JP2002353130A - Beam profile measurement method and exposing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring a beam profile for analyzing acid diffusion within a resist, flare, and aberration in an optical system, and to provide an exposing method for accurately correcting proximity effect. SOLUTION: The beam measurement method comprises a process for exposing a plurality patterns onto an exposure surface with a specific interval for measuring the line width of a specific pattern, a process for performing exposure and measuring the line width by changing the pattern interval, a process for calculating the forward scattering and backward scattering in the exposure surface by simulation, a process for obtaining the aberration of an optical system by fitting a simulation result to a measurement result with the aberration of the optical system as a variable, a process for obtaining flares from the deviation between the measurement result and the simulation result, and a process for obtaining acid diffusion by changing process temperature. The exposure method is used to correct the proximity effect, based on the beam provide measurement method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam profile measuring method capable of analyzing a plurality of factors contributing to a beam profile in lithography for manufacturing a semiconductor device and the like, and a proximity effect based on the measured beam profile. The present invention relates to an exposure method capable of correcting with high accuracy.

[0002]

2. Description of the Related Art As LSI design rules have shrunk,
The exposure wavelength in lithography has been shortened. At present, light having a wavelength of 248 nm using a KrF excimer laser as a light source is used for lithography.
In order to cope with future miniaturization, lithography using 193 nm wavelength light using an ArF excimer laser as a light source and 157 nm wavelength using an F ₂ excimer laser as a light source has been put into practical use.

Further, as a lithography technique which can cope with a design rule of 0.1 μm or less, charged particle beam lithography such as electron beam lithography and IPL (Ion Projection Lithography), and E using light having a wavelength of about 13 nm.
UV (Extreme UV) lithography, X-ray lithography, and the like have been proposed.

In these lithography techniques, aberrations in an optical system, beam spread caused by an optical system called flare, scattering of a charged particle beam such as light or an electron beam in a resist, scattering from a substrate, and the like. The beam profile (beam shape) changes depending on various factors.

[0005] When a chemically amplified resist is used, a reaction takes place using an acid generated by light as a catalyst to insolubilize or solubilize a light-irradiated portion. However, the acid generated by light diffuses from the exposed area to the unexposed area in the solid phase, and affects the line width of the resist. Therefore,
Acid diffusion in the chemically amplified resist is also one of the factors that determine the beam profile.

In general, as the design rules are reduced and the patterns are made closer, the deviation between the dimension of the resist pattern formed by lithography and the design dimension increases. This phenomenon is called the proximity effect. To correct the proximity effect, it is indispensable to measure a beam profile including all factors contributing to resist pattern formation.

For example, in electron beam lithography,
As a conventionally proposed beam profile measuring method, there is a method of scanning an edge of a metal mark with an electron beam. According to this method, the aberration of the electron optical system is obtained from the shape of the reflected electron signal from the irradiation position of the electron beam or the shape of the passing electron signal at the irradiation position. There is also known a method for measuring the aberration, forward scattering, and acid diffusion of an electron optical system from the dependence of the pattern size on the exposure amount. Or,
A method of measuring backscattering (area density method) is also known from the difference in the optimum exposure amount when the drawing area ratio is changed.

[0008]

However, according to the above-mentioned conventional beam profile measuring method, only a part of the beam profile can be measured. Further, according to the Monte Carlo simulation, backscattering and forward scattering can be obtained by calculation, but acid diffusion and flare in a resist, aberration of an optical system, and the like cannot be obtained only by simulation.

In the case of photolithography, there is also a method of measuring a light intensity distribution of light transmitted through a mask using a light intensity simulation microscope and predicting a beam profile. The light intensity simulation microscope consists of a light source that irradiates the mask with ultraviolet light, and a CCD that detects the light transmitted through the mask.
(Charge coupled device). However, the light intensity simulation cannot measure, for example, acid diffusion in a resist.

The present invention has been made in view of the above-mentioned problems, and therefore, the present invention separately measures, among factors determining a beam profile, acid diffusion in a resist, flare, and aberration of an optical system. It is an object of the present invention to provide a beam profile measurement method that can be used. Also,
An object of the present invention is to provide an exposure method that can correct a proximity effect with high accuracy in consideration of a plurality of factors affecting a beam profile.

[0011]

In order to achieve the above object, a beam profile measuring method according to the present invention comprises the steps of: forming a plurality of patterns on an exposure surface at predetermined intervals by exposure; Measuring the line width of at least one specific pattern, at least once, forming the plurality of patterns by exposure by changing the interval, and measuring the line width, and changing the interval. Making the change in the measurement result correspond, calculating forward scatter and back scatter of the exposure surface by a first simulation, and using the aberration of the optical system of the exposure light source as a variable, using the first simulation result. Calculating a change in the line width with respect to the change in the interval by performing a second simulation so as to fit the measurement result. And a step of obtaining the aberration when the second simulation result is fitted, and a step of obtaining a beam spread caused by the optical system from a difference between the measurement result and the second simulation result. It is characterized by.

Preferably, the exposed surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment, and the step of performing the exposure and the measurement of the line width includes: And performing the exposure and the measurement of the line width under conditions in which the diffusion is suppressed.

Preferably, the exposed surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment. Performing the exposure and the measurement of the line width under the first condition under which the acid diffuses in the resist, and performing the heat treatment under the second condition under which the diffusion is suppressed. And a step of measuring the line width, wherein the second simulation step is a step of using the measurement result under the second condition, and the measurement result under the first condition, The method further includes a step of obtaining a range and a degree of the acid diffusion from a deviation from the measurement result under the second condition.

Preferably, the heat treatment includes at least one of pre-baking before the exposure and post-exposure baking after the exposure, wherein the pre-baking temperature is higher than the second condition under the first condition. The post exposure baking temperature is higher in the first condition than in the second condition.

Preferably, the step of forming the pattern includes a step of scanning the exposure surface with an electromagnetic wave or a charged particle beam. More preferably, the charged particle beam includes an electron beam. Alternatively, the step of forming the pattern includes:
A step of performing exposure by an electromagnetic wave or a charged particle beam through a mask having the pattern, and transferring the pattern to the exposed surface.

Preferably, in the step of forming the plurality of patterns by exposure while changing the interval, the exposure amount is kept constant without changing. Preferably, the specific pattern is:
The central pattern or the pattern closest to the center among the plurality of patterns. Preferably, the line width of the specific pattern is an average value of the line widths of a plurality of patterns. Preferably, the pattern includes a linear pattern.

As a result, not only the backscattering and forward scattering which could be calculated conventionally, but also the aberration of the electron optical system,
It is possible to grasp the degree and range of the flare, and the degree and range of the acid diffusion in the chemically amplified resist. As described above, back scattering, forward scattering, electron optical system aberration, acid diffusion, and flare, which are factors that determine the beam profile, are individually determined, so that the beam profile contributing to resist pattern formation can be more accurately grasped. It is possible to do. Therefore, the proximity effect correction can be performed with high accuracy.

In order to achieve the above object, a beam profile measuring method according to the present invention includes a step of forming a plurality of patterns on an exposure surface at predetermined intervals by exposure, and a step of forming at least one of the patterns. A step of measuring a line width difference between one specific pattern and another at least one second specific pattern, and forming the plurality of patterns by exposure at least once by changing the interval; A step of measuring a line width difference, a step of associating a change in the interval with a change in the measurement result, a step of calculating forward scattering and back scattering of the exposure surface by a first simulation, and an optical system of an exposure light source Is used as a variable, a second simulation is performed using the first simulation result to fit the measurement result, and the Calculating the change in the line width difference; obtaining the aberration when the measurement result and the second simulation result are fitted; and calculating a difference between the measurement result and the second simulation result. Obtaining a spread of the beam caused by the optical system.

Preferably, the exposed surface includes a resist in which an acid is generated and diffused by the exposure and the diffusion is suppressed by a heat treatment, and the step of performing the exposure and the measurement of the line width difference includes: Performing a heat treatment to measure the exposure and the line width difference under the condition that the diffusion is suppressed.

Preferably, the exposed surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment, and the step of performing the exposure and measuring the line width difference includes: A step of performing the exposure and the measurement of the line width difference under the first condition in which the acid diffuses in the resist without performing the heat treatment, and performing the heat treatment under the second condition in which the diffusion is suppressed, Performing the exposure and measuring the line width difference, wherein the second simulation step is a step of using the measurement result under the second condition, and the measurement result under the first condition is used. And determining a range and a degree of the acid diffusion from a deviation from the measurement result under the second condition.

Preferably, the heat treatment includes at least one of pre-baking before the exposure and post-exposure baking after the exposure, wherein the pre-baking temperature is higher than the second condition under the first condition. The post exposure baking temperature is higher in the first condition than in the second condition.

Preferably, the step of forming the pattern includes a step of scanning the exposure surface with an electromagnetic wave or a charged particle beam. More preferably, the charged particle beam includes an electron beam. Preferably, the step of forming the pattern includes:
A step of performing exposure by an electromagnetic wave or a charged particle beam through a mask having the pattern, and transferring the pattern to the exposed surface.

Preferably, in the step of forming the plurality of patterns by exposure while changing the interval, the exposure amount is kept constant without being changed. Preferably, the first specific pattern is a center pattern or a pattern closest to the center among the plurality of patterns. Preferably, the second
The line width of the specific pattern is an average value of the line widths of the patterns at both ends of the plurality of patterns. Alternatively, the second specific pattern is a pattern at one end of the plurality of patterns. Preferably, at least one of the line width of the first specific pattern and the line width of the second specific pattern is an average value of the line widths of the plurality of patterns. Preferably,
The pattern includes a linear pattern.

As a result, not only the backscattering and forward scattering which could be calculated conventionally, but also the aberration of the electron optical system,
It is possible to grasp the degree and range of the flare, and the degree and range of the acid diffusion in the chemically amplified resist. As described above, back scattering, forward scattering, electron optical system aberration, acid diffusion, and flare, which are factors that determine the beam profile, are individually determined, so that the beam profile contributing to resist pattern formation can be more accurately grasped. It is possible to do. Therefore, the proximity effect correction can be performed with high accuracy.

In order to achieve the above object, an exposure method of the present invention comprises a step of forming a plurality of patterns on an exposure surface at predetermined intervals by exposure, and a step of forming a specific pattern which is at least one of the patterns A step of measuring a line width, at least once, changing the interval, forming the plurality of patterns by exposure, and measuring the line width, and associating the change in the interval with the change in the measurement result. Process and
Calculating the forward scattering and back scattering of the exposure surface by a first simulation, and using the aberration of the optical system of the exposure light source as a variable, using the first simulation result,
Performing a second simulation to fit the measurement result and calculating a change in the line width with respect to the change in the interval; and obtaining the aberration when the measurement result and the second simulation result are fitted. A step of obtaining a beam spread caused by the optical system from a difference between the measurement result and the second simulation result; and correcting a part of the pattern using the aberration and the beam spread. The method further includes a step of adding and a step of forming the corrected pattern by exposure on another exposure surface equivalent to the exposure surface.

Preferably, the exposed surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment. Performing the exposure and the measurement of the line width under the first condition under which the acid diffuses in the resist, and performing the heat treatment under the second condition under which the diffusion is suppressed. And a step of measuring the line width, wherein the second simulation step is a step of using the measurement result under the second condition, and the measurement result under the first condition, A step of obtaining the range and degree of the acid diffusion from a deviation from the measurement result under the second condition, wherein the step of correcting the part of the pattern uses the range and the degree of the acid diffusion .

Thus, specific factors can be examined in detail based on the beam profile including all the factors contributing to pattern formation. Therefore, the proximity effect correction can be performed more accurately. ADVANTAGE OF THE INVENTION According to the exposure method of this invention, even if a pattern is miniaturized and the pattern space | interval is close, the deviation | shift between the dimension of the pattern transferred by exposure and a design dimension can be made small.

In order to achieve the above object, an exposure method according to the present invention comprises a step of forming a plurality of patterns on an exposure surface at predetermined intervals by exposure, and a first step of forming at least one of the patterns. A step of measuring a line width difference between the specific pattern and another at least one second specific pattern; and forming the plurality of patterns by exposure at least once by changing the distance, Measuring the difference; correlating the change in the interval with the change in the measurement result; calculating the forward scattering and back scattering of the exposure surface by a first simulation; and the aberration of the optical system of the exposure light source. Is used as a variable, and the second simulation is performed using the first simulation result to fit the measurement result.
Performing a simulation of, and calculating the change in the line width difference with respect to the change in the interval; obtaining the aberration when the measurement result and the second simulation result are fitted; Obtaining a spread of a beam caused by the optical system from a deviation from the simulation result of Step 2, a step of correcting a part of the pattern using the aberration and the spread of the beam, Forming the corrected pattern by exposure on another exposure surface.

Preferably, the exposed surface includes a resist in which an acid is generated and diffused by the exposure and the diffusion is suppressed by a heat treatment, and the step of performing the exposure and the measurement of the line width difference includes: A step of performing the exposure and the measurement of the line width difference under the first condition in which the acid diffuses in the resist without performing the heat treatment, and performing the heat treatment under the second condition in which the diffusion is suppressed, Performing the exposure and measuring the line width difference, wherein the second simulation step is a step of using the measurement result under the second condition, and the measurement result under the first condition is used. And, from the deviation from the measurement result under the second condition, further comprising a step of obtaining the range and degree of the acid diffusion, wherein in the step of correcting a part of the pattern, the range of the acid diffusion and Use degree.

Thus, specific factors can be examined in detail based on the beam profile including all factors contributing to pattern formation. Therefore, the proximity effect correction can be performed more accurately. ADVANTAGE OF THE INVENTION According to the exposure method of this invention, even if a pattern is miniaturized and the pattern space | interval is close, the deviation | shift between the dimension of the pattern transferred by exposure and a design dimension can be made small.

[0031]

Embodiments of a beam profile measuring method and an exposure method according to the present invention will be described below with reference to the drawings. (Embodiment 1) This embodiment shows a beam profile measuring method in electron beam lithography.

Specifically, a beam profile of a variable-shaped electron beam direct writing machine HL-800D (manufactured by Hitachi, Ltd.) having an acceleration voltage of 50 kV was measured, and based on the measurement results and the simulation results, acid diffusion in the resist was determined. Analyze flare and aberrations of the electron optics.

In the present embodiment, a plurality of line patterns are drawn on the resist, and each factor of the beam profile is measured from the change in the line width of the center line when the pattern interval is changed. Here, the center line does not necessarily have to be at a position equidistant from the line patterns at both ends, and may be near the center of the line patterns at both ends. Alternatively, the average of the line widths of about two line patterns near the center may be used as the line width of the center line.

The process will be described in order from the resist coating step. First, a chemically amplified negative resist NEB31 (manufactured by Sumitomo Chemical Co., Ltd.) is applied to a quartz substrate, for example, with a thickness of 250 nm by a spin coat method. Next, pre-baking (PB) is performed, for example, at a temperature of 100 ° C. or 12 ° C.
Perform at 0 ° C. for 120 seconds.

Next, by using HL-800D, a line having a design dimension of 100 nm in line width and 5 μm in length is, for example, 3 lines.
The book is drawn at a predetermined pattern interval. At this time, the exposure amount is fixed at, for example, 20 μC / cm ^2, and the pattern interval is changed. FIG. 1 shows scanning electron microscope (SEM) photographs of the drawn three lines.

In this embodiment, the pattern interval is set to 5
Although it was changed in the range of 0 nm to 2 μm, the pattern interval was set to, for example, 50 nm to 2 μm depending on the behavior of the beam profile.
It may be changed in a range of about 20 μm. Further, it is sufficient that at least two line patterns are provided. However, if the number of line patterns is increased and the drawing area ratio is increased while the exposure amount is kept constant, the contribution of backscattering to the beam profile increases. Therefore, the upper limit of the number of line patterns is appropriately determined within a range in which the backscatter does not increase,
For example, the number is about nine.

Thereafter, post-exposure baking (PEB;
post exposure baking) at 90 ° C or 80 ° C
C. for 120 seconds and then tetramethylammonium hydroxide (TMAH; tetramethylammonium hydrox
Developing with a solution containing 2.38% of ide) for 60 seconds.

Under normal process conditions, PB is 100 ° C.
Perform PEB at 90 ° C. In this case, the acid diffusion in the resist occurs as described above. As the temperature of PB increases, the free volume in the resist decreases, and the diffusion of acid is suppressed. Further, the lower the temperature of PEB, the more the thermal diffusion of acid in the resist is suppressed. Therefore, when suppressing the diffusion of acid, PB was performed at 120 ° C. and PEB was performed at 80 ° C.

FIG. 2 shows the relationship between the line width increase of the central line of the three lines and the pattern interval. The solid line shows the calculation result when the beam profile of the electron optical system is calculated as a Gaussian function with an aberration σ of 60 nm. In this calculation, the acceleration voltage is 50 kV, the resist film thickness is 250 nm.
And the result of Monte Carlo simulation for
A Gaussian function of 60 nm is superposed and integrated in a range of three lines with a design line width of 100 nm.

The forward scattering and the back scattering are calculated by Monte Carlo simulation, and the subsequent calculation takes into account the aberration of the electron optical system. The backscattering and the forward scattering can be calculated by performing Monte Carlo simulation according to the related art. Alternatively, for example, backscattering may be measured by the area density method described above, and the measurement result may be used for correcting the calculation result of the backscattering.

In FIG. 2, black circles (●) show the experimental results under normal process conditions, and open circles (○) show the experimental results under process conditions that can suppress acid diffusion. By comparing the solid line (calculated result) with the experimental result, it is possible to examine a specific factor among the factors of the beam profile other than the forward scattering, the back scattering, and the aberration of the electron optical system. Specifically, it is possible to analyze the acid diffusion in the resist and the spread (flare) of the beam caused by the electron optical system.

A method of analyzing each factor of the beam profile will be described below. Regarding the acid diffusion in the resist, the usual process conditions for acid diffusion (PB temperature 100
At the PEB temperature of 90 ° C.) and the process conditions (PB temperature 120
At 80 ° C. and a PEB temperature of 80 ° C.).

As shown in FIG. 2, the pattern interval is 500
When the width is smaller than about nm, the amount of increase in line width under normal process conditions is larger than the amount of increase in line width under process conditions that can suppress acid diffusion. Pattern interval is 500n
If m is exceeded, there is no difference between the line width increase amount under normal process conditions and the line width increase amount under process conditions where acid diffusion can be suppressed.

From this, it can be seen that under the above-described ordinary process conditions, acid is diffused from the exposed region to the unexposed region by about 500 nm, and the beam profile is affected by the acid diffusion in this range. Also, a pattern interval of 500 n
Even within the range of m or less, the smaller the pattern interval, the greater the difference between the experimental results between the normal process conditions and the process conditions that can suppress acid diffusion. From this, it is also understood that the influence of the acid diffusion rapidly increases as approaching the exposed region.

Regarding the flare, the amount of increase in the line width under the process conditions that can suppress the acid diffusion will be compared with the calculation result. As shown in FIG. 2, the pattern interval is 150 to 9
In the range of about 00 nm, the increase in the line width under the process conditions that can suppress the acid diffusion is larger than the calculation result.
From this, it can be seen that when the pattern interval is 150 to 900 nm, the flare increases.

The aberration of the electron optical system is optimized by inputting the amount of aberration σ as a variable at the time of calculation. For example,
A Monte Carlo simulation is performed using the beam profile as a Gaussian function of the aberration σ. Alternatively, the beam profile of the electron optical system may be superimposed on the result of the Monte Carlo simulation as an arbitrary function.

For example, in a region where the line width of the center line is sharply increased and the pattern interval is 150 nm or less, the calculation result of the simulation shows that the line width increase under the process conditions (PB temperature 120 ° C., PEB temperature 80 ° C.) which can suppress the acid diffusion Fit with quantity. In the present embodiment, the aberration σ = 60
In the case of nm (see FIG. 2), the best fit was obtained between the calculation result of the Monte Carlo simulation and the increase in the line width under the process conditions capable of suppressing the acid diffusion. The value of the aberration is obtained from such fitting.

According to the beam profile measuring method of the embodiment of the present invention, it is possible to grasp not only the backscatter and the forward scattering which can be calculated, but also the aberration of the electron optical system and the degree and range of the flare. Become. Further, it becomes possible to grasp the extent and range of acid diffusion from the exposed region to the unexposed region in the chemically amplified resist.

As described above, since the back scattering, forward scattering, aberration of the electron optical system, acid diffusion and flare which are factors determining the beam profile are individually obtained,
It is possible to more accurately grasp the beam profile that contributes to the formation of the resist pattern. Therefore, it is possible to perform the proximity effect correction with high accuracy and reduce the deviation between the dimension of the resist pattern and the design dimension.

The exposure method according to the present embodiment performs proximity effect correction on a mask pattern based on the beam profile obtained by the above-described beam profile measurement method according to the present embodiment, and uses the corrected mask to perform variable shaping. Electron beam direct writing is performed.

According to the exposure method of the present embodiment, a beam profile including all factors contributing to pattern formation is measured, and specific factors are examined in detail based on the measured beam profile. Effect correction can be performed more accurately. Therefore, even when the pattern is miniaturized and the pattern interval is close, the deviation between the dimension of the resist pattern and the design dimension can be reduced.

(Embodiment 2) This embodiment corresponds to Embodiment 1.
Similarly to the above, a method for measuring a beam profile in electron beam lithography using HL-800D will be described. Patterns are formed under the above normal process conditions and under the process conditions that can suppress acid diffusion, and beam profiles are measured, respectively.According to the measurement results and simulation results, acid diffusion in the resist, flare, and aberration of the electron optical system To analyze. The simulation can be performed in the same manner as in the first embodiment.

In this embodiment, a plurality of line patterns are drawn on the resist, and each factor of the beam profile is measured from a change in the line width difference between the center line and both end lines when the pattern interval is changed. Here, it is desirable that the line width of both end lines is an average of the line widths of both end lines. However, in order to simplify the measurement of the line width, the line width of one end line can be substituted. Further, the center line does not necessarily have to be at a position equidistant from the line patterns at both ends, and may be near the center of the line patterns at both ends.
Alternatively, the average of the line widths of about two line patterns near the center may be used as the line width of the center line.

The resist coating step, PB step, exposure step, and PEB step are performed in the same manner as in the first embodiment.
For example, three line patterns are formed. The exposure amount is fixed at, for example, 20 μC / cm ^2, and the pattern interval is changed in a range of, for example, 50 nm to 2 μm. However, regarding the pattern interval and the number of line patterns, the first embodiment
Similarly to the above, the influence of the backscatter can be arbitrarily changed within a negligible range.

As in FIG. 2, the line width difference between the center line and both end lines is plotted against the pattern interval. Above a specific pattern interval, the line width difference under normal process conditions matches the line width difference under process conditions that can suppress acid diffusion. The line width difference under the normal process condition becomes larger than the line width difference under the process condition in which the acid diffusion can be suppressed within the specific pattern interval or less, that is, within the range in which the influence of the acid diffusion occurs.

The smaller the pattern interval, the greater the difference between the experimental results between the normal process conditions and the process conditions that can suppress acid diffusion. As described above, according to the present embodiment, similarly to the first embodiment, the range and the degree of the acid diffusion can be analyzed, and the influence of the acid diffusion on the beam profile can be grasped.

The flare will be examined by comparing the line width difference under the process conditions capable of suppressing acid diffusion with the calculation result. As in FIG. 2, when the pattern interval is within a specific range, the line width difference under the process conditions that can suppress the acid diffusion is larger than the calculation result. It can be seen that the flare increases within such a range of the pattern interval.

The aberration of the electron optical system is optimized by inputting the amount of aberration σ as a variable at the time of calculation. For example,
A Monte Carlo simulation is performed using the beam profile as a Gaussian function of the aberration σ. Alternatively, the beam profile of the electron optical system may be superimposed on the result of the Monte Carlo simulation as an arbitrary function.

For example, in a region (near an exposure region) below a specific pattern interval where the line width difference between the center line and both end lines sharply increases, the simulation calculation result is compared with the line width difference under the process conditions that can suppress acid diffusion. Fit.
The aberration σ when the calculation result of the Monte Carlo simulation and the line width difference under the process conditions that can suppress the acid diffusion are best fitted is the aberration of the electron optical system.

According to the beam profile measuring method of the embodiment of the present invention described above, it is possible to grasp not only the backscatter and the forward scattering which can be calculated, but also the aberration of the electron optical system and the degree and range of the flare. Become. Further, it becomes possible to grasp the extent and range of acid diffusion from the exposed region to the unexposed region in the chemically amplified resist.

As described above, the back scattering, forward scattering, aberration of the electron optical system, acid diffusion, and flare, which are factors that determine the beam profile, are individually determined.
It is possible to more accurately grasp the beam profile that contributes to the formation of the resist pattern. Therefore, it is possible to perform the proximity effect correction with high accuracy and reduce the deviation between the dimension of the resist pattern and the design dimension.

The exposure method according to the present embodiment performs a proximity effect correction on a mask pattern based on the beam profile obtained by the beam profile measuring method according to the above-described embodiment, and uses a corrected mask to perform variable shaping. Electron beam direct writing is performed.

According to the exposure method of the present embodiment, a beam profile including all factors contributing to pattern formation is measured, and specific factors are examined in detail based on the measured beam profile. Effect correction can be performed more accurately. Therefore, even when the pattern is miniaturized and the pattern interval is close, the deviation between the dimension of the resist pattern and the design dimension can be reduced.

Embodiments of the beam profile measuring method and the exposure method of the present invention are not limited to the above description.
For example, lithography other than electron beam lithography,
For example, the present invention can be applied to measurement of a beam profile in IPL, EUV lithography, X-ray lithography, or the like.

However, when the present invention is applied to lithography other than the electron beam direct writing of the above embodiment, it is necessary to produce a plurality of masks having different pattern intervals.
On the other hand, in the above embodiment, a plurality of masks having different pattern intervals are unnecessary, and the beam profile can be measured relatively easily. In addition, various changes can be made without departing from the gist of the present invention.

[0066]

According to the beam profile measuring method of the present invention, among the factors determining the beam profile, acid diffusion in the resist, flare, and aberration of the optical system can be individually analyzed. Further, according to the exposure method of the present invention, it becomes possible to correct the proximity effect with high accuracy in consideration of a plurality of factors affecting the beam profile.

[Brief description of the drawings]

FIG. 1 is an SEM photograph of a line pattern according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a pattern interval and a line width increase amount of a center line according to the first embodiment of the present invention, with respect to a calculation result and an experimental result.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 541M

Claims (28)

[Claims] A plurality of patterns formed on an exposure surface at predetermined intervals;
Forming by exposure, and measuring a line width of a specific pattern that is at least one of the patterns, at least once, changing the interval, forming the plurality of patterns by exposure, the line A step of measuring a width; a step of associating a change in the interval with a change in the measurement result; a step of calculating forward scattering and back scattering of the exposure surface by a first simulation; and aberrations of an optical system of the exposure light source. Using the first simulation result as a variable, performing a second simulation to fit the measurement result, and calculating a change in the line width with respect to a change in the interval; Obtaining the aberration when the second simulation result is fitted; and calculating the second simulation result and the second simulation result. Obtaining a beam divergence caused by the optical system from a deviation from the result. 2. The method according to claim 1, wherein the exposed surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment. The step of performing the exposure and measuring the line width includes performing the heat treatment. 2. The beam profile measuring method according to claim 1, further comprising the step of: performing the exposure and the measurement of the line width under conditions where the diffusion is suppressed. 3. The exposure surface includes a resist in which an acid is generated and diffused by exposure to light, and the diffusion is suppressed by a heat treatment. The step of performing the exposure and the measurement of the line width includes performing the heat treatment. A step of performing the exposure and the measurement of the line width under a first condition under which an acid is diffused in the resist; and performing the heat treatment under a second condition in which the diffusion is suppressed. Measuring the line width, the second simulation step is a step of using the measurement result under the second condition, and the measurement result under the first condition and the second simulation step are performed. 2. The beam profile measurement method according to claim 1, further comprising a step of obtaining a range and a degree of the acid diffusion from a deviation from the measurement result under the following condition. 4. The heat treatment includes at least one of pre-baking before the exposure and post-exposure baking after the exposure, wherein the pre-baking temperature is the second temperature under the first condition.
4. The beam profile measuring method according to claim 3, wherein the post exposure baking temperature is higher than the second condition under the first condition. 5. The beam profile measuring method according to claim 1, wherein the step of forming the pattern includes a step of scanning the exposure surface with an electromagnetic wave or a charged particle beam. 6. The beam profile measuring method according to claim 5, wherein said charged particle beam includes an electron beam. 7. The beam profile according to claim 1, wherein the step of forming the pattern includes a step of performing exposure with an electromagnetic wave or a charged particle beam through a mask having the pattern, and transferring the pattern to the exposed surface. Measuring method. 8. The beam profile measuring method according to claim 1, wherein, in the step of forming the plurality of patterns by exposure while changing the interval, the exposure amount is kept constant without being changed. 9. The beam profile measuring method according to claim 1, wherein the specific pattern is a central pattern or a pattern closest to the center among the plurality of patterns. 10. The beam profile measuring method according to claim 1, wherein the line width of the specific pattern is an average value of the line widths of a plurality of patterns. 11. The beam profile measuring method according to claim 1, wherein said pattern includes a linear pattern. 12. A step of forming a plurality of patterns on an exposed surface at predetermined intervals by exposure, a first specific pattern that is at least one of the patterns, and a second specific pattern that is at least one of the other. Measuring the line width difference with the specific pattern, at least once, forming the plurality of patterns by exposure while changing the interval, and measuring the line width difference; and A step of corresponding to a change in the measurement result; a step of calculating forward scatter and a back scatter of the exposure surface by a first simulation; and using the aberration of the optical system of the exposure light source as a variable, and using the first simulation result. Performing a second simulation so as to fit with the measurement result, and calculating a change in the line width difference with respect to the change in the interval; A step of determining the aberration when simulation results were fitted, the deviation between the measurement result and the second simulation result, the beam profile measuring method having a step of determining the spread of the beam due to the optical system. 13. The step of performing the exposure and the measurement of the line width difference, wherein the exposed surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment. 13. The beam profile measuring method according to claim 12, further comprising a step of performing the exposure and the measurement of the line width difference under a condition where the diffusion is suppressed. 14. The exposure surface includes a resist in which an acid is generated and diffused by the exposure, and the diffusion is suppressed by a heat treatment. Performing the exposure and the measurement of the line width difference under the first condition in which the acid diffuses in the resist, and performing the exposure under the second condition in which the heat treatment is performed and the diffusion is suppressed. And a step of measuring the line width difference, wherein the second simulation step is a step using the measurement result under the second condition, and the measurement result under the first condition, 13. The beam profile measuring method according to claim 12, further comprising a step of obtaining a range and a degree of the acid diffusion from a deviation from the measurement result under the second condition. 15. The heat treatment includes at least one of pre-baking before the exposure and post-exposure baking after the exposure, wherein the pre-baking temperature is the second temperature under the first condition.
The beam profile measurement method according to claim 14, wherein the post-exposure baking temperature is lower than the first condition and the second condition is higher than the second condition under the first condition. 16. The beam profile measuring method according to claim 12, wherein the step of forming the pattern includes a step of scanning the exposure surface with an electromagnetic wave or a charged particle beam. 17. The beam profile measuring method according to claim 16, wherein said charged particle beam includes an electron beam. 18. The beam profile according to claim 12, wherein the step of forming the pattern includes a step of performing exposure with an electromagnetic wave or a charged particle beam through a mask having the pattern, and transferring the pattern to the exposed surface. Measuring method. 19. The beam profile measuring method according to claim 12, wherein in the step of changing the interval to form the plurality of patterns by exposure, the exposure amount is fixed without changing. 20. The beam profile measuring method according to claim 12, wherein the first specific pattern is a center pattern or a pattern closest to the center among the plurality of patterns. 21. The beam profile measuring method according to claim 12, wherein the line width of the second specific pattern is an average value of line widths of both end patterns of the plurality of patterns. 22. The beam profile measuring method according to claim 12, wherein said second specific pattern is one of the plurality of patterns. 23. The beam profile measuring method according to claim 12, wherein at least one of the line width of the first specific pattern and the line width of the second specific pattern is an average value of the line widths of a plurality of patterns. 24. The beam profile measuring method according to claim 12, wherein said pattern includes a line pattern. 25. A step of forming a plurality of patterns on an exposure surface at predetermined intervals by exposure, and a step of measuring a line width of a specific pattern which is at least one of the patterns; Forming a plurality of patterns by exposure by changing an interval, measuring the line width, causing the change in the interval to correspond to the change in the measurement result, and the forward scattering and the back scattering of the exposed surface. Calculating by a first simulation, performing a second simulation using the aberration of the optical system of the exposure light source as a variable, and using the first simulation result to fit the measurement result, Calculating the change in the line width with respect to, and determining the aberration when the measurement result and the second simulation result are fitted. A step of obtaining a beam spread caused by the optical system from a difference between the measurement result and the second simulation result; and correcting a part of the pattern using the aberration and the beam spread. An exposure method, comprising: adding, and forming the corrected pattern by exposure on another exposure surface equivalent to the exposure surface. 26. The exposure surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment. The step of performing the exposure and the measurement of the line width includes performing the heat treatment. A step of performing the exposure and the measurement of the line width under a first condition in which an acid diffuses in the resist; Measuring the line width, the second simulation step is a step of using the measurement result under the second condition, and the measurement result under the first condition and the second simulation step are performed. Further comprising a step of obtaining a range and a degree of the acid diffusion from a deviation from the measurement result under the condition of (1), wherein the range and the degree of the acid diffusion are used in the step of correcting a part of the pattern. 25 notes Exposure method. 27. A step of forming a plurality of patterns on an exposed surface at predetermined intervals by exposure, a first specific pattern which is at least one of the patterns, and a second specific pattern which is at least one of the other. Measuring the line width difference with the specific pattern, at least once, forming the plurality of patterns by exposure while changing the interval, and measuring the line width difference; and A step of associating a change in the measurement result, a step of calculating forward scattering and back scattering of the exposure surface by a first simulation, and using the aberration of the optical system of the exposure light source as a variable and Performing a second simulation so as to fit with the measurement result, and calculating a change in the line width difference with respect to the change in the interval; A step of obtaining the aberration when the simulation result is fitted; a step of obtaining a spread of a beam caused by the optical system from a difference between the measurement result and the second simulation result; and An exposure method comprising: correcting a part of the pattern by using spread; and forming the corrected pattern by exposure on another exposure surface equivalent to the exposure surface. 28. The method according to claim 28, wherein the exposed surface includes a resist that generates and diffuses an acid upon exposure and suppresses the diffusion by a heat treatment. The step of performing the exposure and the measurement of the line width difference includes performing the heat treatment. Performing the exposure and the measurement of the line width difference under the first condition in which the acid diffuses in the resist, and performing the exposure under the second condition in which the heat treatment is performed and the diffusion is suppressed. And a step of measuring the line width difference, wherein the second simulation step is a step using the measurement result under the second condition, and the measurement result under the first condition, A step of obtaining a range and a degree of the acid diffusion from a deviation from the measurement result under the second condition, wherein in the step of correcting a part of the pattern, the range and the degree of the acid diffusion are determined. Claims used The exposure method of 7, wherein.