JPH065541A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for filling a slit with polycrystalline Si having a low resistance and a very small crystal grain to form an electrode. CONSTITUTION:In selectively growing polycrystalline Si, a spontaneous oxide film 5 is removed from a slit 3 in an insulating film, and carbon monooxide or dioxide is fed to the slit to form a SiC/Si oxide mixture layer 6 on the clean exposed Si face before doing so. In this case the formation of the mixture layer is in a pretreatment process prior to the start of the selective growth. However, it may be in an intermediate process: the feed of Si material gas (silane gas) is interrupted in the course of the selective growth, and carbon monooxide or dioxide is fed instead.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method for forming an electrode by selectively growing a polycrystalline Si film in an opening provided in an insulating film on a silicon (Si) substrate. It relates to a method of forming.

[0002]

2. Description of the Related Art Conventionally, the opening of an insulating film on a Si substrate is
As a technique for selectively burying with a film, selective epitaxial growth of Si single crystal is widely known. The selective growth itself is performed by using a silane-based gas (for example, SiH ₂
This is achieved by controlling the flow rate ratio between Cl ₂ ) and the etching gas (for example, HCl) to adjust the balance between growth and etching. That is, selective growth becomes possible by etching the nuclei of Si deposition (very small Si particles) formed on the insulating film while maintaining the Si growth in the openings.

However, in recent years, in order to form the polycrystalline Si emitter electrode employed in the ultra-high speed bipolar transistor in a self-aligned manner, a technique of selectively growing polycrystalline Si in the emitter opening has become important. .

This is because impurities in polycrystalline Si (for example,
Since the diffusion coefficient of As is larger than that of single crystal, it is advantageous to form a shallow emitter by heat treatment at low temperature for a short time, and prevents unfavorable carrier injection at the interface of polycrystalline Si / Si substrate. This is due to the formation of a protective barrier, and a device application example by Aoyama et al. Has also been reported (T. Aoyama et al. “S.
elective Polysilicon Depo
position (SPD) by Hot-Wall L
PCVD and Its application
to HighSpeed Bipolar Devi
ces ”, Extended Abstracts o
f the 22nd Conference on
Solid State Devices and M
materials, 1990, pp665).

In this report, selective growth of polycrystalline Si is realized in a reaction temperature range of 750 to 850 ° C. using a mixed gas system of SiH ₂ Cl ₂ / HCl / H ₂ . At this time, under a constant growth temperature / pressure condition, if the HCl mixing ratio is made small, the growth rate increases, but if the ratio is made smaller than the critical mixing ratio, the selectivity is impaired. In addition, when the mixing ratio of HCl is increased, the growth rate is significantly reduced, and the growing polycrystalline Si
Has a large crystal grain size and has a crystal structure of a film similar to a single crystal containing many crystal defects. Therefore, the HCl mixing ratio is adjusted to selectively grow polycrystalline Si having crystal grains as small as possible while maintaining a high growth rate.

Further, in order to prevent single crystallization of the selectively grown film, a reaction gas for growth (eg, SiHCl ₃ / H) is used.
A method has been proposed in which a compound containing nitrogen, oxygen, and a carbon atom (for example, ammonia gas) is added to ₂ mixed gas) to prevent single crystallization of Si and polycrystallize (JP-A-61-1).
No. 31434). This is because Si nitride is formed in the selectively grown Si film, which hinders the epitaxial growth of Si.

[0007]

However, in the conventional polycrystalline Si selective growth, the range of the selectable HCl mixing ratio is narrow, and a slight change in the surface state of the selective growth substrate (for example, an extremely small amount of organic system). Due to the adhesion of impurities, the variation in the growth of the natural oxide film, etc., the selectivity is impaired, or the grown polycrystalline Si crystal grains become large. There is a problem that

Further, in the method of mixing nitrogen, oxygen and carbon into the reaction gas, Si nitride, oxide and carbide for inhibiting epitaxial growth are incorporated into the grown polycrystalline Si film at a high density. In addition, there arises a problem that the electric resistance does not decrease even if impurities such as As are doped.

The present invention has been made to solve the above problems inherent in the prior art. Therefore, the object of the present invention is to bury an opening with polycrystalline Si having a low electric resistance and small crystal grains. Another object of the present invention is to provide a novel method for manufacturing a semiconductor device capable of forming electrodes.

[0010]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention is provided with polycrystalline Si.
In selective growth, hydrogen or hydrogen chloride / hydrogen mixed gas is used to remove the natural oxide film in the insulating film opening, and carbon monoxide or carbon dioxide is supplied to this insulating film opening to clean these exposed Si surfaces. After adsorbing and reacting
It is characterized by performing selective growth. At this time, the adsorption of carbon monoxide or carbon dioxide should be performed in a pretreatment step before the start of selective growth, or the supply of Si source gas (silane-based gas) should be interrupted during the selective growth to remove carbon monoxide or carbon dioxide. This is an intermediate treatment step of flowing.

[0011]

The carbon monoxide or carbon dioxide adsorbed on the exposed Si surface selectively reacts with the underlying substrate (Si) to form a mixture of polycrystalline Si carbide (SiC) and Si oxide, which is opened in the next step. When Si is grown by the silane-based gas supplied to the substrate, this mixture prevents the continuity of the crystal lattice of the underlying substrate (silicon single crystal) from being transmitted to the selectively grown silicon film. The growing Si film is polycrystallized. In addition, the mixture of SiC and Si oxide forms an extremely thin layer due to the heat treatment performed during the growth, and since excess Si is supplied from the interface between the substrate and the selective growth film, the substrate and the selective growth film are almost composed of silicon. It will be in a bonded state and will not form a strong barrier that raises the electrical resistance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be specifically described with reference to the drawings for each of its preferred embodiments.

1A to 1D are process diagrams showing a first embodiment according to the present invention.

Referring to FIGS. 1 (a) to 1 (d), S is formed on an n-type Si substrate 1 by thermal oxidation or chemical vapor deposition.
An i-oxide film 2 is formed, and an opening 3 is further provided by a usual photolithography and etching technique. Then, the n-type diffusion layer 4 is formed in the opening 3 and introduced into the low pressure vapor phase growth apparatus. At this time, a natural oxide film 5 of about 1 nm is formed on the n-type diffusion layer 4 (see FIG. 1A).

Subsequently, hydrogen was introduced into the reduced pressure vapor phase growth apparatus and treated at 850 ° C. and 0.5 torr to form the natural oxide film 5.
Carbon dioxide / inert gas (eg argon,
Introduce a mixed gas of helium and nitrogen) at 850 ° C., 1 to
Carbon dioxide is adsorbed and reacted on the n-type diffusion layer by rr.
At this time, the concentration of carbon dioxide in the mixed gas and the temperature during adsorption
The pressure can be set arbitrarily, but it is necessary to adjust so that the layer 6 of the mixture of SiC and Si oxide is formed at a thickness of several nm, preferably 2 nm or less at the bottom of the opening at the same time when the mixed gas is introduced (Fig. 1 (b)).

Thereafter, a mixed gas of dichlorosilane / hydrogen chloride / hydrogen (SiH ₂ Cl ₂ / HCl / H ₂ ) is flown to selectively grow the polycrystalline Si 7 only in the openings (see FIG. 1 (c)). . The growth conditions at this time are as follows.

Gas flow rate SiH ₂ Cl ₂ 400 sccm HCl 350 sccm H ₂ 10 SLM Growth temperature / pressure 800 ° C./100 to
rr After that, arsenic is ion-implanted at 70 keV and 5 × 10 ¹⁵ / cm ² , and heat treatment is performed at 1000 ° C. for 5 minutes to form the wiring 8 with a metal such as aluminum (see FIG. 1D).

Table 1 shows the contact resistance in the first embodiment, and the reference sample is a sample in which the opening is buried by the conventional technique of mixing ammonia with the source gas for Si selective growth.

[0019]

[Table 1] ─────────────────────────────── Mixture thickness (nm) Resistance (Ω) ──── ─────────────────────────── Example 1 1 20 to 45 2 20 to 50 4 45 to 80 6 80 to 150 10 100 to 200 Prior art −400 to 2000 ─────────────────────────────── The contact size at this time is 0.8 μm × 1. 5 μm
Is.

In the present invention, 20 to 20 per unit contact
While a resistance value of 200Ω was obtained, a resistance value as high as 400 to 2000Ω was obtained by the conventional technique. Also, it can be seen that if the thickness of the mixture layer of SiC and Si oxide is 2 nm or less, the resistance value per unit contact can be stably suppressed to 50Ω or less.

Further, as a result of observing the crystal grains of the selectively grown Si with a transmission electron microscope in the case of not forming a layer of a mixture of SiC and Si oxide and in the case of this embodiment, in the present embodiment, a width of 0. Columnar crystal grains of about 2 to 0.5 μm were observed, but almost no crystal grain boundaries were observed when the layer of the mixture of SiC / Si oxide was not formed. It was confirmed that it was effective in forming a polycrystal of fine crystal grains.

Although carbon dioxide was used to form the mixture layer of SiC and Si oxide in this example, the same result can be obtained by using carbon monoxide. It is also possible to use pure gas as these gases.

2 (a)-(d) show a second embodiment of the present invention.
FIG. 6 is a process drawing showing an example of FIG.

Referring to FIGS. 2A to 2D, a Si oxide film 12 is formed on a p-type Si substrate 11 by thermal oxidation or chemical vapor deposition, and then ordinary photolithography and etching techniques are used. The opening 13 is provided by. Subsequently, the n-type diffusion layer 14 is formed in this opening and introduced into the low pressure vapor phase growth apparatus. At this time, the natural oxide film 15 of about 1 nm is formed on the n-type diffusion layer (see FIG. 2A).

Subsequently, a hydrogen chloride (1%) / hydrogen mixed gas was introduced into the reduced pressure vapor phase growth apparatus, and 850 ° C., 0.5 t.
Then, the natural oxide film on the n-type diffusion layer is removed. At this time, it is possible to use hydrogen fluoride or hydrogen fluoride / hydrogen vapor mixed gas in place of the hydrogen chloride / hydrogen mixed gas, but when using these gases, the treatment temperature should be a low temperature near room temperature. .

Next, a first Si selective growth film 16 having a thickness of 5 nm is formed in the opening under the same conditions as in the first embodiment (see FIG. 2B).

Next, a carbon monoxide / inert gas (eg, argon, helium, nitrogen) mixed gas is introduced 850.
Carbon monoxide is adsorbed and reacted on the exposed Si portion at the bottom of the opening at 1 ° C. and 1 ° C. Also in this case, the concentration of carbon monoxide in the mixed gas and the temperature / pressure at the time of adsorption can be set arbitrarily, but in order to realize low resistance, at the same time when the mixed gas is introduced, a mixture of SiC and Si oxide 17 is formed at the bottom of the opening. Is preferably 2 nm
It is necessary to adjust it so that it is formed with the following thickness (see FIG. 2C).

Then, a second Si selective growth film 18 is formed under the same conditions as the above-mentioned Si selective growth film formation. At this time, the second Si selective growth film 18 becomes polycrystalline Si as in the first embodiment. After this, arsenic was changed to 70 keV, 5 × 10 ¹⁵ /
Ion implantation is performed at a cm ² and heat treatment is performed at 1000 ° C. for 5 minutes to form the wiring 19 with a metal such as aluminum (see FIG. 2D).

In the second embodiment, the selective growth of Si is performed in two steps.
It differs from the first embodiment in that it is performed in stages. First
The position where the mixture of SiC and Si oxide is formed by the selective Si growth of Si is raised above the position where it was originally the surface of the Si substrate, and the strain caused by the mixture of SiC and Si oxide is directly generated on the Si substrate. Will not reach.
As a result, generation of crystal defects that cause pn junction leakage is suppressed.

Table 2 shows the results of measuring the pn junction leak in the comb-shaped diffusion layer having an area of 1 × 10 ^-2 cm ² and a perimeter of 40 cm, using the reference sample of the first embodiment. The leak current of this example was 1 to 6 × 10 ⁻⁹ A / cm ² , whereas the leak current of the reference sample was 5 to 75 × 10 ⁻⁹ A / cm ² ,
It was confirmed that the pn junction leakage can be reduced by the second example.

[0031]

[Table 2] ─────────────────────────── Leakage current ───────────────── ────────── Example 1-6 × 10 ^-9 A / cm ² Reference sample 5-75 × 10 ^-9 A / cm ² (first example) ─────── ──────────────────── In addition, although carbon monoxide was used for forming the mixture layer of SiC and Si oxide in this example, carbon dioxide may be used. Simultaneous results can be obtained. Further, as in the first embodiment, it is possible to use pure gas.

[0032]

As described above, according to the present invention,
Prior to the selective growth, the natural oxide film grown on the exposed Si surface to be selectively grown is removed, and a mixed layer of SiC / Si oxide is formed, and then Si is selectively grown to form a microcrystal of the grown film. The contact resistance can be lowered by using polycrystal grains.

Further, according to the present invention, Si selective growth is performed to 2
By dividing into stages and forming a mixture layer of SiC / Si oxide after the first Si selective growth, it becomes possible to reduce the leak current of the pn junction under the Si selective growth film.

[Brief description of drawings]

1A to 1D are schematic views showing steps of a first embodiment according to the present invention.

2 (a) to (d) are schematic views showing steps of a second embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... n-type Si substrate 2 ... Si oxide film 3 ... opening 4 ... n type diffusion layer 5 ... natural oxide film 6 ... SiC / Si oxide mixture layer 7 ... polycrystalline Si 8 ... Al wiring 11 ... p type Si Substrate 12 ... Si oxide film 13 ... Opening portion 14 ... N-type diffusion layer 15 ... Natural oxide film 16 ... First Si selective growth film 17 ... SiC / Si oxide mixture layer 18 ... Second Si selective growth film 19 ... Al wiring

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device in which polycrystalline silicon is selectively grown only in an exposed opening of a silicon substrate provided in an insulating film on a silicon substrate, wherein natural oxidation formed on the bottom surface of the opening. A method of manufacturing a semiconductor device, which comprises selectively growing polycrystalline silicon after a step of removing a film and a step of forming a mixture layer of silicon carbide / silicon oxide on a bottom surface of the opening. 2. A method of manufacturing a semiconductor device in which silicon is selectively grown only in an exposed opening of a silicon substrate provided in an insulating film on a silicon substrate, wherein a natural oxide film formed on a bottom surface of the opening is formed. Selective growth of polycrystalline silicon is performed after a step of removing, a step of forming a silicon selective growth film on the bottom surface of the opening, and a step of forming a silicon carbide / silicon oxide mixture layer on the silicon selective growth film. A method for manufacturing a semiconductor device, comprising: 3. The method for manufacturing a semiconductor device according to claim 1, wherein the step of removing the natural oxide film is performed in an atmosphere of hydrogen or hydrogen chloride / hydrogen mixed gas. . 4. The step of forming the mixture layer of silicon carbide / silicon oxide comprises carbon monoxide, carbon dioxide, a mixed gas thereof, or a gas atmosphere obtained by diluting these single gases or mixed gas with an inert gas. 3. The method according to claim 1, further characterized in that
The method for manufacturing a semiconductor device according to any one of 1.