阅读说明：本技术 一种防止湿法氧化时过度氧化的垂直腔面发射激光器的制作方法 (Manufacturing method of vertical cavity surface emitting laser for preventing excessive oxidation during wet oxidation ) 是由 李志虎 于军 邓桃 张新 徐现刚 于 2019-03-21 设计创作，主要内容包括：本发明涉及一种防止湿法氧化时过度氧化的垂直腔面发射激光器的制作方法,通过限制层孔道制作,在高温氧化时制作的限制层金属能够在很大程度上防止水蒸汽的过度氧化,本发明中通过限制层孔道制作可以比较有效的阻止过度氧化,在湿法氧化时只需要在原先测算平均氧化速率的基础上继续增加氧化时间,可以完全保证氧化的完成而又不会过度氧化,从而达到我们需要的孔径大小,实际上该种工艺将需要的氧化通道提前制作出来。(The invention relates to a method for manufacturing a vertical cavity surface emitting laser for preventing excessive oxidation during wet oxidation, which can prevent excessive oxidation of water vapor to a great extent by manufacturing limiting layer pore passages, wherein limiting layer metal manufactured during high-temperature oxidation can be manufactured by the limiting layer pore passages.)

1. A method for manufacturing a vertical cavity surface emitting laser for preventing excessive oxidation during wet oxidation is characterized by comprising the following steps:

(1) manufacturing a table top; the mesa after fabrication comprises a wafer with an epitaxial layer, a first SiO₂A film layer and a pore channel, wherein the first SiO is grown on the surface of the wafer with the epitaxial layer₂A film layer, the pore passage penetrates the first SiO downwards through the surface of the table-board₂The film layer extends into the wafer of the epitaxial layer;

further preferably, in the step (1), the first SiO₂The thickness of the film layer is

(2) Manufacturing a limiting layer pore channel; the method comprises the following steps:

A. growing second SiO on the surface of the wafer finished in the step (1)₂A film layer;

B. using photoresist to make a mask pattern, removing the photoresist in the limiting layer region to be made, and etching off the second SiO in the limiting layer region to be made₂Film layer, the first SiO₂A film layer;

C. etching a limiting layer pore channel at a limiting layer area to be manufactured;

preferably, in the step C, an ICP dry etching method is used to etch the limiting layer pore channel;

D. c, manufacturing a layer of metal on the surface of the wafer finished in the step C;

more preferably, in the step D, a layer of metal is formed on the surface of the wafer by a sputtering method or a vapor deposition method;

E. d, plating a metal layer on the surface of the wafer finished in the step D until the metal layer is filled in the pore canal of the limiting layer;

preferably, in the step E, a metal layer is plated on the surface of the wafer completed in the step D by using an electroless plating method;

F. using photoresist to make mask pattern, protecting the region of the limiting layer pore canal, and making the metal layer, metal and second SiO in other regions₂Film layer, first SiO₂The film layers are sequentially corroded;

(3) oxidizing and diffusing; carrying out high-temperature oxidation on the wafer finished in the step (2), and continuing to carry out high-temperature oxidation for 20-50% of T when the wafer reaches the scale of the high-temperature oxidation according to the average rate measured and calculated during the high-temperature oxidation, wherein T is the time taken for reaching the scale of the high-temperature oxidation calculated according to the average rate measured and calculated;

(4) manufacturing an isolation layer;

further preferably, the thickness of the isolation layer is

(5) And (5) manufacturing an electrode.

2. The method as claimed in claim 1, wherein in step C, the hole diameter of the confining layer channel is 2-4 μm.

3. The method according to claim 1, wherein said step (3) of oxidizing and diffusing comprises: performing high-temperature oxidation in an oxidation furnace, wherein saturated steam is used for the high-temperature oxidation, nitrogen is introduced for the high-temperature oxidation, the nitrogen introduction rate is 2-10L/min, the temperature in the oxidation furnace is 400-450 ℃, the high-temperature oxidation time is 30-90min, and the volume of the oxidation furnace is 50-100L, so that the nitrogen is ensured to fill the whole oxidation furnace cavity within 25-50 min.

4. The method as claimed in claim 1, wherein the metal is gold, gold beryllium, platinum or nickel, and the thickness of the metal is set as

5. The method for fabricating a vertical cavity surface emitting laser according to claim 1, wherein said step (1) of fabricating a mesa comprises:

G. growing a first SiO on the surface of a wafer with an epitaxial layer₂A film layer;

H. using photoresist to make mask pattern to protect the region of the pore channel to be made, removing photoresist from other region and making the first SiO₂Etching off the film layer;

I. and D, etching the wafer finished in the step H by using an ICP (inductively coupled plasma) dry etching method to etch the pore channel, and removing the photoresist.

6. The method as claimed in claim 5, wherein in step H, the photoresist has a thickness of

7. The method as claimed in claim 5, wherein in step I, the depth of the hole is greater than the thickness of the confinement layer.

8. The method for fabricating a vertical cavity surface emitting laser according to claim 1, wherein said step (4) of fabricating an isolation layer comprises:

J. growing third SiO on the surface of the wafer finished in the step (3)₂A film layer;

K. manufacturing a mask pattern by using photoresist;

and L, etching an electrode area to be manufactured by using an ICP (inductively coupled plasma) dry etching method.

9. The method for manufacturing a vertical cavity surface emitting laser capable of preventing excessive oxidation during wet oxidation according to claim 1, wherein the step (5) of manufacturing an electrode comprises:

m, manufacturing a P-surface electrode on the P surface of the wafer finished in the step (3);

and N, thinning the N surface of the wafer finished in the step M, and manufacturing an N-surface electrode to obtain the wafer.

10. The method for fabricating a vertical cavity surface emitting laser according to any of claims 1-9, wherein said first SiO is formed on a surface of said substrate₂Film layer, the second SiO₂Film layer, the third SiO₂The material of the film layer is SiO₂The SiO2 is at the thermal evaporation temperatureIs prepared by thermal evaporation at the temperature of 100 ℃ and 300 ℃.

Technical Field

The invention relates to a manufacturing method of a vertical cavity surface emitting laser for preventing excessive oxidation during wet oxidation, and belongs to the technical field of semiconductor processing.

Background

A vertical Cavity Surface Emitting laser (vcsel) is a semiconductor device developed based on gallium arsenide material. The Vcsel mainly has three parts of a laser working substance, a collapse source and an optical resonant cavity. The working substance is a substance which emits laser, but the working substance can not emit laser at any time, and the working substance needs to be excited by a pump source to form population inversion to emit laser, but the obtained laser has short service life, not too high intensity, many light wave modes and poor directivity. Therefore, it is necessary to amplify and oscillate in the Laser Cavity (Laser Cavity) through the resonant Cavity composed of the top Mirror (TopMirror) and the Bottom Mirror (Bottom Mirror), and output by the top Mirror, and the output light is concentrated in the portion without the Oxide layer (oxides) in the middle to output, so as to form the vertical Cavity surface Laser emission, thereby obtaining the stable, continuous, high-quality Laser with certain power.

The vertical cavity surface emitting laser has small active area volume and short cavity, the reflectivity of the cavity mirror reaches more than 99 percent during manufacturing, larger amplitude gain can be obtained, higher relaxation oscillation frequency is realized, and the vertical cavity surface emitting laser is widely applied to high-efficiency data transmission and optical fiber communication; the light emitting direction of Vcsel is vertical to the surface of the substrate, and the manufacturing of the epitaxial structure can be completed firstly. The following advantages are mainly achieved in conclusion: 1. the active area has small volume, and the work under the conditions of single vertical and horizontal direction and low threshold value is very easy to realize; 2. the high-speed modulation can be realized easily, and the optical fiber modulator can be applied to a long-distance and high-speed optical fiber communication system; 3. the exit light beam of Vcsel is circular, has a relatively small divergence angle, and can be easily coupled with optical fibers and other optical elements in a high-efficiency manner; 4. the laser is easy to realize a two-dimensional array, is applied to a parallel optical logic processing system, and can perform high-capacity and high-speed data processing; 5. the electro-optic conversion efficiency is higher and can be more than 50%, and the service life of the device is longer; 6. the semiconductor laser device can be used for detecting without packaging, products are screened, the product yield can be greatly improved, and the production cost is reduced.

The manufacturing process of Vcsel is simple, and is mainly realized through the following steps of 1, manufacturing a table top; 2. oxidizing and diffusing; 3. manufacturing an isolation layer; 4. manufacturing an electrode; 5. and thinning the wafer and cutting into single devices. As described above, one of the most important steps is to complete the oxidation diffusion, form oxide group faults, and limit the lateral diffusion of current. Currently, the most common process of oxidative diffusion is diffusion by wet oxygen, i.e. saturated water vapor reacts with a highly doped metal layer (typically aluminum metal) to form an insulating oxide to limit the lateral spread of current, thereby forming an upper and lower current path. The most important thing of the existing wet oxidation process is to control the oxidation rate, namely the oxidation degree, the oxidation area can not be monitored in time during oxidation, a general oxidation rate is obtained by measuring and calculating the rate of saturated water vapor and the temperature during oxidation, the oxidation degree is controlled by measuring and calculating the average oxidation rate and adjusting the temperature of the whole process, but the required oxidation size is difficult to be completed just due to the unstable temperature and the fluctuation of the reaction rate between the water vapor and the doped metal layer, the limitation effect can not be achieved when the oxidation is insufficient, the quality of the period is directly influenced by too little light passing through the oxidation, and the step generates more defective products.

Chinese patent document CN104882787A (201510300471.9) proposes a surface plasma modulated flip-chip Vcsel laser and its manufacturing method, comprising the following steps: (1) preparing an epitaxial wafer; (2) preparing a table board; (3) wet oxidation; (4) growing SiO2 on the P surface; (5) manufacturing an isolation window; (6) manufacturing a P-surface electrode; (7) thinning the N surface; (8) growing SiO2 on the N surface; (9) etching the SiO2 on the N surface; (10) carrying out overlay and metal sputtering on the N surface; (11) manufacturing a tube core; (12) preparing a nano structure; (13) and (6) testing. The invention mainly supplements the blank of the surface plasma modulation vertical cavity surface laser in the aspect of inversion, so that the full wave band can realize the plasma modulation of a micro-nano structure, but the oxidation hole manufactured by wet oxidation is directly oxidized by a conventional method, and the phenomenon of difficult control of the oxidation degree exists.

Chinese patent document CN1851992A (200610044192.1) proposes a method of preventing the vertical cavity surface emitting semiconductor laser from cracking at the time of wet oxidation. The cracking caused by the over-fast temperature change is prevented mainly by controlling the temperature in different stages during wet oxidation, the abnormal rate of the cracking is reduced to a certain extent by the oxidation completed by the method, but no better solution is provided for the oxidation degree, and particularly, the proper oxidation is difficult to ensure due to the larger fluctuation of the oxidation rate of the oxidation due to the multiple adjustment of the temperature.

In summary, it is necessary to develop a method for ensuring the wet oxidation effectively, so that the oxidation degree of the wet oxidation method is just up to the limited pore diameter required by the people, and the oxidation degree is easy to control.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a manufacturing method of a vertical cavity surface emitting laser for preventing excessive oxidation during wet oxidation;

interpretation of terms:

1. high temperature oxidation refers to a metal corrosion caused by the reaction of a metal material with oxygen at high temperature to form an oxide.

2. Thermal evaporation refers to a process of placing a substrate or a workpiece to be coated in a vacuum chamber, heating a coating material to evaporate and gasify the coating material to deposit a film or a coating on the surface of the substrate or the workpiece.

The technical scheme of the invention is as follows:

a manufacturing method of a vertical cavity surface emitting laser for preventing excessive oxidation in wet oxidation comprises the following steps:

(1) manufacturing a table top; the mesa after fabrication comprises a wafer with an epitaxial layer, a first SiO₂A film layer and a pore channel, wherein the first SiO is grown on the surface of the wafer with the epitaxial layer₂A film layer, the pore passage penetrates the first SiO downwards through the surface of the table-board₂The film layer extends into the wafer of the epitaxial layer;

further preferably, in the step (1), the first SiO₂The thickness of the film layer is 3000-

(2) Manufacturing a limiting layer pore channel; the method comprises the following steps:

A、growing second SiO on the surface of the wafer finished in the step (1)₂A film layer;

B. using photoresist to make a mask pattern, removing the photoresist in the limiting layer region to be made, and etching off the second SiO in the limiting layer region to be made₂Film layer, the first SiO₂A film layer;

C. etching a limiting layer pore channel at a limiting layer area to be manufactured;

preferably, in the step C, the limiting layer pore channel is etched by using an ICP dry etching method.

D. C, manufacturing a layer of thin metal on the surface of the wafer finished in the step C;

further preferably, the metal is gold, gold beryllium, platinum or nickel, and the thickness of the metal is 10-100

In the step D, a layer of metal is preferably formed on the surface of the wafer by a sputtering method or a vapor deposition method.

E. D, plating a metal layer on the surface of the wafer finished in the step D until the metal layer is filled in the pore canal of the limiting layer;

further preferably, in the step E, a metal layer is plated on the surface of the wafer completed in the step D by using an electroless plating method.

F. Using photoresist to make mask pattern, protecting the region of the limiting layer pore canal, and making the metal layer, metal and second SiO in other regions₂Film layer, first SiO₂The film layers are sequentially corroded;

(3) oxidizing and diffusing; carrying out high-temperature oxidation on the wafer finished in the step (2), and continuing to carry out high-temperature oxidation for 20-50% of T when the wafer reaches the scale of the high-temperature oxidation according to the average rate measured and calculated during the high-temperature oxidation, wherein T is the time taken for reaching the scale of the high-temperature oxidation calculated according to the average rate measured and calculated;

the oxidized scale diameter can be seen through a microscope of an infrared light source after high-temperature oxidation, the average oxidation rate can be calculated through the oxidation time and the scale diameter, the oxidation degree needs to be controlled through the average rate in the traditional process, and the limited layer pore passage does not have the problem of peroxidation, so that the oxidized scale diameter can float up by 20-50 percent on the basis of the time calculated according to the average rate to achieve the purpose of thorough oxidation;

the metal at the pore diameter of the limiting layer manufactured in the high-temperature oxidation process can prevent the excessive oxidation of water vapor to a great extent by manufacturing the pore passage of the limiting layer, and the oxidation can be completely finished without excessive oxidation only by continuously increasing the oxidation time on the basis of originally measuring and calculating the average oxidation rate in the wet oxidation process, so that the pore diameter required by people is achieved, and actually, the required oxidation channel is manufactured in advance by the process.

(4) Manufacturing an isolation layer;

further preferably, the thickness of the isolation layer is 1000-

The selection of the thickness can ensure the integrity of the isolation layer and also can give consideration to the efficiency. If the spacer is too thin, it is susceptible to damage during the entire process, and if the spacer is too thick, the fabrication efficiency is too low.

(5) And (5) manufacturing an electrode.

Preferably, in step C, the pore diameter of the limiting layer pore channel is 2 to 4 μm.

The selection of the pore size of the pore passage of the limiting layer is important, the pore size is too large, the quality of the whole device is seriously influenced, metal with too small pore size cannot be completely filled, the limiting effect of limiting the oxidation effect is not achieved, and partial regional peroxidation is easy to occur; the current transmission is greatly influenced after metal is manufactured above the range which can seriously damage the whole epitaxial layer structure. Experimental research shows that the aperture size is between 2 and 4 mu m and is a proper value, so that the quality of the device is not greatly influenced, and the manufacture of the aperture metal filling of the limiting layer is not influenced.

According to a preferred embodiment of the present invention, in the step (3), the oxidation diffusion includes: performing high-temperature oxidation in an oxidation furnace, wherein saturated steam is used for the high-temperature oxidation, nitrogen is introduced for the high-temperature oxidation, the nitrogen introduction rate is 2-10L/min, the temperature in the oxidation furnace is 400-450 ℃, the high-temperature oxidation time is 30-90min, and the volume of the oxidation furnace is 50-100L, so that the nitrogen is ensured to fill the whole oxidation furnace cavity within 25-50 min. The oxidation process is carried out in a saturated vapor pressure atmosphere to ensure uniformity of oxidation.

According to a preferred embodiment of the present invention, the step (1) of fabricating the table top comprises:

G. growing a first SiO on the surface of a wafer with an epitaxial layer₂A film layer;

H. using photoresist to make mask pattern to protect the region of the pore channel to be made, removing photoresist from other region and making the first SiO₂Etching off the film layer;

preferably, in the step H, the thickness of the photoresist is 10000-

I. And D, etching the wafer finished in the step H by using an ICP (inductively coupled plasma) dry etching method to etch the pore channel, and removing the photoresist.

Further preferably, in the step I, the depth of the pore channel is greater than the thickness of the limiting layer; the limiting channel depth must be greater than this to be limiting.

According to a preferred embodiment of the present invention, the step (4) of forming an isolation layer for isolating injection of current into the other regions except the electrode region includes:

J. growing third SiO on the surface of the wafer finished in the step (3)₂A film layer;

K. manufacturing a mask pattern by using photoresist;

and L, etching an electrode area to be manufactured by using an ICP (inductively coupled plasma) dry etching method.

According to a preferred embodiment of the present invention, the step (5) of fabricating an electrode includes:

m, manufacturing a P-surface electrode on the P surface of the wafer finished in the step (3);

and N, thinning the N surface of the wafer finished in the step M, and manufacturing an N-surface electrode to obtain the wafer.

According to a preferred embodiment of the invention, the first SiO₂Film layer, the second SiO₂Film layer, the third SiO₂The material of the film layer is SiO₂Said SiO₂Prepared by thermal evaporation under the temperature condition that the thermal evaporation temperature is 100-300 ℃. SiO produced in this temperature range₂Relatively dense and good adhesion.

The invention has the following beneficial effects:

1. in the invention, the limiting layer metal manufactured in high-temperature oxidation can prevent the excessive oxidation of water vapor to a great extent by manufacturing the limiting layer pore passage, the temperature of the whole process is adjusted by measuring and calculating the average oxidation rate in the traditional process to control the oxidation degree, but the required oxidation size is difficult to be just finished due to the unstable temperature and the fluctuation of the reaction rate between the water vapor and the doped metal layer, the required limiting effect cannot be achieved when the oxidation is insufficient, and the quality during the period of direct influence of too little passing of excessive oxidation light is realized. In the invention, the excessive oxidation can be effectively prevented by manufacturing the limiting layer pore canal, and the oxidation can be completely finished without excessive oxidation only by continuously increasing the oxidation time on the basis of originally measuring and calculating the average oxidation rate during wet oxidation, so that the pore size required by people is achieved, and actually, the required oxidation channel is manufactured in advance by the process.

2. In the invention, the selection of the pore size of the limiting layer pore canal is important, the pore size is too large to seriously affect the quality of the whole device, the metal with too small pore size can not be completely filled to achieve the effect of limiting oxidation, and experimental research shows that the pore size between 2 and 4 mu m is a proper numerical value, which can not greatly affect the quality of the device and can not affect the manufacture of the pore size metal filling of the limiting layer.

3. The limiting layer aperture process is complex in manufacturing, simple in principle and large in improvement of device quality, loss in cost and efficiency caused by manufacturing of the limiting aperture can be made up, and the process method is suitable for oxidation diffusion processes of all lasers and suitable for large-scale production.

Drawings

FIG. 1 is a schematic view of a completed mesa structure;

FIG. 2 is a schematic structural view after completion of step B;

FIG. 3 is a schematic structural view after completion of step (2);

FIG. 4 is a schematic structural diagram after a metal layer is grown;

FIG. 5 is a schematic structural diagram of a grown metal layer after etching of excess metal;

FIG. 6 is a schematic diagram of the structure after oxidation and diffusion;

FIG. 7 is a schematic view of a structure after the isolation layer is formed;

fig. 8 is a schematic structural diagram after the N-face electrode is thinned and grown.

1. Wafer with epitaxial layer, 2, first SiO₂Film layer, 3, pore channel, 4, second SiO₂Film layer, 5 limiting layer pore canal, 6 metal layer, 7 and third SiO₂Film layer, 8, P-face electrode, 9, N-face electrode, 10 and limiting layer.

Detailed Description

The invention is further defined in the following, but not limited to, the figures and examples in the description.