JPS6217097A - Liquid phase epitaxial growth method - Google Patents

Abstract

PURPOSE:To make the meltback amount accurate only by specifying the temp. higher than the meltback temp. and to enable the formation of a specular surface-like epitaxial layer by distributing a saturated soln. for meltback wherein an excessive solute is removed in the meltback temp. to the inside of a soln. reservoir for the distribution. CONSTITUTION:A solvent and an excessive solute are introduced to the inside of a soln. reservoir 12 for meltback. Then after dissolving the solute in the solvent incorporated in the reservoir 12 up to the saturation at midway meltback temp T1 in the rise in temp. by rising the temp. of a furnace, a saturated soln. 17 for meltback wherein the excessive solute content is removed is distributed to the inside of a soln. reservoir 14 for the distribution. Then, it is risen in temp. up to the growth temp. T2 higher than the meltback temp. T1 to make the soln. 17 an unsaturated state and thereafter both the slow cooling and the temp. drop are started from the growth temp. T2 and the soln. 17 reached to a prescribed degree of saturation -DELTAT2 is brought into contact with a substrate 19 for the prescribed time T1 to subject the surface of the substrate to the meltback. Thereafter, a soln. 18 for the growth being in a supercooled state is brought into contact with the substrate 19 to grow an epitaxial layer on the substrate 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid phase epitaxial growth method using a slide boat method, and particularly to improvement of meltback of a substrate surface performed prior to epitaxial growth.

[Prior Art] Among the substrates for epitaxial growth, semi-insulating substrates and mixed crystal substrates are difficult to epitaxially grow directly on the substrate surface.

This is because in the case of a semi-insulating substrate, the substrate becomes high temperature before epitaxial growth, causing thermal deterioration of the surface and lowering the specific resistance. In addition, in the case of a highly oxidizing mixed crystal substrate such as GaAfAs, the surface oxidizes just by exposing it to air, so if you continue to epitaxially grow it, it will grow into islands, making it difficult to obtain a clean epitaxial surface. That's because there isn't.

Therefore, the Meld Pack method was devised to eliminate these drawbacks. That is, as shown in FIG. 4, by sliding the substrate 1 together with the slider 2, the melt-back solution 5 in the melt-back solution reservoir 4 formed in the solution storage section 3 is poured.
A slide boat device configured to be brought into contact with the growth solution 7 in the growth solution reservoir 6 in advance is inserted into the furnace and used.

In the order of operation, first, the temperature inside the furnace is raised to the growth temperature in the state shown in FIG. Next, as shown in FIG. 5, slow cooling is started between R and the substrate 1 is slid at time 1 to remove the unsaturated melt-back solution 5 in which the solute is not sufficiently dissolved in the solvent and time j.
The surface layer of the substrate is melted and removed. At time j when the meltback ends, the substrate 1 is again slid and moved under the growth solution 7 to start growing the epitaxial layer. Then, at time k, the substrate 1 is slid to end the growth.

In order to obtain an unsaturated solution for dissolving and removing the substrate surface layer, the amount of solute was rigorously weighed to be insufficient to saturate the solvent at the growth temperature.

[Problems to be solved by the invention] However, it is difficult to strictly weigh the solute relative to the solvent in the above-mentioned melt-back method, and strict temperature control is also required, so it is difficult to accurately control the degree of unsaturation. I couldn't. For this reason, there is no reproducibility in the amount of meltback, and non-uniform meltback occurs, making it difficult to obtain a mirror-like epitaxial layer with good reproducibility.

[Object of the Invention] An object of the present invention is to solve the above-mentioned conventional problems and to provide a liquid phase epitaxial growth method in which meltback performed before epitaxial growth can be easily performed with good controllability.

[Summary of the Invention] The present invention, which achieves the above object, involves distributing a melt bulk solution at a temperature lower than the cooling start temperature in order to prepare an unsaturated melt bag solution in a slide boat method using a distribution method. It has characteristics.

This will be explained based on FIGS. 1 and 2 corresponding to the actual tM@.

First, a solvent and an excessive amount of solute are put into the melt-back solution reservoir 12. Here, "too much" means that the melt-back solution 17 becomes sufficiently cloudy to become a saturated solution at the melt-back temperature described later.

Next, the temperature of the furnace is started to rise, and when it reaches the meltback temperature T1 in the middle of heating, this temperature is maintained and the solute is dissolved in the solvent in the meltback solution reservoir 12 until it is saturated. )) Thereafter, the saturated melt-back solution 17 from which the excess solute released from the solvent has been removed is distributed into the distribution solution reservoir 14 (FIG. 1(b)).

After this distribution, the temperature is further increased to a growth temperature T2 higher than the meltback temperature Ts to bring the meltback solution 17 into an unsaturated state as shown in FIG. 1(C).

(d)), then gradually cooled down from the growth temperature T2,
The melt-back solution 17 has a predetermined degree of unsaturation (-ΔT2
), the 3% plate 19 is brought into contact with this for a predetermined time tt to melt back the substrate surface.

After that, the growth solution 18 and the substrate 19 are in a supercooled state.
By contacting the epitaxial layer with the substrate 19
grow up.

Therefore, by determining the degree of unsaturation -ΔT2 of the melt-back solution and the contact time t1, it becomes possible to control the melt-back optimally. In this case, in this step, unlike the conventional method in which the melt-back solution maintains a saturated state even if the temperature rises as long as there is free solute, the melt-back solution is moved from the melt-back solution reservoir 12 to the distribution solution reservoir 14. Meltback solution 17 saturated under meltback temperature Ti
By once transferring the solution and cutting off the supply of new solute, the meltback solution 17 becomes unsaturated when the meltback 'IA a T t is exceeded.
Since it is sufficient to initially add solute in excess of the solvent, there is no need to weigh the solvent and solute with high precision, nor to accurately control the absolute value of temperature.

The present invention is applicable to all types of liquid phase epitaxial growth that require melting back of the substrate surface before epitaxial growth, such as semi-insulating substrates and strongly oxidized mixed crystal substrates such as GaAβAS.

[Example] An example of the present invention will be described below based on FIGS. 1 to 3.

Figure 1 shows slide boat equipment @1 for carrying out the present invention.
0 process diagram is shown. In the figure, 11 is a growth solution holder having a meltback solution reservoir 12 and a growth solution reservoir 13, and is slidably provided on a distribution solution holder 16 having two distribution solution reservoirs 14 and 15. . Normally, by sliding the growth solution holder 11, distribution to the distribution solution reservoirs 14 and 15 can be performed at once, but each meltback in the meltback solution reservoir 12 and the growth solution reservoir 13 can be distributed at once. The growth solution 17 and the growth solution 18 can be separately distributed to distribution solution reservoirs 14 and 15 according to the slide calendar.

A slider 20 for holding one substrate is provided at the bottom of the dispensing solution holder 15, and the slider 20 is connected to the board 1-1.
21 so that each meltback solution 1 in the dispensing solution reservoir 14.
7. The slide boat device 10 is configured to sequentially bring the growth solution 18 into contact with the substrate 19.

Now, the work order in the above configuration will be explained. Here, we introduce GaAS on a GaAS semi-insulating substrate.
This will be explained using epitaxial growth as an example.

First, the substrate 19 is set on the slider 20, and Qa as a solvent and Qa As polycrystal as a solute are placed in both the melt-back solution reservoir 12 and the growth solution reservoir 13. Q
The amount of Qa As polycrystals relative to a should be sufficiently excessive to become a saturated solution at the growth temperature described below, that is, the amount should be greater than the saturated amount. Since it is more than the saturation amount, for weighing,
It doesn't require that much precision. Then, the slide boat device 10 is inserted into a reactor (not shown) in the state shown in FIG. 1(a).

Next, as shown in FIG. 2, the furnace into which the slide boat device 10 was inserted is heated to a melt-back temperature T! The temperature was maintained from time a to b, and the raw material Ga AS was
Dissolve in solution a until saturated (Figure 1(a)). Qa
Since AS is added in excess, undissolved free GaA
Although S is present, this free Qa As accumulates in the upper layer of the generated melt-back solution 17 and growth solution 18, and no free Qa As exists in the lower layer.

When the Qa AS is dissolved in the Qa solution until it is saturated, slide the growth solution holder 11 and add the meltback solution 1.
7 is dropped into the first distribution solution reservoir 14 and distributed (FIG. 1(b)). Since the distribution to the first distribution solution reservoir 14 is performed on the lower layer of the meltback solution 17, the free excess Qa A is transferred to the distribution solution reservoir 14.
A saturated solution from which the S content has been removed will be contained.

In this way, a sufficient amount of saturated melt-back solution 17
After entering the distribution solution reservoir 14, the growth solution holder 11 is further slid to cut off the communication between the meltback solution reservoir 12 and the first distribution solution reservoir 12, while the growth solution reservoir 13 and The growth solution 18 is distributed by communicating with the second distribution solution reservoir 15 (FIG. 1(C)).

In this state, the temperature of the furnace is raised from the meltback temperature Tl to the growth temperature 2, and this growth temperature is maintained from time C to d. By maintaining the growth temperature T2, the growth solution 18 in the second distribution solution reservoir 15 becomes M-GaAs
This results in a saturated solution with no .

Moreover, at this time, the melt-back solution 17 trapped in the first distribution solution reservoir 14 is added to the Qa to be newly dissolved.
Since the supply of As is cut off, the temperature becomes unsaturated at T2-Tt. At this point, slide the growth solution holder 11 further to remove the melt-back solution 17 and the growth solution 1.
The distribution operation of step 8 is completed (FIG. 1(d)).

Then, at time d after the completion of these distribution operations, the growth temperature T
2 is gradually cooled down. This gradual cooling is performed with a predetermined gentle temperature gradient. Meltback temperature T lower than growth temperature T2
At a time e when the temperature reaches a predetermined temperature higher than 1, the slider 20
slide to bring the melt pack solution 17 into contact with one substrate. At this time, the melt-back solution 17 is - ΔT
2 = Tr - T3 is definitely in the unsaturated state.

The slider 20 is slid again at a time f when the growth solution 18 in the second distribution solution reservoir 15 is supercooled by ΔT1 while the surface metamorphic layer of the substrate is removed by melting back for a time t1. Then, the substrate 19 from which the metamorphic layer on the surface has been removed is brought into contact with the growth solution 18. This contact is maintained for a time t2 from time f to g to grow an epitaxy cell layer on one substrate.

Here, the meltback amount is determined by the degree of unsaturation -ΔT2 of the meltback solution and the contact time [L, and its accuracy can be controlled to ±10%.

In order to perform meltback to a mirror state under the condition that the cooling start temperature is 800°C or around 800°C, -ΔT2 must be 2.
~15℃ or less is suitable, while the meltback time t
1 is suitable for obtaining a surface for about 1 to 30 seconds, although it depends on the thickness of the metamorphic layer. Since the amount of meltback can be precisely controlled, the minimum amount of meltback solution is required to remove the metamorphic layer.

FIG. 3 shows a modification of the embodiment shown in FIG. 1. The difference from FIG. 1 is that the growth solution holder 11a is only provided with a melt-back solution reservoir 12a, and the distribution solution holder 16
The melt-back solution 17 is placed in the first distribution solution reservoir 14 of
Although the second distribution solution reservoir 15 is filled with the growth solution 18 from the beginning and the distribution operation is not performed, even with this method, the meltback on the substrate surface is uniform. It will be held in

In the above embodiment, the case where one layer is grown after meltback is described, but it is also possible to grow multiple layers after meltback. In addition, when melting back a mixed crystal substrate such as GaAρAs instead of a QaAs semi-insulating substrate, Ga and QaAS are used as a meltback solution.
In addition to polycrystals, Aβ may be added.

[Effects of the Invention 1 As described above, the present invention exhibits the following excellent effects.

(1) By distributing the saturated melt-back solution from which excess solute has been removed under the melt-back temperature into the distribution solution reservoir, the substrate Since the degree of unsaturation of the melt-back solution brought into contact with the melt-back solution can be controlled with high accuracy, the amount of melt-back determined from the degree of unsaturation of the melt-back solution and the contact time can be made accurate. Therefore, the reproducibility of meltback (3) is extremely good, the substrate surface can be uniformly melted back, and a mirror-like epitaxial layer can be obtained with good reproducibility.

(2) Since it is only necessary to add a slightly excessive amount of solute to the solute, there is no need for highly accurate weighing of the solvent and solute as in the past, making the work extremely easy.

[Brief explanation of drawings]

Fig. 1 is a process diagram of one embodiment of the present invention, Fig. 2 is a diagram showing a temperature program in the process of Fig. 1, and Fig. 3 is a diagram showing the temperature program in the process of Fig. 1.
4 is a sectional view of a conventional liquid phase epitaxial growth apparatus, and FIG. 5 is a temperature program for carrying out the process using the apparatus of FIG. 4. In the figure, 12 is a melt-back solution reservoir, 14 is a distribution solution reservoir, 17 is a melt-back solution, 18 is a growth solution, 19 is a substrate, T1 is a melt-back temperature, T2 is a growth temperature, and ΔT2 is a predetermined value. The degree of unsaturation, tl, is a predetermined time. Patent Applicant Hitachi Cable Co., Ltd. Representative Patent Attorney Nobuo Kinuya Drawing Invitation
(No change in content) 12: Nortonoko-7) Nininfme T1: Mel F High 77 (Shishi 14: Reisai Jun Hakama Anchor) T
21 versus i practice level 17: Melt j ~ 7 condolence -ΔT2
Nia 'r6Lq old skin: Bacho's story t de ghost I group interval 19: Act 1 - Figure 1 Figure 3 Figure 5 Procedure ne...correct writing method) % expression % 1, Incident display Tokugansho 60-152340 No. 2,
Title of the invention: Liquid phase epitaxial growth method 3, relationship with the person making the amendment Patent applicant (512) Hitachi Cable Co., Ltd. 4, agent postal code: 105 Atagoyama Lawyer Building 5, 1-6-7 Atago, Minato-ku, Tokyo , Date of amendment order: October 29, 1985 (shipment date) 6. Drawings subject to amendment 7. Contents of amendment (1) Submit drawings prepared using II ink as shown in the attached sheet. (However, the contents remain unchanged) 8. List of attached documents

Claims (1)

[Claims] In the liquid-phase epitaxial growth method using the slide boat method, in which the epitaxial layer is grown on the substrate after melting back the substrate surface, a solvent and an excessive amount of solute are placed in the melt-back solution reservoir, and the melt-back process is performed during heating. After dissolving the solute in the solvent to saturation at a temperature, the saturated melt-back solution, excluding the excess solute free from the solvent, is distributed into a distribution reservoir, and then the growth rate is greater than the melt-back temperature. The temperature is raised to a certain temperature to make the meltback solution unsaturated, and then the temperature is gradually cooled down from the growth temperature, and the substrate is brought into contact with the meltback solution for a predetermined period of time after reaching a predetermined degree of unsaturation. A liquid phase epitaxial growth method characterized by growing an epitaxial layer on a substrate by melting back the substrate and then bringing the substrate into contact with a supercooled growth solution.