JP2703334B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a technique for forming a single crystal layer on a dielectric film by liquid crystal growth, and particularly to a technique for preventing a substrate from being deformed by heat. The present invention relates to a method for manufacturing a semiconductor device in which such a single crystal layer is obtained.

(Prior Art) As a method of obtaining a semiconductor single crystal film of silicon or the like on a substrate, there is known a method of melting a polycrystalline silicon film deposited on an oxide insulating film by an energy beam to form a single crystal. Was.

In the above method, it is effective to melt and recrystallize a large area at a time in order to ensure the uniformity of the silicon recrystallized layer. However, when a large area is melted at a time, the thermal strain increases, and the substrate is deformed after the semiconductor single crystal layer is formed.

Next, the conventional liquid phase growth method and its problems will be described with reference to FIG.

FIG. 4 (a) is an explanatory view showing the above-mentioned conventional liquid phase growth method. In the figure, reference numeral 20 denotes a thin silicon dioxide (Si
O ₂ ) A silicon semiconductor substrate on which a film 21 is formed, and 22 is an SiO ₂ film 21
It is an amorphous silicon film deposited thereon. This board 20
The semiconductor single crystal film is obtained by scanning and irradiating an energy beam 23 such as an electron beam, an ion beam, or a laser beam to melt the amorphous silicon film 22 and recrystallize the substrate using the substrate as a seed. .

(Problems to be Solved by the Invention) However, in manufacturing the single crystal film shown in FIG. 4 (a), in order to melt a large area at a time, a strong energy beam 23 is applied to a fine region. The substrate 20 including the crystalline film 21 is locally and strongly heated, causing an extreme temperature gradient in the substrate. As a result, the substrate after manufacturing is deformed by thermal strain, which is a serious problem in commercialization. Note that reference numeral 24 conceptually shows contour lines of thermal strain.

In order to prevent such deformation due to thermal distortion, the fourth
As shown in (b), a method has been considered in which the substrate 20 is heated from the back side by the heater 25 to raise the temperature of the entire substrate 20 to reduce the local concentration of heat by the beam 23. However, in this method, although the thermal strain 24 has a relatively gentle gradient as shown in the figure, it is still not enough to reduce the thermal deformation of the substrate to a practically acceptable level.

The present invention has been made in view of the above points,
The purpose of the semiconductor device is to reduce the deformation of the substrate after the production to such a degree that practically no problem is caused by causing almost no thermal strain on the substrate in the process of forming the single crystal film by liquid crystal growth. It is to provide a manufacturing method.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention includes a step of forming an insulating film and an amorphous silicon film in a layer on a silicon substrate. And bonding a metal plate to the back surface of the silicon substrate with an adhesive layer having excellent thermal conductivity made of one of an indium-Pt alloy and an indium-Pd alloy each having a predetermined melting point interposed therebetween, A step of pre-heating the adhesive layer at a temperature equal to or higher than a predetermined melting point to dissolve the adhesive layer; and a step of heating the amorphous silicon film on the silicon substrate so that the temperature of the adhesive layer is equal to or lower than the melting point. Irradiating an energy beam to crystallize the amorphous silicon film by liquid phase growth to obtain a silicon single crystal film.

(Function) In performing the above-mentioned liquid phase growth, the back surface of the substrate and the metal plate are bonded to each other via an adhesive layer having good thermal conductivity in a dissolved state, and when the adhesive layer is in a solid state, an energy beam is applied onto the silicon substrate. Irradiation is performed. Therefore, the heat generated locally on the substrate is quickly diffused to the surroundings through the metal plate bonded via the adhesive layer. For this reason, heat is prevented from being concentrated on one point of the substrate, and heat is radiated quickly as a whole, so that a rise in the temperature of the substrate is suppressed. As a result, the occurrence of thermal distortion of the substrate due to the irradiation of the energy beam is effectively reduced to a level that does not pose a problem in practical use, so that substrate deformation is suppressed.

Further, at the time of irradiation with the energy beam, since the adhesive layer is in a solid state, the silicon substrate is held in a fixed shape by the adhesive layer.
Therefore, the deformation of the silicon substrate is further suppressed.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a view for explaining one embodiment of the present invention, and shows a state in which liquid phase growth is performed while irradiating a silicon substrate with an energy beam. As shown in this figure, in this method, first, for example, a 2.0 μm thick silicon dioxide film 11 is formed on a (100) oriented single crystal silicon substrate 10 by a CVD method, and a portion serving as a nucleus during recrystallization of polycrystalline silicon is formed. The opening 12 is formed by selectively etching a part of the silicon dioxide film 11. Note that an aqueous solution of ammonium fluoride was used for this etching. Next, silane (Si) is applied to the entire upper surface of the silicon dioxide film 11 including the opening 12.
After a polycrystalline silicon film 13 having a thickness of 0.8 μm is deposited by a CVD method utilizing thermal decomposition of H ₄ ), a silicon dioxide (SiO ₂ ) film 18 having a thickness of 0.5 mm is further deposited by a CVD method.

After the oxide films 11, 18 and the silicon film 13 are formed in a layered structure on the substrate 10 as described above, the tungsten metal plate 14 is formed on the back surface of the silicon substrate 10 from an indium-Pt alloy or an indium-Pd alloy. It is pasted with the adhesive layer 15 formed therebetween. The indium-Pt alloy has an indium ratio of 65 to 75% and a melting point of 894 ° C. The indium-Pd alloy has an indium ratio of 68.
The melting point is 800 ° C.

Next, the adhesive layer 15 is heated to 800 ° C. to 1000 ° C. together with the substrate 10 to dissolve the adhesive layer 15.

Thereafter, the adhesive layer 15 and the substrate 10 are brought to a solid state at a temperature of 750 ° C. north. Therefore, the substrate 10, the adhesive layer 15, and the tungsten plate 14 adhere very well, and the thermal conductivity is further improved.

When the silicon substrate is prepared as described above, the first
As shown in the figure, when the electron beam 16 is scanned and irradiated in the direction of the arrow, the polycrystalline silicon film 13 is melted from the heated portion and recrystallized to obtain a single crystal silicon film. Here, the irradiation of the electron beam is performed so that the adhesive layer 15 becomes a solid state at 750 ° C. or lower. At this time, considerable heat is generated in the irradiated portion of the electron beam 16 and thermal strain 17 is generated. However, according to the method of this embodiment, the tungsten plate 14 adheres to the back surface of the substrate 10 via the adhesive layer 15. The heat is quickly transferred to the surroundings through these two layers because it is adhered well, preventing heat from concentrating at one point and radiating heat to the outside to suppress a rise in the temperature of the substrate. Then, the substrate 10
Is held in a fixed shape by the solid-state adhesive layer 15. Therefore, the thermal strain applied to the substrate 10 is reduced to a level that does not cause a problem in practical use, and a semiconductor layer with almost no deformation of the silicon substrate can be obtained. Further, in the experiments by the inventors, it was possible to continue the lateral epitaxial growth from the opening.

In the experiment of the inventor, the scanning of the electron beam 16 was performed by the method of Shanar of Applied Physics (J. Apll.
s.) 59 (1986) p. 2971 (T. Hamasak
The method shown in the article by i) et al. was used. That is, 50Mhz
The spot beam having a half width of about 150 μm was rapidly deflected in one direction by an amplitude-modulated sine wave to obtain a pseudo linear electron beam having a length of about 10 mm. For the amplitude modulation of this beam, a modulated wave having a waveform controlled by a computer was used in order to equalize the intensity distribution in the length direction of the linearized beam at a frequency of 100 KHz. The beam linearized in this manner is subjected to a beam acceleration voltage of 10 KV, a beam current of 12 mA, and a scanning speed of 100 m.
At m / s, scanning was performed in a direction perpendicular to the linearized beam.

FIG. 2 shows another embodiment of the present invention. In this embodiment, the oxide insulating films 11 and 18 and the amorphous silicon film 13 are formed on the silicon substrate 10, and the tungsten plate 14 is attached to the back surface of the substrate 10 with the adhesive layer 15 interposed therebetween. Although the method is exactly the same as the method shown in FIG. 1, this method further scans the sample surface with an electron beam while heating the entire substrate 10 from below the rear surface of the substrate 10 with a heater 17 to perform liquid phase growth. It is characterized in that a short crystal film is formed. According to this method, the substrate 10 is entirely heated through the tungsten plate 14, and therefore, the temperature gradient of the substrate due to the irradiation of the electron beam becomes gentler,
The occurrence of thermal distortion is further reduced. Therefore, a single crystal film of a semiconductor device in which the silicon substrate is hardly deformed by heat can be obtained. The electron beam irradiation method can be the same as the method shown in FIG. 1 described above.

FIG. 3 is a graph showing the relationship between the size of the heating area and the warpage of the silicon wafer at that time. In other words, in this graph, the horizontal axis indicates the linearization length of the electron beam as the size of the heating region, and the vertical axis indicates the degree of the warpage of the wafer as the degree of deformation of the silicon substrate. I have. In the graph, curve A indicates the degree of deformation of the conventional wafer, and curve B indicates the degree of deformation of the silicon wafer by the method of the present invention. As is clear from this graph, in the silicon wafer according to the method of the present invention, the degree of deformation for the same heating area is significantly improved as compared with the conventional method, particularly when the linearization length is 5 mm or more. It has become possible to perform single crystallization while suppressing deformation of the silicon substrate to a practically acceptable range.

It should be noted that the same effect as in the above-described embodiment could be obtained by using molybdenum, tantalum or rhenium instead of tungsten. Further, in the above two embodiments, the polycrystalline silicon film is formed on the oxide insulating film and made amorphous, but amorphous silicon may be directly deposited on the oxide insulating film. Of course. In addition, the method of the present invention can be applied to all cases where an electron beam, an ion beam, a laser beam, or the like is used as an energy beam. . This is because the vapor pressure of the indium alloy in a vacuum is low, so that the degree of vacuum is not impaired even by electron beam irradiation requiring a high vacuum.

[Effects of the Invention] As described above in detail with reference to the embodiments, according to the method according to the present invention, the heat generated by concentrating at one point on the substrate is quickly released to the surroundings, and the liquid phase is formed by using the energy beam. Since the single crystal film can be obtained by growing, the substrate after the production hardly undergoes deformation due to thermal strain. Therefore, an excellent semiconductor device having a substrate with almost no deformation can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a method of one embodiment of the present invention, FIG. 2 is a schematic diagram for explaining a method of another embodiment of the present invention, and FIG. 3 is a heating region by an energy beam. FIG. 4 is a graph showing the size of the substrate and the degree of deformation of the substrate (wafer). FIG. 4 is a schematic diagram showing a conventional manufacturing method. 10 Semiconductor substrate 11, 18 Oxide insulating film 13 Amorphous silicon film 14 Tungsten plate 15 Indium alloy layer (adhesive layer) 16 Electron beam

Claims (2)

(57) [Claims] A step of forming an amorphous silicon film on a surface of a silicon substrate via an insulating film; and a step of bonding an indium-Pt alloy or an indium-Pd alloy having a predetermined melting point on a back surface of the silicon substrate. Bonding the metal plate, and preheating the adhesive layer at a temperature equal to or higher than the predetermined melting point to dissolve the adhesive layer. The silicon substrate so that the adhesive layer has a temperature equal to or lower than the melting point. Irradiating the upper amorphous silicon film with an energy beam and crystallizing the amorphous silicon film by liquid phase growth to obtain a single crystal silicon film. . 2. The indium-Pt alloy according to claim 1, wherein the proportion of indium is 65-75%, and the indium-Pd alloy has a proportion of indium of 68-78%. Of manufacturing a semiconductor device.