JP2599767B2 - Solution growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a solution growth apparatus, and more particularly to a solution growth apparatus for compound semiconductor crystals, which aims at growing a compound semiconductor crystal having a uniform composition at a high growth rate and without surface defects. [1] a lower support 1, an upper support 2 having an upper cutout 21 opening downward and an upper opening 22 serving as a solution reservoir for disposing a substrate, and a slider opening serving as a solution reservoir. A solution growth apparatus comprising: a lower support 31; and a slider 3 which slides in contact with the upper support. 31. A growth substrate 5 having a horizontal growth surface disposed on the upper cutout. Dummy substrates 61 through with the growth surface inclined from the horizontal at the slider opening
A solution growing apparatus in which the 64 is disposed, and [2] a slider 3
The solution growing apparatus according to [1], wherein a spacer 7 for forming a space between the substrate and the growth substrate 5 is disposed in the upper cutout 21, and the opening on [3] allows the growth surface of the growth substrate 5 to be horizontal. The lower opening has a shape that allows the growth surface to be horizontal and does not allow the growth surface to pass therethrough as the upper cut-out portion 21; The solution growing apparatus according to [1] is provided with an upper cutout portion 21 having a substrate disposing concave portion 211 and a substrate suction opening portion 212 extending from the bottom of the concave portion to the upper surface of the upper support 2.

[Industrial applications]

The present invention relates to a solution growth apparatus, and more particularly to a solution growth apparatus for compound semiconductor crystals.

Compound semiconductors such as GaAs, InP, and InGaAs have many functions that cannot be obtained with elemental semiconductors such as silicon, such as a light emitting function and an oscillation function, and are expected to be applied to ultrahigh-speed ICs, OEICs, and the like.

When a semiconductor element is manufactured on a semiconductor substrate, a compound semiconductor of the same type or a different type as the substrate is epitaxially grown on the substrate. As the epitaxial growth method, there are a solution growth method, a vapor phase growth method, a molecular beam epitaxial growth method, a metal organic chemical vapor deposition method, and the like.

Above all, the solution growth method can grow the crystal at a temperature much lower than the melting point of the crystal to be grown in a state close to thermal equilibrium, so that a crystal having higher structural integrity than other methods can be obtained.

However, in the solution growth method, the growth rate is low, and a long growth must be performed to obtain a thick growth layer, which causes a problem such as denaturation of the substrate crystal at a high temperature. Therefore, it is necessary to increase the growth rate in order to prevent denaturation of the substrate crystal at high temperature and to improve the throughput.

[Conventional technology]

The principle of the solution growth method will be described using GaAs as an example.

FIG. 7 is an equilibrium diagram of a Ga—As system. For example, 900 ° C
Is gradually cooled to, for example, 800 ° C. Since the solubility is reduced by the cooling, the solution becomes supersaturated, GaAs is precipitated, the As concentration in the solution decreases along the liquidus line, and reaches point b.

FIG. 8 shows a conventional solution growth apparatus by a slide boat method often used in a liquid phase epitaxial growth method. The device is located in a quartz tube (not shown).

The fixed lower support 1 made of carbon has a lower cutout
11 is formed, and the lower substrate 51 is arranged there. A carbon slider 3 having an opening to be a solution reservoir 4 is mounted on the lower support. The slider is operated by operating the operating rod 32 from outside the quartz tube, so that the lower support 1
You can move left and right on the top. At this time, the solution 41 in the solution reservoir 4 of the slider moves with the slider without leaking.

Ga and GaAs as raw materials are put in the solution reservoir 4 so that the solution is saturated at the growth start temperature, and the atmosphere gas in the quartz tube is replaced with high-purity hydrogen gas.

Next, when the temperature is raised to the growth temperature, GaAs is dissolved in Ga to form a saturated solution 41.

Here, the slider 3 is moved to a position where the solution comes into contact with the lower substrate 51. Since the solution is saturated, neither the substrate elutes into the solution nor crystals deposit on the substrate.

Next, when the temperature of the solution is lowered, the solubility of the solute (As) decreases, so that excess GaAs near the substrate is deposited on the substrate, and crystal growth occurs. After the growth to the desired thickness, the slider is further moved to separate the solution from the substrate, and the solution is dropped into the solution drop 12 to terminate the growth.

During crystal growth while lowering the temperature, GaAs is deposited on the substrate from a solution close to the substrate.
As concentration decreases. However, in solutions far from the substrate, GaAs does not precipitate until a certain critical solubility is reached. This condition is called supersaturation or supercooling,
Because of such supersaturation, the solute concentration is low near the substrate and high near the substrate. The difference in the concentration causes the solute to diffuse from a high-concentration portion to a low-concentration portion, so that the solute is transported onto the substrate and crystal growth is continued.

By the way, in the conventional apparatus, the solute is replenished to the substrate only by the diffusion phenomenon, so that the growth rate is low. As a method of increasing the growth rate, there is a method of increasing the degree of supersaturation by increasing the cooling rate. In this case, nuclei of precipitation are generated in the solution and solutes are deposited on the nuclei. The effect of increasing the growth rate is not so large.

[Problems to be solved by the invention]

The solution growth method utilizes the decrease in solubility due to a decrease in temperature as described above, and the solute ratio is as low as several percent, and the growth rate is lower than that of the melt growth method. Therefore, the growth time becomes very long to obtain a thick growth layer.

In addition, the longer the substrate is exposed to high temperatures,
The amount of the element belonging to group V or group IV having a high vapor pressure to escape from the substrate increases, and the quality of the grown crystal deteriorates.

Therefore, it is necessary to increase the growth rate in order to improve the throughput and prevent denaturation of the substrate.

[Means for solving the problem]

In order to increase the growth rate on the substrate, the supply of the solute to the substrate is not only by diffusion but also by convection in the solution.

FIG. 1 shows a solution growth apparatus of the present invention, and FIGS. 1 (a) and 1 (b) are a top view and an AA cross-sectional view, respectively, where 1 is a lower support, and 11 is a lower excision. , 12 is the solution drop, 2 is the upper support, 21 is the upper cutout, 22 is the upper opening, 3 is the slider, 31 is the slider opening, 32 is the operating rod, 4 is the solution reservoir, and 41 is the solution. , 5 indicate a growth substrate, 51 indicates a lower substrate, and 61 to 64 indicate dummy substrates.

The above-mentioned problems are as follows: [1] The lower support 1, an upper support 2 having an upper cut-out portion 21 opened on the lower side where a substrate is placed, and an upper opening 22 serving as a solution reservoir, and a slider serving as a solution reservoir. A solution growth apparatus comprising a slider 3 having an opening 31 and sliding in contact with the lower support and the upper support, wherein a growth substrate 5 having a horizontal growth surface is disposed in the upper cutout. A solution growth apparatus in which dummy substrates 61 to 64 whose growth surfaces are inclined from horizontal are arranged in the slider opening portions,
[2] The solution growing apparatus according to [1], in which a spacer 7 that forms a space between the slider 3 and the growth substrate 5 is disposed in the upper cutout 21, and [3] the opening on the growth substrate 5 The solution growing apparatus according to [1], wherein the lower opening has an opening having a shape not allowing the growth surface to pass through as the upper cutout portion 21; The solution growing apparatus according to [1], which has an upper cutout portion 21 comprising a substrate disposing concave portion 211 opened to the lower side and a substrate suction opening portion 212 extending from the bottom of the concave portion to the upper surface of the upper support 2. .

[Action]

Compound semiconductor solution is a solute (As for Ga + GaAs)
It is known that the lower the concentration of is, the higher the specific gravity becomes.
When the temperature of the solution is lowered to grow crystals on the substrate, the solute is deposited on the substrate from the solution near the substrate, and the concentration of the solute is lower in the solution near the substrate than in the solution far away. Therefore, the specific gravity of the solution near the substrate is higher, and when the substrate is grown in the solution, a downward flow occurs near the substrate. Therefore, in order to utilize such a flow, the present invention arranges the growth substrate 5 horizontally on the solution 41 with the growth surface downward, and places the dummy substrates 61 to 64 in the solution by tilting the growth surface from the horizontal. Place and perform solution growth.

2 shows convection during solution growth in the arrangement according to FIG. During the solution growth, a convection as shown by an arrow in FIG. 2 occurs, and a solution having a high degree of supersaturation is always supplied to the growth substrate 5, so that the growth rate can be increased.

In order to cause convection, the growth surface of the dummy substrate needs to be arranged to be inclined from the horizontal plane, and the generation of convection becomes more active as it approaches vertical. When arranging a plurality of dummy substrates, it is desirable to arrange them at symmetrical positions with respect to the growth surface of the growth substrate from the viewpoint of making the supply of solute by convection uniform.

Although the convection of the solution also occurs on the lower substrate 51 arranged in the lower excision part 11, the solution supplied to the substrate is a solution having a low supersaturation degree after the solute is deposited by the dummy substrates 61 to 64. ， The growth rate does not increase.

In addition, when growing mixed crystals or doping impurities, the composition of the solution does not always match the composition of the precipitated crystals.
So-called segregation occurs. For example, when doping an impurity having a large segregation coefficient, the concentration of the impurity in a solution near the substrate during growth is lower than that in a solution far from the substrate because a large proportion of the impurity is taken into the substrate. In the conventional solution growth apparatus, since the transport of impurity atoms to the growth interface is performed only by diffusion, the supply of impurity atoms is slow. As a result, the concentration of impurities taken into the growing crystal gradually decreases, and a crystal having a uniform composition cannot be obtained.

According to the solution growth apparatus of the present invention, since a solution having a high impurity concentration can be supplied to the growth substrate disposed above the solution due to convection in the solution, a crystal having a uniform impurity concentration can be grown.

〔Example〕

One embodiment of the present invention will be described with reference to a solution growing apparatus shown in FIG.

After moving the slider opening 31 below the upper opening 22 to form the solution reservoir 4, the GaAs dummy substrates 61 to 64 are arranged in contact with the four side walls of the slider opening. Put Ga and GaAs to be the raw material in the reservoir. The dummy substrate may be single crystal or polycrystal.

The growth substrate 5 is arranged in the upper cutout 21, and the lower substrate 51 is arranged in the lower cutout 11.

After replacing the atmosphere gas in the quartz tube with high-purity hydrogen gas, the temperature is raised to 900 ° C and GaAs is dissolved in Ga. At this time, since the surface of the GaAs substrate is dissolved together with the raw material GaAs, the thickness of the dummy substrate must be selected so that the dummy substrate is not completely dissolved.

After the solution 41 is saturated by holding at 900 ° C. for 20 minutes, the slider 3 is pushed in the direction of the arrow to bring the solution into contact with the growth substrate 5. Hold for another 20 minutes and after homogenizing the solution,
Cool at a rate of 0.5 ° C per minute to grow crystals.

After the growth is completed, the solution is separated from the growth substrate by pushing the slider 3 in the direction of the arrow, and the solution is dropped into the solution drop 12 to lower the temperature to room temperature.

FIG. 3 shows the relationship between the growth time and the growth film thickness obtained in this example. The growth film thickness increased almost linearly with the growth time, and a crystal having a film thickness about twice as large as that of the lower substrate was grown on the growth substrate arranged above the solution.

Next, a method of arranging the growth substrate 5 in the upper cutout 21 will be described.

In assembling the solution growth apparatus shown in FIG. 1, first, the slider 3 is placed on the lower support 1 and the growth substrate 5 is placed on the slider. Next, the upper support is integrated with the lower support by covering the upper support 2 from above so that the growth substrate is accommodated in the upper cutout 21 and the slider is wrapped from three sides.

The raw material is put in the solution reservoir 4, heated, and a solution is made. After that, the slider 3 is moved to bring the solution under the growth substrate and brought into contact with the growth substrate. At this time, since the growth surface of the growth substrate comes into contact with the upper surface of the slider and rubs before contacting the solution, the grown crystal has a point-like or linear abnormal growth portion extending in the slider movement direction. May occur. These abnormally grown portions have severe irregularities on the surface, which may cause damage to the photomask, generation of powder, and the like in the subsequent element formation process. Therefore, it is necessary to minimize the occurrence of abnormally grown portions.

Therefore, a method for preventing the growth substrate 5 from directly contacting the slider 3 will be described below.

 FIG. 4 shows an arrangement method I of a growth substrate.

A spacer 7 having an outer periphery substantially equal to that of the growth substrate 5, an inner periphery slightly smaller than the outer periphery, and a thickness of about 0.5 mm is arranged below the growth substrate, and a space is provided between the growth substrate and the slider 3. Formed, and the spacer and the growth substrate are arranged in the upper cutout 21.

In this arrangement, when the slider is moved to bring the solution 4 under the growth substrate, it appears that the solution does not contact the growth substrate due to the space. However, the surface of the solution becomes upwardly convex due to surface tension, and in a space of about 0.5 mm, the solution comes into contact with the growth substrate and crystal growth proceeds.

 FIG. 5 shows a growth substrate arrangement method II.

The upper support 2 has an upper opening that is slightly wider than the growth surface of the growth substrate 5 and a lower opening that is slightly narrower than the growth surface. More specifically, in order to prevent the growth surface of the growth substrate from coming into contact with the upper surface of the slider 3, and to form an extremely narrow space between the growth surface of the growth substrate and the upper surface of the slider 3, A flange 23 having a thickness of about 0.5 mm and a thickness of about 0.5 mm is formed at the bottom of the upper cutout 21.

It is sufficient that the flange has at least a portion narrower than the growth substrate so that the growth substrate does not fall down, and does not need to be formed over the entire periphery of the lower opening.

A substrate holder 52 is placed on the growth substrate to prevent the growth substrate from rising due to the surface tension of the solution. If lifting can be prevented only by the weight of the substrate, it is not necessary to put the substrate holder 52 thereon.

 FIG. 6 shows a method III of arranging a growth substrate.

In this arrangement method, the growth surface of the growth substrate 5 and the upper surface of the slider 3 are suctioned from the upper portion of the upper support (2) so that the upper surface of the slider 3 is not in contact with the growth surface. A substrate placement recess 211 slightly deeper than the thickness of the growth substrate is formed in the upper support 2, a substrate suction opening 212 is formed from the bottom of the recess to the upper surface of the support, and a suction pipe is formed in the opening. 8 is connected, the suction tube is connected to a vacuum system outside the quartz tube, and air is exhausted, and the substrate is adsorbed to the upper support. Thus, a very narrow space is formed between the growth surface of the substrate and the upper surface of the slider.

After the growth substrate 5 was arranged in the same manner as in the arrangement methods I to III, the growth surface of the crystal grown in the same manner as in the above-mentioned embodiment was flat and uniform, and no abnormal growth portion was observed. Therefore, such a growth substrate arrangement method is effective for improving the yield of crystal growth.

〔The invention's effect〕

As described above, according to the solution growth apparatus of the present invention,
The crystal growth rate can be increased to increase the throughput, and a crystal having a flat and uniform growth surface can be grown with good yield.

Further, according to the solution growing apparatus of the present invention, a mixed crystal having a small segregation and a crystal having a uniform impurity concentration distribution can be grown.

The present invention greatly contributes to the manufacture of a device using a compound semiconductor.

[Brief description of the drawings]

 1 is a solution growth apparatus of the present invention, FIG. 2 is convection during solution growth, FIG. 3 is growth time and growth film thickness, FIG. 4 is growth substrate arrangement method I, and FIG. Fig. 6 shows the placement method III of the growth substrate, Fig. 6 shows the equilibrium diagram of the Ga-As system, and Fig. 8 shows the conventional solution growth apparatus. In the figure, 1 is a lower support, 11 is a lower cutout, 12 is a solution drop, 2 is an upper support, 21 is an upper cutout, 211 is a concave portion for arranging a substrate, 212 is a hole for sucking a substrate, and 22 is a suction hole for a substrate. The upper opening, 23 is a flange, 3 is a slider, 31 is a slider opening, 32 is an operating rod, 4 is a solution reservoir, 41 is a solution, 5 is a growth substrate, 51 is a lower substrate, and 52 is a substrate holder. 61 to 64 are dummy substrates, 7 is a spacer, and 8 is a suction tube.

Claims (4)

(57) [Claims] An upper support (2) having a lower support (1), an upper cutout (21) opened on the lower side for disposing a substrate, and an upper opening (22) serving as a solution reservoir.
And a slider (3) having a slider opening (31) serving as a solution reservoir and sliding in contact with the lower support and the upper support. A solution growth apparatus comprising: a growth substrate (5) having a horizontal growth surface; and a dummy substrate (61 to 64) having a growth surface inclined from the horizontal position in the slider opening. 2. The method according to claim 1, wherein a spacer for forming a space between the slider and the growth substrate is arranged in the upper cutout. Solution growth equipment. 3. An upper opening is formed so as to pass the growth surface of the growth substrate (5) horizontally, and a lower opening is formed as an upper cutout portion (21) having the growth surface horizontal and not passed therethrough. The solution growing apparatus according to claim 1, wherein the solution growing apparatus is provided. 4. An upper side comprising a substrate disposing recess (211) opened on the lower side of the upper support stand (2) and a substrate suction opening (212) passing from the bottom of the recess to the upper surface of the upper support stand (2). 2. The solution growing apparatus according to claim 1, further comprising a cutting portion.