JP2629768B2 - Electron beam exposure system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to an electron beam exposure apparatus, and aims to use a vertical incidence type electron beam exposure apparatus with high accuracy and to be able to measure the height with high accuracy. A stage on which the object to be exposed is mounted, a stage driving means for moving the stage, a first deflecting coil for deflecting the electron beam, and the deflected electron beam being vertically incident on the surface of the object to be exposed. A second deflection coil that swings back
A vertical incidence type electron beam exposure apparatus comprising: a deflection control means for controlling a deflection current supplied to the first and second deflection coils; and an electron detector for emitting electrons generated from the surface of the object to be exposed. A deflection switching means for disabling the second deflection coil, and detecting a deflection amount d 'of the electron beam by the first deflection coil when detecting electrons incident on the electron detector, and detecting the deflection amount. mark displacement detection means for detecting a difference Δd between d ′ and the displacement d of the alignment mark from the center axis of the electron beam deflection;
Height calculation means for calculating the height of the object to be exposed is provided from Δd, d and the height l of the center of deflection of the electron beam by the first deflection coil from the reference plane.

[Industrial applications]

 The present invention relates to an electron beam exposure apparatus.

[Conventional technology]

When writing is performed using an electron beam exposure apparatus, it is necessary to measure the height of an object to be exposed such as a wafer to be written, in order to increase the overlay accuracy and the joining accuracy of the patterns.

In an exposure apparatus in which an electron beam is obliquely incident on a wafer, the height of the object to be exposed can be obtained from the angle of incidence of the electron beam on the wafer when the electron beam is deflected. However, in a system in which an electron beam is obliquely incident upon deflection, there is a problem in that the accuracy of connecting the obtained patterns is lower than in a system in which an electron beam is vertically incident.

On the other hand, in an exposure apparatus in which an electron beam is perpendicularly incident on a wafer, a laser length measuring device is used because the height cannot be determined from the incident angle of the electron beam. However, in the height measurement using this laser length measuring device, only a measurement accuracy of the order of μ is obtained, and it is difficult to say that the measurement accuracy is sufficient. Further, since the path of the length measuring beam of the laser length measuring device must be formed around the projection lens of the exposure device, there is a problem that the installation place of the length measuring device is limited and the configuration of the device is restricted.

[Problems to be solved by the invention]

As described above, conventionally, in a system in which an electron beam is obliquely incident on the surface of an object to be exposed, the height of the object to be exposed can be obtained with high accuracy, but the joining accuracy of the obtained pattern becomes poor, and the vertical incidence In such a system, although the connection accuracy is good, the height of the object to be exposed cannot be obtained with high accuracy, and as a result, the drawing accuracy cannot be sufficiently increased.

Therefore, an object of the present invention is to make it possible to accurately measure the height of an object to be exposed with a high-precision electron beam exposure apparatus of a vertical incidence system.

[Means for solving the problem]

As shown in FIG. 3, a vertically incident electron beam exposure apparatus deflects an electron beam 10 by a first deflection coil 6,
Further, the electron beam is returned by the second deflection coil 7 and
Reference numeral 10 denotes an exposure apparatus configured to be perpendicularly incident on an exposure target 11 such as a wafer. Reference numeral 8 in the figure denotes an electrostatic electron lens for converging the electron beam 10.

As shown in FIG. 1, according to the present invention, in the above-mentioned electron beam exposure apparatus of the vertical incidence type, the deflection switching means 4 for enabling the deflection current supplied from the deflection control means 1 to the second deflection coil 7 to be cut off. And actuate it to activate the second
When the return of the electron beam 10 by the deflection coil 7 is invalidated, the electron beam 10 is obliquely incident on the surface of the exposure target 11 by the deflection by the first deflection coil 6.

Reference numeral 9 in the figure denotes an electron detector, by which reflected electrons generated when an alignment mark 14 located at a predetermined position, for example, a position displaced by d from a deflection center axis position indicated by a dotted line, is operated by an obliquely incident electron beam 10 or Detect secondary electrons. The detection signal is sent to the mark position shift amount detection means 3 and a deflection amount signal d '(a signal indicating the deflection amount of the electron beam 10 sent from the deflection control means) when the reflected electrons are detected.
Is compared with the stage position signal d indicating the amount of displacement of the alignment mark 14 from the deflection center axis, thereby detecting the mark positional deviation amount Δd.

This Δd is sent to the height calculating means 2, where the distance l from the deflection center 13 to the reference plane, which is a known amount, and the above d,
The height difference Δl between the surface of the exposure object 11 and the reference plane is calculated.

(Operation)

The height of the center of deflection by the first deflection coil from the reference plane 15 is l as shown in FIG. 2, and the distance between the alignment mark 14 provided on the surface of the exposure object 11 and the center axis of the deflection of the electron beam. Let d be the scanning beam of the electron beam 10 by the first deflection coil 6 to detect the alignment mark 14.

At this time, if the exposure object 11 or the reference surface 15 is lower than the reference mark 15, the alignment mark is located at a position where the deflection efficiency is smaller than d as illustrated.
14 will be detected.

Since the deflection efficiency d ′ at this time is d−Δd, the reference surface
The height variation Δl of the object 11 with respect to 15 is Becomes This is easily obtained from the similarity of triangles. Here, the unit of the deflection efficiency is μm.

As described above, according to the present invention, the second deflection coil 7 for returning the electron beam 10 is invalidated so as to be in a state of oblique incidence, so that the height difference Δ
1 can be easily obtained. Therefore, when Δl is obtained, the second deflection coil 7 is operated again to return to the vertical incidence state, and exposure is performed.

If Δl can be known, it is easy to use this to correct the amount of deflection during exposure.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes deflection control means for controlling a deflection current supplied to the first and second deflection coils 6 and 7 based on exposure data, and 5 shifts the stage 12 to a desired position based on a stage position signal. Stage driving means for moving,
8 is an electrostatic electron lens for focusing the electron beam 10,
Reference numeral 9 denotes an electron detector, 11 denotes an object to be exposed such as a semiconductor wafer, 13 denotes a center of deflection of an electron beam by the first deflection coil 6, and 14 denotes an alignment mark provided on the surface of the object to be exposed. The above configuration is the same as the conventional vertical incidence type electron beam exposure apparatus.

In this embodiment, a height calculating means 2, a mark position shift amount detecting means 3, and a deflection switching means 4 are further provided. Hereinafter, the operation of this embodiment will be described.

Prior to exposure of an exposure target 11 such as a wafer mounted on a stage to an electron beam 10, first, a deflection switching unit 4 is operated, and a deflection current of a second deflection coil 7 supplied from a deflection control unit 1 is supplied. Is shut off, the retraction of the electron beam 10 is stopped, and the electron beam 10 is obliquely incident on the surface to be exposed.

Next, the stage 12 is moved by the stage driving means 5, and the alignment mark 14 provided on the surface of the object 11 is exposed.
Is displaced to a position separated by a predetermined amount, for example, d from the position of the deflection center axis of the electron beam 10 shown by the dotted line. The position of the alignment mark 14 is specified by a stage position signal.

In this state, a deflection current is supplied from the deflection control means 1 to the first deflection coil 6 to scan the vicinity of a position displaced by about d from the deflection center axis. When the electron beam 10 scans the alignment mark 14, since the alignment mark 14 is formed, for example, in a concave shape, reflected electrons are generated and the electron detector 9
Caught in

The deflection amount d 'when the reflected electrons are detected coincides with the position d of the alignment mark 14 when the height of the surface of the object 11 to be exposed and the reference surface (see FIG. 2) 15 are different. And d
± Δd.

The mark position shift amount detecting means 3 calculates the amount of deflection when the reflected electrons are detected by the deflection control means 1 from the deflection amount signal d '= d.
The difference Δd from the stage position signal d indicating the position of the alignment mark 14 is detected and sent to the height calculating means 2.

The height calculating means 2 receives the above d and Δd from the mark position shift detecting means 3 and, based on these and the height l of the deflection center 13 from the reference plane 15 which is a known amount, determines the height of the surface of the object 11 and the reference. The difference from the height of the surface 15 is calculated, and this is output as the height difference Δl.

This height difference Δl is, as described above, It is expressed as Here, the sign of ± indicates + when the height of the surface of the exposure object 11 is higher than the height of the reference plane 15, and −
Becomes

As described above, in the present embodiment, the height of the exposure target 11 can be easily and accurately determined in the oblique incidence state by the deflection switching means 4 while using the vertical incidence exposure apparatus with good drawing accuracy. Accordingly, high accuracy can be obtained in both the connection accuracy of the drawing pattern and the height measurement of the object to be exposed.

〔The invention's effect〕

As described above, according to the present invention, the height of an object to be exposed can be measured with high precision and easily by a vertically incident electron beam exposure apparatus.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention, FIG. 2 is an explanatory view of the principle of the present invention, and FIG. 3 is an explanatory view of a vertical incidence system. In the figure, 1 is a deflection control means, 2 is a height calculation means, 3
Is mark position shift amount detecting means, 4 is deflection switching means,
5 is a stage driving means, 6 is a first deflection coil, 7 is a second deflection coil, 9 is an electron detector, 10 is an electron beam, 11
Is the object to be exposed, 12 is the stage, 13 is the deflection center, 14 is the alignment mark, 15 is the reference plane, d is the stage position signal indicating the position of the alignment mark, and d 'is the deflection amount indicating the deflection position of the electron beam. Indicates a signal.

Claims (1)

(57) [Claims] 1. A stage (12) for mounting an object to be exposed (11).
And stage driving means (5) for moving the stage
A first deflecting coil (6) for deflecting the electron beam (10), and a second deflecting coil (7) for turning the deflected electron beam back so as to be perpendicularly incident on the surface of the object to be exposed.
A deflection control means (1) for controlling a deflection current supplied to the first and second deflection coils; and an electron detector (9) for making electrons generated from the surface of the object to be exposed incident. In the incident type electron beam exposure apparatus, the second deflection coil (7) and a deflection switching unit (4) for nullifying the first deflection coil (7), and the first deflection coil when the electron incident on the electron detector (9) is detected. A mark position for detecting a deflection amount d 'of the electron beam (10) by the deflection coil (6) and detecting a difference Δd between the deflection amount d' and the displacement amount d of the alignment mark from the center axis of the electron beam deflection. From the deviation amount detecting means (3) and the height d from the reference plane of the deflection center (13) of the electron beam (10) by the first deflection coil (6) and the electron beam (10), the object ( Height calculation means (2) for calculating the height of 11) is provided Electron beam exposure apparatus according to claim.