JPS60154440A - Optical mirror body for charged beam - Google Patents

Abstract

PURPOSE:To focus charged beams having different acceleration voltage on the same position at small incident angles while minutely stopping down by using focusing lenses, which respectively focus the respective charged beams, deflectors, which respectively deflect the charged beam directions and one common lens. CONSTITUTION:When impressing the same reference acceleration voltage on the charged beam sources 41-1 and 41-2, the radiated charged beams 51-1 and 51-2 are focused into the parallel beams through the lenses 31-1 and 31-2 for being incident on a common lens 11. The two parallel beams are focused on a fucusing position on a sample surface 1 through the common lens 11. Thereby, the amounts of deflection of the deflectors 21-1 and 21-2 are almost zeron. When the acceleration voltage of one of the charged beams sources, for instance of 41-1 is set slightly higher than the reference voltage, the beam 51-1 and the beam 51-2 can be focused on the same position by intensifying the focusing of the lens 31-1 and operating the deflector 21-1.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical mirror body for charged beams that simultaneously forms images of a plurality of charged beam sources having different acceleration voltages on one sample surface. , for example, is used for baton drawing during semiconductor device manufacturing, semiconductor device inspection, and the like.

[Background of the invention]

Conventionally, in order to focus charged beams having a plurality of different accelerating voltages onto a sample surface, a plurality of charged beam optical columns were simply combined and used. Therefore, in order to solve dimensional problems in installing the objective deflection system and preventing interference in the electromagnetic field distribution between the lens and deflector, it is necessary to use an optical system with a long working distance, resulting in large aberrations. As a result, the beam could not be narrowed down. In addition, the angle of incidence of some of the beams on the sample surface is large, as large as several tens of degrees, and as a result, it becomes difficult to focus on the sample surface due to beam deflection, and the amount of beam deflection is severely limited. There were also points.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problems in the prior art, and to focus a plurality of charged beams with different acceleration voltages onto the same sample surface at a small angle of incidence and finely narrow the focus. An object of the present invention is to provide an optical mirror body for a charged beam that can perform the following.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized by a plurality of charged beam sources having different acceleration voltages, and a focusing device provided for each charged beam from these charged beam sources to respectively focus each charged beam. A lens, a deflector that is installed at a downstream position of each focusing lens and deflects the charged beam direction, and a deflector that simultaneously receives the charged beams from these deflectors and transfers the image of each charged beam source to an arbitrary position on the downstream side. An optical mirror body consisting of one common lens that forms an image at a certain position.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention in which the number of charged beams is two. 1 is the sample surface, 11 is the common lens, 21-
1.21-2 is a deflector group, 51-1.62-2 is a focusing lens group, 41-1.41-2 is a charged beam source, 51-1
．． 51-2 is a charged beam. In Figure 1, 41-1.
A case is shown in which the same reference acceleration voltage is applied to the charged beam source 41-2. Charged beam source 41-
Charged beam 51-1.51 emitted from 1.41-2
-2 is focused into a parallel beam by lenses 61-1 and 61-2 and enters the common lens 11. The two parallel beams are focused by a common lens 11 onto a focal position on the sample surface 1. At this time, the amount of deflection of the deflectors 21-1 and 21-2 is almost zero.

FIG. 2 shows a state in which the acceleration voltage of one of the charged beam sources, for example 41-1, is set higher than the standard voltage. Since the charged beam 51-1 is moving faster than in the standard state, under the same optical conditions as in FIG.
- The amount focused by 1 is small, and the common lens 1
The position focused by 1 is behind the sample surface 1. An error also occurs in the position in the i direction perpendicular to the beam axis.

FIG. 6 shows a state in which the focusing of the lens 31-1 is strengthened. Since the focusing of the lens 51 - 1 is strengthened, the beam 51 - 1 with a high acceleration voltage is focused before entering the common lens 11 , and is further focused and deflected by the common lens 11 to focus on the sample surface 1 . However, since the amount of deflection of the beam 51-1 by the common lens 11 differs depending on the accelerating voltage, it does not match the focal position of the beam 51-2.

FIG. 4 is a diagram showing that the beam 51-1 is deflected by the deflector 21-1. By operating the deflector 21-1, the beams 51-1 and 51-2 can be focused at the same position.

FIG. 5 shows an embodiment according to claim 2. As described in FIG. 4, the deflector 21-1 and the deflector 61-
By operating lens 1, the beams 51-1 and 51-2 are focused on the same position, and the two beams are simultaneously deflected by a common deflector B. In this case, the two beams have different accelerating voltages, so the amount of deflection will be different, but by finely adjusting either or both of the deflectors 21-1 and 21-2, the beams can be focused on the sample surface 1. can be done.

Note that since the beam path within the common lens 11 is deviated from the center of the lens, aberrations may increase, but this can be countered by increasing the Bohr diameter of the common lens 11.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to realize an optical mirror body for charged beams that can finely focus charged beams having different accelerating voltages at a small angle of incidence at the same position.

[Brief explanation of drawings]

FIG. 1 is an optical system layout diagram for explaining the present invention in detail, FIGS. 2, 6, and 4 are optical system layout diagrams for explaining the operation of the present invention, and FIG. 5 is an optical system layout diagram for explaining the operation of the present invention. FIG. 2 is an optical system layout diagram showing an example. [Explanation of symbols] 1... Sample surface 11... Common lens 21-1.21
-2...Deflector group 61-1.61-2...Focusing lens group 41-1.41
-2...Charged beam source 51-1.51-2...Charged beam 6...Common deflector Patent applicant Nippon Telegraph and Telephone Corporation patent attorney Junnosuke Nakamura tl Figure O...2 Kakusai 4 figure

Claims (2)

[Claims] (1) A plurality of charged beam sources with different accelerating voltages, a focusing lens provided for each charged beam from the charged beam source to focus each charged beam, and a focusing lens provided at a position subsequent to each focusing lens. a common lens that receives the charged beams from these deflectors at the same time and forms an image of the charged beam source at an arbitrary position on a subsequent stage side; Optical mirror body for charged beam consisting of. (2) For a charged beam as set forth in claim 1, wherein the common lens is a common lens provided with a deflector common to the plurality of charged beams in its front stage, rear stage, or inside thereof. optical mirror body.