JPS5910054B2 - How to check the pattern accuracy of mask original plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for checking the pattern accuracy of a mask original, which makes it possible to measure the accuracy of a mask pattern. It is intended to be suitably applied to cases such as checking for defects caused by lens aberrations of a lens.

Optical mask originals used in semiconductor manufacturing technology are required to have fine patterns and high precision, and are generally obtained by reducing the original drawings, which have been enlarged several hundred times, using photographic techniques. In this case, the pattern dimensional accuracy of the mask original is approximately ±2 μm, and it is difficult to reduce the accuracy to less than this. This is because there is a limit to confirmation of lens aberration or reduction magnification during reduction, that is, confirmation using conventional optical devices. On the other hand, in recent surface acoustic wave devices, when forming striped electrodes, it is required to suppress the stripe pitch of the striped electrodes to an accuracy of 0.2μ or less, and the distance between transducers to an accuracy of 1μ or less. .

Furthermore, when manufacturing a two-dimensionally wide device such as a charge transfer device (CCD), importance is placed on the weighting accuracy between each transfer section.
However, in any case, it is difficult to select a highly accurate and appropriate mask original using conventional confirmation methods using optical systems. Also, in the case of reduction, the lens has a peculiar characteristic due to lens aberration (the reduction ratio does not match between the center and the periphery of the screen).
If you can identify this habit, for example, you can correct the original drawing based on this in advance and make a more accurate reduction.

In view of the above-mentioned points, the present invention makes it possible to check the accuracy of the pattern dimensions itself, to select an appropriate mask original suitable for the purpose, or to eliminate the peculiarities caused by lens aberrations of optical lenses such as reduction lenses. The present invention provides a method for checking the pattern accuracy of a mask original plate that can be detected.

In the present invention, a striped electrode pattern for a surface acoustic wave device is attached to a mask original plate, a surface acoustic wave device is fabricated using this striped electrode pattern, and the frequency characteristics of the surface acoustic wave device, that is, one notch frequency is measured. By doing so, the dimensional accuracy of the pattern on the mask original plate can be confirmed.

Hereinafter, an example of the method for checking the pattern accuracy of a mask original according to the present invention will be explained with reference to the drawings.

Figures 1 and 2 illustrate the case where the method for checking the pattern accuracy of a mask master is applied to the manufacture of semiconductor devices.

In the present invention, first, as shown in FIG. 1, an appropriate magnification, for example, 2
An original drawing 1 enlarged 00 times is provided.

Along with the main pattern 2 for the semiconductor device, this original drawing 1 also includes a pattern 3 of striped electrodes for a surface acoustic wave element, which is used to confirm the dimensional accuracy of the main pattern in the reduced mask original. In this case, the striped electrode pattern 3 may have a pair of pattern portions 3a and 3b facing each other at a predetermined distance. Next, a mask original of the original size is obtained by reducing the size of this original drawing 1, but at this time, the second
As shown in the figure, a plurality of mask original plates 4 [4A14B, 4C, 4D, 4E, . . . , 4A14B, 4C, 4D, 4E, ...
...]. An example is 200
When you reduce the double enlarged original drawing 1 at a reduction rate of 1/20, and further reduce it at a reduction rate of 1/10 to obtain the original mask at the original size, what is the reduction rate? Using this as a standard, create multiple reduced versions with slightly different reduction ratios, for example, at the time of the first 1/20 reduction, each one has a reduction ratio of... b
, these multiple] are further reduced at a reduction rate of 1, and each is compared to the original drawing 1? ,? Multiple mask originals 2012024A, 4B, 4C, 4 reduced to...
Obtain D, 4E,...

Therefore, each mask original 4 has a main pattern 5 for a semiconductor device and a pair of striped electrode patterns 6 [6a, 6b] for a surface acoustic wave element, each having a slightly different original size. Next, for each mask master plate 4 obtained in this way, the original dimensional accuracy of each main pattern 5 is measured using its own striped electrode pattern 6.

That is, as shown in FIG. 3, for example, Bi
Piezoelectric substrate 7 such as l2GeO2O or LiNbO3
A surface acoustic wave filter 12 is provided on the top surface of the device, in which a pair of strip-shaped electrodes 8 and 9 are formed facing each other at a predetermined distance from each other and constitute an input transducer 10 and an output transducer 11, respectively. This surface acoustic wave filter 12 is provided for each mask original 4A, 4B, 4Cc, . . . . The frequency characteristics of this surface acoustic wave filter 12 are as shown in FIG. 4, and the center frequency of the pass band at this time is F. Alternatively, the notch frequencies f1 and F2 are the pitch L of the striped electrodes 8 and 9, the number of electrode pairs N, and the sound velocity of the surface wave 8.
related to etc. Here, if the frequency of the surface acoustic wave filter 12 is measured, for example, one notch frequency f1 or F2 that can be measured with high accuracy, the actual dimensions of the striped electrodes 8 and 9 can be converted from the notch frequency f1 or F2, and The dimensional accuracy of the main pattern 5 of the mask original 4 can be measured with a dimensional accuracy of 8.9.

Therefore, in this example, one notch frequency f1 or F2 of each surface acoustic wave filter 12 formed using the striped electrode pattern 6 of each mask original 4A, 4B, 4C is measured, and the notch frequency f1 or F2 of each surface acoustic wave filter 12 is measured. , . . . determines the dimensional accuracy of the main pattern 5.

If the dimensional accuracy of the main pattern 5 of each mask original plate 4A, 4B, 4Cc, etc. can be determined, a high-precision mask original plate according to the purpose is selected from among them, and the selected mask original plate is used. If a semiconductor device is manufactured using this method, a highly accurate semiconductor device can be obtained. Incidentally, in the plurality of mask originals 4 obtained as described above, the theoretical value of the notch frequency is 60.
A mask original plate with a notch frequency in the range of 60.25 MHz to 50 KHz for 25 MHz was obtained, and when converted to pattern dimensions, the pitch of the striped electrode is ±
0.03μ, which corresponds to an accuracy of ±1μ between transducers of several lengths.

In this way, accurate measurements on the order of 10 to 10 are possible when the -7 -8 frequency is determined, and therefore, the accuracy confirmation of the mask master plate 4 is much more accurate than conventional optical confirmation. becomes.

In the above example, the present invention is applied to a mask original that is actually used, but it can also be applied to, for example, checking for defects caused by lens aberration of a reduction lens of a reduction device.

FIGS. 5 and 6 are examples of such cases. Regarding lens aberrations, spherical aberration does not change between the center and the periphery of the screen, but astigmatism, coma aberration, distortion aberration, etc. vary greatly between the center and the periphery of the screen, and in general, the diagonal length D of the screen and the lens As the ratio D/f of the focal length f increases (towards the periphery), it increases rapidly.

Therefore, in this example, first, as shown in FIG. 5, a chart 14 is created in which a plurality of striped electrode patterns 13 for surface acoustic wave elements having the same size and shape for measurement are arranged diagonally and orthogonally to each other. This chart 14 is reduced through a reduction lens to be checked to produce a mask original 15 having a striped electrode pattern 16 of actual size as shown in FIG. Each striped electrode pattern 1 of this mask original 15
6 to form surface acoustic wave filters as shown in FIG. 3, the notch frequency of each surface acoustic wave filter is measured, and the deviation of the notch frequency between the center and the periphery of the mask original 15 is measured. In this way, it is possible to check for deviations in the reduction dimensions in various parts of the screen due to aberrations of the reduction lens at this time, so-called lens quirks. Therefore, if the peculiarities of the reduction lens are known, the pattern of the enlarged original image can be corrected in advance when the reduction lens is used to perform the reduction, and more accurate reduction can be expected. As mentioned above, by providing a striped electrode pattern for a surface acoustic wave element on a mask original plate, the pattern dimensional accuracy of the mask original plate can be measured with high precision, which is useful in, for example, semiconductor manufacturing technology. This method can be applied to the selection of a mask original to be used or its appropriate mask, or can be applied to check and correct the aberrations of the reduction lens in a reduction device to perform more accurate reduction. .

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of an enlarged original drawing when the present invention is applied to a mask original plate for semiconductor devices, and FIG. FIG. 3 is a plan view of an example of a surface wave filter used to explain the present invention; FIG. 4 is a frequency characteristic diagram thereof; FIG. 5 is a plan view of the mask original plate; FIG. 6th enlarged plan view of the chart when
This figure is a plan view of a mask original plate according to the present invention obtained by reducing the chart of FIG. 5. 1 is the original drawing, 2 and 5 are the main patterns, 3 and 6 are striped electrode patterns for surface acoustic wave elements, 4 [4A14B14C
, 4D, 4E1...] are mask originals.

Claims (1)

[Claims] 1. Confirming the pattern accuracy of the mask original by creating a surface acoustic wave element from a mask original that has a desired pattern and a striped electrode pattern for surface acoustic wave elements, and measuring the pattern accuracy of the original by measuring its frequency characteristics. Method.