CN112397999A

CN112397999A - Semiconductor laser device for plasma diagnosis and preparation method thereof

Info

Publication number: CN112397999A
Application number: CN202011293444.0A
Authority: CN
Inventors: 毛森; 王中和; 陆凯凯; 焦英豪
Original assignee: Guangdong Hongxin Technology Co ltd
Current assignee: Guangdong Hongxin Technology Co ltd
Priority date: 2020-11-18
Filing date: 2020-11-18
Publication date: 2021-02-23

Abstract

The invention provides a semiconductor laser device for plasma diagnosis and a preparation method thereof, wherein the semiconductor laser device comprises a first electrode, a second electrode, a substrate, a first limiting layer, a first waveguide layer, an active region, a second waveguide layer, a second limiting layer, an ohmic contact layer and an X-ray gold transmission grating layer, wherein the substrate is arranged between the first electrode and the second electrode and sequentially arranged from the first electrode to the second electrode, and the ohmic contact layer is in contact with the second limiting layer. According to the invention, the X-ray gold transmission grating is arranged between the P-face electrode and the P-type limiting layer, so that the high resolution of the semiconductor laser is improved and higher diffraction efficiency is obtained. Can meet the requirement of manufacturing the gold transmission grating with large groove depth, steep side wall and smoothness.

Description

Semiconductor laser device for plasma diagnosis and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductor photoelectricity, in particular to a semiconductor laser device for plasma diagnosis and a preparation method thereof.

Background

With the development of laser technology, a new application subject, namely laser medicine, is gradually formed, and the unique advantages of laser are achieved, so that many problems which cannot be solved in basic research and clinical application of traditional medicine are solved, and the attention of medical circles at home and abroad is aroused. Semiconductor lasers (DL) are particularly suitable for the manufacture of medical devices due to their small size, light weight, long lifetime, low power consumption, wide wavelength coverage, and the like. In addition, semiconductor lasers are widely used in important fields such as optical fiber communication, optical disc access, spectral analysis, and optical information processing.

The gold transmission grating has simple structure, large solid angle and wide spectrum range, can be conveniently combined with a spatial resolution instrument at the same time, and is widely applied to the fields of laser inertial confinement nuclear fusion plasma diagnosis, X-ray celestial body physics and the like. At present, the use wave band of the gold transmission grating in the fields of plasma diagnosis and astrophysics is required to reach sub-kilo electron volts and even higher energy, and in order to realize high-energy X-ray energy spectrum resolution and obtain higher diffraction efficiency, the groove depth (the height of a gold grating line) is required to be increased to more than 500nm on the basis of improving the linear density of the grating, and the straightness and smoothness of the side wall of the grating line are required to be ensured.

Moreover, the power and the service life of the DL are important indexes for measuring the performance of the DL, and the current cavity surface optical disaster phenomenon is a key factor for limiting the power and the service life of the high-power DL. In order to prevent the occurrence of cavity surface optical catastrophe, the techniques mainly used for resisting cavity surface optical catastrophe at present include the following types:

firstly, a cavity surface passivation treatment technology.

Secondly, a cavity surface passivation film technology.

And thirdly, non-radiation absorption window technology. The technology is to prepare a layer of wide-bandgap semiconductor material by secondary epitaxial growth or doping diffusion on the cavity surface of the laser, and aims to reduce the radiation absorption of photons in the region and reduce the temperature of the cavity surface.

However, the cleaning step is required before the passivation film is prepared, which may cause some damage to the cavity surface; non-radiation absorbing window technology may additionally produce semiconductor materials.

Disclosure of Invention

In view of the above, the present invention is directed to a semiconductor laser device for plasma diagnosis and a method for manufacturing the same, which aims to improve the high resolution and diffraction efficiency of the semiconductor laser device.

In view of the above, the present invention provides a semiconductor laser device for plasma diagnosis, which includes a first electrode, a second electrode, a substrate disposed between the first electrode and the second electrode and arranged in sequence from the first electrode to the second electrode, a first confinement layer, a first waveguide layer, an active region, a second waveguide layer, a second confinement layer, an ohmic contact layer, and an X-ray gold transmission grating layer in contact with the second confinement layer.

The first electrode is an N-type electrode, the first limiting layer is an N-type limiting layer, the first waveguide layer is an N-type waveguide layer, the second electrode is a P-type electrode, the second limiting layer is a P-type limiting layer, and the second waveguide layer is a P-type waveguide layer.

The N-type waveguide layer and the P-type waveguide layer are made of AlxGa1-xAs materials, and the thickness ratio of the N-type waveguide layer to the P-type waveguide layer is 3: 1.

the P-type limiting layer is made of AlxGa 1-xAs.

The active region is a quantum well active region or a quantum dot active region.

And two opposite side surfaces of the semiconductor laser device for plasma diagnosis are respectively provided with an antireflection film and a high-reflection film.

The preparation method of the semiconductor laser device for plasma diagnosis comprises the following steps:

the method comprises the following steps that firstly, an N-type limiting layer, an N-type waveguide layer, an active region, a P-type waveguide layer, a P-type limiting layer and an ohmic contact layer are epitaxially prepared on a substrate in sequence;

etching the middle part of the ohmic contact layer to form a P-type limiting layer so as to form a grating groove;

step three, preparing an X-ray gold transmission grating according to the size of the grating groove;

step four, installing the X-ray gold transmission grating into a grating groove;

preparing a P-type electrode on the epitaxial wafer;

and step seven, thinning and polishing the substrate to prepare the N-type electrode.

The preparation method of the X-ray gold transmission grating comprises the following steps:

s1, taking an SOI silicon chip as a substrate, sequentially plating a gold film and a chromium film on the upper surface of the substrate, and plating a silicon nitride film on the lower surface of the substrate to form a substrate;

s2, respectively coating photoresist on the upper surface and the lower surface of the substrate, manufacturing a photoresist mask of a supporting structure on the upper surface of the substrate by utilizing ultraviolet lithography, and manufacturing a photoresist mask of a grating outer frame on the lower surface of the substrate;

s3, respectively removing the silicon nitride film and the chromium film in the non-mask areas on the upper surface and the lower surface of the substrate;

s4, removing the photoresist on the upper surface and the lower surface of the substrate;

s5, coating an anti-reflection film and a photoresist on the upper surface of the substrate in sequence;

s6, making a photoresist grating mask by holographic lithography, wherein the extension direction of the grating mask is vertical to the extension direction of the grating support structure;

s7, transferring the photoresist grating mask pattern into the antireflection film through reactive ion etching;

s8, transferring the photoresist grating mask pattern into the gold film through ion beam etching;

s9, removing the residual photoresist, antireflective film and chromium film on the upper surface of the substrate, and coating a protective adhesive on the lower surface;

s10, putting the substrate into etching liquid consisting of hydrofluoric acid and oxidant for metal catalytic etching;

s11, placing the substrate in a gold plating electrolyte, and electroplating and depositing gold on the upper surface;

s12, removing the protective glue on the lower surface of the substrate, and coating the protective glue on the upper surface of the substrate;

s13, etching the monocrystalline silicon in the non-mask area of the bottom layer;

s14, removing the protective glue on the upper surface;

s15, etching the top monocrystalline silicon;

and S16, removing the silicon nitride and the middle SiO2 layer in the window, cleaning and drying to obtain the X-ray gold transmission grating.

The preparation method further comprises the steps of after edge lines of the epitaxial wafer with the electrodes are cleaved, depositing a highly compact passivation layer on the front cavity surface and the rear cavity surface of the semiconductor laser through an atomic layer deposition method, then depositing an antireflection film on the passivation layer on the front cavity surface, and depositing a high reflection film on the passivation layer on the rear cavity surface.

And the inside is cleaved in ultra-high vacuum. And depositing a passivation film on the laser cavity surface in vacuum, and then depositing a highly compact passivation layer. The first layer of passivation film plays a role in protecting the cavity surface of the laser from contacting air when the cavity surface of the laser is taken out of the vacuum cleaving machine and enters the atmospheric environment, and the cavity surface is prevented from being oxidized. The combination of this technique with the facet passivation film technique further improves the facet anti-facet optical catastrophic ability. The semiconductor laser chip is cleaved in ultrahigh vacuum and then the passivation film is deposited in situ, so that the oxygen in the air can be prevented from oxidizing and damaging the cavity surface, and the cleaning step before the preparation of the passivation film can be omitted, so that the damage of the cleaning step to the cavity surface is prevented, and the integrity of the cavity surface structure is protected to the maximum extent.

The invention has the beneficial effects that:

1. according to the invention, the X-ray gold transmission grating is arranged between the P-face electrode and the P-type limiting layer, so that the high resolution of the semiconductor laser is improved and higher diffraction efficiency is obtained. Can meet the requirement of manufacturing the gold transmission grating with large groove depth, steep side wall and smoothness. The semiconductor laser with the transmission grating layer can improve the reliability in medical diagnosis and is more beneficial for doctors to find out treatment means in a targeted manner.

2. The arrangement of the high-reflection film and the antireflection film gives consideration to both the surface light-emitting efficiency and the cavity surface light-emitting efficiency. The antireflection film is evaporated on the front cavity surface, and the high-reflection film is evaporated on the rear cavity surface, so that the light emitting efficiency of the cavity surface is improved, and the loss threshold of the cavity surface is reduced.

3. According to the invention, the atomic layer deposition method is adopted to deposit a layer of highly-compact passivation layer on the front cavity surface and the back cavity surface, and the passivation layer is highly-compact, so that the highly-compact passivation layer can more effectively prevent other atoms from entering the cavity surface material through the passivation layer compared with the existing passivation method, thereby preventing optical catastrophe of the cavity surface, improving the damage threshold value of the cavity surface, improving the power of the semiconductor laser and prolonging the service life of the semiconductor laser.

Drawings

In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only one or more embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic side cross-sectional view of the present invention;

FIG. 2 is a cross-sectional view of a substrate coated with Au and Cr films on the upper surface and a silicon nitride film on the lower surface according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view of a photoresist mask with a support structure formed on the upper surface and a photoresist mask with a grating outer frame formed on the lower surface according to an embodiment of the present invention;

FIG. 4 is a cross-sectional view of a structure in which a silicon nitride film is etched on a lower surface and a Cr film is etched on an upper surface according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view of a structure after photoresist removal according to an embodiment of the present invention;

FIG. 6 is a cross-sectional view of a structure in which an antireflective film and a photoresist are sequentially coated on an upper surface according to an embodiment of the present invention;

FIG. 7 is a cross-sectional view of a structure of a photoresist grating mask fabricated by holographic lithography according to an embodiment of the present invention;

FIG. 8 is a cross-sectional view of a structure after transferring a photoresist grating mask to an antireflective film according to an embodiment of the invention;

FIG. 9 is a cross-sectional view of the structure after transferring a photoresist grating mask to a gold film according to an embodiment of the present invention;

FIG. 10 is a cross-sectional view of the structure with the photoresist, antireflective film and Cr film removed from the top surface according to the embodiment of the invention;

FIG. 11 is a cross-sectional view of a structure of applying a protective adhesive to a lower surface according to an embodiment of the present invention;

FIG. 12 is a cross-sectional view of a structure after a top surface metal catalytic etching process according to an embodiment of the present invention;

FIG. 13 is a cross-sectional view of a structure after gold is electroplated on the top surface according to an embodiment of the present invention;

fig. 14 is a cross-sectional view of the structure provided in the embodiment of the present invention, after the protective adhesive is removed from the lower surface and the protective adhesive is coated on the upper surface;

FIG. 15 is a cross-sectional view of the structure after etching of the bottom layer of monocrystalline silicon provided in an embodiment of the invention;

FIG. 16 is a cross-sectional view of the structure with the protective glue removed from the top surface according to the embodiment of the present invention;

FIG. 17 is a cross-sectional view of the structure after etching of the top layer of monocrystalline silicon on the upper surface according to an embodiment of the invention;

fig. 18 is a structural cross-sectional view of an X-ray gold transmission grating obtained after removing silicon nitride and the intermediate SiO2 layer in the window according to an embodiment of the present invention.

Labeled as:

1. top layer monocrystalline silicon; 2. an intermediate layer of SiO 2; 3. bottom layer monocrystalline silicon; 4. a SiN film; 5. an Au film; 6. a Cr film; 7. photoresist; 8. a antireflection film; 9. protective glue; 10. an X-ray gold transmission grating layer; 11. a first electrode; 12. a second electrode; 13. a substrate; 14. a first confinement layer; 15. a first waveguide layer; 16. an active region; 17. a second waveguide layer; 18. a second confinement layer; 19. and an ohmic contact layer.

Detailed Description

To make the objects, technical solutions and advantages of the present disclosure more apparent, the present disclosure is further described in detail below with reference to specific embodiments.

It should be noted that technical terms or scientific terms used in the embodiments of the present specification should have a general meaning as understood by those having ordinary skill in the art to which the present disclosure belongs, unless otherwise defined. The use of "first," "second," and similar terms in the embodiments of the specification is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

As shown in fig. 1, a semiconductor laser device for plasma diagnosis includes a first electrode 11, a second electrode 12, a substrate 13 provided between the first electrode 11 and the second electrode 12 and arranged in this order from the first electrode 11 toward the second electrode 12, a first confinement layer 14, a first waveguide layer 15, an active region 16, a second waveguide layer 17, a second confinement layer 18, an ohmic contact layer 19, and an X-ray gold transmission grating layer 10 in which the ohmic contact layer 19 is in contact with the second confinement layer 18. An X-ray gold transmission grating is arranged between the P-face electrode and the P-type limiting layer, so that the high resolution of the semiconductor laser is improved, and the higher diffraction efficiency is obtained. Can meet the requirement of manufacturing the gold transmission grating with large groove depth, steep side wall and smoothness.

In this embodiment, the first electrode 11 is an N-type electrode, the first confinement layer 14 is an N-type confinement layer, the first waveguide layer 15 is an N-type waveguide layer, the second electrode 12 is a P-type electrode, the second confinement layer 18 is a P-type confinement layer, and the second waveguide layer 17 is a P-type waveguide layer.

Wherein the active region 16 is a quantum well active region or a quantum dot active region. This embodiment is illustrated with a quantum well active region. The quantum well active region is manufactured in the N-type waveguide layer and the P-type waveguide layer and is made of indium gallium arsenide materials.

In this embodiment, the substrate is an N-type gaas material with a thickness of about 300-.

The N-type waveguide layer and the P-type waveguide layer are made of AlxGa1-xAs materials, and the thickness ratio of the N-type waveguide layer to the P-type waveguide layer is 3: 1. the N-type waveguide layer and the P-type waveguide layer are different in thickness, so that the optical field distribution is changed, and the interaction probability of photons and the transmission grating is effectively improved.

The N-type limiting layer is manufactured on the substrate and is made of an N-type AlGaAs material, so that an optical field can be effectively limited. The P-type limiting layer is made of AlxGa 1-xAs. The P-type confinement layer is formed on the P-type waveguide layer.

Furthermore, two opposite side surfaces of the semiconductor laser device for plasma diagnosis are respectively provided with an antireflection film and a high-reflection film. The arrangement of the high-reflection film and the antireflection film gives consideration to both the surface light-emitting efficiency and the cavity surface light-emitting efficiency. The antireflection film is evaporated on the front cavity surface, and the high-reflection film is evaporated on the rear cavity surface, so that the light emitting efficiency of the cavity surface is improved, and the loss threshold of the cavity surface is reduced.

the method comprises the following steps that firstly, an N-type limiting layer, an N-type waveguide layer, an active region 16, a P-type waveguide layer, a P-type limiting layer and an ohmic contact layer 19 are epitaxially prepared on a substrate 13 in sequence; the N-type substrate is a gallium arsenic substrate with a (100) plane deviated from a <111> direction by 15 degrees of an N-type deviation angle. On one hand, the formation of a metastable state ordered structure in the growth process can be inhibited by selecting a (100) plane 15-degree N-type deflection angle gallium arsenic substrate deviating from the <111> direction; on the other hand, the doping concentration of P-type impurities in the limiting layer can be improved, the effective potential barrier of electrons is improved, the electron leakage of the active region is inhibited, and the preparation of a high-power semiconductor laser is facilitated.

Etching the middle part of the ohmic contact layer 19 to form a P-type limiting layer so as to form a grating groove;

preparing a P-type electrode on the epitaxial wafer;

and step seven, thinning and polishing the substrate 13 to prepare the N-type electrode. And preparing a P-type electrode and an N-type electrode on the epitaxial wafer, wherein the electrodes are electrode materials capable of forming good ohmic contact with gallium arsenic materials, the P-type electrode is prepared by adopting a sputtering method, and the N-type electrode is prepared by adopting an evaporation method.

s1, taking an SOI silicon chip as a substrate, sequentially plating a gold film and a chromium film on the upper surface of the substrate, and plating a silicon nitride film on the lower surface of the substrate to form a substrate; in the embodiment of the present invention, the top layer single crystal silicon may be the <110> crystal orientation, the <111> crystal orientation or the <100> crystal orientation, wherein the top layer single crystal silicon with the <100> crystal orientation is the best effect, and the bottom layer single crystal silicon may be the <110> crystal orientation or the <100> crystal orientation. The structural parameters of the SOI silicon wafer adopted in the embodiment of the invention are as follows: the top layer of monocrystalline silicon has a crystal orientation of <100> and a thickness of 2-10 microns; the thickness of the middle layer SiO2 is 1-2 microns; the bottom layer of monocrystalline silicon is in a <100> crystal orientation, the thickness of the monocrystalline silicon is 300-500 microns, and the thicknesses of the top layer of monocrystalline silicon, the middle layer of SiO2 and the bottom layer of monocrystalline silicon are designed based on the requirements of products. FIG. 2 is a cross-sectional view of a substrate with an Au film 5 and a Cr film 6 plated on the upper surface and a SiN film 4 (silicon nitride film) plated on the lower surface, according to an embodiment of the present invention, wherein the Au film is deposited by magnetron sputtering, ion beam sputtering, or electron beam evaporation, and the thickness of the Au film is 15nm to 30 nm; because the Cr film is easy to be stripped from the SOI silicon wafer under the action of the Cr removing liquid, the Cr film is used as an intermediate layer of a transfer grating supporting structure, the Cr film is plated by adopting an electron beam evaporation or ion beam sputtering method, the thickness of the Cr film must be larger than that of the catalytic metal so as to protect the catalytic metal under the Cr film from being etched, and experiments prove that the requirement can be met when the thickness is larger than 100 nm; the silicon nitride film and the monocrystalline silicon have similar structures, so that the silicon nitride film and the monocrystalline silicon have strong adhesive force, the silicon nitride film and the monocrystalline silicon do not fall off in the later ultrasonic cleaning process, and the silicon nitride does not react with the potassium hydroxide etching solution for windowing the lower surface of the silicon wafer, so that the silicon nitride film is used as a protective layer for manufacturing the grating outer frame structure, and can be plated by adopting a PECVD (plasma enhanced chemical vapor deposition) method, and the thickness is more than 40 nm.

S2, respectively coating photoresist 7 on the upper surface and the lower surface of the substrate, manufacturing a supporting structure photoresist 7 mask on the upper surface of the substrate by utilizing ultraviolet lithography, and manufacturing a grating outer frame photoresist 7 mask on the lower surface of the substrate; FIG. 3 is a structural cross-sectional view of a grating support structure mask made on the upper surface and a grating outer frame mask made on the lower surface, wherein the grating support structure mask is a line array, the period is preferably 10-20 micrometers, the line width is 2-3 micrometers, the grating outer frame mask image is an orthogonal grid, the width of the grid bars is 1-2 millimeters, and the interval of the grid bars is 4-6 millimeters.

The photoresist is a positive photoresist, such as AZ MIR-701, the coating thickness (500-1000) nm is preferred, the photoresist is coated by using a rotary coating method, and the thickness can be adjusted by adjusting the rotating speed and the proportion of a solvent in the photoresist according to the use instruction of the photoresist. The gluing process is as follows: coating the surface, and baking; then coating the lower surface, and then baking the glue. The baking condition can refer to the photoresist application instruction, and for the AZ MIR-701 photoresist, the single baking parameter is baking for 2 minutes at 90 ℃ of a hot table. The ultraviolet lithography uses a URE-2000/35 type ultraviolet lithography machine of photoelectric technology research institute of Chinese academy of sciences, and the specific process conditions can refer to the photoresist use instruction and the lithography machine use instruction. Because the selected positive photoresist is adopted, the pattern of the photoetching mask is consistent with the target pattern. The process of ultraviolet photoetching comprises the following steps: exposing the upper surface in a contact manner; lower surface contact exposure; and (6) developing.

S3, respectively removing the silicon nitride film and the chromium film in the non-mask areas on the upper surface and the lower surface of the substrate; FIG. 4 is a cross-sectional view of a structure in which a silicon nitride film is etched on a lower surface and a Cr film is etched on an upper surface according to an embodiment of the present invention; for the etching of the silicon nitride film, an ICP-98A type induction coupling plasma etching machine developed by microelectronics of Chinese academy of sciences is used, the etching depth of the silicon nitride film is controlled by controlling the flow rate of reaction gas, the power of an excitation power supply, the power of a bias power supply and the etching time, and a large number of experiments prove that for the silicon nitride film with the thickness of 40nm, the adopted etching conditions are as follows: reaction gas CF 4; the flow rate is 20sccm, the excitation power supply power is 300W, the bias power supply power is 75W, and the time is 90 s. And (3) etching the Cr film by using a Cr removing liquid wet method, wherein the Cr removing liquid is prepared by mixing cerium ammonium nitrate: glacial acetic acid: water is mixed according to the mass ratio of 20:3: 100. Since the etching is isotropic, the etching time cannot be too long, otherwise the lateral undercutting effect will cause the Cr mask lines to disappear. The specific etching time can be obtained by experiment.

S4, removing the photoresist 7 on the upper surface and the lower surface of the substrate; the photoresist on the upper surface and the lower surface is removed by acetone ultrasonic, and the structural cross-sectional view after the photoresist is removed is shown in fig. 5.

S5, coating an antireflective film 8 and a photoresist 7 on the upper surface of the substrate in sequence; fig. 6 is a cross-sectional view of a structure in which an antireflective film and a photoresist are sequentially coated on an upper surface according to an embodiment of the present invention, in order to reduce a standing wave effect in holographic exposure, before a photoresist 7 is coated, a layer of antireflective film 8 is coated on a prepared substrate, the antireflective film is selected from a series of Brewer Science, and a positive photoresist is selected from AZ MIR-701. The thickness of the antireflective film is about 150nm, and the thickness of the photoresist is about 300 nm. The specific process conditions can refer to the application specifications of the antireflective film and the photoresist.

S6, making a photoresist 7 grating mask by holographic lithography, wherein the extension direction of the grating mask is vertical to the extension direction of the grating support structure; fig. 7 is a cross-sectional view of a structure of a grating mask manufactured by holographic lithography according to an embodiment of the present invention, which is obtained by performing holographic exposure on an exposure light path of a laemon lens, developing the exposure light path to obtain a photoresist grating mask, wherein an extending direction of the support structure mask is parallel to an optical platform during exposure, and an extending direction of interference fringes that generate a pattern of the photoresist grating mask is perpendicular to the optical platform, so that the photoresist grating mask obtained by development is naturally perpendicular to the support structure, and the holographic lithography is a conventional process means, and detailed description of a specific operation process is omitted.

S7, transferring the grating mask pattern of the photoresist 7 into the antireflection film 8 through reactive ion etching; fig. 8 is a structural cross-sectional view of transferring a photoresist grating mask to an antireflective film according to an embodiment of the present invention, in which an ICP-98A type inductively coupled plasma etcher developed by microelectronics of the chinese academy of sciences is used, and the etching depth of the antireflective film is controlled by controlling the reaction gas flow, the excitation power, the bias power, and the etching time, and finally the photoresist grating mask pattern is transferred to the antireflective film to form the antireflective film 8 of the grating structure.

S8, transferring the photoresist 7 grating mask pattern into the gold film through ion beam etching; fig. 9 is a cross-sectional view of the structure after transferring the photoresist grating mask to the gold film according to the embodiment of the present invention, in which the photoresist grating mask pattern is transferred to the gold film by using the conventional ion beam etching.

S9, removing the residual photoresist 7, the antireflective film 8 and the chromium film on the upper surface of the substrate, and coating the protective glue 9 on the lower surface; FIG. 10 is a cross-sectional view of the structure after the photoresist, the antireflective film and the Cr film have been removed according to the embodiment of the present invention; in particular to

The photoresist and the antireflective coating (ARC) were removed by acetone sonication, and the Cr coating was removed by Cr removal liquid sonication. FIG. 11 is a cross-sectional view of a structure of the protective adhesive coated on the lower surface according to an embodiment of the present invention, wherein the protective adhesive 9 is made of the protective adhesive of Brewer Science. The specific process conditions of coating the Primer first and then coating can refer to the use instruction.

S10, putting the substrate into etching liquid consisting of hydrofluoric acid and oxidant for metal catalytic etching; fig. 12 is a cross-sectional view of the structure after the catalytic etching process of the upper surface metal provided by the present invention. The oxidant can be hydrogen peroxide, potassium permanganate or silver nitrate, the concentration and the etching temperature of each component of the specific etching solution can be obtained through a contrast experiment, the optimal target is to etch a grating structure with a smooth and steep side wall, the hydrogen peroxide is taken as the oxidant for example, the concentration of hydrofluoric acid in the etching solution is (4-6) mol/L, the concentration of hydrogen peroxide is (0.2-0.3) mol/L, when the temperature of the etching solution is (5-15) DEG C, the obtained grating structure is steep and the side wall is smooth, the roughness of the grating side wall is about 1nm, the etching time is determined by the etching depth and the etching rate, the etching depth is the thickness of the top silicon, and the etching rate can be measured through experiments.

S11, placing the substrate in a gold plating electrolyte, and electroplating and depositing gold on the upper surface; FIG. 13 is a cross-sectional view of the structure after gold is electroplated on the upper surface.

S12, removing the protective adhesive 9 on the lower surface of the substrate, and coating the protective adhesive 9 on the upper surface of the substrate; and (3) removing the alkali-resistant protective glue by using a Piranha solution, and removing the alkali-resistant protective glue by using a water bath for 30 minutes at the water bath temperature of 80 ℃, wherein fig. 14 is a structural cross-sectional view of the protective glue removed from the lower surface and the protective glue coated on the upper surface. The protective glue 9 is the protective glue of Brewer Science. The specific process conditions of coating the Primer first and then coating can refer to the use instruction.

S13, etching the monocrystalline silicon in the non-mask area of the bottom layer; fig. 15 is a cross-sectional view of the structure after etching the lower surface single crystal silicon according to the embodiment of the present invention, in which a KOH aqueous solution with a mass fraction of 30% is used as an etching solution, the etching temperature is 80 ℃, and the etching time is longer than 6 hours. When the intermediate SiO2 layer was etched, a smooth bottom surface was visible, at which time the etch was stopped.

S14, removing the protective glue 9 on the upper surface; the alkali-resistant protective glue is removed by using a Piranha solution, the alkali-resistant protective glue can be removed by water bath for 30 minutes at the water bath temperature of 80 ℃, and the structural cross-sectional view of the upper surface of the protective glue removed is shown in fig. 16.

S15, etching the top monocrystalline silicon 1; fig. 17 is a cross-sectional view of the structure after etching the top-layer single-crystal silicon, which is provided by the embodiment of the present invention, and a KOH aqueous solution with a mass fraction of 30% is used as an etching solution, the etching temperature is 80 ℃, and the etching time is longer than 6 hours. When the intermediate SiO2 layer was etched, a smooth bottom surface was visible, at which time the etch was stopped.

And S16, removing the silicon nitride and the middle SiO2 layer in the window, cleaning and drying to obtain the X-ray gold transmission grating. Soaking in 48% hydrofluoric acid for 8 min to remove the silicon nitride and the intermediate SiO2 layer in the window, and removing the silicon nitride and the intermediate SiO2 layer to obtain a cross-sectional structure as shown in FIG. 18. And (3) cleaning with deionized water, and drying the sample by using a carbon dioxide critical point dryer so as to solve the problem of grating line adhesion caused by drying in the air. The dryer is a carbon dioxide critical point dryer of Quorum E3100 in UK, and the specific operation method can refer to the specification.

The invention also provides a preparation method of the semiconductor laser device for plasma diagnosis, which comprises the following steps:

the method comprises the following steps that firstly, an N-type limiting layer, an N-type waveguide layer, an active region 6, a P-type waveguide layer, a P-type limiting layer and an ohmic contact layer 9 are epitaxially prepared on a substrate 3 in sequence; the N-type substrate is a gallium arsenic substrate with a (100) plane deviated from a <111> direction by 15 degrees of an N-type deviation angle. On one hand, the formation of a metastable state ordered structure in the growth process can be inhibited by selecting a (100) plane 15-degree N-type deflection angle gallium arsenic substrate deviating from the <111> direction; on the other hand, the doping concentration of P-type impurities in the limiting layer can be improved, the effective potential barrier of electrons is improved, the electron leakage of the active region is inhibited, and the preparation of a high-power semiconductor laser is facilitated.

Etching the middle part of the ohmic contact layer 9 to form a P-type limiting layer so as to form a grating groove;

step three, preparing a transmission grating according to the size of the grating groove;

step four, installing the transmission grating into the grating groove;

preparing a P-type electrode on the epitaxial wafer;

and seventhly, thinning and polishing the substrate 3 to prepare the N-type electrode. And preparing a P-type electrode and an N-type electrode on the epitaxial wafer, wherein the electrodes are electrode materials capable of forming good ohmic contact with gallium arsenic materials, the P-type electrode is prepared by adopting a sputtering method, and the N-type electrode is prepared by adopting an evaporation method.

The preparation method of the transmission grating comprises the following steps:

s1, taking an SOI silicon chip as a substrate, plating a Cr film 14 on the upper surface of the substrate, and plating a silicon nitride film 15 on the lower surface of the substrate; the structural parameters of the SOI silicon wafer adopted in the embodiment of the invention are as follows: the top layer of monocrystalline silicon has a crystal orientation of <100> and a thickness of 2-10 microns; the thickness of the middle layer SiO2 is (1-2) microns; the bottom layer of monocrystalline silicon is in a <100> crystal orientation and has a thickness (300-500) microns, wherein the thicknesses of the top layer of monocrystalline silicon, the middle layer of SiO2 and the bottom layer of monocrystalline silicon are designed based on the requirements of products. Fig. 2 is a structural cross-sectional view of a substrate with a Cr-plated upper surface and a silicon nitride-plated lower surface according to an embodiment of the present invention, in which the Cr film is easily peeled off from the SOI wafer by a Cr-removing solution, and thus the Cr film is used as an intermediate layer of a transfer grating support structure, the Cr film is plated by an electron beam evaporation or ion beam sputtering method, the thickness of the Cr film must be greater than that of a catalytic metal, so that the Cr film can be removed by the Cr-removing solution, and experiments prove that a thickness greater than 100nm can meet requirements; the silicon nitride film and the monocrystalline silicon have similar structures, so that the silicon nitride film and the monocrystalline silicon have strong adhesive force, the silicon nitride film and the monocrystalline silicon do not fall off in the later ultrasonic cleaning process, and the silicon nitride does not react with the potassium hydroxide etching solution for windowing the lower surface of the silicon wafer, so that the silicon nitride film is used as a protective layer for manufacturing the grating outer frame structure, and can be plated by adopting a PECVD (plasma enhanced chemical vapor deposition) method, and the thickness is more than 40 nm.

S2, respectively coating photoresist 19 on the upper surface and the lower surface of the substrate, manufacturing a grating supporting structure mask on the upper surface by utilizing ultraviolet lithography, and manufacturing a grating outer frame mask on the lower surface; FIG. 3 is a structural cross-sectional view of a grating support structure mask made on the upper surface and a grating outer frame mask made on the lower surface, wherein the grating support structure mask is a line array, the period is preferably 10-20 micrometers, the line width is 2-3 micrometers, the grating outer frame mask image is an orthogonal grid, the width of the grid bars is 1-2 millimeters, and the interval of the grid bars is 4-6 millimeters. The photoresist is a positive photoresist, such as AZ MIR-701, the coating thickness (500-1000) nm is preferred, the photoresist is coated by using a rotary coating method, and the thickness can be adjusted by adjusting the rotating speed and the proportion of a solvent in the photoresist according to the use instruction of the photoresist. The gluing process is as follows: coating the surface, and baking; then coating the lower surface, and then baking the glue. The baking condition can refer to the photoresist application instruction, and for the AZ MIR-701 photoresist, the single baking parameter is baking for 2 minutes at 90 ℃ of a hot table. The ultraviolet lithography uses a URE-2000/35 type ultraviolet lithography machine of photoelectric technology research institute of Chinese academy of sciences, and the specific process conditions can refer to the photoresist use instruction and the lithography machine use instruction. Because the selected positive photoresist is adopted, the pattern of the photoetching mask is consistent with the target pattern. The process of ultraviolet photoetching comprises the following steps: exposing the upper surface in a contact manner; lower surface contact exposure; and (6) developing.

S3, etching the silicon nitride film 15 on the lower surface through reactive ions, and etching the Cr film 14 on the upper surface through a wet method; FIG. 4 is a cross-sectional view of a structure in which a silicon nitride film is etched on a lower surface and a Cr film is etched on an upper surface according to an embodiment of the present invention; for the etching of the silicon nitride film, an ICP-98A type induction coupling plasma etching machine developed by microelectronics of Chinese academy of sciences is used, the etching depth of the silicon nitride film is controlled by controlling the flow rate of reaction gas, the power of an excitation power supply, the power of a bias power supply and the etching time, and a large number of experiments prove that for the silicon nitride film with the thickness of 40nm, the adopted etching conditions are as follows: reaction gas CF 4; the flow rate is 20sccm, the excitation power supply power is 300W, the bias power supply power is 75W, and the time is 90 s. And (3) etching the Cr film by using a Cr removing liquid wet method, wherein the Cr removing liquid is prepared by mixing cerium ammonium nitrate: glacial acetic acid: water is mixed according to the mass ratio of 20:3: 100. Since the etching is isotropic, the etching time cannot be too long, otherwise the lateral undercutting effect will cause the Cr mask lines to disappear. The specific etching time can be obtained by experiment.

S4, removing the photoresist 19 on the upper surface and the lower surface; the photoresist on the upper surface and the lower surface is removed by acetone ultrasonic, and the structural cross-sectional view after the photoresist is removed is shown in fig. 5.

S5, coating an antireflective film 18 and a photoresist 19 on the upper surface of the substrate in sequence; fig. 6 is a cross-sectional view of a structure in which an antireflective film and a photoresist are sequentially coated on an upper surface according to an embodiment of the present invention, in order to reduce a standing wave effect in holographic exposure, before the photoresist is coated, a layer of antireflective film is coated on a prepared substrate, the antireflective film is selected from a series of Brewer Science, and the positive photoresist is selected from AZ MIR-701. The thickness of the antireflective film is about 150nm, and the thickness of the photoresist is about 300 nm.

S6, holographic photoetching is carried out to manufacture a grating mask, and the extending direction of the grating mask is vertical to the extending direction of the grating support structure mask; fig. 7 is a cross-sectional view of the photoresist grating mask according to the embodiment of the present invention, in which a holographic exposure is performed on a laemoscope exposure light path, and the photoresist grating mask is obtained after development, and when exposure is performed, the extending direction of the support structure mask is parallel to the optical platform, and the extending direction of the interference fringes that generate the photoresist grating mask pattern is perpendicular to the optical platform, so that the photoresist grating mask obtained by development is naturally perpendicular to the support structure.

S7, transferring the grating mask pattern of the photoresist 19 into the antireflection film 18 by reactive ion etching; fig. 8 is a structural cross-sectional view of transferring a photoresist grating mask to an antireflective film according to an embodiment of the present invention, where an etching depth of the antireflective film is controlled by controlling a reaction gas flow rate, an excitation power supply power, a bias power supply power, and an etching time, and finally, a photoresist grating mask pattern is transferred to the antireflective film to form the antireflective film of the grating structure.

S8, depositing catalytic metal on the upper surface of the substrate vertically downwards, where fig. 9 is a cross-sectional view of the structure after plating the catalytic metal according to the embodiment of the present invention, where the catalytic metal is gold, silver, or platinum; and depositing by adopting an ion beam sputtering or electron beam evaporation coating method to obtain the grating structure of the catalytic metal film.

S9, removing the photoresist 19, the antireflective film 18, the Cr film 14 and the catalytic metal attached to the photoresist 19 and the Cr film 14; the anti-reflective coating (ARC), the photoresist and the catalytic metal on the photoresist are removed by using acetone ultrasound, the Cr and the catalytic metal on the Cr are removed by using Cr-removing liquid ultrasound, and fig. 10 is a cross-sectional view of a structure for removing the anti-reflective coating, the photoresist, the Cr film and the catalytic metal attached to the photoresist and the Cr film according to an embodiment of the present invention.

S10, coating alkali-resistant protective glue 21 on the upper surface of the substrate; as shown in fig. 11.

S11, corroding the monocrystalline silicon on the lower surface until the corrosion is stopped to reach the middle SiO2 layer; fig. 12 is a cross-sectional view of the structure after etching the lower surface single crystal silicon according to the embodiment of the present invention, in which a KOH aqueous solution with a mass fraction of 30% is used as an etching solution, the etching temperature is 80 ℃, and the etching time is longer than 6 hours. When the intermediate SiO2 layer was etched, a smooth bottom surface was visible, at which time the etch was stopped.

S12, removing the alkali-resistant protective glue 21; the alkali-resistant protective glue is removed by using a Piranha solution, and the alkali-resistant protective glue can be removed by using a water bath for 30 minutes at the water bath temperature of 80 ℃, and the structural cross-sectional view after the alkali-resistant protective glue is removed is shown in fig. 13.

S13, removing the silicon nitride and the middle SiO2 layer in the window; soaking in 48% hydrofluoric acid for 8 min to remove the silicon nitride and the intermediate SiO2 layer in the window, and removing the silicon nitride and the intermediate SiO2 layer to obtain a cross-sectional structure as shown in FIG. 14.

S14, putting the substrate into etching liquid consisting of hydrofluoric acid and oxidant for metal catalytic etching; the oxidant can be hydrogen peroxide, potassium permanganate or silver nitrate, the concentration of each component of the specific etching solution and the etching temperature can be obtained through a contrast experiment, the optimal target is to etch a grating structure with a smooth and steep side wall, the hydrogen peroxide is taken as the oxidant, the concentration of hydrofluoric acid in the etching solution is (4-6) mol/L, the concentration of hydrogen peroxide is (0.2-0.3) mol/L, and when the temperature of the etching solution is (5-15) DEG C, the obtained grating structure is steep and the side wall is smooth.

And S15, removing the catalytic metal, rinsing and drying to obtain the X-ray self-supporting blazed transmission grating.

In addition, as a further improvement, the preparation method further comprises the steps of cleaving an edge line of the epitaxial wafer with the electrode, depositing a highly dense passivation layer on the front cavity surface and the rear cavity surface of the semiconductor laser through an atomic layer deposition method, then depositing an anti-reflection film on the passivation layer on the front cavity surface, and depositing a high-reflection film on the passivation layer on the rear cavity surface. The thickness of the highly dense passivation layer is 10nm, and the material of the highly dense passivation layer is Si3N 4. The passivation layer is highly dense, so that the highly dense passivation layer can more effectively prevent other atoms from entering the cavity surface material through the passivation layer compared with the conventional passivation method, thereby preventing optical catastrophe of the cavity surface, improving the damage threshold of the cavity surface, improving the power of the semiconductor laser and prolonging the service life of the semiconductor laser. The method can prevent oxygen in the air from oxidizing and damaging the cavity surface, and can omit the cleaning step before preparing the passivation film, thereby preventing the cleaning step from damaging the cavity surface, and protecting the integrity of the cavity surface structure to the maximum extent.

Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the idea of the present disclosure, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present description as described above, which are not provided in detail for the sake of brevity.

The embodiments of the present description are intended to embrace all such alternatives, modifications and variances that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalents, improvements, and the like that may be made within the spirit and principles of the embodiments described herein are intended to be included within the scope of the disclosure.

Claims

1. A semiconductor laser device for plasma diagnosis is characterized by comprising a first electrode, a second electrode, a substrate, a first limiting layer, a first waveguide layer, an active region, a second waveguide layer, a second limiting layer, an ohmic contact layer and an X-ray gold transmission grating layer, wherein the substrate is arranged between the first electrode and the second electrode and is sequentially arranged from the first electrode to the second electrode.

2. A semiconductor laser device for plasma diagnosis as set forth in claim 1, wherein the first electrode is an N-type electrode, the first confinement layer is an N-type confinement layer, the first waveguide layer is an N-type waveguide layer, the second electrode is a P-type electrode, the second confinement layer is a P-type confinement layer, and the second waveguide layer is a P-type waveguide layer.

3. The semiconductor laser device for plasma diagnosis as set forth in claim 2, wherein the N-type waveguide layer and the P-type waveguide layer are made of AlxGa1-xAs material, and the thickness ratio of the N-type waveguide layer to the P-type waveguide layer is 3: 1.

4. the semiconductor laser device for plasma diagnosis as set forth in claim 2, wherein the P-type confinement layer is made of AlxGa1-xAs material.

5. The semiconductor laser device for plasma diagnosis according to claim 1, wherein the active region is a quantum well active region or a quantum dot active region.

6. The semiconductor laser device for plasma diagnosis according to claim 1, wherein both opposite side faces of the semiconductor laser device for plasma diagnosis are provided with an antireflection film and a high-reflection film, respectively.

7. The method for manufacturing a semiconductor laser device for plasma diagnosis according to claim 1, comprising the steps of:

preparing a P-type electrode on the epitaxial wafer;

8. The method for manufacturing a semiconductor laser device for plasma diagnosis as set forth in claim 7, wherein the method for manufacturing the X-ray gold transmission grating includes the steps of:

s14, removing the protective glue on the upper surface;

s15, etching the top monocrystalline silicon;

9. The method as claimed in claim 7, further comprising the steps of cleaving the edge line of the epitaxial wafer having the electrodes, depositing a highly dense passivation layer on the front and rear facets of the semiconductor laser by atomic layer deposition, depositing an anti-reflection film on the passivation layer on the front facet, and depositing a highly reflective film on the passivation layer on the rear facet.