CN106486355A - A kind of wet etching method of InGaP - Google Patents

Abstract

The present invention relates to the technical field of semiconductor manufacturing industry, in particular to an InGaP wet etching method, comprising the following steps: growing an InGaP layer on a substrate or an epitaxial layer; using a wet etching method to etch the substrate or the epitaxial layer etch, and grow the SiN layer on the InGaP layer; use reactive ion beam etching to etch the SiN layer; use dilute hydrochloric acid to clean the surface of the wafer to remove the thin layer of surface oxide; use weak ammonia to clean the surface of the wafer to remove dilute hydrochloric acid treatment H ⁺ ions remaining on the wafer surface, and hang OH-on the dangling bonds; use a mixed acid solution of concentrated hydrochloric acid and phosphoric acid to etch the InGaP layer; use weak ammonia water to clean the wafer surface to remove InGaP remaining H ⁺ ions, and hang OH-on the dangling bond, so as to effectively remove the influence of the previous process on the surface of the InGaP layer, and ensure the smooth progress of the HBT process.

Description

A kind of wet etching method of InGaP

technical field

The invention relates to the technical field of semiconductor manufacturing, in particular to an InGaP wet etching method.

Background technique

GaAs is the most important and widely used semiconductor material among III-V compound semiconductors. The electron mobility in GaAs is 6 times that of silicon (Si), and its electron peak drift velocity is 2 times that of Si. Therefore, GaAs devices have the characteristics of high frequency, high speed, low power consumption, low noise, and monolithic integration.

GaAs HBT devices are widely used in smartphones and base stations, which have the following advantages (source doctoral thesis: Research on InGaP/GaAs microwave HBT devices and VCO circuits):

1. Single positive power supply operation. Unlike depletion-type FET and HEMT devices, a negative voltage must be applied to pinch off the channel. The turn-on voltages of HBT are all positive, and only one positive power supply is needed to work, which can simplify the circuit design.

2. High power density. When the frequency is not too high, the power added efficiency (PAE) is also larger.

3. High breakdown voltage. The bandgap width of the HBT collector material is large, and a high breakdown voltage can be obtained by designing the thickness and doping concentration of the collector region, thereby increasing the output power. Moreover, the reverse breakdown voltage of the collector junction (BC junction) that determines the breakdown voltage of the HBT is mainly determined by the parameters of the epitaxial material, and is not easily affected by the process.

4. Early effect (base area widening effect) and Kirk effect (effective base area expansion effect) are small, so it has better linearity.

5. The requirements for photolithography are relatively low in the manufacture of HBT devices, and the general feature size is 1 μm to 2 μm. Since the thickness of the critical dimension of the base region of the HBT is determined by the thickness of the epitaxial layer, the difficulty of submicron lithography in FET and HEMT is avoided, thereby improving the uniformity and yield of the device.

Currently, InGaP/GaAs has become the mainstream of GaAs-based HBTs. Compared with traditional AIGaAs/GaAs HBT, InGaP/GaAs HBT mainly has the following advantages:

1. In _0.49 Ga _0.51 P is lattice-matched with GaAS, the bandgap width reaches 1.91eV at room temperature, and the breakdown voltage is large, which is beneficial to microwave power applications.

2. InGaP does not contain Al and related defects, has a lower surface recombination rate and fewer deep-level recombination centers, which makes the device more stable and reliable.

3. It is easier to achieve selective etching between InGaP and GaAs, and the device manufacturing process is more stable and easy to control.

Since GaAs HBT is a vertical structure device, the wet etching process is the key process of the whole device. In fact, InGaP is chemically stable. Among common acids and bases in the integrated circuit industry, concentrated hydrochloric acid + phosphoric acid is generally used to etch InGaP. The ratio of concentrated hydrochloric acid: phosphoric acid is 3:2~10:1. Fast, generally above 100 Å/s. Generally, in HBT devices, the thickness of InGaP is 50 Å~5000 Å.

For the HBT process, the etching of InGaP is generally after the front process such as GaAs etching and SiN protective layer etching, because GaAs generally uses wet etching, and SiN generally uses reactive ion beam etching (RIE) Other dry etching methods, plus the fact that As/Ga oxides are easily formed on the surface of GaAs, affect the etching rate of InGaP, and in severe cases, the etching rate is reduced to below 10 Å/s.

Contents of the invention

The embodiment of the present invention provides an InGaP wet etching method, which solves the problem that in the prior art, when etching the InGaP layer, the smooth progress of the HBT process cannot be guaranteed due to the influence of the previous process on the surface of the InGaP layer.

In order to solve the above-mentioned technical problems, a kind of wet etching method of InGaP provided by the present invention comprises the following steps:

growing an InGaP layer on a substrate or an epitaxial layer;

Etching the substrate or epitaxial layer by wet etching, and growing a SiN layer on the InGaP layer;

Etching the SiN layer by reactive ion beam etching;

Wash the wafer surface with dilute hydrochloric acid to remove the thin oxide layer on the surface;

Wash the wafer surface with weak ammonia water to remove the residual H ⁺ ions after the dilute hydrochloric acid treatment of the wafer surface, so that the dangling bonds can hang OH-;

Using a mixed acid solution of concentrated hydrochloric acid and phosphoric acid to etch the InGaP layer;

Clean the wafer surface with weak ammonia water to remove the residual H ⁺ ions after InGaP treatment on the wafer surface, so that the dangling bonds can hang OH-.

Adopting one or more technical solutions in the present invention has the following beneficial effects:

The wet etching method of InGaP that the present invention adopts firstly grows an InGaP layer on the substrate or the epitaxial layer, then, adopts the wet etching method to etch the substrate or the epitaxial layer, and grows SiN on the InGaP layer layer, then, the reactive ion beam etching method can be used as the SiN layer, and then, the surface of the wafer is cleaned with dilute hydrochloric acid to remove the surface oxide film, and the surface of the wafer is cleaned with ammonia water to remove the residual H after the surface of the wafer is treated with dilute hydrochloric acid. ⁺ ions, so that the dangling bonds are hung with OH- to protect the surface of the device. Then, use a mixed acid solution of concentrated hydrochloric acid and phosphoric acid to etch the InGaP layer. Finally, use weak ammonia to clean the wafer surface to remove the InGaP layer. The H ⁺ ions make the dangling bonds hang OH-, protect the surface of the device, thereby effectively removing the influence of the previous process on the surface of the InGaP layer, and ensuring the smooth progress of the HBT process.

Description of drawings

FIG. 1 is a schematic flowchart of steps of an InGaP wet etching method in an embodiment of the present invention.

detailed description

The embodiment of the present invention provides an InGaP wet etching method, which solves the problem that in the prior art, when etching the InGaP layer, the smooth progress of the HBT process cannot be guaranteed due to the influence of the previous process on the surface of the InGaP layer.

In order to solve the above-mentioned technical problems, the technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

The present invention provides a wet etching method for InGaP, as shown in Figure 1, comprising: S101, growing an InGaP layer on a substrate or an epitaxial layer, and the material of the substrate is GaAs, InP, Si, SiC Either one, the epitaxial layer is specifically any one of a GaAs epitaxial layer and an InP epitaxial layer, and the thickness of the InGaP layer is 100 Ř1 μm.

Next, in S102, the substrate or the epitaxial layer is etched by wet etching, and a SiN layer is grown on the InGaP layer. Specifically, the SiN layer is grown by chemical vapor deposition and reactive sputtering, and the temperature is controlled at 200 ℃~600℃, the thickness of the formed SiN layer is 200 Å~1μm.

Then, S103 , etching the SiN layer by using a reactive ion beam method (RIE).

The foregoing is the front-end process before etching the InGaP layer. Since the front-end process has an impact on the efficiency of etching the InGaP layer, the subsequent processing steps are continued.

S104, cleaning the surface of the wafer with dilute hydrochloric acid to remove the thin oxide layer on the surface. Wherein, the mass concentration ratio of hydrochloric acid to water in the dilute hydrochloric acid ranges from 1:500 to 1:10.

Next, perform S105, wash the wafer surface with weak ammonia water, remove the residual H ⁺ ions after the dilute hydrochloric acid treatment of the wafer surface, make the dangling bonds hang OH-, thereby protecting the device surface. The mass concentration ratio of ammonia water to water in the weak ammonia water ranges from 1:500 to 1:10.

Then, perform S106, using a mixed acid solution of concentrated hydrochloric acid and phosphoric acid to etch the InGaP layer. The mass concentration ratio of concentrated hydrochloric acid and phosphoric acid in the mixed acid solution of concentrated hydrochloric acid and phosphoric acid ranges from 3:2 to 10:1.

Finally, S107 is performed to clean the surface of the wafer with weak ammonia water to remove the residual H ⁺ ions after the InGaP treatment on the surface of the wafer, so that the dangling bonds are linked to OH-, thereby protecting the surface of the device.

Through the above scheme, the use of weak ammonia water and dilute hydrochloric acid can effectively clean the surface of the wafer and ensure the normal etching of InGaP. In this way, the influence of the previous process on the surface of the InGaP layer is avoided, and the smooth progress of the HBT process is ensured.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (8)

1. a kind of wet etching method of InGaP, it is characterised in that comprise the steps：

InGaP layer is grown on substrate or epitaxial layer；

Substrate or epitaxial layer are performed etching using wet etching method, and SiN layer is grown on InGaP layer；

SiN layer is etched using reactive ion beam etching (RIBE) method；

Using watery hydrochloric acid cleaning wafer surface, oxide on surface thin layer is removed；

Using weak ammonia liquor cleaning wafer surface, the H remained after watery hydrochloric acid processes crystal column surface is removed⁺Ion so that dangling bonds hang up OH-；

Using concentrated hydrochloric acid and the mix acid liquor of phosphoric acid, InGaP layer is etched；

Using weak ammonia liquor cleaning wafer surface, the H remained after InGaP processes crystal column surface is removed⁺Ion so that dangling bonds hang up OH-.

2. the wet etching method of InGaP according to claim 1, it is characterised in that the material of the substrate is GaAs, Any one in InP, Si, SiC.

3. the wet etching method of InGaP according to claim 1, it is characterised in that the epitaxial layer is specially GaAs Any one in epitaxial layer, InP epitaxial layer.

4. the wet etching method of InGaP according to claim 1, it is characterised in that the thickness of the InGaP layer is 100 Å~1μm.

5. the wet etching method of InGaP according to claim 1, it is characterised in that described grow on InGaP layer SiN layer, using chemical vapor deposition, reactive sputtering method growth SiN layer specially on InGaP layer, control temperature is at 200 DEG C ~ 600 DEG C, the SiN layer thickness of generation is 200 ~ 1 μm.

6. the wet etching method of InGaP according to claim 1, it is characterised in that hydrochloric acid and water in the watery hydrochloric acid Mass concentration ratio scope be 1:500~1:10.

7. the wet etching method of InGaP according to claim 1, it is characterised in that ammoniacal liquor and water in the weak ammonia liquor Mass concentration ratio scope be 1:500~1:10.

8. the wet etching method of InGaP according to claim 1, it is characterised in that the concentrated hydrochloric acid is mixed with phosphoric acid Close in acid solution, concentrated hydrochloric acid is 3 with the mass concentration ratio scope of phosphoric acid：2~10:1.