JPH073826B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and in particular, aluminum gallium arsenide (AlGaAs) -gallium arsenide (GaA).
s) In heterojunction semiconductor materials, A
The present invention relates to a method for selectively etching lGaAs.

(2) Conventional technology and problems In conventional AlGaAs-GaAs heterojunction semiconductor materials, Ga
As a method of selectively etching AlGaAs with respect to As, a wet chemical etching method using phosphoric acid or hydrofluoric acid is used.

However, in recent years, in semiconductor devices that require fine processing, it is difficult to miniaturize the pattern of the semiconductor device due to problems such as uniformity and controllability of wet chemical etching and side etching. Further, in the gas phase etching method and the like, since the gas phase reaction uses a gas flow, the etching in the wafer surface varies depending on the flow direction of the reaction gas, and even if the gas supply is stopped, Etching progresses due to the etchant remaining on the surface. As a result, reproducibility, controllability, etc. are significantly deteriorated, and it is practically impossible to etch the semiconductor operating layer or the like, which requires precise control of the film thickness.

On the other hand, there is a reactive ion etching method using a plasma chemical reaction as a manufacturing method of a semiconductor device which is an alternative to these, which is characterized in that a vertical etching profile is easily obtained, and uniformity and controllability are excellent. As I have it, my expectations are high.

(3) Object of the Invention An object of the present invention is to provide a method for selectively etching AlGaAs with respect to GaAs in an AlGaAs-GaAs heterojunction semiconductor material, in particular, to significantly improve processing accuracy and etching of a thin film. It is intended to provide an etching treatment method capable of controlling extremely well.

(4) Structure of the Invention The present invention is directed to AlGaAs-Ga in which AlGaAs is exposed at least partially.
The As heterojunction semiconductor substrate is maintained at a predetermined temperature, and the AlGaAs layer is selectively etched by reactive ion etching using a gas containing at least one of chlorine and bromine as an etching gas.

In the present invention, a gas containing chlorine (Cl) or bromine (Br) is used as an etching gas, and the difference in vaporization temperature of the reaction product of Cl or Br in plasma between AlGaAs and GaAs is measured. Utilizing this, selective etching of AlGaAs with respect to GaAs is performed. That is, by appropriately controlling the temperature of the substrate to be etched, it is possible to control the evaporation rate of Cl or Br products, thereby providing etching selectivity, which is not possible with conventional wet chemistry and vapor phase etching. The etching is controlled by parameters.

Here, as the gas containing Cl, for example, Cl ₂ , HCl, CCl ₄ , COC
There are _{l 2, C 2 Cl 4,} CHCl 3, CBr 2 Cl 2, BCl 3 , etc., and as the gas containing _{Br, BBr 3, CHBr 3,} CBr 2 Cl 2 and the like. When plasma is formed using these gases, Cl ions,
The following chemical reaction product is formed by Cl radical, Br ion, and Br radical.

Chemical reaction product Boiling point (° C) AlCl ₃ 182.7 (Sublimation temperature 177.8 ° C) GaCl ₃ 201.3 AsCl ₃ 130.2 Chemical reaction product Boiling point (° C) AlBr ₃ 263.3 GaBr ₃ 278.8 AsBr ₃ 221.0 AlxGa ₁ -XAs compared to GaAs And low evaporation temperature AlCl ₃
Or, it contains a large amount of AlBr ₃ component. Therefore, when selectively etching AlGaAs with respect to GaAs, for example, Cl
In the case of the system, by setting the temperature of the substrate to be processed to an appropriate temperature between the boiling points of both AlCl ₃ and GaCl ₃ , selective etching with a large difference in etching grade becomes possible.
Further, by raising the temperature of the substrate to be processed above the boiling point, etching with a high etching rate of AlGaAs can be realized, while by lowering the temperature, etching with a low etching rate of AlGaAs can be realized.

The Br-based etching gas is characterized in that it has a higher boiling point by about 50 to 100 [° C.] and a smaller etching rate than when a Cl-based etching gas is used. That is, it is suitable for etching the minute thickness of AlGaAs, and the controllability with respect to the etching time becomes good.

Here, a gas containing fluorine (F) such as CCl ₂ F ₂ is conceivable as the gas containing Cl or Br, but since the non-volatile product AlF ₃ is formed by the reaction between Al and F, On the contrary, the selectivity of AlGaAs to GaAs is remarkably lost, and a gas containing F cannot be used.

When the gas containing Cl or Br is used, the selectivity to silicon dioxide (SiO ₂ ) or photoresist is good, and these silicon dioxide and photoresist can be used as a mask material.

Further, since the present invention performs etching using the reactive ion etching method, there is no side etching as in the case of using the wet chemical etching method, and the uniformity and controllability for etching of fine areas are improved. Needless to say.

(5) Embodiment of the Invention One embodiment of the present invention will be described in detail. FIG. 1 is a cross section of an AlGaAs-GaAs heterojunction semiconductor substrate.

In FIG. 1, 1 is a semi-insulating GaAs substrate, 2 is a thickness of 10
00 [Å] non-doped GaAs layer, 3 has a thickness of 500 [Å],
AlxGa ₁ -xAs layer (x = 0.3) with an impurity concentration of 10 ¹⁸ cm ^-3 , 4
Indicates a GaAs layer having a thickness of 500 [Å] and an impurity concentration of 10 ¹⁸ cm ⁻³ , and the GaAs layer 4 is provided with a patterned opening (FIG. 4A).

Next, the reactive ion etching apparatus used in this example will be briefly described.

FIG. 2 is a schematic sectional view of the reactive ion etching apparatus. In the figure, 5 is a vacuum chamber, 6 is an electrode corresponding to an anode, 7 is an electrode corresponding to a cathode, and 8 is an electrode shown in FIG. 1 (a).
The semiconductor substrate to be processed shown in, 9 is a resistance heater,
Reference numeral 10 is a Cl ₂ gas introduction source, and 11 is a vacuum pump.

The target semiconductor substrate 8 is placed on the anode electrode 6, and the target semiconductor substrate 8 is maintained at a predetermined temperature by the resistance heater 9. Further, the vacuum chamber 5 is previously filled with helium (He) gas, and Cl ₂ gas is introduced into the vacuum chamber 5 from the Cl ₂ gas introduction source 10. By applying a high frequency voltage between the electrodes 6 and 7, a plasma discharge is generated between the cathode electrode facing the semiconductor substrate 8 to be processed and the vacuum chamber 5
Reactive ions generated therein are bombarded on the semiconductor substrate 8 to be processed, and the semiconductor substrate 8 to be processed is etched by the physical sputtering effect and the chemical reaction effect.

FIG. 3 shows the gas pressure ratio Cl ₂ / H ₂ = 0.1 to 10,
AlxGa ₁ -xAs (x = 0. 0 when the substrate temperature was changed under the conditions of total gas pressure of 1 to 10 [Pa] and electric power of 20 to 200 [W].
3 is a graph showing the measured etching rates of GaAs and 3). In the figure, the curve a is AlxGa ₁ -xAS (x = 0.
The etching rate of 3) and curve b show the etching rate of GaAs.

As is clear from FIG. 3, when the substrate temperature is kept at around 200 ° C., the etching selectivity of AlxGa ₁ -xAs (x = 0.3) with respect to GaAs becomes good.

A semiconductor substrate to be processed having the structure shown in FIG.
The AlxGa ₁ -xAs layer 3 is etched with the GaAs layer 4 as a mask under the above conditions using the above apparatus while keeping the temperature at 0 ° C.

As a result, the AlxGa ₁ -xAs layer 3 of the semiconductor substrate 8 is reduced to 150
When [Å] was etched, the GaAs layer 4 was only etched by about 50 [Å] (FIG. 1 (b)).

According to this embodiment, the selectivity of AlGaAs with respect to GaAs is improved as compared with the conventional etching performed at room temperature (R, T), and the etching process can be performed in a short time.

In this embodiment, the temperature of the semiconductor substrate to be processed is 200 [° C]
However, by maintaining the temperature of the substrate to be processed at an appropriate temperature, it is possible to obtain the desired selectivity and etching rate of AlGaAs with respect to GaAs.

(6) Effects of the Invention According to the present invention, in the AlGaAs-GaAs heterojunction type semiconductor material, while improving the selectivity and processing of AlGaAs with respect to GaAs, the thin film can be formed by changing the temperature of the semiconductor substrate to be processed. Can be well controlled.

[Brief description of drawings]

Figure 1 is a cross section of an AlGaAs-GaAs heterojunction semiconductor substrate,
FIG. 2 is a cross section of the ion etching apparatus in this embodiment, and FIG. 3 is AlxGa ₁ -xAs when the substrate temperature is changed.
It is a graph which measured each (x = 0.3) and the etching rate of GaAs. 2,4 ... GaAs layer, 3 ... AlxGa ₁ -xAs layer, 6, 7 ... Electrode, 8
...... Processed semiconductor substrate, 9 ... Resistance heater, 10 ...
… Cl ₂ introduction part, 11 …… vacuum pump

Claims (2)

[Claims] 1. An aluminum / gallium / arsenic / gallium / arsenic / heterojunction semiconductor substrate having an aluminum / gallium / arsenic layer exposed on at least a part thereof is subjected to reactive ion etching using a gas containing chlorine as an etching gas. -Has a step of selectively etching the gallium-arsenic layer, and the temperature at the time of the etching is between the boiling point of the compound of aluminum and chlorine and the boiling point of the compound of gallium and chlorine generated during the etching. A method for manufacturing a semiconductor device, comprising: 2. An aluminum / gallium / arsenic / gallium / arsenic / heterojunction type semiconductor substrate having an aluminum / gallium / arsenic layer exposed at least at a part thereof is subjected to reactive ion etching using a gas containing bromine as an etching gas.・ Has a step of selectively etching the gallium / arsenic layer, and the temperature at the time of the etching is between the boiling point of the compound of aluminum and bromine and the boiling point of the compound of gallium and bromine generated during the etching. A method for manufacturing a semiconductor device, comprising: