Preparation method of P-type InP ohmic contact electrode

Abstract

The invention provides a preparation method of a P-type InP ohmic contact electrode, and relates to the technical field of InP device manufacturing, and the method comprises the steps: providing a P-type InP wafer material, and carrying out the cleaning of the surface of the P-type InP wafer material; depositing an ohmic contact layer on the surface of the P-type InP wafer material; sequentially depositing a first metal layer, a second metal layer and a third metal layer on the ohmic contact layer; and carrying out two-step annealing treatment on the ohmic contact layer. According to the method, the electrode structure can be stabilized in the annealing process of preparing the ohmic contact electrode, oxidation failure of the electrode material of the ohmic contact part can be effectively prevented in the subsequent technological process, and ohmic contact has better reliability and lower resistivity.

Description

Technical Field

[0001] The invention relates to the technical field of InP device manufacturing, and in particular to a method for preparing a P-type InP ohmic contact electrode. Background Art

[0002] P-type InP (indium phosphide) and its related compounds, such as InGaAsP, are very important for high-speed electronic and optoelectronic devices, such as high electron mobility transistors (HEMTs), photodiodes (PDs), and laser diodes (LDs). In the case of InP / In0.53Ga0.47As / InP (pin) photodiodes, wide-bandgap (1.35 eV) InP is used as a capping layer on the In0.53Ga0.47As active layer to reduce dark current and improve responsivity. Reliable ohmic contacts and low resistance are essential for excellent device performance. Although excellent ohmic contacts to N-type InP can be easily achieved by Au-Ge-Ni metallization, the relatively high barrier height and large effective mass of carriers of P-type InP make it difficult to form a suitable low-resistance ohmic contact to P-type InP compared to N-type materials.

[0003] At present, P-type InP materials usually use the traditional vacuum evaporation gold-zinc alloy method to prepare the metal electrode of the ohmic contact. However, there are some serious technical problems. For example, during the high-temperature annealing process, the AuZn alloy cannot effectively prevent phosphorus from diffusing out of the contact, resulting in poor adhesion of the gold-zinc deposition and uneven metal deposition; the material surface is rough and even has black spots; and the material has poor stability. These shortcomings will cause damage to the ohmic contact, resulting in increased ohmic contact resistance or even failure, which reduces the reliability of the device. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the above shortcomings, the main purpose of the present invention is to provide a method for preparing a P-type InP ohmic contact electrode, which uses metal Pd as an electrode material, which can form a relatively stable Pd2InP compound with InP at low temperature, and form PdZn with InP doped element Zn, and then PdZn decomposes and forms , releasing Zn into InP and preventing Zn from flowing out of the doped substrate. It can not only help stabilize the electrode structure during the annealing process of preparing the ohmic contact electrode, but also effectively prevent the oxidation failure of the electrode material of the ohmic contact part during other subsequent processes.

[0006] (II) Technical solution

[0007] In order to achieve the above-mentioned object, the present invention provides a method for preparing a P-type InP ohmic contact electrode, comprising: providing a P-type InP wafer material, and cleaning the surface of the P-type InP wafer material; depositing an ohmic contact layer on the surface of the P-type InP wafer material; depositing a first metal layer, a second metal layer and a third metal layer in sequence on the ohmic contact layer; and performing a two-step annealing treatment on the ohmic contact layer.

[0008] In the above solution, the ohmic contact layer material includes Pd and Pt.

[0009] In the above scheme, the doping concentration at the location where the ohmic contact layer is deposited on the surface of the P-type InP wafer material is greater than or equal to 1×10 15 cm -3 .

[0010] In the above scheme, an ohmic contact layer is deposited on the surface of a P-type InP wafer material, including: using a deposition technique to deposit a layer of SiO2 on the surface of the P-type InP wafer material; using ultraviolet exposure technology to make an ohmic contact electrode pattern on the surface of SiO2; using an etching process to etch away the SiO2 at the location of the ohmic contact electrode pattern; using a deposition technique to deposit an ohmic contact layer on the surface of the ohmic contact electrode pattern.

[0011] In the above scheme, an ohmic contact layer is deposited on the surface of a P-type InP wafer material, wherein the deposition method includes evaporation, DC magnetron sputtering, reactive magnetron sputtering, radio frequency magnetron sputtering, low pressure chemical vapor deposition and ion beam assisted deposition.

[0012] In the above scheme, an ohmic contact layer is deposited on the surface of the P-type InP wafer material, wherein the deposition thickness of the ohmic contact layer ranges from 10Å to 5000Å.

[0013] In the above scheme, on the ohmic contact layer, the deposition method of the first metal layer includes evaporation, DC magnetron sputtering, reactive magnetron sputtering, radio frequency magnetron sputtering, low pressure chemical vapor deposition, metal organic chemical vapor deposition and ion beam assisted deposition, wherein the deposition thickness of the first metal layer ranges from 100Å to 5000Å.

[0014] In the above solution, the deposition method of the second metal layer and the deposition method of the third metal layer are the same as the deposition method of the first metal layer.

[0015] In the above scheme, the deposition thickness of the second metal layer ranges from 100Å to 5000Å, and the deposition thickness of the third metal layer ranges from 10Å to 5000Å.

[0016] In the above scheme, the ohmic contact layer is subjected to a two-step annealing treatment, including: setting the temperature range of the first step annealing to 300°C to 400°C, and the duration range to 10S to 120S; after completing the first step annealing, setting the temperature range of the second step annealing to 400°C to 1200°C, and the duration range to 1S to 60S.

[0017] (III) Beneficial effects

[0018] The technical solution of the embodiment of the present invention has at least the following beneficial effects:

[0019] (1) This method uses metal Pd as the electrode material, which can form a relatively stable Pd2InP compound with InP at low temperatures. It can not only help stabilize the electrode structure during the annealing process of preparing the ohmic contact electrode, but also effectively prevent the oxidation failure of the ohmic contact electrode material during other subsequent processes.

[0020] (2) The Pd / Zn / Ni / Au structure used in this method has better reliability and lower resistivity than the ohmic contact of the traditional Zn / Au structure.

[0021] (3) The two-step annealing process used in this method can effectively prevent the loss of substrate material, thereby improving the stability of the material and providing a new solution for improving device parameters and reliability for the subsequent preparation of semiconductor laser devices based on P-type InP wafer materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart schematically shows a method for preparing a P-type InP ohmic contact electrode according to an embodiment of the present invention;

[0023] Figure 2 Schematically shows a flow chart of depositing an ohmic contact layer on a surface of a P-type InP wafer material according to an embodiment of the present invention;

[0024] Figure 3 A SEM image of a metal surface after primary annealing according to an embodiment of the present invention is schematically shown;

[0025] Figure 4 The IV curve diagram of the metal semiconductor contact resistance after one annealing according to an embodiment of the present invention is schematically shown;

[0026] Figure 5 Schematically showing a SEM image of a metal surface after secondary annealing according to an embodiment of the present invention;

[0027] Figure 6 The IV curve diagram of the metal semiconductor contact resistance after two annealings according to an embodiment of the present invention is schematically shown;

[0028] Figure 7 A schematic diagram showing the structure of a P-type InP ohmic contact electrode according to an embodiment of the present invention;

[0029] Figure 8 The diagram schematically shows a mask layout for measuring the metal contact resistance of a P-type InP ohmic contact electrode using a CTLM method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0031] Figure 1 The flowchart of the method for preparing a P-type InP ohmic contact electrode according to an embodiment of the present invention is schematically shown.

[0032] like Figure 1 As shown, in an embodiment of the present invention, the method for preparing a P-type InP ohmic contact electrode further includes operations S1 to S4.

[0033] In operation S1 , a P-type InP wafer material is provided, and a surface of the P-type InP wafer material is cleaned.

[0034] Specifically, a P-type InP wafer material is provided, the surface of which can be low-doped or high-doped, wherein the doping concentration at the location where the ohmic contact layer is deposited on the surface of the P-type InP wafer material is greater than or equal to 1×10 15 cm -3 .

[0035] Exemplarily, the surface of the P-type InP wafer material is cleaned, wherein the cleaning method may utilize any of ultrasonic cleaning, chemical cleaning, plasma cleaning, deionized water washing or drying treatment, for example.

[0036] In operation S2 , an ohmic contact layer is deposited on the surface of the P-type InP wafer material.

[0037] Figure 2 The flowchart of depositing an ohmic contact layer on the surface of a P-type InP wafer material according to an embodiment of the present invention is schematically shown.

[0038] like Figure 2 As shown, in an embodiment of the present invention, depositing an ohmic contact layer on the surface of a P-type InP wafer material may further include operations S21 to S24.

[0039] In operation S21, a layer of SiO2 is deposited on the surface of the P-type InP wafer material by using a deposition technology.

[0040] Exemplarily, a layer of SiO2 is deposited on the surface of the P-type InP wafer material using plasma enhanced chemical vapor deposition technology.

[0041] In operation S22, an ohmic contact electrode pattern is formed on the surface of SiO2 by using ultraviolet exposure technology.

[0042] In operation S23, SiO2 at the location of the ohmic contact electrode pattern is etched away using an etching process.

[0043] Exemplarily, the SiO 2 at the location of the ohmic contact electrode pattern is etched away using a RIE (reactive ion etching) process and an ICP (inductively coupled plasma) process.

[0044] In operation S24, an ohmic contact layer is deposited on the surface of the ohmic contact electrode pattern position by using a deposition technology.

[0045] Specifically, the material of the ohmic contact layer may be, for example, metal Pd or metal Pt. Preferably, the material of the ohmic contact layer deposited on the P-type InP surface is metal Pd.

[0046] In an embodiment of the present invention, an ohmic contact layer is deposited on the surface of a P-type InP wafer material, wherein the deposition method includes evaporation, DC magnetron sputtering, reactive magnetron sputtering, radio frequency magnetron sputtering, low pressure chemical vapor deposition and ion beam assisted deposition. Preferably, evaporation deposition is used.

[0047] In an embodiment of the present invention, an ohmic contact layer is deposited on the surface of a P-type InP wafer material, wherein the deposition thickness of the ohmic contact layer ranges from 10 Å to 5000 Å, and preferably is 200 Å.

[0048] Through the embodiments of the present invention, metal Pd is used as the electrode material, which can form a relatively stable Pd2InP compound with InP under low temperature conditions. It can not only help stabilize the electrode structure during the annealing process of preparing the ohmic contact electrode, but also effectively prevent the oxidation failure of the ohmic contact part of the electrode material during other subsequent back-end processes.

[0049] In operation S3 , a first metal layer, a second metal layer, and a third metal layer are sequentially deposited on the ohmic contact layer.

[0050] Exemplarily, the material of the first metal layer may be Zn metal.

[0051] Specifically, on the ohmic contact layer, the deposition method of the first metal layer includes evaporation, DC magnetron sputtering, reactive magnetron sputtering, radio frequency magnetron sputtering, low pressure chemical vapor deposition, metal organic chemical vapor deposition and ion beam assisted deposition, wherein the deposition thickness of the first metal layer ranges from 100 Å to 5000 Å.

[0052] In the embodiment of the present invention, the deposition method of the second metal layer and the deposition method of the third metal layer are the same as the deposition method of the first metal layer.

[0053] Exemplarily, the material of the second metal layer may be Ni metal, wherein the deposition thickness of the second metal layer ranges from 100Å to 5000Å.

[0054] Exemplarily, the material of the third metal layer may be Au metal, wherein the deposition range of the third metal layer is 10 Å to 5000 Å, and the preferred thickness is 2000 Å.

[0055] In operation S4, the ohmic contact layer is subjected to a two-step annealing process.

[0056] In an embodiment of the present invention, the ohmic contact layer is subjected to a two-step annealing treatment, including: setting the temperature range of the first step annealing to 300°C to 400°C, and the duration range to 10S to 120S; after completing the first step annealing, setting the temperature range of the second step annealing to 400°C to 1200°C, and the duration range to 1S to 60S.

[0057] Preferably, in the two-step annealing treatment, the first step annealing temperature is 370° C. and the time is 25 seconds, and the second step annealing temperature is 450° C. and the time is 5 seconds.

[0058] It should be noted that the above annealing process needs to be carried out in a protective atmosphere of nitrogen and hydrogen gases.

[0059] Through the embodiments of the present invention, the two-step annealing process used in the method can effectively prevent the loss of substrate material, thereby improving the stability of the material, and providing a new solution for improving device parameters and reliability for the subsequent preparation of semiconductor laser devices based on P-type InP wafer materials.

[0060] Figure 3 The SEM image of the metal surface after primary annealing according to an embodiment of the present invention is schematically shown. Figure 4 The IV curve diagram of the metal semiconductor contact resistance after a single annealing according to an embodiment of the present invention is schematically shown. Figure 5 The SEM image of the metal surface after secondary annealing according to an embodiment of the present invention is schematically shown. Figure 6 The IV curve diagram of the metal semiconductor contact resistance after two annealings according to an embodiment of the present invention is schematically shown.

[0061] For example, in the method of using Pd / Zn / Ni / Au to make a P-type InP ohmic contact electrode, since Pd metal has a certain anti-oxidation property, it can prevent the ohmic contact from being partially oxidized and failing during the ohmic contact annealing and subsequent processes. Secondly, the annealing test in a nitrogen-hydrogen atmosphere found that the ohmic contact after the secondary annealing has better reliability, such as Figure 3 and Figure 4 As shown in Figure 2, the Pd / Zn / Ni / Au structure has the characteristics of rough metal surface and poor ohmic contact performance after one annealing, while Figure 5 and Figure 6 As shown in the figure, the Pd / Zn / Ni / Au structure shows a good ohmic characteristic curve after the secondary annealing, and the metal surface is smooth and has no defects. This is because at the high temperature of the secondary annealing, Pd forms PdP2 with the substrate InP, which prevents the outward diffusion of doped Zn in the InP substrate and forms a stable ohmic contact.

[0062] Through the embodiments of the present invention, ohmic contact metal Pd is deposited on a clean P-type InP surface, and then Zn metal, Ni metal, and Au metal are sequentially deposited on the deposited ohmic contact layer. Finally, the semiconductor is subjected to secondary high-temperature annealing, so that the effectively formed PdP2 prevents the outward diffusion of doped Zn in the InP substrate, forms a stable ohmic contact, and improves the reliability of the device.

[0063] Based on the above-mentioned method for preparing a P-type InP ohmic contact electrode, an embodiment of the present invention provides a P-type InP ohmic contact electrode.

[0064] Figure 7 The structure of a P-type InP ohmic contact electrode according to an embodiment of the present invention is schematically shown.

[0065] like Figure 7 As shown, the P-type InP ohmic contact electrode is composed of a semiconductor wafer, a Pd metal ohmic contact layer, a Zn metal layer, a Ni metal layer and an Au metal layer from bottom to top.

[0066] The Pd / Zn / Ni / Au structure adopted by the embodiments of the present invention has better reliability and lower resistivity than the ohmic contact of the traditional Zn / Au structure.

[0067] Figure 8 The diagram schematically shows a mask layout for measuring the metal contact resistance of a P-type InP ohmic contact electrode using a CTLM method according to an embodiment of the present invention.

[0068] Exemplarily, a P-type InP semiconductor is cleaned with acetone, ethanol, and deionized water, and after a photolithography plate is made, an ultraviolet exposure technique is used to make the desired ohmic contact electrode pattern on the surface of the P-type InP, and then a layer of Pd metal is deposited on the surface of the P-type InP using radio frequency magnetron sputtering technology as an ohmic contact layer, and a layer of Zn metal is deposited on the Pd surface using radio frequency magnetron sputtering technology, and a layer of Ni metal is deposited on the Zn surface using radio frequency magnetron sputtering technology, and a layer of Au metal is deposited on the Ni surface using radio frequency magnetron sputtering technology. After the production is completed, the ohmic contact is subjected to rapid secondary annealing in a rapid annealing furnace in a nitrogen and hydrogen atmosphere to form an ohmic contact. Figure 8 As shown, a mask pattern is prepared based on the produced ohmic contact electrode, and then the metal contact resistance of the P-type InP ohmic contact electrode is measured using the CTLM (Contactless Transmission Line Model) method.

[0069] Through the embodiments of the present invention, a P-type InP ohmic contact is made using a Pd / Zn / Ni / Au structure, which reduces the damage of the ohmic contact, obtains a lower ohmic contact resistance and better adhesion, and increases the reliability of the device.

[0070] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a P-type InP ohmic contact electrode, the method comprising: Providing a P-type InP wafer material, and cleaning the surface of the P-type InP wafer material; Depositing an ohmic contact layer on the surface of the P-type InP wafer material; Depositing a first metal layer, a second metal layer and a third metal layer in sequence on the ohmic contact layer; The ohmic contact layer is subjected to a two-step annealing process. 2 . The method for preparing a P-type InP ohmic contact electrode according to claim 1 , wherein the ohmic contact layer material comprises Pd and Pt.

3. The method for preparing a P-type InP ohmic contact electrode according to claim 1, wherein the doping concentration at the location where the ohmic contact layer is deposited on the surface of the P-type InP wafer material is greater than or equal to 1×10 15 cm -3 .

4. The method for preparing a P-type InP ohmic contact electrode according to claim 1, wherein the step of depositing an ohmic contact layer on the surface of the P-type InP wafer material comprises: Depositing a layer of SiO2 on the surface of the P-type InP wafer material by using a deposition technology; Using ultraviolet exposure technology to make an ohmic contact electrode pattern on the surface of the SiO2; Etching away SiO2 at the position of the ohmic contact electrode pattern by using an etching process; An ohmic contact layer is deposited on the surface of the ohmic contact electrode pattern position by using a deposition technology.

5. The method for preparing a P-type InP ohmic contact electrode according to claim 1 or 3, wherein an ohmic contact layer is deposited on the surface of the P-type InP wafer material, wherein the deposition method comprises evaporation, DC magnetron sputtering, reactive magnetron sputtering, radio frequency magnetron sputtering, low pressure chemical vapor deposition and ion beam assisted deposition.

6. The method for preparing a P-type InP ohmic contact electrode according to claim 1 or 2, wherein an ohmic contact layer is deposited on the surface of the P-type InP wafer material, wherein the deposition thickness of the ohmic contact layer ranges from 10Å to 5000Å.

7. The method for preparing a P-type InP ohmic contact electrode according to claim 1, wherein the deposition method of the first metal layer on the ohmic contact layer comprises evaporation, DC magnetron sputtering, reactive magnetron sputtering, radio frequency magnetron sputtering, low pressure chemical vapor deposition, metal organic chemical vapor deposition and ion beam assisted deposition, wherein: The deposition thickness of the first metal layer ranges from 100Å to 5000Å. 8 . The method for preparing a P-type InP ohmic contact electrode according to claim 1 , wherein a deposition method of the second metal layer and a deposition method of the third metal layer are the same as a deposition method of the first metal layer. 9 . The method for preparing a P-type InP ohmic contact electrode according to claim 8 , wherein the deposition thickness of the second metal layer is in the range of 100Å to 5000Å, and the deposition thickness of the third metal layer is in the range of 10Å to 5000Å.

10. The method for preparing a P-type InP ohmic contact electrode according to claim 1, wherein the ohmic contact layer is subjected to a two-step annealing treatment, comprising: The temperature range of the first step annealing is set to 300°C to 400°C, and the duration range is 10S to 120S; After the first step annealing is completed, the temperature range of the second step annealing is set to 400° C. to 1200° C., and the duration range is 1S to 60S.

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