JP2002033279A - Manufacturing method of p-type nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high quality p-type nitride semiconductor without annealing after formation. SOLUTION: With a board temperature about 1050 deg.C, a p-type nitride semiconductor layer comprising GaN doped with Mg is grown. Then in a cooling process, with the board temperature at 950-700 deg.C, cooling is done with combination of cooling time and hydrogen concentration of the atmosphere specified in a region ABCDEF which is enclosed with such points as point A (50, 1.0), point B (30, 1.8), point C (10, 4.1), point D (0, 15), point E (0, 0.5), and point F (50, 0.5), with hydrogen concentration (%) of atmosphere being X axis, a cooling time (minute) being Y axis, and coordinate being (X, Y).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaN-based light-emitting element, a light-receiving element, a diode, a transistor, etc.
A p-type nitride semiconductor among group III nitride semiconductors, in particular,
The present invention relates to a method for manufacturing a p-type nitride semiconductor that does not require annealing after formation.

[0002]

2. Description of the Related Art In recent years, GaN-based group III nitride semiconductors having a relatively large bandgap have attracted attention as materials for short-wavelength light-emitting elements used in optical information processing apparatuses and the like in which the amount of information is increasing. It is indispensable for a light emitting element such as a diode element or a laser element to have a configuration in which carriers are recombined in the vicinity of the junction surface and a pn junction emits the recombined light. As is well known, Mg
P-type nitride semiconductor doped with an acceptor such as has an extremely low Mg activation rate as compared with the donor,
It is not easy to obtain a low-resistance p-type nitride semiconductor.

Therefore, heat treatment (post-annealing) is conventionally performed on the p-type nitride semiconductor, which had a high resistance even when it was returned to room temperature after its formation, to convert the hydrogen of the complex composed of Mg and hydrogen from Mg. A method of obtaining a low-resistance p-type nitride semiconductor by dissociation is generally performed.
However, research for obtaining a low-resistance p-type nitride semiconductor without performing post-annealing is also being pursued in order to improve productivity.

A conventional p-type disclosed in Japanese Patent Application Laid-Open No. 10-135575, which does not require post-annealing, will be described below.
A method for manufacturing a type nitride semiconductor will be described.

This publication discloses metalorganic vapor phase epitaxy (MOV).
PE) on a substrate made of sapphire using the TM method.
An organic Mg compound containing a group III source such as G, a nitrogen source such as ammonia, and a p-type dopant is used at a concentration of 0.8% by volume to 2%.
A method is disclosed in which a nitrogen gas containing 0% by volume of hydrogen gas is introduced as a carrier gas, and a substrate temperature is set to 1100 ° C. to grow a p-type nitride semiconductor. Thereby, Mg
By preventing the formation of a complex consisting of hydrogen and hydrogen, a p-type nitride semiconductor exhibiting low resistance during growth is obtained. Further, in the cooling step, the temperature is lowered to 350 ° C. in a nitrogen gas atmosphere containing about 32% by volume of ammonia,
Thereafter, a method is disclosed in which the introduction of ammonia is stopped and the temperature is lowered to room temperature.

[0006]

However, the above-mentioned conventional method of manufacturing a p-type nitride semiconductor without performing post annealing has the following problems. That is, a paper (Applier) published by the inventors of the above publication after that.
d Physics Letters, vol. 72,
(1998), p. As shown in 1748), when the hydrogen concentration in the crystal growth step is increased from 2.4% to 3.7%, the activation of Mg is significantly inferior. A p-type nitride semiconductor cannot be obtained during growth. In addition, when a p-type nitride semiconductor is grown at a low hydrogen concentration, surface migration becomes insufficient, so that predetermined atoms are not arranged at optimal positions on the surface, and high-quality crystals cannot be obtained.

An object of the present invention is to solve the above-mentioned conventional problems and to obtain a high-quality p-type nitride semiconductor without performing post-annealing.

[0008]

In order to achieve the above object, the present invention provides a method for forming a p-type nitride semiconductor layer, comprising forming a low-resistance p-type nitride semiconductor in a p-type nitride semiconductor layer forming step, and then cooling the substrate to a specific substrate temperature in a cooling step. Range, that is, p in the p-type nitride semiconductor layer.
Cooling conditions were devised in a substrate temperature range of about 950 ° C. to about 700 ° C. in which inactivation of the type dopant occurs.

The first method for producing a p-type nitride semiconductor is characterized in that the p-type nitride semiconductor is formed by combining the hydrogen concentration in an atmosphere in which the inactivation of the p-type dopant is unlikely to occur and the cooling time in the specific substrate temperature range. The method is characterized by cooling a layer.

The second method of manufacturing a p-type nitride semiconductor is characterized in that the p-type nitride semiconductor is formed by combining the hydrogen concentration and the cooling rate in an atmosphere in which the inactivation of the p-type dopant hardly occurs in the specific substrate temperature range. The object semiconductor layer is cooled.

[0011] By doing so, the low resistance of the p-type nitride semiconductor can be maintained within a range that can be practically used as a p-type semiconductor.

[0012]

According to the first aspect of the present invention, a p-type dopant source, a nitrogen source and a group III source are introduced onto a substrate while maintaining the temperature of the substrate at about 950 ° C. or higher. Accordingly, the method includes a p-type nitride semiconductor layer forming step of forming a low-resistance p-type nitride semiconductor layer on the substrate, and a cooling step of cooling the substrate on which the p-type nitride semiconductor layer is formed. A method for manufacturing a p-type nitride semiconductor, wherein the temperature of the substrate in the cooling step falls from about 950 ° C. to about 700 ° C., and the p-type nitride semiconductor layer is maintained in an atmosphere capable of maintaining its low resistance. The cooling is performed by a combination of the hydrogen concentration and the cooling time, and has an effect that the inactivation of the p-type dopant in the cooling step can be suppressed.

According to a second aspect of the present invention, in the first aspect, the combination of the hydrogen concentration in the atmosphere and the cooling time is such that the hydrogen concentration (%) in the atmosphere is X-axis, the cooling time is (Minutes) on the Y axis and coordinates (X, Y), point A (50, 1.0), point B (30, 1.8), point C (10, 4.1), point D ( 0, 15), point E (0,
0.5) and an area ABCDEF surrounded by each point represented by a point F (50, 0.5), and is characterized by inactivation of a p-type dopant in a cooling step. This has the effect that the formation can be suppressed more reliably.

According to a third aspect of the present invention, the temperature of the substrate is maintained at about 950 ° C. or higher on a substrate, and a p-type dopant source, a nitrogen source and a group III source are introduced. P-type nitride comprising: a p-type nitride semiconductor layer forming step of forming a low-resistance p-type nitride semiconductor layer on a substrate; and a cooling step of cooling the substrate on which the p-type nitride semiconductor layer is formed. A method of manufacturing a semiconductor, wherein at the time when the temperature of the substrate in the cooling step is approximately 800 ° C., cooling is performed by a combination of a hydrogen concentration of an atmosphere in which the p-type nitride semiconductor layer can maintain its low resistance and a cooling rate. And has the effect of suppressing the inactivation of the p-type dopant in the cooling step.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the combination of the hydrogen concentration in the atmosphere and the cooling rate is such that the hydrogen concentration (%) in the atmosphere is X-axis, the cooling rate is (° C./min) on the Y axis, coordinates on (X, Y), point O (50, 250), point P (30, 140),
Point Q (10, 61), point R (0, 17), point S (0, 5,
00) and an area OPQRST surrounded by each point represented by a point T (50, 500), whereby the passivation of the p-type dopant in the cooling step is further ensured. It has the effect of being able to be suppressed.

Here, the concentration of the specific gas atmosphere is as follows.
It refers to the volume ratio of the gas in the atmosphere.

A specific example of an embodiment according to a method for manufacturing a p-type nitride semiconductor of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view showing a structure of a p-type nitride semiconductor according to an embodiment of the present invention. As shown in FIG. 1, a substrate 1 made of sapphire
On 1, a buffer layer 12 made of GaN and a p-type nitride semiconductor layer 13 made of GaN are sequentially formed.

Specifically, the substrate 11 is held by a substrate holder in a reaction tube (not shown), and the temperature of the substrate 11 is reduced to about 1
The temperature of the substrate 11 was cleaned while flowing nitrogen gas and hydrogen gas at 000 ° C.

Next, the temperature of the substrate 11 is lowered to about 550 ° C., and while flowing nitrogen gas as a carrier gas,
A buffer layer 12 was formed on the surface of the substrate 11 by supplying ammonia and trimethylgallium (hereinafter abbreviated as TMG).

Next, the supply of TMG to the reaction tube is stopped once, the substrate temperature is raised to about 1050 ° C., and ammonia, TMG and biscyclopentane are added while flowing nitrogen gas and hydrogen gas as carrier gases. Dienyl magnesium (hereinafter abbreviated as Cp ₂ Mg) was supplied to form a p-type nitride semiconductor layer 13 made of GaN doped with Mg as a p-type dopant on the buffer layer 12.

Next, after the supply of TMG and Cp ₂ Mg to the reaction tube is stopped, the temperature of the substrate 11 is reduced to 10 while flowing nitrogen gas, hydrogen gas and ammonia as atmosphere gases.
The temperature was lowered from 50 ° C. to 700 ° C., and thereafter, the supply of hydrogen gas and ammonia was stopped, and the substrate 11 was cooled until the temperature of the substrate 11 became 100 ° C. or lower while flowing nitrogen gas as an atmospheric gas.

Here, in the first method for manufacturing a p-type nitride semiconductor according to the present invention, in the cooling step, the substrate temperature is set to about 950 in the cooling step.
The method is characterized in that the p-type nitride semiconductor layer is cooled by a combination of the hydrogen concentration and the cooling time in an atmosphere in which the inactivation of the p-type dopant hardly occurs in a temperature range of from about 700 ° C. to about 700 ° C. explain.

In the cooling step after forming the p-type nitride semiconductor at a substrate temperature of about 950 ° C. or more, the present inventors
In particular, the inventors have found that when the temperature range of the substrate is between about 950 ° C. and about 700 ° C., the hole carrier concentration of the p-type nitride semiconductor is reduced by hydrogen existing in the atmosphere.

FIG. 2 is a graph showing the dependence of the hole carrier concentration on the substrate holding temperature in the cooling step of the method for manufacturing a p-type nitride semiconductor according to one embodiment of the present invention. That is, the hole carrier concentration of the p-type nitride semiconductor when the Mg-doped GaN layer was formed at a substrate temperature of 1050 ° C., held at a certain substrate temperature for 10 minutes in a cooling step, and then cooled to room temperature was shown. In this figure, the horizontal axis plots the substrate temperature held for 10 minutes, and the vertical axis plots the hole carrier concentration. The atmosphere in the cooling step was based on nitrogen, with an ammonia concentration of 20% and a hydrogen concentration of 30% and 0%. As is apparent from FIG. 2, when the hydrogen concentration is 30%, approximately 800
A significant decrease in the hole carrier concentration was observed in a temperature range of 950 ° C. to 700 ° C. with the minimum point at ° C. On the other hand, when the hydrogen concentration was 0%, the hole carrier concentration decreased in the same temperature range, but the degree was small. That is, 950 ° C.
It has been found that the hole carrier concentration of the p-type nitride semiconductor decreases in accordance with the concentration of hydrogen existing in the atmosphere in the temperature range of 700 ° C. This decrease in the hole carrier concentration is presumed to be due to the inactivation of the p-type dopant in the p-type nitride semiconductor by bonding with hydrogen. 0% hydrogen concentration
It is considered that the slight decrease also occurred in the case of the above, due to the influence of hydrogen generated by decomposition of ammonia.

Furthermore, the present inventors examined the relationship between the hole carrier concentration and the cooling time during which the substrate temperature drops from approximately 950 ° C. to approximately 700 ° C. in the cooling step.

FIG. 3 is a graph showing the dependence of the hole carrier concentration on the substrate cooling time from about 950 ° C. to about 700 ° C. in the cooling step of the method for manufacturing a p-type nitride semiconductor according to one embodiment of the present invention. It is. That is, the substrate temperature 10
After forming a GaN layer doped with Mg at 50 ° C., in a cooling step, it is cooled to 700 ° C. at various cooling rates,
It shows the hole carrier concentration of the p-type nitride semiconductor when subsequently cooled to room temperature, the horizontal axis represents the cooling time required for the substrate temperature to drop from approximately 950 ° C. to approximately 700 ° C., and the vertical axis represents It is a plot of hole carrier concentration. The cooling rate should be at least about 950 ° C. to about 7
The temperature was controlled to be substantially constant during 00 ° C. The atmosphere in the cooling step is based on nitrogen with an ammonia concentration of 20% and a hydrogen concentration of 50%, 30%, 10%,
And 0%. As is clear from FIG.
At any hydrogen concentration, the hole carrier concentration decreased as the cooling time became longer. From FIG. 3, the cooling time at which the hole carrier concentration at room temperature was about 1 × 10 ¹⁶ cm ⁻³ was determined. As a result, when the hydrogen concentration was 50%, 30%, 10%, and 0%, the cooling time was 1%. 0.0, 1.8, 4.1, and 15 minutes. That is, in order to secure a practical level of about 1 × 10 ¹⁶ cm ⁻³ or more as a p-type semiconductor, the substrate temperature is about 950 ° C. when the hydrogen concentration is 50%, 30%, 10%, and 0%. From 700 ° C to approximately 700 ° C.
It was found that it was necessary to be within 0, 1.8, 4.1 and 15 minutes.

FIG. 4 is a graph showing the relationship between the hydrogen concentration in the atmosphere and the substrate cooling time from about 950 ° C. to about 700 ° C. in the cooling step of the method for manufacturing a p-type nitride semiconductor according to one embodiment of the present invention. It is.

According to the above results, in the cooling step after the formation of the p-type nitride semiconductor, while the substrate temperature is reduced from about 950 ° C. to about 700 ° C., the atmosphere in which the inactivation of the p-type dopant hardly occurs. As a combination of the hydrogen concentration and the cooling time, as shown in FIG. 4, the hydrogen concentration (%) of the atmosphere is set on the X axis, and the cooling time (minute) when the substrate temperature is between about 950 ° C. and about 700 ° C. is set on the Y axis. , Coordinates (X, Y), point A
(50, 1.0), point B (30, 1.8), point C (1
0, 4.1), point D (0, 15), point E (0, 0.
5) and a combination defined in an area ABCDEF surrounded by points represented by points F (50, 0.5). The reason why the lower limit of the cooling time defined by the straight line EF is 0.5 minutes regardless of the hydrogen concentration is that if the cooling time is shorter than this, the p-type nitride semiconductor is easily cracked by thermal shock. Because it becomes.

(Embodiment 2) A p-type nitride semiconductor having a cross-sectional structure shown in FIG. 1 was manufactured in the same manner as in the first embodiment by the second method for manufacturing a p-type nitride semiconductor of the present invention.

First, using the same method as in the first embodiment, as shown in FIG.
2 and a p-type nitride semiconductor layer 13 are sequentially formed.

Here, in the second method for manufacturing a p-type nitride semiconductor according to the present invention, the temperature of the substrate in the cooling step is approximately 800.
At the time of ° C., the p-type nitride semiconductor layer is cooled by a combination of the hydrogen concentration and the cooling rate in an atmosphere where the inactivation of the p-type dopant hardly occurs.

As shown in FIG. 2, the substrate temperature is approximately 950
The temperature at which the deactivation of the p-type dopant proceeds most remarkably between about 700 ° C. and about 700 ° C. is when the substrate temperature is about 800 ° C. Therefore, shortening the time when the substrate temperature is approximately 800 ° C. as short as possible, in other words, setting the cooling rate at approximately 800 ° C. to a predetermined value or more maintains the low resistance of the p-type nitride semiconductor. It is effective on.

[0034] Therefore, from Fig. 3, in order to ensure practical about 1 × 10 ¹⁶ cm ^-3 or more as a p-type semiconductor, the substrate temperature is the cooling rate at approximately 800 ° C., the hydrogen concentration of 50
%, 30%, 10%, and 0%, respectively, at 250 ° C.
/ Min, 140 ° C / min, 61 ° C / min, and 17 ° C / min.

FIG. 5 is a graph showing the relationship between the hydrogen concentration in the atmosphere and the substrate cooling rate at approximately 800 ° C. in the cooling step of the method for manufacturing a p-type nitride semiconductor according to one embodiment of the present invention.

From the above results, in the cooling step after the formation of the p-type nitride semiconductor, the substrate temperature was about 800 ° C.
As shown in FIG. 5, the hydrogen concentration (%) of the atmosphere is the X-axis, and the cooling rate at a substrate temperature of about 800 ° C. is shown in FIG. (° C./min) on the Y axis, coordinates on (X, Y), point O (50, 250), point P (30, 140),
Point Q (10, 61), point R (0, 17), point S (0, 5,
00) and a combination defined in an area OPQRST surrounded by points represented by points T (50, 500). Here, the upper limit of the cooling rate defined by the straight line ST irrespective of the hydrogen concentration is 500 ° C./min. When the cooling rate is higher than this, cracks easily occur in the p-type nitride semiconductor due to thermal shock. Because it becomes.

The substrate 11 is made of, in addition to sapphire, Si
C, spinel, Si, GaAs, and other nitride semiconductors can be used.
And the like can also be used.
When the substrate 11 is made of a dissimilar material, the substrate 11 and the p-type nitride semiconductor layer 13 formed on the substrate 11 are substantially arranged to reduce lattice mismatch between crystals of the nitride semiconductor and the substrate 11. The buffer layer 12 made of GaN or the like is formed at a low substrate temperature of 400 ° C. to approximately 600 ° C. When the substrate 11 is made of a nitride semiconductor, the p-type nitride semiconductor layer 13 can be formed directly on the substrate 11 without forming the buffer layer 12.

The p-type nitride semiconductor layer 13 is formed on the substrate 11 in advance.
An active layer made of an n-type nitride semiconductor layer or a nitride semiconductor is formed thereon, and then formed on the active layer, thereby forming an element layer having a pn junction.

The p-type nitride semiconductor layer 13 can be formed by maintaining the temperature of the substrate 11 at about 950 ° C. or higher and introducing a p-type dopant source, a nitrogen source and a group III source. The substrate temperature is about 950 ° C. to about 1200 ° C.
Is desirable. When the substrate temperature is lower than 950 ° C., p
In the process of forming the p-type nitride semiconductor layer 13, the p-type dopant is easily deactivated by bonding with hydrogen, and the p-type dopant has a low resistance.
This is because a nitride semiconductor layer cannot be formed.
If the temperature is higher than ℃, it is difficult to form a p-type nitride semiconductor layer having good crystallinity.

The p-type nitride semiconductor layer 13 is made of GaN or Al
A single layer of GaN, InGaN, InAlGaN, or the like, or a stack of these layers can be used.
It is preferable to use Al _x Ga ₁ -xN (0 ≦ x <1), which easily obtains good crystallinity at a substrate temperature of about 950 ° C. or higher, or a material obtained by doping this with a small amount of In.

As the p-type dopant of the p-type nitride semiconductor layer 13, Mg, Zn, Cd, C or the like can be used, but it is preferable to use Mg which can obtain p-type conduction relatively easily. The concentration of the p-type dopant is 1 × 10 ¹⁹ c
Desirably, the value is not less than m ^{−3 and} less than 5 × 10 ²⁰ cm ⁻³ . When the p-type dopant concentration is lower than 1 × 10 ¹⁹ cm ⁻³ , the hole carrier concentration of the p-type nitride semiconductor layer 13 decreases, and when forming an electrode on the p-type nitride semiconductor layer 13 If the ohmic contact resistance is higher than 5 × 10 ²⁰ cm ⁻³ , the crystallinity of the p-type nitride semiconductor layer 13 is deteriorated due to the high concentration of the p-type dopant. This is because it becomes difficult to obtain p-type conduction.

The atmosphere in the reaction tube when forming the p-type nitride semiconductor layer 13 preferably contains hydrogen having a concentration of about 5% to 70%, and contains hydrogen having a concentration of about 10% to 30%. Is more preferred. If the concentration is lower than 5%, the migration of atoms on the formation surface is reduced, so that the crystallinity of the p-type nitride semiconductor layer 13 is deteriorated. This is because the incorporation rate of the type dopant decreases, and the concentration is 7
If it exceeds 0%, the p-type dopant is inactivated by hydrogen in the process of forming the p-type nitride semiconductor layer 13.

In the cooling step, at least the substrate temperature is about 95
Until the temperature falls below 0 ° C., the ammonia concentration in the atmosphere is 5%.
% Is preferable. If the ammonia concentration is lower than 5%, nitrogen is desorbed from the surface of the p-type nitride semiconductor, and the crystallinity of the surface is likely to deteriorate.

In the cooling step, the substrate temperature is approximately 950 ° C.
When the temperature is approximately 700 ° C., the ammonia concentration in the atmosphere is 30%.
The following is preferred. If the ammonia concentration is higher than 30%, the amount of hydrogen generated by the thermal decomposition of ammonia increases and the hole carrier concentration of the p-type nitride semiconductor tends to decrease.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a p-type nitride semiconductor according to the present invention will be described below with reference to the drawings.

Example 1 In this example, a p-type nitride semiconductor having a sectional structure shown in FIG. 1 was manufactured.

First, a substrate 11 made of sapphire having a mirror-finished surface is placed on a substrate holder in a reaction tube (not shown). The substrate 11 was heated for about 10 minutes while flowing hydrogen gas at a rate of 5 liters / minute and hydrogen gas at a rate of 5 liters / minute, thereby removing dirt and moisture such as organic substances attached to the surface of the substrate 11.

Next, the temperature of the substrate 11 is lowered to about 550 ° C., and ammonia is supplied at about 4 liter / min while flowing nitrogen gas as carrier gas at about 16 liter / min.
TMG is supplied at a rate of about 40 μmol / min, and a buffer layer 12 made of GaN is formed on the surface of the substrate 11 by about 0.03 μm.
It was formed with a thickness of μm.

Next, the supply of TMG to the reaction tube was stopped once, the substrate temperature was raised to about 1050 ° C., and about 12 liters / minute of nitrogen gas and about 4 liters / minute of hydrogen gas were used as carrier gases. While flowing ammonia for about 4 minutes.
Liter / min, TMG about 80 μmol / min, Cp ₂ M
g was supplied at about 0.2 μmol / min, and a p-type nitride semiconductor layer 13 made of GaN doped with Mg as a p-type dopant was formed on the buffer layer 12 to a thickness of 2 μm. The Mg concentration of this p-type nitride semiconductor layer 13 is about 2
× 10 ¹⁹ cm ^-3 . Here, the flow rate of the hydrogen gas includes the hydrogen gas for vaporizing TMG and Cp ₂ Mg.

Next, after the supply of TMG and Cp ₂ Mg to the reaction tube was stopped, about 1 nitrogen gas was used as an atmosphere gas.
The temperature of the substrate 11 was lowered from 1050 ° C. to 950 ° C. in about 0.5 minutes while flowing 2 liters / minute, hydrogen gas at about 4 liters / minute, and ammonia at about 4 liters / minute.

Thereafter, the supply of hydrogen gas is stopped, and the temperature of the substrate 11 is raised from 950 ° C. to 700 ° C. while flowing nitrogen gas at about 16 liters / minute and ammonia at about 4 liters / minute as atmosphere gases. Down in about 1.2 minutes. At this time, the cooling rate when the temperature of the substrate 11 was approximately 800 ° C. was about 210 ° C./min. Thereafter, the supply of ammonia was stopped, and nitrogen gas was supplied as atmospheric gas for about 20 hours.
The temperature of the substrate 11 is 100 ° C. while flowing at a rate of 1 liter / minute.
It cooled until it became below.

After cooling, the p-type nitride semiconductor layer 1 is removed from the reaction tube.
3 takes out the substrate 11 formed on its surface, cuts the substrate 11 into chips each having a size of 5 mm square without performing post annealing, and performs a Hall effect measurement by a Van der Pauw method. Was 1.6 × 10 ¹⁷ cm ⁻³ , and a low-resistance and high-quality p-type semiconductor layer could be formed. Since the hole carrier concentration of the p-type nitride semiconductor layer 13 before cooling is estimated to be about 2.0 × 10 ¹⁷ cm ⁻³ obtained by extrapolating the cooling time to zero in FIG. The decrease in the hole carrier concentration could be suppressed to about 20%.

(Example 2) In Example 2, a p-type nitride semiconductor was manufactured in the same procedure as in Example 1 except that the conditions of the atmosphere in the cooling step were changed. .

Specifically, the p-type nitride semiconductor layer 13 is formed
After completion, TMG and Cp were added to the reaction tube. _TwoSuspend supply with Mg
And nitrogen gas of about 12 liters /
, About 4 liters / minute of hydrogen gas and about 4 liters of ammonia
The temperature of the substrate 11 was raised to 1050 while flowing at
The temperature was lowered from 700C to 700C in about 1.7 minutes. At this time,
The temperature of the substrate 11 drops from 1050 ° C. to 950 ° C.
It takes about 0.5 minutes to drop from 950 ℃ to 700 ℃
Took about 1.2 minutes. Also, the temperature of the substrate 11 at this time
However, the cooling rate at 800 ° C. was about 210 ° C./min.
Was.

After the temperature of the substrate 11 falls below 700 ° C., the supply of hydrogen gas and ammonia is stopped, and the temperature of the substrate 11 is reduced to 100 ° C. while flowing nitrogen gas at about 20 liters / minute as an atmosphere gas. It cooled until it became below.

After cooling, the p-type nitride semiconductor layer 1 is removed from the reaction tube.
3 takes out the substrate 11 formed on its surface,
1 was cut out into a chip having a size of 5 mm square, and the Hall effect was measured. The hole carrier concentration was about 4.6 ×
It was 10 ¹⁶ cm ^-3 . P-type nitride semiconductor layer 1 before cooling
Since the hole carrier concentration of No. ³ was estimated to be about 2.0 × 10 ¹⁷ cm ⁻³ , the decrease of the hole carrier concentration in the cooling step could be suppressed to about 77%.

Comparative Example 1 In Comparative Example 1, a p-type nitride was produced in the same procedure as in Example 2 except that the cooling time (or cooling rate) in the cooling step was changed. A semiconductor was manufactured.

Specifically, the p-type nitride semiconductor layer 13 is formed
After completion, TMG and Cp were added to the reaction tube. _TwoSuspend supply with Mg
And nitrogen gas of about 12 liters /
, About 4 liters / minute of hydrogen gas and about 4 liters of ammonia
The temperature of the substrate 11 was raised to 1050 while flowing at
The temperature was lowered from ℃ to 700 ℃ in about 5.6 minutes. At this time,
The temperature of the substrate 11 drops from 1050 ° C. to 950 ° C.
It takes about 1.6 minutes to drop from 950 ℃ to 700 ℃
Took about 4.0 minutes. Also, the temperature of the substrate 11 at this time
However, the cooling rate at 800 ° C. was about 63 ° C./min.

After the temperature of the substrate 11 falls below 700 ° C., the supply of hydrogen gas and ammonia is stopped, and the temperature of the substrate 11 is reduced to 100 ° C. while flowing nitrogen gas as an atmospheric gas at about 20 liters / minute. It cooled until it became below.

After cooling, the p-type nitride semiconductor layer 1 is removed from the reaction tube.
3 takes out the substrate 11 formed on its surface,
1 is cut into 5mm square chips, and the Hall effect
The measurement showed that the hole carrier concentration was about 2 × 10
^Fifteencm^-3And there was high resistance. P-type nitride semiconductor before cooling
The hole carrier concentration of layer 13 is about 2.0 × 10¹⁷cm ^-3
In the cooling process,
Carrier concentration was reduced by about 99%.

(Embodiment 3) FIG. 6 is a sectional view showing the structure of a p-type nitride semiconductor according to another embodiment of the present invention.

In this example, a nitride semiconductor light emitting device having a cross-sectional structure shown in FIG. 6 and having a p-type nitride semiconductor layer disposed on the uppermost surface was manufactured.

The nitride semiconductor light emitting device is obtained by forming a non-doped G on a substrate 21 made of n-type GaN doped with Si.
a first n-type cladding layer 22 made of aN, a second n-type cladding layer 23 made of non-doped AlGaN, a light emitting layer 24 made of non-doped InGaN, an intermediate layer 25 made of non-doped GaN, A p-type clad layer 26 made of doped AlGaN is sequentially laminated. Pt on the p-type cladding layer 26
And Au are laminated in this order to form a p-side electrode 27, and Ti and Au are formed on the region where the substrate 21 is exposed.
Is formed. in this way,
This light emitting element is a light emitting diode in which a pn junction is formed with the light emitting layer 24 interposed therebetween.

Hereinafter, a method of manufacturing the light emitting diode device configured as described above will be described.

First, a substrate 21 made of GaN having a mirror-finished surface and made n-type by doping with Si is placed on a substrate holder in a reaction tube (not shown). At a temperature of about 1100 ° C., while flowing nitrogen gas at 4 liters / minute, hydrogen gas at 4 liters / minute, and ammonia at 2 liters / minute, the substrate 21 is heated at about 1 liter / minute.
By heating for minutes, dirt such as organic substances and moisture adhering to the surface of the substrate 21 were removed.

Next, while maintaining the temperature of the substrate 21 at about 1100 ° C., while supplying nitrogen gas as a carrier gas at about 13 liters / minute and hydrogen gas at about 3 liters / minute, ammonia was supplied at about 4 liters / minute. Min, TMG about 80μ
The first n-type cladding layer 22 made of non-doped GaN was formed at a thickness of 0.5 μm.

After forming the first n-type cladding layer 22, while maintaining the temperature of the substrate 21 at about 1100 ° C., about 15 liters / minute of nitrogen gas and about 3 liters / minute of hydrogen gas are used as carrier gases. While flowing, about 2 L / min of ammonia, about 40 μmol / min of TMG, and about 3 μm of trimethylaluminum (hereinafter abbreviated as TMA).
ol / min, undoped Al _0.05 Ga _0.95
A second n-type cladding layer 23 made of N was formed with a thickness of 0.05 μm.

After forming the second n-type cladding layer 23, the TM
Stop supplying G and TMA and reduce the temperature of substrate 21 to about 700 ° C.
, And maintained at this temperature. Nitrogen gas is used as a carrier gas at about 14 L / min, ammonia at about 6 L / min, TMG at about 4 μmol / min, and trimethylindium (hereinafter abbreviated as TMI). About 1 μmol
Per minute, the light emitting layer 24 having a single quantum well structure made of non-doped In _0.15 Ga _0.85 N is 0.002 μm.
The thickness was formed.

After the growth of the light emitting layer 24, the supply of TMI was stopped, and ammonia was supplied at 6 L / min and TMG was supplied at 2 μmol / min while flowing nitrogen gas as a carrier gas at about 14 L / min. Temperature of 1050
While increasing the temperature to ° C., an intermediate layer 25 made of undoped GaN was grown to a thickness of 0.004 μm.

When the temperature of the substrate 21 reaches 1050 ° C.,
While flowing nitrogen gas at 14 liters / minute and hydrogen gas at 4 liters / minute as carrier gas, ammonia was
Liter / min, TMG 40 μmol / min, TMA 3
By supplying μmol / min and Cp ₂ Mg at 0.4 μmol / min, a p-type cladding layer 26 made of Mg-doped Al _0.05 Ga _0.95 N was grown to a thickness of 0.2 μm.
The Mg concentration of this p-type cladding layer 26 is about 8 × 10 ¹⁹ cm
^{Was -3} .

After the growth of the p-type cladding layer 26, TMG and T
The supply of MA and Cp ₂ Mg was stopped, and nitrogen gas was flowed at about 14 liters / minute, hydrogen gas at about 4 liters / minute, and ammonia at about 2 liters / minute as atmosphere gases.
The temperature of the substrate 21 is increased from 1050 ° C. to 950 ° C. by about 0.5
Dropped in minutes.

Thereafter, the supply of hydrogen gas is stopped, and the temperature of the substrate 21 is raised from 950 ° C. to 700 ° C. while flowing nitrogen gas at about 18 liters / minute and ammonia at about 2 liters / minute as atmosphere gases. Down in about 1.2 minutes. At this time, the cooling rate when the temperature of the substrate 21 was approximately 800 ° C. was about 210 ° C./min.

After the temperature of the substrate 21 falls below 700 ° C., the supply of ammonia is stopped, and cooling is performed until the temperature of the substrate 21 becomes 100 ° C. or lower while flowing nitrogen gas as an atmospheric gas at about 20 liters / minute. After that, the substrate 21 was taken out of the reaction tube.

The obtained nitride semiconductor layer, in particular, the p-type cladding layer 26 is a low-resistance and high-quality p-type semiconductor layer without performing post-annealing for activating doped Mg. Was.

[0099] The post-annealing is not performed on the laminated structure formed of the nitride semiconductor formed as described above, and a SiO ₂ film is deposited on the surface thereof by a CVD method. SiO ₂ for patterning into a square shape for etching
A mask was formed. Then, the p-type cladding layer 26, the intermediate layer 25, and the light emitting layer 2 are formed by a reactive ion etching method.
4, the second n-type cladding layer 23, the first n-type cladding layer 22, and a part of the substrate 21 are removed at a depth of about 1 μm in a direction opposite to the laminating direction, and the surface of the substrate 21 is removed. Exposed. And by photolithography and vapor deposition,
An n-side electrode 28 formed by laminating 0.1 μm thick Ti and 0.5 μm thick Au was formed on a part of the exposed surface of the substrate 21 by vapor deposition. Further, after the etching SiO ₂ mask is removed by wet etching, Pt of 0.3 μm thickness and Au of 0.5 μm thickness are formed on almost the entire surface of the p-type cladding layer 26 by photolithography and vapor deposition. Was formed by vapor deposition.

Thereafter, the back surface of the substrate 21 is polished to 100
The thickness was adjusted to about μm, and separated into chips by scribing.

As a result, the nitride semiconductor light emitting device shown in FIG. 6 was obtained.

The light emitting device was placed on a Si diode having a pair of positive and negative electrodes with the electrode forming surface side facing downward.
Adhered by u bump. At this time, the light emitting element is mounted such that the p-side electrode 27 and the n-side electrode 28 of the light emitting element are connected to the negative electrode and the positive electrode of the Si diode, respectively. Thereafter, the Si diode on which the light emitting element is mounted is mounted on the stem by using Ag paste, and the positive electrode of the Si diode is connected to the electrode on the stem with a wire.
Thereafter, resin molding was performed to produce a light emitting diode. When this light-emitting diode was driven with a forward current of 20 mA, light was emitted in blue with a peak emission wavelength of 470 nm, and uniform surface light emission was obtained from the back side of the substrate 21. At this time, the light emission output was 4 mW, and the forward operating voltage was 3.4 V.

As described above, according to this embodiment,
In the p-type nitride semiconductor layer forming step, a low-resistance and high-quality p-type semiconductor layer can be formed as the p-type cladding layer 26. Further, in the cooling step, the p-type cladding layer 26 maintains low resistance. Can be cooled. as a result,
A nitride semiconductor light emitting device that operates at low voltage and high output can be realized without performing special processing such as post annealing.

[0080]

According to the method of manufacturing a p-type nitride semiconductor according to the present invention, a p-type nitride semiconductor layer having a low resistance is formed on a substrate, and a p-type nitride semiconductor layer is formed in a specific substrate temperature range in a cooling step. In order to cool the p-type nitride semiconductor layer with a combination of the hydrogen concentration in the atmosphere where the inactivation of the dopant is unlikely to occur and the cooling time, or a combination of the hydrogen concentration in the atmosphere and the cooling rate, special treatment such as post annealing is performed. Without performing the method, a p-type nitride semiconductor having low resistance and excellent crystal quality can be obtained.

Further, since the manufacturing process of the p-type nitride semiconductor can be simplified, the manufacturing cost of the nitride semiconductor device using the p-type nitride semiconductor can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a p-type nitride semiconductor according to one embodiment of the present invention;

FIG. 2 is a graph showing a substrate holding temperature dependency on a hole carrier concentration in a cooling step in a method for manufacturing a p-type nitride semiconductor according to one embodiment of the present invention.

FIG. 3 is a graph showing the dependence of the hole carrier concentration on the substrate cooling time from about 950 ° C. to about 700 ° C. in the cooling step of the method for manufacturing a p-type nitride semiconductor according to one embodiment of the present invention.

FIG. 4 shows the hydrogen concentration of the atmosphere in the cooling step of the p-type nitride semiconductor manufacturing method according to one embodiment of the present invention, which is about 9;
Graph showing the relationship between the substrate cooling time from 50 ° C. to approximately 700 ° C.

FIG. 5 is a graph showing the relationship between the hydrogen concentration of the atmosphere and the concentration of about 8 in the cooling step of the method for manufacturing a p-type nitride semiconductor according to one embodiment of the present invention;
Graph showing the relationship between the substrate cooling rate at 00 ° C.

FIG. 6 is a sectional view showing the structure of a p-type nitride semiconductor according to another embodiment of the present invention;

[Explanation of symbols]

 Reference Signs List 11 substrate 12 buffer layer 13 p-type nitride semiconductor layer 21 substrate 22 first n-type clad layer 23 second n-type clad layer 24 light emitting layer 25 intermediate layer 26 p-type clad layer 27 p-side electrode 28 n-side electrode

Continued on the front page (72) Inventor Hidemi Takeishi 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 4K030 AA11 AA13 AA20 BA08 BA38 DA08 FA10 JA06 JA10 JA11 LA15 5F041 AA40 AA42 CA34 CA40 CA46 CA57 CA65 CA82 CA92 DA02 DA07 DA43 5F045 AA04 AB14 AC08 AC12 AC19 AD09 AD14 AF02 AF09 BB16 CA10 CA13 DA53 DA63 DA68 EE15 EJ02 GB05 GB15 5F073 AA74 CA07 CB04 CB05 CB06 DA05 DA35 EA29 5F088 AB07 AB17 BA18 CB04 CB04

Claims (4)

[Claims] 1. A low-resistance p-type impurity is introduced onto a substrate by introducing a p-type dopant source, a nitrogen source and a group III source onto the substrate while maintaining the temperature of the substrate at about 950 ° C. or higher. A method for producing a p-type nitride semiconductor, comprising: a p-type nitride semiconductor layer forming step of forming a p-type nitride semiconductor layer; and a cooling step of cooling a substrate on which the p-type nitride semiconductor layer is formed. While the temperature of the substrate drops from about 950 ° C. to about 700 ° C. in the cooling step, the p-type nitride semiconductor layer is cooled by a combination of a hydrogen concentration of an atmosphere capable of maintaining its low resistance and a cooling time. A method for producing a p-type nitride semiconductor. 2. The combination of the hydrogen concentration of the atmosphere and the cooling time is such that the hydrogen concentration (%) of the atmosphere is the X axis, the cooling time (min) is the Y axis, and the coordinates are (X, Y). , Point A (50, 1.0), point B (30, 1.8), point C (1
0, 4.1), point D (0, 15), point E (0, 0.
5) The method of manufacturing a p-type nitride semiconductor according to claim 1, wherein the method is defined in an area ABCDEF surrounded by points represented by points F (50, 0.5). 3. A low-resistance p-type dopant is introduced onto the substrate by introducing a p-type dopant source, a nitrogen source and a group III source onto the substrate while maintaining the temperature of the substrate at about 950 ° C. or higher. A method for producing a p-type nitride semiconductor, comprising: a p-type nitride semiconductor layer forming step of forming a p-type nitride semiconductor layer; and a cooling step of cooling a substrate on which the p-type nitride semiconductor layer is formed. Wherein at the time when the temperature of the substrate in the cooling step is approximately 800 ° C., the p-type nitride semiconductor layer is cooled by a combination of a hydrogen concentration in an atmosphere capable of maintaining its low resistance and a cooling rate. For producing a nitride semiconductor. 4. The combination of the hydrogen concentration of the atmosphere and the cooling rate is such that the hydrogen concentration (%) of the atmosphere is the X axis, the cooling rate (° C./min) is the Y axis, and the coordinates are (X, Y). ), Point O (50, 250), point P (30, 140), point Q (10, 61), point R (0, 17), point S (0, 50).
4. The method for manufacturing a p-type nitride semiconductor according to claim 3, wherein the method is defined in an area OPQRST surrounded by points 0) and T (50, 500).