JPS5981851A - Electron beam annealing device - Google Patents

Abstract

PURPOSE:To aim at improvements in the element characteristic of a device formed on a semiconductor film, by shaping a beam form on a smaple so as to cause at least one spot to have a concave part outward, while making the kinetic direction of the smaple so as to be directed to the opening side of this concave part. CONSTITUTION:A cathode 1 is made up in forming a part of its cylindrical body into a door type notched at 90deg. to the center axis. The form of an electron beam being image-formed on a sample surface 10 is almost identical to the lower end face (radiating end face) of the cathode 1, meaning that a quarter of a circular image is notched into a door type one. This shaped beam is scanned in the opposite direction to an A direction so as to cause the sample surface 10 to relatively move toward the notch part outward (an arrow A direction). With this, the central part of a melting zone is solidified earlier than the outside part, and since the grain boundary produced out of the central part proceeds for both sides, a large crystal grain is secured and, what is better, a single crystal thin film is obtained so that the element characteristic of a semiconductor device can be improved.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to improvements in electron beam annealing equipment.

[Technical background of the invention and its problems]

Recently, an electron beam annealing apparatus has been developed that irradiates a sample with an electron beam and anneals the sample by scanning the beam. By annealing the semiconductor film on the insulator using this equipment, M
The usefulness of electron beam annealing equipment is attracting attention because the characteristics of devices such as transistors (OS) become close to those of devices formed on bulk semiconductors.

An insulator, for example, a 5i02 film, is amorphous, and the polycrystalline Sl film deposited on this SiO□ film by a normal method has a crystal grain size of only a few hundred [X], and is formed on this polycrystalline St. The carrier mobility of a transistor (MOS) is 10 [cm? /v, sec),
Also, the leakage current is large. However, when the polycrystalline SI film is irradiated and scanned with a high energy density electron beam, the SI
melts and recrystallizes as it is scanned. Then, the crystal grain size is several i o o o (X3 to several [μm]), and the carrier mobility of the Mos transistor formed on this is on the order of 100 [cm2/u, nec]. When a Si single crystal is used as a substrate and a polycrystalline Si film is deposited on a 5So2 film with some holes fully opened in the SiO2 and a part of the polycrystalline Si film is in contact with the substrate, the polycrystalline Si melted by the electron beam annealing described above is It solidifies at the part in contact with the Si single crystal and grows epitaxially.When the single crystallization progresses to the molten Si above the 8102 crotch, a single crystal film is obtained.In addition, when a KMO8) Lansostar is formed, the device characteristics are as follows. Closer to that of devices formed on bulk semiconductors. In this way, 5 inch
By melting and solidifying the polycrystalline s1 on the two films, crystal grains larger than the crystal grain size at the time of deposition can be obtained.

However, this type of method has the following problems. That is, although crystal grains of polycrystalline Si grow due to electron beam annealing, the crystal grains remain at a size of about [ltm'3] at most, even though the polycrystalline Si is often melted. Furthermore, even when a part of a multi-crystalline single crystal is brought into contact with a first single crystal, the portion that becomes single crystal extends only about 20 (μm) from the contact area.In other words, in order to improve the characteristics of a semiconductor film on an insulator, However, there are limits to this, and it has not been possible to significantly improve the device characteristics of the semiconductor film formed on the semiconductor film.

[Purpose of the invention]

Purpose of the present invention U1 A semiconductor film such as polycrystalline silicon can be made into a film with excellent characteristics by electron beam annealing,
It is an object of the present invention to provide an electron beam annealing apparatus that can greatly improve the device properties of devices formed on this semiconductor film.

[Summary of the invention]

The gist of the present invention is to improve the beam shape on the sample so that the liquid phase-in-phase boundary is convex toward the liquid phase side with respect to the in-phase. In other words, when electron beam annealing is performed on a sample such as polycrystalline St, the electron beam shape is usually circular (Gaussian distribution), so the molten part solidifies from the outside, and the crystal nuclei start from the sides of the molten part. This was found to be a factor that hinders recrystallization. Therefore, if the liquid phase-solid phase boundary is convex toward the liquid phase side with respect to the same phase so that the reassimilation of the molten zone is directed outward from the center, recrystallization and crystal grain size increase, etc. It becomes effective.

It was also confirmed that the liquid phase-solid phase boundary described above can be realized by selecting the beam and shape on the sample.

Focusing on these points, the present invention focuses and accelerates an electron beam emitted from an electron emitter and irradiates it onto a sample, and also moves the beam and the sample relatively to generate electrons that anneal the sample. In the beam annealing device, the beam shape on the sample is shaped so that it has at least one concave portion outward, and the direction of movement of the sample with respect to this shaped beam is directed toward the open side of the concave portion. It is something.

Further, in the present invention, the beam intensity on the sample is controlled so that the beam intensity on the sample is stronger at the outer periphery than at the center.

〔Effect of the invention〕

According to the present invention, the liquid phase-solid phase boundary of a sample formed by electron beam annealing can be made convex toward the liquid phase side with respect to the solid phase. Therefore, when a polycrystalline S1 film on an insulator or the like is used as a sample, resolidification of the melted portion occurs from the center toward the outside. In other words, since the grain boundaries included in the resolidified portion extend toward the outside of the melted portion, only a single crystal is selected, and a long single crystal film can be obtained. That is, a semiconductor film such as polycrystalline St can be made into a film with excellent characteristics by electron beam annealing, and it is possible to improve the device performance of a device formed on this semiconductor film.

[Embodiments of the invention]

FIG. 1 is a schematic configuration diagram showing an electron beam annealing apparatus according to the first embodiment of the present invention. In FIG. 2, 1 is a cathode (electron emitter) made of tungsten;
is formed by cutting a part of a cylindrical body with a diameter of 2 [spaces] into a 9o0 sector shape with respect to the central axis. Further, the cathode 1 is arranged so that its central axis coincides with the optical axis of an optical system, which will be described later, and can be rotated about the entire optical axis. A tungsten wire 2 having a diameter of 0.5 mm is welded to the upper part of the cathode 1, and a filament 3 for heating the cathode 1 is provided around the outer periphery of the cathode 1.

Further, in the figure, a Wehnelt electrode 5 is used to control the entire electron beam emitted from the 4Fi cathode 1, and 5 is an anode for accelerating the electron beam.
An electron gun is composed of a filament 3, a Wehnelt electrode 4, an anode 5, and the like.

Below the electron gun, there is an electromagnetic lens 6.7 for focusing the electron beam, an X direction and a Y direction for deflecting the electron beam.
directional deflection plates 8 and 9 are respectively arranged. The electron beam emitted from the electron gun passes through an electromagnetic lens 6.7
The sample surface 10 is irradiated in a focused manner, and the sample surface 10 is scanned by the deflection plates 8 and 9.

The shape of the electron beam imaged on the sample surface 1o of cocoa is almost the same as the lower end surface (radiation end surface) of the cathode 1, and as shown in FIG. It becomes what it is. This shaped beam is scanned in a direction opposite to the input direction so that the sample surface 1o moves relative to the outside of the notch of the beam (in the direction of the arrow in FIG. 2). Note that the beam on the sample surface 10 rotates due to the settings of the electromagnetic lenses 6, 7, etc., but this is corrected by rotating the rotating rJ cathode 1.

When a polycrystalline S1 film was annealed using this apparatus configured as described above, the following results were obtained. First, as a sample, a single crystal Si wafer f wet oxidized L 5
000 CX] no 5Io2BIAk is formed, and a polycrystalline s1 film of 5000 [X) is deposited on this by low pressure CVD method,
Furthermore, on top of this, 10 layers of true pressure CVD Shio#" (?5i02 film)
00 [X] Use the deposited material. The accelerating voltage is]
, 0 [kv], the beam current was 4 to 7 [mA], and the beam diameter at sample-H was ~2500 [μm:1]. The polycrystalline Si film was annealed (one beam scan) under the above conditions, the 5tO2 film on the surface was etched, and the growth of crystal grains in the polycrystalline Si film was investigated. As a result, it was found that a single crystal thin film with a width of about 100 [μm] and a length of several [tones] was obtained.

- When a polycrystalline Si film was annealed under the same conditions as above using a conventional device using a tungsten cylinder with a diameter of 2 Ctrrm as the cathode 1, the crystal grains were at most several [μm] in diameter. . This is because when scanning with a circular electron beam, the shape of the molten pool is circular, and when scanning in a straight line, the outer part of the molten zone solidifies faster than the center. This is because grain boundaries occur on both sides and proceed inward.

On the other hand, when the apparatus of this embodiment is used, the center of the molten zone solidifies faster than the outside, and the grain boundaries generated from the center proceed to both sides, resulting in large crystal grains as described above.
Moreover, a large single crystal thin film can be obtained.

Thus, according to the method of this embodiment, by annealing the polycrystalline S i Jlj'J deposited on an insulator such as an S r 02 film, the crystal grains thereof are increased and recrystallized; ! l) (4) A film with excellent properties can be obtained.

Therefore, the element characteristics of semiconductor devices such as MOS transistors formed on this film can be improved. Furthermore, compared to conventional devices, the present invention has advantages such as being easily realized by simply changing the shape of the cathode 1.

Figures 3(a) and (11) are for explaining the second embodiment, Figure 3(8) is a perspective view showing the cathode configuration, and Figure 3(b) shows the beam shape on the sample. It is a schematic diagram.

This embodiment differs from the first embodiment described above as follows:
Two tungsten cylinders are used in place of the cathode 1 in which a part of the cylinder is cut out. That is, the cathode 1 of the device of this embodiment consists of two tungsten cylinders 11 each having a diameter of 1.5 [■] as shown in FIG.
a.

11b. Each of these tungsten cylinders 11m+11b has an angle of 0.5 [
μm] and are arranged axially symmetrically.

With such a configuration, the shape of the electron beam irradiated onto the sample surface 10 will be the shape of two overlapping circles, as shown in FIG. 3(b). In other words, the two opposing parts of the beam are concave outward. Therefore, the sample surface 10 is on the opening side of the four parts (+11 in the figure).For one sample, SiO□ on a (100)St single crystal substrate
A groove with a width of 3 [μm] was formed in the film in the x110> direction, and the polycrystalline S1 film was heated to 7000 [μm] using the supernatant reduced pressure CVD method.
840□ film of 1500 [x] was further deposited thereon. The conditions such as accelerating voltage and beam current were the same as in the previous example, and the polycrystalline Si film was annealed at a scanning speed of 50 to 15'0 [tM/sec].

As a result, it was found that a single-crystalline film had grown to a length of several trunks on the 8102 film from most of the portion that came into contact with the Si single-crystal in the groove. When this was done using a conventional device, the single crystal film could only extend from the groove by a distance of about 10 [μm].

FIG. 4 is a plan view showing the shape of an aperture mask for explaining the third embodiment. This embodiment differs from the previous first embodiment in that a Gumpel-shaped aperture 12a as shown in FIG. The reason is that the aperture mask 12 having the same diameter is 1N. Furthermore, this "Kalpa combination force, 1?" Therefore, the same effects as in the first embodiment can be obtained.

4,': Figures 5(a) and 5(b) are for fully explaining the fourth embodiment. A schematic diagram showing the beam shape on the sample surface).

This embodiment differs from the previous first embodiment in the following points:
, 'Oso 1'1 is made into a cylindrical shape as shown in Fig. 5 (+1). That is, the diameter of the cathode IFi is 0.7 at the axis of the tungsten cylinder with a diameter of 2.
It is formed by opening a hole of [wn:].

With such a configuration, the illumination irradiated onto the sample surface 10,
The shape of the electron beam is donut-shaped as shown in FIG. 5(b). In other words, the beam intensity on the sample surface 10 is stronger on the outer circumferential side than on the inner side.

When this donut-shaped beam is scanned in one direction, the initially heated area near the center of the scanning area will be cooled and heated again in the beamless or sparse area at the center of the beam, and as a result, the outside area will be heated again. Compared to the inside, the average amount of heating is smaller. Therefore, as in the first embodiment, the middle scanning direction is not defined by the beam shape, so a rotation mechanism or the like for rotating the cathode 1 is not required, and the configuration can be simplified. There are also advantages.

However, the present invention is not limited to the embodiments described above. For example, in the first embodiment, the emission end face of the electron emitter may have a slightly outwardly concave portion at one location. Furthermore, in the third embodiment, the arrangement position of the anomerature mask, the shape of the anomerature, etc. can be changed as appropriate according to the specification C. Furthermore, in the fourth embodiment, the shape of the electron emitter is not necessarily changed. It is not limited to a cylinder, but may be a cylinder with a circular hole centered at its axis at an appropriate depth from the radial end surface side of the cylinder as shown in FIG. 6(a). It is sufficient that the radiation end face shape is donut-shaped.

Furthermore, it is also possible to use a material 22 having a high electron emissivity, such as The2, coated on the outer periphery of a tungsten rod 21 as shown in FIG. 6(b) as the electron emitter. Further, the material of the electron emitter is not limited to tungsten, TlO2, etc., and can of course be changed as appropriate according to specifications. Further, instead of deflecting and scanning the electron beam, the sample may be moved. Furthermore, as a sample &:1: polycrystalline

[Brief explanation of the drawing]

(','l-1: ゛・Figure 1 is a schematic configuration diagram showing the electronic video recorder according to the first embodiment of the present invention. Figure 2 is a schematic diagram showing the configuration of the electronic video recorder according to the first embodiment of the present invention. The schematic diagrams shown in FIGS. 3(a) and 3(b) are for fully explaining the second embodiment, and FIG. 3(at) is a perspective view showing the shape of the electron emitter, and FIG. FIG. 4 is a schematic diagram showing the third embodiment, and is a plan view showing the shape of the groove mask, and FIG.
b) is for explaining the fourth embodiment, and Fig. 5(a)
) is a perspective view showing the shape of the electron emitter, FIG. 5(b) is a schematic diagram showing the beam shape, and FIGS. 6(a) and (b) are for explaining modified examples, and each shows the shape of the electron emitter. FIG. 1... Cathode (electron emitter), 2... Tungsten thin, 3... Filament, 4... Wehnelt N
4'&, 5... Anode, 6, 7... Electromagnetic lens,
8, 9... Deflection plate, 10... Sample surface, Iln, Ilb
...Tungsten cylinder, 12...Aperture mask. Applicant Director of the Agency of Industrial Science and Technology Ishizaka g+, t-1st
Figure 2 Figure 3 Figure 4 Figure 2 1 (a) (a) Figure 5 (b) Figure 6 (b)

Claims (9)

[Claims] (1) A means for focusing and accelerating an electron beam emitted from an electron emitter and irradiating it onto a sample, and shaping the beam shape so that the beam shape on the sample has at least one concave portion outward. and means for relatively moving the sample and the beam so that the direction of interlocking of the sample with respect to the shaped beam is toward the open side of the recess of the beam. Device. (2) The means for shaping the beam shape is characterized in that the electron emitter is one whose radiation end face has at least one outwardly concave portion. Electron beam annealing equipment. (3) The means for completely shaping the beam shape uses two electron emitters having circular or polygonal radiation end faces as the electron emitters, and arranges these electron emitters in a symmetrical FC% with respect to the optical axis. The special ivF is that the
An electron beam annealing apparatus according to claim 1. (4) The electron beam annealing apparatus according to claim 2 or 3, wherein the electron emitter is rotatably provided around an optical axis. (5) The means for shaping the beam shape includes an aperture mask that defines the shape of the beam on the path of the electron beam, and a portion of the aperture mask that is concave outward in at least one place. An electron beam annealing apparatus according to claim 1, wherein the electron beam annealing apparatus has: (6) The electron beam annealing apparatus according to claim 5, wherein the aperture mask has a dumbbell-shaped aperture. (7) A means for focusing and accelerating the electron beam emitted from the electron emitter and irradiating it onto the sample, and a means for controlling the beam intensity so that the beam intensity on the test slope is stronger at the outer periphery than at the center. and means for relatively moving the controlled beam and the sample. (8) The electron beam annealing apparatus according to claim 7, wherein the means for controlling the beam intensity is to use a cylindrical object as the electron emitter. (9) The means for controlling the beam intensity is to use, as the electron emitter, an object whose electron emissivity at its radiation end face is higher at the outer local part than at the central part. The electron beam annealing device described. Claim 9: The electron emitter is a cylindrical first electron emitter with a second electron emitter having a higher % emittance than that of the first electron emitter coated on the outer periphery of the first electron emitter. The electron beam annealing device described.