JPS6133262B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which electrodes with good non-rectifying contact are provided.

Electrodes of semiconductor devices are formed on the surface of the substrate by forming the impurity density on the surface layer of the substrate higher than the impurity density inside the substrate in order to make good non-rectifying contact with the semiconductor substrate immediately below. ing.
For example, the NPN transistor shown in FIG ^.
Collector diffusion is performed on one side surface of the mold base 1, and N ⁺
After forming the type region 2 and the P type base region 3 by performing base diffusion on the other side surface, the N ⁺ type emitter region 4 and the P ⁺ type base region same type high impurity density region 5 for connection are simultaneously formed. Alternatively, it is formed by a diffusion process performed before and after. 6 is a selectively formed silicon oxide layer, 7 is a group impurity layer which may be boron or gallium, and this diffusion takes several tens of minutes to several hours at 1100 to 1200°C even when simultaneous diffusion is used. ing.

The present invention provides an improved method for manufacturing a semiconductor device that forms a region of the same type and high impurity density for connection at a low temperature for a short period of time when electrodes are installed. That is, when an electrode is installed on the surface of a region of one conductivity type on one surface side of a semiconductor substrate, the present invention deposits an impurity metal of the same conductivity type on at least the surface of this region, and then deposits an impurity metal of the same conductivity type on the surface of the region, and then deposits the impurity metal on the surface of the region on the other side. Primary heating is performed for a short period of time at a slightly low temperature to cause the metal that becomes the impurity of the same conductivity type to migrate thermophoretically, and then secondary heating is performed by reversing the heating conditions for both surfaces to return the free metal to the surface of the substrate. A method of manufacturing a semiconductor device is characterized in that a high impurity density region of the same conductivity type is formed in the process of metal movement by electrophoresis and reduction.

The primary heating in the method for manufacturing a semiconductor device of the present invention is performed by heating the evaporation side in a vacuum when the evaporation metal layer is, for example, aluminum and the layer thickness is several tens of microns, and the silicon substrate thickness is 0.5 mm, for example. the surface
At 690℃, the opposite surface is heated to 30℃ higher than the above vapor deposition side surface.
It is placed in a heating furnace set at a high temperature of ~50°C for several minutes.

Next, secondary heating is performed by inverting the substrate, thereby reversing the heating conditions for the primary heating and the substrate, and allowing several minutes to pass. Note that the surface temperature on the vapor deposition side in the above primary heating may be selected within a range up to 1300°C, and in this case also, the surface temperature on the opposite side is set to be 30 to 50°C higher than the above temperature. Further, when the vapor deposited metal is a gold-antimony alloy, it is preferable to set the surface temperature of the vapor deposition side to 1150°C and the opposite side surface temperature to 1200°C during primary heating.

As mentioned above, a metal layer to be an impurity is formed on one surface of the substrate by vapor deposition, and the vapor-deposited metal layer is heated for a short time at a lower temperature than the other surface by primary heating. is thermally migrated into the silicon crystal on the surface layer of the substrate and forms a high impurity density region of the same type as the one conductivity type region on one surface side of the substrate. The metal that exists free outside the crystal is returned to the vapor-deposited metal surface by secondary heating and does not contribute to the conductivity of the silicon substrate. However, since the speed of thermophoresis increases in crystal defect areas, the region to be migrated should be free from distortion.

Examples will be described below with reference to FIGS. 2 and 3.

Figure 2 shows a specific resistance of 5Ω-cm with a small amount of phosphorus added.
gallium is diffused on one surface of the N ^- type silicon substrate 1 to form a P type base region 3, and phosphorus is diffused on the other surface to form an N ⁺ type collector connection region 2;
Regarding the N ⁺ PN ^- N ⁺ transistor in which the emitter region 4 is formed by selectively diffusing phosphorus into a part of the P type base region, a part of the emitter region and a desired part of the base region are exposed and the remaining surface is exposed. Cover with a silicon oxide layer 6. Then, an aluminum vapor deposition layer 7 is formed. This silicon substrate 0 is placed in a furnace 8,
In a vacuum of 10 ^-4 to 10 ^-6 Torr, the furnace wall surface 81 facing the N ⁺ type collector connection region 2 is heated to 800° C. by heating this wall surface with a tungsten heater.
The furnace wall surface 82 facing the above is cooled with water, and this wall surface is heated to 750.degree. C., which is 50.degree. C. lower than the above-mentioned wall surface, and primary heating is performed for about 10 minutes.

Next, the heating conditions are reversed by turning the silicon substrate upside down, ie, the deposition surface is placed on the high temperature side of the furnace, and secondary heating is performed for 10 minutes.

The aluminum vapor deposited layer 7 can be selectively etched and left as an emitter electrode 9 on the surface of the emitter region 4, as shown in FIG. At the same time, a P ⁺ type high impurity density region 10 is formed on the surface of the P type base region by thermophoresis so as to improve non-rectifying contact. Note that in this example, the N ⁺ emitter area is 1
Since the concentration is about two orders of magnitude higher, the conductivity type is not affected by aluminum thermophoresis.

Next, when the surface of the planned region is N-type, if a gold-antimony alloy is deposited instead of aluminum and the manufacturing method of the present invention is carried out, the high impurity density region
An N ⁺ type region is formed.

As mentioned above, according to the present invention, the temperature is lowered by 200 to 300°C than when the conventional high impurity density region is formed by diffusion.
What used to require several hours at low temperatures has now been reduced to just a few minutes. Moreover, it has the remarkable advantage of being able to form a desired area with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an N ⁺ PN ^- N ⁺ transistor in which a high impurity density region of the same type as the P ⁺ type base region is formed by a conventional method, and FIG. 2 shows a primary heating step in an embodiment of the manufacturing method of the present invention. N ⁺ PN ^- N ⁺
FIG. 3 is a cross-sectional view of an N ⁺ PN ^- N ⁺ transistor formed according to an embodiment of the present invention. 0 ... Semiconductor substrate (silicon substrate), 7... (Metal) vapor deposition layer, 10... High impurity density region, 81...
...High temperature furnace wall surface, 82...Low temperature furnace wall surface.

Claims (1)

[Claims] 1. When installing an electrode on the surface of a region of one conductivity type on one surface side of a semiconductor substrate, after vapor-depositing a metal serving as an impurity of the same conductivity type at least on the surface of this region, The metal constituting the impurity of the same conductivity type is thermally migrated by primary heating at a low temperature for a short period of time, and then the above-mentioned heating conditions for both surfaces are reversed and secondary heating is performed to reduce the free metal, thereby forming a high impurity density region of the same conductivity type. 1. A method of manufacturing a semiconductor device, characterized by forming a semiconductor device.