CN112993760B

CN112993760B - Semiconductor manufacturing method

Info

Publication number: CN112993760B
Application number: CN202110182585.3A
Authority: CN
Inventors: 陈伯庄
Original assignee: Guilin Leiguang Technology Co ltd
Current assignee: Guilin Leiguang Technology Co ltd
Priority date: 2021-02-08
Filing date: 2021-02-08
Publication date: 2021-08-24
Anticipated expiration: 2041-02-08
Also published as: CN112993760A; WO2022165899A1

Abstract

The invention provides a semiconductor manufacturing method, which is used for growing quantum wells with different layer thicknesses in the same plane in the single semiconductor epitaxial deposition process and comprises the following steps: carrying out first-time epitaxial growth to grow a basic epitaxial layer structure, wherein the basic epitaxial layer structure comprises a substrate, a sacrificial layer and a bridging layer, and the sacrificial layer is positioned between the substrate and the bridging layer; forming a bridge pattern by photolithography and etching, and forming a wafer with a patterned bridge head overhang; cleaning the wafer; the cleaned wafer with the patterned bridgehead suspension is sent back to the epitaxy equipment for second-layer epitaxy; and selectively removing part of the viaduct structure, thereby forming the wafer with epitaxial layers with different thicknesses in different regions. A corresponding laser integrated structure manufacturing method and a laser integrated structure manufactured thereby are also provided. When this optical mode exits the integrated device through the beam forming section, the resulting far field pattern is narrower, facilitating the coupling of the device light into the fiber and the reliability of the device.

Description

Semiconductor manufacturing method

Technical Field

The invention relates to the field of semiconductor parts and chips, in particular to a semiconductor manufacturing method for growing quantum wells with different layer thicknesses in the same plane in a single semiconductor epitaxial deposition process.

Background

In optoelectronic semiconductor integrated structures, an optical mode must be able to propagate along a horizontal plane waveguide from one section to another section of different properties with minimal loss. Generally, epitaxy can be used for completing parts with different properties on a plane by multiple growths, but the cost is high, and the heights of waveguides with different properties need to be strictly controlled. Techniques that enable the growth of sections with multiple portions of different properties in a single epitaxial growth are beneficial for reducing cost and complexity, and need to be developed and studied.

The related art such as so-called Selective Area Growth (SAG) involves an insulating film mask pattern serving as a mask for modifying a layer Growth rate in a predetermined region. The technique first forms a dielectric insulating film on a semiconductor substrate, performs photolithography thereof to form a mask pattern, and then uses MOCVD epitaxial growth (grows a semiconductor material. deposition of the semiconductor material does not occur on top of the insulating film mask. the growth rate inside the gap between the insulating film masks is improved as compared with a region having no intervening insulating film mask in the periphery.

As shown in fig. 1, which is a schematic structural view of a prior art solution outlined in detail in prior art US patent 5543353, US5543353A discloses a method of manufacturing a semiconductor photonic integrated circuit including first and second optoelectronic devices optically connected to each other on a single semiconductor substrate and formed by a selective area growth process including the step of growing compound semiconductor layers constituting the first and second optoelectronic devices, the first photonic device being formed in a specific area on the semiconductor substrate using a set of insulating film masks having an open space width therebetween, the open space width ranging from 1.0 to 0.125 times a vapor diffusion length of a group III species, the masks being arranged parallel to an optical axis of the first photonic device, the width of each mask being perpendicular to the optical axis, in the range of 16 to 800 μm, the second optoelectronic device is formed without using an insulating film mask. Taking us patent 5543353 as an example, the areas of modification growth are smaller compared to areas that are not modified by any mask pattern. This technique always results in a modified positive rate growth compared to the unmodified region, i.e. the epitaxial layer in the modified region is thicker than the unmodified region (fig. 1). When integrated structures require the use of these small regions in critical applications, the properties of these regions, such as Photoluminescence (PL) and lattice matching, must be carefully characterized. Most devices for characterizing PL and lattice matching can only read large-area data, and can not read small-size modification areas, so that the direct characterization with necessary precision is difficult to adopt; furthermore, if a small area is used to characterize the device, the device cost is very expensive.

Further, an example of an integrated structure is a laser having a passive Beam Forming Section (Beam Forming Section BFS). The key component of such an integrated structure is the laser, which requires direct monitoring and characterization of the epitaxial layers in this part of the fabrication. However, with SAG techniques, BFS must be formed in the unmodified epitaxial region, while lasers must be formed in the modified epitaxial region. Therefore, it is difficult to monitor and characterize materials for laser components by SAG technology.

Disclosure of Invention

The invention aims to provide a semiconductor manufacturing method for growing quantum wells with different layer thicknesses in the same plane in the single semiconductor epitaxial deposition process, and the invention conception is that a Selective Depletion Epitaxy (Selective Depletion Epitaxy) SDE method is adopted, which comprises the following steps:

step 1, carrying out first-time layer epitaxy to grow a basic epitaxial layer structure, wherein the basic epitaxial layer structure comprises a substrate (1), a sacrificial layer (2) and a bridging layer (3), and the sacrificial layer (2) is positioned between the substrate (1) and the bridging layer (3);

step 2, forming a bridge pattern by photolithography and etching, and forming a wafer with a patterned bridge head overhang;

step 3, cleaning the wafer processed in the step 2;

step 4, conveying the cleaned wafer with the patterned bridgehead suspension back to the epitaxial equipment for second-layer epitaxy;

and 5, selectively removing the viaduct structure (4) after the second epitaxial layer is formed, thereby forming the wafers with the epitaxial layers with different thicknesses in different areas.

Preferably, the step 1 is performed by Metal Organic Chemical Vapor Deposition (MOCVD).

Preferably, the substrate of step 1 is made of InP, GaAs, GaN or InAs or other semiconductor single crystal material.

Preferably, the sacrificial layer (2) and the bridge layer (3) have a composition that is lattice-matched or substantially lattice-matched to the material of the substrate (1), and when the substrate (1) is InP, the sacrificial layer (2) is InGaAs and the bridge layer (3) is InP.

Preferably, the step 2 is performed by selective depletion epitaxy, so as to form the bridge pattern on the region to be modified.

Preferably, the step 2 comprises:

step 21, etching through the bridge layer (3) outside the pattern;

the sacrificial layer (2) is removed using a selective etch, but the portions of the bridge layer within the pattern remain, so that the bridge overhangs the area to be modified, step 22.

Preferably, the bridge pattern comprises a support structure (5), an elevated bridge structure (4) and side beams (6) attached to the support structure (5), wherein the support structure (5) is larger than the width of the elevated bridge structure (4) and the width of the side beams (6).

Preferably, during the second epitaxial growth of the layer in step 4, a layer is deposited on the wafer, and the region under the elevated bridge structure is modified to a negative growth rate to form a layer having a thickness less than the thickness of the region outside the elevated bridge structure.

The invention also aims to provide a method for manufacturing a laser integrated structure by growing quantum wells with different layer thicknesses in the same plane in the single semiconductor epitaxial deposition process, which further comprises the following steps after the steps 1-5 are carried out:

step 6, carrying out third epitaxial growth to complete the preparation of the laser integrated device after forming the electric contact; or in order to form a Distributed Feedback (DFB) laser, a grating layer is epitaxially grown for the third time, then holographic exposure or electron beams are adopted to form a grating, and then the fourth time of epitaxy is carried out to form electric contact to complete the preparation of the laser integrated device;

and 7, forming a two-dimensional light guide structure through standard processing, wherein the two-dimensional light guide structure comprises a laser (14) with an electric contact point and a beam forming part (13), and the laser (14) and the beam forming part (13) are combined to form the laser integrated structure.

It is also an object of the present invention to provide a laser integrated structure for growing Quantum wells of different layer thicknesses in the same plane in a single semiconductor epitaxial deposition process, the laser integrated structure comprising a laser (14) and a beam forming part (13) respectively formed in different regions, the laser (14) being formed in a region other than an overpass structure (4) of unmodified epitaxy, the beam forming part (13) being formed in a region of modified epitaxy below the overpass structure (4), the beam forming part (13) being an active waveguide, the laser (14) having upper and lower SCH (Separate confining heterogeneous structure) (7) and lower Separate confining heterogeneous layer structure (9) to form two SCH (Separate confining heterogeneous layer structure) layers, multiple Quantum wells (qw Quantum wells) (8) being formed between the two SCH layers, a P + -InGaAs contact layer (11) and an InP transition layer (12) are arranged above the laser (14), and a contact metal layer (10) is arranged above the P + -InGaAs contact layer (11).

The invention has the beneficial effects that:

(1) when this optical pattern leaves the integrated device through the beam forming section, the resulting far field pattern is narrower compared to a simple laser device without the beam forming section.

(2) It is advantageous for optically coupling the device into an optical fiber that when the epitaxial layer is thin enough to exhibit quantum size effects, the beam forming section also becomes non-absorbing of light emitted by the lasing section due to the formation of quantum wells that are narrower than the lasing section and therefore have a higher bandgap. The reliability of the device is facilitated because the beam forming part has low losses for the laser mode and the exit mirror is also non-absorbing.

The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.

Drawings

Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. The objects and features of the present invention will become more apparent in view of the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a method of fabricating a semiconductor photonic integrated circuit according to the prior art;

FIG. 2 is a schematic diagram of a first sub-layer epitaxy structure implemented by MOCVD according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of bridge pattern formation by photolithography and etching according to an embodiment of the present invention;

FIG. 4 (a) is a schematic cross-sectional view of an epitaxial layer A-A grown by MOCVD after formation of a bridge by photolithography and etching according to an embodiment of the present invention;

FIG. 4 (B) is a schematic cross-sectional view of an epitaxial layer B-B grown by MOCVD after formation of a bridge by photolithography and etching according to an embodiment of the present invention;

FIG. 4 (C) is a schematic cross-sectional view of an epitaxial layer C-C grown by MOCVD after formation of a bridge by photolithography and etching according to an embodiment of the present invention;

fig. 5 is a rwg (ridge waveguide) laser with a beam forming section waveguide according to an embodiment of the present invention.

Detailed Description

The present embodiment provides a semiconductor manufacturing method for growing quantum wells with different layer thicknesses in the same plane in a single semiconductor epitaxial deposition process, and firstly, a viaduct structure is formed on a region to be modified, as shown in fig. 3. The epitaxial layer under the bridge is thinner than the epitaxial layer outside the bridge structure due to reduced source diffusion under the bridge structure. Thus, this technique results in a negative layer Epitaxy rate in the modified region compared to the unmodified region, as shown in fig. 4 (a) - (c), which the inventors have made as a Selective Depletion Epitaxy (Selective Depletion Epitaxy SDE).

The embodiment relates to a wafer manufacturing method for growing quantum wells with different layer thicknesses in the same plane in a single semiconductor epitaxial deposition process, which comprises the following steps:

step 1, referring to fig. 2, a first sub-layer epitaxy is performed by MOCVD (metal-organic chemical vapor deposition) to grow a basic epitaxial layer structure, where the basic epitaxial layer structure is composed of a substrate 1, a sacrificial layer 2 and a bridge layer 3, and the sacrificial layer 2 is located between the substrate 1 and the bridge layer 3. An example of the material of the substrate 1 may be InP, among others. The substrate 1 material may be GaAs, GaN, InAs or other similar materials depending on the application and lasing wavelength. The sacrificial layer 2 and the bridge layer 3 have a composition that is perfectly or substantially lattice matched to the material of the substrate 1.

As a preferred embodiment, the sacrificial layer 2 material and the bridge layer 3 material are chosen such that there is a selective chemical etchant that is selective over the other. In this example, the substrate 1 material is InP, the sacrificial layer 2 material may be InGaAs, and the bridge layer 3 material may be InP or other combinations that meet the above conditions.

Step 2, forming a bridge pattern by photolithography and etching, and forming a wafer with a patterned bridge head overhang; wherein the photolithography and etching process comprises two steps: step 21, etching through the bridge layer 3 outside the pattern; the sacrificial layer 2 is removed using selective etching, but the portions of the bridge layer 3 within the pattern remain, so that the bridge is suspended over the area to be modified, step 22.

As shown in fig. 3, the overpass structure 4 is first formed on the area that needs to be modified. The optimum distance between the viaduct and the wafer surface under the bridge is 2-6um, but other sizes are also possible, and the optimum width of the bridge structure is 2-10um but other sizes are also possible. The length of the bridge structure is determined by the design integration structure requirements. The width of the bridge structure may also vary along the axial direction resulting in variations in the thickness of the waveguide and quantum well. In order to keep the bridge suspended at the bridge level, the structure of the bridge comprises a support structure 5, a viaduct structure 4 and side beams 6 attached to the support structure 5. The side beam 6 may be more than one, or may be placed on one or both sides of the overpass. The support structure 5 is larger than the width of the structure of the viaduct 4 and the width of the side beams 6, so that some of the sacrificial layer 2 is not completely removed during the second etching. Referring to fig. 4, the epitaxial layer under the bridge is thinner than the epitaxial layer outside the bridge structure due to reduced source diffusion under the bridge structure. Thus, SDE techniques result in a negative layer epitaxy rate for the modified regions compared to the unmodified regions.

Step 3, cleaning the wafer processed in the step 2;

and 4, returning the cleaned wafer with the patterned bridgehead suspension to MOCVD equipment for second-layer epitaxy. During the second epitaxial growth of the layer, a layer is deposited on the wafer. The area under the overpass structure is modified to a negative growth rate, and thus the layer formed is thinner than the area outside the overpass structure.

And 5, selectively removing part of the viaduct structure 4 after the second epitaxial layer is formed, thereby forming the wafers with the epitaxial layers with different thicknesses in different areas.

The present embodiment provides a method for manufacturing a laser integrated structure, in which quantum wells with different layer thicknesses are grown in the same plane during a single semiconductor epitaxial deposition process, and after steps 1 to 5 are performed, the method further includes:

step 6, carrying out third epitaxial growth to complete the preparation of the laser integrated device after forming the electric contact; or in order to form a DFB (distributed feedback) laser, a grating layer is epitaxially grown for the third time, then a grating is formed by holographic exposure or electron beams, and then the fourth time of epitaxy is carried out to form electric contact, so that the preparation of a laser integrated device is completed;

after this standard processing may form a two-dimensional light guide structure, step 7. Further processing may form a laser 14 with electrical contacts and a beam forming section 13.

In this embodiment, a laser integrated structure for growing quantum wells with different layer thicknesses in the same plane in a single semiconductor epitaxial deposition process is prepared by using the complete preparation method formed in steps 1 to 7, the embodiment is a rwg (ridge waveguide) structure, and referring to fig. 5, the laser integrated structure comprises a laser 14 and a beam forming part 13 respectively formed in different regions, and the inventive concept is that in the example of applying the technique for growing quantum wells with different layer thicknesses in the same plane in a single semiconductor epitaxial deposition process to an integrated structure of a laser with a passive beam forming part (BFS), the laser 14 is formed in a region other than the viaduct structure 4 without modification, and the beam forming part 13 is formed in a region of modified epitaxy below the viaduct structure 4. Since the area of unmodified epitaxy is much larger than that of modified epitaxy, the laser sliced material can be easily monitored and characterized using the techniques of the present invention, such as by XRD for lattice matching of the epitaxial layer and PL for the spectrum of the epitaxial layer. The beam forming section 13 is a passive waveguide. The upper and lower portions of the laser 14 have an upper separation-limiting heterostructure 7 and a lower separation-limiting heterostructure 9, forming two separation-limiting heterostructure layers with a multi-Quantum well 8, MQW, Multiple Quantum Wells, formed therebetween. A P + -InGaAs contact layer 11 and an InP transition layer 12 are arranged above the laser 14, and a contact metal layer 10 is arranged above the P + -InGaAs contact layer 11.

In the embodiment of the RWG, the beam forming section 13 has thinner layers, and thus the laser optical mode occupies a larger cross-sectional area. This portion may act as a passive waveguide. Those skilled in the art, who are familiar with the art, will be familiar with the technology and may be practiced in other embodiments, such as BH (Buried heterogeneous).

When this optical pattern leaves the integrated device through the beam forming section, the resulting far field pattern is narrower compared to a simple laser device without the beam forming section. This is advantageous for optically coupling the device into an optical fiber. When the epitaxial layer is thin enough to exhibit quantum size effects, the beam forming section also becomes non-absorbing of light emitted from the laser section since the formed quantum well is narrower than the laser section and thus has a higher band gap. This is important because the beam forming part has low loss for the laser optical mode. The light-emitting mirror surface is also non-absorptive, which is beneficial to the reliability of the device.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It will be understood by those skilled in the art that variations and modifications of the embodiments of the present invention can be made without departing from the scope and spirit of the invention.

Claims

1. A semiconductor manufacturing method, characterized by comprising the steps of:

step 2, forming a bridge pattern through photoetching and etching, forming a wafer with a patterned bridge head suspension, and implementing the bridge pattern on an area needing to be modified by adopting a selective depletion epitaxy mode;

step 3, cleaning the wafer processed in the step 2;

and 5, selectively removing part of the viaduct structure (4) after the second epitaxial layer is formed, thereby forming the wafers with epitaxial layers with different thicknesses in different regions.

2. A semiconductor manufacturing method according to claim 1, characterized in that: the step 1 epitaxy is carried out by means of Metal Organic Chemical Vapor Deposition (MOCVD).

3. A semiconductor manufacturing method according to claim 1, characterized in that: the substrate (1) of the step 1 is made of InP, GaAs, GaN or InAs.

4. A semiconductor manufacturing method according to claim 3, wherein: the sacrificial layer (2) and the bridge layer (3) have a composition that is lattice-matched or substantially lattice-matched to the material of the substrate (1), and when the material of the substrate (1) is InP, the material of the sacrificial layer (2) is InGaAs, and the material of the bridge layer (3) is InP.

5. A semiconductor manufacturing method according to claim 1, characterized in that: the step 2 comprises the following steps:

step 21, etching through the bridge layer (3) outside the pattern;

the sacrificial layer (2) is removed using selective etching, but portions of the bridge layer (3) within the pattern are retained, leaving the bridge suspended over the area to be modified, step 22.

6. A semiconductor manufacturing method according to claim 1, characterized in that: the bridge pattern comprises a support structure (5), an elevated bridge structure (4) and side beams (6) attached to the support structure (5), wherein the support structure (5) is larger than the width of the elevated bridge structure (4) and the width of the side beams (6).

7. A semiconductor manufacturing method according to claim 1, characterized in that: and 4, depositing a layer on the wafer during the second epitaxial growth of the layer, wherein the lower area of the elevated bridge structure (4) is modified to a negative growth rate to form a layer with a thickness smaller than that of the area outside the elevated bridge structure (4).

8. A semiconductor manufacturing method according to any one of claims 1 to 7, further comprising, after the step 1 to 5 are performed:

9. A laser integrated structure formed using the semiconductor manufacturing method according to claim 8, the laser integrated structure comprising a laser (14) and a beam forming portion (13) formed in different regions, respectively, the laser (14) being formed in a region other than the viaduct structure of unmodified epitaxy, the beam forming portion (13) being formed in a region of modified epitaxy below the viaduct structure (4), the beam forming portion being a passive waveguide, the laser (13) having an upper separation-limiting heterostructure (7) and a lower separation-limiting heterostructure (9) respectively on an upper portion and a lower portion thereof, thereby forming two separation-limiting heterolayer structures, forming a quantum well (8) therebetween, a P + -InGaAs contact layer (11) and an InP transition layer (12) being provided above the laser (14), and a contact metal layer (10) is arranged above the P + -InGaAs contact layer (11).