JP3296392B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to GaAs, InP, Ga
P, InAs and their compounds, InGaAs
The present invention relates to a dry etching method for a compound semiconductor material such as sP, a simple semiconductor material such as Si and Ge, and an insulating material such as SiO ₂ , Si ₃ N ₄ , and Al ₂ O ₃ , and more particularly to a reactive dry etching.

[0002]

2. Description of the Related Art Conventionally, semiconductor materials such as InP, GaAs and Si, and SiO ₂ , Si ₃ N ₄ and Al ₂
When processing a substrate containing an insulating material such as O ₃ into a desired pattern shape, one or more kinds of reactive gases having a property of chemically reacting with these materials are introduced into a pre-evacuated container. Then, a plasma of a reactive gas is generated by a method such as electric discharge, and active reactive species generated by the plasma are incident on the substrate surface.

[0003] At this time, as a discharge mode for generating plasma, 13.2 is provided between two electrodes arranged in a parallel plate shape.
A method of supplying high frequency power of 56 MHz and causing glow discharge between the electrodes is reactive ion etching (R
IE), which is widely used.

[0004] In this RIE, a substrate material to be processed is disposed on one electrode. In addition, a method in which a plasma chamber for generating active reactive species and a sample chamber for disposing a substrate material are provided in separate spaces, and active reactive species are drawn from the plasma chamber and incident on the substrate material of the sample chamber is known as reactive ion beam etching (RIBE) ), Which is used for processing semiconductor substrate materials.

In these methods, active reactive species generated in plasma are involved in etching in a state in which both ionic active reactive species in a charged state and neutral active reactive species in a non-charged state are mixed. Will be done. The ionic active reactive species have directivity due to the ion sheath electric field formed on the substrate surface, which results in anisotropic etching which is important in semiconductor processing technology.

[0006]

However, since the above-mentioned neutral active species is not affected by the electric field, the movement direction is isotropic. For this reason, the etching caused by the neutral active species is isotropic, and appears as a phenomenon such as causing an undercut in the processed shape, which has been a major problem when trying to obtain an etching rich in anisotropy. . Neutral reactive species are also very chemically active,
The material itself and the substrate material undergo a spontaneous chemical reaction. For this reason, this has been a major obstacle when manipulating the processed shape artificially.

As described above, in the prior art, the discharge plasma of the reactive gas is used as a source of the ionic active species. Neutral active reactive species having the property of impairing etching are inevitably generated in the plasma, and thus it has been difficult to achieve good anisotropic etching.

The present invention has been made in view of such circumstances, and an object of the present invention is to prevent the generation of neutral active reactive species which cause isotropic etching which appears as a phenomenon such as undercut. Another object of the present invention is to provide a dry etching method excellent in anisotropy.

[0009]

In order to achieve the above object, a dry etching method according to the present invention is characterized in that when a substrate is processed into a desired pattern shape, the substrate reacts chemically with a substrate material to form a reaction product. the first gas and the first gas allowed to occur to a reactive dry etching which uses only different second gas, chemically react with the reaction product and the substrate material temperature is held at 100 ° C. a first gas comprising a reactive gas having a property of forming a itself and the substrate
In a state where the material does not produce a spontaneous chemical reaction, through the plasma chamber for the first gas and the substrate material to produce than an atomic beam or molecular beam to raise the chemical reactions second gas converting mechanism transports supplied to the substrate surface and allowed incident the atom beam or molecular beam to the substrate surface, chemically reacted with said first gas and the substrate material, and the first gas to the plasma chamber methods transport supplies, using the same path as the second gas supply path, by controlling the respective supply amounts of the first gas and the second gas are mixed, only the second gas Release
The first gas is a discharge plasma
And the atomic beam or the molecular beam incident on the substrate is made of only the second gas.

[0010]

[0011]

[0012]

In order to achieve the above object, in the present invention, the first reactive gas to be used is supplied to the substrate surface in a state where the first reactive gas does not react spontaneously with the substrate material. Is the biggest feature. As one of the methods, in a dry etching method using discharge plasma, a reactive gas is not involved in discharge. Here, the fact that the discharge plasma does not cause the reactive gas to participate in the discharge means that the reactive gas is not turned into a plasma state, and therefore, the neutral active reaction which causes an undercut or the like that does not impair the anisotropic etching. Seed production can be completely suppressed. Furthermore, since there is no generation of neutral reactive species, the progress of spontaneous reaction of the substrate material is suppressed, which has an effective effect on improving the controllability of processing. At this time, the first reactive gas and the substrate material are mutually reacted on the substrate surface, and the second particle beam is incident on the substrate for the purpose of generating a reaction product.

[0014]

According to the present invention, the undercut or the like does not occur in the shape obtained by the etching because the neutral reactive species does not exist in the situation where the etching of the substrate proceeds. Further, the spontaneous reaction of the substrate material does not proceed. Therefore,
The substrate material can be processed with very high precision. For example, when taking a semiconductor optical waveguide as an example, the dimensions of the waveguide can be strictly determined, and it is possible to manufacture a semiconductor waveguide having extremely high performance.

[0015]

Embodiments of the present invention will be described below.

[ Reference Example 1] FIG. 1 is a schematic view showing an apparatus used in a reference example of the present invention. In the figure, reference numeral 10 denotes a sample chamber, and the sample chamber 1
0 is evacuated by the evacuation system 11. In the sample chamber 10, a sample 1 to be processed is arranged on a sample stage 12. Reference numeral 13 in the drawing indicates a plasma chamber for generating a second particle beam. The plasma chamber 13 is provided with a gas inlet 14 for introducing a source gas for the second particle beam generating plasma. Further, a microwave is introduced from the microwave generation source 15 into the plasma chamber 13 so that plasma can be generated by microwave discharge. In the drawing, reference numeral 16 denotes an extraction grid for extracting a second particle beam from the plasma and making the second particle beam incident on the sample. By applying a voltage to the grid 16, a particle beam having energy corresponding to the voltage is obtained. Can be obtained.
In the drawing, reference numeral 17 denotes a gas introduction mechanism for transporting a first gas, which is a reactive gas chemically reacting with the substrate material, to the vicinity of the substrate surface. In order to obtain a uniform supply to the sample surface in this reference example, although the introducing mechanism of the ring-shaped surrounding the sample, the present invention is not limited thereto.

[0017] In this reference example, as the sample 1, it was used InP crystal where a representative compound semiconductor, the present invention is not limited thereto. Further, a particle beam extracted from plasma generated by Ar gas is used as the second particle beam, but the present invention is not limited to this.

The Ar gas was introduced into the plasma chamber 13 from the gas inlet 14 while maintaining the sample 1 at a temperature of 100 ° C. and controlling the flow rate of Ar gas using a flow controller 18. At this time, the pressure of the Ar gas is 2.0 × 10 ⁻⁴ torr. Next, a microwave of 100 watts was introduced into the plasma chamber 13 from a microwave source. When the voltage applied to the grid 16 is 400 volts, it is converted to a current value of 1.5.
A second particle beam of mA / cm ² was obtained. This second
At the same time as generating the particle beam, bromine gas (Br ₂ ) was introduced from a gas inlet 17 provided in the sample chamber 10 via a flow controller 19. The partial pressure of the Br ₂ gas at this time is 0.9 × 10 ⁻⁴ torr.

FIG. 2 is a cross-sectional observation view of the processed shape of the sample 1 obtained when the particle beam irradiation is performed for 20 minutes in this state.
Shown in This figure is an explanatory diagram of the observation result obtained by observing the sample using a scanning electron microscope. In FIG. 2, reference numeral 20 indicates an SiO ₂ film used as an etching mask, and reference numeral 21 indicates an InP crystal of the processed sample 1. FIG.
As shown in the figure, the processed shape obtained in the present reference example has a ridge shape having a side wall 21a perpendicular to the surface of the InP crystal 20 of the sample 1 from the end of the SiO ₂ film 20 of the etching mask. I understand. At this time, the etching amount is 0.1 micron per minute. From this etching amount, according to the present method, extremely accurate etching can be realized.

Further, it was confirmed that the etching of the sample 1 did not proceed without the irradiation of the second particle beam. This means that no spontaneous reaction occurs between the first reactive gas and the substrate material when the first reactive gas is introduced.

For comparison, the conventional method was performed using the same apparatus. That is, Br ₂ gas, which is a reactive gas, was introduced into the plasma chamber from the gas introduction port 14, plasma was generated by applying microwaves, and a particle beam was extracted by applying a voltage to the grid 16 to be incident on the sample. . FIG. 3 shows a cross-sectional observation result of the processed shape obtained by this method. The side wall 21b penetrated inside from the end of the SiO ₂ film 20 of the etching mask, and an undercut was observed. The processing was performed by changing the pressure of the gas to be introduced, the power of the microwave to be introduced, and the voltage to be applied, and further changing the gas to be introduced to Cl _2. However, the undercut could not be eliminated. This means that once the reactive gas is brought into the plasma state, neutral reactive species are inevitably generated, and the isotropic motion of the neutral reactive species and the spontaneous reaction between the neutral reactive species and the substrate material possessed by them This is because the nature causes an undercut.

[0022] [Example 1] Although in Reference Example 1 was introduced into the apparatus with a different route of gas for generating a first reactive gas and the second particle beam, the first reaction in this example The result of introducing the neutral gas and the gas for generating the second particle beam through the same path will be described. Br as the first reactive gas
Ar and a gas for generating the _second and second particle beams
As shown in FIG. 4, each of the flow controllers 18, 1
After passing through 9, it is mixed just before being introduced into the plasma chamber 13.

In this state, a beam was extracted from the microwave plasma generated in the manner described in Example 1 and made incident on the sample. At this time, the flow rate of Ar was 4.5 cm per minute.
³ The flow rate of the reactive gas Br ₂ is 2.0 c / min.
At m ³ or more, the processed shape exhibited an undercut, but at a flow rate less than this, a processed shape having vertical side walls as shown in FIG. 2 was obtained. This is because when the flow rate of Br ₂ is small, the discharge plasma is substantially generated by Ar gas for generating the second particle beam, and the reactive gas Br ₂ does not contribute to the discharge plasma. This is because neutral reactive species causing undercut are not generated. The etching amount in the case of the present embodiment was approximately 0.1 micron per minute.

[Embodiment 2 ] In Embodiments 1 and 1, an embodiment using a particle beam obtained by gas discharge plasma as the second particle beam has been described. The result when electrons are used as the particle beam will be described.

When using electrons as the second particle beam, an apparatus having a thermoelectron emission filament 30 attached to the plasma chamber 13 as shown in FIG. 5 was used. The filament 30 emits electrons by a current applied from a current source 31.
By using the bias power supply 32 for the circuit consisting of
By applying a negative bias to the substrate potential, a beam composed of electrons was obtained as a second particle beam.

In this manner, Br ₂ as the first reactive gas was introduced through the inlet 17 to 0.9 × 10 ^{-4 in the same} manner as in Reference Example 1.
Introduced to a pressure of torr. It was incident beam of electrons is a second particle beam 40 min sample, resulting machining shape is the place shown in Reference Example 1 2
The vertical side wall similar to the processing shape shown in FIG.

In the above embodiment, the processing sample is In
Although the case of a P crystal has been described, a compound semiconductor material such as GaAs, a simple semiconductor material such as Si,
It is clear from the principle that the method according to the present invention can be applied to an insulating material such as O ₂ .

[0028]

As described above, when the method according to the present invention is used, isotropic etching such as undercutting and spontaneous chemical reactivity with a substrate material are performed when performing etching. Since the generation of reactive reactive species can be completely suppressed, anisotropic etching becomes possible.
Since this anisotropy is caused by the second particle beam, by setting the angle between the particle beam and the substrate, it is possible to obtain a processed shape having an arbitrary angle as well as processing perpendicular to the substrate surface. it can. Further, in the present invention, since the etching of the substrate material proceeds only when the irradiation of the second particle beam is present, the operability of the processed shape is extremely excellent.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus used in Reference Example 1 of the present invention.

FIG. 2 is a view of a cross-sectional observation result of a processed shape of an InP crystal obtained by Reference Example 1 of the present invention.

FIG. 3 is a view showing a cross-sectional observation result of a processed shape when an InP crystal is etched by a conventional method.

FIG. 4 is a schematic configuration diagram of an apparatus used in Embodiment 1 of the present invention.

FIG. 5 is a schematic configuration diagram of an apparatus used in Embodiment 2 of the present invention.

[Explanation of symbols]

1 Sample 10 Sample chamber 11 a vacuum evacuation system 12 sample table 13 plasma chamber 14 gas inlet 15 microwave generating source 16 for leading out the grid 17 gas inlet 18 flow controller 19 flow controller 20 SiO ₂ film 21 InP crystals 21a, 21b Side wall 30 Thermionic filament 31 Power supply 32 Bias power supply

Claims (1)

(57) [Claims] In processing a substrate into a desired pattern shape, only a first gas which chemically reacts with a substrate material to generate a reaction product and a second gas different from the first gas are used. A reactive dry etching method, wherein a first gas, which is a reactive gas having a characteristic of forming a reaction product by chemically reacting with a substrate material maintained at a temperature of 100 ° C., is formed by itself and a substrate material. Is a spontaneous chemical reaction
The state does not occur, together with the first gas and the substrate material is transported supplied to the substrate surface via a plasma chamber for generating from the second gas with an atomic beam or molecular beam to raise the chemical reaction A method of causing the atomic beam or the molecular beam to be incident on a substrate surface to chemically react the first gas with a substrate material, and transporting and supplying the first gas to the plasma chamber. Using the same path as the gas supply path of 2,
By controlling the supply amounts of the mixed first gas and second gas, only the second gas is discharged.
The first gas contributes to plasma, but the first gas
A dry etching method , wherein an atomic beam or a molecular beam incident on the substrate is made of only the second gas so as not to contribute .