JPH03158735A - Method for inspecting optical distortion in exposure device - Google Patents

Abstract

PURPOSE:To facilitate control over aberrations by measuring the shape of a mask pattern transferred onto a wafer and finding the deformation rate of the pattern. CONSTITUTION:A circle (contact hole pattern) which has a radius gamma (0.4 - 1.5mum) is installed on the mask side and the mask pattern is transferred onto the wafer. Then the shape of the transferred pattern is measured. Then the deformation rate is found from maximum size and minimum size. Then the focus of the exposure device is shifted within the depth of focus and the deformation rate is measured. A device whose deformation rate deviates from a determined value is re-adjusted. Thus, the device whose distortion is minimized is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical strain inspection method in a semiconductor exposure apparatus.

(Prior Art) Conventionally, as technologies in this field, there have been the following, for example. Inspection of aberrations in exposure equipment used in the semiconductor manufacturing process involves transferring a line and space (L&S) or Siemens star mask pattern onto a wafer and reading the spread of interference fringes.

Here, the latter optical strain inspection method using a Siemens star mask will be explained.

FIG. 5 is a diagram showing the reading location on the wafer surface, and FIG. 6 is a diagram showing the Siemens star pattern (an enlarged view of part A in FIG. 5).

In this optical strain inspection method using a Siemens star mask, the Siemens star mask is transferred onto a wafer and the difference in spread of interference fringes a is read to check for deviations in the 45° direction and 90° direction.

If there is no optical aberration component, the degree of spread of the interference fringes a will normally decrease in the 45° direction and the 90° direction, and the fringes will spread in an arc shape.

Note that this device tilts the wafer around the center point O.
Because of this structure, the spread of interference fringes a can be checked using a single wafer. WII for loading wafers once
For devices without I, the same check can be performed by shifting the focus.

(Problem to be Solved by the Invention) However, with the method described above, reading errors become large due to differences in the appearance of interference fringes depending on the individual processes and differences in the judgment of borders between fringes depending on the reader. There was a problem.

For this reason, there was a problem that aberrations remained in the actual pattern.

The present invention measures the length of the mask pattern transferred onto the wafer, rather than reading the spread of the interference fringes, in order to eliminate the difference in appearance of the interference fringes due to the process described above and the reading error caused by the reader. It is an object of the present invention to provide an optical distortion inspection method for an exposure apparatus in which the variation in optical distortion data due to individual differences is small and aberrations can be easily managed by determining the deformation rate.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an optical distortion inspection method in an exposure apparatus used in a semiconductor manufacturing process, which includes a step of transferring a mask pattern onto a wafer, and a step of transferring a mask pattern onto a wafer. The method includes a step of measuring the shape of the pattern, a step of determining the deformation rate of the transferred pattern based on the measurement result, and a step of inspecting the aberration of the optical system based on the deformation rate. .

(Function) According to the present invention, as described above, an actual pattern (contact hole) is transferred onto the wafer and the length is measured instead of the Siemens star mask, so aberrations within the wafer can be checked. can do.

Furthermore, by shifting the focus to the 1N10UT side, the degree of aberration within the depth of focus can be changed.

Furthermore, since the dimensions of the mask are clear, there will be no variation in the data based on the length measurement results of the pattern transferred onto the wafer.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an example of a mask pattern according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a normal transfer pattern on a wafer without aberration according to the present invention, and FIG. FIG. 4 is a diagram showing an example of a transferred pattern on a wafer when there is an aberration, and FIG. 4 is a diagram showing an example of a transferred pattern on a wafer when there is an aberration in the 90° direction according to the present invention.

(1) First, as shown in Figure 1, radius r (0,4~
1.5μm) circle (contact hole pattern) is installed on the mask side (added to the current resolution check mask)
Then, the mask pattern is transferred onto the wafer.

(2) Next, measure the shape of the transferred pattern.

As a result, if there is no optical aberration, the transferred pattern on the wafer will be circular, as shown in FIG.

Note that in the case of the 21 exposure device, the image is transferred as mask r:wafer r, and in the case of the 5:1 reduction exposure device, the image is transferred as mask ``:wafer r/5''.

Furthermore, when aberration occurs in the 45° direction, the transferred pattern on the wafer becomes elliptical, as shown in FIG. Furthermore,
If the aberration occurs in the 90° direction, it will become an ellipse as shown in FIG.

(3) Therefore, the maximum dimension (M
ay) and the minimum dimension (Win) are measured and substituted into the following equation to obtain the deformation rate. That is, deformation rate (%) = ((Max - Min)/Max
) X100.

(4) Next, shift the focus within the depth of focus of the exposure device and measure the deformation rate. This is to investigate the performance (optical distortion) of the exposure device. Here, if the device deviates from the value determined as the deformation rate, it should be adjusted again, and if the device manufacturer performs the inspection as a final inspection item at the time of factory shipment, it will ensure that the device has minimal distortion. be able to.

Such a deformation rate inspection is performed using the same process that checks the variation in light source energy, distortion, and L&S.

In the above, even if the contact hole is not circular,
Measurement is possible if the mask pattern has equal distances in the 90' direction and 45° direction.For example, as shown in FIG. 7, if the mask pattern is a regular octagon satisfying AE=BF=CG=DH Good too.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, the length of the mask pattern transferred onto the wafer is measured and its deformation rate is determined, so that optical distortion data due to individual differences is The variation is small, and a practical effect can be achieved in controlling aberrations.

Furthermore, by performing this inspection on a single lens, it is possible to manage distortions that occur during assembly.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a mask pattern according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a normal transfer pattern on a wafer without aberration according to the present invention, and FIG. A diagram showing an example of a pattern transferred on a wafer when there is aberration, FIG. 4 is a diagram showing an example of a pattern transferred on a wafer when there is an aberration in the 90° direction according to the present invention, and FIG. 5 shows a reading location on the wafer surface. FIG. 6 is a diagram showing the Siemens star pattern, and FIG. 7 is a diagram showing an example of a mask pattern showing another embodiment of the present invention.

Claims (1)

[Claims] A method for inspecting optical distortion in an exposure apparatus used in a semiconductor manufacturing process, comprising: (a) transferring a mask pattern onto a wafer;
b) measuring the shape of the transferred pattern; (c) determining the deformation rate of the transferred pattern based on the measurement results; and (d) calculating the aberration of the optical system based on the deformation rate. A method for inspecting optical distortion in an exposure apparatus, comprising: a step of inspecting.