WO2019047235A1

WO2019047235A1 - Phase modulator and fabrication method therefor, and silicon-substrate electro-optic modulator

Info

Publication number: WO2019047235A1
Application number: PCT/CN2017/101286
Authority: WO
Inventors: 王志仁; 周林杰; 周砚扬; 刘磊
Original assignee: 华为技术有限公司
Priority date: 2017-09-11
Filing date: 2017-09-11
Publication date: 2019-03-14
Also published as: CN111051969A; CN111051969B

Abstract

A phase modulator and a fabrication method therefor, and a silicon-substrate electro-optic modulator. A P-type doped region (2) is divided by the phase modulator into a first P-type doped region (21) and a second P-type doped region (22); an N-type doped region (3) is divided into a first N-type doped region (31) and a second N-type doped region (32), wherein the doping concentration of the second P-type doped region (22) is smaller than that of the first P-type doped region (21), and the doping concentration of the second N-type doped region (32) is smaller than that of the first N-type doped region (31), thus achieving good electrical contact between the phase modulator and a driving circuit by using the heavy doping concentrations of the first P-type doped region (21) and the first N-type doped region (31), as well as reducing the doping concentration of the P-type doped region (2) at one side close to a PN junction structure (1) by using the second P-type doped region (22), reducing the doping concentration of the N-type doped region (3) at one side close to the PN junction structure (1) by using the second N-type doped region (32), and reducing the optical transmission loss of the phase modulator, thereby reducing the optical transmission loss of the silicon-substrate electro-optic modulator.

Description

Phase modulator and manufacturing method thereof, silicon-based electro-optic modulator

Technical field

The present application relates to the field of optical signal modulation technologies, and in particular, to a phase modulator and a method for fabricating the same, and a silicon-based electro-optic modulator.

Background technique

In recent years, with the rapid development of information technology, people are increasingly demanding the development of backbone networks with ultra-high-speed transmission capabilities, and large-bandwidth ultra-high-speed optical modulators are key components for achieving high-speed transmission capabilities. Silicon-based electro-optical modulators are receiving more and more attention due to their high integration, low cost and compatibility with traditional CMOS processes. However, the transmission loss of the existing silicon-based electro-optic modulator is large.

Summary of the invention

In a first aspect, an embodiment of the present application provides a phase modulator, including:

a PN junction structure, the PN junction structure including oppositely disposed P regions and N regions; and a PN junction between the P region and the N region;

a P-type doped region electrically connected to the P region, the P-type doped region includes a first P-type doped region and a second P-type doped region, wherein the second P-type doped region is located Between the P region and the first P-type doped region, and a doping concentration of the first P-type doped region is greater than a doping concentration of the second P-type doped region, thereby utilizing the The heavily doped concentration of the first P-type doped region achieves good electrical contact of the phase modulator with the driver circuit and utilizes the second P-type doped region to reduce the P-type doped region close to the PN The doping concentration on one side of the junction structure reduces the optical transmission loss of the phase modulator, thereby reducing the optical transmission loss of the silicon-based electro-optic modulator;

An N-type doped region electrically connected to the N region, the N-type doped region includes a first N-type doped region and a second N-type doped region, wherein the second N-type doped region is located Between the first N-type doped region and the N region, and a doping concentration of the first N-type doped region is greater than a doping concentration of the second N-type doped region, thereby utilizing the The heavily doped concentration of the first N-type doped region achieves good electrical contact of the phase modulator with the driver circuit and utilizes the second N-type doped region to reduce the N-type doped region close to the PN The doping concentration on one side of the junction structure reduces the optical transmission loss of the phase modulator, thereby reducing the optical transmission loss of the silicon-based electro-optic modulator.

In one implementation, the doping concentration of the second P-type doping region is greater than the doping concentration of the P region; the doping concentration of the second N-type doping region is greater than the doping of the N region Miscellaneous concentration.

In one implementation, the doping concentration of the second P-type doping region is gradually decreased in a direction parallel to the first P-type doping region to the P region to reduce the phase Optical transmission loss due to carrier absorption effects in the modulator.

In one implementation, the doping concentration of the second N-type doping region is gradually decreased in a direction parallel to the first N-type doping region to the N region to reduce the phase Optical transmission loss due to carrier absorption effects in the modulator.

In one implementation, the doping concentration of the first P-type doping region is on the order of 1*10 ²⁰ to ensure good electrical contact between the first P-type doping region and the external driving circuit; The doping concentration of an N-type doping region is on the order of 1*10 ²⁰ to ensure good electrical contact of the first N-type doping region and the driving circuit.

In one implementation, the doping concentration of the P region is on the order of 1*10 ¹⁷ -1*10 ¹⁸ , and the doping concentration of the N region is on the order of 1*10 ¹⁷ -1*10 ¹⁸ to The optical transmission loss of the phase modulator is reduced while ensuring the modulation efficiency of the phase modulator.

In a second aspect, an embodiment of the present application provides a silicon-based electro-optic modulator comprising the phase modulator of any of the above.

In a third aspect, an embodiment of the present application provides a method for fabricating a phase modulator, including:

Providing a silicon wafer, the silicon wafer comprising a silicon substrate, an isolation layer on a surface of the silicon substrate, and a planar layer on a side of the isolation layer facing away from the silicon substrate;

Removing a portion of the planar layer to form a raised structure, the raised structure comprising a first surface and a second surface and a third surface on opposite sides of the first surface, the first surface being higher than the second a surface and the third surface;

Forming a PN junction structure in the first surface, the PN junction structure including oppositely disposed P regions and N regions; and a PN junction between the P region and the N region;

Forming a first P-type doping region in the second surface, a doping concentration of the first P-type doping region being greater than a doping concentration of the P region;

Forming a first N-type doping region in the third surface, the doping concentration of the first N-type doping region being greater than a doping concentration of the N region;

Forming a second P-type doped region in the second surface, and forming a second N-type doped region in the third surface, wherein the second P-type doped region is located in the first P Between the doped region and the P region, and the doping concentration of the second P-doped region is less than the doping concentration of the first P-type doped region; the second N-type doped region Located between the first N-type doped region and the N region, and the doping concentration of the second N-type doped region is less than a doping concentration of the first N-type doped region.

A phase modulator fabricated by the method for fabricating a phase modulator according to an embodiment of the present application, by dividing the P-type doped region into two portions of the first P-type doping region and the second P-type doping region The doping concentration of the second P-type doping region is smaller than the doping concentration of the first P-type doping region, thereby realizing the using the heavily doped concentration of the first P-type doping region Good electrical contact of the phase modulator with the driver circuit, and using the second P-type doping region to reduce the doping concentration of the P-type doping region near the side of the PN junction structure, lowering the phase modulator The optical transmission loss, which in turn reduces the optical transmission loss of the silicon-based electro-optic modulator. Meanwhile, the phase modulator fabricated by the phase modulator manufacturing method provided by the embodiment of the present application further divides the N-type doping region into the first N-type doping region and the second N-type doping region. a two-part, wherein a doping concentration of the second N-type doping region is smaller than a doping concentration of the first N-type doping region, thereby realizing utilizing a heavily doped concentration of the first N-type doping region The phase modulator is in good electrical contact with the driving circuit, and uses the second N-type doping region to reduce the doping concentration of the N-type doping region near the side of the PN junction structure, and reduce the phase The optical transmission loss of the modulator, which in turn reduces the optical transmission loss of the silicon-based electro-optic modulator.

In one implementation, in a direction parallel to the first P-type doped region to the P region, the first The doping concentration of the second P-type doping region is gradually decreased to reduce the optical transmission loss due to the carrier absorption effect in the phase modulator; parallel to the first N-type doping region to the In the direction of the N region, the doping concentration of the second N-type doping region is gradually decreased to reduce the optical transmission loss due to the carrier absorption effect in the phase modulator.

In one implementation, forming a second P-type doped region in the second surface and forming a second N-type doped region in the third surface includes:

Forming a first mask layer on the first surface of the raised structure;

Forming a sidewall structure on a side of the convex structure facing the second surface and the third surface, a projection of the sidewall structure on the flat layer and the first P-type doping region not Overlapped and not overlapping the first N-type doped region;

Forming a second mask layer on a side of the sidewall structure facing away from the planar layer, the second mask layer covering the third surface, the first surface, and the first P-type doped region Exposing a portion of the sidewall structure at the second surface;

Forming a second P-type doped region in a region of the second surface below the sidewall structure, using the second mask layer as a mask;

Removing the second mask layer;

Forming a third mask layer on a side of the sidewall structure facing away from the planar layer, the third mask layer covering the second surface, the first surface, and the first N-type doped region Exposing a portion of the side wall structure at the third surface;

Forming a second N-type doped region in a region of the third surface below the sidewall structure by using the third mask layer as a mask;

The material of the first mask layer and the second mask layer are different, and the materials of the first mask layer and the third mask layer are different.

In one implementation, the material of the first mask layer is silicon nitride, germanium or silicon oxynitride.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any creative work.

1 is a schematic structural diagram of a phase modulator according to an embodiment of the present application;

2 is a schematic structural diagram of a phase modulator according to another embodiment of the present application;

3 is a schematic structural diagram of a silicon-based electro-optic modulator according to an embodiment of the present application;

4 is a flowchart of a method for fabricating a phase modulator according to an embodiment of the present application;

5 to FIG. 26 are cross-sectional views showing a structure of each step in a method of fabricating a phase modulator according to another embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application are clearly and completely described in the following with reference to the drawings in the embodiments of the present application. It is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present application without departing from the inventive scope are the scope of the present application.

In the following description, numerous specific details are set forth in order to facilitate a full understanding of the application, but the invention may be practiced in other ways than those described herein, and those skilled in the art can do without departing from the scope of the application. The invention is not limited by the specific embodiments disclosed below.

Existing silicon-based electro-optic modulators include a phase modulator (also referred to as a phase shifter), optocouplers on opposite sides of the phase modulator for respectively connecting the input and output, and with the optocoupler and a transmission waveguide between the phase modulators, wherein the phase modulator comprises a PN junction structure and a P-type doped region and an N-type doped region on both sides of the PN junction, wherein the PN junction structure The P-region and the N-region including the opposite arrangement and the PN junction between the P-region and the N-region are mainly used for realizing phase modulation of an optical signal, and the P-doped region and the N-type doped region are mainly used for Electrically connecting an external driving circuit to apply an operating signal to the PN junction structure by using an external driving circuit. The P-type doping is performed in the P-type doping region and the N-type doping region of the phase modulator formed by the prior art. The region is a heavily doped region in which the doping concentration is uniformly distributed, and the N-doped region is also a heavily doped region in which the doping concentration is uniformly distributed, and between the P-doped region and the N-type doped region and the PN junction The closer the distance is, the more carriers of the heavily doped region penetrate into the P and N regions of the PN junction structure, The more carriers in the P and N regions of the PN junction structure, the greater the doping concentration, the greater the optical transmission loss of the phase modulator, resulting in greater optical transmission loss of the silicon-based electro-optic modulator. .

In view of this, the embodiment of the present application provides a phase modulator, as shown in FIG. 1, the phase modulator includes:

a PN junction structure 1, the PN junction structure 1 includes oppositely disposed P regions 11 and N regions 12, and a PN junction 13 between the P region 11 and the N region 12, wherein the P region 11 is a P-type semiconductor doped region in the PN junction structure, the N region 12 being an N-type semiconductor doped region in the PN junction structure;

a P-type doping region 2 electrically connected to the P region 11 , the P-type doping region 2 including a first P-type doping region 21 and a second P-type doping region 22, wherein the second P a doping region 22 is located between the P region 11 and the first P-type doping region 21, and a doping concentration of the first P-type doping region 21 is greater than the second P-type doping region Doping concentration of 22;

An N-type doped region 3 electrically connected to the N region 12, the N-type doped region 3 includes a first N-type doped region 31 and a second N-type doped region 32, wherein the second N The doped region 32 is located between the first N-type doped region 31 and the N region 12, and the doping concentration of the first N-type doping region 31 is greater than the second N-type doped region Doping concentration of 32.

In the embodiment of the present invention, the P-type doping region 2 and the N-type doping region 3 are used for electrically connecting with a driving circuit, thereby passing through the P-type doping region 2 and the N-type doping region. 3 Applying a driving signal supplied from the driving circuit to the PN junction structure 1 to realize phase modulation of the optical signal.

The phase modulator provided by the embodiment of the present invention divides the P-type doping region 2 into two parts, the first P-type doping region 21 and the second P-type doping region 22, wherein the The doping concentration of the second P-type doping region 22 is smaller than the doping concentration of the first P-type doping region 21, thereby realizing the phase modulation by using the heavily doped concentration of the first P-type doping region 21. Good electrical contact with the driving circuit, and using the second P-type doping region 22 to reduce the doping concentration of the P-type doping region 2 near the PN junction structure 1 side, reducing the phase modulation Optical transmission loss. Similarly, the N-type doping region 3 is divided into a first N-type doping region 31 and a second N-type doping region 32, wherein the doping concentration of the second N-type doping region 32 is similar. Less than the doping concentration of the first N-type doping region 31, thereby achieving good electrical contact between the phase modulator and the driving circuit by using the heavily doped concentration of the first N-type doping region 31, and utilizing the second N The doping region 32 reduces the doping concentration of the N-type doping region 3 near the PN junction structure 1 side, and reduces the optical transmission loss of the phase modulator.

It should be noted that if the doping concentration of the second P-type doping region 22 is too low, the series equivalent resistance of the PN junction 13 is significantly increased, so that the RC constant is increased, and the phase modulator is lowered. Bandwidth. Similarly, if the doping concentration of the second N-type doping region 32 is too low, the series equivalent resistance of the PN junction 13 is also increased, so that the RC constant is increased to lower the bandwidth of the optical waveguide. Therefore, in one embodiment of the present application, the doping concentration of the second P-type doping region 22 is greater than the doping concentration of the P region 11, and the second N-type doping. The doping concentration of the impurity region 32 is greater than the doping concentration of the N region 12 to ensure the bandwidth of the phase modulator on the basis of reducing the optical transmission loss of the phase modulator.

On the basis of the above embodiments, in one embodiment of the present application, the second P-type doping region 22 is in a direction parallel to the first P-type doping region 21 to the P region 11. The doping concentration is gradually reduced to reduce the optical transmission loss due to the carrier absorption effect in the phase modulator. Specifically, in one embodiment of the present application, the doping concentration of the second P-type doping region 22 is uniform in a direction parallel to the first P-type doping region 21 to the P region 11. The decrease is such that the second P-type doping region 22 has less influence on the resistance value of the P-type doping region 2, and does not have an excessive influence on the bandwidth of the phase modulator.

Similarly, based on any of the above embodiments, in one embodiment of the present application, the second N is in a direction parallel to the first N-type doping region 31 to the N region 12. The doping concentration of the doped region 32 is gradually reduced to reduce the optical transmission loss due to the carrier absorption effect in the phase modulator. Specifically, in one embodiment of the present application, the doping concentration of the second N-type doping region 32 is uniform in a direction parallel to the first N-type doping region 31 to the N region 12 The decrease is such that the second N-type doping region 32 has a small influence on the resistance value of the N-type doping region 3, and does not have an excessive influence on the bandwidth of the phase modulator.

On the basis of any of the above embodiments, in an embodiment of the present application, as shown in FIG. 2, the phase modulator further includes:

Covering the P-type doping region 2, the N-type doping region 3, and the first insulating layer 4 of the PN junction structure 1, the first insulating layer 4 having a first via hole and a second via hole ;

a first electrode 5 electrically connected to the first P-type doping region 21 through the first via hole;

a second electrode 6 electrically connected to the first N-type doping region 31 through the second via hole;

a second insulating layer 7 on the side of the PN junction structure 1, the P-type doping region 2 and the N-type doping region 3 facing away from the first insulating layer 4;

a silicon substrate 8 on the side of the second insulating layer 7 facing away from the PN junction structure 1, the P-type doping region 2 and the N-type doping region 3;

The first electrode 5 is used for electrically connecting the driving circuit and the first P-type doping region 21, and the second electrode 6 is for electrically connecting the driving circuit and the first N-type doping region 31, The second insulating layer 7 is used to isolate the silicon substrate 8 and a structure located above the second insulating layer 7.

On the basis of the above embodiments, in one embodiment of the present application, the doping concentration of the first P-type doping region 21 is on the order of 1*10 ²⁰ to ensure the first P-type doping region 21 Good electrical contact with the first electrode 5 to achieve good electrical contact of the first P-doped region 21 and the driver circuit. Similarly, the doping concentration of the first N-type doping region 31 is on the order of 1*10 ²⁰ to ensure good electrical contact between the first N-type doping region 31 and the second electrode 6, thereby realizing Good electrical contact of the first N-type doped region 31 with the driver circuit.

In the embodiment of the present application, the phase modulator changes the effective refractive index in the PN junction structure 1 by changing the carrier concentration in the PN junction structure 1 by applying a driving signal, thereby realizing an optical signal. Phase modulation, and the modulation efficiency of the phase modulator increases as the carrier concentration in the PN junction structure 1 increases, and therefore, in one embodiment of the present application, based on any of the above embodiments The doping concentration of the P region 11 is on the order of 1*10 ¹⁷ -1*10 ¹⁸ to reduce the optical transmission loss of the phase modulator while ensuring the modulation efficiency of the phase modulator.

Correspondingly, the embodiment of the present application further provides a silicon-based electro-optic modulator, as shown in FIG. 3, the silicon-based electro-optic modulator includes: a first optical coupler 100 electrically connected to an input terminal for inputting light The signal is divided into two optical signals of the first optical signal and the second optical signal, and the first optical waveguide 200 that is connected to the first optical coupler 100 to transmit the first optical signal is connected to the first optical coupler 100. a second transmission waveguide 300 transmitting the second optical signal, a first phase modulator 400 connected to the first transmission waveguide 200, and a second phase modulator 500 connected to the second transmission waveguide 300, a third transmission waveguide 600 connected to the first phase modulator 400, a fourth transmission waveguide 700 connected to the second phase modulator 500, and connected to the third transmission waveguide 600 and the fourth transmission waveguide 700 The second optical coupler 800. The first phase modulator 400 and the second phase modulator 500 are phase modulators provided by any of the above embodiments of the present application.

In a specific operation, the first optical coupler 100 is configured to divide an input optical signal into a first optical signal and a second optical signal, where the first transmission waveguide 200 is configured to transmit the first optical signal to the first a phase modulator 400, the first phase modulator 400 modulates the first optical signal and outputs the same to the third transmission waveguide 600, and outputs the third transmission waveguide 600 to the second optical coupling The second transmission waveguide 300 is configured to output the second optical signal to the second phase modulator 500, and the second phase modulator 500 modulates the second optical signal and outputs the same The fourth transmission waveguide 700 is output to the second optical coupler 800 via the fourth transmission waveguide 700, and the second optical coupler 800 is configured to transmit the third transmission waveguide 600 and the fourth transmission The optical signals output from the waveguide 700 are combined and output.

It can be seen from the above that the phase modulator provided by the embodiment of the present application, the silicon-based electro-optic modulator including the phase modulator, divides the P-type doping region 2 into the first P-type doping region 21 and The second P-type doping region 22 has two portions, wherein a doping concentration of the second P-type doping region 22 is smaller than a doping concentration of the first P-type doping region 21, thereby utilizing the first The heavily doped concentration of a P-type doped region 21 achieves the phase modulator and drive Good electrical contact of the moving circuit, and using the second P-type doping region 22 to reduce the doping concentration of the P-type doping region 2 near the PN junction structure 1 side, reducing the phase modulator Optical transmission loss, which in turn reduces the optical transmission loss of the silicon-based electro-optic modulator. Meanwhile, the phase modulator provided by the embodiment of the present application and the silicon-based electro-optic modulator including the phase modulator divide the N-type doping region 3 into the first N-type doping region 31 and the Two portions of the second N-type doping region 32, wherein a doping concentration of the second N-type doping region 32 is smaller than a doping concentration of the first N-type doping region 31, thereby utilizing the first N The heavily doped concentration of the doped region 31 achieves good electrical contact of the phase modulator with the drive circuit and utilizes the second N-type doped region 32 to reduce the N-type doped region 3 near the PN The doping concentration on the side of the junction structure 1 reduces the optical transmission loss of the phase modulator, thereby reducing the optical transmission loss of the silicon-based electro-optic modulator.

In addition, the embodiment of the present application further provides a method for fabricating a phase modulator. As shown in FIG. 4, the manufacturing method includes:

S10: as shown in FIG. 5, a silicon wafer is provided, the silicon wafer includes a silicon substrate 8, an isolation layer 7 on a surface of the silicon substrate 8, and a side of the isolation layer 7 facing away from the silicon substrate 8. Flat layer 9.

In an embodiment of the present application, the isolation layer is an insulating layer, such as a silicon dioxide layer, and the planar layer is a silicon material layer.

Specifically, in an embodiment of the present application, the method for forming a silicon wafer includes: providing a silicon substrate; forming an isolation layer on a surface of the silicon substrate; and facing the isolation layer from the silicon substrate The side surface forms a flat layer. The formation process of the isolation layer may be a deposition process or an oxidation process; the formation process of the planarization layer may also be a deposition process, which is not limited in this application, as the case may be.

S20: removing a portion of the flat layer 9 as shown in FIG. 6, forming a convex structure 10, the convex structure 10 including a first surface and second and third surfaces respectively located on opposite sides of the first surface The first surface is higher than the second surface and the third surface.

Specifically, in an embodiment of the present application, a part of the flat layer is removed to form a convex structure, and the convex structure includes a first surface and a second surface and a third surface respectively located on two sides of the first surface a surface, the first surface being higher than the second surface and the third surface comprising:

Forming a first capping layer on a surface of the flat layer, the first capping layer covering a region where the PN junction structure is to be formed, exposing a region where the P-type doping region and the N-type doping region are to be formed;

Etching the flat layer with the first cover layer as a mask to form a convex structure, the raised structure comprising a first surface and a second surface respectively located on opposite sides of the first surface and a third surface, the first surface being higher than the second surface and the third surface, wherein the first surface corresponds to a region where the PN junction structure is to be formed, and the second surface corresponds to a portion to be formed A region of the P-type doped region, the second surface corresponding to a region where the N-type doped region is to be formed.

S30: forming a PN junction structure in the first surface, the PN junction structure including oppositely disposed P regions and N regions and a PN junction between the P region and the N region.

Specifically, in an embodiment of the present application, a PN junction structure is formed in the first surface, the PN junction structure includes oppositely disposed P regions and N regions, and is located in the P region and the N region. The PN junction between:

As shown in FIG. 7, a second cover layer 20 is formed on a side of the flat layer 9 facing away from the isolation layer 7, a second cover layer 20 covering a portion of the second surface, the third surface, and a portion of the first surface in which the N region is to be formed, exposing a portion of the first surface where the P region is to be formed, and a portion of the second surface to be formed into the second P-type doped region;

As shown in FIG. 8, using the second cover layer 20 as a mask, forming the P region in the first surface;

As shown in Figure 9, the first cover layer 10 is removed;

As shown in FIG. 10, a third cover layer 30 is formed on a side of the flat layer 9 facing away from the isolation layer 7, the third cover layer 30 covering the second surface, a portion of the third surface, and the Forming a portion of the P region in the first surface, exposing a portion of the first surface where the N region is to be formed, and a portion of the third surface where the second N-type doping region is to be formed;

As shown in FIG. 11 and FIG. 12, with the third cover layer 30 as a mask, the N region 12 is formed in a portion of the first surface where the N region is to be formed, and the P region and the N region are Forming the PN junction 13 at a boundary;

The third cover layer 30 is removed.

It should be noted that, in the foregoing embodiment of the present application, the order of forming the P zone and the N zone may be interchanged, which is not limited in this application, as the case may be.

S40: forming a first P-type doping region in the second surface, the doping concentration of the first P-type doping region being greater than the doping concentration of the P region.

Specifically, in an embodiment of the present application, forming the first P-type doping region in the second surface includes:

As shown in FIG. 13, a fourth cover layer 40 is formed on the surface of the flat layer 9, the fourth cover layer covering the first surface, the third surface and a portion of the second surface, only exposing the a portion of the second surface to be formed into the first P-type doped region;

As shown in FIG. 14, the fourth P-type doped region is formed on the second surface, and the first P-type doped region 21 is formed on the second surface. The formation process of the first P-type doping region is ion implantation, and the implanted ions are boron.

As shown in Figure 15, the fourth cover layer 40 is removed.

S50: forming a first N-type doping region in the third surface, wherein a doping concentration of the first N-type doping region is greater than a doping concentration of the N region.

Specifically, in an embodiment of the present application, forming the first N-type doping region in the third surface includes:

As shown in FIG. 16, a fifth cover layer 50 is formed on the surface of the flat layer 9, the fifth cover layer 50 covering the first surface, the second surface and a portion of the third surface, only exposed a portion of the third surface to be formed into the first N-type doped region;

As shown in FIG. 17, the first N-type doped region is formed on a portion of the third surface where the first N-type doping region is to be formed, using the fifth capping layer as a mask. An N-type doped region is formed by ion implantation, and the implanted ions are phosphorus;

As shown in FIG. 18, the fifth cover layer 50 is removed.

It should be noted that, in the foregoing embodiment of the present application, the order of forming the first P-type doping region and the first N-type doping region may be interchanged, which is not limited in this application. Depending on the situation.

S60: forming a second P-type doped region in the second surface, and forming a second N-type in the third surface a doped region, wherein the second P-type doped region is between the first P-type doped region and the P region, and a doping concentration of the second P-type doped region is less than a doping concentration of the first P-type doping region; the second N-type doping region is between the first N-type doping region and the N region, and the second N-type doping region The doping concentration is less than the doping concentration of the first N-type doping region.

On the basis of the above embodiments, in one embodiment of the present invention, the doping of the second P-type doping region is in a direction parallel to the first P-type doping region to the P region. The concentration gradually decreases; the doping concentration of the second N-type doped region gradually decreases in a direction parallel to the first N-type doped region to the N region.

In an embodiment of the present application, in a second embodiment of the present application, forming a second P-type doped region in the second surface, and forming a second N-type doped region in the third surface includes :

As shown in FIG. 19, a first mask layer 60 is formed on the first surface of the bump structure, wherein the forming process of the first mask layer may include deposition and etching;

As shown in FIG. 20, a sidewall structure 70 is formed on a side of the convex structure facing the second surface and the third surface, and a projection and a projection of the sidewall structure 70 on the flat layer 9 The first P-type doped regions 21 do not overlap and do not overlap the first N-type doped regions 31, wherein, at the second surface, along the first P-type doped regions The thickness of the sidewall structure gradually increases in a direction to the P region; at the third surface, in a direction parallel to the first N-type doping region to the N region, the side The thickness of the wall structure is gradually increased;

As shown in FIG. 21, a second mask layer 80 is formed on a side of the sidewall structure 70 facing away from the flat layer 9, the second mask layer 80 covering the third surface, the first surface And the first P-type doping region 21, exposing the portion of the sidewall structure 70 at the second surface, wherein the forming process of the second mask layer may include depositing and etching;

As shown in FIG. 22, using the second mask layer 80 as a mask, a second P-type doped region 22 is formed in a region of the second surface below the sidewall spacer 70, the second The formation process of the P-type doping region is ion implantation, and the implanted ions are boron;

As shown in Figure 23, the second mask layer 80 is removed;

As shown in FIG. 24, a third mask layer 90 is formed on a side of the sidewall structure 70 facing away from the flat layer 9, the third mask layer 90 covering the second surface, the first surface And the first N-type doping region 31 exposing a portion of the sidewall structure 70 at the third surface;

As shown in FIG. 25, using the third mask layer 90 as a mask, a second N-type doping region 32 is formed in a region of the third surface below the sidewall structure 70, the second The formation process of the N-type doping region is ion implantation, and the implanted ions are phosphorus;

The material of the first mask layer and the second mask layer are different, and the materials of the first mask layer and the third mask layer are different. Specifically, in an embodiment of the present application, the material of the first mask layer is silicon nitride, germanium or silicon oxynitride, and the material of the second mask layer is silicon dioxide, the third The material of the mask layer is silicon dioxide, but the present application does not limit this, as long as the materials of the first mask layer and the second mask layer are different.

In addition, in the embodiment of the present application, after the forming the second N-type doping region 32, the method further includes:

As shown in FIG. 26, the third mask layer 90, the sidewall structure 70, and the first mask layer are sequentially removed. 60.

It should be noted that, in the embodiment of the present application, the order of forming the second P-type doping region and the second N-type doping region may be interchanged, which is not limited in this application, as the case may be. And set.

In the embodiment of the present application, due to the region of the second surface where the second P-type doping region is to be formed, the direction along the first P-type doping region to the PN junction structure, the side The thickness of the wall structure is gradually increased. Therefore, when the second P-type doped region is formed in the second surface by using the sidewall structure and the second mask layer as a mask, the edge can be made The doping concentration of the second P-type doped region gradually decreases in a direction from the first P-type doping region to the PN junction structure.

Similarly, due to the region of the third surface where the second N-type doping region is to be formed, the thickness of the sidewall structure along the direction of the first N-type doping region to the PN junction structure Gradually increasing, therefore, when the second N-type doped region is formed in the third surface by using the sidewall structure and the third mask layer as a mask, the first along the first The doping concentration of the second N-type doped region gradually decreases from the N-type doped region to the direction of the PN junction structure.

It should be noted that, in an embodiment of the present application, the manufacturing method further includes:

Forming a first insulating layer covering the protruding structure, the first insulating layer having a first through hole and a second through hole therein;

Forming a first electrode electrically connected to the first P-type doping region through the first via hole;

Forming a second electrode electrically connected to the first N-type doping region through the second via hole;

Wherein the first electrode is for electrically connecting the driving circuit and the first P-type doping region, and the second electrode is for electrically connecting the driving circuit and the first N-type doping region.

In summary, the phase modulator fabricated by the method for fabricating the phase modulator provided by the embodiment of the present application divides the P-type doped region into the first P-type doped region and the second P-type. Two portions of the doped region, wherein a doping concentration of the second P-type doping region is smaller than a doping concentration of the first P-type doping region, thereby utilizing re-doping of the first P-type doping region The impurity concentration achieves good electrical contact between the phase modulator and the driving circuit, and utilizes the second P-type doping region to reduce the doping concentration of the P-type doping region near the side of the PN junction structure, and reduce The optical transmission loss of the phase modulator, which in turn reduces the optical transmission loss of the silicon-based electro-optic modulator. Meanwhile, the phase modulator fabricated by the phase modulator manufacturing method provided by the embodiment of the present application further divides the N-type doping region into the first N-type doping region and the second N-type doping region. a two-part, wherein a doping concentration of the second N-type doping region is smaller than a doping concentration of the first N-type doping region, thereby realizing utilizing a heavily doped concentration of the first N-type doping region The phase modulator is in good electrical contact with the driving circuit, and uses the second N-type doping region to reduce the doping concentration of the N-type doping region near the side of the PN junction structure, and reduce the phase The optical transmission loss of the modulator, which in turn reduces the optical transmission loss of the silicon-based electro-optic modulator.

It should be noted that, in the manufacturing method of the phase modulator provided in the embodiment of the present application, the forming process of each component structure is widely applied to the fabrication of a CMOS (Complementary Metal Oxide Semiconductor), and therefore, the present application The fabrication method of the phase modulator provided by the embodiment has high stability and reliability. Moreover, the manufacturing process and the tradition of the phase modulator provided by the embodiment of the present application The VLSI CMOS process is compatible and requires no special processes, which facilitates large-scale manufacturing and cost reduction of the device.

Each part of this manual is described in a progressive manner. Each part focuses on the differences from other parts. The same similar parts between the parts can be referred to each other.

The above description of the disclosed embodiments enables those skilled in the art to make or use the application. Various modifications to these embodiments are obvious to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application is not limited to the embodiments shown herein, but the broadest scope consistent with the principles and novel features disclosed herein.

Claims

A phase modulator, comprising:

a PN junction structure, the PN junction structure including oppositely disposed P regions and N regions; and a PN junction between the P region and the N region;

a P-type doped region electrically connected to the P region, the P-type doped region includes a first P-type doped region and a second P-type doped region, wherein the second P-type doped region is located Between the P region and the first P-type doped region, and a doping concentration of the first P-type doped region is greater than a doping concentration of the second P-type doped region;

An N-type doped region electrically connected to the N region, the N-type doped region includes a first N-type doped region and a second N-type doped region, wherein the second N-type doped region is located The doping concentration of the first N-type doping region is greater than the doping concentration of the second N-type doping region.
The phase modulator according to claim 1, wherein a doping concentration of the second P-type doping region is greater than a doping concentration of the P region; and a doping of the second N-type doping region The concentration is greater than the doping concentration of the N region.
The phase modulator according to claim 1 or 2, wherein the doping of the second P-type doping region is in a direction parallel to the first P-type doping region to the P region The concentration gradually decreases.
The phase modulator according to claim 1 or 2, wherein the doping of the second N-type doping region is in a direction parallel to the first N-type doping region to the N region The concentration gradually decreases.
The phase modulator according to claim 1, wherein a doping concentration of said first P-type doping region and said first N-type doping region is on the order of 1*10 20 , said P region and The doping concentration of the N region is on the order of 1*10 17 -1*10 18 .
A silicon-based electro-optic modulator comprising the phase modulator of any of claims 1-5.
A method for fabricating a phase modulator, comprising:

Providing a silicon wafer, the silicon wafer comprising a silicon substrate, an isolation layer on a surface of the silicon substrate, and a planar layer on a side of the isolation layer facing away from the silicon substrate;

Removing a portion of the planar layer to form a raised structure, the raised structure comprising a first surface and a second surface and a third surface on opposite sides of the first surface, the first surface being higher than the second a surface and the third surface;

Forming a PN junction structure in the first surface, the PN junction structure including oppositely disposed P regions and N regions; and a PN junction between the P region and the N region;

Forming a first P-type doping region in the second surface, a doping concentration of the first P-type doping region being greater than a doping concentration of the P region;

Forming a first N-type doping region in the third surface, the doping concentration of the first N-type doping region being greater than a doping concentration of the N region;

Forming a second P-type doped region in the second surface, and forming a second N-type doped region in the third surface, wherein the second P-type doped region is located in the first P Between the doped region and the P region, and the doping concentration of the second P-doped region is less than the doping concentration of the first P-type doped region; the second N-type doped region Located between the first N-type doped region and the N region, and the doping concentration of the second N-type doped region is less than a doping concentration of the first N-type doped region.
The fabrication method according to claim 7, wherein the doping concentration of the second P-type doping region is gradually decreased in a direction parallel to the first P-type doping region to the P region. The doping concentration of the second N-type doping region gradually decreases in a direction parallel to the first N-type doping region to the N region.
The method according to claim 8, wherein forming a second P-type doped region in the second surface and forming a second N-type doped region in the third surface comprises:

Forming a first mask layer on the first surface of the raised structure;

Forming a sidewall structure on a side of the convex structure facing the second surface and the third surface, a projection of the sidewall structure on the flat layer and the first P-type doping region not Overlapped and not overlapping the first N-type doped region;

Forming a second mask layer on a side of the sidewall structure facing away from the planar layer, the second mask layer covering the third surface, the first surface, and the first P-type doped region Exposing a portion of the sidewall structure at the second surface;

Forming a second P-type doped region in a region of the second surface below the sidewall structure, using the second mask layer as a mask;

Removing the second mask layer;

Forming a third mask layer on a side of the sidewall structure facing away from the planar layer, the third mask layer covering the second surface, the first surface, and the first N-type doped region Exposing a portion of the side wall structure at the third surface;

Forming a second N-type doped region in a region of the third surface below the sidewall structure by using the third mask layer as a mask;

The material of the first mask layer and the second mask layer are different, and the materials of the first mask layer and the third mask layer are different.
The method according to claim 9, wherein the material of the first mask layer is silicon nitride, germanium or silicon oxynitride.