CN1940715A - Method of correcting photomask pattern and method of forming same - Google Patents

Abstract

A method for correcting a photomask pattern includes providing a test photomask having a plurality of original patterns formed according to an original drawing data. Then, the original pattern on the test photomask is transferred to the first photoresist layer to form a plurality of first developed patterns correspondingly, and the first size of the first developed patterns is measured. Then, a pattern shrink process is performed on the first developed pattern to correspondingly form a plurality of first shrunk patterns, and a second size of the first shrunk patterns is measured. Then, a deviation value between the first size and the second size is calculated, and the original drawing data, the first size, the second size and the deviation value are collected to obtain a database. Then, the data of the database is used to establish an optical proximity effect correction model. Then, the original drawing data is corrected according to the optical proximity correction model to obtain corrected drawing data.

Description

Method of correcting photomask pattern and method of forming same

technical field

The present invention relates to a method for correcting photolithography and its forming method, in particular to a method for correcting a photomask pattern and its forming method.

Background technique

Recently, the semiconductor industry tends to shrink the design and development of circuit components, and one of the most important steps in the entire semiconductor process is photolithography. Anything related to the structure of semiconductor elements, such as the pattern of each layer of thin film, is determined by the photolithography process to determine the size of its Critical Dimension (CD), which is also determined by the development of photolithography process technology.

Nowadays, in response to the development direction of device size reduction and resolution improvement, KrF exposure machine can be used with phase shift mask (Phase Shift Mask, PSM), but in order to better break through the technology node of the process, exposure machine needs to use smaller wavelength The light source is, for example, krypton fluoride (KrF, 248nm), argon fluoride (ArF, 193nm), fluorine (F ₂ , 157nm), argon (Ar ₂ , 126nm), etc., so that the element can obtain a smaller line width, And further get a smaller component size. However, the exposure tools mentioned above are still very expensive, or are still under development.

Therefore, an innovative pattern miniaturization technology, Chemical Shrink Process, was proposed. The chemical shrinkage process is to apply the chemical shrinkage reagent on the photoresist layer that has been exposed and developed, and perform a baking step to form a new material layer on the side wall of the pattern in the photoresist layer. In order to achieve the purpose of pattern reduction.

Generally speaking, using the chemical shrinkage process to shrink the pattern is to estimate the amount of shrinkage with a single bias (Bias) value (bias value = critical dimension of the pattern after miniaturization - critical dimension of the pattern after development), and then use This deviation value determines the target critical dimension (Target CD) of the developed pattern on the photoresist layer, and the target CD corrects the size of the original pattern on the photomask. However, when the original patterns to be transferred to the wafer have the same critical dimensions but different pattern densities, it is impossible to control the size of the original patterns on the photomask with a single deviation value. After the photolithography process and the chemical shrinkage process, the critical dimensions of the patterns presented on the wafer are all allowable pattern dimensions. In this way, the yield and reliability of the process and the performance of the device will be seriously affected.

Contents of the invention

In view of this, the object of the present invention is to provide a method for correcting a photomask pattern and a method for forming the same, which can correct the photomask pattern with different critical dimension deviation values, so that the pattern formed on the wafer is more accurate and improves the accuracy of the photomask pattern. Process reliability and yield.

The invention proposes a method for calibrating a photomask pattern. In the calibrating method, a test photomask is firstly provided, and a plurality of original patterns have been formed on the test photomask according to an original drawing data. Then, the original pattern on the test photomask is transferred to a first photoresist layer to form a plurality of first developed patterns correspondingly, and the first size of each first developed pattern is measured. Next, a pattern miniaturization process is performed on the first developed pattern to form a plurality of first miniaturized patterns correspondingly, and the second size of each first miniaturized pattern is measured. Then, calculate the deviation value of the first size and its corresponding second size, and collect the original drawing data, the first size, the second size and the deviation value to obtain a database. Then, use the data in the database to establish an optical proximity effect correction model. Next, the original drawing data is corrected according to the optical proximity effect correction model to obtain corrected drawing data.

According to the embodiment of the present invention, after establishing the optical proximity effect correction model, performing a first verification step to verify the optical proximity effect correction model. Wherein, the first verification step is, for example, using the original drawing data and the first dimension to establish a verification fitting curve model. Then, compare the optical proximity effect correction model with the verification fitting curve model to determine whether the plurality of second post-development patterns preformed on the second photoresist layer are correct, and if not, repeat to establish the optical Steps for Proximity Effect Correction Model. In one embodiment, after the first verification step, a second verification step is further included to verify the optical proximity effect correction model. Wherein, the second verification step is, for example, comparing the optical proximity effect correction model with the original drawing data to determine whether the plurality of second miniaturized patterns preformed on the second photoresist layer are correct, and if not, repeat The step of establishing an optical proximity effect correction model is performed.

According to the embodiments of the present invention, the pattern miniaturization process mentioned above is, for example, a chemical miniaturization process, a heat flow process, a chemical amplification composition line width process, and a Ravenson type phase transfer photomask double exposure process.

According to the embodiments of the present invention, the above-mentioned original drawing data are, for example, key dimensions, pattern density, and line width to space ratio.

The invention further provides a method for forming a photomask pattern. The forming method first forms a plurality of original patterns on a test photomask according to an original drawing data. Then, the original pattern on the test photomask is transferred to the first photoresist layer to form a plurality of first developed patterns correspondingly, and the first dimensions of these first developed patterns are measured. Afterwards, a pattern miniaturization process is performed on the first developed patterns to form a plurality of first miniaturized patterns correspondingly, and a second size of the first miniaturized patterns is measured. Next, calculate the deviation value of the first size and its corresponding second size, and collect the original drawing data, the first size, the second size and the deviation value to obtain a database. Then, the data in the database is used to establish an optical proximity effect correction model. Subsequently, the original drawing data is corrected according to the optical proximity effect correction model to obtain corrected drawing data. Then, a writing step is performed to write the corrected drawing data on a photomask to form a pattern on the photomask.

According to the embodiment of the present invention, after establishing the optical proximity effect correction model, performing a first verification step to verify the optical proximity effect correction model. Wherein, the first verification step is, for example, using the original drawing data and the first dimension to establish a verification fitting curve model. Then, compare the optical proximity effect correction model with the verification fitting curve model to determine whether the plurality of second developed patterns preformed on the second photoresist layer are correct, and if not, repeat the process of establishing optical proximity Steps in the Effect Modification Model. In one embodiment, after the first verification step, a second verification step is further included to verify the optical proximity effect correction model. Wherein, the second verification step is, for example, comparing the optical proximity effect correction model with the original drawing data to determine whether the plurality of second shrunken patterns preformed on the second photoresist layer are correct, and if not, then Repeat the steps to model the corrected optical proximity effect.

According to the embodiments of the present invention, the pattern miniaturization process mentioned above is, for example, a chemical miniaturization process, a heat flow process, a chemical amplification composition line width process, and a Ravenson type phase transfer photomask double exposure process.

According to the embodiments of the present invention, the above-mentioned original drawing data are, for example, key dimensions, pattern density, and line width to space ratio.

According to an embodiment of the present invention, the above-mentioned writing step uses an electron beam or a laser beam to perform it.

The present invention utilizes the effect produced by the chemical shrinkage process and the influence of the optical proximity effect to establish a database and perform calculations to obtain an optical proximity effect correction model, and correct the original drawing data with the optical proximity effect correction model , to obtain the target critical dimension of the originally designed circuit layout pattern, which can save process cost and improve process yield and reliability.

In order to make the above and other objects, features and advantages of the present invention more comprehensible, the present invention will be described in more detail below with reference to the accompanying drawings and preferred embodiments.

Description of drawings

FIG. 1 is a flowchart of steps of a method for forming a photomask pattern according to an embodiment of the present invention.

simple notation

100, 110, 120, 130, 140, 150, 160, 170, 180: steps

Detailed ways

FIG. 1 is a flowchart of steps of a method for forming a photomask pattern according to an embodiment of the present invention.

Referring to FIG. 1 , in step 100 , a test photomask is provided, and a plurality of original patterns have been formed on the test photomask according to an original drawing data. For example, the original drawing data of the originally designed circuit layout pattern is written on a test photomask to form a plurality of original patterns on the test photomask. The above-mentioned original drawing data includes the key dimensions, pattern density, and line width-to-spacing ratio (Duty Ratio) of the originally designed circuit layout pattern.

Step 110 , transferring the original pattern on the test photomask to the photoresist layer, so as to form a plurality of developed patterns in the photoresist layer, and measure the critical dimension of each developed pattern. Wherein, the method of transferring the original pattern on the test photomask to the photoresist layer is, for example, performing exposure and development steps, and these steps are known to those skilled in the art, and will not be repeated here. The method for measuring the critical dimension of the pattern after development is, for example, using a scanning electron microscope (Scanning Electron Microscopy, SEM) or an optical microscope (Optical Microscopy, OM) to measure it. Generally speaking, when the original pattern on the test photomask is transferred to the photoresist layer through exposure and development steps, it will be interfered by the light source in the exposure step, and the photoresist layer of the photoresist layer will Due to the influence of the agent, the pattern formed after development will be rounded at the right angle, the end of the pattern will shrink (Line-end Shortening), and the line width will be reduced or increased. It is the so-called Optical Proximity Effect (OPE).

Step 120 , performing a pattern miniaturization process on the developed pattern in the photoresist layer to form a plurality of miniaturized patterns correspondingly, and measuring the critical dimension of each miniaturized pattern. Likewise, the method for measuring the critical dimension of the miniaturized pattern is, for example, using a scanning electron microscope or an optical microscope to measure it. In addition, the above pattern miniaturization process can be, for example, Chemical Shrink Process, Thermol Flow Process, Chemical Amplification of Resist Line Process, Ravenson type phase transfer photomask Double Exposure with Levnson-type Phase Shift Masks Process, etc.

In this embodiment, the chemical shrinkage process is taken as an example for illustration, but of course the present invention is not limited thereto. The chemical shrinkage process is also called Resolution Enhancement Lithography Assist by Chemical Shrink (RELACS) technology, which, for example, uses chemical shrinkage reagents to coat a photoresist layer that has been formed with a pattern after development. and perform a baking step to form a new material layer on the sidewall of the developed pattern in the photoresist layer, so as to achieve the purpose of shrinking the pattern. In addition, it should be noted that after the developed pattern is subjected to the chemical shrinkage process, the shrinkage amount of the formed pattern will vary depending on the key size, density, and line-to-space ratio (Duty Ratio) of the pattern. As mentioned above, the shrinkage amount of the miniaturized pattern refers to the deviation (Bias) value between the critical dimension of the miniaturized pattern and the critical dimension of the developed pattern.

Step 130, establishing a database. It is, for example, calculating the deviation value of CD of each developed pattern from its corresponding CD of each miniaturized pattern, and collecting original drawing data, CD of developed pattern, CD of miniaturized pattern and both The deviation value to build a database.

Step 140, using the data in the database to establish an Optical Proximity Correction Model (OPC Model). For example, an existing software package, such as optical proximity correction (OPC) software, is used to input data from a database, and after calculation and correction, an optical proximity correction model is established.

In particular, because there are quite a lot of parameters affecting the chemical shrinkage process, including reaction concentration, reaction time, diffusion rate and reaction area, etc., in order to satisfy such a complex reaction mechanism, a lot of data must usually be collected to deduce its reaction kinetics Mathematical models such as mass transfer and mass transfer can correct the photomask pattern and obtain the target critical dimension of the originally designed circuit layout pattern. Moreover, coupled with the influence of the optical proximity effect, more data and more complex inferences are necessarily required before the target critical dimension of the originally designed circuit layout pattern can be obtained. And the present invention uses the effect produced by the chemical shrinkage process and the influence of the optical proximity effect to establish a database, and utilizes the existing software package (OPC software) to calculate these data to establish an optical proximity effect correction model, The original drawing data can be corrected to obtain the target critical dimension of the originally designed circuit layout pattern, which can save process cost and improve process yield and reliability.

In one embodiment, after step 140, a first verification step (step 150) can also be performed to verify the above-mentioned optical proximity effect correction model, the purpose of which is to detect if the corrected drawing data is written on the photomask , and transferred to the photoresist layer, whether the pattern in the photoresist layer is the size allowed by the process. The first verification step is, for example, using an existing software package, such as Post OPC Verification (Post OPC Verification) software, to establish a detection fitting curve model with the original drawing data and the critical dimension after development. Then, compare the optical proximity effect correction model with the verification fitting curve model to determine whether the multiple developed patterns in the pre-pattern miniaturization process are correct. If the optical proximity effect correction model does not match the verification fitting curve model, it means that the pattern is connected to the pattern after development (Pattern Bridge) or the opening pattern is not opened, etc., so step 140 should be repeated to re-establish the optical proximity effect correction Model.

In another embodiment, after step 150, a second verification step (step 160) can also be performed, the purpose of which is to verify that the original drawing data is corrected and written on a photomask, and transferred to the photoresist The etchant layer, and after the pattern miniaturization process, whether the formed miniaturized pattern is correct. The above-mentioned second verification step is, for example, using post-OPC verification software to compare the optical proximity effect correction model with the original drawing data to determine whether the plurality of miniaturized patterns preformed on a photoresist layer are correct, and if not If yes, step 140 should be repeated to re-establish an optical proximity effect correction model.

From the above, it can be seen that the present invention can use the existing software package (verify post-OPC software) to verify the reliability and accuracy of the established optical proximity effect correction model. Likewise, this saves the cost of the process.

Please continue to refer to FIG. 1 , step 170 , correct the original drawing data according to the optical proximity effect correction model to obtain a corrected drawing data.

The above-mentioned steps 100-170 can be regarded as a method for correcting the photomask pattern, and then the method for forming the photomask pattern can be continued after step 170 .

Referring to FIG. 1 again, step 180 is to write the corrected drawing data on a photomask. This step is to perform a writing step, writing the corrected drawing data on a photomask to form a pattern on the photomask. Wherein, the above-mentioned writing step includes using electron beams (e-beam) or laser beams (laser beams) to perform it.

In summary, the present invention has at least the following advantages:

1. The present invention corrects the effect produced by the chemical shrinkage process and the optical proximity effect, and establishes an optical proximity effect correction model to correct the photomask pattern, so that the pattern formed on the wafer is more accurate, so the process can be improved reliability and yield.

2. The present invention uses the existing software package, which can avoid complex inferences, and can correct the photomask pattern to obtain the original designed circuit layout pattern, which can save process costs.

Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Those skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention It shall prevail as defined in the appended claims.

Claims (15)

1. A method for correcting a photomask pattern, comprising: providing a test photomask on which a plurality of original patterns have been formed according to an original drawing data; Transferring the original patterns on the test photomask to a first photoresist layer to form a plurality of first developed patterns correspondingly, and measuring a first of each of the first developed patterns a size; performing a pattern miniaturization process on the first developed patterns to form a plurality of first miniaturized patterns correspondingly, and measuring a second size of each of the first miniaturized patterns; calculating a deviation value of each of the first dimensions and each of the corresponding second dimensions, and collecting the original drawing data, the first dimensions, the second dimensions and the deviation values to obtain a database ; using data from the database to create an optical proximity correction model; and The original drawing data is corrected according to the optical proximity correction model to obtain corrected drawing data. 2. The method for calibrating a photomask pattern according to claim 1, further comprising performing a first verification step to verify the optical proximity effect correction model after establishing the optical proximity effect correction model. 3. The method for correcting a photomask pattern as claimed in claim 2, wherein the first verifying step comprises: establishing a verification fitting curve model using the original drawing data and the first dimensions; and comparing the optical proximity correction model with the verification fitting curve model to determine whether the second post-developed patterns pre-formed on a second photoresist layer are correct, and if not, repeating the process of establishing the Steps to modify the model for the optical proximity effect. 4. The method for calibrating a photomask pattern as claimed in claim 2, further comprising performing a second verification step to verify the optical proximity effect correction model after the first verification step. 5. The method for correcting a photomask pattern as claimed in claim 4, wherein the second verifying step comprises comparing the optical proximity correction model with the original drawing data to determine that the preformed photoresist is formed in a second photoresist Whether the plurality of second miniaturized patterns on the layer are correct, if not, repeat the step of establishing the optical proximity effect correction model. 6. The method for correcting photomask patterns according to claim 1, wherein the pattern miniaturization process includes chemical miniaturization process, heat flow process, chemical amplification composition line width process, and double exposure process of Ravenson type phase transfer photomask. 7. The method for correcting a photomask pattern as claimed in claim 1, wherein the original drawing data includes critical dimension, pattern density, and line-to-space ratio. 8. A method for forming a photomask pattern, comprising: forming a plurality of original patterns on a test photomask according to an original drawing data; Transferring the original patterns on the test photomask to a first photoresist layer to form a plurality of first developed patterns correspondingly, and measuring a first of each of the first developed patterns a size; performing a pattern miniaturization process on the first developed patterns to form a plurality of first miniaturized patterns correspondingly, and measuring a second size of each of the first miniaturized patterns; calculating a deviation value of each of the first dimensions and each of the corresponding second dimensions, and collecting the original drawing data, the first dimensions, the second dimensions and the deviation values to obtain a database ; use the data in the database to build an optical proximity correction model; Correcting the original drawing data according to the optical proximity correction model to obtain a corrected drawing data; and A writing step is performed to write the corrected drawing data on a photomask to form a pattern on the photomask. 9. The method for forming a photomask pattern according to claim 8, further comprising performing a first verification step to verify the optical proximity effect correction model after establishing the optical proximity effect correction model. 10. The method for forming a photomask pattern according to claim 9, wherein the first verifying step comprises: establishing a verification fitting curve model using the original drawing data and the first dimensions; and comparing the optical proximity correction model with the verification fitting curve model to determine whether the second post-developed patterns pre-formed on a second photoresist layer are correct, and if not, repeating the process of establishing the Steps to modify the model for the optical proximity effect. 11. The method for forming photomask patterns as claimed in claim 9, further comprising performing a second verification step to verify the optical proximity effect correction model after the first verification step. 12. The method for forming a photomask pattern as claimed in claim 11, wherein the second verifying step comprises comparing the optical proximity correction model with the original drawing data to determine that the pre-formation is in a second photoresist Whether the plurality of second miniaturized patterns on the layer are correct, if not, repeat the step of establishing the optical proximity effect correction model. 13. The method for forming a photomask pattern as claimed in claim 8, wherein the pattern miniaturization process includes a chemical miniaturization process, a heat flow process, a chemical amplification composition line width process, and a Ravenson-type phase transfer photomask double exposure process. 14. The method for forming a photomask pattern as claimed in claim 8, wherein the original drawing data includes critical dimensions, pattern densities, and line-to-space ratios. 15. The method for forming a photomask pattern as claimed in claim 8, wherein the writing step is performed using an electron beam or a laser beam.

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