JP2009192684A - Method of adjusting electron beam drawing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an method of adjusting an electron beam drawing device, in which an irradiation amount for correcting CD variation due to fogging effect can be adjusted more precisely. <P>SOLUTION: In the method of adjusting the electron beam drawing device, a predetermined position of a mask for measurement is irradiated with an electron beam, a fogging amount is measured at a plurality of measurement positions provided at predetermined intervals at a periphery of the irradiation position irradiated with the electron beam, and a fogging effect correction parameter is obtained from fogging amounts measured at the plurality of measurement positions to adjust the irradiation amount of the electron beams with the fogging effect correction parameter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an adjustment method of an electron beam drawing apparatus for correcting a fogging effect and adjusting an electron beam irradiation amount in, for example, an electron beam drawing apparatus.

  In recent years, with the miniaturization and high integration of semiconductor devices, there has been a demand for improvement in mask processing accuracy, and an electron beam lithography apparatus having excellent resolution and capable of high-precision mask processing has been used. Yes.

  In such an electron beam drawing apparatus, a desired pattern is formed by controlling the electron beam to a desired position by a deflector and irradiating a substrate to be processed such as a blank coated with a resist. At this time, some of the irradiated electrons are reflected, but are collected by a reflection electron prevention plate provided on the surface facing the substrate to be processed. However, some of the electrons are rereflected and re-irradiate the resist on the substrate to be processed.

  The influence of such re-irradiation due to multiple scattering is called a fogging effect, which causes a CD (Critical Dimension) fluctuation in mask processing. In order to correct this, it is necessary to adjust the electron beam irradiation amount for each drawing field in accordance with the drawing area density of the drawn pattern and the distance between the patterns drawn adjacent thereto.

  Usually, an electron beam drawing apparatus calculates a fogging effect correction parameter by drawing a test pattern on a substrate on which a resist has been applied in advance, and measuring the developed pattern to measure the fogging effect correction parameter. The amount of irradiation is adjusted by feeding back to (see, for example, Patent Documents 1 and 2).

However, with further miniaturization, there is a demand for more precise adjustment of the irradiation amount for correcting the CD variation accompanying the fogging effect.
Japanese Patent Laid-Open No. 11-204415 JP 2007-150243 A

  As described above, in the electron beam drawing apparatus, with further miniaturization, a more precise adjustment of the irradiation amount for correcting the CD fluctuation accompanying the fogging effect is required. According to the adjustment method so far, the actual image is evaluated through the development process, and the correction parameter is calculated based on the evaluation result.

  However, the effects of in-plane non-uniform components depending on the process such as development loading due to the difference in the drawing area ratio, developer flow in the development apparatus, and measurement instrument errors due to resist measurement combined with the improvement in required accuracy. Can no longer be ignored.

  An object of the present invention is to solve such problems and to provide an adjustment method of an electron beam drawing apparatus capable of more precise adjustment of an irradiation amount for correcting a CD variation due to a fogging effect.

  According to the present invention, the electron beam is irradiated to a predetermined position of the measurement mask, the irradiation amount is measured at a plurality of measurement positions provided at predetermined intervals around the irradiation position irradiated with the electron beam, A method for adjusting an electron beam drawing apparatus is provided, wherein a fogging effect correction parameter is obtained from an irradiation amount measured at each measurement position, and the electron beam irradiation amount is adjusted by the fogging effect correction parameter.

  In the method for adjusting an electron beam lithography apparatus according to the present invention, it is desirable to measure the irradiation amount with a Faraday cup connected to an opening provided in a measurement mask.

  In the electron beam lithography apparatus of the present invention, it is desirable to simultaneously measure the dose at a plurality of measurement positions.

  Alternatively, in the electron beam drawing apparatus according to the present invention, it is desirable to sequentially measure the dose at a plurality of measurement positions.

  Furthermore, in the method for adjusting an electron beam lithography apparatus according to the present invention, it is desirable to transfer the measured irradiation amount and measurement position information to an electron beam irradiation amount adjustment mechanism provided in the electron beam lithography apparatus.

  According to the present invention, in the electron beam writing apparatus, the fogging effect can be adjusted more accurately by directly measuring the fogging effect, thereby correcting the CD variation.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
In FIG. 1, the conceptual diagram of the fog measurement which concerns on this embodiment is shown. In the fog measurement, the same structure as that used when irradiating a substrate to be processed such as a blank coated with a normal resist is used. In this embodiment, however, a measurement mask is used instead of the substrate to be processed as shown in the figure. Is used.

  In such a configuration, the electron beam 10 is transmitted from an electron gun (not shown) through a plurality of apertures (not shown), a deflector (not shown), and the objective lens 11 as shown in the figure. The measurement mask 12 is irradiated to a place where there is no opening 12a. A backscattered electron prevention plate 13 is provided on the surface of the objective lens 11 facing the measurement mask 12.

  The measurement mask 12 is made of a conductive material or a surface of a conductive material coated with a conductive film, and is grounded. In addition, it is considered that the behavior such as electron scattering in such a measurement mask is not significantly different from that in the case of irradiating a blank or the like which is a substrate to be processed.

  The measurement mask 12 is formed with a plurality of openings 12a having a diameter of, for example, 0.5 mm and measuring points at a predetermined pitch, for example, 1 to 2 mm. In addition, it is preferable that the opening diameter is small in order to perform measurement with higher accuracy. A Faraday cup 15 for receiving an electron beam with a cup-shaped stopper and measuring the current value via an insulator 14 is connected to each opening 12a.

  FIG. 2 shows a top view of the measurement mask 12. Although the opening part 12a is arrange | positioned suitably, for example, 10 places are provided in the 6-inch mask on both sides of the irradiation point 16 in a line. At this time, if the measurement width is, for example, about 3 to 25 mm, the fogging influence range can be measured.

  The fog measurement is performed by irradiating such a measurement mask 12 with an electron beam.

  FIG. 3 shows a flowchart of fog measurement and correction. First, a measurement mask 12 to which a Faraday cup 15 or the like is connected is loaded on a stage (not shown) (St. 1).

  Then, an arbitrary position on the measurement mask 12 is irradiated with the electron beam (St. 2). At this time, the electron beam is irradiated onto the measurement mask 12, and a part of the electron beam is reflected, and a part of the electron beam is reflected by the backscattering prevention plate 13 and re-irradiated to the measurement mask 12.

  Thus, the electron beam partially scattered and irradiated onto the measurement mask 12 enters the Faraday cup 15 through the opening 12a, and the irradiation amount at each measurement position is obtained from the measured current value. (St. 3).

  FIG. 4 shows an example of the fog measurement result thus measured. As shown in the figure, the current value (irradiation amount) increases in the vicinity of the irradiation point, decreases as the distance from the irradiation point increases.

Next, fitting is performed with an arbitrary function from the obtained irradiation amount and measurement position, and a fogging effect correction coefficient θ and an influence radius σ, which are fogging correction parameters, are obtained (St. 4). As an example,
Error function: f (x1, x2) = a / 2 (erf (x1 / s)-erf (x2 / s)) + d
In the case of fitting with, a is the CD fluctuation amount due to the fogging effect, and s is the influence radius σ. If the relationship between the dose (Dose) and the CD is obtained in advance, the fogging effect ratio θ can be obtained from the CD fluctuation amount a.

  The fog correction parameters (effect correction coefficient θ, influence range σ) obtained in this way are provided in an electron beam drawing apparatus, and are stored in a drawing data decoder, which is an electron beam irradiation amount adjustment mechanism with a built-in correction function. Transfer or input manually or automatically (St. 5). At this time, the fog correction parameter may be calculated inside the apparatus by inputting the measured current value (irradiation amount) and information on the measurement position as they are.

  Then, the irradiation amount of the electron beam is adjusted from the calculated fog correction parameter (St. 6), and actual drawing is performed (St. 7).

  According to the present embodiment, fog measurement can be performed without being affected by development loading, in-plane non-uniform components depending on the process, and measurement instrument errors due to resist measurement, and the electron beam can be measured with higher accuracy. The irradiation amount can be adjusted.

  In the present embodiment, the openings and the Faraday cups are arranged in a line, but the measurement may be performed by arranging them two-dimensionally. By arranging in this way, it becomes possible to perform measurement with higher accuracy.

(Embodiment 2)
In FIG. 5, the conceptual diagram of the fog measurement which concerns on this embodiment is shown. As shown in the figure, as in the first embodiment, the electron beam 20 is irradiated to an arbitrary position of the measurement mask 22 through the objective lens 21 provided with the backscattered electron prevention plate 23.

  Like the first embodiment, the measurement mask 22 is made of a conductive material or a surface of a conductive material coated with a conductive film, and is grounded, but has one opening 22a, This is different from the first embodiment in that there is one Faraday cup 25.

  The measurement mask is loaded on a stage (not shown), and can be moved in the XY direction by driving the stage. As in the first embodiment, a Faraday cup 25 for receiving an electron beam with a cup-shaped stopper and measuring the current value is connected to the opening 22a through the insulator 24.

  The fog measurement is performed by irradiating such a measurement mask 22 with an electron beam. The electron beam partially scattered and irradiated on the measurement mask 22 enters the Faraday cup 25 through the opening 22a, and the irradiation amount is obtained from the measured current value.

  And after measuring the irradiation amount in a predetermined position, the stage 22 is moved by a predetermined pitch (for example, 1 mm), thereby moving the opening 22a in the X direction and irradiating again. By repeating this operation, fog measurement in a desired region is performed.

  At this time, the information on the measurement position can be acquired, for example, by moving the stage at a predetermined speed, as time information, or by setting the irradiation position in advance and making the measurement order correspond to the set irradiation position. .

  The current value (irradiation amount) measured in this way, or the calculated fog correction parameter (effect correction coefficient θ, influence range σ) is the electron beam irradiation amount having a built-in correction function in the same manner as in the first embodiment. It is transferred manually or automatically to the drawing data decoder which is the adjustment mechanism. At this time, as in the first embodiment, the measured current value (irradiation amount) and information on the measurement position may be input as they are, and the fog correction parameter may be calculated inside the apparatus. Then, the irradiation amount of the electron beam is adjusted, and actual drawing is performed with the adjusted irradiation amount.

  According to the present embodiment, as in the first embodiment, the fogging amount can be obtained without being affected by the development loading, the in-plane non-uniform component depending on the process, and the error of the measuring instrument due to the resist measurement. It becomes possible to adjust the irradiation amount of the electron beam with higher accuracy.

  Furthermore, as in Embodiment 1, measurement cannot be performed with a single irradiation, but measurement can be performed with one Faraday cup without providing a large number of Faraday cups.

  In the present embodiment, the stage is moved in the X direction and the measurement is performed. However, the stage may be moved in the XY direction to perform two-dimensional measurement. By measuring in this way, it becomes possible to measure with higher accuracy.

  The present invention is not limited to the embodiment described above. Various other modifications can be made without departing from the scope of the invention.

The conceptual diagram of the fog measurement in 1 aspect of this invention. FIG. 6 is a top view of a measurement mask in one embodiment of the present invention. 3 is a flowchart of fog measurement and correction according to one embodiment of the present invention. The figure which shows an example of the fog measurement result in 1 aspect of this invention. The conceptual diagram of the fog measurement in 1 aspect of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 20 ... Electron beam 11, 21 ... Objective lens 12, 22 ... Measurement mask 12a, 22a ... Opening part 13, 23 ... Reflection prevention plate 14, 24 ... Insulator 15, 25 ... Faraday cup 16 ... Irradiation point

Claims (5)

Irradiate the electron beam to a predetermined position on the measurement mask,
At a plurality of measurement positions provided at predetermined intervals around the irradiation position irradiated with the electron beam, the irradiation amount is measured,
From the irradiation amount measured at each of the plurality of measurement positions, a fogging effect correction parameter is obtained,
An adjustment method of an electron beam lithography apparatus, wherein an irradiation amount of an electron beam is adjusted by the fogging effect correction parameter.   The method for adjusting an electron beam lithography apparatus according to claim 1, wherein the irradiation amount is measured by a Faraday cup connected to an opening provided in the measurement mask.   The method for adjusting an electron beam lithography apparatus according to claim 1, wherein the irradiation amounts at the plurality of measurement positions are simultaneously measured.   The method for adjusting an electron beam lithography apparatus according to claim 1, wherein the irradiation amounts at the plurality of measurement positions are sequentially measured.   5. The information on the measured irradiation amount and measurement position is transferred to an electron beam irradiation amount adjusting mechanism provided in an electron beam drawing apparatus. 6. Method for adjusting the electron beam lithography apparatus.

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