JPH08330205A - Alignment method - Google Patents

Abstract

PURPOSE: To provide an alignment method with improved production efficiency without requiring much time and labor and without stopping a device. CONSTITUTION: In an alignment method in photolithography process, first the distortion of a projection lens of an exposure device where layer to be aligned is exposed to light is measured (Step S1). Then, the position of the alignment mark formed at the layer to be aligned is measured (Step S2) and a distortion error value at that position is obtained (Step S3). Then, the obtained distortion error value is inputted to an exposure device as an offset value in advance (Step S4).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment method using photolithography, which is useful for microfabrication for patterning using a photoresist film in the manufacture of semiconductor devices.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, alignment accuracy is one of the basic performances required in a photolithography process. Alignment errors can be roughly classified into offset, scaling, and rotation errors. Among these error factors, the variation in alignment accuracy (3σ) is mainly due to scaling and rotation errors, and | X | (average value of alignment errors) is mainly due to offset.

Here, in the conventional alignment method, the pilot processing method is used to remove the offset error. A flowchart of this pilot processing method is shown in FIG. As shown in FIG. 6, pattern exposure / development is performed on the pilot wafer of the alignment layer (step S11), and then the offset error value of the pilot wafer is measured (step S12). Next, the measured offset error value is input to the exposure apparatus and the main body lot is processed (step S13). After the lot processing, the offset error value is measured before shipping, and if it is within the standard, the process proceeds to the next step (step S1).
4).

[0004]

In the conventional alignment method by the pilot processing method, the offset error value is set by using the pilot wafer for each lot, so the apparatus stops until the pilot processing is completed and the production efficiency is lowered. In addition, the pilot processing procedure required a lot of time and labor.

FIG. 7 shows an offset error value when the gate forming process of the device (0.5 μm rule) is pilot-processed by each exposure apparatus. In FIG. 7, the horizontal axis indicates the number (number) assigned to each exposure apparatus, and ○ indicates the Y-axis offset error value.
● indicates the X axis offset error value. From this FIG.
It can be seen that the offset error depends on the exposure apparatus. The difference in the offset error value depending on the exposure apparatus is considered to be due to the distortion of the projection lens or the difference in the stage system. For this reason, a method of improving alignment accuracy by performing a pilot process, measuring an offset error value, and feeding it back is taken. Not only is this method labor-intensive, but it is expected that feedback by the pilot processing method will be rather difficult when in-line is performed.

An object of the present invention is to provide an alignment method which does not require much time and labor, does not stop the apparatus, and has high production efficiency.

[0007]

An alignment method according to claim 1, which is an alignment method in a photolithography process, comprising a step of measuring distortion of a projection lens of an exposure apparatus and an alignment mark formed on an alignment target layer. Measuring the position of
It is characterized by including a step of obtaining a distortion error value at the position of the alignment mark and a step of inputting the distortion error value as an offset value to the exposure apparatus.

An alignment method according to a second aspect is an alignment method in a photolithography process, characterized in that an alignment mark formed on an alignment layer is arranged at the center of a projection lens of an exposure apparatus. The alignment method according to a third aspect is the alignment method according to the first or second aspect, wherein an offset error value by the stage system of the exposure apparatus is set to 0 μm.

[0009]

According to the alignment method of the present invention, the distortion of the projection lens of the exposure apparatus is measured, the position of the alignment mark formed on the aligned layer is measured, the distortion error value at that position is obtained, and this distortion error value is calculated. The offset value is input to the exposure apparatus. With this method, compared to the conventional pilot processing method that uses a pilot wafer for each lot to set the offset error value, the reduction in production efficiency due to the stop of the equipment is suppressed, and as with the pilot processing method, many There is no need to spend time and effort.

Further, according to the alignment method of the present invention, the alignment mark formed on the layer to be aligned is arranged at the center of the projection lens of the exposure apparatus. This method improves the alignment accuracy compared with the conventional pilot processing method, and suppresses the decrease in production efficiency due to the stop of the device compared with the conventional pilot processing method. There is no need to spend time and effort.

[0011]

【Example】

[First Embodiment] A first embodiment of the present invention will be described. FIG. 1 is a flow chart showing an alignment method according to the first embodiment of the present invention.

First, the distortion of the projection lens of the exposure apparatus that has exposed the layer to be aligned is measured (step S1). Next, the position of the alignment mark formed on the layer to be aligned is measured (step S2), and the distortion error value at that position is obtained (step S3). Next, the obtained distortion error value is input in advance to the exposure apparatus as an offset value (step S4). After that, exposure / development is performed, the offset error value is measured, and if it is within the standard, the process proceeds to the next step.

Further, description will be made with reference to FIG. 2 and specific numerical values. FIG. 2A shows a layout of the shot (exposure) area 1, the alignment marks 2 and 3 (2; Y axis, 3; X axis) and the main body device region 4, and FIG. 2B shows the alignment mark position. Shows the distortion value of the projection lens at. The distortion value measured here is the distortion value X = at the position of the alignment mark 2 on the Y axis.
The distortion value Y is 0.05 μm at the position of the alignment mark 3 on the X axis, and the offset value input to the exposure apparatus at this time is X = −0.0.
5μm, Y = -0.05μm, the main body is exposed,
After development, the offset error is measured.

FIG. 3 shows the case of using the method according to the first embodiment (● in FIG. 3) and the conventional pilot processing method in the gate forming process of the device (0.5 μm rule). (O in FIG. 3) indicates data (offset error value) obtained by performing alignment measurement at the time of lot shipment. FIG. 3A shows an X-axis offset error value for each exposure apparatus, FIG. 3B shows a Y-axis offset error value for each exposure apparatus, and the horizontal axes of FIGS. 3A and 3B are The number of each exposure device is shown. The alignment measurement number here is 5 shots in the wafer and 4 points in the shot, that is, 20 points in total. From FIG. 3, the offset error at the time of shipment between the alignment method of this embodiment and the conventional pilot processing method is within ± 0.05 μm, and no significant difference is seen. Here, the offset error due to the stage system of the exposure apparatus is set to be 0 μm.

According to this embodiment, as compared with the conventional pilot processing method in which an offset error value is set by using a pilot wafer for each lot, the reduction in production efficiency due to the stop of the apparatus is suppressed, and the pilot It is not necessary to spend a lot of time and labor unlike the processing method, and it is possible to greatly reduce the time and improve the productivity.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
An example will be described. FIG. 4 is a layout diagram showing an alignment method according to the second embodiment of the present invention. In FIG. 4, 1 is a shot (exposure) area, 5 is a projection lens of an exposure apparatus, and 6 is an X-axis and Y-axis alignment mark formed on an alignment layer.

In this embodiment, the position of the alignment mark 6 is arranged at the center of the projection lens 5 of the exposure apparatus. By disposing the alignment mark 6 in this way, the distortion error of the projection lens 5 can be removed, and the device difference of the offset error due to the exposure device does not occur. Here, the offset error due to the stage system is set to be 0 μm. Figure 5 shows the device (0.5 μm
When the alignment is performed by each exposure device in the gate formation step of (rule), the offset error value at the time of lot shipment is shown. In FIG. 5, the horizontal axis indicates the number (number) assigned to each exposure apparatus, the circle indicates the Y axis offset error value, and the black circle indicates the X axis offset error value.
From FIG. 5, no difference in offset error between the exposure apparatuses was observed, and a value close to 0 μm was measured.

According to this embodiment, the alignment accuracy is improved as compared with the conventional pilot processing method, and the reduction in production efficiency due to the stop of the apparatus is suppressed as compared with the conventional pilot processing method, and the pilot efficiency is suppressed. It is not necessary to spend a lot of time and labor unlike the processing method, and it is possible to greatly reduce the time and improve the productivity.

[0019]

According to the alignment method of the present invention, the distortion of the projection lens of the exposure apparatus is measured, the position of the alignment mark formed on the alignment layer is measured, and the distortion error value at that position is obtained. The value is input to the exposure apparatus as an offset value. With this method, compared to the conventional pilot processing method that uses a pilot wafer for each lot to set the offset error value, the reduction in production efficiency due to the stop of the equipment is suppressed, and as with the pilot processing method, many Since it is not necessary to spend time and labor, it is possible to significantly reduce time and improve productivity.

Further, according to the alignment method of the present invention, the alignment mark formed on the layer to be aligned is arranged at the center of the projection lens of the exposure apparatus. This method improves the alignment accuracy compared with the conventional pilot processing method, and suppresses the decrease in production efficiency due to the stop of the device compared with the conventional pilot processing method. Since it is not necessary to spend time and labor, it is possible to significantly reduce time and improve productivity.

[Brief description of drawings]

FIG. 1 is a flowchart of an alignment method according to a first embodiment of the present invention.

FIG. 2 is a layout diagram for explaining an alignment method according to a first embodiment of the present invention.

FIG. 3 is a comparison diagram of an offset error between the alignment method of the first embodiment of the present invention and the conventional pilot processing method.

FIG. 4 is a layout diagram showing an alignment method according to a second embodiment of the present invention.

FIG. 5 is a diagram showing the device dependency of an exposure device of an offset error according to the alignment method of the second embodiment of the present invention.

FIG. 6 is a flowchart of a conventional alignment method.

FIG. 7 is a diagram showing the device dependency of an exposure device of an offset error by a conventional alignment method.

[Explanation of symbols]

 1 Shot (exposure) area 2 Alignment mark (X axis) 3 Alignment mark (Y axis) 4 Body device area 5 Projection lens 6 Alignment mark (X, Y axis)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/30 525X

Claims (3)

[Claims] 1. An alignment method in a photolithography process, which comprises a step of measuring distortion of a projection lens of an exposure apparatus, a step of measuring a position of an alignment mark formed on an alignment layer, and a position of the alignment mark. And the step of inputting the distortion error value as an offset value to the exposure apparatus. 2. An alignment method in a photolithography process, wherein an alignment mark formed on an alignment layer is arranged at the center of a projection lens of an exposure apparatus. 3. The alignment method according to claim 1, wherein the offset error value by the stage system of the exposure apparatus is set to 0 μm.