JP3154448B2 - Selective growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selective growth method, and more particularly, to a method in which a source gas is introduced into a processing chamber and is patterned with an insulating material different from a substrate under a pressure environment satisfying a condition of a molecular flow. The present invention relates to a selective growth method for selectively forming a thin film at a desired place on a substrate.

[0002]

2. Description of the Related Art At present, a range from a molecular flow to an intermediate flow (10 to 10) in which the distance from the inner wall of a vacuum vessel is about the mean free path.
UHV-CV to form thin film under pressure condition of ^-5 to 10 ^-3 Torr)
D method exists (semiconductor materials, March 1992, 43-48
page). In this method, no reaction occurs in the gas phase, and thin film formation occurs mainly by chemical reaction of molecules on each surface on the substrate. As a result, each surface material has a characteristic that the time required until film formation is started is different.

For example, when a substrate formed of Si (silicon) is patterned with SiO ₂ (silicon dioxide), under a predetermined condition, Si _{2 is used} as a source gas.
When H ₆ is irradiated on the substrate surface, film formation is first started on the substrate surface appearing in the opening of the pattern, and then after a predetermined time, film formation is started on the SiO ₂ surface. Therefore, by utilizing this characteristic, it is possible to realize selective growth in which a required film is formed only on the substrate surface at the beginning of film formation. This selective growth is selective epitaxial growth.

However, in the above case, when the total amount of the supplied source gas exceeds a certain critical supply amount, the phenomenon of the selective growth described above collapses, and film formation starts at an undesirable place, that is, at the surface of the patterning material. (Published by the American Physical Society,
Appl. Phys. Lett. Vol. 59, 30 September 1991, Numbe
r 14,1735-1736, Jpn. J. Appl. Phys. Vol.31 (1992) p
p.1432-1435). An example of this state is shown by a characteristic graph 31 in FIG. FIG. 3 shows selective growth conditions (substrate temperature dependence) in an insulating material pattern substrate. 31 is SiO ₂ , 3
2 relates to Si ₃ N ₄ .

As shown in FIG. 3, when the source gas is supplied beyond the critical supply amount, nucleation of Si starts on the surface of the patterning material SiO ₂ and selective growth ends. Si
Until the formation of Si nuclei on O ₂ starts, epitaxial growth is selectively performed on the surface of the silicon substrate as described above, and the critical film thickness is determined by the growth rate and the selective growth time at that time. Therefore, the critical supply is a measure of "selectivity". As described above, in the selective growth, since the selective growth phenomenon is determined depending on the total supply amount of the source gas, there is a critical selective growth film thickness. The critical supply amount is determined by the patterning material and the substrate temperature. As shown in a characteristic graph 32 of FIG. 3, when selective growth is performed by irradiating Si ₂ H ₆ (disilane) as a source gas on a Si substrate patterned with, for example, Si ₃ N ₄ , S
Compared with the case where the same selective growth is performed on the Si substrate patterned with iO ₂ (characteristic graph 31), the selectivity is reduced to 1/10 or less. Therefore, depending on the type of the patterning material, there is a case where a practical film thickness cannot be obtained. In the example shown in FIG. 3, although a practical selective growth film can be obtained with the SiO ₂ film pattern,
The case where a sufficient film thickness cannot be obtained with the Si ₃ N ₄ film pattern is shown.

In view of the above problem, a method of adding a trace amount of Cl _{2 has} conventionally been proposed as a method for improving the selectivity (the 38th Annual Meeting of the Physical Society of Japan, Spring Meeting 1990, Proceedings of the 38th Lecture Meeting on Applied Physics). No.1 29a-ZF-6). Trace amount Cl
FIG. 4 shows a characteristic graph obtained by the _two- addition method. This characteristic graph shows the changes in the critical supply amount and the growth rate when the epitaxial silicon growth rate is kept constant while the substrate temperature and the Si ₂ H ₆ flow rate are kept constant, and Cl ₂ is added under these conditions. is there. According to this graph, for example, when the patterning material is Si ₃ N _4, Cl ₂
It can be seen that the selectivity is increased by 50 times only by supplying 0.03 SCCM. Actually, the Cl ₂ supply amount and the growth rate are opposite to each other, and the growth rate becomes 以下 or less, so that the result is that the increase in the substantial selectivity is improved by about 25 times. The reason why the selectivity is improved in this way is that Cl ₂ suppresses the formation of Si nuclei on the surface of the patterning material.

[0007]

As described above, in the conventional method of adding a trace amount of Cl ₂ , the selectivity is improved, but the growth rate is greatly reduced. In particular,
As the flow rate of Cl ₂ is increased, the growth rate sharply decreases. In order to avoid a decrease in the growth rate, the supplied C
l ₂ must be a trace amount of about 0.01 cc / min. Therefore, according to the conventional Cl ₂ addition method, since the supply flow rate of the added gas is inevitably extremely small, it is extremely difficult to accurately control the flow rate of Cl ₂ with an existing flow control device. Having. Therefore, there is a problem that the growth rate cannot be accurately controlled.

It is an object of the present invention to provide a practical selective growth method capable of increasing the growth rate of a selective growth film and accurately controlling the flow rate of an additive gas in the selective growth of an epitaxial film.

[0009]

The selective growth method according to the present invention is directed to a substrate patterned with an insulating film such as SiO ₂ or Si ₃ N ₄ under a pressure range from a molecular flow to an intermediate flow, and The substrate where the silicon surface appears at the pattern opening is irradiated with a silicon hydride such as Si ₂ H ₆ as a source gas, and the silicon surface is selectively exposed to Si.
And Si _1-x Ge _x is a selective growth method of performing the crystal growth of the epitaxial layer, in addition to the irradiation of the source gas, and irradiating the silicon halide compound gas to the substrate. In the above selective growth method, preferably, the silicon-based compound gas is a compound gas of silicon and chlorine or a compound gas of silicon and fluorine.

[0010]

In the selective growth method according to the present invention, a silicon-based compound gas of silicon is introduced as an additive gas, and this halide-based compound gas is thermally decomposed on the substrate to form Si and H.
And Cl or F are formed. Of these, Cl or F
Reduces the nucleation of Si on the insulating film and improves the selectivity. Further, since the halide compound has a low adhesion coefficient, it is necessary to increase the supply amount in order to supply Cl or F necessary for improving the selectivity. Feeding takes place.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a configuration of an apparatus in which a selective growth method according to the present invention is performed. This apparatus is a UHV-CVD apparatus having an improved configuration based on a general MBE apparatus and configured to be able to introduce a gas source. The illustrated portion 1 is a growth chamber, and 2 is a substrate disposed in the growth chamber 1. The substrate 2 is disposed on the substrate support 1a. As shown, the growth chamber is divided into a chamber 1A and a chamber 1B by the substrate 2 and its support 1a. The present apparatus includes, in addition to the growth chamber 1, at least a substrate exchange chamber (not shown) for carrying the substrate 2 into the growth chamber without exposing the substrate 2 to the atmosphere, and the substrate 2 into the growth chamber 1 from the substrate exchange chamber. And a transfer mechanism (not shown).

A substrate heating mechanism 3 is provided in the upper chamber 1A, and a gas introduction mechanism 4 for introducing a source gas and an additive gas is provided in the lower chamber 1B. The substrate heating mechanism 3 includes a heater inside, and heats only the substrate 2 from behind. The source gas and the additive gas blown from the tip of the gas nozzle of the gas introduction mechanism 4 are applied to the processing surface of the substrate 2. The source gas is, for example, Si ₂ H ₆ , and the additive gas is, for example, a halide-based compound gas of Si. Examples of the Si-based compound gas include SiH ₂ Cl ₂
It is. In the illustrated example, the source gas and the additive gas are simultaneously introduced by a common gas nozzle, but the source gas and the additive gas may be introduced by separate gas nozzles. Further, the irradiation time of the source gas and the irradiation time of the additive gas may be made different from each other and introduced.

The substrate 2 is disposed between the chamber 1A and the chamber 1B with its processing surface facing downward. Both chambers 1 by substrate 2
A and 1B are partitioned. The substrate 2 is formed of, for example, silicon. The substrate 2 is not limited to a silicon substrate, but may be any as long as it has a silicon layer at least on its processing surface. On the processing surface of the substrate 2, for example, a patterning material made of an insulating material such as SiO ₂ or Si ₃ N _{4 is} used.
A predetermined pattern having an opening where the substrate surface appears is formed. In the selective growth method of this embodiment, a thin film is selectively formed only on the silicon surface appearing in the opening.
The inner wall surface of each of the chambers 1A and 1B is covered with, for example, a water-cooled shroud 5. Each of the chambers 1A and 1B is provided with an exhaust system including turbo molecular pumps 6 and 7 having a large exhaust speed. The exhaust capacity of the turbo molecular pump 7 is, for example, 1000 l / sec.

By controlling the water-cooled shroud 5 and the inflow of the source gas into the chamber 1A, a complete cold wall of the gas contact surface can be realized. Further, the pressure in the growth chamber at the time of introducing the source gas can be maintained in the range from the molecular flow region of about 10 ^-5 to 10 ^-3 Torr to the intermediate flow region by the exhaust system including the turbo molecular pumps 6 and 7. As a result, the decomposition of the source gas introduced by the gas introduction mechanism 4 in the gas phase is suppressed, the decomposition of the source gas other than the substrate surface is suppressed along with the formation of the cold wall, and the selectivity due to the decomposed source gas is reduced. Deterioration is minimized.

As described above, in forming a thin film by the selective growth method, SiH _{2 is used} as an additional gas in addition to the source gas.
The substrate is irradiated with Cl ₂ and the selectivity at that time (critical supply amount)
The increase and the decrease in the growth rate were measured, and the measurement results are shown in FIG. In FIG. 2, the horizontal axis indicates the flow rate of SiH ₂ Cl ₂ . In this thin film formation, the temperature of the substrate 2 is set to 650 ° C., and the source gas Si ₂ H ₆ is introduced at 3 SCCM. In FIG. 2, a characteristic graph 10 shows a change characteristic of the critical supply amount when the patterning material is SiO ₂ , and a characteristic graph 11 shows a change characteristic of the critical supply amount when the patterning material is Si ₃ N ₄ . Graph 12 shows the change characteristics of the growth rate.

As shown in FIG. 2, the patterning material SiO
₂ and Si ₃ N ₄ , the additive gas SiH ₂
Accordance introduction amount of Cl ₂ increases in the range of about 5～16SCCM, the critical supply amount i.e. selectivity is improved. In addition, the growth rate is shown to be reduced. However, for example, when the patterning material is Si ₃ N ₄ , the growth rate when the critical supply amount is 50 cc shows that the decrease in the film formation rate is maintained at 80% or more. Therefore, in the case of this embodiment, the practical improvement in selectivity is 40 times or more. The flow rate of the additive gas SiH ₂ Cl ₂ at that time is 15 SCCM, which can be said to be a sufficiently practical flow rate in terms of flow rate controllability.

In the above, the additive gas SiH ₂ Cl ₂ is thermally decomposed on the substrate 2 to generate Si, H and Cl. Of these, Cl acts on the patterning material in the same manner as the conventional Cl ₂ addition method, and improves the selectivity. Also Si
Above, the precipitation of Si precipitated from SiH ₂ Cl ₂ contributes to the growth, and suppresses a decrease in the growth rate due to Cl ₂ . Therefore, selectivity can be further improved. Further, since SiH ₂ Cl ₂ has a low adhesion coefficient, in order to supply Cl necessary for improving selectivity, it is necessary to supply more than the conventional Cl ₂ gas supply amount. The gas supply in the area becomes possible. in this way,
The SiH ₂ Cl ₂ addition method according to the present embodiment is a selective growth method capable of obtaining a sufficiently practical selective growth film thickness and a practical flow rate control method.

The effect of the above embodiment is that SiH ₂ Cl
_The selectivity is not limited to ₂ , and the selectivity can be similarly improved with another compound gas of Si and Cl.

It has been reported that selectivity is improved by adding a small amount of F ₂ gas (Hiroi et al .: Japan Society of Applied Physics Autumn 1991, 11a-Z-6). Accordingly, similar effects can be obtained by using Si and F (fluorine) -based compound gas as in the case of Cl ₂ gas.

[0020]

As is apparent from the above description, according to the present invention, in a selective growth method by gas source epitaxial utilizing a UHV-CVD apparatus, a silicon halide compound gas is added to a substrate with a source gas together with a source gas. By irradiating the treated surface, it is possible to improve the selectivity by suppressing the decrease in the growth rate, and to increase the flow rate of the added gas to realize a practical selective growth method capable of controlling the flow rate. Can be.

[Brief description of the drawings]

FIG. 1 shows a UHV in which a selective growth method according to the present invention is performed.
FIG. 2 is a configuration diagram of a CVD apparatus.

FIG. 2 is a graph showing characteristics of a critical supply amount and a growth rate by a selective growth method according to the present invention.

FIG. 3 is a graph showing characteristics of a critical supply amount according to a conventional selective growth method.

FIG. 4 is a graph showing characteristics of a critical supply amount and a growth rate by a conventional trace amount Cl ₂ addition method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Growth chamber 1A, 1B ... Chamber 2 ... Substrate 3 ... Substrate heating mechanism 4 ... Gas introduction mechanism 5 ... Water-cooled shroud 6, 7 ... Turbo molecular pump

Claims (2)

(57) [Claims] 1. A substrate, which is patterned with an insulating film and has a silicon surface appearing in a pattern opening, is irradiated with a hydrogenated compound of silicon as a source gas under a pressure range from a molecular flow to an intermediate flow. In a selective growth method for selectively growing a crystal of an epitaxial layer, in addition to the irradiation of the source gas, the substrate is irradiated with a halide compound gas of silicon. 2. The selective growth method according to claim 1, wherein
The selective growth method, wherein the halide-based compound gas is a compound gas of silicon and chlorine or a compound gas of silicon and fluorine.