CN-121995661-A - Method for improving efficiency of electro-optic modulator and electro-optic modulator

CN121995661ACN 121995661 ACN121995661 ACN 121995661ACN-121995661-A

Abstract

The invention discloses a method for improving the efficiency of an electro-optic modulator and the electro-optic modulator, and belongs to the technical field of integrated photoelectrons. The method comprises the steps of firstly preparing a silicon optical device on an SOI wafer, inversely bonding the silicon optical device on a lithium niobate wafer to serve as a new substrate, then removing the original silicon substrate and thinning an oxygen-buried layer, and finally bonding a lithium niobate film on the thinned surface and preparing a modulation structure. According to the invention, the high-loss silicon substrate is replaced by the low-loss lithium niobate substrate, so that a symmetrical dielectric environment is constructed, and the problems of high radio frequency loss and mismatch of refractive indexes of microwaves and light waves in the prior art are effectively solved. The method obviously reduces microwave loss, realizes speed matching, greatly improves the modulation efficiency and bandwidth of the modulator, improves thermal stress matching, and improves the device yield.

Inventors

LI QINGYUN
LI HAISHENG
SHEN YUAN
ZHANG ZHENXING
ZHENG XUEYAN

Assignees

西湖大学光电研究院

Dates

Publication Date: 20260508
Application Date: 20260305

Claims (10)

1. A method of improving the efficiency of an electro-optic modulator comprising the steps of: providing a silicon-on-insulator (SOI) wafer and a lithium niobate wafer, wherein the SOI wafer comprises a silicon substrate layer, an oxygen-buried layer and a top silicon structure layer which are sequentially stacked; bonding one side of a top silicon structure layer of the SOI wafer with the surface of the lithium niobate wafer to enable the lithium niobate wafer to be a supporting substrate; Removing the silicon substrate layer of the SOI wafer, and thinning the buried oxide layer to form an isolation medium layer with a preset thickness; Bonding a lithium niobate film on the surface of the isolation medium layer; And manufacturing an optical waveguide and a modulation electrode on the lithium niobate thin film to form an electro-optical modulation structure.
2. A method of improving the efficiency of an electro-optic modulator according to claim 1, further comprising, prior to said bonding the SOI wafer to the lithium niobate wafer: Preparing a silicon optical function device on a top silicon structure layer of the SOI wafer in advance; The silicon optical function device comprises at least one of an optical coupler, a beam splitter, a beam combiner, a photodetector or a thermal modulator.
3. The method of claim 2, wherein bonding the top silicon structural layer side of the SOI wafer to the surface of the lithium niobate wafer comprises: And turning over the SOI wafer so that the back surface of the SOI wafer faces upwards, and bonding the SOI wafer to the surface of the lithium niobate wafer through the first dielectric layer.
4. A method of improving the efficiency of an electro-optic modulator as claimed in claim 1 wherein the method of removing the silicon substrate layer of the SOI wafer comprises one or a combination of mechanical lapping, chemical etching or dry etching.
5. The method for improving efficiency of an electro-optic modulator according to claim 1, wherein the step of thinning the buried oxide layer comprises: And thinning the oxygen buried layer to below 200nm by using a chemical mechanical polishing process, so that the light field coupling condition is met between the lithium niobate thin film and the top silicon structure layer below.
6. The method of claim 1, further comprising, after the step of bonding the lithium niobate film to the surface of the insulating dielectric layer: and carrying out high-temperature annealing treatment on the bonded wafer to enhance bonding strength and release stress.
7. A method for improving the efficiency of an electro-optic modulator according to claim 1, wherein the step of fabricating an optical waveguide on the lithium niobate film comprises: and etching the lithium niobate thin film through photoetching and etching processes to form a ridge waveguide structure, wherein the ridge waveguide structure is positioned in the area above the top silicon structure layer.
8. A method of improving the efficiency of an electro-optic modulator according to claim 1, further comprising, after forming the electro-optic modulation structure: Depositing a second dielectric layer as a protective layer on the electro-optic modulation structure; the protective layer, the isolation dielectric layer and the lithium niobate wafer jointly form a low microwave loss environment of the electro-optical modulation structure.
9. The method of claim 1, wherein the lithium niobate wafer and the lithium niobate thin film have a lattice constant and a thermal expansion coefficient that match, and the lithium niobate wafer has a low loss tangent characteristic.
10. An electro-optic modulator prepared by the method of any one of claims 1 to 9, comprising: a lithium niobate substrate; a silicon light device layer on the lithium niobate substrate; a thinned buried oxide layer located on the silicon optical device layer; The lithium niobate modulation layer is positioned on the thinned oxygen-buried layer and comprises a ridge waveguide and a modulation electrode; Wherein the silicon optical device layer is coated between the lithium niobate substrate and the thinned buried oxide layer.

Description

Method for improving efficiency of electro-optic modulator and electro-optic modulator Technical Field The invention belongs to the technical field of integrated photoelectrons, in particular to a method for improving the efficiency of an electro-optical modulator and the electro-optical modulator, and particularly relates to a method for improving the modulation efficiency and bandwidth of the electro-optical modulator based on a heterogeneous integration technology. Background The rapid development of Artificial Intelligence (AI) technology is leading the fourth industrial revolution, and optoelectronics sealing (CPO) technology has become a critical path for breaking through the network interconnection bottleneck of AI computing centers. In the optical-electrical interconnection system, the electro-optical modulator is used as a core device to bear the heavy duty of the conversion from an electric signal to an optical signal, and the bandwidth, the insertion loss, the power consumption and the integration level directly determine the overall performance of the optical communication system. Lithium Niobate On Insulator (LNOI) thin films are ideal materials for compact, low half-wave voltage and high bandwidth modulators due to their excellent electro-optic effect and large refractive index differences with surrounding materials. However, lithium Niobate (LN) materials are chemically inert and difficult to perform fine micro-nano etching, which greatly contributes to the manufacturing cost and process difficulty of lithium-full niobate modulators. In contrast, silicon-on-insulator (SOI) platforms have a mature CMOS compatible process, which is very easy to implement complex waveguide coupling, splitting/combining, detection and thermal modulation functions, but silicon materials themselves lack second order electro-optic effects. To combine the advantages of both, the prior art has widely adopted heterogeneous integration schemes that bond thin film lithium niobate to the surface of etched-formed SOI. The scheme utilizes silicon-based photon technology to treat passive and thermal modulation functions, and only utilizes a lithium niobate layer to realize electro-optic modulation. However, the buried oxide layer (Buried Oxide, BOX) of conventional SOI wafers is typically thin (e.g., 2-3 microns or even thinner) in thickness, which results in the Radio Frequency (RF) signal applied to the electro-optic modulator electrodes not being effectively isolated and thus leaking into the underlying silicon substrate. The silicon substrate has high dielectric constant and semiconductor characteristics, so that not only is huge radio frequency loss caused, but also serious mismatch between the refractive index of microwaves and the refractive index of optical wave groups is caused, thereby limiting the electro-optical interaction length and the high-frequency response efficiency of the modulator, and becoming a bottleneck for limiting the performance of a high-end optical module. Disclosure of Invention The application aims to solve the problems that the existing SOI-based heterogeneous integrated modulator cannot effectively isolate radio frequency signals from a high dielectric constant silicon substrate due to the limitation of the thickness of an oxygen burying layer, so that the speed mismatch of microwaves and light waves and the radio frequency loss are overlarge, the modulation efficiency and the bandwidth of a device are limited, and the like. In order to achieve the above-mentioned purpose, the application adopts the following technical scheme that a method for improving the efficiency of an electro-optical modulator comprises the following steps: Providing a silicon-on-insulator SOI wafer and a lithium niobate wafer, wherein the SOI wafer comprises a silicon substrate layer, an oxygen-buried layer and a top silicon structure layer which are sequentially laminated; Bonding one side of a top silicon structure layer of the SOI wafer with the surface of the lithium niobate wafer to enable the lithium niobate wafer to be a supporting substrate; Removing the silicon substrate layer of the SOI wafer, and thinning the buried oxide layer to form an isolation medium layer with a preset thickness; Bonding a lithium niobate film on the surface of the isolation medium layer; And manufacturing an optical waveguide and a modulation electrode on the lithium niobate film to form an electro-optic modulation structure. Further, before bonding the SOI wafer with the lithium niobate wafer, it further includes: pre-preparing a silicon optical function device on a top silicon structure layer of an SOI wafer; the silicon optical function device comprises at least one of an optical coupler, a beam splitter, a beam combiner, a photodetector, or a thermal modulator. Further, the step of bonding one side of the top silicon structure layer of the SOI wafer to the surface of the lithium niobate wafer specifically includes: And turning ov