JP2002353526A - ELECTRODE-FORMING METHOD FOR beta-FeSi2 ELEMENT - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode forming method for a '-FeSi2 element, for which the manufacturing method is significantly simplified, enabling lower manufacturing cost. SOLUTION: A method for forming an electrode is provided for constituting an element on a β-FeSi2 thin film of a semiconductor or on a flat plate. Either in the atmosphere or in an inert gas atmosphere, the surface part of the β-FeSi2 material is heated to 982 deg.C or higher, so that the entire or part of it is phase- converted into a α-FeSi5 phase. A part, in which a phase has converted, is used as an electrode 2 of proper conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device in the field of electronics, which comprises depositing a metal material from outside and applying and bonding an electrode for conducting a current to an element material plate or a thin film substrate. relates to the electrode forming method for forming without, in particular beta-FeSi ₂
And a method of heating a part of the electrode to convert it to a metal phase to form an electrode.

[0002]

2. Description of the Related Art A conventional semiconductor device is silicon (S).
i) A functional material thin film is formed on a substrate or a flat substrate material, and electrodes for inputting / outputting signals are provided thereon. In the case of an electrode of a relatively large sample piece of ceramic or a functional material, an electrode wire is wound around the sample end, or the electrode wire is fixed to a part of the surface using a metal paste or various solders.

On the other hand, in order to perform fine wiring such as light emission, light reception, memory and IC circuit devices using Si or III-V group compound semiconductor materials, various electrode forming methods have been conventionally developed.

[0004] In general, a device has been formed by depositing a vapor deposition film, a sputter film, and an ion plating film of a metal conductor on the surface of the device and processing it into a fine pattern using photolithography technology.

[0005]

A semiconductor device requires a semiconductor material and an electrode material. Since the function of the electrode is to introduce or extract a current to or from the functional semiconductor material, a so-called ohmic contact must be made at the interface between the two, which mechanically adheres to each other and shows normal electrical conduction.

For this purpose, a metal that is a good conductor is selected as an electrode material. Generally, aluminum (Al), copper (Cu), silver (Ag), gold (Au), or the like is used.
Although a material having high conductivity is desirable, problems such as corrosion after long-term use may occur depending on the potential difference depending on the atmosphere or temperature used and the combination with a semiconductor material. Since changes due to these phenomena must be avoided, it is important to select an electrode material.

Further, in order to maintain a good bonding state between the semiconductor material and the electrode material, at least a foreign substance that hinders mechanical contact must be removed. For example, both surfaces are cleaned well to remove organic impurities, or oxides and dust are removed to increase the degree of mechanical adhesion. As a method of bringing the electrode material into contact with the cleaned surface, a metal film is deposited in a vacuum or a film is formed by a sputtering method.

However, the operation of keeping the surface clean is a factor of increasing the number of steps and increasing the price.

Furthermore, in order to process the laminated conductive film into an arbitrary electrode pattern shape, an expensive photolithographic apparatus is used, a pattern original mask is prepared, a resist is applied to the semiconductor film surface, exposure is performed, and the resist film is removed by etching. Or the etching of the metal film with an alkaline solution → the completion of the electrode pattern.

However, after a fine metal pattern is formed by the photolithography method, when forming another metal film electrode thereon, a laminated metal thin film is formed over the etching step formed in the pretreatment. Is formed. At this time, the phenomenon that the film connecting the lower surface and the upper surface of the step is not sufficiently connected, that is, the so-called step coverage is poor occurs, which causes the electrode film to be peeled or the disconnection to occur.

As described above, in these conventional forming methods, in order to increase the production yield and achieve the high quality and low cost targets of the product, expensive equipment is used, and the process inspection is performed many times. However, there was a problem that much time and effort had to be taken.

An object of the present invention is to provide a method for forming an electrode of a β-FeSi ₂ element, which can eliminate the above-mentioned problems, remarkably simplify the manufacturing process, and reduce the manufacturing cost.

[0013]

According to the present invention, there is provided a method for forming an electrode for forming an element on a semiconductor β-FeSi ₂ thin film or a flat plate. The β-FeSi _{2 in the} atmosphere or in an inert gas atmosphere.
By heating the surface portion of the material to at least 982 ° C. or more, part or all of the material is phase-converted to the α-Fe ₂ Si ₅ phase, and the phase-converted portion is used as an electrode having good conductivity. I do.

[2] In the method for forming an electrode of a β-FeSi ₂ element according to the above [1], a heat source for heating a part of the material surface is a laser beam, and the material surface is formed near a focal point where the laser beam is focused. Irradiation heats and raises the temperature, causing conversion to a conductive metal crystal phase, and then shutting off the laser beam and rapidly cooling the material to around room temperature to reduce that portion of the metal crystal phase. The present invention is characterized in that a conductive portion is used as it is, and an electrode having the conductive portion in a predetermined shape is formed.

[3] The method for forming an electrode of a β-FeSi ₂ element according to the above [2], wherein the heating temperature of the material surface by the laser beam is between 982 ° C. and 1212 ° C., and α-Fe ₂ Si ₅ After heating the irradiated portion of the laser beam in the phase, the laser beam is cut off and rapidly cooled to around room temperature to leave the α-phase, and an electrode pattern is formed by repeating this process.

[4] The method for forming an electrode of a β-FeSi ₂ element according to the above [2], wherein Nd is used as the laser light source.
It is characterized by using an additive YAG laser.

[5] The method for forming an electrode of a β-FeSi ₂ element according to the above [2], wherein the β-FeSi 2
₍₂₎ A method of forming an electrode by irradiating the laser light to form an element on a thin film or a flat plate, wherein the material surface is heated in advance to around 600 ° C. And heating the material surface by irradiating the surface of the material, thereby forming an electrode by causing conversion to a conductive crystalline phase.

In the present invention, when an electrode is formed on the surface of a semiconductor material to form an element, a special cleaning for obtaining an ohmic contact and a baking heating after contact, without selecting a special electrode material and using it, Also, it eliminates the steps of vapor deposition and sputtering film formation, avoids the step coverage problem even when film formation other than electrodes is required, eliminates steps such as masks and light exposure, and provides good quality in air or an inert gas atmosphere. This provides means for forming an electrode of the β-FeSi ₂ element.

That is, a part of the sample material is heated to a temperature higher than the transformation temperature of the semiconductor crystal phase by laser irradiation,
The part is converted into a metal crystal phase to form a conductor, which is used as an electrode.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic view of an apparatus for converting a part of the β-FeSi ₂ phase into an α-Fe ₂ Si ₅ phase by laser heating according to an embodiment of the present invention, and FIG. FIG. 6 is a sectional view of an electrode forming step of a FeSi ₂ element.

As shown in FIG. 1, a sample plate (silicon substrate) 1 on which a β-FeSi ₂ film has been grown on a Si crystal substrate in advance is moved by a computer 9 to draw an electrode pattern. It is placed on the stage 10.

A laser beam 6 emitted from an Nd: YAG laser 8 similarly controlled by a computer 9
Passes through a mirror 5 that optimally constructs the optical path of the apparatus and a beam switch 7 also controlled by a computer, and is further contracted by a condenser lens 4 to focus on a heating point 3 on the sample surface. The electrode 2 can be formed by patterning a portion formed into a metal film by this heating. The scattered light reflected from the sample surface is absorbed by the absorber 11.

The feature of the present invention is that the device material β-Fe
It is based on the fact that the Si ₂ thin film utilizes the transformation of a metal body into α-Fe ₂ Si ₅ by causing a crystal transformation by a heating operation.

Hereinafter, a method for forming an electrode of a β-FeSi ₂ element of the present invention will be described in detail with reference to FIG.

(1) First, a semiconductor β-FeSi ₂ thin film 22 is formed on a silicon substrate 21 as shown in FIG.

(2) Next, as shown in FIG.
The laser beam 23 to a predetermined location of the beta-FeSi ₂ thin film 22 by irradiating, by heating to above 982 ° C., is converted to α-Fe ₂ Si ₅ 24 of the metal body.

(3) Next, as shown in FIG. 2C, the metal α-Fe ₂ Si ₅ 24 is rapidly cooled to near room temperature to form a permanent electrode 25.

FIG. 3 is a diagram showing a binary phase diagram of iron and silicon and a principle diagram for explaining a phenomenon at the time of metallization by heating.

The β-FeSi ₂ phase of the intermetallic compound made of a composition ratio of Fe and Si of 1: 2 is a semiconductor, and its composition exists at a point A on the _binary phase diagram. When this material is heated by laser annealing or the like, β phase decomposition temperature (982 ° C) B
At which point the β-FeSi ₂ phase structure is maintained up to this temperature. When the temperature further rises and exceeds point B to point C,
The β-FeSi ₂ phase structure of the heated part is decomposed, and a small amount of the ε-FeSi phase D point material and a large part of α-Fe ₂ S
i ₅ phase E point substance becomes separated mixed crystal phase. The α-Fe ₂ Si ₅ phase formed here is a metal phase, which is used as an electrode material.

The position in the phase diagram of the material in which most of the heating points have been converted to the α-Fe ₂ Si ₅ phase is point E. Then
When the material that has been converted to the α phase at the E point is rapidly cooled and lowered to a point F near room temperature, the stable thermal equilibrium phase β
Α-F without separating into a mixed crystal phase of FeSi ₂ and Si
It remains as e ₂ Si ₅ . Since this crystal phase is a metal, it becomes a good conductor of electricity and functions as an electrode material.

If the material at the point E is allowed to stand at around 900 ° C. to 650 ° C. for a good time without being rapidly cooled to around room temperature, α-F
Since the e ₂ Si ₅ phase is separated and precipitated again into the β-FeSi ₂ semiconductor phase and Si, the e ₂ Si ₅ phase does not have metal properties as an electrode. In order to use the part converted from the β-FeSi ₂ phase by heating to the α-Fe ₂ Si ₅ phase as an electrode, it is important to rapidly cool to a point F near room temperature.

A feature of the present invention is that a portion of a sample film is converted into a metal by causing a crystal transformation by a heating operation. Therefore, when manufacturing a device for forming an electrode on a semiconductor element, a metal for an electrode is externally formed. It is not necessary to adhere and deposit. Since a part of the sample material becomes an electrode with no flat surface on the sample material surface, the contamination between the material and the electrode, which has occurred during the conventional electrode formation, is basically eliminated, and the material Excessive cleaning of the surface is unnecessary. In addition, since the contact surface of the material is a flat continuous surface, an electrode in which ohmic contact is completely obtained is formed.

The method for forming an electrode of a β-FeSi ₂ element of the present invention is characterized in that a necessary portion is heated and converted into a metal phase, so that the heating method is not limited to the laser annealing method, but may include a high heat flame or a high heat metal. It is also possible by a method such as crimping one end.

Generally, an electrode of a semiconductor device has a width of 1 mm or less and is composed of a fine pattern of several hundred μm to several tens μm. It is desirable to use a laser beam capable of miniaturizing a heat source. When the laser beam is narrowed down using a lens, the beam diameter applied to the focal point becomes several μm to several tens μm. Since this part is metallized, it can be freely moved by moving the light beam and the sample position and continuously connecting the heating points. An electrode pattern is formed.

The laser beam used for heating has various wavelengths. For example, an excimer laser having a strong output in an ultraviolet wavelength region, a semiconductor easily obtained in a green or red visible light region, a He or Ne gas laser, a C
d and Ne: YAG solid-state lasers; and CO ₂ gas lasers having a long wavelength of 10 μm. Each has its own characteristics and can be heated, but in order to efficiently absorb light and speed up heating, the light absorption coefficient and reflection coefficient of the material must be selected. That is, light having a wavelength of 0.9 μm to 2 μm has a high absorption coefficient for the β-FeSi ₂ film. In this regard, the Nd: YAG laser is most suitable as the light source for the present invention. Although an ultraviolet laser can provide a large energy power, it is not suitable as a heating light source because the high energy causes collisions and scattering of material atoms and molecules.

Further, visible light reflects a lot and is not efficient as a heat source. Long-wavelength lasers have a large focal area, are not suitable for fine electrode patterns, and have low light absorption.

The energy required for heating depends on the light absorptance, thermal conductivity, melting point, specific heat, etc. of the material to be irradiated. However, in order to heat a region having a radius of several tens of μm to around 1000 ° C., 10 ⁺⁶ W / requires an energy density of cm ² ,
A short time in seconds is sufficient. If an ordinary laser having a beam diameter of 1 to 2 mm has an output of several W, a sufficient energy density can be obtained when focusing is performed.

For β-FeSi ₂ , the wavelength is 1.06 μm.
When a Nd: YAG laser of m is used, its light absorption is as good as 10 ⁵ and its thermal conductivity is very low as used in thermoelectric power generation materials. Can be heated to around 1000 ° C. by squeezing 10 W output light and irradiating for several seconds.

FIG. 4 is an enlarged cross-sectional view of a portion for irradiating the sample surface by focusing the laser beam.

As shown in this figure, when a laser beam 33 is focused and irradiated on a portion (heating point) 34 on the surface of a β-FeSi ₂ phase 32 grown on a sample plate (silicon substrate) 31. Heated by the light absorption of the material. The temperature of the heating point 34 is high at the center and the heated portion spreads due to heat conduction, but the temperature decreases as the distance from the center increases. The line 35 is an isotherm along the heat diffusion direction at this time. Reference numeral 36 denotes an electrode, 37 denotes a scanning direction of the laser beam 33, and 38 denotes a trajectory of the scanning of the laser beam 33.

Here, β-FeSi_Two→ α-Fe_TwoSi
_FiveThe part heated sufficiently to cause phase transformation is metal
Convert to phase. In order to use this converted part as an electrode wire,
When the position where the beam hits is moved in a straight line or curve,
Α-Fe converted to trace 38 _TwoSi_FiveThe phase remains. Once
If the sweep does not have enough width for the electrode,
Trajectory 3 before the beam hitting position is converted to α phase
If you sweep from side 8 in the direction 37
An electrode pattern having a large width can be obtained.

By repeating this operation to form a desired shape pattern, a device electrode can be obtained.

Since the energy density of the laser beam can be increased by narrowing it down, it is a method suitable for heating a small area. However, when the energy density cannot be increased, for example, in the case of heating the image irradiation of an incandescent lamp, the laser beam is irradiated. It is effective to apply a heating bias to the irradiation sample in advance. That is, a heater is placed between the sample plate (silicon substrate) and the movable stage, or the entire surface of the sample is irradiated with lamp heater light to raise the temperature of the sample so as not to exceed 500 ° C.

In this temperature range, the β-FeSi ₂ phase of the sample does not change, and the α-Fe ₂ Si ₅
There is no conversion to the Si phase. By irradiating the sample surface in this state with a light source, even a light source having a low power can sufficiently reach a temperature of 982 ° C. or more in a short time and can be converted into an α-Fe ₂ Si ₅ phase. If the light source is quickly turned off after the conversion to the metal phase, and if the light source is rapidly cooled, the temperature will be around 500 ° C., so that a patterned electrode is formed while the α-phase metal remains.

The method of obtaining the desired electrode pattern by continuous repetitive sweeping by converting the focal position of the laser beam into a metal phase has been described above. However, the entire surface of the material is irradiated with the projected image of the electrode pattern, and the entire surface is exposed at once. A method of obtaining the electrode pattern of (1) is also considered. However, a laser light source for heating a large area of the entire electrode portion requires a very large power, and a large amount of heat is applied to the original pattern, which may burn the pattern. The above-described preheating method produces an effect of suppressing the power of the original laser, and is therefore an effective method for obtaining a portion of the electrode pattern by heating and irradiating it in a single irradiation.

It should be noted that the present invention is not limited to the above-described embodiment, but various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0048]

As described in detail above, according to the present invention, by heating a part of the β-FeSi ₂ thin film to 982 ° C. or more, the part is converted into the α-Fe ₂ Si ₅ phase. And that part was made to be a conductive electrode,
Conventionally, a metal film is deposited and photolithography is not used to form a device electrode.Without forming a flat surface, the manufacturing process can be remarkably omitted, and a low-cost device can be constructed. became.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for implementing a method for forming an electrode of a β-FeSi ₂ element according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an electrode forming step of a β-FeSi ₂ element according to an embodiment of the present invention.

FIG. 3 is a principle diagram illustrating a binary phase diagram of iron and silicon and a phenomenon at the time of metallization by heating.

FIG. 4 is an enlarged view of the vicinity of an electrode formed for irradiation with a laser focus.

[Explanation of symbols]

Reference Signs List 1,31 Sample plate (silicon substrate) 2,36 Electrode 3 Heating point 4 Condensing lens 5 Mirror 6,23,33 Laser beam 7 Beam switch 8 Nd: YAG laser 9 Computer 10 Stage 11 Absorber 21 Silicon substrate 22 Semiconductor β -FeSi ₂ thin film 24 Metallic α-Fe ₂ Si ₅ 25 Permanent electrode 32 β-FeSi ₂ phase 34 Site (heating point) 35 Isotherm 37 Laser beam scanning direction 38 Trajectory of laser beam scanning

Continuation of the front page (71) Applicant 501208671 Poet King Wang 4-8-3-4-404 Ninomiya, Tsukuba City, Ibaraki Prefecture (71) Applicant 501208682 Yasuhiro Fukuzawa 36-13 Higashiarai, Tsukuba City, Ibaraki Prefecture Room 303, Tokuhara Mansion 303 71) Applicant 501208992 Yasuhiko Nakayama 1-41-1103 Keyakidaira, Miyamae-ku, Kawasaki-shi, Kanagawa (72) Inventor Yunosuke Makita 2-8-10, Hakusan, Toride-shi, Ibaraki-pref. -211-1 510, Building 410 (72) Inventor: Shio Wang 4-8-3-4-404, Ninomiya, Tsukuba City, Ibaraki Prefecture (72) Inventor: Yasuhiro Fukuzawa 36-13 Higashiarai, Tsukuba City, Ibaraki Prefecture Tokuhara Mansion 303 Room No.72 (72) Inventor Yasuhiko Nakayama 1-41-103 Keyakidaira, Miyamae-ku, Kawasaki-shi, Kanagawa F term (reference) 4M104 AA10 BB19 CC01 DD31 HH20

Claims (5)

[Claims] 1. A method for forming an electrode for forming an element on a semiconductor β-FeSi ₂ thin film or a flat plate, comprising: forming the β-FeS 2 in air or an inert gas atmosphere.
i ₂ material in whole or in part by heating the surface portion to at least 982 ° C. or higher is phase converted to α-Fe ₂ Si ₅ phase, the use of a portion obtained by said phase transformation as a good electrode conductivity A method for forming an electrode of a β-FeSi ₂ element. 2. The method for forming an electrode of a β-FeSi ₂ element according to claim 1, wherein a heat source for heating a part of the material surface is a laser beam, and the laser beam is irradiated on the material surface near a focused focus. The temperature is increased by heating to cause conversion to a conductive metal crystal phase, and thereafter, the laser beam is shut off and the material is rapidly cooled to around room temperature to leave that portion in the metal crystal phase. A method for forming an electrode of a β-FeSi ₂ element, comprising forming an electrode having a predetermined shape as a conductive portion. 3. The method for forming an electrode of a β-FeSi ₂ element according to claim 2, wherein the heating temperature of the material surface by the laser beam is between 982 ° C. and 1212 ° C., and the α-Fe ₂ Si ₅ phase is heated. After heating the irradiated portion of the laser light, the laser light is cut off and rapidly cooled to around room temperature to leave the α-phase, and an electrode pattern is formed by repeating this process.
A method for forming an electrode of a FeSi ₂ element. 4. The method for forming an electrode of a β-FeSi ₂ element according to claim 2, wherein the laser light source is Nd-doped Y.
A method for forming an electrode of a β-FeSi ₂ element, comprising using an AG laser. 5. The method for forming an electrode of a β-FeSi ₂ element according to claim 2, wherein the electrode is formed by irradiating the laser beam to form the element on a β-FeSi ₂ thin film or a flat plate of the semiconductor. A method of forming a conductive crystal phase by heating the material surface to near 600 ° C. in advance and further irradiating the material surface near the focal point of the laser beam. The method for forming an electrode of a β-FeSi ₂ element, wherein the electrode is formed by causing