CN101145672A - Fabrication method of micro-hole vertical cavity surface emitting laser - Google Patents

Abstract

A preparation method of a micro-hole vertical cavity surface emitting laser, comprising the following steps: Step 1: Take an ordinary vertical cavity surface emitting laser, the laser includes an N-surface electrode, an optical cavity surface, an optical hole, and a P-surface electrode; Step 2 : Prepare an antireflection coating on the surface of the optical cavity of a common vertical cavity surface emitting laser; Step 3: use focused ion beam etching technology to etch off the antireflection coating on the P surface electrode; Step 4: Antireflection coating on the surface of the optical cavity Prepare a metal film on the transparent film and the P-surface electrode; Step 5: Etch a sub-wavelength micro-hole on the light exit hole to complete the fabrication of the micro-hole vertical cavity surface emitting laser.

Description

Fabrication method of micro-hole vertical cavity surface emitting laser

technical field

The invention relates to a preparation method of a semiconductor laser, in particular to a preparation method of a microhole vertical cavity surface emitting laser.

Background technique

Current optical data storage systems, such as CD or DVD, are far-field storage systems, and their storage density is limited due to the limitation of diffraction limit. Utilizing the evanescent wave in the near-field of the light source can break through the limitation of the diffraction limit and greatly increase the storage density. Therefore, high-density optical data storage has become a large field of near-field optical applications. If a tiny light source that breaks through the diffraction resolution limit can be manufactured, it will be a great impetus to the application fields such as micro-area imaging, micro-area detection and nano-lithography. In this context, near-field optics has developed rapidly. Near-field data storage has become one of the most promising high-density data storage methods. Among them, the preparation of high-quality near-field light sources is an important research direction.

Based on the very-small-aperture laser (VSAL) prepared by the edge-emitting laser, the probe-type near-field storage has made breakthrough progress, and the light transmission efficiency is greatly improved compared with ordinary fiber optic probes. It greatly improves the resolving power of the near-field optical microscope, and as a nanoscale light source, it can also be used in many fields such as nanolithography, nanoprocessing, nanolight manipulation, and nanospectroscopy.

However, since the preparation of VASL needs to etch tiny holes on the active area, and the size of the active area is very small, it is difficult to control the precise positioning of the small holes, and the repeatability of the process is poor. As a result, the preparation process is complex, difficult and the yield is low. Moreover, the manufactured devices have a short lifetime, and the achieved power density is not enough for data storage.

Based on the superiority of the vertical cavity surface emitting laser over the edge emitting laser itself, if it has a smaller size, it is more conducive to the realization of integration, the threshold current density is low, and it has the characteristics of symmetrical light output mode. And compared to the micro-hole laser based on the edge-emitting laser, it is relatively easy to prepare the micro-hole laser based on the vertical cavity surface emitting laser.

Contents of the invention

The object of the present invention is to provide a preparation method of a micro-hole vertical cavity surface emitting laser, which has the following advantages: smaller size, favorable for integration, low threshold current density, and symmetrical light output mode; preparation process Simple, good process repeatability, easy positioning when etching tiny holes 16.

A preparation method of a micro-hole vertical cavity surface emitting laser of the present invention is characterized in that it comprises the following steps:

Step 1: Take an ordinary vertical cavity surface emitting laser, which includes N-face electrode, light-emitting cavity surface, light-emitting hole, and P-face electrode;

Step 2: Prepare an anti-reflection coating on the light exit cavity surface of a common vertical cavity surface emitting laser;

Step 3: using focused ion beam etching technology to etch away the anti-reflection coating on the P surface electrode;

Step 4: Prepare a metal film on the antireflection film on the surface of the light exit cavity and on the P surface electrode;

Step 5: Etching tiny holes with sub-wavelength dimensions on the light exit hole to complete the fabrication of the micro-hole vertical cavity surface emitting laser.

Wherein the anti-reflection film material is a mixture of SiO ₂ and SiN _x , or Al ₂ O ₃ , MgF material, with a thickness of 200nm-400nm.

The anti-reflection film is an insulating layer, which can avoid direct contact between the metal and the surface of the light-emitting cavity in the next step, thereby protecting the surface of the light-emitting cavity.

The P-side electrode and the N-side electrode are current injection channels.

The metal film material is Ti/Au, Ti/Ag, Ti/Al or Ti/Ni, wherein the thickness of Ti is 5nm-30nm, and the thickness of Au, Ag, Al or Ni layer is 60nm-400nm.

Wherein the Ti in the metal film can improve the adhesion of the device surface.

Wherein the metal film is a high reflection film, which can block the normal output light of a common vertical cavity surface emitting laser.

Wherein the size of the tiny hole etched on the light exit hole is of sub-wavelength order, and the depth is the same as the thickness of the metal film.

Wherein, during the focused ion beam etching, the minimum ion beam current density and the maximum overlap distance are used.

The preparation method of the microhole vertical cavity surface emitting laser of the present invention is prepared on the basis of the common vertical cavity surface emitting laser. The specific preparation process includes coating an anti-reflection film 14 on the optical exit cavity surface 11 of a common vertical cavity surface emitting laser, removing the anti-reflection film 14 on the P surface electrode 13, and then coating a metal film 15, and then using the method of focused ion beam etching on the light exit surface. A micro hole 16 with a sub-wavelength size is prepared on the hole 12 to confine the light in a low-loss micro resonator cavity, and make the light exit through the micro hole 16, thereby generating high-efficiency near-field light.

Description of drawings

In order to further illustrate the technical contents of the present invention, the present invention is described in detail below in conjunction with accompanying drawing as follows, wherein:

Fig. 1 is a schematic diagram of the exit cavity surface of a common vertical cavity surface emitting laser.

Fig. 2-Fig. 5 are process flow charts for manufacturing the micro-hole vertical cavity surface emitting laser of the present invention on the basis of common vertical cavity surface emitting lasers.

In the figure: 10 is the N surface electrode, 11 is the light exit cavity surface, 12 is the light exit hole, 13 is the P surface electrode, 14 is the antireflection film, 15 is the metal film, 16 is the micro hole, 17 is the side surface, and 18 is the laser.

Detailed ways

Please refer to Fig. 1-shown in Fig. 5, a kind of micro hole vertical cavity surface emitting laser of the present invention, comprises the following steps:

(1) Deposit an anti-reflection film 14 on the light exit cavity surface 11 of a common VCSEL (Fig. 1) by electron cyclotron resonance plasma chemical vapor deposition (ECR plasma CVD), as shown in Fig. 2, the materials are SiO ₂ and SiN _x mixture, or Al ₂ O ₃ , MgF and other materials, with a thickness of 200nm-400nm. The anti-reflection film 14 is used as an insulating film to avoid direct contact between the metal and the light exit cavity surface 11 in the next step, thereby protecting the light exit cavity surface 11 .

(2) Etching away the anti-reflection film 14 on the P-surface electrode 13 by using a focused ion beam system, as shown in FIG. 3 , so that the P-surface electrode 13 and the N-surface electrode 10 can form a current injection channel. The etching time is 30s-120s.

(3) sputter metal film 15 on anti-reflection film 14, as shown in Figure 4, material is Ti/Au, Ti/Ag, Ti/Al or Ti/Ni, wherein the thickness of Ti is thinner, is 5nm-30nm , mainly to improve the adhesion, so that the Au layer has better adhesion on the cavity surface and is not easy to peel off. The thickness of the Au, Ag, Al or Ni film is 60nm-400nm, and the metal film 15 acts as a reflective film to block the normal output light of the laser, so that the reflectivity of the optical cavity surface 11 is greater than 90% near the lasing wavelength. When preparing the metal film 15, the N surface electrode 10 of the laser is glued on the glass sheet with an insulating material, and the side 17 of the laser is protected with an insulating material to prevent the metal from spreading to the device side 17 during the sputtering process so that the N surface electrode 10 and The surface 11 of the light exit cavity is short-circuited. After the sputtering is completed, the power-voltage-current characteristics of the laser are detected to ensure that the voltage characteristics of the laser are normal, and the metal film 15 completely covers the normal output light, so as to improve the yield of the micro-hole vertical cavity surface emitting laser.

(4) Use focused ion beam etching technology to etch a sub-wavelength micro-hole 16 on the light exit hole 12, as shown in Figure 5, confine the light in the low-loss micro-resonator cavity, and make the light exit through the micro-hole 16 , to generate high-efficiency near-field light. When etching the metal film 15, in order to minimize the damage to the light exit cavity surface 11 during the etching process, the minimum ion beam current density is used, which is the main factor determining the etching rate. For the coincidence distance, which is the main factor determining the surface roughness, the largest coincidence distance is used. The etched microholes 16 are of sub-wavelength size, the wavelength of the VCSEL involved in the present invention is 650nm-980nm, the diameter of the microholes 16 is 50nm-450nm, and the depth is the same as the thickness of the metal film 15 . The etching time for a single tiny hole 16 is generally 20s-60s, based on the fact that the metal film 15 is just removed.

Described step (1) is carried out like this, use electron cyclotron resonance plasma chemical vapor deposition method (ECR plasmaCVD) deposition material to be the anti-reflection film 14 of SiO ₂ and _SiNx mixture on the light exit cavity surface 11 of common VCSEL, Or Al ₂ O ₃ , MgF and other materials, with a thickness of 200nm-400nm. This method has a high degree of vacuum; it can be deposited at a lower temperature; the deposited anti-reflection film 14 has almost no pinholes and high density; the _Hz /He plasma of electron cyclotron resonance can be used to decarburize and deoxygenate the cavity surface Cleaning treatment, and the deposited film has good reproducibility. This layer of anti-reflection film 14 is used as an insulating layer to avoid direct contact between the metal and the light-emitting cavity surface 11 during the next step of gold plating, and can play a role in protecting the light-emitting cavity surface 11 .

The step (2) is carried out by etching off the anti-reflection film 14 on the P-face electrode 13 with a thickness of 200nm-400nm, so that the P-face electrode 13 and the N-face electrode 10 can form a current injection channel. The etching time is 30s-120s. The dual-beam DualBeam ^TM DB235-FIB workstation produced by FEI Company of the United States is used, and the minimum focusing point of the Ga+ ion beam is 7nm. The whole system works under the condition of high vacuum above 10 ^-4 Pa.

Described step (3) is carried out like this, uses the magnetron sputtering method to coat metal film 15, and material is Ti/Au, Ti/Ag, Ti/Al or Ti/Ni, wherein the thickness of Ti is relatively thin, is 5nm- 30nm, its function is to improve the adhesion, so that the Au layer has better adhesion on the cavity surface and is not easy to peel off. The thickness of the Au, Ag, Al or Ni layer is 60nm-400nm. The metal film 15 as a reflective film can block the normal output light of the vertical cavity surface emitting laser, so that the reflectivity of the optical cavity surface 11 is greater than 90% near the lasing wavelength. When preparing the metal film 15, the N surface electrode 10 of the laser is glued on the glass sheet with an insulating material, and the side 17 of the laser is protected with an insulating material at the same time to prevent the metal from spreading to the device side 17 during the sputtering process so that the N surface electrode 10 and A short circuit occurs on the surface 11 of the light exit cavity. After the sputtering is completed, the power-voltage-current characteristics of the laser are detected to ensure that the metal film 15 completely covers the normal output light, and the voltage characteristics of the device are normal, so as to improve the yield of microporous devices.

Described step (4) is carried out like this, the size of the tiny hole 16 etched on the light exit hole 12 is sub-wavelength order of magnitude, the wavelength of the vertical cavity surface emitting laser involved in the present invention is 650nm-980nm, and the diameter of the tiny hole 16 is 50nm-450nm, the shape is a single circular hole, square hole or special-shaped hole, it can also have a certain periodic ring structure or an array structure composed of a series of tiny holes 16, etch the depth of the tiny holes 16 and the thickness of the metal film 15 same. The etching time for a single tiny hole 16 is generally 20s-60s, based on the fact that the metal film 15 is just removed. The same FIB system as in step (2) is used. The etching process has certain requirements on the etching rate of the metal film 15. By adjusting the ion beam current density, dwell time, and beam spot overlap distance during etching, The process conditions such as ion beam scanning time are precisely controlled, so that better surface flatness can be obtained after etching. In order to reduce the damage to the optical cavity surface 11 during etching to the greatest extent, the minimum ion beam current density is used, which is the main factor determining the etching rate. At the same time, the maximum coincidence distance is adopted, which is the main factor determining the surface roughness.

Claims (9)

1. the preparation method of a micro-hole vertical cavity radiation laser is characterized in that, may further comprise the steps:

Step 1: get a common vertical cavity surface emitting laser, this laser comprises, N face electrode, emitting cavity face, light hole, p side electrode;

Step 2: on the emitting cavity face of common vertical cavity surface emitting laser, prepare anti-reflection film;

Step 3: utilize the focused-ion-beam lithography technology to etch away anti-reflection film on the p side electrode;

Step 4: preparing metal film on the anti-reflection film on the emitting cavity face He on the p side electrode;

Step 5: on light hole, etch the micro hole of sub-wavelength dimensions, finish the making of micro-hole vertical cavity radiation laser.

2. the preparation method of micro-hole vertical cavity radiation laser according to claim 1 is characterized in that, wherein said anti-reflection film material is SiO ₂And SiN _xMixture, or Al ₂O ₃, the MgF material, thickness is 200nm-400nm.

3. the preparation method of micro-hole vertical cavity radiation laser according to claim 1 is characterized in that, wherein said anti-reflection film is an insulating barrier, can avoid that metal directly contacts with the emitting cavity face in next step, thus protection emitting cavity face.

4. the preparation method of micro-hole vertical cavity radiation laser according to claim 1 is characterized in that, wherein said p side electrode and N face electrode are the electric current injection channel.

5. the preparation method of micro-hole vertical cavity radiation laser according to claim 1, it is characterized in that, wherein said metal membrane material is Ti/Au, Ti/Ag, Ti/Al or Ti/Ni, and wherein the thickness of Ti is 5nm-30nm, and the thickness of Au, Ag, Al or Ni layer is 60nm-400nm.

6. the preparation method of micro-hole vertical cavity radiation laser according to claim 1 is characterized in that, the Ti in the wherein said metal film can improve the adhesiveness of device surface.

7. the preparation method of micro-hole vertical cavity radiation laser according to claim 1 is characterized in that, wherein said metal film is highly reflecting films, can stop common vertical cavity surface emitting laser and export light normally.

8. the preparation method of micro-hole vertical cavity radiation laser according to claim 1 is characterized in that, wherein said on light hole the micro hole of etching be of a size of the sub-wavelength magnitude, the thickness of the degree of depth and metal film is identical.

9. the preparation method of micro-hole vertical cavity radiation laser according to claim 1 is characterized in that, during wherein said focused-ion-beam lithography, adopts minimum ion beam current density and maximum coincidence distance.

Images