阅读说明：本技术 一种Cap layer层蚀刻优化方法 (Cap layer etching optimization method ) 是由 王田瑞 王凤玲 成飞 于 2021-07-14 设计创作，主要内容包括：本发明公开了一种Cap layer层蚀刻优化方法,包括以下步骤：S1、准备全结构的外延片；S2、对所述外延片的N面进行翘曲补偿处理；S3、在所述外延片P面的Cap layer层上沉积一层光学膜；S4、将沉积有光学膜的外延片进行欧姆接触光刻,使光刻胶边缘具有倾角；S5、利用干法刻蚀,刻蚀掉所述光刻胶覆盖范围以外的光学膜；S6、进行欧姆接触金属沉积,将金属沉积在刻蚀掉的区域内,使沉积后的金属与所述光刻胶边缘的倾角和Cap layer层紧密接触；S7、使用SN830溶液去除所述光刻胶。通过该工艺方法,使沉积后的金属与光刻胶紧密贴合,避免SN830溶液对Cap layer层造成蚀刻现象,增大了选择比,方便控制蚀刻角度,提升芯片的良率并且极大程度地保护了芯片的性能。(The invention discloses a Cap layer etching optimization method, which comprises the following steps: s1, preparing an epitaxial wafer with a full structure; s2, carrying out warping compensation processing on the N surface of the epitaxial wafer; s3, depositing an optical film on the Cap layer of the P surface of the epitaxial wafer; s4, carrying out ohmic contact photoetching on the epitaxial wafer deposited with the optical film to enable the edge of the photoresist to have an inclination angle; s5, etching the optical film outside the coverage range of the photoresist by using dry etching; s6, depositing ohmic contact metal, depositing the metal in the etched area, and enabling the deposited metal to be in close contact with the inclination angle of the edge of the photoresist and the Cap layer; and S7, removing the photoresist by using an SN830 solution. By the process method, the deposited metal is tightly attached to the photoresist, so that the phenomenon that the SN830 solution etches the Cap layer is avoided, the selection ratio is increased, the etching angle is conveniently controlled, the yield of the chip is improved, and the performance of the chip is greatly protected.)

1. A Cap layer etching optimization method is characterized by comprising the following steps: the method comprises the following steps:

s1, preparing an epitaxial wafer with a full structure;

s2, carrying out warping compensation processing on the N surface of the epitaxial wafer;

s3, depositing an optical film on the Cap layer of the P surface of the epitaxial wafer;

s4, carrying out ohmic contact photoetching on the epitaxial wafer deposited with the optical film to enable the edge of the photoresist to have an inclination angle;

s5, etching the optical film outside the coverage range of the photoresist by using dry etching;

s6, depositing ohmic contact metal, depositing the metal in the etched area, and enabling the deposited metal to be in close contact with the inclination angle of the edge of the photoresist and the Cap layer;

and S7, removing the photoresist by using an SN830 solution.

2. The method for optimizing etching of a Cap layer according to claim 1, wherein: in step S4, the method for performing the ohmic contact lithography by making the edge of the photoresist have a tilt angle is as follows:

s41, performing a glue coating process on the epitaxial wafer by using a spin coater to ensure that the photoresist is at least 3um thick;

s42, exposing by using an exposure machine, wherein the exposure parameters are exposure dose 2500 and focal length 0;

and S43, developing the exposed epitaxial wafer by using a developing solution.

3. The method of claim 2, wherein the etching optimization method for the Cap layer comprises the following steps: the gluing process in step S41 includes the following steps:

s411, rapidly and rotationally coating a photoresist on the epitaxial wafer at a high rotating speed by using a spin coater to rapidly spread the photoresist;

s412, standing the epitaxial wafer which is spin-coated with the photoresist for 10S;

and S413, slowly rotating the epitaxial wafer at a low rotating speed by using a spin coater to enable the photoresist on the epitaxial wafer to be uniform.

4. The method of claim 3, wherein the etching optimization method for the Cap layer comprises the following steps: in the step S41, the high rotating speed is 3500-4000 r/S.

5. The method of claim 3, wherein the etching optimization method for the Cap layer comprises the following steps: in the step S43, the low rotating speed is 800-1200 r/S.

6. The method of claim 3, wherein the etching optimization method for the Cap layer comprises the following steps: the inclination angle of the edge of the photoresist is 70-80 degrees.

7. The method for optimizing etching of a Cap layer according to claim 1, wherein: the warpage compensation mode is to grow a stress film, and the stress film is made of SiO₂、SiN_XOr SiO_XN_y。

8. The method for optimizing etching of a Cap layer according to claim 1, wherein: the optical film is made of one or a composition of dielectric substances formed by Si, N, O, Al, F and Mg.

9. The method for optimizing etching of a Cap layer according to any one of claims 1 to 8, wherein: the metal material used for metal deposition is one or more of gold, titanium, silver, copper, chromium, manganese and germanium.

10. The method for optimizing etching of a Cap layer according to any one of claims 1 to 8, wherein: the epitaxial wafer with the full structure comprises a Cap layer, a P-DBR layer, an oxide layer, a quantum well layer, an N-DBR layer and a substrate from the P surface to the N surface, wherein the substrate is a GaAs single crystal substrate.

Technical Field

The invention relates to the technical field of chip preparation, in particular to a Cap layer etching optimization method.

Background

The VCSEL chip is manufactured by taking an epitaxial wafer as a base wafer and performing corresponding process flow on the epitaxial wafer. The epitaxial wafer consists of a Cap layer, a P-DBR, an N-DBR, an oxide layer, a quantum well and a substrate, and the reliability or the photoelectric characteristic of the chip can be influenced when any layer is damaged.

In the preparation process of the VCSEL chip, after the process steps of optical film deposition, photoetching, etching, metal deposition and the like are respectively carried out on the Cap layer of the epitaxial wafer, the SN830 solution is needed to be used for cleaning the epitaxial wafer, and the photoresist remained on the epitaxial wafer is cleaned. The photoetching process is to remove part of the photoresist and expose the optical film; the etching step is to remove the optical film at the photoetching position, so that the metal after the metal deposition step is directly contacted with the Cap layer. However, when the metal deposition step is performed at present, the edge metal deposited on the Cap layer cannot be tightly attached to the optical film, and a certain gap (as shown in the SEM image of fig. 1) may exist, and when the SN830 solution is used to clean the residual photoresist, the SN830 solution is very easy to be dipped into the Cap layer from the gap, so as to dissolve a part of the Cap layer, and cause a certain damage to the Cap layer, which finally affects the optoelectronic characteristics and reliability of the chip.

Therefore, it is necessary to solve the problem that the edge of the optical film and the metal cannot be tightly adhered during metal deposition, and a method for protecting the Cap layer from etching is sought.

Disclosure of Invention

Aiming at the technical problem, the invention provides an etching optimization method of the Cap layer, which can enable the metal of a chip to be perfectly attached to the edge of an optical film during metal deposition, and avoid the etching of the SN830 solution on the Cap layer.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a Cap layer etching optimization method is characterized in that: the method comprises the following steps:

s1, preparing an epitaxial wafer with a full structure;

s2, carrying out warping compensation processing on the N surface of the epitaxial wafer;

s3, depositing an optical film on the Cap layer of the P surface of the epitaxial wafer;

s4, carrying out ohmic contact photoetching on the epitaxial wafer deposited with the optical film to enable the edge of the photoresist to have an inclination angle;

s5, etching the optical film outside the coverage range of the photoresist by using dry etching;

s6, depositing ohmic contact metal, depositing the metal in the etched area, and enabling the deposited metal to be in close contact with the inclination angle of the edge of the photoresist and the Cap layer;

and S7, removing the photoresist by using an SN830 solution.

By adopting the scheme, when the metal is deposited, the metal is slowly changed into a solid from liquid, the edge of the photoresist is inclined to a certain degree, the liquid metal is deposited downwards along the inclined angle, the metal is tightly attached to the photoresist after being solidified, and no gap exists.

Further, in step S4, the method of the ohmic contact lithography for making the photoresist edge have a tilt angle is as follows:

s41, performing a glue coating process on the epitaxial wafer by using a spin coater to ensure that the photoresist is at least 3um thick;

s42, exposing by using an exposure machine, wherein the exposure parameters are exposure dose 2500 and focal length 0;

and S43, developing the exposed epitaxial wafer by using a developing solution.

By adopting the scheme, in order to enable the exposed photoresist to have a certain angle, the gluing process is optimized firstly, the thickness of 3um is ensured, and 3000 angstroms is ensured when dry etching is carried out in the step S5; and then the edge inclination effect of the photoresist is achieved by changing exposure parameters such as exposure dose, focal length and the like.

Further, in step S4, the method of the ohmic contact lithography for making the edge of the photoresist have a tilt angle is as follows:

s411, rapidly and rotationally coating a photoresist on the epitaxial wafer at a high rotating speed by using a spin coater to rapidly spread the photoresist;

s412, standing the epitaxial wafer which is spin-coated with the photoresist for 10S;

and S413, slowly rotating the epitaxial wafer at a low rotating speed by using a spin coater to enable the photoresist on the epitaxial wafer to be uniform.

By adopting the scheme, the photoresist is firstly spread rapidly by rotating at a high speed, the photoresist is still for 10s to ensure the thickness of the photoresist and can not be too thin, and then the photoresist on the whole wafer is uniformly thick by rotating at a low speed.

Furthermore, in step S41, the high rotation speed is 3500-4000 r/S.

Furthermore, in step S43, the low rotation speed is 800 to 1200 r/S.

Furthermore, the inclination angle of the edge of the photoresist is 70-80 degrees.

Furthermore, the warpage compensation mode is to grow a stress film made of SiO₂、SiN_XOr SiO_XN_y。

Furthermore, the material of the optical film is a composition formed by one or more of dielectrics formed by Si, N, O, Al, F and Mg.

Further, the metal material used for metal deposition is one or more of gold, titanium, silver, copper, chromium, manganese and germanium.

Further, the epitaxial wafer with the full structure comprises a Cap layer, a P-DBR layer, an oxide layer, a quantum well layer, an N-DBR layer and a substrate from the P surface to the N surface, wherein the substrate is a GaAs single crystal substrate.

Has the advantages that: according to the invention, through optimizing the steps of the photoetching process method, the photoresist has a certain inclination angle at the exposed edge, the liquid metal is deposited along the inclination angle, so that the deposited metal is tightly attached to the photoresist, the phenomenon that the SN830 solution enters the gap to etch the Cap layer due to the gap is avoided, the selection ratio is increased, the etching angle is conveniently controlled, the yield of the chip is improved, and the performance of the chip is greatly protected.

Drawings

FIG. 1 shows an SEM image of a photoresist with a gap between the photoresist and the metal.

Fig. 2 is a schematic structural diagram of the glued epitaxial wafer.

Fig. 3 is a schematic view of an epitaxial wafer structure after ohmic contact lithography.

Fig. 4 is a schematic structural view of an epitaxial wafer after metal deposition.

Fig. 5 is a schematic view of the structure of the epitaxial wafer after the photoresist is removed.

Fig. 6 is an SEM image of an epitaxial wafer after the method of the present invention was used.

The structure comprises a substrate, a substrate.

Detailed Description

The embodiments of the present invention will be further described with reference to the accompanying drawings.

Example (b): as shown in fig. 2-5, a method for optimizing etching of a Cap layer 3 includes the following steps:

s1, preparing an epitaxial wafer 1 with a full structure; the epitaxial wafer 1 with the full structure comprises a Cap layer 3, a P-DBR layer, an oxide layer, a quantum well layer, an N-DBR layer and a substrate from the P surface to the N surface, wherein the substrate is a GaAs single crystal substrate.

S2, carrying out warping compensation processing on the N surface of the epitaxial wafer 1; the warpage compensation mode is to grow a stress film 2, and the stress film 2 is made of SiO₂、SiN_XOr SiO_XN_y(ii) a The stress film 2 is used for compensating the warping of the epitaxial wafer, so that the epitaxial wafer 1 is flat, and the steps of photoetching, metal deposition and the like are facilitated.

S3, depositing an optical film 4 on the Cap layer 3 on the P surface of the epitaxial wafer 1; the optical film is made of one or a composition of dielectric substances formed by Si, N, O, Al, F and Mg, and the thickness of the optical film 4 is 3000 angstroms.

And S4, carrying out ohmic contact photoetching on the epitaxial wafer 1 deposited with the optical film 4 to enable the edge of the photoresist 5 to have a dip angle of 70-80 degrees.

The method of the ohmic contact lithography for making the edge of the photoresist 5 have a tilt angle is as follows:

s41, performing a glue coating process on the epitaxial wafer 1 by using a spin coater to ensure that the thickness of the photoresist 5 is at least 3 um;

the gluing process comprises the following steps:

s411, rapidly and rotationally coating the photoresist 5 on the epitaxial wafer 1 at a high rotating speed by using a spin coater to rapidly spread the photoresist 5; the high rotating speed is 4000 r/s;

s412, standing the epitaxial wafer 1 which is spin-coated with the photoresist 5 for 10S;

s413, slowly rotating the epitaxial wafer 1 at a low rotating speed by using a spin coater to make the photoresist 5 on the epitaxial wafer 1 uniform; the low rotating speed is 1000 r/s.

And S42, carrying out exposure by using an exposure machine, wherein the exposure parameters are exposure dose 2500 and focal length 0.

S43, developing the exposed epitaxial wafer 1 with a developer.

And S5, etching the optical film 4 outside the coverage of the photoresist 5 by using dry etching.

S6, depositing ohmic contact metal, and depositing metal 6 in the etched area to make the deposited metal closely contact with the inclination angle of the edge of the photoresist 5 and the Cap layer 3; the metal 6 used for metal deposition is made of one or more of gold, titanium, silver, copper, chromium, manganese and germanium.

And S7, removing the photoresist 5 by using an SN830 solution.

In this embodiment, the removal of the photoresist 5 by using the SN830 solution is very desirable.

The dry etching is a technology for etching a film by using plasma, the chemical activity of the gases in the plasma is much stronger than that of the gases in a normal state, and the gases can react with the materials more quickly by selecting proper gases according to different etched materials, so that the aim of etching and removing is fulfilled; the plasma can be guided and accelerated by the electric field to have certain energy, and atoms of the material of the etched object can be knocked out when the plasma bombards the surface of the etched object, so that the aim of etching by utilizing physical energy transfer is fulfilled. Dry etching is a result of a balance of both physical and chemical processes on the wafer surface. In this embodiment, the thickness of the dry etching is 3000 angstroms, and the optical film 4 is just etched away, so as to ensure that the Cap layer is not etched away. The electrode pattern formed by dry etching is annular, and the CD value of the annular electrode is about 3.

When ohmic contact photoetching is carried out, the angle of the photoresist 5 needs to be reduced, the focal length is correspondingly increased,The exposure dose was reduced and the data of the epitaxial wafer 1 generated in adjusting the focus and exposure dose are as follows:

dose of exposure	Focal length	CD	Angle of rotation
				3000	-1	3	90
2800	-0.5	3.1	84
				2500	0	3.15	77

It can be seen that the angle of the epitaxial wafer 1 measured by SEM at an exposure dose of 2500 and a focal length of 0 was 77 degrees, while the CD value of the ring electrode was 3.15 in the normal range, as shown in fig. 6, at which the deposited metal covered the optical film 4 well and the phenomenon of etching the Cap layer 3 with the SN830 solution was not observed from the SEM picture.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims. The techniques, shapes, and configurations not described in detail in the present invention are all known techniques.