JPH11224642A - Electron beam exposure apparatus and electron beam exposure method - Google Patents

Abstract

(57) Abstract: An electron beam exposure apparatus having a means for detecting blur of an electron beam, wherein the size of the blur of the electron beam is quantified without being affected by the shaping shape of the electron beam, and the refocus coefficient is determined. To decide. A measured charge intensity distribution acquisition unit (43) for measuring a reflection amount of an electron beam irradiated on a sample to acquire a first waveform of a first charge intensity distribution on a sample (2), and a shaping unit (2).
A charge intensity distribution calculating means 53 for calculating a second waveform of a theoretical charge intensity distribution using blur as a parameter based on the shape data of the transmission region of 0, and comparing the first waveform with the second waveform to calculate the second waveform. A blur value defining means 55 for defining the magnitude of the blur that minimizes the difference between the first waveform and the second waveform as the actual blur value applied to the sample 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam exposure method and an electron beam exposure apparatus, and more particularly, to an electron beam exposure apparatus having means for detecting blur of an electron beam.

[0002]

2. Description of the Related Art The manufacture of a semiconductor device involves a film forming step and a film patterning step. Patterning of a film is performed by etching the film using a resist pattern as a mask. The formation of the resist pattern is obtained by exposing and further developing the resist applied on the film, and there is an electron beam exposure apparatus as one of the exposure apparatuses for exposing the resist.

An electron beam exposure apparatus has a structure in which an electron beam emitted from an electron gun is irradiated on a resist on a substrate through a plurality of electron lenses, electron beam shapers, deflectors, and the like. In order to shape the electron beam, a variable shaping slit having a rectangular transmission hole, a block mask, or the like is used. However, the electron beam is blurred on the resist due to electron interaction due to lens aberration and Coulomb force, which causes problems such as spreading of the pattern and deterioration of pattern accuracy. Investigations have been made in advance on the degree of beam blurring by the following method.

[0004] The blurring of the electron beam is performed by irradiating a sample with an electron beam shaped into a rectangular shape by a variable shaping slit through an electron lens, scanning the sample on the sample, and measuring a change in the amount of reflection of electrons from the sample. It is required by things. For example, as shown in FIG. 9, a metal film 102 such as tantalum or tungsten is formed on a silicon substrate 101, a window 103 is formed in the metal film 102, and the window 103 is formed.
The structure is such that the surface of the silicon substrate 101 is exposed from the substrate.

Then, the sample is irradiated with an electron beam,
The electron beam is scanned over the sample so as to pass through the electron beam 3, the reflected amount of the electron beam is measured by the backscattered electron detector 104, and the amount of change in the reflected amount is obtained. ) Obtain the intensity electron distribution. And
In the tail portion on both sides of the waveform of the electron irradiation intensity distribution in FIG. 10, a region of 90% to 10% with respect to the peak value is defined as the blur value of the electron beam.

[0006]

However, such definition of the blur value of the electron beam is appropriate when irradiating a sample with a rectangular shaped electron beam, but it is appropriate to define the blur value of the electron beam in a shape other than the rectangular shape. The shaping of the electron beam is not appropriate because the blur value of the electron beam greatly differs from the actual blur of the electron beam.

For this reason, for an electron beam shaped into a shape other than a rectangle, it becomes impossible to determine the blur value of the electron beam necessary for refocusing to reduce the influence of the Coulomb effect. SUMMARY OF THE INVENTION An object of the present invention is to provide an electron beam exposure apparatus capable of quantifying the size of an electron beam blur and determining a refocusing coefficient without being affected by the shape of the electron beam shaping.

[0008]

Means for Solving the Problems The above-mentioned problems are shown in FIG.
As illustrated in FIG. 4, an electron beam generating means 10 for emitting an electron beam toward a sample W (2), a shaping means 20 having a transmission region for shaping the electron beam,
Converging means 32 for converging the electron beam transmitted through the shaping means 20 on the surface of the sample W (2); focus adjusting means 28 for adjusting the focus of the electron beam converged by the converging means 32; A measured electron irradiation intensity distribution acquisition unit 43 for measuring a reflection amount of the electron beam irradiated on the sample and acquiring a first waveform of a first electron irradiation intensity distribution on the sample W (2); An electron irradiation intensity distribution calculating unit 53 for calculating a second waveform of a theoretical electron irradiation intensity distribution using blur as a parameter based on the shape data of the transmission region of the shaping unit 20; By comparing the second waveform, the magnitude of the blur at which the difference between the first waveform and the second waveform becomes a predetermined magnitude is determined by the actual size of the electron beam irradiated onto the sample W (2). Define as bokeh value Having a Ke value definition means 55 be solved by an electron beam exposure apparatus according to claim.

In the above electron beam exposure apparatus, a difference between the first waveform and the second waveform is obtained by a least square method. In the above-described electron beam exposure apparatus, the predetermined magnitude of the difference between the first waveform and the second waveform is a minimum value. In the above-mentioned electron beam exposure apparatus, by changing the focus by the focus adjusting means 28, a plurality of the blur values are obtained, and a proper focus value obtaining means 56 for obtaining an appropriate focus value in which the blur value is minimum, Focus data storage means 57 for storing the data of the proper focus value acquired by the proper focus acquisition means 56, and focus control for controlling the focus of the focus adjustment means 28 based on the data in the focus data storage means 57 And means 40.

In the above-described electron beam exposure apparatus, the focus adjusting means 28 is an electromagnetic lens or a refocus coil. In the above-described electron beam exposure apparatus, the sample 2 has a step, and the measured electron irradiation intensity distribution obtaining unit 43 detects reflected electron of the electron beam that scans the step of the sample 2. 6 and a calculating means 42 for calculating an electron irradiation intensity distribution based on a change in the amount of the reflected electrons detected by the reflected electron detecting means 6 and 41.

In the above-mentioned electron beam exposure apparatus, as shown in FIG. 8, the sample 2 has reflection areas 61 and 62 of fine linear or fine dots, and the measured electron irradiation intensity distribution obtaining means 43 The reflection areas 61 and 6 of the sample 2
And a backscattered electron detecting means for detecting backscattered electrons of the electron beam for scanning the second electron beam.

In the above-described electron beam exposure apparatus, the electron irradiation intensity distribution calculating means 53 integrates the two-dimensional Gaussian distribution function over the transmission area of the shaping means to thereby calculate the second electron irradiation intensity distribution. It has a calculating means for calculating. Note that the extent of the two-dimensional Gaussian distribution function in an arbitrary axis direction may be different from the extent of the two-dimensional Gaussian distribution function in an axial direction orthogonal thereto.

[0013] The above object is achieved by shaping an electron beam emitted toward a sample through a transmission area, and then adjusting the electron beam transmitted through the shaping means by a focus adjusting means to converge on the surface of the sample. Then, a first waveform of a first electron irradiation intensity distribution on the sample is obtained by actually measuring an electron reflection amount of the electron beam reflected from the sample, and the shape data of the transmission area of the shaping unit is obtained. And calculating a second waveform of a theoretical electron irradiation intensity distribution using blur as a parameter, comparing the first waveform with the second waveform, and comparing the first waveform with the second waveform. Is defined as an actual blur value illuminated on the sample, the electron beam exposure method comprising:

Next, the operation of the present invention will be described. According to the present invention, a first waveform of an electron irradiation intensity distribution on a sample based on actual measurement and a second waveform of a theoretical electron irradiation intensity distribution are obtained, and a first waveform and a second waveform are respectively obtained. Are compared to determine the magnitude of the blur in the theoretical electron irradiation intensity distribution such that the difference becomes a predetermined magnitude, and the magnitude of the blur is defined as the actually measured blur value of the electron beam.

For this reason, it is not limited to the case where the shaped shape of the electron beam is rectangular, and the definition of blur according to the shaped shape can be made the same, and the blur value in the electron beam exposure apparatus can be quantified. Accordingly, the blur value can be accurately measured for an arbitrary electron beam shape in exposure. In addition, if the focus is corrected so that the blur value is minimized and the correction dose for the proximity effect is determined, a fine pattern can be formed with high accuracy.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. 1 to 7 show an electron beam exposure apparatus according to a first embodiment of the present invention.
The exposure column system shown in FIG. 1 has an electron beam generation source 10 for irradiating electrons to a wafer W mounted on a movable wafer stage 1, and the electron beam generation source 1
0 has a cathode electrode 11 and the Wehnelt 12 and the anode 13 made of LaB _6.

On the wafer stage 1 side of the electron beam generator 10, a first beam for shaping the electron beam into, for example, a rectangle is provided.
And a first electromagnetic lens 16 for converging the shaped beam. Further, second and third electromagnetic lenses 18 and 19 are arranged between the first electromagnetic lens 16 and the wafer stage 1, and a block is provided between the second electromagnetic lens 18 and the third electromagnetic lens 19. The mask 20 is arranged so as to be movable in the horizontal direction. The block mask 20 is provided with transmission holes 20a and 20b of various patterns as shown in FIG. 2, and in order to select one of the plurality of transmission holes 20a and 20b, the periphery of the block mask 20 is provided. First to fourth deflectors 21 and 2
2, 23 and 24 are arranged. And the first to fourth
The electron beams deflected by the deflectors 21, 22, 23, and 24 are configured to pass through the selected transmission hole 20a.

Between the third lens 19 and the wafer stage 1, there is provided a blanking 25 for blocking or transmitting an electron beam in accordance with a blanking signal, a fourth electromagnetic lens 26 for reducing the beam, and a round. The aperture 27 and the fifth lens 29 are arranged in order. Further, a refocus coil 28 for focus adjustment is arranged on the fifth electromagnetic lens 29.

A main deflector 33 and a sub-deflector 34 for positioning the electron beam on the sample W between the fifth lens 29 and the wafer stage 1, and an electron beam on the sample W mounted on the wafer stage 1. It has an objective electromagnetic lens 32 for projecting a beam. Note that, instead of the block mask 20, a blocking aperture array (B) having a large number of openings for forming a group of fine beams for irradiating the sample W is provided.
AA) may be provided, or a second slit portion capable of variably shaping the electron beam into a predetermined shape may be provided instead of the block mask 20.

In the above exposure column system, focusing of the electromagnetic lenses 16, 18, 19, 26 and 32, adjustment of the current density of electrons emitted from the electron beam source 10,
The movement of the wafer stage 1 is controlled according to a program of the control circuit 40. Further, a blur detection sample 2 for measuring blur of the electron beam is arranged at a position outside the wafer mounting area on the wafer stage 1. The blur detection sample 2 has a structure in which a metal film 4 such as tantalum or tungsten is formed on a silicon substrate 3 and a window 5 for exposing the silicon substrate 3 is formed in the metal film 4. The electron beam shaped by 20 or the like is controlled by the control circuit 40 so as to scan the surface of the metal film 4 and the surface of the silicon substrate 3 in the window 5.

Above the wafer stage 1 and below the objective electromagnetic lens 32, a reflected electron detector 6 for detecting the amount of electrons reflected from the blur detection sample 2 is arranged. The backscattered electron detector 6 has a current measuring device 41
Is connected, and the temporal and positional change of the amount of reflected electrons detected by the current measuring device 41 is obtained by the differential calculator 42. Then, the operation data d ₁ from the differential operation unit 42 and the electron beam irradiation position data d from the control circuit 40
Based on ₂ , the waveform acquisition circuit 43 draws a waveform of the intensity distribution of the charges applied to the blur detection sample 2. The waveform has a shape as shown in FIG. 3 corresponding to the transmission hole 20a, for example.

The electron beam intensity distribution of the electron beam on the wafer W based on the electron beam irradiation is hereinafter referred to as a measured electron beam intensity distribution, and the measured electron beam intensity distribution changes the focus value of the refocus coil 28. By doing so, a plurality of different waveforms are obtained, and their data d ₃ are stored in the first data storage unit 51 of the computer 50 shown in FIG. The waveform data d ₃ is represented by a function g _i (x) (i is an integer) for a predetermined axial direction x.

The shaping data d _4, which is a function B (i) representing the shape of a transmission hole such as the block mask 20, is stored in the second data storage section 52 of the computer 50.
Data d ₅ of the theoretical electron distribution function formula passing through the infinitesimal area Δx of the transmission hole of the block mask 20 is stored in the second data storage unit 52 of the computer 50. The data d ₅ of the electron (charge) distribution function formula uses the blur amount δ of the electron beam as one of the parameters.

The waveform calculation circuit 53 of the computer 50
Based on each data in the second data storage unit 52, the waveform of the electron irradiation intensity distribution expected by the theoretical electron beam irradiation on the sample W is calculated. Then, the calculated irradiation intensity distribution of the electron beam (hereinafter referred to as a theoretical electron irradiation intensity distribution) has a waveform as shown in FIG. 5, for example.
The data d ₆ is stored in the third data storage unit 54.

The charge distribution function in the infinitesimal area Δx is expressed by the following equation (1). Equation (1) is a process in which the distribution of the charged particles irradiated on the wafer W through the infinitesimal minute area Δx of the transmission hole 20a of the block mask 20 becomes a Gaussian distribution, and is shaped into a rectangular shape. The present invention can be applied to not only an electron beam that is shaped into a beam but also an electron beam that is shaped into a shape other than a rectangle.

[0026]

(Equation 1)

The data d of the shaped shape of the electron beam
₄ By calculating Equation (2), which is the integral of Equation (1), based on (for example, data of the line and space shape), a theoretical electron irradiation intensity distribution can be obtained.

[0028]

(Equation 2)

In equation (2), η (x) is
A function representing the shape of the transmission hole 20a of the mask 20;
Normally, it is 1 at the opening and 0 at the non-opening. First data
The waveform data of the measured electron irradiation intensity distribution stored in the storage unit 51
Data d_ThreeAnd the theoretical data stored in the third data storage unit 54
Waveform data d of electron irradiation intensity distribution ₆Is a computer 5
Compared by the fitting unit 55 within 0
You.

The fitting unit 55 changes the waveform of the theoretical electron irradiation intensity distribution by changing the value of the blur value δ of the theoretical electron irradiation intensity distribution represented by the equation (2).
Thus, seeking a theoretical electron irradiation intensity distribution waveform and the measured electron irradiation intensity distribution of the difference between smallest blur value magnitude of [delta] waveforms, the blur values and [delta] _i, the [delta] _i one waveform data defined as a unique blurring value of d _3. Then, δ _{i is obtained} for the function g _i (x) of all the waveform data d ₃ .

In this case, whether or not the waveform of the measured electron irradiation intensity distribution and the waveform of the theoretical electron irradiation intensity distribution are reduced is determined by the least square method shown in the following equation (3).
In Equation (3), h (δ) is a function indicating the square of the difference between the waveform of the measured electron irradiation intensity distribution and the waveform of the theoretical electron irradiation intensity distribution.

[0032]

(Equation 3)

H (δ) is, for example, a characteristic curve as shown in FIG.
And a blur value δ at which the minimum value of h (δ) is obtained._iSeeking
You will Blur value δ defined as above
_iAre a plurality of data stored in the first data storage unit 51 prepared in advance.
Waveform data d_ThreeFunction g of_iask for all of (x)
Will be. This was obtained with different focus
Function g of a plurality of measured electron irradiation intensity distributions _i(x)
Blur value δ to define each_iIs different
You.

Next, if the measured electron irradiation intensity distribution for each different focus I _f (x, δ _i) and, I _f (x,
Since the relationship between δ _i ) and the blur value δ _i is, for example, as shown in FIG. 7, the measured electron irradiation intensity distribution _{If best} (x, δ _i ) corresponding to δ _{i0 at} which the blur value δ _i becomes the smallest is obtained. The obtained focus value f is used as the optimum focus value f _0i for actual electron beam exposure. The determination of the size of the optimum focus value f _0i is performed by the optimum focus determination unit 56.
Done by

The optimum focus value f _0i is a focus value at which blurring due to electron scattering such as electron interaction on the sample W is _minimized . As described above, the unique blur value δ
process from _i definition to determine the optimum focus value f _0i is performed for all the data of the shape of the transmissive area such as the block mask 20, the optimum focus value f _0i obtained by the processing, the transmission area The data is stored in the fourth data storage unit 57 in association with the data of the shape function B (i).

The data stored in the fourth data storage unit 57 is taken in by the control circuit 40 and used as a focus value when exposing the resist R applied on the actual sample W (for example, a semiconductor substrate). Is done. The first to fourth data storage units 51, 52, 54, 57 as described above
, The blur value δ _i , and the optimum focus value f _0i are respectively displayed on a display unit (not shown).

In the above description, only the electron irradiation intensity distribution in the x-coordinate direction of the shaped electron beam is considered.
Considering the electron irradiation intensity distribution in the y coordinate direction orthogonal to the x coordinate, the following expression (4) is used instead of expression (1) as the distribution of charged particles in an infinitesimal area. Equation (4)
Can be expressed as in equation (5).

[0038]

(Equation 4)

[0039]

(Equation 5)

In the equations (4) and (5), the electron irradiation intensity distributions in the x-coordinate direction and the y-coordinate direction are the same, but there is a difference between the electron irradiation intensity distributions in the x-coordinate direction and the y-coordinate direction. Equations (6) and (7) below are applied to.

[0041]

(Equation 6)

[0042]

(Equation 7)

When the waveform of the actually measured electron irradiation intensity distribution is obtained, the amount of electrons incident on the reflected electron detector 6 is differentiated with respect to time. However, the reflection region has a fine width as shown in FIG. In the case of a thin line shape, the reflection region 61 is not a surface but a line, so that the electrons or signals incident on the reflected electron detector 6 are substantially differentiated, and the differential calculator 42 shown in FIG. 1 is omitted. You can do it. Also,
As shown in FIG. 8 (b), even when the reflection area is a minute dot 62, the state is substantially differentiated.

[0044] Incidentally, in the above description has been finally determined the optimum focus with blur value [delta] _i, the blur value [delta] _i
Is used in the correction formula of the proximity effect to correct the dose amount, so that a fine pattern can be formed with high accuracy.

[0045]

As described above, according to the present invention, the first waveform of the electron irradiation intensity distribution on the sample based on the actual measurement,
The second waveform of the theoretical electron irradiation intensity distribution is obtained, and the first waveform is compared with the second waveform, and the magnitude of the blur of the theoretical electron irradiation intensity distribution such that the difference is minimized. And the size of the blur is defined as the blur value of the electron beam, so that not only the case where the shaped shape of the electron beam is rectangular, but the definition of the blur according to the shaped shape is the same, and the electron beam exposure The blur value in the apparatus can be quantified, whereby the blur value can be accurately measured for an arbitrary electron beam shape in exposure. In addition, when the focus is corrected so that the blur value is minimized and the correction dose for the proximity effect is determined, a fine pattern with high accuracy can be formed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram (part 1) of an electron beam exposure apparatus showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of an electron beam shaping means used in the embodiment of the present invention.

FIG. 3 is a perspective view showing an example of a waveform of an actually measured electron irradiation intensity distribution obtained according to the embodiment of the present invention.

FIG. 4 is a configuration diagram (part 2) of an electron beam exposure apparatus according to an embodiment of the present invention.

FIG. 5 is a waveform diagram of a theoretical electron irradiation intensity distribution obtained by the electron beam exposure apparatus according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of a characteristic curve regarding a blur value calculated by the fitting unit according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a characteristic curve regarding focus calculated by the optimum focus determination unit according to the embodiment of the present invention.

FIG. 8 is a perspective view showing an example of a blur detection sample used in the electron beam exposure apparatus according to the embodiment of the present invention.

FIG. 9 is a configuration diagram of measurement of an amount of electron reflection on a sample by a general electron beam exposure apparatus.

FIG. 10 is a diagram showing a conventional waveform of electron irradiation intensity distribution on a sample and a definition of the blur.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer stage, 2 ... Sample for blur detection, 3 ... Silicon substrate, 4 ... Metal film, 5 ... Window, 6 ... Backscattered electron detector, 1
0 ... Electron beam source, 20 ... Block mask, 28 ...
Refocus coil, 32 ... objective electromagnetic lens, 40 ... control circuit, 41 ... current measuring device, 42 ... differential operation device, 43 ...
Waveform acquisition circuit, 50 computer, 51 first data storage unit, 52 second data storage unit, 53 waveform operation circuit, 54 third data storage unit, 55 fitting unit, 56 optimal focus Decision unit, 57
... A fourth data storage unit.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/027 H01L 21/30 541V

Claims (9)

[Claims] An electron beam generating means for emitting an electron beam toward a sample; a shaping means having a transmission area for shaping the electron beam; Focusing means for adjusting the focus of the electron beam converged by the focusing means; measuring the amount of reflection of the electron beam irradiated on the sample to measure the amount of reflection of the electron beam on the sample; Actual electron irradiation intensity distribution acquiring means for acquiring a first waveform of the electron irradiation intensity distribution of No. 1 and a theoretical electron irradiation intensity distribution of blurring as a parameter based on shape data of the transmission region of the shaping means. An electron irradiation intensity distribution calculating means for calculating the second waveform; and comparing the first waveform with the second waveform,
And a blur value defining means for defining, as an actual blur value of the electron beam irradiated onto the sample, a magnitude of the blur at which a difference between the waveform of the second waveform and the second waveform becomes a predetermined magnitude. Electron beam exposure apparatus. 2. The difference between the first waveform and the second waveform is:
2. The electron beam exposure apparatus according to claim 1, wherein the electron beam exposure apparatus is obtained by a least square method. 3. An electron beam exposure apparatus according to claim 1, wherein said predetermined magnitude of a difference between said first waveform and said second waveform is a minimum value. 4. A proper focus value obtaining means for obtaining a plurality of the blur values by changing the focus by the focus adjusting means, and obtaining a proper focus value which minimizes the blur value, and the proper focus obtaining means. Focus data storage means for storing the data of the appropriate focus value obtained by the above, and focus control means for controlling the focus of the focus adjustment means based on the data in the focus data storage means. The electron beam exposure apparatus according to claim 1. 5. The sample has a step, the measured electron irradiation intensity distribution obtaining means detects reflected electron of the electron beam scanning the step of the sample, and the reflected electron detection. 2. An electron beam exposure apparatus according to claim 1, further comprising a calculating means for calculating an electron irradiation intensity distribution based on a change in the amount of said reflected electrons detected by said means. 6. The sample has a reflection area of a fine line or a fine dot, and the measured electron irradiation intensity distribution acquiring means detects reflection electrons of the electron beam that scans the reflection area of the sample. 2. The apparatus according to claim 1, further comprising an electronic detecting unit.
An electron beam exposure apparatus according to claim 1. 7. The electron irradiation intensity distribution calculating means includes arithmetic means for calculating the second electron irradiation intensity distribution by integrating a two-dimensional Gaussian distribution function over the transmission area of the shaping means. The electron beam exposure apparatus according to claim 1, wherein: 8. The electron beam exposure apparatus according to claim 7, wherein the extent of the two-dimensional Gaussian distribution function in an arbitrary axis direction is different from the extent of the axial direction orthogonal thereto. . 9. After shaping an electron beam emitted toward a sample through a transmission area, the electron beam transmitted through the shaping means is adjusted by a focus adjusting means to converge on the surface of the sample, and A first waveform of a first electron irradiation intensity distribution on the sample is obtained by actually measuring a reflection amount of the electrons of the electron beam reflected from the sample, and based on shape data of the transmission region of the shaping unit, the blur is obtained. Of the theoretical electron irradiation intensity distribution
The first waveform is compared with the second waveform, and the first waveform is calculated.
An electron beam exposure method, wherein the magnitude of the blur at which the difference between the second waveform and the second waveform becomes a predetermined magnitude is defined as an actual blur value irradiated on the sample.