracy required in each reference layer and the total number of shot positions required for alignment. 3. The method according to claim 2, wherein the step is a step. 4. The number-of-shots setting step includes calculating the number of measurement shots required in each reference layer by the following equation (1).
The alignment method according to claim 2 or 3, wherein Mai is the number of shot positions of each reference layer, and M is the total number of shot positions required at the time of overlay exposure. , Ai are the alignment accuracy required for each reference layer, n is the number of reference layers, and Max ｛｝
Represents a function for selecting the maximum value, and Int ｛｝ represents an integer function.) (Equation 1) 5. The shot number setting step sets the number of measurement shots required in each reference layer based on a predetermined table representing a relationship between the alignment accuracy, the measurement accuracy, and the number of measurement shots. The positioning method according to claim 2, wherein the positioning is performed. 6. The positioning method according to claim 1, wherein the positioning method selects the shot positions so as to be the same shot positions in a plurality of the reference layers. 7. When sequentially performing exposure processing of the same pattern on a plurality of substrates, a basic arrangement of the shot positions is created independently for each reference layer on a first sheet of the series of substrates. 7. The alignment method according to claim 1, wherein in the measurement of the second and subsequent substrates, a necessary shot position is selected from the created basic arrangement. 8. A device manufacturing method, comprising: performing positioning by the positioning method according to claim 1; and superposing and exposing the pattern of the original on the substrate. 9. A measuring means for measuring an alignment mark at a plurality of predetermined shot positions from the plurality of shot positions when overlaying and exposing a pattern of an original onto a plurality of shot positions on a substrate; In an exposure apparatus that repeatedly performs alignment marks on a plurality of types of predetermined reference layers that have been subjected to overlay exposure, and performs alignment of the original plate and the substrate based on statistical processing of measured values, the reference layer has two layers. In the above case, the measurement unit measures the alignment mark of a shot position independently selected for each reference layer from shot positions measured in alignment at the time of exposure before the overlay exposure. An exposure apparatus, comprising: