JP2005085850A - Vapor phase epitaxial growth apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniform a substrate temperature during the growing of an epitaxial layer in the surface of the substrate in a vapor phase epitaxial growth system. <P>SOLUTION: A plurality of substrates 4 are arranged in a turning plate-like susceptor 3 in its circumferential direction and it is held in a manner that their growing planes may face the side of a gas passage, and a soaking plate 7 is overlaid on the rear side of the substrate. A material gas is applied in the direction of diameter of the susceptor 3, and the susceptor 3 is heated together with the substrate 4 by a heating means 21 from the opposite side to the gas passage, so that a semiconductor crystal is epitaxially grown on the heated substrate 4 by an organic metal vapor phase growth method. In such a vapor phase epitaxial growth apparatus, the soaking plate 7 is made smaller in thickness toward the outside of the susceptor 3 in its radial direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vapor phase epitaxial growth apparatus suitable for making the substrate temperature uniform during the epitaxial layer growth of a group III-V compound semiconductor crystal in a plane.

  Group III-V compound semiconductors such as GaAs (gallium arsenide) and InGaAs (indium gallium arsenide) have a feature of higher electron mobility than Si (silicon) semiconductors. Taking advantage of this feature, it is often used in devices that require high-speed and high-efficiency operation, light-emitting devices, and the like. Typical examples include HEMT (High Electron Mobility Transistor), LED (Light Emitting Diode), LD (Laser Diode) and the like.

  As an example, FIG. 2 shows the basic structure of an LD. The LD is composed of a cap layer, a p-cladding layer, a light-emitting layer, an n-cladding layer, and a buffer layer, which are grown on the substrate and from the top. The cap layer is a layer for forming an electrode. The p-cladding layer is doped with a p-type dopant and the n-cladding layer is doped with an n-type dopant, and the generated carriers are supplied to the light emitting layer and recombined to emit light. The buffer layer has a function of preventing deterioration of device characteristics due to residual impurities on the substrate surface. The substrate is a base for single crystal growth.

表１に示したＬＤエピタキシャルウエハの成長方法を以下に述べる。 Table 1 shows an example of LD structure. Crystal growth is called epitaxial. The epitaxial layer names n- and p- indicate that the epitaxial layer is n-type and p-type, respectively, and un- indicates that the epitaxial layer is undoped. The unit of thickness is nm (10 ^-9 m). The unit of carrier concentration is cm ⁻³ .

The growth method of the LD epitaxial wafer shown in Table 1 will be described below.

  The compound semiconductor crystal of the LD is generally grown by a vapor phase epitaxial growth apparatus using a metal organic vapor phase epitaxy (hereinafter referred to as MOVPE method). In the MOVPE method, a group III organometallic source gas and a group V source gas are introduced into a reaction furnace as a mixed gas with a high-purity hydrogen carrier gas, and the source material is pyrolyzed near the substrate heated in the reaction furnace. A compound semiconductor crystal grows epitaxially on the substrate.

  Here, FIG. 3 shows a configuration of a reactor (reactor) employed by a conventional MOVPE apparatus (vapor phase epitaxial growth apparatus). This is because a plate-shaped susceptor 3 is provided on the upper wall of the reaction tube 2 through which the source gas flows from the source gas supply port 2a to the gas exhaust port 2b, and is configured to be rotatable by a motor 10, and An opening 5 is formed in substantially the same shape as the semiconductor substrate 4 that is the target of vapor phase epitaxial growth, and the surface of the substrate 4 is housed downward and the lower surface is exposed in the opening 5 as shown in FIGS. And an epitaxial growth apparatus in which a soaking plate 7 is fitted in the opening 5 facing the main heater 21 as a heating source for heating the substrate 4. In addition, 9 is a magnetic shield unit and 22 is an outer periphery heater.

  The substrate 4 on which the epitaxial layer is grown is set on the susceptor 3 and heated in a growth furnace. When the source gas is supplied into the growth furnace, the source gas is decomposed by heat, and an epitaxial layer is grown on the substrate.

For example, when growing un-GaAs, Ga source material Ga (CH ₃ ) ₃ (trimethylgallium) and As source material AsH ₃ (arsine) are supplied to the substrate. In addition, there is Ga (CH ₃ CH ₂ ) ₃ (triethylgallium) as another Ga raw material. Other As raw materials include As (CH ₃ ) ₃ (trimethylarsenic) and TBA (tertiary butylarsine).

When growing un-Al _0.5 Ga _0.5 As, Ga (CH ₃ ) ₃ , AsH ₃ , and Al source material Al (CH ₃ ) ₃ (trimethylaluminum) are supplied to the substrate. In addition, there is Al (CH ₃ CH ₂ ) ₃ (triethylaluminum) as an Al raw material.

When growing n-GaAs, Ga (CH ₃ ) ₃ , AsH ₃ and n-type dopant are supplied to the substrate. Examples of the n-type dopant element include Si and Se (selenium). Si raw materials include SiH ₄ (monosilane) and Si ₂ H ₆ (disilane). Se raw material includes H ₂ Se (hydrogen selenide).

  Here, as an example, consider a case where two substrates 4 are set on the susceptor 3 as shown in FIG. 4 and an epitaxial layer is grown on the substrate 4. FIG. 5 shows an example of a conventional technique for growing an epitaxial layer by setting the crystal growth surface of the substrate 4 parallel to the flow direction of the source gas. The substrate 4 was set on the susceptor 3, and a plate called a soaking plate 7 was placed thereon to grow. Normally, the thickness of the soaking plate 7 is not changed in the radial direction of the susceptor 3, that is, the epitaxial layer is grown using a uniform thickness.

  As a vapor phase epitaxial growth apparatus using a soaking plate with a non-uniform thickness, for example, a structure using a soaking plate having a slope that increases in thickness from the center of the susceptor toward the outside is known. (For example, refer to Patent Document 1).

In the technique of Patent Document 1, in view of the problem that when n-type GaAs or AlGaAs is grown, the carrier concentration of the epitaxial layer gradually increases from the center direction of the susceptor 3 toward the peripheral direction. It is an object to improve the in-plane uniformity of the carrier concentration in the epitaxial layer by positioning the thicker one on the center side of the susceptor and positioning the thicker side on the peripheral side of the susceptor.
JP-A-10-007490

  However, as the substrate area handled increases, the in-plane uniformity of the substrate temperature during epitaxial layer growth has become an important issue.

  That is, when grown by a vapor phase epitaxial growth apparatus using a soaking plate having a uniform thickness of the prior art (FIG. 5), as shown in FIG. 6, there is a distribution in which the temperature decreases at the outer periphery as seen by the diameter of the susceptor. For this reason, even in each substrate 4, a large temperature difference has occurred within the substrate surface. The reason why the temperature is high on the inner peripheral side of the susceptor 3 is that the heating efficiency is high because it is directly under the heater. On the other hand, on the outer peripheral side of the susceptor 3, the influence of heat radiation due to rotation is large, so the temperature becomes low. As a result, the carrier concentration, the film thickness, the composition, the lattice matching degree, etc., which are the characteristics of the epitaxial layer to be grown, inevitably have a distribution in the plane.

  Accordingly, an object of the present invention is to provide a vapor phase epitaxial growth apparatus that solves the above-described problems and makes the substrate temperature during epitaxial layer growth uniform within the substrate surface.

  In order to achieve the above object, the present invention is configured as follows.

  In the vapor phase epitaxial growth apparatus according to the first aspect of the present invention, a plurality of substrates are arranged in a circumferential direction on a rotating plate-shaped susceptor, and a growth surface is supported toward the gas flow path side. Overlaying a soaking plate, flowing source gas in the diameter direction of the susceptor, heating the susceptor together with the substrate from the opposite side of the gas flow path by heating means, and the semiconductor crystal is grown on the heated substrate by metal organic vapor phase epitaxy In the vapor phase epitaxial growth apparatus for epitaxial growth, the thickness of the soaking plate is changed so that the thickness decreases toward the outside in the radial direction of the susceptor.

  According to a second aspect of the present invention, in the vapor phase epitaxial growth apparatus according to the first aspect, the surface on the gas flow path side of the soaking plate is a flat surface, and the surface on the heating means side is thinner from the center of the susceptor toward the outer peripheral side. It is characterized by being formed by an inclined surface having a predetermined inclination angle θ.

The invention according to claim 3 is the vapor phase epitaxial growth apparatus according to claim 1 or 2, wherein the vapor phase epitaxial growth apparatus is an apparatus for growing a group III-V compound semiconductor crystal by a metal organic vapor phase growth method. AsH ₃ (arsine), As (CH ₃ ) ₃ (trimethyl arsenic), TBA (tertiary butyl arsine), PH ₃ (phosphine), or TBP (tertiary butyl phosphine), CH ₃ ) ₃ (trimethylaluminum), Ga (CH ₃ ) ₃ (trimethylgallium), In (CH ₃ ) ₃ (trimethylindium), Al (CH ₃ CH ₂ ) ₃ (triethylaluminum), Ga (CH ₃ CH ₂ ) ₃ (triethyl gallium), using an In (CH ₃ CH _{2) 3} (triethyl indium), a diluent gas , H ₂ (hydrogen), using N ₂ (nitrogen) or Ar (argon), characterized in that.

  In the present invention, the thickness of the soaking plate is changed in the radial direction of the susceptor. That is, the thickness of the soaking plate is configured so that the thickness decreases from the center of the susceptor toward the outside, and specifically, the soaking plate having such an inclination is configured. For example, the following excellent effects can be obtained.

  (1) The substrate temperature during epitaxial layer growth can be made uniform in the substrate plane.

  (2) An epitaxial layer with high in-plane carrier concentration is obtained.

  (3) An epitaxial layer with high in-plane film thickness uniformity can be obtained.

  (4) An epitaxial layer with high in-plane uniformity of composition can be obtained.

  (5) An epitaxial layer with high in-plane uniformity of lattice matching can be obtained.

  (6) In-plane uniformity of the substrate temperature can be achieved by a very easy means.

  (7) In-plane uniformity of the substrate temperature can be achieved by extremely low cost means.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  The premise compound vapor phase epitaxial growth apparatus 1 is the same as that shown in FIG. 3 except for the configuration in which the thickness of the soaking plate 7 is changed (inclined surface). That is, the compound semiconductor vapor phase epitaxial growth apparatus 1 according to the present embodiment is provided with a disk-shaped susceptor 3 on the upper wall of the reaction tube 2 through which the source gas flows from the source gas supply port 2a to the gas exhaust port 2b. Is configured to be rotatable by the motor 10. An opening 5 is formed in the susceptor 3 in substantially the same shape as that of the semiconductor substrate 4 to be subjected to vapor phase epitaxial growth. The surface of the substrate 4 is accommodated downward in the opening 5 and the lower surface is exposed. To do. A soaking plate 7 is fitted into the opening 5 so as to face the main heater 21 as a heating source for heating the substrate 4 and is stacked on the back side of the substrate. In addition, 9 is a magnetic shield unit and 22 is an outer periphery heater.

  However, unlike the prior art, in the present invention, the thickness of the soaking plate 7 is changed so that the thickness decreases toward the outside in the radial direction of the susceptor. In this embodiment, as shown as an inclined surface 7 a in FIG. 1, each soaking plate 7 is inclined so that the thickness of the soaking plate becomes thinner from the inner periphery 3 a to the outer periphery 3 b of the susceptor 3. Wearing. Therefore, the inclined surface 7a of the soaking plate 7 is inclined by a predetermined inclination angle θ with respect to a horizontal plane parallel to the flow direction of the source gas. In other words, the heat equalizing plate 7 includes an inclined surface having a predetermined inclination angle θ bulging toward the center of the susceptor 3 as an upper surface thereof.

  By doing so, the temperature on the inner peripheral side of the susceptor 3 that has been conventionally high is less affected by the heating by the heaters 21 and 22, and the temperature is lowered. The temperature rises because the heat from the heat is easily transmitted. As a result, the in-plane temperature distribution of each substrate 4 can be made extremely uniform as can be seen from FIG. In order to confirm this effect, an LD was prototyped as an example as follows.

  The present invention was applied to the growth of the LD epitaxial wafer shown in Table 1.

The substrate temperature during growth is 700 ° C., the growth furnace pressure is 70 Torr, and the dilution gas is hydrogen. A GaAs substrate was used as the substrate. The growth of the un-Al _0.1 Ga _0.9 As layer with a _{Ga (CH 3) 3, Al} (CH 3) 3 and AsH ^_3, 65cm ₃ / min their flow rates respectively, 45cm ³ / min and 1000 cm ³ / min It is. For the growth of the n-Al _0.5 Ga _0.5 As layer, Si ₂ H ₆ is used in addition to Ga (CH ₃ ) ₃ , Al (CH ₃ ) ₃ and AsH ₃ used for the growth of un-Al _0.1 Ga _0.9 As. did. The flow rates are 65 cm ³ / min, 150 cm ³ / min, 1000 cm ³ / min and 300 cm ³ / min, respectively. Ga (CH ₃ ) ₃ , AsH ₃ and Si ₂ H ₆ are used for the growth of the n-GaAs layer, and their flow rates are 100 cm ³ / min, 300 cm ³ / min and 200 cm ³ / min, respectively.

  The thickness of the soaking plate 7 was set so that the inclined surface 7a on the upper surface was inclined 10 ° with respect to the horizontal direction (inclination angle θ = 10 °). The susceptor was rotated at 30 rpm to carry out epitaxial growth.

表２に、本実施例（図１）における基板面内の温度差を、従来方法（図５）と比較して示す。

Table 2 shows the temperature difference within the substrate surface in this example (FIG. 1) in comparison with the conventional method (FIG. 5).

  In the case of the present embodiment (soaking plate having an inclination angle θ = 10 °), the temperature difference in the substrate surface is as large as 10.0 ° C. in the case of the conventional technique (soaking plate with uniform thickness). The temperature difference in the substrate surface is 1.0 ° C., which is a value that is an order of magnitude smaller. From this, it can be seen that according to the present invention, an epitaxial layer having a very high in-plane uniformity of film thickness can be obtained.

  As described above, according to the present invention, it is understood that extremely high in-plane temperature uniformity of the substrate can be achieved during the growth of the epitaxial layer.

  Here, when examining the optimum condition of the substrate inclination angle θ, when applying the present invention, it is necessary to set the inclination angle of the soaking plate thickness so as to cancel out the substrate temperature distribution in the prior art. . In other words, when the temperature difference in the substrate surface is large, the inclination angle of the soaking plate thickness is also increased, and conversely, when the temperature difference in the substrate surface is small, the inclination angle of the soaking plate thickness is also decreased. To do.

  Further, the thickness change of the soaking plate does not necessarily have to be linearly changed, and any geometric shape such as a curved line or a step shape may be adopted.

  The preferred embodiments of the present invention have been described above. The present invention is not limited to the so-called “face-down” method in which the substrate is disposed so that the crystal growth surface faces downward as described above. The present invention can also be applied to a so-called “face-up” method in which the substrate is arranged so as to face upward.

It is a figure which shows the set state of the board | substrate and the soaking | uniform-heating board with respect to the susceptor of the vapor phase epitaxial growth apparatus which concerns on the Example of this invention, (a) is sectional drawing by the side of a susceptor, (b) is the temperature distribution of the diameter direction of the susceptor. FIG. It is explanatory drawing which shows the basic structure of LD. It is sectional drawing which showed the structure of the vapor phase epitaxial growth apparatus in a prior art. It is a figure which shows the board | substrate setting method to a susceptor in a prior art. It is a figure which shows the set state of the board | substrate and heat equalization board in a prior art. It is a figure for demonstrating the in-plane nonuniformity of the substrate temperature which is a problem of a prior art, (a) is sectional drawing by the side of a susceptor, (b) is the figure which showed temperature distribution of the diameter direction of the susceptor. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vapor phase epitaxial growth apparatus 2 Reaction tube 3 Susceptor 3a Inner circumference 3b Outer circumference 4 Substrate 5 Opening 7 Heat equalizing plate 7a Inclined surface 21 Main heater 22 Outer circumference heater θ Inclination angle

Claims (3)

A rotating plate-shaped susceptor is provided with a plurality of substrates arranged in the circumferential direction, and the growth surface is supported toward the gas flow path side, and a heat equalizing plate is provided on the back side of the substrate, in the susceptor diameter direction. In a vapor phase epitaxial growth apparatus for flowing a source gas, heating a susceptor together with a substrate from the opposite side of the gas flow path by a heating means, and epitaxially growing a semiconductor crystal on the heated substrate by metal organic chemical vapor deposition.
A vapor phase epitaxial growth apparatus characterized in that the thickness of the soaking plate is changed so that the thickness decreases toward the outside in the radial direction of the susceptor. The vapor phase epitaxial growth apparatus according to claim 1,
The surface of the heat equalizing plate on the gas flow path side is a flat surface, and the surface on the heating means side is formed by an inclined surface having a predetermined inclination angle θ that becomes thinner from the center of the susceptor toward the outer peripheral side. Phase epitaxial growth equipment. In the vapor phase epitaxial growth apparatus according to claim 1 or 2,
The vapor phase epitaxial growth apparatus is an apparatus for growing a III-V group compound semiconductor crystal by a metal organic vapor phase growth method,
As a group V raw material, AsH ₃ (arsine), As (CH ₃ ) ₃ (trimethylarsenic), TBA (tertiary butyl arsine), PH ₃ (phosphine) or TBP (tertiary butyl phosphine) are used.
As Group III raw materials, Al (CH ₃ ) ₃ (trimethylaluminum), Ga (CH ₃ ) ₃ (trimethylgallium), In (CH ₃ ) ₃ (trimethylindium), Al (CH ₃ CH ₂ ) ₃ (triethylaluminum) , Ga (CH ₃ CH ₂ ) ₃ (triethylgallium), In (CH ₃ CH ₂ ) ₃ (triethylindium),
A vapor phase epitaxial growth apparatus using H ₂ (hydrogen), N ₂ (nitrogen) or Ar (argon) as a gas for dilution.

Images