JPH04129219A - Dry etcher - Google Patents

Abstract

PURPOSE:To realize anisotropic etching by dry system by introducing the atomized carrier gas into a hermetic container and by impressing it with electric fields to control wafer temperature. CONSTITUTION:A mist of chemical liquid introduced through a gas inlet tube 4 is electrified by the friction between gas and chemical liquid and therefore undergoes migration of uniform directionality. Therefore, the mist descends anisotropically onto a workpiece film 8 on a wafer 1, and this film is etched by chemical reaction with a photoresist 9 as the mask. Further, setting wafer temperature below 0 deg.C freezes etching reaction on the side wall of a workpiece film under etching with the result that anisotropic etching can be realized by dry system with a photoresist as the mask.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wet etching apparatus, and more particularly to a wet etching apparatus capable of realizing an anisotropic etched shape.

[Conventional technology]

As shown in the perspective view of FIG. 2, a conventional wet etching apparatus includes a rectangular parallelepiped-shaped container 10 filled with a chemical solution.
An apparatus for etching a plurality of wafers 1 by immersing them in a carrier 11, and a wafer in which a chemical solution is ejected from a nozzle 12 and the spray of the chemical solution is rotated by a spin chuck 13, as shown in the schematic diagram of FIG. 1 is known.

On the other hand, as a conventional anisotropic etching apparatus, a dry etching apparatus is generally used, as shown in the schematic diagram of FIG. In this case, the gas exhaust port 14 and the gas inlet port 1
Usually 400KH in a vacuum container 16 with 5
Etching is performed using ions and plasma by placing the wafer 1 in an ionized gas plasma generated between two parallel electrodes 7 connected to a high frequency oscillator 17 of 56 MHz or 13°.

In general, anisotropic etching equipment uses directional ions to achieve anisotropic etching through physical action, and equipment that etches the material to be processed through chemical action using ions or radicals. At the same time, an apparatus is known that realizes anisotropic etching by forming a protective film on the side wall of the material to be processed to inhibit the etching reaction.

[Problem to be solved by the invention]

In the above-mentioned conventional wet etching apparatus, etching progresses by a chemical reaction in the chemical solution, so the etched shape is isotropic, and an anisotropic etched shape cannot be realized.

In addition, in dry etching equipment that can realize anisotropic etched shapes using conventional technology, etching is performed using ion kinetic energy, so the selectivity ratio between the film to be processed and the underlying film of the film to be processed is sufficiently increased. It is difficult to do so. For example, in the process of selectively removing a polycrystalline silicon film containing phosphorus by dry etching to form a gate electrode, the selectivity ratio between the polycrystalline silicon film and the oxide film underlying it is approximately 10 to 10. It is about 20. Therefore, especially when the thickness of the oxide film is as thin as 100A or less, the oxide film is also etched by a slight overetching, and S
There was a problem that i was exposed and the characteristics of the MOSFET deteriorated.

Furthermore, in the case of a dry etching apparatus, since charged particles are used for etching, the photoresist and the film to be processed are charged. For example, in the process of forming the gate electrode, the photoresist or polycrystalline silicon film that serves as a mask is likely to be charged, creating a potential difference between the semiconductor substrate and the photoresist, and in some cases short circuiting may occur, causing the gate electrode to become electrically charged. There was a problem with it being destroyed.

Furthermore, in the case of dry etching, ions also collide with the side walls of the reaction chamber vacuum chamber and the electrodes, so F is removed from the side walls and electrodes.
There is a problem in that heavy metals such as e.g. adhere to the wafer due to the sputtering effect, resulting in contamination.

The present invention provides a wet etching apparatus which can realize an anisotropic etched shape and solves the problems associated with anisotropic etching using a dry etching apparatus.

[Means to solve the problem]

The wet etching apparatus of the present invention includes a gas introduction pipe for introducing a carrier gas containing a mist chemical into a closed container;
It has an electrode that applies an electric field to the sealed container, and a temperature controller that cools the wafer placed in the sealed container.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram of a wet etching apparatus according to an embodiment of the present invention.

The wafer 1 is held on a wafer holder 2 connected to a wafer temperature controller 3 that can control the temperature in the range of -20°C to +50°C, and the wafer holder 2 introduces a carrier gas containing a mist chemical solution. It is installed in a closed container 6 having a gas inlet pipe 4 and a gas exhaust pipe 5. The closed container 6 is placed in an electric field having a gradient generated between the electrodes 7a and 7b.

The chemical mist introduced into the closed container 6 from the gas introduction pipe 4 becomes electrically charged due to friction between the gas and the chemical during its formation process, and therefore moves in a uniform direction within the electric field. Therefore, the chemical mist falls anisotropically onto the workpiece M8 on the wafer 1, and the workpiece film 8 is etched by a chemical reaction using the photoresist 9 as a mask.

In addition, by setting the wafer temperature below 0℃,
In particular, the etching reaction on the side wall of the film being etched is frozen, while etching continues on the surface being etched due to mist collisions, exothermic reactions, and the like. As a result of the above, anisotropic etching can be achieved by wet etching using a photoresist as a mask.

As a specific example of the above, a case will be described in which a gate electrode is formed by anisotropically etching polycrystalline silicon containing phosphorus. A polycrystalline silicon film can be wet-etched using a mixed solution of HF and HNO. HF
After mixing HNOg and pure water at a ratio of 1:50:100, nitrogen gas is made into a mist as a carrier gas, and the mist is introduced into a closed container within an electric field. The wafer holder temperature is set to 0°C using a temperature controller.

Under the above setting conditions, a polycrystalline silicon film with a layer resistance of 10 to 20 Ω/hole has an etching rate of 300A 7m.
It is etched at in ~5008/min. In this case, the reaction does not proceed on the sidewalls of the polycrystalline silicon film because the mist has directionality. Etching progresses on the etched surface of the polycrystalline silicon film due to collision of directional mist and exothermic reaction.

As a result, anisotropic etching of the polycrystalline silicon film can be achieved. In addition, in this case, the selectivity with the base oxide film is 30
0 to 1000 is obtained, and no charge-up occurs, so no breakdown of the insulation film occurs. In addition, there is less heavy metal contamination caused by sputtering the side walls of the reaction chamber and the like.

〔Effect of the invention〕

As explained above, the present invention has the unique effect of being able to achieve anisotropic etching by wet etching, which was not possible with conventional techniques, and also improves the ability to remove mask materials, which was a problem with dry anisotropic etching. This has the effect that the selectivity ratio between the photoresist and the film to be processed, and the selectivity between the film to be processed and its base film, which were small and insufficient, can be greatly improved. Further, there are also effects such as no breakdown of the insulating film due to charge-up, which was a problem with the dry etching method, and very little heavy metal contamination.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a wet etching apparatus according to an embodiment of the present invention, FIGS. 2 and 3 are perspective views and schematic diagrams of a conventional wet etching apparatus, and FIG. 4 is a conventional dry anisotropic etching apparatus. FIG. DESCRIPTION OF SYMBOLS 1... Wafer, 2... Wafer holder, 3... Temperature controller, 4... Gas introduction pipe, 5... Gas exhaust pipe, 6... Airtight container, 7.7a, 7b... electrode,
8... Film to be processed, 9... Photoresist, 10...
・Container, 11...Carrier, 12...Nozzle, 13
...Spin chuck, 14...Gas exhaust port, 15.
...Gas inlet, 16...Vacuum container, 17...High frequency oscillator. Kazu Punishment Haze District

Claims (1)

[Claims] The invention is characterized by having a gas introduction pipe for introducing a carrier gas containing a mist-formed chemical into a sealed container, an electrode for applying an electric field to the sealed container, and a temperature controller for cooling a wafer placed in the sealed container. wet etching equipment.