JPS6137773B2 - - 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 a means for forming an epitaxial substrate whose elements are separated in an isolation region is improved.

Conventionally, epitaxial substrates used as substrates for bipolar devices are fabricated by vapor phase growth of a desired epitaxial layer on a semiconductor substrate. To form elements such as transistors on the epitaxial layer ^of the epitaxial substrate thus obtained, for example, ^as shown in FIG. P such as boron is applied to the layer 3 through the diffusion mask 4.
It is necessary to provide in advance a p ⁺ -type isolation region 5 for element isolation by diffusing type impurities. However, in such conventional methods, it is necessary to use an expensive vapor phase growth apparatus when growing the epitaxial layer, and the growth temperature etc. must be strictly controlled in order to obtain the desired epitaxial layer. There are drawbacks that inevitably lead to a decrease in productivity. Furthermore, in forming the p ⁺ -type isolation region, diffusion in the horizontal direction is involved, as shown in FIG. 1, which has the disadvantage of impairing high integration of devices.

On the other hand, as a result of various studies to overcome the above drawbacks, the present invention has been developed by coating a single-crystal semiconductor substrate with an amorphous semiconductor layer containing impurities of the first conductivity type, and further covering desired portions of the semiconductor layer. When a semiconductor layer is covered with a high melting point metal film and used as a mask to selectively ion-implant impurities of the second conductivity type into the semiconductor layer and then irradiated with laser light, the amorphous semiconductor layer is much more sensitive to the laser than the single crystal semiconductor substrate. The non-crystalline semiconductor layer, which easily absorbs light energy and is reflective of the high-melting point metal film, forms a single crystal from the portion in contact with the single-crystal semiconductor substrate, using the single-crystal semiconductor substrate as a crystal nucleus due to the reflective property of the high-melting-point metal film. In addition, it has been found that the second conductivity type ion implantation portion can be diffused to selectively form a second conductivity type single crystal semiconductor layer. Moreover, when the laser beam is irradiated again after the high melting point metal film is removed, the energy absorption of the laser beam is greater in the amorphous semiconductor layer than in the single crystal semiconductor, as described above. The portion of the amorphous semiconductor layer from which the film has been removed is selectively melted and similarly becomes single crystallized, while the already formed single crystal semiconductor layer of the second conductivity type absorbs almost no energy from the laser beam and is heated. It has been found that the second conductivity type impurity in the single crystal semiconductor layer does not re-diffuse in the lateral direction because it is not affected by this effect.

As a result of further intensive research based on the above findings, the inventors of the present invention coated a semiconductor substrate with an amorphous semiconductor layer containing impurities of the first conductivity type, and covered desired portions of this semiconductor layer with a refractory metal film. After ion-implanting impurities of the second conductivity type into the semiconductor layer portion using this as a mask, the exposed semiconductor layer portion other than the high melting point metal film is converted to the second conductivity type by irradiating with laser light. can be converted into a single crystal semiconductor layer. However, by irradiating the high melting point metal film again with laser light, the high melting point metal film can be removed without causing re-diffusion of the second conductivity type impurity in the single crystal semiconductor layer formed in the above step. The portion of the amorphous semiconductor layer containing first conductivity type impurities from which the melting point metal film has been removed can be converted into a first conductivity type single crystal semiconductor layer. As a result, there is almost no pattern conversion difference with respect to the high-melting point metal film that serves as a mask, and a single crystal semiconductor layer of the opposite conductivity type separated by an isolation region consisting of a single crystal semiconductor layer of a predetermined width is placed on the semiconductor substrate. It can be formed extremely easily and with good reproducibility.
We have discovered a method for manufacturing highly integrated and highly reliable semiconductor devices by forming bipolar transistors and the like in single-crystal semiconductor layers separated by isolation regions of this substrate.

The present invention will be explained in detail below.

First, an amorphous semiconductor layer containing impurities of a first conductivity type is coated on a semiconductor substrate by a CVD method or the like. The impurities in this semiconductor layer are n-type (eg, arsenic, phosphorus, etc.) or p-type (eg, boron, etc.). Furthermore, in coating the amorphous semiconductor layer, there is no need for expensive vapor phase growth equipment that is required for forming conventional epitaxial layers, and there is no need for strict and complicated vapor phase growth control. , is extremely easy to do. Subsequently, a desired portion of the amorphous semiconductor layer is covered with a high melting point metal film by, for example, photolithography. This high melting point metal film acts as an implantation mask during ion implantation of a second conductivity type impurity, which will be described later, and also functions as a mask for laser light by reflecting the laser light during irradiation with laser light. Examples of such high melting point metals include molybdenum, tantalum, and tungsten. A specific example of the amorphous semiconductor portion covered with the high melting point metal film is a portion where an element region is to be formed or a portion where an isolation region is to be formed. The selective coating of these two formation regions may be done depending on the conductivity type of the amorphous semiconductor layer (or the conductivity type of the impurity to be ion-implanted).

Next, using the high melting point metal film as a mask, a second conductivity type impurity is ion-implanted into the exposed amorphous semiconductor layer portion other than the metal film, and then laser light is irradiated. For the purpose of this ion implantation, it is necessary to perform the ion implantation under energy conditions that do not allow the ion to pass through to the semiconductor layer under the high-melting point metal film, but to sufficiently implant the impurity into the exposed portion of the semiconductor layer. The impurity of the second conductivity type is p-type when the impurity in the semiconductor layer is n-type, and is n-type when the impurity in the semiconductor layer is p-type. Laser light irradiation selectively melts the exposed ion-implanted amorphous semiconductor layer and converts it into a second conductivity type single crystal semiconductor layer, meaning that energy is absorbed only in the amorphous semiconductor layer. It is necessary to select the wavelength of the laser beam. Such a laser beam may have a wavelength of 1.06μ, for example.
A Nd-YAG laser beam or the like can be used. Subsequently, after removing the high melting point metal film,
Apply laser light irradiation again. It is necessary to use a laser beam having a wavelength similar to that of the laser beam. The portion of the amorphous semiconductor layer containing impurities of the first conductivity type from which the metal film has been removed by such laser irradiation, that is, the portion of the semiconductor layer in which the impurities of the second conductivity type have not been ion-implanted, is a single crystal semiconductor of the first conductivity type. single crystal semiconductor layers having mutually different conductivity types are formed on the semiconductor substrate. Thereafter, one of these semiconductor layers is used as an isolation region and the other as an element region, and a bipolar transistor, a MOS transistor, etc. are formed in this element region to manufacture a semiconductor device. In addition,
A bipolar transistor (especially
When forming an npn bipolar transistor),
Normally, n is used to reduce the series resistance of the collector.
^{A +} type buried layer was formed between the substrate and the element region, but with recent advances in shallow junction formation technology, the formation of the buried layer becomes unnecessary if the thickness of the single crystal semiconductor layer is reduced.

Next, an example of the present invention suitable for manufacturing a bipolar integrated circuit will be described with reference to the drawings.

Example 1 [] First, as shown in Figure 2 a, the specific resistance is 30~
After depositing a 0.8 μm thick amorphous silicon layer 12 doped with 5×10 ¹⁶ /cm ³ of phosphorus, which is an n-type impurity, on a 50 Ω-cm p ^- type silicon substrate 11, a 1.0 μm thick layer was deposited on the entire surface. An amorphous silicon base layer 1 to be formed into an element formation region by vacuum-depositing a molybdenum film and patterning it by photolithography.
2 was covered with a molybdenum film 13.

[] Next, boron, which is a p-type impurity, is output
After doping the exposed portion of the amorphous silicon layer 12 other than the molybdenum film 13 by implanting ions into the entire surface under the conditions of 50Kev and a dose of 1×10 ¹⁴ /cm ² ,
The entire surface was irradiated with Nd-YAG laser light having a wavelength of 1.06 μm, a pulse width of 200 nsec, and an energy density of 5 J/cm ² . At this time, the portion of the ion-implanted amorphous silicon layer 12 where the molybdenum film 13 does not exist melts and becomes single crystallized by liquid phase epitaxy, and the boron doped near the surface rapidly diffuses to form p ^- type silicon. The p-type isolation region 14 having an impurity concentration of 1×10 ¹⁸ /cm ³ was formed as shown in FIG. 2b. Note that the portion of the amorphous silicon layer 12 under the molybdenum film 13 was not affected by the laser light and remained in an amorphous state.

[] Next, the molybdenum film 13 was removed with a phosphoric acid-based etchant, and again Nd- with a wavelength of 1.06 μm, a pulse width of 200 nsec, and an energy density of 5 J/cm ²
The entire surface was irradiated with YAG laser light. At this time, the portion of the phosphorus-doped amorphous silicon layer 12 exposed by removing the molybdenum film 13 is made into a single crystal by liquid phase epitaxy, and as shown in FIG. 0.8μm
Thus, an n-type epitaxial region 15 (element formation region) was formed with an impurity concentration equivalent to that during silicon deposition. After that, the n-type epitaxial region 1
5, according to the usual method, ρs = 800Ω/□, junction depth
A p type internal base region 16 of 0.5 μm and a p ⁺ type external base region 17 are formed, and furthermore, an n ⁺ type emitter region 18 with ρs = 20Ω/□ and a junction depth of 0.6 μm and a collector region are formed in the internal base region 16. After forming an n ⁺ collector electrode contact region 19 in the n-type epitaxial region 15 as a base, a silicon oxide film 20 is grown and contact holes 21...2 are formed.
Connect the openings in No. 1 and the Al film to the base, emitter, and collector by vapor deposition and patterning.
A bipolar integrated circuit was manufactured by forming Al wirings 22, 23, and 24 (as shown in FIG. 2d).

In the first embodiment, the molybdenum film 13 is used as a mask and the p-type isolation region 1 is
4 and an n-type epitaxial region 15 as an element formation region can be easily formed, and both regions 1 and 15 can be easily formed.
The dimensions of 4 and 15 can be defined with high accuracy depending on the shape of the molybdenum film 13, and a highly integrated and highly reliable bipolar integrated circuit can be manufactured using an extremely simple manufacturing process.

Example 2 [] First, as shown in FIG. 3a, amorphous silicon doped with boron, which is a p-type impurity, at 1×10 ¹⁶ /cm ³ is placed on a p ^- type silicon substrate 11 similar to that in Example 1. After depositing the layer 12' with a thickness of 0.8 μm, a molybdenum film with a thickness of 1.0 μm is vacuum-deposited on the entire surface, and patterned by photolithography to coat the amorphous silicon layer 12', which is to become an isolation region, with molybdenum. It was covered with a membrane 13'.

[] Next, outputs phosphorus, which is an n-type impurity.
After ion implantation into the entire surface under the conditions of 50keV and a dose of 4×10 ¹² /cm ² to dope the exposed amorphous silicon layer 12' except for this film 13' using the masking effect of the molybdenum film 13', the wavelength
1.06μm, pulse width 200nsec, energy density
The entire surface was irradiated with 5J/cm ² Nd-YAG laser light.
At this time, the portion of the ion-implanted amorphous silicon layer 12' where the molybdenum film 13' does not exist melts and becomes single crystallized by liquid phase epitaxy, and the phosphorus doped near the surface rapidly diffuses and p ^- type silicon substrate 11, and the impurity concentration is 3× as shown in FIG. 3b.
10 ¹⁶ /cm ³ , specific resistance 0.2Ω-cm, junction depth 0.8μm
An n-type epitaxial region 15' (element formation region) was formed.

[] Next, the molybdenum film 13' was removed using a phosphoric acid-based etchant, and the entire surface was again irradiated with Nd-YAG laser light under the same conditions as described above.
At this time, the boron-doped amorphous semi-silicon layer 12' exposed by removing the molybdenum film 13' becomes single crystallized by liquid phase epitaxy, and as shown in FIG. 3c, the impurity concentration becomes amorphous. A P-type isolation region 14' was formed at the same time as the silicon layer was deposited. Thereafter, in the same manner as in Example 1, an npn bipolar transistor was formed in the n-type epitaxial region 15', and Al wiring was provided to manufacture a bipolar integrated circuit.

In Example 2, a highly integrated and highly reliable bipolar integrated circuit was also manufactured using an extremely simple manufacturing process.

As detailed above, according to the present invention, a semiconductor substrate is coated with an amorphous semiconductor layer containing a first conductivity type impurity, a high melting point metal film is selectively coated on the semiconductor layer, and the metal film is coated with a high melting point metal film. The isolation region of the single crystal is , the element formation region can be easily formed, and the dimensions of both regions can be precisely controlled by the shape of the high melting point metal film, and by forming transistors etc. in this element formation region, high integration and high reliability can be achieved. This method has remarkable effects such as the ability to manufacture semiconductor devices extremely easily and with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a substrate having an n-type epitaxial layer separated by a p ⁺ isolation region manufactured by a conventional method, and FIGS. Cross-sectional views showing the manufacturing process, FIGS. 3 a to 3 c are Embodiment 2 of the present invention
FIG. 3 is a cross-sectional view showing some steps of the bipolar integrated circuit in FIG. 11...p ^- silicon substrate, 12, 12'... impurity-doped amorphous silicon layer, 13, 13'...
...Molybdenum film, 14, 14'...p type isolation region, 15, 15'...n type epitaxial region (element formation region), 16...p type internal base region, 17...p ⁺ type external base area, 18
... n ⁺ type emitter region, 19 ... n ⁺ type collector electrode contact region, 20 ... silicon oxide film, 22,
23, 24...Al electrode.

Claims (1)

[Claims] 1. A step of coating a semiconductor substrate with an amorphous semiconductor layer containing impurities of a first conductivity type, a step of covering a desired portion of the amorphous semiconductor layer with a high melting point metal film, and a step of covering the high melting point metal film with a high melting point metal film. After selectively ion-implanting a second conductivity type impurity into the amorphous semiconductor portion exposed as a mask, irradiation with laser light is performed, and after removing the high melting point metal film, irradiation with laser light is performed again. 1. A method for manufacturing a semiconductor device, comprising the steps of: