JPH11162390A - Electron beam drawing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily correct the positional shift of a generated electron beam and to obtain information on the shape and state of the electron beam by detecting secondary electron information obtained by a detector for detecting reflected electrons or secondary electrons and information derived from the shape of the electron beam formed based on secondary electrons obtained by the scanning of a mark by a deflector and/or information derived information on reflected electrons. SOLUTION: A mark 108 for adjustment is formed on a stage 107 and the stage 107 is driven so as to position the mark 108 for adjustment within a range possible to scan the mark by electron beam 102 in adjusting rectangular apertures 103 and apertures 105 for collective transfer to deflect the electron beam 102 and to scan the mark 108. Since the scanning starting position can be set to be a single position for all of the measurement of the rectangular apertures 103 and the apertures 105 for collective transfer for the control only for alteration, the starting position can be employed as a standard for measurement position. Defined rotation degree and magnification error calculation can be carried out by specifying the degree of the difference of the positions of the gravity center of the respective apertures 105 from the standard position and the position of the gravity center of the rectangular apertures 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing apparatus, and more particularly to an electron beam drawing apparatus suitable for improving the drawing accuracy of an electron beam having a transfer opening.

[0002]

2. Description of the Related Art An electron beam lithography apparatus has a lower throughput in drawing a semiconductor integrated circuit pattern than other exposure apparatuses. Therefore, various methods have been devised to improve the throughput. Among them, there is a batch transfer for drawing a certain area at one time.

On the other hand, there is also known a variable-shaped drawing method capable of drawing a rectangle of an arbitrary size.

[0004] The batch transfer opening and the variable shaping opening for realizing these drawing methods are mechanically movable and can be replaced. For this reason, a displacement or rotation of the opening occurs, which affects drawing. As a method of adjusting the drawing position, rotation, and magnification of the batch transfer, there is a method of adjusting using an opening for adjustment. Since this adjustment method is different from the aperture used for actual drawing, there is a possibility that a slight shift may occur even if the adjustment is performed.

[0005] Therefore, after mechanically moving the opening or after replacement, drawing is performed on the adjustment wafer coated with the photosensitive material using variable molding and batch transfer, and after developing the wafer, using a length measuring device or the like. The device is adjusted by measuring misalignment, rotation and magnification errors.

A technique for measuring the dimensions of a drawing pattern using a length measuring device is disclosed in Japanese Patent Application Laid-Open No. 62-239529.

[0007]

The above prior art requires a drawing step using an adjustment wafer before the drawing step.
There is difficulty in terms of drawing throughput. JP-A-62-2395
In the technique disclosed in Japanese Patent Publication No. 29, since the measurement is performed after drawing on the sample, the sample has to be replaced when the drawing fails due to the displacement of the drawing pattern, thereby reducing the throughput and reducing the throughput. It also leads to lower yield.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an apparatus capable of correcting a displacement of an electron beam generated at a transfer opening without using a sample for adjustment, and furthermore, information on the shape of the electron beam. It is an object of the present invention to provide an electron beam lithography apparatus capable of obtaining the following.

[0009]

In order to achieve the above object, the present invention provides an electron source, a transfer opening for forming an electron beam emitted from the electron source, and an electron beam formed by the transfer opening. An electron beam lithography apparatus provided with a deflector for scanning a shaped electron beam, a detector for detecting reflected electrons or secondary electrons obtained by irradiating the shaped electron beam, and a detector obtained by scanning a mark by the deflector. Secondary electronic information,
And / or means for detecting information derived from the shape of the molded electron beam based on reflected electron information.

According to the present invention, by scanning the formed electron beam on the mark, it is possible to obtain the shape information of the formed electron beam as a secondary electron or a reflected electron signal.

Further, as one of the information derived from the shape of the molded electron beam, it is possible to obtain positional information of an arbitrary position of the molded electron beam. In particular, the center of gravity of the molded electron beam is specified, compared with the center of gravity information of the electron beam stored in advance, and the sample is actually irradiated with the electron beam by controlling so as to reduce the difference. It is possible to control the position of the electron beam without taking steps such as observing the electron beam.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of an electron beam lithography apparatus most suitable for realizing the present invention. An electron beam 102 emitted from an electron gun 101 becomes a rectangular electron beam at a rectangular opening 103, and passes through an opening 105 of an arbitrary shape by a deflector 104 of batch transfer to form an electron beam of an arbitrary shape. . The formed electron beam is controlled by an electron optical system 106 including a deflector, and scans an adjustment mark 108 fixed to a stage 107.

The backscattered electrons emitted at this time are detected by a backscattered electron detector 109 typified by a semiconductor detector, and converted into an electric signal by an analog signal processing unit 111. In addition,
In this embodiment, reflected electrons are detected, but secondary electrons may be detected. Alternatively, both electrons may be detected by using a backscattered electron detector and a secondary electron detector.

The analog signal processing unit 111 further includes a range switching circuit, a band limiting circuit, a differentiating circuit, and the like. The control computer 115 performs processing as needed. The analog signal processed by the analog signal processing unit 111 is converted into a digital signal of about 12-bit gradation by the A / D converter 112 and then stored in the memory 113 as signal data. The control computer 115 reads out the signal data via the data bus 114, and calculates the position of the electron beam from the signal data. Since this position data is normally output in the number of shots, the control computer 115 must know the movement amount per shot and convert it to coordinate data. The electron beam is controlled so that the movement amount is constant. The flow of the process of the present invention will be described with reference to the operation flowchart of FIG. 2 and FIGS. 4 to 5 by taking the calculation of the position, rotation, and magnification of the electron beam at the batch transfer opening of FIG. 3 as an example.

The electron beam that has passed through the batch transfer opening changes into various shapes depending on the shape of the opening. Although drawing accuracy such as throughput is improved by drawing using the changed electron beam, there is a possibility that the position of the opening itself may be shifted due to displacement, rotation, or the like. Therefore, by calculating the specific position (for example, the position of the center of gravity) of the electron beam on the sample when passing through the opening for batch transfer, the drawing position of the selected opening can be adjusted.

In order to adjust the position of the electron beam passing through the batch transfer opening 301, in step 201, the center of gravity position calculated from the opening area of each batch transfer opening and the reference position (drawing position for batch transfer) ) 302 is calculated. The method of calculating the position of the center of gravity is calculated by the formula shown in Expression 1 using the opening area of each position when the opening is subdivided in the vertical direction 401 or the horizontal direction 402 as shown in FIG. Therefore, the position of the center of gravity becomes the position indicated by 403, and the distance 404 from the reference position can be calculated.

[0018]

(Equation 1)

In step 202, the electron beam that has passed through the batch transfer opening is adjusted to an adjustment mark 502 on the stage.
Is scanned to obtain a backscattered electron signal 501 during scanning. 5
01 is obtained based on the amount of backscattered electrons detected by the backscattered electron detector 109 (vertical axis) and the irradiation position of the electron beam (horizontal axis). In the case of the present embodiment, the irradiation position of the electron beam is identified based on the deflection current applied to the electron beam deflector.

In step 203, the electron beam profile 503 is obtained by differentiating the acquired reflected electron signal.
To get.

The profile 503 is information derived from the shape of the electron beam passing through the transfer opening. That is, by differentiating the acquired reflected electron signal, what is obtained is information on the shape of the electron beam itself that has passed through the transfer opening.

In step 204, profile 5
From 03, the position of the center of gravity is calculated using Equation 2. Incidentally, the position of the center of gravity (specific position) on the sample of the electron beam calculated in this way is also information derived from the shape of the electron beam of the present invention.

[0023]

(Equation 2)

In step 205, steps 201 to 204 are performed for the variable forming opening 307, and the deviation amount between the variable molding drawing position and the batch transfer drawing position is calculated as shown in Expression 3, and the deviation amount is calculated. Is the position adjustment amount at the opening. D in Equation 3 is a shift amount, and C
r is the position of the center of gravity of the batch transfer opening, Cd is the design distance between the reference position and the center of gravity of the batch transfer opening, Sr is the center of gravity of the variable forming opening, and Sd is the reference position of the variable forming opening. It is a design distance between the position and the position of the center of gravity.

[0025]

D = (Cr-Cd)-(Sr-Sd) (Equation 3) In step 206, the above operation is performed for all the batch transfer openings (303 to 306) to calculate the position adjustment amount. I do.

By adjusting the position of the collective transfer with this amount of position adjustment, there is no displacement even if drawing is performed using both the variable molding and the collective transfer or only the collective transfer.

In this embodiment, an adjustment mark 108 is provided on the stage 107, and for example, a rectangular opening 103
When the batch transfer opening 105 is replaced or adjusted, the stage 107 is driven so that the mark 108 is positioned within a scannable range of the electron beam 102, and the mark 108 is scanned by deflecting the electron beam 102. The scanning start position at that time can be set to the same position for all the measurements of the rectangular opening 103 and the batch transfer opening 105 for controlling only the deflection, and thus becomes a reference of the measurement position. By calculating the position of the center of gravity of each opening from the reference position, the amount of deviation between the position of the center of gravity of the batch transfer opening 105 and the position of the center of gravity of the rectangular opening 103 is specified. When determining the center of gravity position in design, the same position of each opening is used as a reference position. In any case, the position of the center of gravity from the reference position is the position information. The position data of the stage is obtained by, for example, a laser length measuring device (not shown) provided on the stage.

Further, since the position shift occurs even when the rotation or magnification error occurs in the electron beam, the rotation and magnification of the electron beam are adjusted using the position adjustment amount.

In step 207, the formula shown in Equation 4 is minimized from the calculated position adjustment amount (the measured distance between the collective transfer opening and the variable forming opening) and the design distance between the collective transfer opening and the variable forming opening. An approximation coefficient is calculated by approximation by the square method. In Expression 4, Mx and My are the deviation amounts of the position adjustment amount from the design distance, Dx and Dy are the design distance, and a to f are approximation coefficients.

[0030]

Mx + Dx = a + b * Dx + c * Dy My + Dy = d + e * Dx + f * Dy (Equation 4) In step 208, the rotation amount Dr and the magnification error Dg are calculated from the calculated approximation coefficients using Expression 5.

[0031]

(Equation 5)

In step 209, if the calculated rotation amount and magnification error are within the allowable range, the process is terminated. If not, steps 201 to 208 are performed while gradually changing the voltage values of the rotating lens and the reducing lens. I do.

In step 210, the approximation coefficient is calculated by approximating the expression shown in Expression 6 by the least square method from the voltage values of the rotating lens and the reducing lens and the rotation and magnification errors at that time. In Equation 6, Dr and Dg are the rotation amount and the magnification error, and Vr,
Vg is a voltage value of the rotating lens and the reduction lens, and a to d are approximation coefficients.

[0034]

(Equation 6) Dr = a + b * Vr Dg = c + d * Vg (Equation 6) In step 211, rotation is performed based on the calculated approximation coefficient,
The voltage value of the rotating lens and the reduction lens at which the magnification error becomes 0 is the optimum voltage value. The voltage value is set for each lens.

In step 212, the position adjustment is performed again, so that the rotation and magnification errors are reduced, and the drawing position deviation in the variable molding and the batch transfer is reduced.

Although one of the information derived from the shape of the electron beam has been described above with reference to the position of the center of gravity of the electron beam formed by the transfer opening, for example, the shape of the formed electron beam is not limited to the above-described example. In the case of a triangle as shown in the example, a vertex of the triangle may be set as the specific position.

The specification by the position of the center of gravity can be performed even if the shape of the electron beam is circular or the structure is complicated. Therefore, the specification has been described in detail as a preferred example for carrying out the present invention.

[0038]

As described above, according to the present invention, the adjustment of the projection aperture can be performed without using the adjustment sample and the adjustment aperture, thereby realizing high-speed and high-precision adjustment. be able to.

Therefore, steps such as drawing for adjustment after mechanically moving the opening or after replacement can be omitted, and the overall throughput of the apparatus is improved.

In addition to the above effects, according to the present invention, information derived from the shape of the molded electron beam can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a configuration of an electron beam writing apparatus.

FIG. 2 is an operation flowchart of the present invention.

FIG. 3 is an explanatory view of an embodiment of the present invention (a batch transfer opening and a variable-shaped opening).

FIG. 4 is an explanatory diagram of an embodiment of the present invention (a method of calculating the position of the center of gravity of the opening for batch transfer).

FIG. 5 is an explanatory diagram of an embodiment of the present invention (a method of calculating the position of the center of gravity from reflected electrons).

[Description of References] 101: electron gun, 102: electron beam, 103: rectangular opening,
104: Deflector for batch transfer, 105: Opening for batch transfer,
Reference numeral 106: electronic engineering system, 107: stage, 108: adjustment mark, 109: reflection electron detector, 110: drawing control system, 111: analog signal processing unit, 112: A / D converter, 113: memory, 114: data Bus 115
... Control computer, 201 ... Design distance calculation processing between the center of gravity position and the reference position, 202 ... Mark scanning on the stage, 203
... Signal data differentiation processing, 204 ... Gyroid position calculation processing, 2
05: position adjustment amount calculation processing, 206: position adjustment amount calculation processing of all batch transfer openings, 207: approximate expression calculation processing from position adjustment amounts and design values, 208: rotation amount and magnification error calculation processing from approximate expressions, 209 ... Rotation amount and magnification error determination processing, 21
0: rotation amount and magnification error calculation processing by changing the lens voltage value; 211: approximation expression calculation processing from the lens voltage value, rotation amount, and magnification error; 212: optimal lens voltage value calculation from the approximation expression; Setting processing, 213: Reposition adjustment amount calculation processing, 301, 303 to 306: Batch transfer opening, 302
... Reference position (collective transfer drawing position), 307... Variable forming opening, 401... Opening area when the batch transfer opening is subdivided (horizontal direction), 402. Direction), 403: Center of gravity position calculated from opening area, 404: Distance between center of gravity position and reference position, 501:
When a mark is scanned by batch transfer, a reflected electron signal 502
... Adjustment mark on stage, 503. Electron beam profile.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/027 H01L 21/30 541N (72) Inventor Yasuhiro Someda 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (10)

[Claims] 1. An electron beam writing apparatus comprising: an electron source; a transfer opening for forming an electron beam emitted from the electron source; and a deflector for scanning the electron beam formed by the transfer opening. A detector for detecting reflected electrons or secondary electrons obtained by irradiating the obtained electron beam, and secondary electron information obtained by scanning the mark by the deflector, and / or An electron beam lithography apparatus comprising means for detecting information derived from the shape of a molded electron beam. 2. The method according to claim 1, wherein the means for detecting information derived from the shape of the electron beam comprises scanning the shaped electron beam by scanning the shaped electron beam on a mark by the deflector. An electron beam drawing apparatus comprising means for specifying a position of a center of gravity. 3. The method according to claim 2, wherein the position of the center of gravity is calculated based on a profile of reflected electron information or secondary electron information obtained by deflecting the formed electron beam on the mark. Electron beam drawing apparatus. 4. The transfer opening according to claim 2, wherein the transfer opening is a batch transfer opening in which a pattern to be drawn is formed in the opening, and the calculated center of gravity of the transfer opening is stored in advance. An electron beam lithography apparatus, comprising: means for comparing the center-of-gravity position information of the transfer opening and calculating the difference. 5. The transfer opening according to claim 2, wherein the transfer opening is a variable molding opening, and compares the calculated center-of-gravity position of the transfer opening with pre-stored center-of-gravity position information of the transfer opening. An electron beam lithography apparatus comprising means for calculating the difference. 6. The batch transfer opening according to claim 2, wherein the transfer opening is a variable molding opening and a batch transfer opening which is arranged on the sample side of the variable molding opening and has a pattern to be drawn in the opening. And a means for calculating the difference between the positions of the centers of gravity of the variable molding opening and the batch transfer opening. 7. An electron beam writing apparatus according to claim 4, further comprising a deflector for deflecting the formed electron beam so as to suppress the difference in the position of the center of gravity. 8. The electron beam lithography apparatus according to claim 4, further comprising a rotary lens and / or a reduction lens controlled to suppress the difference in the position of the center of gravity. 9. The electron beam drawing apparatus according to claim 1, wherein the information derived from the shape of the electron beam is position information of an arbitrary portion of the molded electron beam. 10. An electron beam is scanned over a sample or a mark provided on a sample stage, and the shape information of the electron beam is obtained based on secondary electron information or reflected electron information obtained by the scanning. An electron beam shape specifying method using an electron beam drawing apparatus.