JP3654438B2 - Dry etching method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to compound semiconductor materials such as GaAs, InP, GaP, InAs, and their compounds, such as InGaAsP, simple semiconductor materials such as Si and Ge, and insulating materials such as SiO ₂ , Si ₃ N ₄ , and Al ₂ O _3. In particular, the present invention relates to reactive dry etching.
[0002]
[Prior art]
Conventionally, when processing a substrate containing a semiconductor material typified by InP, GaAs, or Si and an insulating material such as SiO ₂ , Si ₃ N ₄ , or Al ₂ O ₃ into a desired pattern shape, these materials and chemicals are used. One or more kinds of reactive gases having a reactive property are introduced into a previously evacuated container, a reactive gas plasma is generated by a method such as discharge, and the active reactive species generated in the plasma are This was done by making it incident on the substrate surface.
[0003]
At this time, as a discharge form for generating plasma, a method in which high frequency power of 13.56 MHz is supplied between two electrodes arranged in a parallel plate shape and a glow discharge is generated between the electrodes is a reactive ion. This method is called etching (RIE) and 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 in which a substrate material is arranged are separated from each other, and the reactive reactive species are extracted from the plasma chamber and incident on the substrate material in the sample chamber is reactive ion beam etching (RIBE). ) And is used for processing semiconductor substrate materials.
[0005]
In these methods, active reactive species generated in plasma are involved in etching in a state where both ionic active reactive species in a charged state and neutral active reactive species not in a charged state are mixed. Become.
The ionic active reactive species has directivity by the ion sheath electric field formed on the substrate surface, and this brings about etching exhibiting anisotropy that is important in semiconductor processing technology.
[0006]
[Problems to be solved by the invention]
However, since the neutral active species described above are not affected by the electric field, the direction of movement is isotropic. For this reason, the etching caused by the neutral active species is isotropic, appears as a phenomenon that causes an undercut in the processed shape, and has become a big problem when trying to obtain etching rich in anisotropy .
In addition, the neutral active reactive species is in a chemically very active state, and spontaneously reacts with itself and the substrate material.
For this reason, it has become a big obstacle when manipulating the processing shape artificially.
[0007]
As described above, in the prior art, the discharge plasma of the reactive gas is used as the supply source of the ionic active species, so that the anisotropic etching is impaired together with the ionic active reactive species necessary for the anisotropic etching. Neutral active reactive species having properties are inevitably generated in the plasma, and it is difficult to realize good anisotropic etching.
[0008]
The present invention has been made in consideration of such circumstances, and the object of the present invention is to prevent the generation of neutral active reactive species that cause isotropic etching that appears as a phenomenon such as undercut. The present invention provides a dry etching method having excellent directivity.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the first aspect of the present invention comprises a first gas, which is a reactive gas having a property of chemically reacting with a substrate material to form a reaction product, and itself. An atomic beam or molecule generated from a second gas different from the first gas while being transported and supplied to the vicinity of the substrate surface via a plasma chamber in a state where no chemical reaction occurs spontaneously with the substrate material In a dry etching method in which a beam is incident on a substrate surface to chemically react the first gas and a substrate material, the first gas is bromine, and the first gas is introduced into the plasma chamber. As a method of transporting and supplying, by using the same route as the second gas supply route and controlling the supply amounts of the mixed first gas and second gas, only the second gas can be supplied. Discharge It said first gas contributes to Zuma allowed to not contribute to the discharge plasma, characterized by a state of an atomic beam or a molecular beam allowed to incident consists of only the second gas to the substrate.
[0012]
In order to achieve the above object, in the present invention, it is the maximum to supply the first reactive gas to be used to the substrate surface in a state in which the first reactive gas does not spontaneously react with the substrate material. It is a feature.
As one of the methods, in a dry etching method using discharge plasma, a reactive gas is not involved in the discharge.
Here, the fact that the reactive gas is not involved in the discharge means that the reactive gas is not put into a plasma state, and for this reason, the generation of neutral active reactive species that causes undercut and the like that does not cause anisotropic etching. Can be completely suppressed.
[0013]
Furthermore, since there is no generation of neutral active reactive species, the progress of the spontaneous reaction of the substrate material is suppressed, which has an effective effect on improving the controllability of processing.
At this time, the second particle beam is incident on the substrate for the purpose of causing the first reactive gas and the substrate material to react with each other on the substrate surface to generate a reaction product.
[0014]
[Action]
According to the present invention, since there is no neutral active reactive species in the situation where etching of the substrate proceeds, undercut or the like does not occur in the shape obtained by etching. In addition, the spontaneous reaction of the substrate material does not proceed.
Therefore, it is possible to process the substrate material with very high accuracy.
For example, taking a semiconductor optical waveguide as an example, the dimensions of the waveguide can be strictly determined, and it becomes possible to manufacture a semiconductor waveguide with very good performance.
[0015]
【Example】
Examples according to the present invention will be described below.
[0016]
[ Reference example ]
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 10 is evacuated by an evacuation system 11. In the sample chamber 10, a sample 1 to be processed is placed on a sample stage 12. Moreover, the code | symbol 13 in a figure shows the plasma chamber for producing | generating a 2nd particle beam. The plasma chamber 13 is equipped with a gas inlet 14 for introducing a raw material gas for the second particle beam generating plasma. Further, microwaves are introduced into the plasma chamber 13 from a microwave generation source 15 so that plasma can be generated by microwave discharge. In the figure, reference numeral 16 denotes a drawing grid for drawing a second particle beam from the plasma and making it incident on the sample. By applying a voltage to the grid 16, a particle beam having energy corresponding to the voltage is shown. Can be obtained. In the figure, 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 this reference example, in order to obtain a uniform supply to the sample surface, a ring-shaped introduction mechanism surrounding the sample is used. However, the present invention is not limited to this.
[0017]
In this reference example, InP crystal, which is a typical compound semiconductor, was used as sample 1, but the present invention is not limited to this. Moreover, although the particle beam taken out from the plasma produced | generated with Ar gas is used as a 2nd particle beam, this invention is not limited to this.
[0018]
While the sample 1 was kept at a temperature of 100 ° C., Ar gas was introduced into the plasma chamber 13 from the gas inlet 14 while the flow rate was controlled using the flow rate controller 18.
At this time, the pressure of Ar gas is 2.0 × 10 ⁻⁴ torr.
Next, a 100-watt microwave was introduced into the plasma chamber 13 from a microwave source.
When the applied voltage to the grid 16 was 400 volts, a second particle beam of 1.5 mA / cm ² in terms of current value was obtained.
Simultaneously with the generation of the second particle beam, bromine gas (Br ₂ ) was introduced from the gas inlet 17 provided in the sample chamber 10 via the flow rate controller 19. The partial pressure of Br ₂ gas at this time is 0.9 × 10 ⁻⁴ torr.
[0019]
FIG. 2 shows a cross-sectional observation view of the processed shape of the sample 1 obtained when the particle beam irradiation for 20 minutes is performed in this state. This figure is an explanatory view of the observation result of 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. As shown in FIG. 2, the processed shape obtained in this reference example is 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 that. The etching amount at this time is 0.1 micron per minute, and from this etching amount, extremely accurate etching can be realized by this method.
[0020]
Further, it was confirmed that the etching on the sample 1 did not proceed in the absence of the second particle beam irradiation.
This means that in a state where the first reactive gas is introduced, no spontaneous reaction occurs between the first reactive gas and the substrate material.
[0021]
For comparison, the conventional method was also performed using the same apparatus.
That is, Br ₂ gas, which is a reactive gas, was introduced into the plasma chamber from the gas inlet 14, plasma was generated by introducing microwaves, and a voltage was applied to the grid 16 to draw out the particle beam and enter the sample. .
FIG. 3 shows a cross-sectional observation result of the processed shape obtained by this method.
The side wall 21b entered the inside from the end of the SiO ₂ film 20 of the etching mask, and undercut was observed.
Although the processing was carried out 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 introduced gas to Cl ₂ , the undercut could not be eliminated.
This is because, once the reactive gas is brought into a plasma state, a neutral active reactive species is inevitably generated, and the isotropic movement of the neutral active reactive species and the spontaneous reaction between the substrate material possessed by it. This is because sex brings an undercut.
[0022]
[Example 1 ]
In the reference example , the first reactive gas and the gas for generating the second particle beam are introduced into the apparatus through different paths. However, in the present embodiment, the first reactive gas and the second particle beam are introduced into the apparatus. The result of introducing the gas for generation through the same route will be described. As shown in FIG. 4, the first reactive gas Br ₂ and Ar, which is a gas for generating the second particle beam, pass through the respective flow rate controllers 18 and 19 and then the plasma chamber 13. It is mixed before being introduced into.
[0023]
In this state, a beam was extracted from the microwave plasma generated as described in the reference example and made incident on the sample. At this time, the flow rate of Ar is 4.5 cm ³ per minute. When the flow rate of the reactive gas Br ₂ is 2.0 cm ³ or more per minute, the processed shape exhibits an undercut. However, at a flow rate below this, the processed shape exhibiting a vertical side wall as shown in FIG. 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 there are no neutral active reactive species that cause undercuts. The etching amount in this example was approximately 0.1 microns per minute.
[0024]
[Example 2 ]
If reference example, in Example 1 showed the example using the particle beam where obtained by a discharge plasma of the gas as the second particle beam, in this embodiment using electrons as the second particle beam The result of is described.
[0025]
When using electrons as the second particle beam, as shown in FIG. 5, a device in which a thermionic emission filament 30 is attached to the plasma chamber 13 is used.
The filament 30 emits electrons due to the current applied from the current source 31, but by using the bias power source 32 to bias the circuit composed of the current source 31 and the filament 30 negatively with respect to the substrate potential, A beam consisting of electrons as a second particle beam was obtained.
[0026]
In this manner, Br ₂ as the first reactive gas was introduced from the introduction port 17 to a pressure of 0.9 × 10 ⁻⁴ torr as in the case of the reference example . When a beam made of electrons as the second particle beam was incident on the sample for 40 minutes, the obtained processed shape had vertical sidewalls similar to the processed shape shown in FIG. 2 as shown in the reference example .
[0027]
In the above-described embodiments, the case where the processed sample is an InP crystal has been described. However, the method according to the present invention can be applied to a compound semiconductor material such as GaAs, a simple semiconductor material such as Si, and an insulating material such as SiO _2. The applicability is clear from the principle.
[0028]
【The invention's effect】
As described above, by using the method according to the present invention, neutral active reactive species that cause isotropic etching such as undercut and spontaneous chemical reactivity with the substrate material when etching is performed. Since generation can be completely suppressed, etching rich in anisotropy becomes possible.
Since this anisotropy is caused by the second particle beam, it is possible to obtain a machining shape having an arbitrary angle as well as machining perpendicular to the substrate surface by setting the angle formed by the particle beam and the substrate. it can.
Furthermore, in the present invention, since the etching of the substrate material proceeds only after the irradiation with the second particle beam, 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 a reference example of the present invention.
FIG. 2 is a diagram of a cross-sectional observation result of a processed shape of an InP crystal obtained by a reference example of the present invention.
FIG. 3 is 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 Example 1 of the present invention.
FIG. 5 is a schematic configuration diagram of an apparatus used in Example 2 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sample 10 Sample chamber 11 Vacuum exhaust system 12 Sample stage 13 Plasma chamber 14 Gas inlet 15 Microwave generation source 16 Drawer grid 17 Gas inlet 18 Flow controller 19 Flow controller 20 SiO ₂ film 21 InP crystal 21a, 21b Side wall 30 Thermionic filament 31 Power source 32 Bias power source

Claims (1)

  The first gas, which is a reactive gas having a characteristic of chemically reacting with the substrate material to form a reaction product, is in a state where it does not spontaneously cause a chemical reaction and the plasma chamber Through the substrate surface, an atomic beam or a molecular beam generated from a second gas different from the first gas is incident on the substrate surface, and the first gas and the substrate material are brought into contact with each other. In the dry etching method in which chemical reaction is performed, the first gas is made of bromine, and as a method of transporting and supplying the first gas to the plasma chamber, the same path as the second gas supply path is used. By controlling the supply amounts of the mixed first gas and second gas, only the second gas contributes to the discharge plasma, but the first gas contributes to the discharge plasma. Strangely allowed, dry etching method, characterized by a state of an atomic beam or a molecular beam allowed to incident consists of only the second gas to the substrate.

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