CN1152154C - Chemical etching liquid system for preparing gallium antimonide semiconductor device - Google Patents

Abstract

The invention relates to a chemical corrosion solution for preparing gallium antimonide-based semiconductor devices. It includes hydrochloric acid series, hydrofluoric acid series and tartrate series. The hydrochloric acid-based corrosive solution is hydrochloric acid, tartaric acid and hydrogen peroxide; the hydrofluoric acid-based corrosive solution is hydrofluoric acid, tartaric acid and hydrogen peroxide; the tartrate-based corrosive solution is potassium sodium tartrate, hydrochloric acid and hydrogen peroxide. These three etching solutions will not damage the photoresist mask, and can be applied to the mesa etching of binary and quaternary III-V antimony compounds such as GaSb, AlGaAsSb, InGaAsSb, etc. The etching rate is controllable and less than 1 μm/min. Compatible with device process.

Description

Chemical etching solution for preparing gallium antimonide-based semiconductor devices

technical field

The invention relates to a class of chemical etching solution for preparing gallium antimonide (GaSb) based semiconductor devices. It belongs to the field of semiconductor devices.

Background technique

Electronic and optoelectronic devices made of III-V antimonide multilayer heterostructure materials have been developed for many years, and the device performance has been greatly improved. However, because the devices are mostly limited to simple structures, the further improvement of device performance is greatly restricted. One of the main reasons is that the device technology of antimony-containing compound semiconductors is not mature enough. Wet etching is an effective method for preparing various mesa structures in the fabrication process of III-V antimonide devices, and the choice of etching solution in the wet etching process is the key.

The chemical etching of GaSb and related antimony-containing compounds has been studied in the 1980s, but most of them are used to clean the surface of GaSb substrate materials for MOCVD or MBE. Typical etching solutions include Br ₂ +CH ₃ OH, HNO ₃ +HF+H ₂ O, Br ₂ +HCI+HNO ₃ +CH ₃ COOH, etc. Among these etching solutions, Br ₂ +CH ₃ OH etchant has better performance, and the surface of the etched material is smooth and bright. And the corrosion of GaSb material is isotropic. Its reaction mechanism is as follows:

GaBr ₃ soluble in CH ₃ OH and decomposable SbBr ₃ are generated. However, since the methanol in the etching solution is an organic solvent, it can dissolve most of the photoresist, and the etching rate of these etching solutions is too high, reaching several to tens of microns per minute, which is difficult to control in the device process. There are many limitations in the process. For other oxidative corrosion solutions, when they react with GaSb, Sb ₂ O ₃ , which is neither soluble in water nor in acidic or alkaline solutions, will be formed. This oxide film prevents the further occurrence of corrosion reaction. Obviously, these corrosive solutions cannot be used in the preparation of devices. The corrosion solution and corrosion characteristics suitable for quaternary alloy semiconductors AlGaAsSb and InGaAsSb have not been reported in the literature.

So far, the chemical etching solution for preparing gallium antimonide-based semiconductor devices is unsatisfactory in use. There are mainly three problems: (1) the corrosion rate is too high, (2) the process control is difficult, (3) the formation of insoluble water oxides. Therefore, the development of new chemical etching solutions for the preparation of GaSb-based devices has become an urgent need.

Contents of the invention

The object of the present invention is to provide a new chemical etching solution for preparing GaSb-based semiconductor devices. That is to say, the present invention is mainly aimed at III-V group antimonide epitaxial single crystal materials used in optoelectronic devices and high-frequency microwave devices, and provides a new type of corrosion solution with excellent performance. This corrosion solution has the characteristics of slow corrosion rate and easy process control, and It does not contain components that will damage the photoresist, is compatible with the device process, and is not easy to form oxides that are insoluble in water. Since the current III-V antimonide devices are mainly composed of quaternary AlGaAsSb, InGaAsSb and GaSb materials, the etching solution must have good corrosion characteristics for these materials and can be used in the preparation process of optoelectronic devices.

The chemical corrosion solution provided by the present invention mainly includes hydrochloric acid series, hydrofluoric acid series and tartrate series.

1. Hydrochloric acid corrosive solution

The composition of the hydrochloric acid-based corrosive solution includes hydrochloric acid, tartaric acid and hydrogen peroxide. The molar concentration of the components is expressed by mixing 2.5M hydrochloric acid solution, 0.25M tartaric acid solution and 0.6M hydrogen peroxide solution in a volume ratio of 1-4:1:1, and ultrasonically stirring and mixing uniformly. Clean the sample with isopropanol, acetone, alcohol, and deionized water before corrosion, then put it into the corrosion solution, stir it manually for 10 seconds every 20-30 seconds, and clean it with deionized water after the corrosion is over.

The etchant has good corrosion characteristics for GaSb, and as shown in Fig. 1, the corrosion depth has a linear relationship with the corrosion time, and the corresponding corrosion rate is about 0.18 μm/min. This etching solution is suitable for the preparation of devices using a single GaSb material and narrow line width and the surface treatment of GaSb (see Example 1 for details).

Under the same conditions, AlGaAsSb was corroded with hydrochloric acid corrosion solution. The results show that for AlGaAsSb materials with the same composition, the corrosion depth also exhibits a linear relationship with time. The etch rate is close to that of GaSb material (see Example 2 for details).

2. Hydrofluoric acid corrosion solution

The hydrofluoric acid-based corrosion solution is prepared by mixing 5M hydrofluoric acid solution, 0.25M tartaric acid solution and 0.6M hydrogen peroxide solution, and is stirred evenly by ultrasonic stirring. With different mixing ratios, different reaction rates can be obtained. Similar to the hydrochloric acid corrosion solution, the sample was cleaned with isopropanol, acetone, alcohol, and deionized water before the reaction, and manually stirred for 10 seconds every 20-30 seconds during the reaction, and cleaned with deionized water after the reaction.

The specific components of the hydrofluoric acid-based etching solution are hydrofluoric acid: tartaric acid: hydrogen peroxide = 1-4:1:1 (volume ratio), as shown in Figure 2, when the ratio of the three is 1:1:1, the etching solution The etching rate of GaSb reaches 2.5 μm/min (see Example 3 for details). When the ratio of the three is 4:1:1, the etching rate of GaSb is about 1.0 μm/min. Figure 3 shows the relationship between the corrosion rate of hydrofluoric acid-based etching solution and GaSb under different dilution ratios. As can be seen from the figure, the hydrofluoric acid concentration in the hydrofluoric acid-based etching solution has a very obvious influence on the corrosion rate (see Example 4 for details).

The corrosion rate of quaternary alloy semiconductor AlGaAsSb by hydrofluoric acid etching solution depends not only on the composition and concentration of the etching solution, but also on the Al composition of the material. The results are shown in Figure 4. Therefore, the change trend of the corrosion rate appears to be more complicated (see Example 5 for details).

Corrosion of GaSb and AlGaAsSb with hydrofluoric acid-based etching solution can obtain steep corrosion steps, and the curve of the corrosion area is smooth. The pH value of the hydrofluoric acid solution is in the range of about 3 to 5, which is suitable for using conventional photoresist as a resist

Changing the temperature can also adjust the corrosion rate. Figure 5 shows the variable temperature corrosion of AlGaAsSb with an Al composition of 0.866, the temperature ranges from room temperature 300K to 360K, and the corrosion rate can be adjusted between 0.4-1.6 μm/min (see Example 6 for details).

3. Tartrate corrosion solution

The components of the tartrate-based corrosive solution include potassium sodium tartrate, tartaric acid and hydrogen peroxide. Prepare potassium sodium tartrate/hydrochloric acid solution first: HCl: H ₂ O: potassium sodium tartrate = 66ml: 440ml: 24g, prepare dilute hydrogen peroxide solution before corrosion: H ₂ O ₂ : H ₂ O = 20ml: 480ml, and then press 0.5- Mix the two solutions at a volume ratio of 2:1, and mix them evenly with ultrasonic stirring. Wash the sample with isopropanol, acetone, alcohol, and deionized water before the reaction, manually stir for 10 seconds every 20-30 seconds during the reaction, and wash with deionized water after the reaction.

The etching solution is suitable for GaSb, AlGaAsSb (Al composition is 0-0.5) and InGaAsSb. Since the etchant is weakly acidic, it has no obvious effect on the photoresist. The corroded surface of the sample and the mesa corroded by the cleavage plane are clear (see Example 7 for details). The etching rate of the etching solution for AlGaAsSb and InGaAsSb is relatively stable, and the etching depth increases linearly with the etching time, and there is no obvious anisotropy for quaternary materials, that is, the etching rate for each crystal plane is basically the same. Figure 6 shows the etching rate of the etching solution for AlGaAsSb (X _Al =0-0.5) and InGaAsSb. For In _0.187 Ga _0.813 As _0.02 Sb _0.98 , the corrosion rate is 0.21μm/min; for Al _0.206 Ga _0.794 As _0.02 Sb _0.98 , the corrosion rate is 0.29μm/min; for Al _0.492 Ga _0.508 As _0.02 Sb _0.98 and In other words, the corrosion rate is 0.26 μm/min. The lateral corrosion effect of this solution is relatively obvious. When the corrosion depth reaches 1.6-1.8 μm, the lateral corrosion causes the step interface to shrink inward by about 0.5 μm.

Compared with the prior art, the three chemical etching solutions provided by the present invention have three advantages. First, it has wide applicability and can be applied to GaSb, AlGaAsSb and InGaAsSb semiconductor materials. However, the conventional etchant can only corrode GaSb materials. Second, the corrosion rate is slow and easy to control. The corrosion rate of all corrosive solutions in the present invention can be controlled within 1 μm/min, and the corrosion rate can be controlled by dilution or temperature change. The corrosion rate of the corrosive solution reported in the literature is generally above 1 μm. Third, it is compatible with the device process. None of the above etching solutions contain components that damage the photoresist. Therefore, the three etching solutions described in the present invention can be applied to the preparation of GaSb-based semiconductor devices.

Description of drawings

The substantive features and remarkable progress of the present invention are further described below through the accompanying drawings and examples, but the present invention is by no means limited, that is, the present invention is by no means limited to the examples.

Figure 1(a) The relationship between the corrosion depth and time of GaSb by hydrochloric acid etching solution. The abscissa in the figure is the corrosion time (second), and the ordinate is the corrosion depth (μm).

(b) The corresponding step curve.

Figure 2 The relationship between the corrosion depth and time of the hydrofluoric acid-based corrosive solution.

Fig. 3 Corrosion rate of GaSb by hydrofluoric acid-based etching solution at different dilution ratios. The abscissa in the figure is the ratio of water: hydrofluoric acid etching solution, and the ordinate is the corrosion rate (μm/min).

Fig. 4 Corrosion rate of AlGaAsSb quaternary alloy semiconductor by hydrofluoric acid-based etchant under different Al compositions. The abscissa is the Al composition, and the ordinate is the corrosion rate (μm/min).

Fig. 5 Corrosion rate of AlGaAsSb by hydrofluoric acid-based etching solution at different temperatures. The abscissa is the temperature 1000/T (1/K), and the ordinate is the corrosion rate (μm/min).

Fig. 6 Corrosion depth and time of AlGaAsSb and InGaAsSb by tartaric acid-based etchant. The abscissa is time (second), and the ordinate is corrosion depth (μm).

(a) Al _0.206 Ga _0.794 As _0.02 Sb _0.98

(b) Al _0.492 Ga _0.508 As _0.02 Sb _0.98

(c) In _0.187 Ga _0.813 As _0.02 Sb _0.98

Figure 7(a)-(c) are the corrosion morphology of the surface and cleavage plane of Al _0.206 Ga _0.794 As _0.02 Sb _0.98 , Al _0.492 Ga _0.508 As _0.02 Sb _0.98 , In _0.187 Ga _0.813 As _0.02 Sb _0.98 , respectively .

Detailed ways

Embodiment 1 Corrosion of GaSb material by hydrochloric acid-based etchant

Take hydrochloric acid with a molar concentration of 2.5M, 0.25M tartaric acid solution and 0.6M hydrogen peroxide solution, and mix them in a volume ratio of 1:1:1 to form a hydrochloric acid-based corrosion solution. Clean the GaSb material with isopropanol, acetone, alcohol and deionized water first, then put it into a hydrochloric acid corrosion solution for corrosion, stir manually for 10 seconds every 30 seconds during the reaction, and wash it with deionized water after the reaction. The result is as follows As shown in Figure 1(a), it shows that GaSb is etched with this etching solution, the etching depth has a linear relationship with time, the reaction is stable, and it has good repeatability. From the step diagram in Figure 1(b), it can be seen that the boundary steps between the corrosion zone and the non-corrosion zone are steep, indicating that the lateral corrosion effect of the corrosive solution is not obvious, and the reaction rate is only 0.18 μm/min at the ratio concentration, which can be well Control the depth of corrosion.

Example 2 Corrosion of AlGaAsSb Quaternary Alloy Semiconductor Materials by Hydrochloric Acid Corrosion Solution

The Al _0.206 Ga _0.794 As _0.02 Sb _0.98 quaternary alloy semiconductor material was etched with the same concentration and proportion of the etchant as in Example 1. Corrosion depth also exhibits a linear relationship with time. The etch rate is similar to that of GaSb material. Others are the same as embodiment 1.

Embodiment 3 Corrosion of GaSb by hydrofluoric acid etching solution

Hydrofluoric acid: tartaric acid: hydrogen peroxide with a volume ratio of 1:1:1 corrodes the GaSb material, and the relationship between the corrosion depth and time is shown in Figure 2, which is a linear relationship. When reducing the concentration of hydrofluoric acid in the solution while keeping the concentration of other components constant, the corrosion rate has little change, but when the concentration of hydrofluoric acid in the solution is reduced to below 0.5M, the corrosion rate shows a sharp downward trend . All the other are with embodiment 1.

Example 4 The effect of different dilution ratios of hydrofluoric acid solutions on the corrosion rate of GaSb

The hydrofluoric acid solution is: hydrofluoric acid: tartaric acid: hydrogen peroxide = 4:1:1 (volume ratio), and its corrosion rate for GaSb is about 1.0 μm/min. With the increase of the dilution ratio of corrosive solution, the corrosion rate basically decreased linearly. When the solution dilution ratio reaches more than 2, the corrosion rate tends to be constant. When the dilution ratio is 3.4, the corrosion rate drops to 0.3μm/min. See Figure 3 for details.

Example 5 Corrosion rate of AlGaAsSb quaternary alloy semiconductor materials with different Al components by hydrofluoric acid-based etchant.

When hydrofluoric acid: tartaric acid: hydrogen peroxide: water is mixed at a volume ratio of 4:1:1:8, it has good corrosion characteristics for AlGaAsSb with all Al components. Using this solution to corrode AlGaAsSb materials with different Al components shows that (as shown in Figure 4), the corrosion rate of AlGaAsSb materials with different Al components is parabolic, and the corrosion rate of the corrosion solution presents when the Al component is about 0.5. The minimum value, when the Al composition is about 0.1, that is, when the AlGaAsSb composition is close to GaSb, the corrosion rate is about 0.7μm/min. When the Al composition changes within the range of 0.1 to 0.9, the corrosion rate is mostly below 0.8 μm/min, which is suitable for device fabrication.

Example 6 Control the corrosion rate of AlGaAsSb material by hydrofluoric acid-based etching solution by adjusting the temperature.

Hydrofluoric acid: tartaric acid: hydrogen peroxide: water is mixed in a volume ratio of 4:1:1:8 to etch AlGaAsSb with an Al composition of 0.866. During the corrosion, the temperature of the corrosion solution is controlled by a water bath from 300K to 360K, and the relationship between the corrosion rate and the temperature is obtained as shown in Figure 5. It can be seen from the figure that when the temperature changes from 300K to 360K, the corrosion rate changes from 0.4 μm/min to 1.6 μm/min, and the curve in the figure shows a good linear relationship, which satisfies the Arrhenius relationship.

Example 7 A tartrate-based etchant was used to etch a 100 μm-wide mesa on molecular beam epitaxy AlGaAsSb and InGaAsSb single crystal materials.

The samples used for etching are AlGaAsSb and InGaAsSb grown by solid-state source molecular beam epitaxy. The substrate is n-type Te-doped (100) GaSb, and its electron concentration is about 1×10 ¹⁸ cm ^-3 . The Al components in AlGaAsSb are 0.2 and 0.5, and the As components are 0.02. The In composition in InGaAsSb is 0.18, and the As composition is 0.02. Prepare potassium sodium tartrate/hydrochloric acid solution: HCl: H ₂ O: potassium sodium tartrate = 66ml: 440ml: 24g. The epitaxial material was first cleaned with isopropanol, acetone, absolute ethanol, and deionized water, and dried with nitrogen. Then remove water vapor on a hot plate at 120°C, and apply photoresist AZ6809. After conventional photolithography and development processes, the etching and photoresist protection areas are determined, that is, strip-shaped areas with a width of 100 μm. Incubate in an oven at 80°C for 15 minutes. Prepare dilute hydrogen peroxide solution: H ₂ O ₂ :H ₂ O=20ml:480ml, then mix the dilute hydrogen peroxide solution and potassium sodium tartrate/hydrochloric acid solution at a volume ratio of 1:1, and mix well by ultrasonic stirring. After drying the photoresist, react at room temperature with an etchant. The reaction was manually stirred for 10 seconds every 30 seconds. After the reaction, rinse the photoresist repeatedly with deionized water, then wash the photoresist with acetone, and finally dry it with nitrogen gas. Measure the steps at the boundary of the corrosion area on a step meter to obtain the corrosion depth, and observe the corrosion morphology under a microscope. Figure 6(a)-(c) shows the relationship between corrosion depth and time of Al _0.206 Ga _0.794 Sb _0.98 , Al _0.492 Ga _0.508 As _0.02 Sb _0.98 and In _0.187 Ga _0.813 As _0.02 Sb _0.98 . Figure 7(a)-(c) respectively shows the surfaces and cleavage planes of Al _0.206 Ga _0.794 As _0.02 Sb _0.98 , Al _0.492 Ga _0.508 As _0.02 Sb _0.98 , In _0.187 Ga _0.813 As _0.02 Sb _0.98 after 2 minutes corrosion corrosion morphology.

Claims (2)

1. prepare a kind of chemical corrosion solution that gallium antimonide base semiconductor device is used, it is characterized in that the composition of described chemical corrosion solution comprises potassium sodium tartrate, tartaric acid and hydrogen peroxide; Prepare potassium sodium tartrate/hydrochloric acid solution earlier: HCl: _H O: potassium sodium tartrate = 66ml: 440ml: 24g, dilute hydrogen peroxide solution before corrosion: H ₂ O ₂ : H ₂ O = 20ml: 480ml, and then mix the two solutions at a volume ratio of 0.5-2:1. 2. The chemical etching solution for preparing gallium antimonide-based semiconductor devices according to claim 1, characterized in that the etching depth of the chemical etching solution to AlGaAsSb and InGaAsSb increases linearly with etching time.

Images