CN101303459A - Fabrication method of traveling wave electrode electroabsorption modulator and mode spot converter integrated device - Google Patents

Abstract

A method for manufacturing an integrated device of a traveling wave electroabsorption modulator and a mode-spot converter, comprising: sequentially growing an indium-phosphorus stress buffer layer, an n-1.2Q quaternary layer, an n-indium-phosphorus spacer layer, and a lower layer respectively on a substrate Confinement layer, multiple quantum wells, upper confinement layer and defect diffusion layer; grow and etch a silicon oxide mask to protect the electroabsorption modulator region, phosphorus ion implantation, annealing, remove silicon oxide mask and defect diffusion layer; Etch the tapered upper waveguide and lower waveguide in the device material area; epitaxially p-type indium phosphide thin layer, p-type indium gallium arsenide stop layer, p-type indium phosphide cap layer and p-type indium gallium arsenide contact layer in sequence; etch The ridge structure of the EA region; etching the insulating plane of the EA region; making tantalum nitride film resistors; making p-type metal ohmic contacts; making N-type metal ohmic contacts; making polyimide bridges; on the electroabsorption modulator material region Fabrication of titanium gold electrode structure; thinning and cleavage to complete fabrication.

Description

Fabrication method of traveling wave electrode electroabsorption modulator and mode spot converter integrated device

technical field

The invention belongs to the technical field of semiconductors, and relates to a method for manufacturing an electroabsorption modulator with a traveling wave electrode structure, in particular to a method for manufacturing an integrated device of a traveling wave electroabsorption modulator and a mode-spot converter.

Background technique

In recent years, with the rapid development of the information industry, people's demand for high-speed networks has become more and more intense. Modulators with high-frequency bandwidths are key components for realizing high-speed systems. Improving the modulation bandwidth of modulators has become a research hotspot in recent years. The electroabsorption modulator (EAM) with a lumped electrode structure may be too high because of its RC limitation, generally around 20GHz. In order to obtain a higher bandwidth, electroabsorption with a traveling wave electrode structure can be used The modulator (hereinafter referred to as TEAM), which is different from the lumped EAM, has no resistance-capacitance (RC) limitation, and can reach a bandwidth of 40GHz or higher after scientific design.

The electro-absorption modulator is a double-terminal coupled device, which requires low insertion loss and high offset tolerance. In order to improve the coupling efficiency of the electro-absorption modulator and the optical fiber and effectively reduce the insertion loss of the device, there are currently two main methods: 1) Using a large optical cavity structure with separate confinement layers, growing very thick on both sides or one side of the active region The quaternary material is heavily doped, so that the electric field is confined in the thin active layer, while the optical field is confined in the quaternary layer and the active layer, thereby improving the coupling efficiency of the electroabsorption modulator and the fiber . (See literature: IEEE PHOTONICSTECHNOLOGY LETTERS.2004.16(2), pp.440-442.) 2) Integrated mode converter. The semiconductor mode spot converter can almost adiabatically convert the asymmetric near-field distribution of the active device into a symmetrical input or output near-field, which can not only improve the coupling efficiency of the active device and the optical fiber, but also improve its partial adjustment capacity Difference. (See literature: Semicond. Sci. Technol., Vol.20, No.9, 2005, pp.912-916).

Contents of the invention

The purpose of the present invention is to provide a method for manufacturing an integrated device of a traveling wave electroabsorption modulator and a mode-spot converter, which integrates a terminal load film resistor, and can optimize the resistance value of the load resistor to improve the modulation bandwidth. A traveling-wave electrode structure is used to obtain higher modulation bandwidth, and the integrated mode spot converter improves the coupling efficiency of active devices and optical fibers.

The invention provides a method for manufacturing an integrated device of a traveling wave electroabsorption modulator and a mode-spot converter, which is characterized in that the manufacturing process includes the following steps:

Step 1: sequentially grow indium phosphorus stress buffer layer, n-1.2Q quaternary layer, n-indium phosphorus space layer, lower separate confinement layer, multiple quantum wells, upper separate confinement layer on a substrate by metal-organic vapor deposition method layer, defect diffusion layer;

Step 2: grow a layer of silicon oxide mask on the defect diffusion layer, use wet etching to remove the silicon oxide mask in the template converter material area, form a silicon oxide pattern in the middle to protect the material area of the electroabsorption modulator, and conduct phosphorus ion Implantation, annealing, quantum well hybridization, blue-shifting the bandgap wavelength of the material, and finally removing the silicon oxide mask and defect diffusion layer with chemical reagents;

Step 3: Etching the tapered upper waveguide and lower waveguide structures of the spot converter in the template converter material area;

Step 4: epitaxially p-type indium phosphide thin layer, p-type indium gallium arsenide-phosphide selective chemical stop layer, p-type indium phosphide capping layer and p-type indium gallium arsenide contact layer on the device in sequence by metal-organic vapor deposition;

Step 5: Etching the ridge structure at the material region of the electroabsorption modulator by using a combination of chemical wet and reactive ion dry etching;

Step 6: Wet etch the material area of the electroabsorption modulator to the substrate to form an insulating plane, which is used as an insulating medium for the input and output part of the microwave transmission line of the traveling wave electrode;

Step 7: On one side of the insulating plane of the substrate, a tantalum nitride film resistor is manufactured by stripping with glue;

Step 8: Make a p-type metal ohmic contact on the ridge structure by stripping with glue;

Step 9: making N-type metal ohmic contacts on both sides of the ridge structure on the material area of the electroabsorption modulator by stripping with glue;

Step 10: Fabricating polyimide bridges on the electroabsorption modulator material area;

Step 11: Fabricate a titanium-gold traveling-wave electrode structure on the material area of the electroabsorption modulator;

Step 12: Thinning and cleavage to complete the fabrication of the entire device.

The substrate mentioned therein is a semi-insulating indium phosphide substrate.

The thickness of the i-indium phosphorus defect diffusion layer is 200nm.

The material of the multiple quantum wells is InGaAsP.

Wherein the tapered upper waveguide adopts the reactive ion dry etching method, and the width of the tapered upper waveguide is linearly reduced from 3 μm to 0 μm; the lower waveguide adopts the wet etching method, and its width is 6 μm.

The tantalum nitride thin film resistor mentioned therein has a surface resistance value of 50Ω/□, and load resistances with different resistance values of 50, 40, 30, and 20 ohms can be realized by adjusting the width of the thin film resistor.

The material of the defect diffusion layer is i-indium phosphide.

Description of drawings

In order to further illustrate the method of the present invention, the present invention is specifically described below in conjunction with accompanying drawing and specific embodiment, wherein:

Fig. 1 is a cross-sectional view after one epitaxy;

FIG. 2 is a schematic perspective view of P ion implantation;

Fig. 3 is a three-dimensional schematic diagram of a double waveguide structure of a spot mode converter;

Figure 4 is a cross-sectional view after secondary epitaxy;

Fig. 5 is a schematic diagram of modulator region ridge etching;

Fig. 6 is a top view of P, N ohm contacts, thin film resistors and polyimide bridges;

Figure 7 is a top view of the device after fabrication.

Detailed ways

的二氧化硅(SiO₂)掩膜9。Figure 1 is a cross-sectional view after one epitaxy. A 500nm-thick InP stress buffer layer 2 is grown on the substrate 1 by metal-organic chemical vapor deposition (MOCVD), which mainly adjusts the lattice mismatch, and then sequentially grows on it: n-1.2Q quaternary layer 3 The thickness of the n-1.2Q quaternary layer 3 is used as the high refractive index layer of the lower waveguide of the mode spot converter; the thickness of the n-InP space layer 4 is 0.25 μm, and this layer needs to be heavily doped, because N The ohmic contact layer will be made on it; the thickness of the lower confinement layer 5 is 100nm respectively, and this layer is in order to confine the light field; InGaAsP multiquantum well 6; The layers are the same; the thickness of the defect diffusion layer 8 is 200 nm. Using plasma enhanced chemical vapor deposition (PECVD), grow 4000

Silicon dioxide (SiO ₂ ) mask 9 .

FIG. 2 is a schematic perspective view of P ion implantation. Etching away the SiO ₂ in the template converter material region 10, leaving only the SiO ₂ mask 9 in the electroabsorption modulator material region 11, its function is to protect the electroabsorption modulator material region 11 in the ion implantation process, so that the The surface of the material in the region will not be implanted with defects, while the template converter material region 10 is not protected by the SiO ₂ mask 9, and P ions with an energy of 50KeV and a dose of 1×10 ¹⁴ cm ^-2 are implanted on the surface of the material. The defect diffusion layer 8 is introduced into defects by ion implantation, and in the subsequent rapid annealing process, the defects diffuse from the defect diffusion layer 8 to the upper confinement layer 7 and the multiple quantum wells 6 respectively, changing the energy band structure of the multiple quantum wells 6, making the template The material bandgap wavelength of the converter material region 10 has a "blue shift" phenomenon relative to the electroabsorption modulator material region 11, which is the quantum well hybrid effect induced by ion implantation. The purpose of doing this is to make the material band gap of the template converter material region 10 larger than the material of the electroabsorption modulator material region 11, so that the input light with a wavelength slightly longer than the wavelength of the material band gap of the electroabsorption modulator material region 11 passes through the template converter material. There is little absorption when propagating in the region 10, which reduces the insertion loss of the device. Finally, the silicon oxide mask 9 is removed with hydrofluoric acid, and the defect diffusion layer 8 is etched away with a 4:1 solution of hydrochloric acid and water.

Fig. 3 is a three-dimensional schematic diagram of a double waveguide structure of a spot mode converter. The tapered upper waveguide structure 12 is etched by reactive ion etching, the etching conditions are: Ar:CH4:H2=5:18:45, 100W, 6 minutes, the etching depth is 300nm, and then the lower waveguide structure 13 is etched out by wet method , the etching conditions are: liquid bromine, 10 seconds, and the etching depth is 800nm. The spot mode converter of the double waveguide structure can almost adiabatically convert the asymmetric near-field distribution of the active device into a symmetrical input or output near-field , effectively improve the coupling efficiency of active devices and optical fibers.

FIG. 4 is followed by secondary epitaxy, followed by p-type InP thin layer 14 , p-type InGaAsP selective chemical stop layer 15 , p-type InP cover layer 16 and p-type InGaAs contact layer 17 . In order to effectively control the depth of the etching modulator ridge structure 18, the etching needs to be carried out in two steps. First, a selective etching solution is used to etch the p-type InGaAsP selective chemical stop layer 15. The function of the selective chemical stop layer 15 is The selective etchant is blocked from further etching, and the depth of the modulator ridge structure 18 is controlled. The p-type indium phosphide thin layer 14 and the p-type indium phosphide capping layer 16 function as a current path and limit the refractive index of the multiple quantum wells 6 . The function of the p-type InGaAs contact layer 17 is to reduce the contact resistance between the metal and the device.

Figure 5. Schematic diagram of modulator region ridge etching. In order to effectively control the depth of the etched modulator ridge structure 18, the etching needs to be performed in two steps. First, a selective etching solution is used to etch to the p-type InGaAsP selective chemical stop layer. 15. Then use reactive ion etching to etch to the n-InP space layer 4, the etching conditions are: Ar:CH4:H2=5:18:45, 100W, 8 minutes and 30 seconds, and the etching depth is more than 500nm. etch to the n-InP space layer 4, because the N metal ohmic contact layer 22 must be made on the electrically conductive n-InP space layer 4, so that the device can work normally.

其面电阻值为50Ω/□，通过调节薄膜电阻的宽度，可以实现50、40、30、20Q等不同阻值的负载电阻，这样可以通过改变负载电阻阻值来优化调制带宽。同样采用带胶剥离(lift-off)方法在调制器脊结构18上制作厚度为1000的p型Au/Zn欧姆接触层21，在调制器脊结构18的两侧制作厚度2000

的N型Au/Ge/Ni欧姆接触层22。它们的作用是减小金属电极和材料的接触电阻。接下来在调制器脊结构18上作聚酰亚胺桥23，注意一定要露出调制器脊结构18上的p型Au/Zn欧姆接触层21，聚酰亚胺需要360℃高温固化50分钟，聚酰亚胺桥23的作用是为后来的钛金电极24提供电绝缘，同时缓和了调制器脊结构18的高度差，使得钛金电极24在脊台上平滑、连续。Figure 6 is a top view of P, N ohmic contacts, thin film resistors and polyimide bridges. First, the electroabsorption modulator material region 11 is wet-etched to the substrate 1 to form an insulating plane 20, which is used as a traveling wave electrode microwave The input and output parts of the transmission line are insulating media; then the tantalum nitride film resistor 19 is manufactured by using the lift-off method, and the thickness of the tantalum nitride is 1000

Its surface resistance value is 50Ω/□. By adjusting the width of the thin film resistor, load resistors with different resistance values such as 50, 40, 30, and 20Ω can be realized. In this way, the modulation bandwidth can be optimized by changing the resistance value of the load resistor. Also use the tape stripping (lift-off) method to make a thickness of 1000 on the modulator ridge structure 18 The p-type Au/Zn ohmic contact layer 21 is made on both sides of the modulator ridge structure 18 with a thickness of 2000

N-type Au/Ge/Ni ohmic contact layer 22. Their function is to reduce the contact resistance of metal electrodes and materials. Next, make a polyimide bridge 23 on the modulator ridge structure 18, and make sure to expose the p-type Au/Zn ohmic contact layer 21 on the modulator ridge structure 18. The polyimide needs to be cured at 360°C for 50 minutes. The function of the polyimide bridge 23 is to provide electrical insulation for the subsequent titanium gold electrode 24, and at the same time alleviate the height difference of the modulator ridge structure 18, so that the titanium gold electrode 24 is smooth and continuous on the ridge platform.

钛金电极17，然后刻蚀出行波电极图形。该电极在输入输出的部分设计的特征阻抗为50Ω，一端直接在绝缘平面20上，作为微波输入端，一端压在氮化钽薄膜电阻19上，形成负载电阻电路。Figure 7 is a top view of the device after the device is fabricated. The entire electrode pattern is shown in the figure, and the sputtering method is used to grow 5000

Titanium gold electrode 17, and then etch the traveling wave electrode pattern. The designed characteristic impedance of the input and output part of the electrode is 50Ω, one end is directly on the insulating plane 20 as a microwave input end, and the other end is pressed on the tantalum nitride film resistor 19 to form a load resistance circuit.

In summary, the preparation method of the present invention is:

1) On a substrate 1, an indium-phosphorus stress buffer layer 2, an n-1.2Q quaternary layer 3, an n-indium-phosphorus spacer layer 4, a lower confinement layer 5, and multiple quantum wells are sequentially grown on a substrate 1 by metal-organic vapor deposition. 6. Upper confinement layer 7 and defect diffusion layer 8 respectively;

2) Grow a layer of silicon oxide mask 9, etch away the silicon oxide mask in the template converter material region 10 by a wet method, form a silicon oxide pattern in the middle to protect the electroabsorption modulator material region 11, perform phosphorus ion implantation, and anneal , realize quantum well hybridization, make the material bandgap wavelength blue-shift, and finally remove the silicon oxide mask 9 and defect diffusion layer 8 with chemical reagents;

3) etching the tapered upper waveguide 12 and lower waveguide 13 structures of the speckle converter in the template converter material region 10;

4) Epitaxially p-type indium phosphide thin layer 14, p-type indium gallium arsenide phosphide selective chemical stop layer 15, p-type indium phosphide capping layer 16 and p-type indium gallium arsenide contact on the device by metal-organic vapor deposition method layer 17;

5) Etching the ridge structure 18 by using a method combining chemical wet etching and reactive ion dry etching;

6) Wet etch the substrate 1 in the material area 11 of the electroabsorption modulator to form an insulating plane 20, which is used as an insulating medium for the input and output part of the microwave transmission line of the traveling wave electrode;

7) On one side of the insulating plane of the substrate 1, a tantalum nitride thin film resistor 19 is produced by stripping with glue;

8) Fabricate a p-type metal ohmic contact 21 on the ridge structure 18 by stripping with glue;

9) On both sides of the ridge structure 18 on the material region 11 of the electroabsorption modulator, N-type metal ohmic contacts 22 are fabricated by stripping with glue;

10) making a polyimide bridge 23 on the electroabsorption modulator material region 11;

11) Fabricate a titanium-gold traveling-wave electrode structure 24 on the electroabsorption modulator material 11;

12) Thinning and cleavage to complete the fabrication of the entire device.

The advantages of the present invention are:

With the traveling-wave electrode structure, the modulation bandwidth of the electroabsorption modulator has no RC limitation, and a modulation bandwidth of 40 GHz or higher can be achieved. The electrode structure has been simulated and calculated to effectively reduce the microwave transmission loss and reflection loss of the device.

The two ends of the electroabsorption modulator integrate mode spot converters, which can almost adiabatically convert the asymmetric near-field distribution of the active device into a symmetrical input or output near-field, which can improve the coupling efficiency of the active device and the fiber , and can improve its offset tolerance, thereby effectively reducing the insertion loss of the device.

The device integrates the load resistor of the microwave output terminal into the device, and the resistance value can be changed by changing the strip width of the thin film resistor, so the modulation bandwidth of the modulator can be optimized by reducing the resistance value of the load resistor.

The fabrication of the device only needs two epitaxy, the process is simple and feasible, and the fabrication cost is low.

Claims (7)

1, a kind of method for making of going ripple electroabsorption modulator and module spot converter integrated device is characterized in that manufacturing process comprises the steps:

Step 1: the method that adopts metal organic chemical vapor deposition on the substrate grow successively indium phosphorus stress-buffer layer, n-1.2Q quaternary layer, n-indium phosphorus space layer, down respectively limiting layer, Multiple Quantum Well, on limiting layer, defective diffusion layer respectively;

Step 2: growth one deck silicon oxide masking film on the defective diffusion layer, fall the silicon oxide masking film in template converter material district with wet etching, the centre forms monox figure protection electroabsorption modulator material sections, carrying out phosphonium ion injects, annealing, realize quantum well mixing, make the material band gap wavelength blue shift, remove silicon oxide masking film and defective diffusion layer with chemical reagent at last;

Step 3: waveguide and following waveguiding structure in the taper of template converter material district etching spot-size converter;

Step 4: extension p type indium phosphide thin layer, p type InGaAsP select chemistry to stop layer, p type indium phosphide cap rock and p type indium gallium arsenic contact layer to the method for employing metal organic chemical vapor deposition successively on device;

Step 5: the method that employing wet chemical and reactive ion dry etching combine is at electroabsorption modulator material sections place etching ridge structure;

Step 6: adopt wet etching to substrate in the electroabsorption modulator material sections, form the insulation plane, as the input of traveling wave electrode microwave transmission line, output insulating medium;

Step 7: the method that adopts band glue to peel off on a side on the insulation plane of substrate is made tantalum nitride membrane resistance;

Step 8: the method that adopts band glue to peel off on ridge structure is made p type metal Ohmic contact;

Step 9: the method that the both sides of the ridge structure on the electroabsorption modulator material sections adopt band glue to peel off is made N type metal Ohmic contact;

Step 10: on the electroabsorption modulator material sections, make the polyimide bridge;

Step 11: on the electroabsorption modulator material sections, make titanium traveling wave electrode structure;

Step 12: the attenuate cleavage, finish the making of entire device.

2, the method for making of traveling wave electrode electro-absorption modulator according to claim 1 and module spot converter integrated device is characterized in that, wherein said substrate is the semi-insulating inp substrate.

3, the method for making of traveling wave electrode electro-absorption modulator according to claim 1 and module spot converter integrated device is characterized in that, the thickness of wherein said i-indium phosphorus defective diffusion layer is 200nm.

4, the method for making of traveling wave electrode electro-absorption modulator according to claim 1 and module spot converter integrated device is characterized in that, the material of wherein said Multiple Quantum Well is an InGaAsP.

5, the method for making of traveling wave electrode electro-absorption modulator according to claim 1 and module spot converter integrated device, it is characterized in that, waveguide is the method that adopts the reactive ion dry etching in the wherein said taper, and the width of waveguide reduces to 0 μ m from 3 μ m linearities in this taper; The method of wet etching is adopted in following waveguide, and its width is 6 μ m.

6, the method for making of traveling wave electrode electro-absorption modulator according to claim 1 and module spot converter integrated device, it is characterized in that, wherein said tantalum nitride membrane resistance, its face resistance value is 50 Ω/, by regulating the width of sheet resistance, can realize the pull-up resistor of 50,40,30,20 ohm of different resistances.

7, the method for making of traveling wave electrode electro-absorption modulator according to claim 1 and module spot converter integrated device is characterized in that, the material of wherein said defective diffusion layer is the i-indium phosphide.

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