JPH0864525A - Crystal grain forming method and semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] Providing a technology to form ultra-fine crystal grains of 10 to 40 Å and enabling the production of highly reliable single-electron devices and Si light-emitting devices with short-wavelength emission. Especially. [Structure] By depositing a material element while maintaining the substrate temperature at a lower temperature equal to or lower than the lower limit temperature of the crystal phase deposition, ultrafine particles are deposited. The amorphous fine particles are heat-treated at a temperature equal to or higher than the crystallization temperature to be crystal fine particles. A semiconductor device of the present invention has a structure in which the above-mentioned crystal fine particles are sandwiched by an insulating thin film and further sandwiched by a conductive material. By applying a voltage between the conductive materials, a current is injected into the crystal fine particles by a tunnel current to obtain a light emitting operation. [Effect] A large-capacity, high-speed, low-power-consumption LSI that uses a single electronic element and a blue-green light element can be used to realize an optical / electric fusion system for large-volume data transfer / processing. Become.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming crystal grains on a different material, and more particularly to a method for forming fine crystal grains having a quantum size effect. The present invention also relates to a semiconductor device used alone or mounted on a Si integrated circuit as a light emitting element for optical interconnect.

[0002]

2. Description of the Related Art Large scale integrated circuit (L) which is a subsystem of electronics.
(SI) has dramatically improved the performance of large capacity, high speed, and low power consumption by miniaturizing the elements. However, miniaturization is now regarded as the limit of the operating principle of conventional devices.
We have reached the point where we can see the wall of μm. 0.1 μm
After that, an electronic element having a new operating principle must play a role in the development of the LSI. The new device utilizes the quantum size effect that appears in the hyperfine structure, and in particular, due to the simplicity of its principle, it uses the Coulomb blockade phenomenon that appears in minute crystal grains with a size of 100 Å or less. One electronic device is the main focus. Recently, many results of theoretical calculations and principle experiments on single-electron devices have been reported,
The progress is remarkable. However, development of element manufacturing technology is also essential for this element to support new industries. This field is still in its infancy. The inventors
Previously, a technique for forming fine crystal grains by the migration of Si atoms generated on SiO2 and the subsequent aggregation phenomenon was reported.

A new important swell in the future trend of electronics is the fusion of electronic circuits and optical communication. Bi-directional mass transmission of data by optical fiber and data processing by high-speed LSI
It becomes a daily scene both at work and at home. At that time, an optical / electrical conversion element is required at the connecting portion between the LSI and the optical cable. A typical GaAs-based compound semiconductor element is used as the light-receiving / emitting element, but cannot be mounted on SiLSI, which is the mainstream of electronic circuits. This is because Si and GaAs are in a dopant relationship with each other and are chemically incompatible. Therefore,
A photoelectric conversion element using Si is required. The Si light receiving element has a history of development so far, and has been put to practical use such as a photo diode and a photo transistor. However, with respect to light emission, it is difficult to realize since Si has an indirect transition type band structure, and research and development have finally started in recent years when the visible light emission of porous Si was discovered. Porous Si is obtained by the worm-eating phenomenon of Si that occurs during anodization, and it can be obtained by the Japanese Journal of Applied Physics.
Physics 31 (1992) L1219 to L1222, diameter 1
It consists of 50-280Å particles of SiO2, in which
Si having a diameter (50-80 Å) about 1/3 that of SiO2 grains
Grains are included. Since the size of Si particles is extremely small, 100 Å or less, the band structure is directly shifted to the transition type by the quantum size effect, and light emission is possible. In this anodization method, the size of Si grains is consequently controlled by the formation current density. For this reason, it is difficult to control and form particularly minute Si particles of 10 to 40 Å which are necessary for light emission in a high frequency band, that is, a short wavelength band of blue to green, which is desirable for mass data transfer.

[0004]

A single electronic device is (e *
e) / 2C (C; electrostatic capacity of fine particles, e; elementary charge) is kT
Stable operation when larger than (T = 300K). The smaller the grains are, the smaller C is. According to the calculation, 10 to 80 Å is the applicable range for device operation. However, especially when reliability is required, the difference between (e * e) / 2C and kT needs to be sufficiently large, and 10 to 40 Å is the particle size range that can meet this requirement. On the other hand, in the Si light emitting device, the particle size corresponds to the emission wavelength, and for blue to green emission, 10 to 40 Å of Si is used.
Fine particles are required. In any case, a technique for forming Si particles with an extremely small diameter of 10 to 40 Å is required.

The crystal grain forming technique previously reported by the present inventors is to deposit crystal grains of a desired size by controlling the substrate temperature and the deposition rate of Si. Lower the substrate temperature (however, the lower limit is 240 ° C at which Si is deposited in the crystalline phase),
If the deposition rate is increased, it is possible to form Si crystal grains of 10 to 40 Å. However, problems such as in-plane uniformity and manufacturing equipment arise when forming fine particles having a particularly small size.

[0006] For example, if it is attempted to form 20Å fine particles at intervals of 20Å, about 2Å will be deposited in terms of the film thickness of a continuous film. 1Å / sec. (See Fig. 1, 850
If it is deposited at (° C.), the deposition time is 2 seconds.
By the way, if the beam shutter is opened and closed to start and stop the deposition, the cross-sectional shape of the Si irradiation beam is asymmetrically deformed as the shutter crosses. During this time, the Si irradiation on the substrate becomes non-uniform, and the in-plane uniformity of the deposition amount deteriorates. If the open / close transition time is sufficiently shorter than the steady irradiation time, this problem can be ignored. However, even if the transition time is at most 0.3 seconds, if the deposition time is as short as 2 seconds, the proportion of the transition time reaches 30%, and in fact, it cannot be ignored.

[0007] Usually, the substrate is rotated during the deposition in order to make the film thickness uniform in the surface of the substrate, but in order to achieve the uniformization, at least one rotation must be performed by the end of the deposition. This corresponds to a rotation speed of 30 rpm for a deposition time of 2 seconds. Actually, about 10 rotations are necessary to make the homogenizing effect sufficiently work, and a rotation speed of 300 rpm is necessary. 300 rpm is a high rotation speed for a vacuum drive device, and in this case, there is a problem that the frequency of failure of the device increases.

To avoid these problems, a technique capable of depositing Si particles at a lower speed is required. In the conventional method, when the deposition rate is slowed, the migration length of Si atoms becomes long and the crystal grain size becomes large.
It is not possible to deposit very small particles of ~ 40Å.

An object of the present invention is to produce a highly reliable single-electron device and a blue to green light emitting Si light emitting device.
It is to provide a technique for controlling and forming crystal grains with an extremely small size of up to 40 Å. Further, regarding the Si light emitting element, an element structure utilizing the fine particles formed in the present invention is also provided.

[0010]

[Means for Solving the Problems] The means of the present invention for forming extremely fine crystal grains of 10 to 40 Å by low-speed deposition of 1 Å / sec. Or less is as follows. First, the substrate temperature is lowered to the lower limit temperature of crystal phase deposition (240 ° C.) or less, and amorphous Si fine particles are deposited. Next, the crystallization temperature (240
(.Degree. C.) or higher, and this is crystallized.

Further, in order to form a light emitting device using the fine particles formed in the present invention, the following structure is constructed. That is, 10
A very small crystal grain of ~ 40 Å is sandwiched by a thin insulating film, and a conductive material is sandwiched between them. By applying a voltage between the conductive materials in this structure, a light emission phenomenon is caused in the fine particles. For the light emitting element, one that emits light in the cross section of the element (usually the cleaved surface of the substrate) and from the electrode side (the plane of the substrate)
Some take out light. In the latter case, transparent materials are used for the insulating film and the conductive material on the extraction side.
The fine particle layer may be a single layer or a plurality of layers.

[0012]

[Function] Regarding means for forming ultra-fine crystal grains of 10 to 40 Å by low-speed deposition.

In the manufacturing method of the present invention, while heating the insulating film on which the fine particles are placed to a desired temperature, atoms or molecules consisting of the constituent elements of the fine particles are supplied from the gas phase. By raising the temperature of the insulating film, thermal energy is given to the constituent elements supplied on the film, and migration on the film (migration) and aggregation of elements encountered as a result of migration are possible. FIG. 1 shows the migration length of Si atoms on the film surface as a function of the substrate temperature when the surface of the SiO 2 film is irradiated with Si atoms. Since agglomeration occurs and Si particles are generated at the time when the migration is completed, the migration length roughly corresponds to the generation interval of Si particles, and also corresponds to the particle size when Si particles are grown to the full interval.

As shown in FIG. 1, the migration length changes depending on the substrate temperature and the migration species supply rate (deposition rate). Since lowering the substrate temperature reduces the energy supplied for migration,
Migration length is reduced. Supply rate (deposition rate)
If the value is increased, the number of migration species existing per unit area increases, and the probability of encountering each other increases. The migration length is also shortened because other migration species meet and coalesce into agglomerates within a short distance to stop the migration. The conventional method is to use the substrate temperature and the deposition rate to deposit crystal grains of a desired size. In this method, there is a lower limit to the temperature at which the crystalline phase is deposited, so that it is difficult to ignore when attempting to form fine particles with an extremely small size, as described above. For reference, the deposition condition region of the conventional method is shown as a light gray region (region 1) in FIG.

In the present invention, Si is deposited by further lowering the substrate temperature below the lower limit temperature of crystal phase deposition. By doing so, as shown in FIG. 1, the migration length can be sufficiently shortened even at a low deposition rate. (The deposition condition region of the present invention is a region (region 2) shown in dark gray in FIG. 1. Of the characteristic lines, the portion falling within this region is the deposition condition. The minimum unit of crystal structure Areas with a migration length shorter than the lattice constant, which is the size of, are not used for the deposition of fine grains, because grains smaller than the minimum crystal structure are deposited and cannot be crystallized). However, since the temperature is lower than the crystallization temperature, it is not possible to obtain crystal grains only by the deposition process as in the conventional method. The fine particles are deposited in an amorphous state. By performing heat treatment at a temperature equal to or higher than the crystallization temperature after the deposition, solid phase growth occurs and the amorphous fine particles transition to a crystalline phase.

About the action in the light emitting device using the crystal grains of extremely small size of 10 to 40 Å.

By forming a thin insulating film, a tunnel current flows in the film when a voltage is applied to a conductive material (used as an electrode) sandwiching the insulating film. Since the insulating film sandwiches the extremely fine crystal grains, the tunnel current flows through the potential well of the fine grains.
That is, an electric current is injected into the fine particles. If carriers are injected into the potential well, carrier recombination occurs. At this time, since the fine particles shift to a direct transition type band structure due to the quantum size effect, mainly photons, that is, light are emitted by recombination. If a transparent insulating film or electrode is used, light is emitted through these films, and a light outlet can be provided on the electrode side. An example of the transparent material is an insulating film or a conductive film, each of which is SiO 2.
2, glass with boron / phosphorus addition, and Indium tin ox
ide (ITO), etc.

[0018]

【Example】

(Example 1) An example in which crystalline Si fine particles having a diameter of 20 Å were formed by the manufacturing method of the present invention and used as a channel to manufacture a single electron transistor will be described.

First, the structure of the produced transistor is shown in FIG.
It is shown in (c). A voltage is applied between the source terminal 9 and the drain terminal 10 to cause a source-drain current to flow through the crystalline Si microparticles 5, and the current is applied to the gate terminal 8 at O
N / OFF. When no voltage is applied to the gate terminal 8, a current does not flow (OFF state) due to the Coulomb blockade phenomenon that appears in the fine particles 5 due to the quantum size effect. If a voltage is applied to the gate terminal 8 and the tunnel resistance between the fine particles 5 is set to a quantum resistance (h / 4 (e * e), h; Planck's constant, e; elementary charge amount) or less, the Coulomb blockade is broken, A current flows (ON state).

The production of crystalline Si fine particles and a single-electron transistor using the same will be described below in order. Using a low resistance Si wafer 1 with a resistivity of 0.003 Ωcm, a thickness of 250 is formed on the surface other than the element formation area by the normal selective oxidation method.
A SiO 2 film 2 of 0 Å was formed as an element isolation region (see FIG. 2A). Next, this wafer is heat-treated in an oxygen atmosphere to form a 40 Å thick Si film on the surface of the element formation region.
An O 2 film 2 was formed (see FIG. 2B). On top of this,
A 1000 Å thick tungsten film 3 was deposited by the CVD method, and this was patterned by dry etching using a mask as shown in FIG. 2C. These are finally used as a source and a drain, respectively.

The sample was introduced into an ultra-high vacuum chamber and heated to 125 ° C., and while maintaining this temperature, an electron beam evaporation method was used to deposit Si atoms on the surface of the SiO 2 film 2 at a deposition rate of 0.1 Å / sec. Was supplied. This allows the diameter on the sample surface to
20 Å and 10 Å high hemispherical amorphous Si microparticles 4
They were formed at an interval of 0Å (see Fig. 3 (a)). This time,
The required deposition time was 20 seconds, and the substrate was rotated 10 times at a speed of 30 rpm. Then, the temperature was raised to 500 ° C. and heat treatment was performed for 1 hour to crystallize the amorphous Si fine particles 4.

Next, SiH4, O2, PH3, B2
Chemical vapor deposition using H5 as source gas (Chemical Vapor Deposition)
Boron / phosphorus added glass 6 is deposited by por deposition (CVD), the surface is flattened by reflow by heat treatment at 800 ° C., the thickness is 50 Å in the absence of crystallized Si fine particles 5, and the thickness is 40 in some places. Å (see Fig. 3 (b)).

The tungsten film 3 is deposited again by the CVD method, and the gate electrode 7 is formed by dry etching using a mask.
It was molded into the shape (see FIG. 3 (c)).

CVD of SiO 2 film 2 as an interlayer insulating film
Method (see FIG. 4 (a)) and wiring (FIG. 4 (b)) as is normally done in the integrated circuit manufacturing process.
And a passivation film were formed to form a gate terminal 8, a source terminal 9, a drain terminal 10, and a substrate potential terminal 11 (see FIG. 4C).

The substrate potential terminal 11 and the source terminal 9 are grounded, a negative voltage is applied to the gate terminal 8 and a positive voltage is applied to the drain terminal 10 to check the operation of this semiconductor device, and the gate voltage turns on the drain current as desired. I confirmed that it turned off.

(Example 2) By the manufacturing method of the present invention, crystalline Si fine particles having a diameter of 20 Å are formed, and the Si particles are used.
An example of manufacturing a light emitting element will be described.

First, the structure of the manufactured Si light emitting device is shown in FIG.
It is shown in (c). A voltage is applied between the upper electrode 13 and the lower electrode 14 to cause a tunnel current to flow, and carriers are injected into the crystalline Si microparticles 5 to obtain light emission.

Hereinafter, the manufacturing process will be described in order. Using a low resistance Si wafer 1 with a resistivity of 0.003 Ωcm,
An oxide film having a thickness of 2500 Å was formed on the surface other than the element formation region by a normal selective oxidation method to form an element isolation region (see FIG. 5A). Next, this wafer is heat-treated in an oxygen atmosphere, and the surface of the element formation region is covered with Si having a thickness of 30 Å.
An O 2 film 2 was formed (see FIG. 5B).

The sample was introduced into an ultra-high vacuum chamber, heated to 125 ° C., and while maintaining this temperature, Si atoms were deposited on the surface of the SiO 2 film 2 of the substrate at a deposition rate of 0.1 Å / sec. Was supplied. This allows the diameter on the sample surface to
20 Å, 10 Å high hemispherical amorphous Si microparticles 4
It was formed at intervals of Å (see Fig. 5 (c)). At this time, the deposition time is 20 seconds, and the substrate is rotated at a speed of 30 rpm.
It was rotated 0 times. Then, the temperature was raised to 500 ° C. and heat treatment was performed for 1 hour to crystallize the amorphous Si fine particles 4.

Next, SiH4, O2, PH3, B2
Chemical vapor deposition using H5 as source gas (Chemical Vapor Deposition)
Boron / phosphorus added glass 6 is deposited by por deposition (CVD) and the surface is flattened by reflowing by heat treatment at 800 ° C. The thickness is 40 Å where there are no crystalline Si fine particles 5, and the thickness is 30 Å where (Fig. 6
(See (a)).

On top of this, an Indium tin oxide (ITO) film 1 was formed by sputtering, as is commonly reported for optical elements.
2 was deposited. Then, this was formed into an upper electrode 13 having a desired shape by etching using a mask. Further, the boron / phosphorus-added glass 6 was etched by using the upper electrode 13 as a mask to remove the boron / phosphorus-added glass 6 and the crystalline Si fine particles 5 other than the electrode region (FIG. 6B).
reference). This is to prevent unnecessary current from flowing between the upper electrodes 13 along the crystalline Si fine particles 5.

After that, passivation and wiring were carried out by using a technique usually used in the manufacturing process of the integrated circuit, and the device fabrication was completed (see FIG. 6C).

When a voltage was applied to the upper electrode terminal 15 and the lower electrode terminal 16 of the thus-produced device and the device was observed, blue light emission was observed. That is, it was confirmed that the desired light emitting element could be manufactured by the present invention.

[0034]

According to the present invention, a highly reliable single electron element and a blue to green light emitting Si light emitting element can be manufactured.
Large amount of data transfer using SI and blue-green Si light emitting element
It becomes possible to realize an optical / electrical fusion system of processing.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of a manufacturing method of the present invention.

FIG. 2 is a diagram showing a first embodiment.

FIG. 3 is a diagram showing a first embodiment.

FIG. 4 is a diagram showing a first embodiment.

FIG. 5 is a diagram showing a structure of a semiconductor device of the present invention and a second embodiment.

FIG. 6 is a diagram showing a structure of a semiconductor device of the present invention and a second embodiment.

[Explanation of symbols]

1 ... Si wafer, 2 ... SiO 2 film, 3 ... Tungsten film, 4 ... Amorphous Si microparticles, 5 ... Crystalline Si microparticles, 6 ...
Boron / phosphorus-doped glass, 7 ... Gate electrode, 8 ... Gate terminal, 9 ... Source terminal, 10 ... Drain terminal, 11 ... Substrate potential terminal, 12 ... Indium tin oxide (ITO) film, 13
... upper electrode, 14 ... lower electrode, 15 ... upper electrode terminal, 1
6 ... Lower electrode terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Whalei 1-280, Higashikoigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (4)

[Claims] 1. A method of forming crystal grains on a different type of substrate, characterized in that the constituent elements of the crystal grains are once deposited as amorphous fine grains and are crystallized by heat treatment. Forming method. 2. The method for forming crystal grains according to claim 1, wherein the deposition of the constituent elements is performed by atomic / molecular beam transport in a vacuum. 3. The method for forming crystal grains according to claim 1, wherein the constituent element of the crystal grains is Si and the material of the substrate is SiO2. 4. The energy of the crystal grains is higher than that of the crystal grains.
A semiconductor device in which a material with a large gap is sandwiched, which is further sandwiched by electrodes, and electric charges are injected into crystal grains by applying a voltage between the electrodes to emit light.