JPS629627A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable to easily diffuse impurities on a semiconductor substrate at a low temperature by a method wherein a compound layer consisting of impurity atoms and oxygen atoms is formed on the semiconductor substrate by performing a low-temperature processing, and impurity atoms are diffused on the semiconductor substrate by the use of the chemical layer as an impurity diffusion source. CONSTITUTION:A p-type a-Si film 2 is formed on a glass substrate 1 by performing a plasma CVD method. Then, after a POx film 3 is formed by performing a plasma CVD method using the mixed gas of PH3 and N2O (or O2), a mask 4 consisting of a metal is formed, and a laser beam is made to irradiate. As a result, the P contained in the POx film 3 is diffused into the a-Si film 2, and an n-layer 6 corresponding to the aperture 4a of the mask 4 is formed. Then, the mask 4 is removed by etching, and after the POx film 3 is removed by rinsing, electrodes 7 and 8 are formed on the a-Si film 2 and the n-layer 6 respectively, and the desired p-n junction diode is formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device,
It is most suitable for use in forming diffusion layers on Si and other various semiconductor substrates.

[Summary of the invention]

The present invention provides a method for manufacturing a semiconductor device, in which a compound layer of impurity atoms and oxygen atoms is formed on a semiconductor substrate by a low-temperature process, and the impurity atoms are diffused into the semiconductor substrate using this as an impurity diffusion source. This method makes it possible to easily diffuse impurities into a semiconductor substrate at low temperatures.

[Conventional technology]

Conventionally, amorphous Si (a-3i), polycrystalline S
The following method is used to form an n layer or a p layer in i s single crystal Si or the like. In the first method, a mixed gas of SiH and PH3 is used to form the n-layer, and Si If is used to form the p-layer.
It is formed by vapor phase growth using a mixed gas of a and BtHi. The second method is to form an n layer and pIW by ion-implanting PSB or the like into Si.

The third method is to form a PSG film or a BSG film on Si, and then perform heat treatment to diffuse P or B in these films into Si to form an n-layer or phi.

C Problems to be Solved by the Invention] However, in the first method described above, since the growth is from a gas phase, a lateral pn junction (or pi, ni junction) is formed.
cannot be formed. Further, the second method not only requires heat treatment at a temperature of 600° C. or higher to activate the ion-implanted impurities, but also has the disadvantage of being expensive. Furthermore, the third method not only requires heat treatment at a temperature of 600°C or higher like the second method, but also requires a PSG film or BS film to take out the electrode.
There is a drawback that a step of etching the G film is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that corrects the above-mentioned drawbacks of the prior art.

[Means for solving problems]

The inventors of the present invention have conducted extensive research to correct the shortcomings of the prior art as described above, and have discovered the following phenomenon.
The present invention has been devised. That is, first, for example, an a-Si film is formed on, for example, a glass substrate, and then pH 3 and N
, O (or 0□) (e.g. PH+/Nz
Plasma C using O≧0.001) as a reaction gas
Vapor phase growth is performed at low temperature using the VD method. As a result, a POX film is formed on the a-Si film described above. Next, the a-5i film is melted by locally heating the vicinity of the P OX /a Si interface using light having a wavelength that is strongly absorbed by Si, such as a laser beam from an excimer laser. As a result, P in the PoX film is diffused into the a-Si film to form an n layer, and activation is also performed at the same time.

Polycrystalline Si film, single-crystalline Si film is used instead of the above-mentioned a-Si film.
Even when a film or the like is used, the n-layer can be formed in the same manner. In addition, in the plasma CVD mentioned above, B2H4 and N
If a mixed gas with 20 (or OX) is used as a reaction gas, a BOX film will be formed on the a-5i film, so a p layer can be formed by diffusing B in this PoX film into Si. I can do it.

Moreover, both the above-mentioned POX film and BOX film can be easily removed by washing with water, which is advantageous.

FIG. 4 shows an example of the conductivity of an a-5i film in which impurities were diffused using the above-mentioned PO film as an impurity diffusion source.

As is clear from FIG. 4, the a-Si film immediately after formation has a dark conductivity of 10-'' (0 cm)-' and a bright conductivity of 1.
0-' (100 mV/c+a), P was diffused from the POヮ film into the a-5i film by irradiating it with an excimer laser beam (energy density: e.g. 230 mJ/cd) at room temperature. Later, 2(Ωa
A high electrical conductivity of n)-' or higher was obtained. Figure 4 also shows the conductivity of the a-Si film immediately after the formation of the POX film and the conductivity of the a-5i film after the POX film was removed by washing without laser beam irradiation. .

From these measurement results, the dark conductivity was 10-3 (0 cm)-' immediately after forming the POX film, and the dark conductivity and bright conductivity were It can be seen that both the conductivity values are the same as those immediately after the a-Si film was formed.

Although the reaction formula for forming the above-mentioned POX film and BO film is not yet clear, for example, PO.

The membrane is: nPH, + nN, o −=(PO,), + nN
! I.

It is thought to be formed by a plasma polymerization reaction in a mixed gas of PH, N, and O, as shown in the following.

(pot) in the above formula is a deliquescent crystal thin film and is transparent. This (PO□) film is composed of molecules such as P2O3 or P, 01°, and additionally contains H and P in addition to poz. It is thought that these molecules are decomposed by ultraviolet light or heat and P is diffused into the semiconductor.

The present invention was devised based on the above-mentioned experimental results.

That is, in the method for manufacturing a semiconductor device according to the present invention, a compound layer of impurity atoms and oxygen atoms (for example, POX film 3) is formed on a semiconductor substrate (for example, p-type A-5T film 2) by a low-temperature process. The impurity atoms are diffused into the semiconductor substrate using the compound layer as an impurity diffusion source.

〔Example〕

Embodiments of the method for manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings.

First, a first embodiment in which the present invention is applied to manufacturing a vertical pn junction diode will be described.

As shown in FIG. 1A, first, for example, a p-type a-Si film 2 is formed on a glass substrate 1 by the plasma CVD method, and then a PHI film is formed on this a-5i film 2 by the same method as described above. After forming PO and film 3 by the plasma CVD method using a mixed gas with N20 (or OX), a metal such as AI%MO is patterned into a predetermined shape by a photoresist process on this PO and film 3. A mask 4 is formed.

Next, as shown in FIG. 1B, a laser beam 5 such as an excimer laser is irradiated using the mask 4. As a result, P in the POX film 3 is diffused into the a-Si film, and a zero layer 6 is formed corresponding to the opening 4a of the mask 4.

Next, after removing the mask 4 by etching and further removing the PoX film 3 by washing with water, as shown in FIG.
Electrodes 7.8 are formed on the i-film 2 and the 0-layer 6, respectively, to form the intended pn junction diode.

According to the first embodiment described above, POx on the a-Si film
A film 3 is formed, and then a laser beam 5 is irradiated with a mask 4 formed on this PoX film 3 to diffuse it from the POX film 3 into the Pt-a-5i film 2, thereby forming a 0 layer 6. Therefore, the O layer 6 can be easily formed at room temperature, and therefore a diode can be manufactured on the low melting point glass substrate 1 by a low temperature process. Further, there is no need to perform ion implantation or high-temperature heat treatment as in the past, and therefore manufacturing costs can be reduced. Furthermore, the above-mentioned POX film 3 can be easily removed by washing with water as described above, which is extremely advantageous in manufacturing.

Next, a second embodiment in which the present invention is applied to manufacturing a lateral pn junction diode will be described.

As shown in FIG. 2A, first, a sufficiently thin p-type a-Si film 2 is formed on a glass substrate l, and then PO, film 3 and a mask of a predetermined shape are formed in the same manner as in the first embodiment described above. form 4.

Next, as shown in FIG. 2B, a laser beam 5 is irradiated using a mask 4 as in the first embodiment.

As a result, there is 0 in the a-5i film 2 throughout the film thickness direction.
Layer 6 is formed.

Next, after removing the mask 4 by etching and further removing the POX film 3 by washing with water, a-3i is removed as shown in FIG. 2C.
Electrodes 7 and 8 are formed on the membrane 2 and the 0 layer 6, respectively, to complete the desired lateral pn junction diode.

According to the second embodiment, in addition to the same advantages as the first embodiment, there is a disadvantage that a lateral pn junction, which is difficult to realize using conventional methods, can be easily formed.

Next, a third example in which the present invention is applied to the manufacture of pnp transistors.
An example will be explained.

As shown in FIG. 3A, first, a p-type a-St film 2 and a POX film 3 are formed on a glass substrate l in the same manner as in the second embodiment, and then a mask 4 of a predetermined shape is formed on this POX film 3. form.

Next, as shown in FIG. 3B, using mask 4, L/-q
- irradiate beam 5; As a result, a narrow 0 layer 6 is formed corresponding to the opening 4a of the mask 4 in the a-Si film. Note that this 0 layer 6 constitutes a base, and the p-type a-3i films 2a and 2b present on both sides of this 0 layer 6 constitute an emitter and a collector, respectively.

Next, mask 4 is removed by etching, and then PO is applied.

After removing the membrane 3 by washing with water, a
St film 2b, 0 layer 6 and a Si film 2a with electrode 7
.about.9 are respectively formed to complete the desired pnp transistor.

According to this third embodiment, there are advantages similar to those of the first and second embodiments.
p) A transistor can be easily formed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the three embodiments described above, and various modifications can be made based on the technical idea of the present invention. For example, in the three embodiments described above, the p-type a-5i film 2 and the PO
It is also possible to use an n-type a-5i film and a B Ox film instead of 8O2O3.

In this case, diodes with p and n reversed in FIGS. 1C and 2C are obtained for the first and second embodiments, and an npn transistor is obtained for the third embodiment. Furthermore, in the three embodiments described above, a mask 4 is formed on the POX film 3, and the 0 layer 6 is formed at a desired position on the a-Si film 3 by irradiating the laser beam 5 using this mask 4. However, it is also possible to form the 0 layer 6 by, for example, placing a photomask on which a mask pattern of a predetermined shape is formed on the POX film 3 or irradiating it with the laser beam 5 while bringing it close to the POX film 3. be. This has the advantage that the photoresist process for forming the mask 4 can be omitted.

In addition, the a-3i film 3 used in the above three examples
Polycrystalline stl instead! It is also possible to use a single crystal Si film, or even a semiconductor film other than St if necessary. Similarly, it is also possible to use a Si substrate, a quartz substrate, etc. in addition to the glass substrate l. Not only that, but also P on the Si substrate.
It is also possible to form a desired diffusion layer in the Si substrate by directly forming an OX film or the like. Furthermore, in the three embodiments described above, a laser beam by an excimer laser was used as a heating source for impurity diffusion, but if necessary, laser beam irradiation by a YAG laser, ruby laser, etc., or electron beam irradiation could be used. irradiation,!
R irradiation or the like may also be used.

Furthermore, the removal of the POX film 3 (or 80g film) can also be performed by a method other than washing with water, such as wet etching or dry etching using a predetermined etching solution.

Note that in the three embodiments described above, the present invention was applied to a diode and a transistor.
The present invention can also be applied to other semiconductor devices.

〔Effect of the invention〕

According to the method for manufacturing a semiconductor device according to the present invention, it is possible to easily diffuse impurities into a semiconductor substrate at a low temperature, and the method can be adapted to a low-temperature manufacturing process. Furthermore, it is also possible to form a lateral pn junction if necessary.

[Brief explanation of drawings]

1A to 1C are cross-sectional views showing the first embodiment in which the present invention is applied to manufacturing a vertical pn junction diode. 3A to 3C are cross-sectional views showing, in order of process, a third embodiment in which the present invention is applied to the manufacture of a pnp) transistor, and FIG. 3 is a graph showing changes in electrical conductivity of an a =Si film due to formation of a POX film and subsequent laser beam irradiation. In addition, in the symbols used in the drawings, 1. ---
−−−−−−−−−−−1・po, membrane 5−−−−−・−
・・−・−Laser beam 6−・−−−1−−−−−
--...-n layer.

Claims (1)

[Claims] Manufacturing a semiconductor device, characterized in that a compound layer of impurity atoms and oxygen atoms is formed on a semiconductor substrate by a low-temperature process, and the impurity atoms are diffused into the semiconductor substrate using the compound layer as an impurity diffusion source. Method.