阅读说明：本技术 铌酸锂单晶薄膜芯片及其制作方法 (Lithium niobate single crystal thin film chip and manufacturing method thereof ) 是由 周赤 吉贵军 刘昆 张大鹏 王兴龙 于 2020-12-07 设计创作，主要内容包括：本发明提供一种铌酸锂单晶薄膜芯片及其制作方法。制作方法包括在支撑晶圆上依次制备介质层和铌酸锂薄层；对介质层与铌酸锂薄层之间的键合界面进行缺陷检测；分析并记录二维尺寸大于预先设定值的缺陷的位置；在缺陷的周围设置隔离槽,隔离槽在周向上包围缺陷,隔离槽的深度大于或等于铌酸锂薄层的厚度。通过该制作方法制作的铌酸锂单晶薄膜芯片不仅能够有效地防止缺陷的扩大和扩散,而且能够有效地释放大片铌酸锂薄层在晶圆上的应力积累。(The invention provides a lithium niobate single crystal thin film chip and a manufacturing method thereof. The manufacturing method comprises the steps of sequentially preparing a dielectric layer and a lithium niobate thin layer on a support wafer; detecting the defects of the bonding interface between the dielectric layer and the lithium niobate thin layer; analyzing and recording the position of the defect with the two-dimensional size larger than a preset value; and arranging an isolation groove around the defect, wherein the isolation groove surrounds the defect in the circumferential direction, and the depth of the isolation groove is greater than or equal to the thickness of the lithium niobate thin layer. The lithium niobate single crystal thin film chip manufactured by the manufacturing method not only can effectively prevent the defects from expanding and diffusing, but also can effectively release the stress accumulation of a large lithium niobate thin layer on the wafer.)

1. The method for manufacturing the lithium niobate single crystal thin film chip is characterized by comprising the following steps:

preparing a dielectric layer and a lithium niobate thin layer on a support wafer in sequence;

detecting the defects of the bonding interface between the dielectric layer and the lithium niobate thin layer;

analyzing and recording the position of the defect with the two-dimensional size larger than a preset value;

and arranging an isolation groove around the defect, wherein the isolation groove circumferentially surrounds the defect, and the depth of the isolation groove is greater than or equal to the thickness of the lithium niobate thin layer.

2. The method for producing a lithium niobate single crystal thin film chip according to claim 1, characterized in that:

and forming the isolation groove by adopting a surface scribing mode.

3. The method for producing a lithium niobate single crystal thin film chip according to claim 2, characterized in that:

the surface scribing tool is a semiconductor wafer diamond cutter or a laser cutter.

4. The method for producing a lithium niobate single crystal thin film chip according to any one of claims 1 to 3, characterized in that:

the step of sequentially preparing the dielectric layer and the lithium niobate thin layer on the support wafer comprises the following steps:

and preparing the dielectric layer on the support wafer by a film plating or direct oxidation method, and polishing the surface of the dielectric layer.

5. The method for producing a lithium niobate single crystal thin film chip according to claim 4, characterized in that:

the refractive index of the material of the dielectric layer is smaller than that of the lithium niobate material.

6. The method for producing a lithium niobate single crystal thin film chip according to claim 4, characterized in that:

the step of sequentially preparing the dielectric layer and the lithium niobate thin layer on the support wafer comprises the following steps:

injecting ions into the optical-level surface of a raw material lithium niobate wafer, wherein the ions penetrate through the optical-level surface to form an ion layer, the ion layer divides the raw material lithium niobate wafer into a raw material lithium niobate wafer main body and the lithium niobate thin layer, and the surface of the lithium niobate thin layer is polished;

and bonding the lithium niobate thin layer with the dielectric layer.

7. The method for producing a lithium niobate single crystal thin film chip according to claim 6, characterized in that:

after bonding the lithium niobate thin layer with the dielectric layer, the step of sequentially preparing the dielectric layer and the lithium niobate thin layer on the support wafer further comprises:

heating to a first preset temperature;

and heating to a second preset temperature, so that the lithium niobate thin layer is separated from the raw material lithium niobate wafer main body and is left on the dielectric layer, wherein the second preset temperature is higher than the first preset temperature.

8. The method for producing a lithium niobate single crystal thin film chip according to claim 7, characterized in that:

the first preset temperature is 200 ℃ to 230 ℃, and the second preset temperature is 250 ℃ to 350 ℃.

9. The method for producing a lithium niobate single crystal thin film chip according to any one of claims 1 to 3, characterized in that:

the step of detecting the defects of the bonding interface between the dielectric layer and the lithium niobate thin layer comprises the following steps:

and detecting the defects of the bonding interface by adopting an optical microscope, and recording the imaging of the bonding interface by adopting a scanning mode.

10. A lithium niobate single crystal thin film chip produced by the production method according to any one of claims 1 to 9;

the lithium niobate single crystal thin film chip comprises a lithium niobate thin layer, a dielectric layer and a support wafer which are sequentially arranged in a laminated mode, wherein an isolation groove is formed in the periphery of a defect on a bonding interface between the dielectric layer and the lithium niobate thin layer, and the isolation groove circumferentially surrounds the defect.

Technical Field

The invention relates to the field of photoelectric semiconductor materials, in particular to a lithium niobate single crystal thin film chip and a manufacturing method thereof.

Background

The lithium niobate single crystal has excellent transmission performance, electro-optic performance, nonlinear optical performance and piezoelectric performance, and is widely applied to optical communication, data center optical interconnection and high-frequency filtering devices. The nanometer thin film lithium niobate single crystal on other material substrate has the excellent characteristics, and can be used for integrated devices, which is a novel hopeful integrated optical material. However, growing lithium niobate single crystal thin films on other substrate materials has proven difficult to achieve, whereas mechanical slicing techniques have difficulty in producing thin films of nanometer-scale thickness.

The lithium niobate single crystal film prepared by using Smart-Cut technology in recent years makes the mass production of thin film lithium niobate wafers possible. The method comprises the following general steps: firstly, polishing the surface of a raw material lithium niobate wafer to meet the requirements of wafer bonding, simultaneously preparing another carrier wafer, such as a silicon (Si) wafer, preparing a buffer layer, such as silicon dioxide (SiO2), on the carrier wafer, polishing to enable the buffer layer to meet the requirements of wafer bonding, then performing ion implantation with specific energy and specific measurement, such as helium ions (He +), on the polished surface of the raw material lithium niobate wafer, then bonding the polished surface of the raw material wafer and the polished surface of the carrier wafer, heating the two wafers after bonding to enable the implanted ions to be compounded into micro bubbles, separating the raw material lithium niobate wafer after expansion, and leaving a lithium niobate film on the carrier wafer.

In the method for preparing the lithium niobate thin film wafer, the bonding between the lithium niobate wafer and the medium film layer on the bearing wafer is realized by the attractive action of Van der Waals force between two extremely flat bonding surfaces which are very close to each other. While such an extremely flat bonding surface is an ideal condition, in practice, due to the limitation of grinding and polishing processes, there are individual parts that cannot reach the extremely flat condition, so that the two bonded surfaces cannot be close enough, and van der waals force cannot exert attractive force. Such defects are manifested as voids (void) in the wafer bonding interface, which may be further enlarged by external or internal factors such as heat, pressure, stress, etc. during subsequent processing steps, resulting in larger areas of gaps or separation zones in the wafer bonding surface.

The subsequent fabrication of the optical waveguide is based on this bonding interface and can damage the optical waveguide structure if the bonding is incomplete or if there is a separation zone. Therefore, how to ensure the bonding quality of the interface and effectively prevent the separation and the cracking of the bonding surface caused by the expansion of the gap of the bonding surface is always a key factor influencing the bonding yield of the wafer. And many factors causing the defect expansion and diffusion are caused by the chip manufacturing process, and how to take measures to ensure that the defect expansion risk is reduced in the manufacturing process of the lithium niobate photonic chip is very important for improving the chip manufacturing yield.

Disclosure of Invention

A first object of the present invention is to provide a method for manufacturing a lithium niobate single crystal thin film chip, which can effectively prevent the enlargement and diffusion of defects and can effectively release the stress accumulation of a large lithium niobate thin layer on a wafer.

The second object of the present invention is to provide a lithium niobate single crystal thin film chip produced by the above production method.

In order to achieve the first object, the invention provides a method for manufacturing a lithium niobate single crystal thin film chip, which comprises the steps of sequentially preparing a dielectric layer and a lithium niobate thin layer on a support wafer; detecting the defects of the bonding interface between the dielectric layer and the lithium niobate thin layer; analyzing and recording the position of the defect with the two-dimensional size larger than a preset value; and arranging an isolation groove around the defect, wherein the isolation groove surrounds the defect in the circumferential direction, and the depth of the isolation groove is greater than or equal to the thickness of the lithium niobate thin layer.

According to the scheme, before the wafer enters the chip manufacturing process, the isolation groove is used for isolating the defect area between the lithium niobate thin layer and the dielectric layer, so that the optical waveguide can be effectively prevented from being damaged due to the expansion and diffusion of the defect, and meanwhile, the stress accumulation of a large lithium niobate thin layer on the wafer can be effectively released. The manufacturing method can enable the lithium niobate single crystal thin film chip to bear the influence of more external force, temperature and other factors in the processes of photoetching, cleaning, baking, etching and the like, prevent the reduction of the yield of the chip caused by the expansion and diffusion of defects, and simultaneously avoid the quality and reliability risks brought to the final product by the recessive defects in the finished product of the chip.

Preferably, the isolation groove is formed by surface scoring.

In a further aspect, the surface scribing tool is a semiconductor wafer diamond cutter or a laser cutter.

In a preferred embodiment, the step of sequentially preparing the dielectric layer and the lithium niobate thin layer on the support wafer comprises: preparing a dielectric layer on a support wafer by a film plating or direct oxidation method, and polishing the surface of the dielectric layer.

Further, the refractive index of the material of the dielectric layer is smaller than that of the lithium niobate material.

Therefore, the refractive index of the material of the dielectric layer is smaller than that of the lithium niobate material, so that the lithium niobate waveguide is formed.

The further scheme is that the step of sequentially preparing the dielectric layer and the lithium niobate thin layer on the support wafer comprises the following steps: injecting ions into the optical-grade surface of the raw material lithium niobate wafer, forming an ion layer after the ions penetrate through the optical-grade surface, dividing the raw material lithium niobate wafer into a raw material lithium niobate wafer main body and a lithium niobate thin layer by the ion layer, and polishing the surface of the lithium niobate thin layer; and bonding the lithium niobate thin layer with the dielectric layer.

Therefore, the surface of the raw material lithium niobate wafer implanted with ions, namely the surface of the lithium niobate thin layer, is optically polished to remove surface unevenness possibly caused by ion bombardment, so that the requirement of wafer bonding is met.

The further scheme is that the step of sequentially preparing the dielectric layer and the lithium niobate thin layer on the support wafer after bonding the lithium niobate thin layer and the dielectric layer further comprises the following steps: heating to a first preset temperature; and heating to a second preset temperature to separate the lithium niobate thin layer from the raw material lithium niobate wafer main body and store the lithium niobate thin layer on the dielectric layer, wherein the second preset temperature is higher than the first preset temperature.

In a further embodiment, the first predetermined temperature is 200 ℃ to 230 ℃ and the second predetermined temperature is 250 ℃ to 350 ℃.

Therefore, the bonded combined wafer is heated to the first preset temperature, so that the bonding surface is sufficiently annealed and strengthened. And then heating the bonded combined wafer to a second preset temperature to gasify the implanted ions, so that an ion implantation layer in the raw material lithium niobate wafer cracks, the main body of the raw material lithium niobate wafer is separated from the combined wafer, and a layer of single crystal lithium niobate thin layer is left on the surface of the support crystal.

In a preferred embodiment, the step of detecting defects of the bonding interface between the dielectric layer and the lithium niobate thin layer includes: and detecting the defects of the bonding interface by adopting an optical microscope, and recording the imaging of the bonding interface by adopting a scanning mode.

In order to achieve the second object, the present invention provides a lithium niobate single crystal thin film chip manufactured by the above manufacturing method, the lithium niobate single crystal thin film chip includes a lithium niobate thin layer, a dielectric layer, and a support wafer, which are sequentially stacked, an isolation groove is provided around a defect on a bonding interface between the dielectric layer and the lithium niobate thin layer, and the isolation groove surrounds the defect in a circumferential direction.

Drawings

FIG. 1 is a flowchart of steps S11 to S16 in an embodiment of the method for manufacturing a lithium niobate single crystal thin film chip of the present invention.

FIG. 2 is a flowchart of steps S17 to S12 in an embodiment of the method for manufacturing a lithium niobate single crystal thin film chip of the present invention.

FIG. 3 is a schematic structural diagram of a bonded wafer in an embodiment of the method for manufacturing a lithium niobate single crystal thin film chip according to the present invention.

FIG. 4 is a schematic structural diagram of an embodiment of a lithium niobate single crystal thin film chip of the present invention.

FIG. 5 is a schematic view showing defects and isolation trenches observed on the surface of an embodiment of a lithium niobate single crystal thin film chip of the present invention.

The invention is further explained with reference to the drawings and the embodiments.

Detailed Description

Referring to fig. 1 to 3, when the method for manufacturing a lithium niobate single crystal thin film chip is performed, step S11 is first performed to prepare a dielectric layer 2 on a support wafer 1 by plating or direct oxidation. The refractive index of the material of the dielectric layer 2 is smaller than that of the lithium niobate material, and the material of the dielectric layer 2 in this embodiment is silicon dioxide.

Then, step S12 is performed to perform an optical polishing process on the surface of the dielectric layer 2 as the buffer layer, so as to obtain a very smooth optical plane.

Then, step S13 is executed to implant ions into the optical-level surface of the raw material lithium niobate wafer 3, and the ions penetrate the optical-level surface and stay at a predetermined depth on the wafer surface, so as to form an ion layer 4, and the ion layer 4 separates the raw material lithium niobate wafer 3 into a raw material lithium niobate wafer main body 5 and a lithium niobate thin layer 6. The thickness of the lithium niobate thin layer 6 is determined by ion energy, usually 500 nm to 1000 nm, and the injected ions must have a sufficiently narrow energy distribution so that the ions enter the surface of the raw material lithium niobate wafer 3 and then stay in a certain narrow depth range through material deceleration, and helium ions (He +) are used as the ions in this embodiment.

Then, step S14 is executed, after ion implantation is completed, optical polishing is performed on the dielectric layer 2 to remove surface unevenness possibly caused by ion bombardment, so as to meet the requirement of wafer bonding.

Then, step S15 is performed to perform wafer bonding on the lithium niobate thin layer 6 and the dielectric layer 2.

Then, step S16 is executed to heat the bonded wafer to a first predetermined temperature, where the first predetermined temperature is 200 ℃ to 230 ℃, so that the bonding interface 60 between the lithium niobate thin layer 6 and the dielectric layer 2 is sufficiently annealed and strengthened.

And step S17 is executed to heat the bonded united wafer to a second preset temperature, where the second preset temperature is 250 to 350 ℃, so that the injected ions are gasified and polymerized into micro-bubbles, and under the action of the micro-bubbles, the ionic layer 4 is separated at the raw material lithium niobate wafer main body 5, and the lithium niobate thin layer 6 with a specific thickness remains on the dielectric layer 2 of the support wafer 1.

Then, step S18 is performed to perform optical polishing treatment on the surface of the lithium niobate thin layer 6, so that the thickness and the surface finish thereof meet the requirements of the optical waveguide.

Then, step S19 is executed to perform defect detection on the bonding interface 60 between the dielectric layer 2 and the lithium niobate thin layer 6 by using an optical microscope. The bonding defects 7 typically appear as localized voids or separations that can be observed under an optical microscope of sufficient magnification. For large area wafers, an image of the bonding interface 60 of the entire wafer may be recorded in a scanning fashion and the microscopic image recorded in a computer storage medium.

Then, step S20 is performed to analyze the recorded microscopic image, determine and record the positions of defects 7 having a two-dimensional size larger than a predetermined value, and simultaneously, map all the defects 7. The preset value is not more than the waveguide width of the photonic chip.

Then, step S21 is performed to divide the isolation groove 8 shown in fig. 5 around each of the defects 7 after detection, and the isolation groove 8 circumferentially surrounds the corresponding defect 7. The isolation trenches 8 separate the defects 7 from other non-defects 7. The determination of the position of the isolation trench 8 can be done by existing image processing software while making the isolation trench layout.

And finally, executing a step S22, performing surface scribing on the lithium niobate thin layer 6 according to the isolation groove layout, wherein the scribing depth is equal to the thickness of the lithium niobate thin layer 6, and realizing the isolation of the defect 7. The tool for surface scribing can be a semiconductor wafer diamond cutter or a laser cutter, and the scribing tool can be controlled by software and is carried out according to the isolation groove pattern generated in the previous process.

The lithium niobate single crystal thin film chip shown in fig. 4 is formed by the above manufacturing method, and includes the lithium niobate thin layer 6, the dielectric layer 2 and the support wafer 1 which are sequentially stacked, the isolation groove 8 is provided around the defect 7 on the bonding interface 60 between the dielectric layer 2 and the lithium niobate thin layer 6, and the isolation groove 8 surrounds the defect 7 in the circumferential direction.

The subsequent chip lithography process may have various methods, for example, when maskless lithography (e.g., electron beam or laser scanning lithography) is adopted, the scanning beam may be controlled according to the isolation trench layout, and selective exposure is performed. When mask photoetching is adopted, the process flow is not influenced, and only the separation area is not required to be cut in the subsequent cutting. Other processes after the lithography are not affected.

Therefore, before the wafer enters the chip manufacturing process, the isolation groove is used for isolating the defect area between the lithium niobate thin layer and the dielectric layer, so that the optical waveguide can be effectively prevented from being damaged due to the expansion and diffusion of the defect, and the stress accumulation of the large lithium niobate thin layer on the wafer can be effectively released. The manufacturing method can enable the lithium niobate single crystal thin film chip to bear the influence of more external force, temperature and other factors in the processes of photoetching, cleaning, baking, etching and the like, prevent the reduction of the yield of the chip caused by the expansion and diffusion of defects, and simultaneously avoid the quality and reliability risks brought to the final product by the recessive defects in the finished product of the chip.

The depth of the isolation groove can also be slightly larger than the thickness of the lithium niobate thin layer, and the difference between the depth of the isolation groove and the thickness of the lithium niobate thin layer is less than or equal to 100 nanometers. The above-described modifications also achieve the object of the present invention.

Finally, it should be emphasized that the above-described preferred embodiments of the present invention are merely examples of implementations, not limitations, and various changes and modifications may be made by those skilled in the art, without departing from the spirit and scope of the invention, and any changes, equivalents, improvements, etc. made within the spirit and scope of the present invention are intended to be embraced therein.