JP2000294828A - Manufacturing method of GaN-based semiconductor device - Google Patents

Abstract

(57) [Problem] To provide a method for manufacturing a GaN-based semiconductor device, which can effectively suppress surface leakage current of the device by simple processing. SOLUTION: As a device structure of a GaN-based semiconductor device,
Stack of GaN-based crystal layer including p-type layer (layers 3 to
6), and heat-treating the laminate at 300 ° C. to 600 ° C. in an atmosphere containing hydrogen and / or a hydrogen compound to increase the resistance of the side surfaces S of the p-type layers 5 and 6;
Suppress surface leakage current. GaN with pn junction
This is a manufacturing method useful for GaN-based light-receiving elements, in particular.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of semiconductor devices using GaN-based materials.

[0002]

2. Description of the Related Art A GaN-based semiconductor device (hereinafter also referred to as a GaN-based device) is a semiconductor device using a GaN-based material, and includes a light-emitting device, a light-receiving device, and other devices having other functions. It is attracting attention as having a band gap and excellent heat resistance and ultraviolet resistance.

A particularly useful element structure among GaN-based elements is one in which a GaN-based crystal layer is grown in multiple layers to form a laminate, and electrodes are provided so that current flows in the lamination direction of the laminate. . For example, the device shown in FIG.
This is an example of an element having an n-junction, and includes an n-type GaN-based crystal layer 23, an undoped layer 24, and a p-type GaN-based crystal layer 25 on a sapphire crystal substrate 21 via a buffer layer 22.
Is formed, and the p-type electrode P
11, an n-type electrode P12 is provided.

When the device shown in FIG. 2 is a light emitting device, p
By passing a current between the type electrode and the n-type electrode,
Then, electrons and holes are recombined, and a light emission phenomenon occurs. In the case of a light receiving element, carriers are generated in the layer 24 by irradiation of the light to be received, and the carriers are extracted as a photocurrent flowing between the p-type electrode and the n-type electrode. In either case, the current flows so as to pass through the pn junction in the stacking direction. At this time, as shown by a broken line A in FIG. 2, it is important that a current passes through the inside of the stacked body.

[0005]

However, as shown in FIG. 2, a surface leakage current is generated on the side surface a of the laminated body (the surface where the laminated state appears), which is problematic. For example, in a light-emitting element, the part of the injected current that becomes a surface leak current does not recombine and does not contribute to light emission. Also, in the light receiving element, the part of the generated carriers that becomes the surface leakage current is recombined and disappears on the surface and does not contribute to the photocurrent. Furthermore, in the light receiving element,
Since the surface leak current flows regardless of the amount of received light even if only the reverse voltage is applied, the S / N of the light receiving element is remarkably deteriorated, and the sensitivity characteristic is deteriorated particularly in a region where the amount of light is small.

An object of the present invention is to provide a method of manufacturing a GaN-based semiconductor device which solves the above-mentioned problems and which can effectively suppress the surface leakage current of the GaN-based semiconductor device by simple processing.

[0007]

The manufacturing method of the present invention has the following features. (1) A laminate of a GaN-based crystal layer including a p-type layer is made of GaN
Growing the device as a device structure of a system-based semiconductor device, and subjecting the stacked body to an atmosphere containing hydrogen and / or a hydrogen compound so that the side surface of the p-type layer has a high resistance.
Performing a heat treatment at a temperature of 00 ° C. to 600 ° C.

(2) The laminate according to the above (1), wherein the laminate includes a pn junction and at least a side surface of the p-type layer constituting the pn junction among the p-type layers has a high resistance. Production method.

[0009]

According to the present invention, a laminate comprising a GaN-based crystal layer constituting a GaN-based device is subjected to a heat treatment at 300 ° C. to 600 ° C. in an atmosphere containing hydrogen and / or a hydrogen compound, thereby exposing the laminate to the side surface of the laminate. In the side surface of the p-type layer thus formed, in a portion from the surface of the side surface to a minute depth, the dopant is inactivated by bonding with hydrogen, and the p-type conductivity is suppressed to increase the resistance. By increasing the resistance of the side surface of the p-type layer, surface leakage current can be suppressed. Hereinafter, the "atmosphere containing hydrogen and / or hydrogen compound" used in the heat treatment for increasing the resistance of the device in the present invention is described as follows.
Also referred to as "hydrogen-containing atmosphere."

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method of the present invention will be described based on a simple example of manufacturing a light receiving element. In describing the stacked structure of the device, for convenience, a vertical distinction is provided in the stacked structure of the device assuming that the crystal substrate is located on the lower layer side and the GaN-based crystal layer is stacked upward. A direction perpendicular to the up-down direction (for example, a direction in which the upper surface of the layer spreads) is also referred to as a lateral direction. When the laminated body or each layer is viewed from the outside in the lateral direction, the outer peripheral end face where the laminated state and the thickness of the layer appear is the side surface.

The light receiving element shown in FIG.
A double hetero junction structure (n-type cladding layer (contact layer) 3, undoped low band gap layer 4, p-type cladding layer 5), p-type contact layer 6 via buffer layer 2
Is formed, and a p-type electrode P1 and an n-type electrode P2 are provided thereon to form a light receiving element. In this example, the entire device including the crystal substrate 1 has a laminated structure.
The layer 3 to the layer 6 are laminated bodies composed of GaN-based crystal layers.

As shown by hatching in FIG.
The side surfaces S of the p-type layers 5 and 6 in the stacked body made of the aN-based crystal are increased in resistance to a minute depth by heat treatment in a hydrogen-containing atmosphere. Due to the increase in the resistance, the surface leak current, which has been a problem in the description of the related art, is suppressed, and the S leakage current which has been deteriorated due to the surface leak current is reduced.
/ N, sensitivity characteristics in a region with a small amount of light, and the like are improved. In addition, the problem caused by the surface leakage current is similarly improved in elements other than the light receiving element.

[0013] GaN-based material in the present invention, the GaN-based crystal, wherein _{In X Ga Y Al Z N (} 0 ≦ X ≦ 1,0 ≦ Y ≦
1, 0 ≦ Z ≦ 1, X + Y + Z = 1) and a crystal thereof.

The GaN-based device manufactured according to the present invention may be any device having a structure that can achieve the object of the present invention. That is, an element having an element structure capable of suppressing surface leakage current by increasing the resistance of the side surface of the p-type layer may be used. For this purpose, a stack composed of a GaN-based crystal layer is provided, and a current flows in one or more of the layers in the layer thickness direction in a layer thickness direction. It is sufficient that a p-type layer to be made resistive is included. In particular, in the case of an element having a pn junction, particularly a light receiving element, the surface leakage current is a serious problem as described above, and the usefulness of the manufacturing method according to the present invention becomes more remarkable.

Among the devices having the above-described device structure, those having no pn junction include, for example, a Schottky light receiving device using only a p-type layer. Such an element is also an element in which current flows in the thickness direction of the p-type layer. By increasing the resistance of the side surface of the p-type layer, surface leakage current is suppressed, and characteristics are improved.

Further, as an element having a pn junction, L
Light emitting devices such as EDs and semiconductor lasers, and p
An in-type light receiving element, an avalanche-type light receiving element, and the like can be given. The element structure of the GaN-based light emitting element is also basically the structure as shown in FIG. 1, and the dimensional ratio of each part is changed so as to be preferable for light reception and light emission.

In the case of an element having a pn junction, the vertical positional relationship between the p-type and the n-type is not limited. However, for processing reasons, as shown in the example of FIG. Is preferable. As for the arrangement of the electrodes, a sapphire crystal substrate (insulator) is preferably used as a crystal substrate, as seen in a general GaN-based device, and therefore, as shown in the example of FIG. An arrangement in which a portion is removed from above to expose the lower n-type contact layer, an n-type electrode is provided on the exposed surface, and a p-type electrode is provided on the upper p-type contact layer of the remaining laminate. It has become. However, the present invention is not limited to these examples, and a mode in which the p-type and n-type are upside down, a mode in which a lower electrode is provided on a crystal substrate using a conductive crystal substrate, and the like may be freely selected.

The parts to be increased in resistance are cleaved, divided, and RI
The side surface of the p-type layer exposed by E or the like may be only the most effective part for suppressing the surface leakage current, or may be the entire side surface of the p-type layer. Good. The heat treatment step for increasing the resistance may be performed at any time after the side surface of the p-type layer to be increased in resistance is formed.

The hydrogen-containing atmosphere used for the heat treatment for increasing the resistance is a fluid, particularly a gas, containing one or both of hydrogen and a hydrogen compound. Hydrogen and / or
Alternatively, the content of the hydrogen compound may be not less than the extent that the surface leakage current of the element is suppressed, and the concentration is preferably 0.5% by volume or more.

Examples of the above-mentioned hydrogen compounds include hydrocarbon compounds such as ammonia and methane, and hydrogen halides such as hydrogen chloride. When the hydrogen-containing atmosphere is a mixed fluid of hydrogen and / or a hydrogen compound and another fluid, examples of the other fluid include air, nitrogen, helium, and argon.

The temperature of the heat treatment for increasing the resistance is 300
C. to 600.degree. C. is a preferable range.
00 ° C to 500 ° C is preferable in terms of protection of the electrode, and is an effective temperature range. The time of the heat treatment may be about 1 minute to 30 minutes or longer.

The depth at which the resistance of the side surface of the p-type layer is increased varies depending on the conditions of the heat treatment.
The depth is about 0 μm. The dopant that can be inactivated is one that turns a GaN-based semiconductor, such as Mg or Zn, into a p-type.

The term "increase in resistivity" as used in the present invention does not mean that the resistivity of the side surface of the p-type layer falls within a specific numerical range, but that the resistivity of the side surface of the p-type layer is the resistivity in the original state before the heat treatment. It is to be higher than. However, there is a target value of the resistivity of the side surface of the p-type layer. GaN formed as a normal p-type layer
Although the resistivity of the system crystal layer is about 1 Ωcm to 10 Ωcm, it is preferably set to 10 ⁴ Ωm or more by heat treatment for increasing the resistance, and particularly to 10 ⁶ Ωm or more.
The effect of suppressing the surface leak current is sufficiently significant. The extent to which the degree of the increase in resistance changes depending on the conditions of the heat treatment for increasing the resistance can be measured in advance by an experiment using a sample made of the same material.

Contrary to the above, the extent to which the resistance of the device manufactured according to the present invention is increased as a result depends on the fact that the surface layer on the side surface of the target p-type layer is fine. However, it is difficult to directly measure the resistivity of only that portion. In such a case, as shown in the example of the light receiving element, the degree of increase in resistance can be estimated by evaluating the entire element. The leak current of a light-receiving element manufactured and increased in resistance according to the present invention is measured. For example, it is a measurement of a leak current under a condition where only a reverse voltage is applied without receiving light. This element is annealed in a nitrogen atmosphere to release the high resistance state on the side surface of the p-type layer by the heat treatment performed by the manufacturing method of the present invention, and return to the state before the heat treatment. That is, the p-type dopant which has been inactivated by bonding with hydrogen is activated by annealing in a nitrogen atmosphere. The leak current of the light receiving element in this state is measured in the same manner as described above, and the degree of the increase in the resistance and the resistivity of that portion are calculated from the difference from the above. Furthermore, a heat treatment for increasing the resistance was performed by the manufacturing method of the present invention to reproduce the above-described leak current, and it was confirmed that this light receiving element was subjected to the heat treatment for increasing the resistance according to the manufacturing method of the present invention. May be.

When the GaN-based device of the present invention has the device structure shown in FIG. 1, the material of the crystal substrate may be any material that can grow a GaN-based material, such as sapphire,
Quartz, SiC and the like can be mentioned. Above all, a C-plane, an A-plane of sapphire, and a 6H-SiC substrate, particularly a C-plane sapphire substrate are preferable.

When a pn junction is formed in a laminate, not only a simple two-layer pn junction such as a homojunction and a heterojunction but also a three-layer DH (double heterojunction) and an SQW having a superlattice structure (Single Quantum Well), MQW
(Multiple Quantum Well) or a structure having quantum dots.

[0027]

EXAMPLE In this example, a light receiving element having the structure shown in FIG. 1 was manufactured. [Crystal Substrate, Buffer Layer] A wafer-shaped (2 inch diameter, 330 μm thick) sapphire C-plane substrate was used as the crystal substrate 1, and MOCVD was performed in a hydrogen atmosphere at 500 ° C.
An AlN buffer layer 2 having a thickness of 20 nm was formed on the substrate 1.

[Laminate composed of GaN-based crystal layer] On the buffer layer 2, an n-type GaN layer 3 (dopant Si) having a thickness of 4 μm was grown. This layer also functions as a contact layer for forming an n-type electrode. further,
An undoped In _0.1 Ga _0.9 N layer 4 having a thickness of 0.05 μm and a p-type Al _0.1 Ga _0.9 N cladding layer 5 (dopant Mg) having a thickness of 0.2 μm were sequentially grown to form a DH structure. A p-type GaN layer 6 having a thickness of 0.1 μm was further grown on the layer 5 to provide a contact layer for forming a p-type electrode.

By RIE, the layers 6 to
The layer 4 is partially removed to partially expose the upper surface of the n-type contact layer 3 as shown in FIG. 1, an n-type electrode P2 is provided on the surface, and p-type Type electrode P
And a 5 mm × 5 mm size G on the wafer substrate.
A large number of aN-based light receiving element structures were obtained.

[Heat Treatment for High Resistance] The above-mentioned state is inserted into a normal resistance heating type heat treatment furnace together with the wafer substrate, and is placed in an atmosphere of 50% by volume of hydrogen gas and 50% by volume of nitrogen gas. At 400 ° C. for 2 minutes.

[Element division] After the above heat treatment, element division was performed using a commercially available scribe device and breaking device, and a light receiving element was obtained. The number of samples is five.

For comparison with a conventional product, a light-receiving element for comparison was manufactured in exactly the same steps as above except that the heat treatment for increasing the resistance was not performed. The number of samples is five.

[Evaluation] A reverse voltage was applied to the light receiving element (element A) obtained according to the manufacturing method of the present invention and the light receiving element (element B) manufactured for comparison without light. Was applied, and the leak current of each device was examined. The results (mean values) are as follows. Element A is
When the reverse voltage is 5 V, the leak current is 0.1 nA and the reverse voltage is 10 V
In this case, the leak current was 1.5 nA, and the value of the leak current was small. On the other hand, the element B has a reverse voltage of 5
At 10 V, the leakage current was 10 nA, and at 10 V reverse voltage, the leakage current was 200 nA, which was sufficiently larger than that of the element A, and was a leakage current as a conventional problem. From these results, it was found that the manufacturing method of the present invention can sufficiently and effectively suppress the leak current of the light receiving element.

The device A was placed in a nitrogen atmosphere at 500
When the heat treatment was performed at 5 ° C. for 5 minutes, the increase in the resistance of the side surface of the p-type layer was released, and the leakage current increased to almost the same as that of the element B. Further, the device was again heated at 400 ° C. for 2 hours in a hydrogen-containing atmosphere similar to the heat treatment for increasing the resistance in the above embodiment.
After performing the heat treatment for 5 minutes, the element A returned to the original low leak current shown by the element A. From this, it has been found that it is possible to presume that the p-type layer has a high resistance on the side surface by the manufacturing method of the present invention.

[0035]

As described above, according to the manufacturing method of the present invention, the resistance of the side surface of the p-type layer included in the element structure is effectively increased by a simple process of heat treatment in a hydrogen-containing atmosphere. It is possible. Thus, a preferable G in which various characteristic deteriorations due to surface leakage current are improved.
An aN-based device can now be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structural example of a light receiving element having a pn junction as an example of a GaN-based element of the present invention.

FIG. 2 is a diagram showing a structural example of a conventional GaN-based device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crystal substrate 3-6 GaN-based crystal layer Sp Side surface of p-type layer P1, P2 Electrode

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroaki Okakawa 4-3-1 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries, Ltd. Itami Works (72) Inventor Yoichiro Ouchi 4-3-1 Ikejiri, Itami-shi, Hyogo Mitsubishi Electric Wire Inside the Itami Works of Industrial Co., Ltd. (72) Masahiro Koto 4-3-1 Ikejiri, Itami-shi, Hyogo Mitsubishi Cable Industries Co., Ltd.Itami Works, Ltd. 72) Inventor Hiroshi Hamamura 3-2-2 Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation (72) Inventor Sumito Shimizu 3-2-2 Marunouchi Chiyoda-ku, Tokyo Nikon Corporation (72) Invention Person Tatsushi Nomura 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation (72) Inventor Kiyoaki Shinohara Chiyoda-ku, Tokyo 3-chome No. 2 No. 3 Co., Ltd. Nikon in the F-term of the (reference) 5F041 AA21 CA04 CA34 CA40 CA46 CA65 CA73 CA76

Claims (2)

[Claims] A step of growing a stacked body of GaN-based crystal layers including a p-type layer as an element structure of a GaN-based semiconductor element; and forming the stacked body so that the side surface of the p-type layer has a high resistance. Performing a heat treatment at 300 ° C. to 600 ° C. in an atmosphere containing hydrogen and / or a hydrogen compound. 2. The method according to claim 1, wherein the laminate includes a pn junction, and at least a side surface of the p-type layer forming the pn junction of the p-type layer has a high resistance. .