JP2821563B2 - Compound crystal epitaxial growth method and doping method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for epitaxially growing a compound crystal and a method for doping the same. The present invention relates to a doping method for epitaxial growth of a compound crystal having strict control of dopant impurities in addition to control of film thickness on the order.

[0002]

2. Description of the Related Art Conventionally, for example, as a technique for growing a thin film crystal of a semiconductor, molecular beam epitaxy (Mol-ecular Beam Epitaxy) has been known.
axy (hereinafter referred to as MBE) or Metal Organic-Chemical Vapor Deposition
, Hereinafter referred to as MO-CVD) and the like. In particular, in the case of compound semiconductors, these methods have been frequently used for manufacturing semiconductor devices.

[0003] The MO-CVD is widely used because it has a relatively simple structure and requires an inexpensive apparatus, has a high growth rate and a short growth time, and has excellent mass productivity. The growth film thickness could not be controlled by the layer order.

In this doping technique by MO-CVD, a compound gas of a constituent element of a semiconductor is formed on a substrate crystal.
The dopant compound gas is introduced at the same time. The MBE uses a method in which the vapor is deposited on the substrate crystal while controlling the molecular beam by heating and evaporating the raw material. The crystal thickness is extremely thin, and the composition, profile and crystal growth rate are sufficiently controlled. So you can
The controllability of the grown film thickness is superior to that of MO-CVD.

In the doping method in the MBE, vapor of a dopant element is vapor-deposited together with vapor of a constituent element as a raw material on a substrate crystal. This MB
In order to obtain a good quality crystal by E, for example, in the case of GaAs, it is necessary to set the crystal growth temperature to a high temperature of 500 to 600 ° C., and when the temperature is high, a steep impurity profile such as npn or pnp is produced Is a problem that impurities are redistributed. Furthermore, since MBE is based on a vapor deposition method, there has been a problem that the growth film has a deviation from the stoichiometric composition and a high density of surface defects such as oval defects.

Due to these inconveniences, in recent years, molecular layer epitaxy (Mo) having film thickness controllability on the order of a monolayer has been proposed.
(Lecular Layer Epitaxy, hereinafter referred to as MLE) is attracting attention. In the case of crystal growth of a III-V compound, the MLE is a method in which a group III compound gas and a group V compound gas are alternately introduced onto a substrate crystal to grow the crystal in a monomolecular layer.

This technique is described, for example, in J. Nishizawa, H. Abe and T. Kurabayashi;
electrochem. Soc. 132 (1985) 1197-1200 ". The above-mentioned MLE utilizes a compound gas adsorption and a surface reaction. For example, in the case of a group III-V crystal, a monomolecular film growth layer is obtained by introducing a group III compound gas and a group V compound gas once each. .

As described above, since the MLE utilizes the adsorption of a compound gas to a monolayer, the MLE can always be grown in the order of monolayers within a certain pressure range even when the pressure of the introduced gas changes. Further, this MLE is used for growing a GaAs crystal such as trimethylgallium (TMG), which is an alkyl gallium, and arsine (As, a hydrogen compound of arsenic).
Although H ₃ ) has been used, a high-purity GaAs growth layer can be obtained at a lower temperature by using triethylgallium (TEG), which is an alkyl gallium, instead of the TMG.

This technique is described in, for example, J. Nishizawa, H. Abe, T. Kuraba-yashi & N. Sakura et al.
i. J. Vac. Sci. Technol. A4 (3), (1986) 706-710. In addition, the above-mentioned doping method of GaAs by MLE is performed by sequentially introducing a compound gas of a dopant into a substrate crystal surface in addition to a compound gas of TEG and AsH ₃ . This makes it possible to obtain a high-purity crystal whose impurities are controlled, such as a high-doped crystal, at a low temperature.

Further, since the MLE grows a crystal film at a low temperature, the redistribution of impurities is very small, and a steep impurity profile can be realized. This technology is described in, for example, J. Nishizawa, H. Ab.
e and T. Kurabayashi; J. Electrochem. Soc. Vol. 136,
No. 2 pp. 478-484 (1989) ".

[0011]

By the way, for example, in order to obtain a high-speed semiconductor device, it is necessary to obtain a growth film having a higher impurity concentration and to realize crystal growth at a lower temperature. come. Therefore, it is desired to further improve the doping method in the molecular layer epitaxial growth.

In view of the above-mentioned problems, an object of the present invention is to provide a reaction based on the basic concept of molecular layer epitaxy.
Reaction occurs at low temperatures due to the environment in which
And remove the functional groups from the surface adsorbate to remove
A method of epitaxially growing a compound crystal that enables high-purity crystals to be obtained at low temperature by efficiently fixing the crystals to the surface , and a method of forming a monolayer with a high-concentration impurity density that is strictly controlled at low temperatures. An object of the present invention is to provide a doping method in epitaxial growth of a compound crystal which can be obtained on the order.

[0013]

SUMMARY OF THE INVENTION According to the method of the present invention, there is provided, in accordance with the method of the present invention, group III and V on a substrate crystal heated in vacuum.
In a compound crystal epitaxial growth method in which a plurality of crystal component gases of a compound such as a group element are introduced in a predetermined order to grow a single crystal, a chemical reaction with a crystal component gas is performed to form a surface.
This is achieved by simultaneously introducing at least one of the plurality of crystal component gases with a reaction gas for removing the functional group of the adsorbate .

According to the doping method for epitaxial growth of a compound crystal of the present invention, a crystal component gas of a compound such as a group III element or a group V element and Si, Ge, S, In a doping method in the epitaxial growth of a compound crystal in which a single crystal is grown by introducing a compound gas of a dopant such as Se, Te, Zn, Cd, and Mg in a predetermined order, one of the crystal component gases is used. Chemical reaction with crystal component gas simultaneously with introduction of crystal component gas
This is achieved by introducing a reaction gas which removes the functional groups of the surface adsorbate . Further reaction gas, previously on the substrate
Dopa different from the compound gas of the dopant introduced
Different types of organometallic compounds or hydrides
Characterized by being a compound gas of a dopant of
It is. In addition, the reactant gas is
-Same dopant as compound gas of punt but different
Of organometallic compounds or hydride dopants
It is characterized by being a material gas.

[0015]

According to the above construction, a reactive gas is introduced onto a substrate crystal heated in a vacuum in addition to a gas containing a crystal growth component such as GaAs, simultaneously with at least one of the crystal component gases. Thus, the crystal component gas and the reaction gas are chemically reacted at a low temperature on the substrate crystal, whereby a high-purity crystal can be obtained at a low temperature.

In a doping method of introducing a crystal component gas and a dopant compound gas in a predetermined order onto a substrate crystal heated in a vacuum, the reaction gas is added to the crystal component gas and the dopant gas in the doping method. The crystal is supplied simultaneously in synchronization with the introduction of the crystal component gas and chemically reacted at a low temperature, whereby a crystal whose impurities are strictly controlled at a low temperature can be obtained.

When a crystal component gas is alternately introduced onto a substrate heated in a vacuum, surface adsorption or crystallization accompanied by deposition and surface reaction occurs sequentially, and a semiconductor single crystal grows in monomolecular layers. For example, in the crystal growth of GaAs, the crystal component gas is TMG (trimethylgallium), TEG (triethylgallium), DMGaCl
(Dimethyl gallium chloride), DEGaCl (diethyl gallium chloride) or GaCl ₃ (gallium trichloride).

As As source gas, AsH ₃ (arsine), TMAs (trimethyl arsenic), TEAs (triethyl arsenic) or AsCl ₃ (arsenic trichloride) is used. Al
In the growth of GaAs, in addition to the above-mentioned source gases of Ga and As, Al
TMA (trimethylaluminum), T
EA (triethyl aluminum), TIBA (triisobutylaluminum), DMAlH (dimethylaluminum hydride), DEAlH (diethylaluminum hydride), DMAlCl (dimethylaluminum chloride), DEAlCl (diethyl aluminum chloride) or AlCl ₃ (aluminum trichloride) is used Can be

During the introduction of the above-mentioned source gases of Ga, As and Al,
By sending a reaction gas that chemically reacts with this, an alkyl group such as a methyl group or an ethyl group, or a functional group of a surface adsorbate such as Cl or H can be removed by a surface reaction. This can prevent contamination of C (carbon) from the alkyl group and mixing of Cl into the crystal. Further, by removing the H, atoms of the material as a raw material are exposed on the surface, and the next supplied raw material gas is efficiently adsorbed on the surface, so that strict control of monolayer growth can be achieved.

In the above-mentioned doping method in the GaAs or AlGaAs crystal growth method, a compound gas containing a dopant is also introduced for a predetermined time. That is, the crystal component gas and the compound gas of the dopant are introduced in a predetermined order. The compound gas of the dopant may be an n-type impurity compound such as DMSe (dimethyl selenium), DESe (diethyl selenium), DMS (dimethyl sulfur), DES (diethyl sulfur), DMTe (dimethyl tellurium), DETe (diethyl tellurium), etc. Group VI organic metals, H ₂ S (hydrogen sulfide), H ₂
Group VI hydrogen compounds such as Se (hydrogen selenide) and SiH ₄ ,
_{Si 2 H 6, Si 3 H} 8, Si (CH 3) there is a IV group compound, such as _4.

The compound of the p-type impurity is DM
Zn (dimethyl zinc), DEZn (diethyl zinc), DMCd
(Dimethyl cadmium), DECd (diethyl cadmium), Bi-CPMg (bis-cyclopentadienyl magnesium), GeH ₄ and C from methyl groups such as TMG
(Carbon).

In order to introduce these gases onto the substrate crystal and efficiently incorporate them into the crystal as donors and acceptors, after introducing these gases, the functional groups remaining on the crystal surface by bonding with the elements are removed. There is a need. For this reason, after the introduction of the dopant compound ,
By introducing a reaction gas at the same time as introducing one of them and removing a functional group by a surface reaction, doping of a pure element becomes possible. Further, since the doping is performed in the process of growing the molecular layers, the site of the crystal in which the dopant enters can be controlled, so that a highly doped crystal can be obtained.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the epitaxial crystal growth method of the present invention will be described below in detail with reference to the accompanying drawings, taking a semiconductor epitaxial crystal growth as an example. FIG. 1 is a time chart related to a doping method conventionally used in molecular layer epitaxy.
₃ ) shows an example of molecular layer epitaxy of GaAs.

That is, in a crystal growth method in which TEG and AsH ₃ are alternately introduced onto a substrate crystal at a predetermined pressure and for a predetermined time, respectively, a compound gas containing a dopant is mixed with the following gases (a) to (d). Select and install any one of the introduction modes. The mode (a) is for introducing a compound gas of a dopant in synchronization with the evacuation of AsH ₃ , and the mode (b) is for synchronizing the introduction of a compound gas of a dopant at the same time as introducing TEG. If the mode of (c) is that in synchronism with the time TEG exhaust introducing a compound gas of dopant mode (d) are in the case of introducing the compound gas simultaneously de <br/> Panto in synchronism with the time of introduction of AsH ₃ is there.

FIG. 2 shows an embodiment of epitaxial growth of a non-doped GaAs molecular layer according to the present invention.
As a crystal component gas, TEG or TMG is used as a Ga source gas, and AsH ₃ is used as an As source gas. In addition, H ₂ is used as a reaction gas that chemically reacts with them. These gases are introduced onto a substrate crystal heated in a vacuum by a gas introduction procedure as shown.

For example, when the organometallic gas of Ga is introduced onto the substrate crystal, the reaction gas H ₂ is introduced at the same time, so that the Ga- (C _{2
H 5) x (0 <x} ≦ 3) or Ga- (CH _{3) x} (0
Since C ₂ H ₅ and CH _{3 in} <x ≦ 3) react with and desorb from H ₂ , an epitaxial crystal growth film free of C (carbon) can be formed on the substrate crystal. Further, crystal growth at a low temperature can be realized.

As the source gas of Ga, DMGaCl, DE
There are GaCl and GaCl _3. By introducing the reaction gas H ₂ at the same time as introducing these gases, a high-purity GaAs crystal can be obtained at a low temperature in the same manner as described above. As a source gas for As, besides AsH ₃ , TM
When an organic metal gas such as As, TEAs, and AsCl ₃ or a chloride is used, a high-purity GaAs is formed by introducing a reaction gas H ₂ at the same time as introducing these gases. Crystals can be obtained by low-temperature growth.

Next, FIGS. 3 5 shows an example of a non-doped Al _x Ga _1-x As grown according to the present invention. The crystal component gas includes TEG or T as a Ga source gas.
MG is used, TIBA or TEA is used as an Al source gas, and AsH ₃ is used as an As source gas.

[0029] FIGS. 3-5 are both represent gas introduction procedure of Al _x Ga _1-x As growth. In each case, Ga
By introducing the reaction gas H ₂ at the same time as introducing the organometallic gas of Al and Al, high-purity Al _x Ga
_1-x As crystals can be obtained by low-temperature growth.

[0030] DMGaCl as a source gas in addition to Ga in the crystal component gas, using DEGaCl and GaCl _3, TMA as material gas Al, DMAlH, DEAlH, DMAlCl, DEAl
Similarly, when Cl and AlCl ₃ are used, a high-purity Al _x Ga _{1 -x} As crystal is grown at a low temperature by simultaneously introducing the reaction gas H ₂ while introducing these gases. Can be obtained at

Also, TMAs and TEAs are used as the source gas for As.
And when using an organic metal gas such as AsCl ₃ or a chloride, by introducing H ₂ which is a reaction gas at the same time as introducing these gases, high purity Al _x Ga _1-x
As crystals can be obtained by low-temperature growth.

Each of the examples shown in FIGS. 2 to 5 is a method for growing a crystal of GaAs and Al _x Ga _{1 -x} As.
P, InP, AlAs, InAs, InSb, In _x Ga _1-x As, Al _x Ga _1-x
The same method can be applied to the epitaxial growth of a molecular layer of P, InAs _y P _1-y or the like.

FIG. 6 shows an embodiment of a doping method in the molecular layer epitaxial crystal growth of GaAs according to the present invention. As shown in the figure, when a crystal component gas TEG or TMG and AsH ₃ are alternately introduced onto a substrate crystal heated in a vacuum to perform crystal growth, a compound gas of a dopant is converted to TEG (or TM).
In the doping method G), which is introduced synchronously with the evacuation (corresponding to the c mode in FIG. 1), the reaction gas is introduced in the following modes (c1) and (c2). The mode (c1) is when the reaction gas is introduced simultaneously in synchronization with the introduction of AsH ₃ , and the mode (c2) is in synchronization with the introduction of TEG or TMG.
This is a case where a reaction gas is introduced at the same time .

As the compound gas of the dopant, DMS, DES, DMSe, DESe, D
Group VI organometallic compounds such as MTe, DETe, H ₂ S and H
Group VI hydrides such as ₂ Se or _{SiH 4,, Si 2 H 6} , Si
_A group IV hydride such as ₃ H ₈ and a group IV organometallic compound such as Si (CH ₃ ) ₄ are used. Examples of the p-type dopant compound include DMCd, DECd, and Bi-CPMg.
A group II organometallic compound, a group IV hydride such as GeH _4, or a C (carbon) from a methyl group such as TMG is used.

Both the n-type and p-type dopant compounds are
They can be roughly classified into organometallic compounds and hydrides. Further, instead of H2 as a reaction gas, the above TE
A compound gas of a dopant of a different kind from the compound gas of the dopant introduced in synchronization with the exhaust of G (or TMG) may be introduced. For example, both (1) and (2) below correspond to the (c1) and (c2) modes shown in FIG. _{(1) {TEG-Si 2} H 6 - (DESe, AsH 3)} (2) {(TEG, DESe) -Si 2 H 6 -AsH 3}

The dopant compound gas introduced in synchronization with the exhaustion of the TEG (or TMG) is Si.
₂ H ₆ is used. The above (1) and (2) show the case where DESe which is a compound gas of a dopant is used as a reaction gas.

Further, FIG. 7 shows that in the doping method (corresponding to the mode A in FIG. 1) in which the compound gas of the dopant is introduced in synchronization with the evacuation of AsH ₃ , the reaction gases are represented by the following (a1) and (a2). ) Shows the case of introducing the mode. The mode (a1) is for introducing a reaction gas simultaneously with the introduction of AsH ₃ , and the mode (a2) is for introducing a reaction gas simultaneously with the introduction of TEG or TMG.

As the compound gas of the dopant, the above-mentioned Group VI organometallic compounds, Group VI hydrides, Group IV hydrides, Group IV organometallic compounds, Group II organometallic compounds and TMG are used. Further, instead of H ₂ as a reaction gas, the above AsH
A compound gas of a dopant of a different kind from the compound gas of the dopant to be introduced in synchronization with the evacuation in step ₃ may be introduced.

For example, the following (3), (4) and (5) correspond to the (a1) mode shown in FIG. _{(3) {TEG- (Si 2} H 6, AsH 3) -DESe} (4) {TEG- (H 2, AsH 3) -DESe} (5) {TEG- (H 2 Se, AsH 3) -DESe ＤＥ DESe is used as the dopant compound gas introduced in synchronization with the evacuation of AsH ₃ .

The above (3) is a case where Si ₂ H ₆ as a compound gas of a dopant is used as a reaction gas, (4) is a case where H ₂ is used as a reaction gas, and (5) is a compound gas of a dopant as a reaction gas. 3 shows the case where H ₂ Se was used. In the example of the above (5), since the organometallic compound of Se and the hydride of Se undergo a surface reaction, the doping density of Se can be increased to n ≧ 2 × 10 ¹⁹ cm ⁻³ at room temperature. .

In the above examples (3) and (4), the ethyl group of the adsorbed TEG reacts with the reaction gas Si ₂ H ₆ or H ₂ to be desorbed. Therefore, C in the crystal growth film
(Carbon) can be reduced. Further, since the dopant compound reacts with the reaction gas at a low temperature as in the example of (5), the crystal growth temperature can be lowered. Therefore, since the dopant is not redistributed, a high-purity grown film can be obtained.

The following Table 1 shows examples of combinations of the compound gas of the dopant and the reaction gas in the doping method in the GaAs molecular layer epitaxial crystal growth according to the present invention.

[0043]

[Table 1]

As described above, the doping method in the epitaxial crystal growth according to the present invention employs Al _x Ga in addition to GaAs.
_1-x As, GaP, InP, AlAs, InAs, InSb, In _x Ga _1-x A
The present invention is also applicable to molecular layer epitaxial crystal growth of s, Al _x Ga _1-x P, InAs _y P _{1-y, and the} like. As described above, the present invention is a technique extremely suitable for producing an active layer required for an LSI or an ultra-high-speed IC.

[0045]

As described above, the method for epitaxially growing a compound crystal according to the present invention provides a method for growing a single crystal by separately introducing a plurality of crystal component gases in a predetermined order onto a substrate crystal heated in a vacuum. In the epitaxial crystal growth of a compound crystal for growing a thin film, a high-purity crystal is obtained by simultaneously introducing a reaction gas onto the substrate crystal in addition to the crystal component gas in synchronization with the introduction of at least one of the crystal component gases. It can be obtained by low temperature growth. Further, the doping method in the epitaxial crystal growth of the compound crystal of the present invention is such that a reaction gas is simultaneously and synchronously introduced with the crystal component gas in addition to the crystal component gas and the dopant compound gas on the substrate crystal heated in vacuum. By introducing, it is possible to obtain a crystal whose impurities are strictly controlled by low-temperature growth,
Further, a crystal doped with a higher concentration of impurities can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing a time chart relating to a gas introduction method of a dopant compound gas in molecular layer epitaxy.

FIG. 2 Non-doping when H ₂ is used as a reaction gas
5 is a graph showing a gas introduction method in GaAs molecular layer epitaxy.

FIG. 3 Non-doping when H ₂ is used as a reaction gas
4 is a graph showing a first example of a gas introduction method in molecular layer epitaxy of Al _x Ga _1-x As.

FIG. 4 Non-doping when H ₂ is used as a reaction gas
9 is a graph showing a second example of a gas introduction method in molecular layer epitaxy of Al _x Ga _1-x As.

FIG. 5 Non-doping when H ₂ is used as a reaction gas
It is a graph showing a third example of the gas introduction method in molecular layer epitaxy Al _x Ga _1-x As.

FIG. 6 is a graph showing a C-mode doping method in GaAs molecular layer epitaxy.

FIG. 7 is a graph showing a doping method using A mode in GaAs molecular layer epitaxy.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-116120 (JP, A) JP-A-63-181314 (JP, A) JP-A-61-34928 (JP, A)

Claims (6)

(57) [Claims] In a method for epitaxially growing a compound crystal, a plurality of crystal component gases of a compound are introduced into a substrate crystal heated in a vacuum in a predetermined order to grow a single crystal. Functional groups on the surface adsorbate
A method for epitaxially growing a compound crystal, wherein the reaction gas to be removed is introduced simultaneously with at least one of the plurality of crystal component gases. 2. A doping method in the epitaxial growth of a compound crystal, in which a compound crystal component gas and a dopant compound gas are introduced into a substrate crystal heated in a vacuum in a predetermined order to grow a single crystal. the introduction of one crystal component gases of the crystal component gases and
At the same time , it reacts chemically with the crystal component gas to form surface adsorbate.
The above doping method, wherein a reactive gas for removing a functional group is introduced. 3. A dopan wherein the reaction gas is different from a compound gas of a dopant previously introduced on the substrate crystal.
Characterized in that a preparative compounds gases different types of the organometallic compound or hydride of <br/> dopant, doping method in epitaxial growth of a compound crystal according to claim 2. 4. The method according to claim 1 , wherein said reactant gas precedes said substrate crystal.
Dopant same as the compound gas of the dopant introduced
Different types of organometallic compounds or hydrides
-A compound gas of punt
2. In the epitaxial growth of the compound crystal described in 2,
Grouping method. 5. The doping method in the epitaxial growth of a compound crystal according to claim 2, wherein the crystal component gas contains a group III element and a group V element. 6. The method according to claim 6, wherein the compound gas of the dopant is Si, Ge,
6. The doping method in the epitaxial growth of a compound crystal according to claim 2, wherein the compound gas is a compound gas of S, Se, Te, Zn, Cd, and Mg.