JPS59194436A - Dry etching method and device therefor - Google Patents

Abstract

PURPOSE:To perform an anisotropic etching without setting complicated conditions by generating a plasma by the emission of a light and the application of a high frequency electric field to a substance to be etched, suppressing an isotropic etching and performing the anisotropic etching. CONSTITUTION:Relatively small high frequency power is applied from a high frequency power source 5 to electrodes 7, 10 under reaction gas of the prescribed pressure and under the emission of a light of the specific wavelength to generate a high frequency electric field between the electrode. Since a large difference occurs between the etching velocities due to a plasma at the position to be emitted with a light of absorption wavelength and the shaded position, and anisotropic etching is substantially performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to dry etching used in semiconductor manufacturing processes, and in particular to a dry etching method for semiconductor substrates having large and finely integrated circuits, and a method that can be easily implemented. It is related to the device.

Conventionally, reactive ion etching equipment capable of anisotropic etching, in which etching progresses only in a certain direction, has been used to notch semiconductor substrates with large integration, high M degree, and miniaturized circuits. has been done. As shown in FIG. 1, this device controls the pressure in the circular part of the etching chamber 1 using an exhaust device 2 that evacuates the inside of the etching jig chamber 1, an automatic pressure control device 3, and a mass flow controller 4 that supplies a reaction gas into the etching chamber 1. While maintaining a constant reduced pressure state, high-frequency power is applied from a high-frequency power source 5 to an upper electrode 6 and a lower electrode 7, which are horizontal parallel plate electrodes provided opposite each other inside the etching chamber 1, to generate a plasma of a reactive gas. Then, the entire etching of the semiconductor substrate to be etched 8 placed on the upper surface of the lower electrode 7 is performed.

When etching is performed using such conventional equipment, multiple types of reaction gases are often used, and the optimum value is determined by determining the flow rate of these reaction gases, the overall pressure, and the amount of high-frequency power to be applied. This requires a lot of time and effort.

In order to determine the optimal value of the above-mentioned high-frequency power amount, if the applied amount of high-frequency power is increased, a strong cathode falling field effect will appear and crystal defects are likely to occur due to ion bombardment, so in order to prevent this, the pressure of the reaction gas must be increased. Then, isotropic etching occurs where side etching occurs, and problems such as minute circuit breaks appear. On the other hand, if the amount of high-frequency power applied is reduced, etching will not only be difficult to progress due to the deposition of one of the plurality of reactive gases, but also the above-mentioned isotropic etching will appear.

Furthermore, even on a single surface to be etched, the etching speed is different between the periphery and the center, resulting in poor etching uniformity. This is extremely difficult.

The present invention has been made to solve these problems, and it is an object of the present invention to provide a method for etching with high uniformity in which conditions can be easily determined, and an apparatus that can easily perform this method.

This will be explained in detail below with reference to the drawings.

FIGS. 2 and 6 are block diagrams of the apparatus of the present invention. Maintaining the inside of the etching chamber 9 at a constant reduced pressure is exactly the same as in the conventional example shown in FIG.

The object to be etched is placed on the upper surface of the horizontal parallel plate electrodes provided inside the notching chamber 9 so as to face each other. A second electrode (which is grounded through a power source 5 and which faces above the A electrode among the parallel plate electrodes)
Reference numeral 10 (hereinafter referred to as B electrode) is an annular flat plate, which is directly grounded. A light projection device 11 is provided above the central opening of the B electrode 10 so as to illuminate the object to be etched 8 placed on the upper surface of the A electrode 7 through the opening. The light projecting device 11 includes a light source 12. 'A luminous flux adjuster 13 and a filter 14 are provided. The light flux adjuster 13 in FIGS. 2 and 6 is a diffuser using a concave lens, but it may also be a condenser using a convex lens or a parapet surface reflector installed on the opposite side of the light source to create parallel reflected light. These selections are often determined by the light irradiation conditions.

In this embodiment, the light projecting device, the A electrode and the B electrode may be arranged vertically, or they may be arranged horizontally as shown in FIG. In this case, it goes without saying that the wafer 8 is held on the surface of the A electrode on the B electrode side.

Next, the etching method of the present invention will be explained while explaining the operation of each part shown in FIGS. 2 and 6. Before starting etching, the etching chamber 9 is
The inside of the unit is maintained at a predetermined reduced pressure. Note that, unlike the conventional example, a simple gas is used as the reaction gas in this case. After such a state is reached, the light source 12 is turned on, and the light flux adjuster is selected so as to achieve the desired irradiation state. When irradiating the entire surface of the object 8 to be etched, use a diffuser, and when only the central portion is to be irradiated, select either a mirror surface reflector or a condenser depending on the size of the irradiation range. The reason why only the central portion is irradiated is to make the etching rate uniform since the peripheral portion of the generally etched surface has a higher etching rate and the central portion has a lower etching rate.

Further, the filter 14 is one that mainly allows light having a wavelength absorbed by the material to be etched to pass through. This prevents over-etching since the underlying material that comes out after the etching of the etched material is completed is difficult to be etched because its absorption wavelength is different.

In this way, a relatively small high-frequency power is applied from the high-frequency power supply 5 to the opposing electrodes 7 and 1o under the irradiation of a reactant gas at a constant pressure and light of a specific wavelength, thereby generating a high-frequency electric field between the electrodes. Ru. In this case, the intensity of the high frequency power may be weak enough to make it difficult to generate plasma in the conventional example.

Here, the mechanism by which plasma is generated by weak high-frequency power as described above will be explained. Under constant reduced pressure,
When a surface to be etched is irradiated with light having a wavelength absorbed by the material to be etched, gas molecules on this surface become excited. When a high-frequency electric field is applied to gas molecules in such an excited state, the excited molecules easily turn into plasma, even in a weak electric field that makes it difficult to generate plasma under normal conditions, and subsequently, nearby neutral molecules also turn into plasma. I'm going to be done.

In this way, the most intense plasma formation occurs on the surface of the material to be etched, resulting in a large difference in the etching speed due to zero lasma between the area irradiated with the light of the absorption wavelength and the area in the shadow. , side etching is hardly performed, and substantially anisotropic etching is performed. In addition, since the irradiation is with light having the absorption wavelength of the material to be etched, when the etching of the material to be etched is completed and the underlying material appears, the absorption wavelength of this underlying material is different from that of the material to be etched, so the underlying material is Almost no gas excitation phenomenon occurs on the surface, and no locally strong plasma is generated, so that only weak plasma etching is performed overall.

Furthermore, conventionally, in order to satisfy each of the etching speed, etching selectivity between the material to be etched and the underlying material, etching anisotropy, and etching uniformity, appropriate amounts of reaction gases were mixed and used. Was.

For this reason, depending on the type of reaction gas, a deposition phenomenon may occur, and Kf agglomerates may accumulate on the surface to be etched, thereby interfering with the progress of etching. However, the method of the present invention uses only a simple reaction gas, and in order to ensure the above-mentioned etching rate, selectivity, anisotropy, and uniformity, the device is irradiated with light at the absorption wavelength of the material to be etched. No position phenomenon appears and the progress of etching is not obstructed.

Furthermore, since the applied high-frequency power is small, there is almost no damage to the surface to be etched due to ion bombardment by the generated plasma, and no crystal defects are caused by this.

If chlorine or chlorine-based gas is used as the reaction gas, turn off the high-frequency power after etching, increase the degree of vacuum, and irradiate the surface with long-wavelength light for a while to remove the chlorine adhering to the surface to be etched. Alternatively, since the chlorine-based gas can be evaporated, corrosion due to chlorine or the like will not occur even after the object to be etched is taken out from the etching chamber.

As described above, when cyanotching is performed using the method and apparatus of the present invention, anisotropic etching can be easily performed without setting complicated conditions and without causing damage such as crystal defects to the object to be etched. Because of this, it is possible to easily perform etching of highly precise and miniaturized circuits, and the practical effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional dry etching apparatus. FIGS. 2 and 6 are block diagrams of the dry etching apparatus of the present invention. In the figure, 5 is a high frequency power supply, 7 is an A electrode, 9 is an etching chamber, 10 is a B electrode, 11 is a light projection device, inside this is 12 a light source, 13 is a light flux adjuster, and 14 is a filter. Patent applicant: Toshihito Yamamoto, patent attorney representing Kokusai Denki Co., Ltd.

Claims (1)

[Claims] (1) In a dry etching method in which a semiconductor substrate having a highly integrated circuit is etched with high precision using high-frequency plasma, the surface of the material to be etched is irradiated with light in a specific wavelength band. A dry etching method characterized by bringing the gas molecules above into an excited state, applying a high frequency electric field to the excited gas molecules to generate plasma, and performing anisotropic etching by suppressing isotropic etching. 2. The dry etching method according to claim 1, wherein the light in the specific wavelength band is light at a wavelength absorbed by the material to be etched. 3. The dry etching method according to claims 1 and 2, wherein the entire surface of the surface to be etched is irradiated with light in the absorption wavelength band. 4. The dry etching method according to claims 1 and 2, in which the area to be irradiated with light in one wavelength band is a part of the surface to be etched. 5. In a dry etching device that etches semiconductor substrates with highly integrated circuits with high precision using high-frequency plasma, the object to be etched is placed on the top surface.
a first electrode formed and arranged horizontally, a second electrode facing substantially parallel to the first electrode and provided with an opening at the center; A dry etching apparatus comprising: a light projection device for irradiating the object to be etched placed on the first electrode with light in a specific wavelength band from above the opening of the second electrode. 6. In a dry etching apparatus for etching a semiconductor waveguide substrate having a large integrated circuit with high precision using high frequency plasma, a first electrode is arranged vertically and is adapted to hold an object to be etched on a side surface; a second electrode facing substantially parallel to the first electrode holding the object to be etched and having an opening in the center;
A dryer comprising: a light projection device that irradiates the object to be etched held on the surface of the first electrode with light in a specific wavelength band from the lateral direction through the opening of the second electrode. Etching equipment. 7. The dry etching apparatus according to claims 5 and 6, wherein the light projection device includes a light source, a luminous flux adjuster, and a filter that passes the light in the specific wavelength band. . 8. The dry etching apparatus according to claim 7, wherein the light flux adjuster is a condenser made of a convex lens. 9. The dry etching apparatus according to claim 7, wherein the light flux adjuster is a diffuser comprising a concave lens. 10. The dry etching apparatus according to claim 7, wherein the light flux adjuster is a parapet surface reflector that converts the beam into parallel beams.