JP4635418B2 - Semiconductor device manufacturing method and semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device manufacturing method, and more particularly to a semiconductor device manufacturing method and a semiconductor device capable of securing an adhesion film between an electrode, a semiconductor layer, and a dielectric film in an electrode portion of a semiconductor laser element. .

  2. Description of the Related Art In recent years, semiconductor devices, particularly semiconductor laser elements, have become smaller, lighter, more reliable, and have higher output, and are used as light sources for electronic devices such as personal computers and DVDs and medical devices. Among these, group III-V nitride semiconductors are actively studied because they can emit light with a relatively short wavelength.

  For example, as shown in FIG. 2, a semiconductor laser using a nitride semiconductor includes an n-type semiconductor layer 32 made of an n-type GaN layer and the like on an sapphire substrate 30 via an intermediate layer 31 and an InGaN multiple quantum well. An active layer 35 and a p-type semiconductor layer 36 made of a p-type AlGaN layer having a ridge formed on the surface are laminated in this order. An n-type ohmic electrode 33 and an n-type pad electrode 34 are formed on the n-type semiconductor layer 32. A surface other than the top surface of the ridge is covered with an insulating film 38 on the p-type semiconductor layer 36, and a p-type ohmic electrode 39 is formed in ohmic contact with the p-type semiconductor layer 36 on the top surface of the ridge. Further, a protective film 37 is formed on the surface of the n-type semiconductor layer 32, the active layer 35 and the p-type semiconductor layer 36 except for a part of the region on the p-type ohmic electrode 39. In addition, a p-type pad electrode 40 electrically connected to the p-type ohmic electrode 39 is disposed.

In such a semiconductor laser, a specific electrode material is selected (for example, Patent Documents 1 and 2), or the impurity concentration of the p-type semiconductor layer is adjusted (for example, Patent Document 3), so that the semiconductor layer and the electrode In order to reduce the driving voltage and improve the light emission efficiency, the ohmic connection with the resistor is further reduced in resistance.
JP-A-5-291621 JP-A-6-275868 JP-A-10-303504

  Even if the ohmic connection between the semiconductor layer and the electrode is secured by various methods as described above, an insulating film, a protective film, or the like is interposed in a region other than the region where the semiconductor layer and the electrode are ohmic-connected. However, due to the poor adhesion between these insulating films and the electrode material, there is a problem that the ohmic connection of the electrode is impaired or the electrode itself is peeled off in the manufacturing process of the semiconductor device.

  The present invention has been made in view of the above problems, and even when an insulating film, a protective film, or the like is interposed in a region other than the region where the semiconductor layer and the electrode are ohmic-connected, the electrode material is excellent. It is an object of the present invention to provide a method for manufacturing a semiconductor device and a semiconductor device capable of preventing peeling of electrodes and the like by obtaining adhesion, achieving high reliability, and realizing low voltage and high luminance. .

  The present invention
  On the semiconductor layer having a ridge on the surface, at least the upper surface of the ridge of the semiconductor layer is exposed. ₂ A dielectric film made of
  An adhesion film made of Rh or HfO is laminated so as to cover the dielectric film,
  After heat-treating the adhesion film,
  An electrode including a nickel film or an alloy film thereof connected to the top surface of the ridge and disposed on the side surface of the ridge via an adhesion film is formed.
This is a method for manufacturing a semiconductor device.
  in this way,
  The semiconductor layer is preferably made of a p-type nitride semiconductor.
  The heat treatment is preferably performed at a temperature of 400 ° C. or higher in an oxidizing atmosphere.

  The present invention also provides a semiconductor device having an electrode electrically connected to at least the ridge upper surface in a semiconductor layer having a ridge on the surface, wherein ZrO is formed in a partial region between the semiconductor layer and the electrode. ₂ A dielectric film made of Rh or HfO is laminated in this order, the electrode includes a nickel film or an alloy film thereof, and the dielectric film is not in direct contact with the side surface of the ridge; The semiconductor device is characterized in that the film is interposed on the side surface of the ridge so as to be in contact with the nickel film or an alloy film thereof.
  In this semiconductor device, the semiconductor layer is preferably made of a p-type nitride semiconductor.

  With the above configuration, good adhesion to the semiconductor layer and protective film (dielectric film) of the electrode material can be obtained, and peeling of the electrode and the like can be prevented, and the reliability is high and low. A semiconductor device in which voltage and high luminance are realized can be obtained.

  In the method of manufacturing a semiconductor device according to the present invention, first, a dielectric film is formed on the semiconductor layer.

Here, the semiconductor device of the present invention includes all devices including a semiconductor layer as part of its configuration. For example, a light-emitting element, a light-receiving element, a CCD, a transistor, a capacitor, a resistor, a thyristor, a conversion device such as a photoelectric conversion device, a semiconductor laser, and a circuit combining two or more of these may be used. In particular, the semiconductor layer constituting the semiconductor laser is appropriate. Examples of the semiconductor layer constituting such a semiconductor device include elemental semiconductor layers such as silicon and germanium, III-V group compound semiconductor layers such as GaAs, AlN, InP, GaN, AlGaN, AlInGaN, and InN, ZnSe, and CdTe. And various semiconductor layers such as II-VI compound semiconductor layers such as CdS. Among these, nitride semiconductors, that is, GaN, AlN, InN, or mixed crystals thereof (for example, In _x Al _y Ga _1-xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1) and the like are preferable. The semiconductor layer is doped with p-type impurities (for example, Mg, Zn, Cd, Be, Ca, Ba, etc.) or n-type impurities (for example, Si, Sn, Ge, Se, C, Ti, etc.). The doping concentration is, for example, about 1 × 10 ¹⁶ to 10 ¹⁹ cm ⁻³ . In particular, a nitride semiconductor layer containing a p-type impurity is more preferable. These semiconductor layers are formed by any method known in the art, such as MOVPE, MOCVD (metal organic chemical vapor deposition), HVPE (halide vapor deposition), MBE (molecular beam vapor deposition). can do.

As the dielectric film, for example, a single layer such as SiO ₂ , SiN _x , AlN, Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , SiON, HfO ₂ , Sc ₂ O ₃ , Y ₂ O ₃ , MgO or the like A laminated layer is mentioned. Of these, ZrO ₂ is preferable. These dielectric films can be formed by known methods such as sputtering, ECR sputtering, CVD, ECR-CVD, ECR-plasma CVD, vapor deposition, and EB. The film thickness of the dielectric film can be appropriately adjusted depending on the material used and the like, for example, about 400 to 2500 angstroms, preferably about 400 to 1000 angstroms.

  The dielectric film is formed on the semiconductor layer so as to expose a part of the region on the semiconductor layer. As will be described later, the dielectric film is secured on the semiconductor layer and a region for connecting electrodes is secured. This is to insulate and protect the surface of the semiconductor layer other than the connection region with the electrode. As a method of forming a dielectric film so as to expose a part of the region, after a dielectric film is laminated on the entire surface of the semiconductor layer, a desired method is used by a method known in the art, for example, photolithography and etching processes. There is a method of forming a mask having a shape and etching the dielectric film using the mask. Alternatively, a lift-off method or the like may be used.

  Next, an adhesion film is laminated on the dielectric film. Examples of the adhesion film include a single layer or a laminated layer of a platinum group metal or the like. Examples of the platinum group metal include group VIII metals in either the long periodic table or the short periodic table, such as Rh, Ru, Pd, Pt, Os, Ir, and Hf. Among these, a single layer film containing Rh or a laminated film in which a layer containing Rh is disposed on the electrode side described later is preferable.

  Note that forming an adhesion film so as to cover the dielectric film means that the adhesion film is formed so that at least an electrode described later is in direct contact with the adhesion film without being in direct contact with the dielectric film. To do. Therefore, the adhesion film may be formed only on a part of the dielectric film, or may be formed all over the dielectric film, that is, with the same size and shape as the dielectric film, It may be formed over a part of the dielectric film to a part of the semiconductor layer, or larger than the dielectric film and in direct contact with the semiconductor layer, over a part or all of the dielectric film. It may be formed over.

  The adhesion film can be formed by a method known in the art, similarly to the dielectric film described above. When patterning into a predetermined shape, as described above, photolithography and etching methods, lift-off methods, etc. Can be used. Patterning may be performed simultaneously with the above-described dielectric film depending on the shape of the adhesion film. The film thickness of the adhesion film can be appropriately adjusted depending on the material used and the like, for example, about 50 to 500 angstroms, preferably about 100 to 300 angstroms.

  Next, the adhesion film is heat-treated. In this heat treatment, the semiconductor layer on which the adhesion film is formed is heated, for example, at a temperature of 400 ° C. or higher, preferably about 500 to 700 ° C. for 1 to 30 minutes, preferably about 5 to 20 minutes. Can be performed. The heat treatment may be performed by a furnace annealing method using an electric furnace or an RTA method using a halogen lamp, an electron beam, an excimer laser, or the like. The heat treatment is preferably performed in an air atmosphere or an oxygen atmosphere. By such heat treatment, oxygen is taken into the inside of the adhesion film from the surface of the adhesion film, whereby adhesion with an electrode described later can be improved.

Subsequently, an electrode is formed on the semiconductor layer and the adhesion film. The electrode can be formed of, for example, a single layer film or a multilayer film of a metal or an alloy such as palladium, platinum, nickel, gold, titanium, tungsten, copper, silver, zinc, tin, indium, and aluminum. Among these, a single layer film containing nickel or an alloy thereof or a laminated film in which a layer containing nickel or an alloy thereof is arranged on the side in contact with the adhesion film is preferable. The film thickness of the electrode can be appropriately adjusted depending on the material used, and for example, about 500 to 1500 angstroms is appropriate. The electrode material can be formed, for example, by a method known in the art as in the case of the dielectric film. The electrode material is formed on almost the entire surface of the semiconductor layer, and then patterned by photolithography and etching processes, a lift-off method, an EB method, and the like. Note that the electrode only needs to be formed at least on the semiconductor layer, but it is preferable that the electrode be in ohmic contact with a part of the semiconductor layer and disposed in a state of being in close contact with the adhesion film on the adhesion film. At this time, it is important that the electrode is formed so as not to be in direct contact with the dielectric film.
Embodiments of a semiconductor device manufacturing method and a semiconductor device according to the present invention will be described in detail below.

First, in order to manufacture the semiconductor laser shown in FIG. 1 as a semiconductor device, a buffer layer made of GaN and a nitride semiconductor layer made of undoped GaN are grown on a sapphire substrate 10 having a diameter of 2 inches and a C plane as a main surface. By doing so, the underlayer 11 is formed.
Next, an n-type contact layer made of GaN doped with Si of 1 × 10 ¹⁸ / cm ³ , a crack prevention layer made of In _0.06 Ga _0.94 N, and an A made of undoped AlGaN on the underlayer. An n-type cladding layer and an n-type light guide layer are grown by alternately laminating layers and B layers made of GaN doped with Si at 5 × 10 ¹⁸ / cm ³ . Thereby, the n-type semiconductor layer 12 is formed.

Subsequently, a barrier layer made of In _0.05 Ga _0.95 N doped with Si 5 × 10 ¹⁸ / cm ³ and a well layer made of undoped In _0.1 Ga _0.9 N were alternately stacked three times. An active layer 15 having a multiple quantum well structure (MQW) in which a barrier layer is stacked thereon is grown.
Next, a p-type electron confinement layer made of AlGaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Mg, a p-type light guide layer made of undoped GaN, a layer made of undoped Al _0.16 Ga _0.84 N, and Mg-doped GaN Then, a p-type cladding layer made of a superlattice layer in which layers made of these are alternately stacked, and a p-type contact layer made of p-type GaN doped with Mg at 1 × 10 ²⁰ / cm ³ are grown. Thereby, the p-type semiconductor layer 16 is formed. Thereafter, the wafer is annealed at 700 ° C. in a nitrogen atmosphere to further reduce the resistance of the p-type semiconductor layer 16.

After stacking the nitride semiconductors in this manner, a p-type semiconductor layer, an active layer, and a part of the n-type semiconductor layer are sequentially etched using a mask having a desired shape to form an n-type contact layer. To expose the surface.
Thereafter, a mask having a predetermined shape is formed on the uppermost p-type contact layer, and a striped ridge is formed on the p-type contact layer using this mask.

Subsequently, a ZrO ₂ film is formed on the p-type layer surface as a dielectric film 18 to a thickness of about 600 Å by ECR sputtering. On top of this, an Rh film is formed as the adhesion film 21 to a thickness of about 100 angstrom using a sputtering apparatus, and an annealing process is performed at 600 ° C. for about 10 minutes in an oxygen atmosphere.
Thereafter, it is immersed in a BHF solution for 20 minutes, followed by washing with water, ultrasonic washing and rinsing to dissolve and remove the dielectric film 18 and the adhesion film 21 formed on the upper surface of the striped ridge.

  Next, the p-type ohmic electrode 19 made of Ni—Au and the n-type ohmic electrode 13 made of Ti—Al are formed on the ridge and the n-type contact layer on the p-type contact layer by sputtering.

Thereafter, asher is performed at 150 ° C. for about 10 minutes, and an annealing process is further performed. Next, a protective film 17 covering a part of the p-type ohmic electrode 19 and the n-type ohmic electrode 13 is formed of SiO ₂ , and Ni is connected to the p-type ohmic electrode 19 and the n-type ohmic electrode 13. A p-type pad electrode 20 and an n-type pad electrode 14 made of -Ti-Au are formed.
Thereafter, asher is performed at 150 ° C. for about 10 minutes.

  In the semiconductor device thus obtained, the adhesion of the p-type ohmic electrode formed on the semiconductor layer and the adhesion film was evaluated.

  First, the obtained semiconductor device was subjected to ultrasonic treatment for 30 minutes twice, then treated with ultrasonic waves for 30 minutes, heat-treated at 180 ° C. for 30 minutes, and further immersed in cold water. I went twice. Then, it processed for 60 minutes with ultrasonic waves, heat-processed for 30 minutes at 220-300 degreeC, and also immersed in cold water, this process was performed 8 times, and finally, it processed with ultrasonic waves for 60 minutes. Even by such a series of ultrasonic treatment and thermal shock test, it was confirmed that no peeling of the p-type ohmic electrode was observed, and adhesion capable of sufficiently withstanding the subsequent manufacturing process was secured.

  Further, in the above-described example, ultrasonic treatment was also performed on a semiconductor device similarly manufactured except that an HfO film was formed instead of an Rh film as an adhesion film. That is, after 30 times of treatment with ultrasonic waves twice, treatment with ultrasonic waves for 30 minutes, heat treatment at 180 ° C. for 30 minutes, and further immersed in cold water, this treatment was performed twice. As a result, even in such a series of ultrasonic treatment and thermal shock test, the p-type ohmic electrode is not peeled off, and an electrode having good adhesion that can sufficiently withstand the manufacturing process of a normal semiconductor device is obtained. It was confirmed that

  On the other hand, for comparison, ultrasonic treatment and thermal shock tests were performed on the semiconductor devices similarly manufactured except that a Zr film was formed instead of an Rh film as an adhesion film in the above-described example. As a result, it was confirmed that the p-type ohmic electrode peeled off in the first 30 minutes of ultrasonic treatment and thermal shock test.

  The present invention provides a device including a semiconductor layer as a part of its structure, for example, a light emitting element, a light receiving element, a CCD, a transistor, a capacitor, a resistor, a thyristor, a photoelectric conversion device or other conversion device, a semiconductor laser, and a combination of two or more thereof It can be applied to all of the circuits.

It is a schematic sectional drawing which shows one Embodiment of the semiconductor device of this invention. It is a schematic sectional drawing which shows the semiconductor laser which is the conventional semiconductor device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sapphire substrate 11 Underlayer 12 N-type semiconductor layer 13 n-type ohmic electrode 14 n-type pad electrode 15 Active layer 16 p-type semiconductor layer (semiconductor layer)
17 Protective film 18 Dielectric film 19 P-type ohmic electrode (electrode)
20 p-type pad electrode 21 adhesion film

Claims (5)

A semiconductor layer having a ridge on the surface, forming a dielectric film made of ZrO ₂ so as to expose at least the ridge top surface of the semiconductor layer,
An adhesion film made of Rh or HfO is laminated so as to cover the dielectric film,
After heat-treating the adhesion film,
A method of manufacturing a semiconductor device, comprising forming an electrode including a nickel film or an alloy film thereof connected to an upper surface of the ridge and disposed on the side surface of the ridge via an adhesion film.   The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor layer is made of a p-type nitride semiconductor.   The method for manufacturing a semiconductor device according to claim 1, wherein the heat treatment is performed at a temperature of 400 ° C. or higher in an oxidizing atmosphere. A semiconductor device having an electrode electrically connected to at least an upper surface of a ridge in a semiconductor layer having a ridge on the surface, wherein a dielectric film made of ZrO _{2 is formed} in a partial region between the semiconductor layer and the electrode; An adhesion film made of Rh or HfO is laminated in this order, the electrode includes a nickel film or an alloy film thereof, the dielectric film is not in direct contact with the ridge side surface , and the adhesion film is nickel on the ridge side surface. A semiconductor device comprising a film or an alloy film thereof in contact with the film .   The semiconductor device according to claim 4, wherein the semiconductor layer is made of a p-type nitride semiconductor.

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