JP2006194618A - Evaluation method and scanning method of charged particle beam, and charged particle beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform accurate evaluation of a charged particle beam, even when deviation from an ideal response occurs on an edge part of a knife edge member. <P>SOLUTION: When performing scanning by the charged particle beam 1 so as to cross the edge part 4b of the knife edge member 4, and performing curve fitting between a signal waveform of the charged particle beam 1 detected by scanning and an evaluation function modeled based on a edge response function, and measuring a feature quantity of the charged particle beam 1 based on the result, the evaluation function is modeled based on the edge response function comprising the sum of two edge responses having different edge positions. Hereby, even when deviation from the ideal response occurs on the edge part 4b of the knife edge member 4, the charged particle beam 1 can be evaluated accurately. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for evaluating a charged particle beam in an apparatus using a charged particle beam such as an electron beam drawing apparatus or an ion beam apparatus.

  Prior to the actual drawing operation, the electron beam drawing apparatus evaluates the electron beam by measuring the size and position of the electron beam used for drawing or the focus state of the electron beam, and based on the evaluation result. The electron beam is adjusted. FIG. 1 shows an example of an apparatus used for such an electron beam measurement.

  In the figure, reference numeral 1 denotes an electron beam to be measured. The electron beam 1 has a rectangular cross section formed by two rectangular slits (not shown) located on the upper side of the apparatus and a deflector (not shown) provided between the two rectangular slits. Yes.

  The electron beam 1 is focused by the final lens 2 and further deflected by the electrostatic deflector 3. A knife edge member 4 is arranged on the lower side of the deflector 3. The knife edge member 4 is formed with a rectangular opening 4a. And in the knife edge member 4, the inner edge part 4b which prescribes | regulates each edge | side around this opening part 4a has a linear part corresponding to the said each edge, The thickness is formed thinly.

  An aperture member 5 that shields the scattered electron beam 1 is provided on the lower side of the knife edge member 4, and a Faraday cup 6 that detects the amount of current of the electron beam 1 is disposed below the aperture member 5.

  With the above configuration, when a predetermined deflection signal is applied to the deflector 3, the rectangular electron beam 1 is deflected in the X direction in the figure. As a result, the electron beam 1 is scanned across the inner edge portion 4 b of the knife edge member 4. Therefore, by scanning the electron beam 1 by the deflector 3, the electron beam 1 shifts from the state shielded by the knife edge member 4 to the state passing through the opening 4 or from the state passing through the opening 4. It will transfer to the state shielded by the knife edge member 4. FIG.

  The example shown in FIG. 1 is an example in which the electron beam 1 shifts from the state shielded by the knife edge member 4 to the state passing through the opening 4 by the scanning of the electron beam 1 by the deflector 3. That is, the electron beam 1 is initially deflected by the deflector 3 so that the electron beam 1 is positioned on the knife edge member 4 (see the dashed-dotted line rectangle A in FIG. 1) and shielded by the knife edge member 4. Is deflected in the X direction and scanned across the inner edge 4b of the knife edge member 4, so that the electron beam 1 is located at the center of the opening 4a (see the solid rectangle B in FIG. 1), Thus, the electron beam 1 is passing through the opening 4.

  When the electron beam 1 is scanned as described above, the electron beam 1 is initially shielded by the knife edge member 4 and the current (absorption current) of the electron beam 1 detected by the Faraday cup 6 is not detected. The beam 1 partially passes through the opening 4 sequentially, and the detection current (absorption current) of the electron beam by the Faraday cup 6 gradually increases. When the electron beam 1 reaches the position of the rectangle B in FIG. 1, the entire electron beam 1 passes through the opening 4, and the detection current signal of the electron beam 1 by the Faraday cup 6 reaches a peak.

  When the detection current signal of the electron beam 1 by the Faraday cup 6 is sampled at the scanning position of the electron beam 1 in the scanning, waveform data is obtained. At this time, assuming that the scanning position is x, the function representing the profile in the scanning direction of the electron beam 1 is p (x), and the response function of the edge portion 4b is T (x), the obtained waveform is a convolution integral as follows. The function F (x) is represented.

  Here, the ideal edge function is a step function T0 (x) as shown in the following equation.

  For reference, the profile function p (x) and the step function T0 (x) are shown in FIGS. 2 and 3, respectively.

A function F ₀ (x) representing a waveform when the step function T0 (x) is applied is an expression shown below, and is an integral form of the original profile function p (x).

Therefore, when the first derivative of the function F ₀ (x) is performed, the original profile function p (x) is reproduced.

  By the way, if the properties of the original electron beam 1 are known to some extent, the beam feature quantities such as the size information a, the position information b, and the blur information c are modeled as parameters, and a specific function p (x, a, b, c) can be set. Conventionally, using the model function p (x, a, b, c), the above-described feature quantities a, b, c of the electron beam 1 are derived and evaluated by the following method. .

  First, in the current measurement of the actual electron beam 1 through the Faraday cup 6, first-order differentiation processing is performed on the data string Gi (i = 1, 2,..., N) of the detection signal waveform obtained by sampling. The data string is assumed to be gi (i = 1, 2,..., N). Here, the data string Gi and the data string gi obtained based on the response function of the ideal edge portion are shown in FIGS. 4 and 5 for reference.

  Then, using p (x, a, b, c) as an evaluation function, the evaluation function p (x, a, b, c) so that a square residual s (a, b, c) expressed below is minimized. ) To obtain the parameters a, b, and c.

Alternatively, when the integral form F ₀ (x, a, b, c) of the model function p (x, a, b, c) is given in a specific function form, F ₀ (x, a, Using b, c) as an evaluation function, the fitting function of the evaluation function F ₀ (x, a, b, c) is performed so that the square residual S (a, b, c) expressed below is minimized, Each parameter a, b, c is obtained.

  Note that the point that the detection signal waveform is fitted to the modeled waveform in this way is described in Patent Document 1, for example.

JP-A-9-166698

  However, the edge portion 4b of the actual knife edge member 4 does not have an ideal response as described above due to the influence of organic matter adhesion (contamination), edge processing error, scattering of the electron beam 1 at the end face, and the like. .

Accordingly, the waveform data string Gi obtained via the Faraday cup 6 also deviates from the ideal waveform F ₀ (x), and this deviation occurs in the data string gi obtained by differentiating the waveform data Gi. Will also be affected. Here, FIGS. 6 and 7 show examples of the waveform data string Gi and the data string gi obtained in such a case. The example shown in FIG. 6 shows a case where organic matter is attached to the edge portion 4 b of the knife edge member 4. Further, the example shown in FIG. 7 shows a case where the shielding of the electron beam 1 at the end face of the edge portion 4b of the knife edge portion 4 is incomplete.

As described above, the function p (x, a, b, c) or the function F ₀ in the prior art is applied to the waveform data sequence Gi obtained based on the edge portion 4b that does not have an ideal response and the data sequence gi. When (x, a, b, c) is applied as an evaluation function, an error occurs in measurement, and the electron beam 1 cannot be accurately evaluated. In particular, since the organic substances attached to the edge portion 4b are stacked each time the scanning of the electron beam 1 is repeated, if the electron beam 1 is continuously measured, the result obtained for each measurement changes.

  Further, if the organic matter adheres to the edge portion 4b, the measurement error also increases accordingly. In this case, the portion of the edge portion 4b where no organic matter adheres is selected and the scanning position of the electron beam 1 is changed. There is a need. However, the change time depends on the judgment of the operator who operates the apparatus, and the judgment of the change time varies depending on the operator.

  The present invention has been made in view of such points, and the charged particle beam can be accurately evaluated even when the edge portion of the knife edge member deviates from the ideal response. An object is to provide a particle beam evaluation method.

  Another object of the present invention is to provide a charged particle beam that can automatically change the scanning position of a charged particle beam by judging the adhesion state of foreign matter (organic matter, etc.) to the edge portion of the knife edge member. A deflection method and a charged particle beam device are provided.

  The charged particle beam evaluation method according to the present invention scans a charged particle beam across an edge portion, and is modeled on the basis of a signal waveform of the charged particle beam detected along with the scanning and an edge response function. A charged particle beam evaluation method for performing a curve fitting with the evaluation function and measuring a feature amount of the charged particle beam based on the result, wherein the evaluation function is calculated from a sum of two edge responses having different edge positions. It is modeled based on the edge response function.

  The charged particle beam scanning method according to the present invention compares the values of the parameter S and the parameter w obtained by curve fitting with a predetermined reference value, and based on the comparison result, the edge by the charged particle beam. The scanning position of the part is controlled.

  Then, the charged particle beam apparatus according to the present invention compares the values of the parameter S and the parameter w obtained by curve fitting with a predetermined reference value in the same manner as the charged particle beam scanning method described above. Based on this, the scanning position of the edge portion by the charged particle beam is controlled.

  In the charged particle beam evaluation method of the present invention, the evaluation function applied to curve fitting is modeled based on an edge response function that is the sum of two edge responses with different edge positions. Therefore, the charged particle beam can be accurately evaluated even when the edge portion of the knife edge member deviates from the ideal response.

  In the charged particle beam scanning method or charged particle beam apparatus according to the present invention, the values of the parameter S and the parameter w obtained by curve fitting are compared with a predetermined reference value, and the charged particles are determined based on the comparison result. The scanning position of the edge portion by the beam is controlled. Accordingly, it is possible to automatically change the scanning position of the charged particle beam by determining the adhesion state of foreign matter (organic matter or the like) to the edge portion of the knife edge member.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 8 is a schematic configuration diagram showing an apparatus used for the charged particle beam evaluation method of the present invention. This apparatus is an apparatus constituting a part of the charged particle beam apparatus. In the present invention, the charged particle beam apparatus is an example of an electron beam drawing apparatus. Here, the same components as those of the conventional apparatus shown in FIG. 1 are indicated by the same numbers.

  In the figure, reference numeral 1 denotes an electron beam to be measured. The electron beam 1 has a rectangular cross section formed by two rectangular slits (not shown) located on the upper side of the apparatus and a deflector (not shown) provided between the two rectangular slits. Yes.

  The electron beam 1 is focused by the final lens 2 and further deflected by the electrostatic deflector 3. A knife edge member 4 is arranged on the lower side of the deflector 3. The knife edge member 4 is formed with a rectangular opening 4a. And in the knife edge member 4, the inner edge part 4b which prescribes | regulates each edge | side around this opening part 4a has a linear part corresponding to the said each edge, The thickness is formed thinly.

  An aperture member 5 that shields the scattered electron beam 1 is provided on the lower side of the knife edge member 4, and a Faraday cup 6 that detects the amount of current of the electron beam 1 is disposed below the aperture member 5. Thereby, the absorption current by the Faraday cup is detected.

  The detection signal of the absorption current detected by the Faraday cup 6 is converted into a digital signal by the AD converter 7. The digitized detection signal is output to the waveform memory 8. The detection signal supplied to and stored in the waveform memory 8 is read by the control CPU 9 and a curve fitting process described later is executed by the control CPU 9. The control CPU 9 controls the deflection circuit 10 for supplying a deflection signal (scanning signal) for scanning the electron beam 1 to the deflector 3. As a result, a deflection signal is applied to the deflector 3 by the deflection circuit 10.

  When a predetermined deflection signal is applied to the deflector 3, the rectangular electron beam 1 is deflected in the X direction. As a result, the electron beam 1 is scanned across the inner edge portion 4 b of the knife edge member 4. Therefore, by scanning the electron beam 1 by the deflector 3, the electron beam 1 shifts from the state shielded by the knife edge member 4 to the state passing through the opening 4 or from the state passing through the opening 4. It will transfer to the state shielded by the knife edge member 4. FIG.

  The example shown in FIG. 8 is an example in which the electron beam 1 shifts from the state shielded by the knife edge member 4 to the state passing through the opening 4 by the scanning of the electron beam 1 by the deflector 3. That is, the electron beam 1 is initially deflected by the deflector 3 so that the electron beam 1 is positioned on the knife edge member 4 (see the rectangle A in FIG. 8) and shielded by the knife edge member 4. Is deflected in the X direction in the figure and scanned across the inner edge portion 4b of the knife edge member 4, and as a result, the electron beam 1 is centered in the opening 4a (see a solid rectangle B in FIG. 8). Thus, the electron beam 1 passes through the opening 4.

  When the electron beam 1 is scanned as described above, the electron beam 1 is initially shielded by the knife edge member 4 and the current (absorption current) of the electron beam 1 detected by the Faraday cup 6 is not detected. The beam 1 partially passes through the opening 4 sequentially, and the detection current (absorption current) of the electron beam by the Faraday cup 6 gradually increases. When the electron beam 1 reaches the position of the rectangle B in FIG. 8, the entire electron beam 1 passes through the opening 4, and the detection current signal of the electron beam 1 by the Faraday cup 6 reaches a peak.

  In this scanning, the detection current signal of the electron beam 1 by the Faraday cup 6 is sampled with respect to the scanning position of the electron beam 1 to obtain waveform data. At this time, assuming that the scanning position is x, the function representing the profile in the scanning direction of the electron beam 1 is p (x), and the response function of the edge portion 4b is T (x), the obtained waveform is a convolution integral as follows. The function F (x) is represented.

  In the present invention, a function modeled as a sum of two edge responses having different edge positions in the X direction is applied as the response function of the edge portion 4b of the knife edge member 4. When formulated using the parameter S representing the response amount ratio and the parameter w representing the displacement from the reference position, the modeled function is expressed by the following equation. Here, the parameter S is set in a range of 0 ≦ S <1.

  In the above equation, the second term represents the response of the incomplete part. Application examples of the parameter S and the parameter w are shown in FIG. 6 and FIG. 7 described above.

  In the present invention, a waveform obtained by convolution integration is obtained by applying this modeled function to the above equation (1) [see Equation 8]. This calculation is executed by the control CPU 9.

  At this time, in the present invention, since the incomplete part, which is the second term of the above equation (2) [see Equation 7], does not have a complete step response, the correction function h (x) representing the deviation from the step response. To improve the accuracy of approximation. When the function h (x) is introduced in this way, the above equation (2) becomes the following equation.

  Assuming that the response function is the above equation (3), when the waveform of the profile function p (x, a, b, c) with respect to the electron beam 1 is calculated based on the above equation (1), the following equation is obtained.

The effect of introducing the function h (x) into the second term of the above equation (2) is the parameter of the blur amount from the ideal response of the second term of the above equation (3) into which the function h (x) is introduced. This is shown by setting d. Therefore, when S, w, and d are introduced as parameters, the actual waveform can be modeled and expressed using the function form F ₀ (x) of the ideal waveform.

  The differential form of the above equation (4) is as follows.

  Therefore, a data string obtained by performing first-order differentiation on the data string Gi (i = 1, 2,..., N) of the absorption current waveform of the electron beam 1 measured through the Faraday cup 6 and obtained by sampling. Is given by gi (i = 1, 2,..., N), the function f (a, b, c, S, w, d) obtained by the above equation (5) is used as an evaluation function and is expressed by the following equation: The fitting function of the evaluation function f (a, b, c, S, w, d) is performed so that the square residual s (a, b, c, S, w, d) is minimized, and the parameters a, Find b, c, S, w, d.

  Alternatively, the square remainder represented by the following equation is obtained using the integral form F (x, a, b, c, S, w, d) of the model function f (a, b, c, S, w, d) as an evaluation function. Fitting of the evaluation function F (x, a, b, c, S, w, d) is performed so that the difference S (a, b, c) is minimized, and each parameter a, b, c, S, w , D.

  The electron beam 1 can be evaluated using the parameters a, b, c, S, w, and d thus obtained.

  In addition, it is also possible to use the above equation (2) [see Equation 9] as a response function without introducing the correction function h (x) as described above. Assuming that the response function is the above equation (2), the waveform of the profile function p (x, a, b, c) with respect to the electron beam 1 is calculated based on the above equation (1) [see equation 8]. It becomes.

  The above-described fitting process may be performed using the differential form of the above equation as an evaluation function. Alternatively, the above-described fitting process may be performed using the differential integral form as an evaluation function.

  As described above, in the present invention, the charged particle beam (electron beam) is scanned across the edge portion, and modeling is performed based on the signal waveform of the charged particle beam detected during the scanning and the edge response function. In the charged particle beam evaluation method for performing the curve fitting with the measured evaluation function and measuring the feature amount of the charged particle beam based on the result, the evaluation function is an edge formed by the sum of two edge responses having different edge positions. Modeled in response function.

  Therefore, even when the edge portion deviates from the ideal response, the charged particle beam can be accurately evaluated.

  Furthermore, in the present invention, one of the two edge responses is modeled based on a correction evaluation function that represents a deviation of the edge position from the other edge response.

  Thereby, the evaluation accuracy of the charged particle beam can be further improved.

  Next, a charged particle beam scanning method and a charged particle beam apparatus according to the present invention will be described below.

  In the charged particle beam scanning method and charged particle beam apparatus according to the present invention, the values of the parameter S and the parameter w obtained by curve fitting in the above-described charged particle beam evaluation method, and predetermined reference values S0 and w0. When the parameters S and w exceed the corresponding reference values S0 and w0, the scanning position of the edge portion of the knife edge member by the charged particle beam is changed. That is, since the parameters S and w change depending on the adhesion state of foreign matter (organic matter or the like) to the edge portion, the scanning position of the edge portion by the charged particle beam is changed based on the change of the parameters S and w. .

  Thereby, the scanning position of the edge part by the charged particle beam is controlled based on the comparison result. At this time, another evaluation value R (S, w) = S · w may be calculated and compared with the reference value R0. The calculation and comparison are executed by the control CPU 9.

  In the charged particle beam scanning method and charged particle beam apparatus according to the present invention, the adhesion state of the foreign matter to the edge portion of the knife edge member is determined, and the scanning position of the edge portion of the knife edge member by the charged particle beam is controlled. Therefore, the scanning position can be automatically managed.

It is a schematic block diagram which shows an example of the apparatus used for the measurement of an electron beam. It is a figure which shows the function p (x) showing the profile of the scanning direction of an electron beam. It is a figure which shows step function T0 (x) corresponding to the response function of an ideal edge part. It is a figure which shows the data string Gi. It is a figure which shows the data sequence gi. It is a figure which shows each function p (x) and T (x) in case the organic substance adheres to an edge part, and each data sequence Gi and gi. It is a figure which shows each function p (x) and T (x) in case the shielding of the electron beam in the end surface of an edge part is incomplete, and each data sequence Gi and gi. It is a schematic block diagram which shows the apparatus used for the evaluation method of the charged particle beam in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electron beam (charged particle beam), 2 ... Last stage lens, 3 ... Deflector, 4 ... Knife edge member, 4a ... Opening part, 4b ... Edge part, 5 ... Aperture member, 6 ... Faraday cup, 7 ... AD Converter, 8 ... Waveform memory, 9 ... Control CPU, 10 ... Deflection circuit

Claims (6)

The charged particle beam is scanned across the edge, and the curve fitting is performed between the signal waveform of the charged particle beam detected during the scan and the evaluation function modeled based on the edge response function. In the charged particle beam evaluation method for measuring the feature quantity of the charged particle beam based on the above, the evaluation function is modeled based on an edge response function consisting of a sum of two edge responses having different edge positions. Characterized charged particle beam evaluation method. The charged particle beam evaluation method according to claim 1, wherein one of the two edge responses is corrected by a correction function that represents a deviation of an edge position from the other edge response. The charged particle beam is scanned across the edge, and the curve fitting is performed between the signal waveform of the charged particle beam detected during the scan and the evaluation function modeled based on the edge response function. In the charged particle beam evaluation method for measuring the characteristic amount of the charged particle beam based on the above, a parameter S representing the response amount and a parameter w representing the position difference are introduced as parameters representing the deviation from the ideal response of the edge portion. ,

A method for evaluating a charged particle beam, wherein the function F (x) given by (1) is used as an evaluation function. The charged particle beam is scanned across the edge, and the curve fitting is performed between the signal waveform of the charged particle beam detected during the scan and the evaluation function modeled based on the edge response function. In the charged particle beam evaluation method for measuring the characteristic amount of the charged particle beam based on the parameters, the parameter S representing the amount of response, the parameter w representing the position difference, and the ideal response are used as parameters representing the deviation from the ideal response of the edge portion. Parameter d representing the amount of blurring from the beam is introduced, and the amount parameter of the charged particle beam blur is c

A method for evaluating a charged particle beam, wherein the function F (x) given by (1) is used as an evaluation function. 5. The value of the parameter S and the parameter w obtained by curve fitting in the charged particle beam evaluation method according to claim 3 or 4 is compared with a predetermined reference value, and the edge by the charged particle beam is based on the comparison result. A scanning method of a charged particle beam, characterized by controlling a scanning position of a part. 5. The value of the parameter S and the parameter w obtained by curve fitting in the charged particle beam evaluation method according to claim 3 or 4 is compared with a predetermined reference value, and the edge by the charged particle beam is based on the comparison result. A charged particle beam apparatus for controlling a scanning position of a unit.

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