JPS6258620A - Charged beam device - Google Patents

Abstract

PURPOSE:To perform a positioning operation by suppressing the effect of a charged beam inflicting on a sample by a method wherein a conductive body with an aperture part, through which the charged beam can be passed, is provided directly above the sample such as a large scale integrated circuit (LSI) and the like leaving an interval and covering the surface of the sample. CONSTITUTION:An X-Y stage 8 carrying sample 3 is arranged in a chamber. A device with which an electron beam 2 is generated, a deflector 1 with which the direction of the electron beam 2 is controlled, and an objective lens 9 with which the aperture for the electron beam 32 is controlled are provided on the upper part of the chamber, and using the above-mentioned materials, a control is performed for the purpose of projecting a charged beam on the sample 3. A thin film insulating layer 5', which is necessary in the process of manufacture, and a resist 6 are formed on the sample 3. A charged shield plate 10, having the aperture part 10A with which the range of irradiation of the electronic beam 2 on the sample 3 is controlled, is provided in the chamber, and the movement of the electron beam 2 is controlled by a shifting mechanism 11 so that the electron beam 2 is made to irradiate on the reference mark 4 of the sample 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charged beam device that enables highly accurate position detection.

[Prior Art] Position detection technology in charged beam devices has improved primarily with the development of semiconductor device manufacturing. That is, it includes a beam positioning technique for an electron beam lithography device in forming a batten of an LSI or the like, and a batten position measuring technique for an electron beam length measuring machine in evaluating a formed batten. These technologies are becoming extremely important as batons become smaller.

For example, to describe the formation of a batten by the electron beam direct drawing technique with reference to FIG. 3, first, the electron beam 2 that has passed through the deflector 1 scans the reference mark 4 previously provided on the sample 3. The electron beam incident on the reference mark 4 is backscattered in the sample, penetrates the thin metal layer 5 or resist 6 deposited or coated on the reference mark, and is captured by the detector 7. Next, the relative position information between the beam and the mark is calculated from the signal obtained by the detector 7, the beam position is corrected, and the circuit button is drawn at the correct position. In addition, in the figure, 8 is a ×Y stage, and 9 is an objective lens. In this way, several layers to more than ten layers of battens are superimposed using the marks provided in advance on the sample as positional standards, making it possible to achieve highly accurate superposition. However, in the device manufacturing process, the sample surface is made of oxides, nitrides, and PSG.
Often covered with insulating materials such as films and resists,
When these were irradiated with an electron beam, charge-up occurred, which often caused errors in the position of the incident beam. Furthermore, when an insulating substrate such as GaAs is used as a sample substrate, the electrons incident on the substrate often have nowhere to go, and charge is accumulated there. There were times when it would shift.

Conventionally, in order to deal with such sample charge-up, for example, the paper by Wattg et al.
Electron Device
s, Vol, ED-28, No, 11°P, +33
8.1981) and Japanese Unexamined Patent Publication No. 55-87434, a conductive thin film such as amorphous silicon is deposited on the sample surface or resist surface by thin deposition or sputtering, and the thin film is passed through the YX stage 8. The method used was to set the voltage to the same potential as ground.

However, in these methods, not only the steps of attaching and removing the thin film are increased, but also the sample itself may deteriorate due to the increase in temperature of the sample due to the attaching step. Another drawback is that the resolution of the resist batten deteriorates due to scattering of the electron beam incident on the adhered thin film. Furthermore, when the sample is a magnetic material, there is a similar drawback in that the electron beam trajectory is bent by magnetic lines of force from the sample. This situation is a common problem in baton drawing devices, length measuring devices, microscopes, etc. that use electron beams. The same applies to charged beam devices other than electron beams, such as ion beam devices.

[Problems to be Solved by the Invention] An object of the present invention is to provide a charged beam device that prevents the influence of charges accumulated on an insulating sample or the influence of magnetism on a magnetized sample and enables highly accurate beam positioning. There is a particular thing.

[Means for Solving the Problems] In order to achieve the above object, in the charged beam device according to the present invention, a conductive body is provided directly above the sample, covering the surface of the sample, and having an opening through which the charged beam passes. ing.

[Function] Electric lines of force generated from charges accumulated in the insulating sample are absorbed by this conductive material, making it difficult for them to affect the incident beam. In conventional charged beam devices, as shown in Figure 3, the distance from the bottom of the objective lens located at the bottom of the electron optical column to the sample surface is determined by the design constants of the electron optical system and the size of the detector for backscattered electrons. A certain space (or distance a) was required. This distance was approximately 20-50 mm+. The electric lines of force extending from the charges accumulated in the insulating sample are closed at the grounded metal surface at the bottom of the objective lens.
The trajectory of the electron beam passing through the objective lens is bent by the electric field until it reaches the sample surface. In the experiments conducted by the present inventors, the amount of deviation of the incident beam trajectory is determined by the distance from the bottom of the objective lens to the sample surface.

It is known that the distance from the bottom of the objective lens to the sample surface is determined by the amount of accumulated charge and the energy of the incident beam. We found that this is the most important factor. These findings apply equally to magnetized samples. By installing the conductive material according to the invention, the deviation of the incident beam trajectory is significantly reduced.

[Example] FIG. 1 is a diagram illustrating the present invention in detail.

This example shows an electron beam exposure apparatus using a conductive material as an electric field shield plate. In the figure, 1 is a deflector, 2 is an electron beam, 3 is a sample, 5' is a thin film insulating layer, 6 is a resist, and 7 is a detector. 8 is an XY stage, 9 is an objective lens, 10 is an electric field shield plate, and 11 is an electric field shield plate moving mechanism.

An aluminum plate was used as the electric field shield plate 10, and was fixed at a position 1 mm directly above the sample. Electric field shield plate 1
0 is grounded via the mirror body. An opening 10A (2.5 ma+' in this embodiment), which is slightly larger than the beam deflection field, is provided in the center of the electric field shield plate 10, and the sample 3 can be irradiated with an electron beam through the opening 10A. Note that the beam axis and the opening 10 of the electric field shield plate
In order to facilitate positioning with A, an electric field shield plate moving mechanism 11 is provided.

Because of this configuration, the electric field due to charges on the thin film insulating layer 5' and the resist 6 on the sample 3 is applied to the sample 3.
and is limited to a very narrow range of the electric field shield plate 10,
It no longer acts to bend the incident beam trajectory. If the opening 10A of the electric field shield plate is kept to a few square meters or less as in this example, the number of electric lines of force extending through the opening will be very small. There was a similar effect on the incident beam position shift.

FIG. 2 shows experimental data showing the effects of the present invention. The figure shows the relationship between the amount of beam positional deviation and the distance between the lower surface of the electric field shield plate and the sample surface when performing slam writing on a resist coated on a GaAs substrate at an accelerating voltage of 30 kV. The radiation dose given for each baton formation was 1.2 X 10-' l
: (2008 LC/cm2 in terms of resist sensitivity), and the amount of positional deviation between the bangs is taken as the amount of positional deviation of the beam. As is clear from this figure, the smaller the distance from the electric field shield surface to the sample, the smaller the amount of beam position deviation.When the distance was 30Il1m, the deviation was as much as 1gm, but when the distance was less than a few mm, there was no deviation at all. . Even when the irradiation dose is higher than that in this experiment, this tendency does not change at all, resulting in normal batten formation (resist sensitivity number ~ number + kc/crn2), batten position measurement, or image shift using a scanning electron microscope. It was found that there was no problem with deterioration of resolution.

As is clear from these results, the conventional charged beam device does not have a special electric field shield plate, and therefore,
The electric charge on the insulating sample has a large influence on the incident beam position, and in order to determine the correct beam position or observe the image, it is complicated to attach a conductive thin film onto the insulating sample. The present invention greatly improves this type of problem in that an insulating sample can be used as it is as a sample for drawing, length measurement, or image observation.

Note that the electric field shield plate is not limited to aluminum.
It is clear that any electrically conductive material can be used, and a high permeability material such as permalloy as the electrically conductive material will act as an electric and magnetic field shield plate.

Furthermore, it is clear that the mounting part is not limited to the side wall of the mirror body, but may be mounted anywhere as long as it can be grounded.

The embodiment shown in FIG. 1 shows an example in which a conductive body serving as an electric field shield plate is provided apart from the sample surface. However, for image observation in a relatively narrow range, it is also possible to place the electric field shield plate in contact with the surface of the sample after placing the sample on the XY stage. In addition, when it is necessary to irradiate the entire surface of a large sample with an electron beam, such as when drawing, a mechanism for moving the electric field shield plate upward and downward can be added to
Immediately before moving the stage, the electric field shield plate may be separated from the sample and moved to a predetermined position, and then the electric field shield plate may be placed in contact with the sample again.

Furthermore, such a configuration can be applied not only to an electron beam drawing device but also to a charged beam device such as an electron beam length measuring machine or a scanning electron microscope. Further, the present invention can be applied not only to electron beam devices but also to ion beam devices.

[Effects of the Invention] As explained below, in the present invention, the influence of charges on an insulating sample can be removed by a simple method, which not only improves the positioning accuracy of the charged beam but also improves the accuracy of the conventional conductive thin film. This has the advantage of expanding the scope of application of the charged beam device, such as being effective even for samples to which it is impossible to attach.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view of an electron beam exposure apparatus as an embodiment of the present invention, Fig. 2 is a diagram showing changes in beam position shift depending on the distance between the electric field shield plate and the sample surface, and Fig. 3 is a diagram showing a conventional electron beam exposure system. FIG. 2 is a partial cross-sectional view of a beam exposure device. 1... Deflector, 2... Electron beam, 3... Sample, 4... Reference mark. 5... Metal thin film layer, 5'... Insulating thin film layer. 6... Resist, 7... Detector, 8... XY stage, 9... Objective lens, 10... Electric field shield plate, 10A... Opening, 11... Electric field shield plate movement mechanism.

Claims (1)

[Claims] In a charged beam device that irradiates a sample with a charged beam,
A charged beam device characterized in that a conductive body having an opening through which a charged beam passes is provided to cover the surface of the sample.