CN109917615A - Method for generating photomask using optical proximity correction model - Google Patents

Abstract

A method of photomask being generated using optical proximity effect correction model, including test photomask is provided, which has feature quadrangle, different according to size and the variation of length-width ratio.A variety of different serif patterns are added to each corner of this feature quadrangle.Using the test photomask of each with serif pattern, multiple test patterns are formed on chip.Measurement and at least one geometric parameter for statisticalling analyze multiple test pattern, to determine a specific serif pattern to the corner of each test photomask.Optical proximity effect correction model is established, the specific serif pattern including each test photomask in the corner.Receive Database Layout's pattern.First database layout patterns are generated using optical proximity effect correction model.It executes optical proximity effect and corrects process, to be most preferably melted into second Database Layout's pattern to the first database layout patterns.Photomask is generated according to second Database Layout's pattern.

Description

Method for generating photomask using optical proximity correction model

technical field

The present invention relates to a semiconductor fabrication technique, and in particular to a method of producing a photomask using an optical proximity effect correction model. Optical proximity correction (optical proximity correction), also referred to as OPC below.

Background technique

The formation of the structure of the semiconductor device generally requires photolithography and etching procedures, wherein the photolithography technology requires a photomask with a pattern, and a light source is used to transfer the pattern to the structure layer on the wafer to form the etching mask. Then, using an etching mask, the structure layer is etched to complete the desired structure.

With the decreasing trend of the size of semiconductor integrated circuits, the size of the semiconductor elements therein also shrinks accordingly. Correspondingly, in order to produce the photomask of the microstructure contained therein, the pattern of the photomask should also be reduced. However, due to the effect of optical diffraction, when the pattern from the photomask is transferred to the wafer, it is deformed, in which corners such as right-angled shapes are inevitably curved towards rounded corners.

In order for the microstructure to be more accurately completed on the wafer, its ideal photomask pattern is modified by the mechanism of OPC, wherein the ideal photomask pattern is transferred to the wafer, and the critical dimensions of the pattern on the wafer are adjusted. measurements to obtain the required corrections to the photomask pattern.

However, when the pattern of the photomask is two-dimensionally distributed, there will be a large error in measuring the critical dimension. This kind of error will affect the establishment of the OPC model, resulting in that even if the pattern of the photomask actually used for production is corrected by OPC, the OPC model still has non-negligible errors.

Therefore, how to establish a better OPC model is one of the issues to be considered in the technical research and development, in order to achieve a more accurate correction effect on the photomask pattern.

SUMMARY OF THE INVENTION

The present invention relates to a method of using an OPC model to generate a photomask. By improving the OPC model, the measurement accuracy can be greater, so that the pattern of the photomask can have better accuracy through the OPC model.

According to one embodiment of the present invention, a method of generating a photomask using an optical proximity effect correction model includes providing a test photomask having characteristic quadrilaterals that vary in size and aspect ratio. Add a variety of different serif patterns to each corner of the feature quad. Using each of the test photomasks having the serif patterns, a plurality of test patterns are formed on the wafer. At least one geometric parameter of the plurality of test patterns is measured and statistically analyzed to determine a particular serif pattern for each of the corners of the test photomask. An optical proximity effect correction model is established including the specific serif pattern at the corner of each of the test photomasks. A database layout pattern is received. A first database layout pattern is generated using the optical proximity correction model. An optical proximity effect correction process is performed to optimize the first database layout pattern into a second database layout pattern. A photomask is generated according to the second database layout pattern.

According to an embodiment of the present invention, for the method, the change of the serif pattern corresponds to the change of the size and the aspect ratio of the characteristic quadrilateral.

According to an embodiment of the present invention, for the method, the serif pattern has a structure of at least one layer.

According to an embodiment of the invention, for the method, the serif pattern is a single layer.

According to an embodiment of the present invention, for the method, the serif pattern is a double layer.

According to an embodiment of the present invention, for the method, the characteristic quadrilateral is a square or a rectangle, and the serif pattern includes a right-angled bending structure, which is closely spaced with the corners.

According to an embodiment of the present invention, for the method, the variation of the serif pattern includes a plurality of different variations of the integrated line width and line length.

According to an embodiment of the present invention, for the method, the characteristic quadrilateral includes a plurality of different rectangles.

According to an embodiment of the present invention, for the method, a plurality of different serif patterns are added to each corner of each of the plurality of rectangles.

According to an embodiment of the present invention, for the method, the characteristic quadrilaterals include squares of different shapes.

According to an embodiment of the present invention, for the method, a plurality of different serif patterns are added to each corner of each of the plurality of squares.

According to an embodiment of the present invention, for the method, in the step of providing a test photomask, the number of the feature quadrilaterals of the test photomask is multiple and distributed in a two-dimensional manner.

According to an embodiment of the present invention, for the method, the at least one geometric parameter includes a cross-sectional width of the characteristic quadrilateral at a predetermined position.

Description of drawings

The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a schematic diagram of an unmodified photomask pattern layout according to an embodiment of the present invention;

2 is a schematic diagram of a test pattern formed on a wafer according to the photomask of FIG. 1 according to an embodiment of the present invention;

3 is a schematic diagram of geometric parameters measured on a test pattern according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a photomask pattern layout after correction according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a test pattern formed on a wafer by the photomask after correction according to FIG. 4 according to an embodiment of the present invention;

6 is a schematic diagram of geometric parameters measured on a test pattern according to an embodiment of the present invention;

7 is a schematic diagram of corner correction of a photomask pattern according to an embodiment of the present invention;

8 is a schematic diagram of corner correction of a photomask pattern according to an embodiment of the present invention;

9A to 9D are schematic diagrams of corner correction of a photomask pattern according to an embodiment of the present invention; and

10 is a schematic flowchart of a method for generating a photomask using an optical proximity effect correction model according to an embodiment of the present invention.

Explanation of reference numerals

90: Photomask

92: Wafer

94: Test Photomask

96: Wafer

100: Photomask Pattern

102: Mask Pattern

104: Geometric parameters

106: Geometry parameters

110: Photomask Pattern

112, 112a, 112b, 112c, 112d: Serif pattern

114, 114a, 114b, 114c, 114d: mask patterns

S10, S12, S14, S16, S18, S20, S22, S24, S26: Steps

Detailed ways

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used in the drawings and description to refer to the same or like parts.

The present invention relates to the technology of correcting photomasks by OPC, so that more accurate corrections to photomask patterns can be obtained. It is beneficial to manufacture the fine structure more accurately under the requirement of downsizing of the component size.

The following examples are given to illustrate the present invention, but the present invention is not limited to the examples.

Based on the need to improve the quality of photomask patterns, the present invention conducts practical discussions on photomask patterns and the mechanism of patterns transferred to wafers before proposing technical improvements. FIG. 1 is a schematic diagram of a pattern layout of an unmodified photomask according to an embodiment of the present invention.

Referring to FIG. 1 , only the photomask pattern 100 in one area of the photomask 90 is taken for illustration. In general, the plurality of photomask patterns 100 on the photomask 90 are distributed in a two-dimensional manner. An ideal photomask pattern 100 includes, for example, a rectangle or a combination pattern of rectangles whose four corners are right-angled corners. In the photolithography process of manufacture, for example, the photomask pattern 100 of the photomask 90 will be optically irradiated to the photoresist layer on the wafer, and then through the development process, an etching mask will be formed on the wafer. The mold is used to complete the transfer process of transferring the photomask pattern 100 of the photomask 90 to the wafer.

However, a diffraction phenomenon occurs when the light source passes through the photomask pattern 100 , wherein the diffraction effect is more pronounced in the corners with sharp corners. This results in distortion of the imaged pattern of the photoresist layer on the wafer.

2 is a schematic diagram of a test pattern formed on a wafer according to the photomask of FIG. 1 according to an embodiment of the present invention. Referring to FIG. 2 , the corners of the mask pattern 102 obtained after the photomask pattern 100 is transferred to the photoresist layer on the wafer 92 will be rounded after development. If the geometric parameters of the mask pattern 102 , such as the width or length, are actually measured based on the needs of the OPC process, when compared with the actual photomask pattern 100 , errors will be generated on the mask pattern 102 , thereby affecting the OPC. accuracy of the model.

FIG. 3 is a schematic diagram of geometric parameters measured on a test pattern according to an embodiment of the present invention. Referring to FIG. 3 , in the process of establishing the OPC model, as described above, the photomask pattern 100 for testing will form the mask pattern 102 for testing on the circle. The actual measurement is performed on the geometric parameters 104 of the mask pattern 102, such as width, length, or width at a predetermined position.

Through the research of the present invention, it is found that if a plurality of mask patterns 102 are distributed in a two-dimensional structure, the measurement of the geometric parameter 104 will have a larger error compared to the measurement of a single mask pattern 102 . However, the actual designed patterns generally involve a two-dimensional distribution structure, so the measurement error will affect the accuracy of the OPC model.

The present invention at least conducts in-depth research on the problem of measurement accuracy, and proposes a way to improve the accuracy when establishing an OPC model, in order to establish a more accurate OPC model, which is conducive to the subsequent OPC process for the actual component photomask pattern. Correction for better accuracy.

In the process of establishing the OPC model, in general, the method for establishing the OPC model proposed by the present invention includes providing a test photomask. The test photomask has characteristic quadrilaterals that vary in size and aspect ratio. Add a variety of different serif patterns to each corner of the feature quad. Using each of the test photomasks having the serif patterns, a plurality of test patterns are formed on the wafer. At least one geometric parameter of the plurality of test patterns is measured and statistically analyzed to determine a particular serif pattern for each of the corners of the test photomask. Build an OPC model including the specific serif pattern at the corners of each of the test photomasks.

The accuracy of the OPC model established by the above method can be improved, which is beneficial to the subsequent OPC process to generate the photomask pattern actually required.

For the process to generate the actual photomask required for the actual formation of the device structure, it includes receiving a database layout pattern. The database layout pattern is generally selected based on, for example, the actual component structure to be manufactured. The corners of the pattern at this time have not been corrected. Next, use the previously established OPC model to generate the first database layout pattern, with serif patterns added to the corners. Next, the OPC process is performed to optimize the layout pattern of the first database into the layout pattern of the second database. The second database layout pattern is the corrected data, and a photomask is generated according to the second database layout pattern.

Some examples are given below to describe how to correct the mechanism of the corners of the OPC model, which is beneficial to the measurement of geometric parameters.

FIG. 4 is a schematic diagram illustrating the layout of a photomask pattern after modification according to an embodiment of the present invention. Referring to FIG. 4, in the process of building the OPC model, the test photomask 94 will include a photomask pattern 110, which is the quadrilateral of the feature. The present invention adds a serif pattern 112 at the corners of the photomask pattern 110 to the right-angled corners. A serif pattern 112 is provided along the sharp corners of the corners. The serif pattern 112 may be a single layer or multiple layers, and may vary in thickness and length. The present invention tests various serif patterns 112 for the shape and size of each feature of the quadrilateral, and obtains a specific quadrilateral pattern 112 corresponding to the feature of the photomask pattern 110 in advance. The specific serif pattern 112 is obtained by measuring its at least one geometric parameter, and then analyzing the difference between the measured data and the photomask pattern 110 by means of statistical analysis. In this way, an optimized serif pattern 112 for the quadrilateral of the corresponding feature can be determined.

Taking the photomask pattern 110 of FIG. 4 as an example, adding the serif pattern 112 at the corners will generate different diffraction patterns, which not only compensates the structure of the corners, but also benefits the measurement accuracy. FIG. 5 is a schematic diagram of a test pattern formed on a wafer according to the photomask after correction in FIG. 4 according to an embodiment of the present invention. Referring to FIG. 5 , the photomask pattern 110 of the test photomask 94 is switched to the photoresist layer on the wafer 96 to obtain the mask pattern 114 . The mask pattern 114 contains the effect of the serif pattern 112, the corners of which are more evident.

FIG. 6 is a schematic diagram illustrating geometric parameters measured on a test pattern according to an embodiment of the present invention. Referring to FIG. 6 , the dashed line represents the photomask pattern including the serif pattern 112 . The mask pattern 114 formed on the wafer 96 using the photomask pattern, which is, for example, the photoresist pattern actually formed by the photoresist layer on the wafer 96, is represented by a solid line. For this mask pattern 114, measurements are made for key geometrical parameters 106 such as the width of the mid-position. Statistical analysis of the difference between the measured data and the photomask pattern 110 is performed.

It should be noted here that since different serif patterns 112 will generate different mask patterns 114, the accuracy of the measurement will also vary accordingly. According to the present invention, the accuracy of the measurement is analyzed through the variation of various serif patterns 112 , so that the optimized specific serif pattern 112 can be determined for the corners of the photomask pattern 110 . According to a variety of photomask patterns 110 that have been established in advance, the corresponding optimized serif patterns 112 are obtained through the above process, and an OPC model is established. The corners of the characteristic quads in these OPC models already contain the appropriate serif patterns 112 after screening.

For the variation of the serif pattern 112, it can be done in a number of ways. 7 is a schematic diagram of corner correction of a photomask pattern according to an embodiment of the present invention. Referring to FIG. 7 , the serif patterns 112 at the corners of the mask pattern 114 are closely folded along the corners. The serif pattern 112 is, for example, a single-layer pattern. The thickness and length of the serif pattern 112 may also vary.

FIG. 8 is a schematic diagram of corner correction of a photomask pattern according to an embodiment of the present invention. Referring to FIG. 8 , the mask pattern 114 is, for example, a two-layer structure. Likewise, the thickness and length of the serif pattern 112 may vary.

From the changes in FIGS. 7 and 8 , to describe the changes in the number of layers, the serif pattern 112 may be a single layer or a multi-layer stacked structure.

In addition, the serif pattern 112 also changes according to the different changes in the size and aspect ratio of the quadrilateral. 9A to 9D are schematic diagrams of corner correction of a photomask pattern according to an embodiment of the present invention. Referring to FIGS. 9A to 9D, the quadrilaterals of the mask patterns 114a, 114b, 114c, and 114d are, for example, rectangles or squares. During the multi-sample establishment process of the OPC model, the corresponding serif patterns 112a, 112b, 112c, and 112d will be optimally selected according to different sizes and shapes of different rectangles, and the thickness and length can be changed. , through measurement and statistical analysis to obtain one of the serif patterns, so that a more accurate measurement can be obtained.

From the changes of FIGS. 7 and 8 to FIGS. 9A to 9D, the changes of the serif pattern 112 can be combined with each other to obtain other changed embodiments. The serif pattern 112 of the present invention is not limited to the illustrated embodiments.

As for the method for generating a photomask, FIG. 10 is a schematic flowchart of a method for generating a photomask using an optical proximity effect correction model according to an embodiment of the present invention. Referring to FIG. 10 in conjunction with the structures of FIGS. 4 to 9D , the method of using the OPC model to generate a photomask includes step S10 , providing a test photomask 100 . The test photomask has characteristic quadrilaterals that vary in size and aspect ratio. In step S12, a plurality of different serif patterns are added to each corner of the characteristic quadrilateral. At step S14 , a plurality of test patterns are formed on wafer 96 using each of the test photomasks having the serif patterns 112 . In step S16, at least one geometric parameter of the plurality of test patterns is measured and statistically analyzed to determine a specific serif pattern for each of the corners of the test photomask. In step S18, an optical proximity effect correction model is established, including the specific serif pattern at the corner of each of the test photomasks.

In step S20, a database layout pattern is received. Here, the database layout pattern is determined according to actual needs, and is generally proposed by the user end to the photomask manufacturing end. In step S22, a first database layout pattern is generated using the optical proximity effect correction model. In step S24, an optical proximity effect correction process is performed to optimize the first database layout pattern into a second database layout pattern. In step S26, a photomask is generated according to the second database layout pattern.

In the present invention, an OPC model is pre-established, and the corners of the OPC model are modified to optimize the serif pattern according to the size and shape of the quadrilateral pattern. This OPC model will be included in the subsequent OPC process. At the same time, the accuracy of the final generated photomask can be improved in the OPC process. It is beneficial to transfer the microstructure to the photoresist layer on the wafer more accurately during the photolithography process, and to approach the ideally designed element structure.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (13)

1. a kind of method for generating photomask using optical proximity effect correction model characterized by comprising

Test photomask is provided, the test photomask is different according to size and the variation of length-width ratio with feature quadrangle；

A variety of different serif patterns are added to each corner of the feature quadrangle；

Using each described test photomask with the serif pattern, multiple test patterns are formed on chip；

Measurement and at least one geometric parameter for statisticalling analyze the multiple test pattern, with determine a specific serif pattern to The corner of each test photomask；

Optical proximity effect correction model is established, including test photomask described in each in the specific serif in the corner Pattern；

Receive Database Layout's pattern；

First database layout patterns are generated using the optical proximity effect correction model；

It executes optical proximity effect and corrects process, to be most preferably melted into the second Database Layout to the first database layout patterns Pattern；And

Photomask is generated according to second Database Layout pattern.

2. the method according to claim 1, wherein the variation of the serif pattern is corresponding four side of the feature The size of shape changes with the length-width ratio.

3. according to the method described in claim 2, it is characterized in that, at least one layer of structure of serif pattern.

4. according to the method described in claim 3, it is characterized in that, the serif pattern is single layer.

5. according to the method described in claim 3, it is characterized in that, the serif pattern is double-deck.

6. the method according to claim 1, wherein it is described state feature quadrangle be square or rectangle, The serif pattern includes right angle bending structure, closely sealed with the corner.

7. the method according to claim 1, wherein the variation of the serif pattern includes combined line width and wire length A variety of different variations.

8. the method according to claim 1, wherein the feature quadrangle includes different multiple rectangles.

9. according to the method described in claim 8, it is characterized in that, each the multiple rectangular each described angle It falls, a variety of different serif patterns is added.

10. the method according to claim 1, wherein the feature quadrangle includes square of different shapes.

11. according to the method described in claim 10, it is characterized in that, it is the multiple square each it is described each A variety of different serif patterns are added in corner.

12. the method according to claim 1, wherein being tested in the step of photomask providing, the survey Try photomask the feature quadrangle quantity be it is multiple, be distributed in two dimensions.

13. the method according to claim 1, wherein at least one described geometric parameter includes the feature four Cross-sectional width of the side shape in predetermined position.