JP2003191200A - Ge3N4 NANO BELT AND METHOD OF MANUFACTURING IT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new Ge<SB>3</SB>N<SB>4</SB>nano belt, which will become very useful in the future of semiconductor nano technology and method of manufacturing the Ge<SB>3</SB>N<SB>4</SB>nano belt. <P>SOLUTION: This Ge<SB>3</SB>N<SB>4</SB>nano belt has not a circular but a square cross section and long length and includes Ge<SB>3</SB>N<SB>4</SB>. This method comprises a step of mixing the powder of Ge and SiO<SB>2</SB>, and a step of covering this mixed powder with activated carbon particles, a step of heating the mixed powder with activated carbon particles in NH<SB>3</SB>atmosphere to make it grow into a form of Ge<SB>3</SB>N<SB>4</SB>nano belt and a step of cooling Ge<SB>3</SB>N<SB>4</SB>having a form of belt. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a Ge ₃ N ₄ nanobelt and a method for producing the same. More specifically, the present invention provides a novel Ge ₃ N useful for future semiconductor nanotechnology applications.
₄ Nanobelt and its manufacturing method.

(Prior Art) Germanium Nitride (Ge ₃
N ₄ ) is an important dielectric material in semiconductor technology. This is a promising material that is expected to develop in high performance complementary metal oxide semiconductor (CMOS) germanium devices, replacing the GeO ₂ material, which has the fatal weakness of being soluble in water. is there. This Ge ₃ N ₄ has been integrated in a metal oxide semiconductor (MOS) device including a MOS field effect transistor (MOSFET) to date, and can withstand a rapid thermal anneal (RTA) temperature and generate heat. Ge ₃ N ₄ -InP, Ge ₃ are advantageous because of their lowness, negligible hysteresis, and low current drift.
N ₄ -GaAs metal - insulator - are manufactured as semiconductor field effect transistor (MISFET).

In such materials, Ge ₃ N ₄ is
It is manufactured as a two-dimensional thin film. However, Ge ₃ N ₄
For the production of one-dimensional (ID) nanoscale materials
No one has reported yet. Perhaps because of the generally low interest in ID nanoscale dielectric materials, studies of Ge ₃ N ₄ ID nanoscale materials have been neglected.

As is well known, numerous studies on ID nanoscale materials have been stimulated by the pioneering work of carbon nanotubes (CNTs) in 1991. And, since _{then, BN, WS 2, B x} C y N z
Besides nanotubes consisting of MoS ₂ and MoS ₂ , various other solid state ID nanoscale materials have been synthesized and studied. These are high temperature superconducting (HTSC) materials, such as the HTSC material yttrium-barium-copper-.
Oxides and related MgO nanorods, magnetic Fe nanowires, conductor Pt nanoscale networks, hard materials SiC, Si ₃ N
₄ nanorods. Furthermore, S which is a semiconductor material
i, Ge, GaN, GaAs, ZnO, SnO ₂ , In
₂ O ₃ and CdO nanowires and nanobelts have also been investigated.

In addition to scientific interest, these 1D nanoscale materials were manufactured with the belief that they would be useful for various applications in future nanotechnology. And similarly, Ge ₃ N, which can be applied in various ways by future nanotechnology,
Realization of ₄ 1D nanoscale materials is expected.

Therefore, the present invention solves the above problems and is extremely useful in future semiconductor nanotechnology, and is a novel 1D nanoscale material Ge ₃ N ₄ nanobelt and production of this Ge ₃ N ₄ nanobelt. It is intended to provide a way.

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention firstly includes Ge ₃ N ₄ having a belt shape having a long cross section that is a quadrangle rather than a circle. Ge ₃ N ₄ nanobelts are provided.

Secondly, the present invention has a width of 30 to 300.
Ge ₃ N according to the first invention, which is in the range of nm, has a thickness of 150 nm or less, and has a length of 1 μm or more.
Provide ₄ nanobelts. Thirdly, the present invention relates to the Ge
₃ N ₄ includes α-Ge ₃ N _{4 and} has a (0001) plane

There is provided a Ge ₃ N ₄ nanobelt according to the first or second invention, wherein the angle between and is 92 °. In the fourth aspect of the present invention, the Ge ₃ N ₄ is β-Ge ₃ N.
₄ wherein the angle between the belt-axis direction and the [0001] direction, which is the 7 °, Ge for the first or second aspect of the present invention
Provide a ₃ N ₄ nanobelt.

A fifth aspect of the present invention is a method for manufacturing a Ge ₃ N ₄ nanobelt, which comprises mixing Ge and SiO ₂ powder, covering the mixed powder with activated carbon particles, and covering with activated carbon particles. A method is provided that includes the steps of heating the mixed powder thus obtained to grow Ge ₃ N ₄ into a belt shape, and cooling the Ge ₃ N ₄ having a belt shape.

In the sixth aspect of the present invention, Ge and SiO
_A method for producing a Ge ₃ N ₄ nanobelt according to the fifth invention, wherein the mixing ratio with ₂ is 1 to 1.2: 1 by weight. The present invention, in the seventh, heating is carried out for 1 hour or more at eight hundred to eight hundred sixty ° C., to provide a _Ge 3 _{N 4} nanobelts manufacturing method of the related invention of the fifth or sixth. In the eighth aspect of the present invention, the NH ₃ atmosphere is 100 to 400 cm.
³ / is the partial NH ₃ flow of, to provide a method for manufacturing a fifth to seventh _Ge 3 _{N 4} nanobelt for any of the present invention.

Detailed Description of the Invention G provided by the present invention
The e ₃ N ₄ nanobelts include Ge ₃ N ₄ having a rectangular cross section rather than a circular cross section and having a long belt shape. More specifically, this Ge ₃ N ₄ nanobelt is a belt-shaped Ge ₃ N ₄ having a width in the range of 30 to 300 nm and a thickness of 150 nm.
And the length is 1 μm or more. And this Ge ₃ N ₄ nanobelt is Ge + Si
It can be manufactured by thermally reducing a mixed powder of O _{2 in} an NH ₃ atmosphere. The features of the Ge ₃ N ₄ nanobelt of the present invention will be described below together with the description of the method for producing the Ge ₃ N ₄ nanobelt of the present invention.

The method for producing a Ge ₃ N ₄ nanobelt according to the present invention comprises a step of mixing Ge and SiO ₂ powder, a step of covering the mixed powder with activated carbon particles, a step of heating them in an NH ₃ atmosphere, and a step of cooling. Is included.

Various devices were used to synthesize the Ge ₃ N ₄ material,
For example, a horizontal furnace as illustrated in FIG. 5 can be used. In this device of FIG. 5, the diameter is ˜2 cm and the length is ˜2.
A cm3 boron nitride (BN) crucible (4) is installed in the center of the furnace (1). The device is also provided with a heating coil (4), such as a low or high frequency coil, an inlet pipe (2) at one end and an outlet pipe (3) at the other end. ing.

In the first step of the process of the invention, the starting Ge and SiO ₂ powders are homogeneously mixed in a weight ratio of ˜1.2: 1, more preferably 1 to 1.2: 1. Mixed. This Ge + SiO ₂ mixed powder (5) is put into a BN crucible (4) as shown in the lower part of FIG. Then, in the second step, the Ge + SiO ₂ mixed powder (5) is used as a thin layer (6) of activated carbon powder, preferably high-purity activated carbon powder, and more preferably containing C nanoparticles. Try to cover.

In the third step, the Ge + SiO ₂ mixed powder (5) having a thin carbon layer (6) is heated in an NH ₃ atmosphere to grow Ge ₃ N ₄ into a belt shape. Cool Ge ₃ N ₄ with shape. More specifically, a stream of NH ₃ is introduced into the furnace (1) through the inlet pipe (2) for a sufficient time prior to heating to drive O ₂ out of the furnace (1). Then G with a thin carbon layer (6)
The e + SiO ₂ mixed powder (5) is heated in an NH ₃ atmosphere. In the present invention, heating at 800 to 860 ° C. for 1 hour or longer is a standard. Further, as particularly preferable heating, under a NH ₃ gas stream of 300 cm ³ / min, at 850 ° C. for 2 hours.
Time heating is illustrated. In the cooling step, NH ₃ is kept flowing until Ge ₃ N ₄ having a belt shape is completely cooled to, for example, room temperature.

As a result, on the surface of the thin carbon layer, Ge ₃ N ₄ with a belt shape can be seen as a white hard skin. Then, the thin carbon layer is dispersed in a solvent such as alcohol to obtain the Ge ₃ N ₄ nanobelt of the present invention as a deposit.

In the present invention, Ge ₃ N ₄ nanobelts are considered to be obtained by thermal reduction based on the following reaction.

In the method of the present invention, GeO which is a volatile substance is generated by the following reaction, and Ge (solid) + Si
O ₂ (solid) → GeO (vapor) + SiO (solid), and this GeO then reacts with NH ₃ gas on the C nanoparticle site to grow a Ge ₃ N ₄ nanobelt. This method does not require a CNT template, but does require Ge ₃ N ₄ precipitation sites provided by C nanoparticles.

In the obtained Ge ₃ N ₄ nanobelt, the ideal α phase of Ge ₃ N ₄ (P31c, a = 0.8)
202 nm, c = 0.5941 nm) and β phase (P6
3 / m, a = 0.038 nm, c = 0.3074n
The presence of slightly different phases was identified from m).

This Ge ₃ N ₄ nanobelt was deposited on a Cu mesh to prepare a transmission electron microscope (TEM) sample. The TEM sample was observed with a 300 kV field emission analysis electron microscope (JEM-3000f) equipped with an X-ray energy dispersive spectrometer (EDS).

There were many Ge ₃ N ₄ nanobelts as 1D nanoscale materials in this sample. It was confirmed that these had a width within the range of 30 to 300 nm and a length of several μm or more as described above. Figure 1
(A) shows three different lengths of 1D nanoscale material, designated as A, B, and C, respectively. It was found that rotating these about their axis changes their projected width. From this it can be concluded that these 1D nanoscale materials have a square cross section rather than a circular cross section perpendicular to their axis. The contrast and shape observed for this 1D nanoscale material is that of SnO ₂ nanobelts (Hsu,
W. K. et al. Electrochemica
l formation of novel nano
wires and ther dynamics
ffects. Chem. Phys. Lett. 28
4,177-183 (1998)), this 1D nanoscale material can be recognized as a nanobelt. Furthermore, the ratio of thickness to width of this 1D nanoscale material can be estimated to be ˜1: 2, with almost all nanobelts having a thickness of 150 nm or less. Further, EDS analysis of these three nanobelts revealed that the three nanobelts contained only Ge and N, as shown in the EDS spectrum of FIG. 1 (b). Here, the Cu peak is generated from the Cu lattice as the carrier. Together with other analysis results, this 1D nanoscale material was confirmed to be a Ge ₃ N ₄ nanobelt composed of a Ge ₃ N ₄ single crystal. 10
ED by randomly selecting more than ₃ Ge ₃ N ₄ nanobelts
When examined by S analysis, all EDS spectra are almost the same as in FIG. 1 (b).

FIG. 2A shows Ge ₃ in FIG. 1A.
Figure ₄ shows a dark field image of N4 nanobelt A, which is in the electron diffraction (ED) pattern shown in Figure 2 (b).

Is utilized. This is α-Ge ₃ N ₄
of

It is identified by And

The measured spacing d of 0.702 nm and 0.453 nm are in agreement with the ideal values for α-Ge ₃ N ₄ of 0.710 nm and 0.456 nm. The belt axis is

Perpendicular to. Also, the fact that the bright region is small is due to the fact that in other regions of the Ge ₃ N ₄ nanobelt

It is thought that this is due to the distortion of
In other areas

Is believed to be linked to the effect that does not conform to Bragg's law. The change in contrast is due to the Ge ₃ N ₄ nanobelt being curved under the irradiation of the electron beam.

FIG. 3 shows a high resolution transmission electron microscope (HRTEM) image of a Ge ₃ N ₄ nanobelt B having an α phase. The inset is

It is the ED pattern of In this ED pattern, it was observed that each spot had stripes along the direction of the arrow. This phenomenon is caused by the nanobelt shape effect (P. Hirsh, A. Howie, R. et al.
B. Nicholson, D.M. W. Pashley &
M. J. Whelan, Electron Micro
oscopy of Thin Crystals (L
ondon, Butterworths, 1967)
p. 98. ), The direction of extension of this stripe is

It is perpendicular to the nanobelt axis perpendicular to. Y. L. Li et al.

A belt axis direction perpendicular to can be found in the α-Si ₃ N ₄ whiskers having a similar structure,
This is the closest packing

It has been described that the result is a growth perpendicular to (Jour. Mater. Sci. 31, 26).
77 (1996)). this

The distance d between the and (0001) plane is 0.71.
0 nm and 0.595 nm, which are the ideal values for α-Ge ₃ N ₄ 0.710 nm and 0.5, respectively.
It agrees with 94 nm. However, with the (0001) plane

The angle between the two is 92 °, and α-Ge ₃ N
The difference from the ideal value of 90 ° of ₄ is 2 °. α-G
Such a phenomenon of the e ₃ N ₄ material has never been reported. However, the same phenomenon was observed only in α′-SiAlON, and in this case, the (0001) plane

The angle formed by and is 91 °. The cause of this phenomenon has not been clarified. Dong et al. Have reported that for certain β-Ge ₃ N ₄ materials, the N-Ge-N bond angle is 104 ° -111 °, but Ge-N ^6h -Ge.
The bond angle is reported to be 114 ° or 123 °. Such a value is the ideal N
-Ge-N bond angle of 109.5 ° and ideal Ge-
It is slightly different from 120 ° in N ^6h -Ge bond angle. 9 in the α-Ge ₃ N ₄ nanobelt of the present invention
The angle of 2 ° is the N-Ge-N bond angle and Ge-N.
It is believed that the −Ge bond angles are slightly offset from the ideal values of 109.5 ° and 120 °, respectively.

FIGS. 4 (a) and 4 (b) respectively show β-
₃ shows the shape and HRTEM image of Ge ₃ N ₄ . The inset of (b) is

It is the ED pattern in.

The spacing d corresponding to and 0001 reflections is
They are 0.700 nm and 0.309 nm, respectively.
These are respectively the ideal spacing d of β-Ge ₃ N _4.
Which is 0.696 nm and 0.307 nm. The belt axial direction differs from the [0001] direction by only 7 °. Then, on the surface of the Ge ₃ N ₄ nanobelt, as shown by the symbol S, some step-like steps are present. Based on these HRTEM observations, it is suggested that the Ge ₃ N ₄ nanobelt has a growth mechanism as shown in FIG. 4 (c). That is, although the growth of the Ge ₃ N ₄ nanobelt is along the [0001] direction, at the Ge ₃ N ₄ precipitation stage,
The precipitation surface of e ₃ N ₄ is

There is a slight but continuous movement along.

With respect to the synthesized material, no metal nanoparticles were found at the tip of the Ge ₃ N ₄ nanobelt and Si ₃ N ₄ nanobelt was used.
_{No 3} N ₄ material was also found. Based on the above observations, it is hypothesized that the Ge ₃ N ₄ nanobelts of the present invention result from a two-step process. That is, in the first step, GeO vapor is generated by the following reaction.

Ge (solid) + SiO ₂ (solid) → GeO
(Vapor) + SiO (Solid) Then, the generated GeO vapor approaches the surface of the C nanoparticles, and the Ge-vapor is generated by the following vapor-vapor-solid (VVS) reaction.
Crystal nuclei of e ₃ N ₄ are generated.

3GeO (steam) + 4NH ₃ (steam) +3
C (solid) → Ge ₃ N ₄ (solid) +3 CO (steam) +6
H ₂ (steam) Ge ₃ by the subsequent steam-steam (VV) reaction
Growth of along the axis on the N ₄ nucleus occurs.

3GeO (steam) + 4NH ₃ (steam) → G
e ₃ N ₄ (solid) + 3H ₂ O (steam) + 3H ₂ (steam) This VV reaction has a difference in volume Gibbs energy difference for the production of 1 mol of Ge ₃ N ₄ at 850 ° C. as compared with the VVS reaction. Only -201KJ larger. Therefore, if only the Gibbs energy of volume is taken into consideration, the VV reaction will become dominant and the VV reaction will play a dominant role in the growth of Ge ₃ N ₄ nanobelts. On the other hand, VVS
If only the reaction takes place in-situ on the C nanoparticles, only fine Ge ₃ N ₄ nanoparticles of about the same size as the C nanoparticles will be obtained. However, when considering the surface Gibbs energy, C
Since the nanoparticles have a large surface area and a high surface Gibbs energy, the VVS reaction becomes dominant and fine Ge ₃ N
₄ nuclei are easily generated. In general, nanobelt growth is not disturbed along the belt axis, and the degree of supersaturation on the sides of the nanobelt is sufficiently low that nanobelt growth is impeded in a direction perpendicular to the belt axis. ing. In this theory, the fact that the Ge ₃ N ₄ nanobelts in FIGS. 2 (a) and 3 have different axial directions is believed to be due to sufficiently low supersaturation on their different sides.

The Ge ₃ N ₄ nanobelt of the present invention is a novel dielectric material Ge ₃ N ₄ having a 1D nanoscale structure and the above-mentioned properties, for important applications for semiconductor nanotechnology in the future. It will be extremely useful.

[Brief description of drawings]

FIG. 1 (a) shows the morphology of nanobelts A, B, and C, and (b) shows the EDS spectrum of nanobelt A, where N-Kα (0.39 ke
V), Ge-Lα (1.19 keV), Ge-Kα
(9.88 keV) and Ge-Kβ (10.98 keV)
The peak in V) is labeled. The Cu peak is
It is generated from the Cu lattice of the carrier.

FIG. 2 (a) shows the ED pattern shown in FIG. 2 (b). The dark field image of Nanobelt A using is illustrated, (b)
Shows the ED pattern from the bright region in (a) on the left side. The right part of the simulated α-Ge ₃ N ₄ Is.

FIG. 3 shows an HRTEM image of Belt B. The angle between two planes with d-spaces of 0.710 nm and 0.595 nm is 92 °. Inset is It is an ED pattern in. The arrow indicates the direction of the stripes at the reflected spot.

FIG. 4 (a) illustrates the morphology of β-Ge ₃ N ₄ nanobelts, and (b) shows HRTEM images of nanobelts. There is a small angular difference of 7 ° between the belt axis and the [0001] direction, and there are some steps marked S. (C) shows the growth diagram of the nanobelt and the difference between the belt axial direction and the [0001] direction.

[Procedure amendment]

[Submission date] May 22, 2002 (2002.5.2)
2)

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 (a) shows the morphology of nanobelts A, B, and C, and (b) shows the EDS spectrum of nanobelt A, where N-Kα (0.39 keV), G
e-Lα (1.19 keV), Ge-Kα (9.88 k)
eV) and Ge-Kβ (10.98 keV) peaks are labeled. The Cu peak is generated from the Cu lattice of the carrier.

FIG. 2 (a) shows the ED pattern shown in FIG. 2 (b). The dark field image of Nanobelt A using is illustrated, (b)
Shows the ED pattern from the bright region in (a) on the left side. The right part shows the simulated α-Ge ₃ N ₄ Is.

FIG. 3 shows an HRTEM image of Belt B. The angle between two planes with d-spaces of 0.710 nm and 0.595 nm is 92 °. Inset is It is an ED pattern in. The arrow indicates the direction of the stripes at the reflected spot.

FIG. 4 (a) illustrates the morphology of β-Ge ₃ N ₄ nanobelts, and (b) shows HRTEM images of nanobelts. There is a small angular difference of 7 ° between the belt axis and the [0001] direction, and there are some steps marked S. (C) shows the growth diagram of the nanobelt and the difference between the belt axial direction and the [0001] direction.

FIG. 5: Manufacturing of Ge ₃ N ₄ nanobelts of the invention of this application
As an example of a device that can be used,
It is a schematic cross-sectional view.

[Explanation of symbols] 1 furnace 2 inlet pipe 3 outlet pipe 4 Boron nitride crucible 5 Ge + SiO ₂ mixed powder 6 carbon layer 7 heating coil

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G077 AA01 AA10 BE11 DB28 DB30                       HA20 TA02

Claims (8)

[Claims] 1. A Ge ₃ N ₄ nanobelt comprising a belt-shaped Ge ₃ N ₄ having a quadrangular shape instead of a circular shape and a long length. 2. The width is in the range of 30 to 300 nm,
The Ge ₃ N ₄ nanobelt according to claim 1, having a thickness of 150 nm or less and a length of 1 μm or more. 3. A (0001) plane containing α-Ge ₃ N ₄ and Ge _{3 according to} claim 1 or 2, wherein the angle between and is 92 °.
N ₄ nanobelt. 4. The Ge ₃ N ₄ nanobelt according to claim 1 or 2, comprising β-Ge ₃ N ₄ , wherein the angle between the belt axial direction and the [0001] direction is 7 °. 5. A step of mixing Ge and SiO ₂ powder, a step of covering the mixed powder with activated carbon particles, a step of heating the mixed powder covered with the activated carbon particles to grow Ge ₃ N ₄ into a belt shape, And a method for manufacturing a Ge ₃ N ₄ nanobelt, which includes a step of cooling Ge ₃ N ₄ having a belt shape. 6. The mixing ratio of Ge and SiO ₂ is 1 by weight.
˜1.2: 1 Ge _{3 of} claim 5 characterized in that
N ₄ Nanobelt manufacturing method. 7. The method for producing a Ge ₃ N ₄ nanobelt according to claim 5, wherein the heating is carried out at 800 to 860 ° C. for 1 hour or more. 8. The NH ₃ atmosphere is 100 to 400 cm.
^The method for producing a Ge ₃ N ₄ nanobelt according to any one of claims 5 to 7, wherein the NH ₃ flow is ³ / min.