KR20030090996A - lifting - off Method with laser in a Growth chamber - Google Patents

Abstract

PURPOSE: A laser lift-off method in a growth chamber is provided to form free standing nitride substrate regardless of variation of temperature or atmosphere by separating a substrate from a nitride material in the growth chamber through a laser lift-off method while not transferring the nitride material grown on the substrate. CONSTITUTION: Powder is received in a reaction receptacle built in the growth chamber(31) that receives heat by an electrical furnace(30). Heat is applied to the growth chamber and a susceptor connected to the substrate to maintain a uniform temperature difference between the growth chamber and the susceptor. N2 generating gas is injected into the growth chamber to grow a nitride material on the substrate. Laser light is irradiated to the susceptor to separate the nitride material and the substrate from the growth chamber.

Description

Lifting-off Method with Laser in a Growth Chamber

The present invention relates to a laser lift off method in a growth chamber in which the nitride is separated from the substrate using a laser lift off method in the growth chamber without moving the nitride grown on the substrate.

Recently, as the demand for high efficiency short wavelength optical devices increases, research into nitride semiconductors that are known to be suitable for such applications is being actively conducted. In particular, by adding phosphors in addition to the blue violet short wavelength optical devices, With the ability to produce white light, the interest in this field is increasing day by day.

In the light emitting device such as a nitride laser diode, sapphire is mainly used as a substrate, but nitride and sapphire have high density crystallinity when a nitride layer is formed on the sapphire substrate due to a difference in lattice constant and thermal expansion coefficient. There was a problem that a defect occurred.

In order to solve this problem, attempts have been made to fabricate a light emitting device using a free standing nitride substrate. In this method of manufacturing a free standing substrate, mechanical lapping is performed after a thick nitride layer is grown on a sapphire substrate. Sapphire using a laser lift-off process that melts the interface portion of the nitride layer 10 and the sapphire substrate 11 by performing laser irradiation on the transparent sapphire substrate 11 as shown in FIG. 1. The substrate is removed.

That is, after the nitride layer is grown on the sapphire substrate installed in the high temperature growth chamber of 1000 ° C. or more, the sapphire substrate (hereinafter referred to as “sample”) on which the nitride layer is grown is transferred to the outside of the growth chamber, and then the sapphire substrate Was irradiated with a laser to separate the nitride layer from the sapphire substrate.

2A to 2D are flowcharts illustrating the laser lift-off method in more detail. As shown in the drawing, first, the transfer arm 33 passes through the bellows corrugated pipe 35 to lift-off chamber ( 31), a sapphire substrate 22 on which the nitride layer is to be grown is placed on the transfer arm 33, at which time the transfer arm adsorbs the sapphire substrate 22 in a vacuum (FIG. 2A).

Subsequently, the gate valve 30 is opened, the sapphire substrate 22 is seated on the inner surface of the growth chamber 20 by the transfer arm 33, and then the transfer arm 33 is moved to the lift-off chamber 31. After the transfer, the gate valve 30 is closed (FIG. 2B).

Then, the growth chamber 20 is heated by using the electric furnace 21, N ₂ generated from a gas such as nitrogen or ammonia injected from the injection tube 25 of the growth chamber 20, and the growth chamber. (20) The nitride layer 23 is grown on the sapphire substrate 22 by bonding Ga molecules sublimed in the gallium boat 24 inside.

Next, when growth of the nitride layer 23 is completed on the sapphire substrate 22, the gate valve 30 is opened, and the transfer arm 33 staying in the lift-off chamber 31 is moved to the growth chamber. It transfers to 20 and adsorb | sucks the sapphire substrate 22 (FIG. 2C).

Next, the transfer arm 33 which adsorbs the sapphire substrate 22 is transferred to the lift-off chamber 31, and rotated so that the sapphire substrate 22 faces the transparent window 34 so as to face the sapphire substrate ( The laser light is irradiated to 22 to separate the sapphire substrate 22 and the nitride layer 23 (FIG. 2D).

As described above, the conventional laser lift-off method must perform a process of transferring the sapphire substrate, in which the nitride layer is grown, from the growth chamber to the lift-off chamber using a transfer arm.

However, there are cases in which the nitride layer has dropped the grown sapphire substrate during transfer, and the lift-off chamber for performing laser lift-off is difficult to maintain at the same temperature as the high-growth growth chamber temperature of about 1000 ° C. The temperature difference between the and the lift-off chamber caused a temperature difference between the two chambers, causing micro cracks and bending in the nitride layer, and continuously heating both the growth chamber and the lift-off chamber. Since the work must be performed, there was a problem that the manufacturing cost is also increased.

Accordingly, the present invention is to solve the above problems, without moving the substrate on which the nitride layer is grown from the growth chamber to the lift-off chamber, by separating the substrate and the nitride in the growth chamber by using a laser lift-off method in the temperature or atmosphere It is an object of the present invention to provide a laser lift-off method in a growth chamber to obtain a good free standing nitride substrate without change.

To this end, the present invention stores the powder in a reaction vessel embedded in a growth chamber that receives heat by an electric furnace, and applies heat to the growth chamber and the susceptor to which the substrate is connected, thereby reducing the temperature difference between the growth chamber and the susceptor by T. After the growth of the nitride is completed by injecting the N ₂ generating gas into the growth chamber, and the growth of the nitride is completed, by irradiating a laser light directly to the susceptor or through a mirror (mirror) Separate the nitride from the substrate in the growth chamber.

1 is a diagram conceptually illustrating a general laser lift-off method,

2a to 2d is a process flow chart illustrating a conventional laser lift off method in more detail,

FIG. 3 shows an apparatus to which the first embodiment of the present invention relates to a laser lift-off method in a growth chamber,

FIG. 4 shows an apparatus to which the second embodiment of the present invention relates to a laser lift-off method in a growth chamber.

Explanation of symbols on the main parts of the drawings

30: electric furnace 31: growth chamber

32: boat 33: metal gallium

34, 35: injection tube 36: susceptor

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention, the embodiment to be described will be described with respect to the example of growing gallium nitride, particularly in the nitride.

<First Embodiment>

First, the gallium nitride substrate manufacturing apparatus to which the present invention is applied, as shown in FIG. 3, has a horizontal structure, a growth chamber 31 which receives heat heated in an electric furnace 30; A boat (32) located inside the growth chamber (31) and containing powder capable of producing Ga molecules that are sublimed by heat transferred from the growth chamber (31); A first injection tube 34 for injecting hydrogen chloride (HCl) from the outside through the growth chamber 31 to one side of the boat 32; A second injection tube 35 for injecting NH ₃ , which is a gas generating N ₂ , into the growth chamber 31; It is composed of a susceptor 36 exposed to the outside through the growth chamber 31 and the electric furnace 30 to seat the substrate so as to grow the gallium nitride combined with the sublimed Ga molecule and N ₂ . .

In the apparatus thus constructed, the first embodiment of the present invention first transfers the heat heated in the electric furnace 30 to the boat 32 through the growth chamber 31.

At this time, the temperature of the growth chamber 31 is maintained at about 800 ° C. to 900 ° C. using heat transferred by heating in the electric furnace, and the temperature of the susceptor 36 is adjusted to 1000 by adjusting the flow of N ₂ . It is maintained at ℃ ~ 1050 ℃.

In this state, hydrogen chloride (HCL) gas is injected into the boat 32 through the first injection pipe 34, the powder is contained in the boat 32, the powder is gallium nitride powder or metal gallium or these Preference is given to using any one selected from mixed powders of.

Subsequently, the injected hydrogen chloride gas and the powder are chemically reacted through the heat heated in the electric furnace to form a compound.

For example, when the powder is metal gallium, hydrogen chloride molecules and gallium molecules react to form gallium chloride, and the chemical formula is as follows.

2Ga + 2HCL-> 2GaCl + H _{2 ↑}

Next, when the compound formed in the boat 32 is discharged to the growth chamber, and the N ₂ product gas is injected through the second injection pipe connected to one side of the growth chamber, the N molecule generating gas and The ejected compounds combine to form gallium nitride.

At this time, the N ₂ product gas is preferably used ammonia (NH ₃ ) gas, the chemical reaction formula is as follows.

GaCl + NH _3- > GaN + HCL + H _{2 ↑}

Next, gallium nitride (GaN) thus formed is mounted on a substrate (not shown) provided on the susceptor 36 to grow. At this time, it is preferable to use a sapphire substrate, silicon carbide, or the like.

On the other hand, when the growth of the gallium nitride layer on the substrate is completed, the laser beam is irradiated to the back surface of the substrate through one side of the susceptor 36 to lift off the substrate and the gallium nitride layer.

At this time, the susceptor 36 is preferably exposed to the outside through the electric furnace 30, in particular, during the growth of gallium nitride, a circular removable heater (heater) on one side of the exposed susceptor 36 ) To maintain the same temperature as the ambient temperature, it is preferable to perform the process by removing the removable heater when the laser lift off.

In addition, although the laser light may be directly irradiated through one side of the susceptor 36 which is exposed to the outside as described above, as shown in FIG. It is preferable to irradiate laser light to one side of the susceptor 36 exposed to the outside.

Second Embodiment

4 is a perspective cross-sectional view of a gallium nitride substrate device to which a second embodiment of the present invention is applied, and shows a form of a vertical structure, first comprising: a growth chamber 41 receiving heat heated in an electric furnace 40; A reaction vessel 43 containing a powder 42 which is located inside the growth chamber 41 and generates gallium (Ga) molecules, and a gas for generating N ₂ is injected into the growth chamber 41. At least one injection tube 44, 45, a substrate 46 on which the gallium nitride layer is installed on the reaction vessel 43, and the fastening device is connected to the substrate 46, and the tube 47 is connected. It is composed of a susceptor 49, the temperature can be controlled by using a cooling gas flowing through the outside, 48).

In this arrangement, the second embodiment of the present invention first uses the heat of the electric furnace 40 and the flow of N ₂ circulated through the tubes 47 and 48 to the growth chamber 41 and the susceptor. The temperature of (49) is adjusted to be equal to 1050 ° C to 1100 ° C.

This is because when the temperature is higher than 1100 ° C., the nitride is easily decomposed, and when the temperature is lower than 1050 ° C., the fine crystals of Group III melts, for example, gallium molecules (Ga), are not easily synthesized, thereby reducing the amount of nitride to be extracted.

In this state, NH ₃ , a gas generating N ₂ , is injected into the growth chamber 40 through the injection pipes 44 and 45 at a flow rate of about 50 sccm (standard cubic centimeter per minute).

Subsequently, when NH ₃ , the gas for generating N ₂ , is chemically reacted with a powder capable of producing gallium molecules (Ga) contained in the reaction vessel 43, for example, metal gallium, nitriding is described by the following chemical reaction formula: Gallium is generated and the reaction time is about 1 to 4 hours.

2Ga + 2NH _3- > 2GaN + 3H _{2 ↑}

Subsequently, the generated gallium nitride is deposited on the substrate 46 positioned under the susceptor 49 in the form of fine crystal powder and sublimes again to grow a gallium nitride layer on the substrate 46.

In this case, the substrate 46 may be any one selected from sapphire substrate and silicon carbide, and in particular, at least one or more substrates may be seated to allow mass production.

Next, when the laser light is irradiated on the rear surface of the substrate on which the gallium nitride layer is grown by the susceptor 49 by using an apparatus (not shown) capable of irradiating laser light, the temperature in the growth chamber 41 is increased. It is possible to separate the substrate and the gallium nitride layer without falling, but as shown in Figure 4 it is preferable to irradiate the laser light using the reflection angle of the mirror (mirror).

As described in detail above, the laser lift-off method in the growth chamber of the present invention separates the substrate and the nitride in the growth chamber by using the laser lift-off method without moving the nitride grown on the substrate, without changing the temperature or the atmosphere. There is an effect of obtaining a free standing nitride substrate.

Although the invention has been described in detail only with respect to the specific examples described, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (5)

A first step of storing powder in a reaction vessel embedded in a growth chamber in which heat is transmitted by an electric furnace; A second step of maintaining a constant temperature difference between the growth chamber and the susceptor by applying heat to the growth chamber and the susceptor to which the substrate is connected; Injecting an N ₂ generation gas into the growth chamber to grow nitride on the substrate; And a fourth step of separating the nitride from the substrate in the growth chamber by irradiating a laser light to the susceptor when the growth of the nitride is completed. The method of claim 1, wherein the fourth step; A laser lift-off method in a growth chamber characterized in that the nitride and the substrate are separated by irradiating laser light to the susceptor through a mirror. The method of claim 1, wherein the susceptor; It is installed inside the growth chamber and one side is exposed to the outside through the electric furnace, The fourth step; The laser lift-off method in the growth chamber, characterized in that the nitride and the substrate are separated by irradiating laser light to one side of the susceptor exposed to the outside. According to claim 3, Removable heater is provided on one side of the susceptor exposed to the outside, The fourth step; The detachable heater installed on one side of the susceptor exposed to the outside is separated and then the laser lift off method in the growth chamber, characterized in that the nitride and the substrate by separating the laser light. The method according to any one of claims 1 to 4, The powder; Selected from gallium nitride powder, gallium metal powder or mixed powder thereof, The substrate; Sapphire or silicon carbide, And said N ₂ product gas is ammonia (NH 3) gas.