TECHNICAL FIELD

The present invention relates to a plasma processing apparatus and a plasma processing method, and particularly relates to a plasma processing apparatus and a plasma processing method that perform etching processing and that are suitable for processing deep holes or deep trenches having high aspect ratio.

BACKGROUND ART

Semiconductor devices having a three-dimensional structure are manufactured and miniaturization and multi-layering of patterns to be formed are in progress.

For example, in a NAND flash memory device having a three-dimensional structure, it is necessary to form a via or a trench that penetrates a stacked film formed by stacking a number of pairs of polycrystalline silicon (poly-Si) films and silicon oxide (SiO2) films, or by stacking a number of pairs of silicon nitride (SiN) films and silicon oxide (SiO2) films.

PTL 1 discloses a technique for processing a SiO2(poly-Si or SiN or WSi) stacked film by using a gas containing nitrogen trifluoride (NF3) and fluoromethane (CH3F).

It is disclosed in PTL 2 that, in a cryogenic environment in which the temperature of a wafer is −30° C. or lower, a stacked film of a silicon oxide film and a silicon nitride film is etched by using a processing gas as a first processing gas, which contains hydrogen (H2), carbon tetrafluoride (CF4) and trifluoromethane (CHF3), and the stacked film of a silicon oxide film and a silicon nitride film is etched by using a processing gas as a second processing gas, which contains hydrogen (H2), carbon tetrafluoride (CF4), trifluoromethane (CHF3) and hydrogen bromide (HBr).

PRIOR ART LITERATURE

Patent Literature

PTL 1: JP-A-2015-144158

PTL 2: JP-A-2017-103388

SUMMARY OF INVENTION

Technical Problem

When the number of stacked layers of a device having a three-dimensional structure increases with integration, a ratio of a depth to an opening width, that is, an aspect ratio of a deep hole or a deep trench that penetrates a stacked film, increases. As the aspect ratio increases, the etching rate may decrease and a tapered shape may be formed. That is, it can be said that it is difficult to obtain an aspect ratio of a certain value or more. PTLs 1 and 2 describe methods for improving the tapered shape, but the decrease in etch rate is not taken into consideration. In the case where the etching rate decreases as the aspect ratio increases, processing time increases exponentially for obtaining a processed shape having a high aspect ratio, and the throughput of plasma processing is seriously affected.

In order to solve the above-mentioned problems in the related art, the invention provides a plasma processing apparatus and a plasma processing method for realizing a plasma etching method by which the tapered shape is improved and the decrease in etch rate is prevented.

Solution to Problem

In order to solve the above-mentioned problems, in the invention, there is provided a plasma processing method in which a first stacked film formed by alternately stacking a silicon oxide film and polycrystalline silicon, or a second stacked film formed by alternately stacking a silicon oxide film and a silicon nitride film, is etched by using a plasma. The first stacked film or the second stacked film is etched by using a mixed gas of a hydrogen bromide gas, a hydrofluorocarbon gas and a nitrogen element-containing gas.

In order to solve the above-mentioned problems, in the invention, there is provided a plasma processing method in which a stacked film formed by alternately stacking a silicon oxide film and a silicon nitride film is etched by using a plasma. The stacked film is etched by using a mixed gas of a hydrogen bromide gas, a fluoromethane (CH3F) gas and a nitrogen gas.

In order to solve the above-mentioned problems, in the invention, there is provided a plasma processing method in which a first stacked film formed by alternately stacking a silicon oxide film and polycrystalline silicon, or a second stacked film formed by alternately stacking a silicon oxide film and a silicon nitride film, is etched by using a plasma. The first stacked film or the second stacked film is etched by using a mixed gas of a fluoromethane (CH3F) gas, a nitrogen gas and a chlorine gas, or by using a mixed gas of a fluoromethane (CH3F) gas, a nitrogen gas, and a boron trichloride (BCl3) gas .

In order to solve the above-mentioned problems, in the invention, there is provided a plasma processing method in which a stacked film formed by alternately stacking a silicon oxide film and a metal film is etched by using a plasma. The stacked film is etched by using a mixed gas of a hydrogen bromide gas, a fluoromethane (CH3F) gas and a nitrogen element-containing gas.

In order to solve the above-mentioned problems, in the invention, there is provided a plasma processing apparatus that includes : a processing chamber in which a sample is subjected to plasma processing; a first radio frequency power source that supplies radio frequency power for generating a plasma; a sample stage on which the sample is placed; a second radio frequency power source that supplies radio frequency power to the sample stage; and a control unit that controls the first radio frequency power source and the second radio frequency power source so as to etch a stacked film formed by alternately stacking a silicon oxide film and a polycrystalline silicon, or a stacked film formed by alternately stacking a silicon oxide film and a silicon nitride film, by using the plasma generated by a mixed gas of a hydrogen bromide gas, a hydrofluorocarbon gas and a nitrogen element-containing gas.

In order to solve the above-mentioned problems, in the invention, there is provided a plasma processing apparatus that includes: a processing chamber; an upper electrode disposed on an upper side in the processing chamber; a sample stage that is disposed on a lower side in the processing chamber opposite the upper electrode and on which a sample to be processed is placed; a gas supply unit that supplies an etching gas to the processing chamber; a radio frequency power applying unit that applies radio frequency power to the upper electrode; a temperature measurement unit that measures temperature of the sample stage; a cooling gas supply unit that supplies a cooling gas to between the sample to be processed placed on the sample stage and the sample stage; a refrigerant circulation unit that circulates a temperature-controlled refrigerant in a flow path formed inside the sample stage; and a control unit that controls the gas supply unit, the radio frequency power applying unit, the cooling gas supply unit and the refrigerant circulation unit. At time of controlling the gas supply unit and the radio frequency power applying unit to generate a plasma in the processing chamber so as to perform plasma etching processing on the sample to be processed placed on the sample stage, the control unit, according to temperature information of the sample stage measured by the temperature measurement unit and based on a relationship stored in advance between temperature of the sample stage and temperature of the sample to be processed placed on the sample stage, controls the cooling gas supply unit and the refrigerant circulation unit so as to maintain the temperature of the sample to be processed at a predetermined temperature during the plasma etching processing. The gas supply unit is controlled by the control unit to supply a mixed gas as the etching gas into the processing chamber so as to form a compound, which has an effect of promoting the plasma etching processing of the sample to be processed, on a surface of the sample to be processed which is maintained at the predetermined temperature.

Advantageous Effect

According to the invention, in a process of forming a deep hole or a deep trench having a high aspect ratio in a stacked film of a silicon-containing film and a silicon oxide film by plasma etching, the decrease in etch rate can be prevented and the processing throughput can be improved. Further, the cross-sectional shape of the deep hole or the deep trench can be made vertical.

