Plasma etching method and plasma processing apparatus
Provided is a plasma etching method which enables etching with high accuracy while controlling and reducing surface roughness of a transition metal film. The etching is performed for the transition metal film, which is formed on a sample and contains a transition metal element, by a first step of isotropically generating a layer of transition metal oxide on a surface of the transition metal film while a temperature of the sample is maintained at 100° C. or lower, a second step of raising the temperature of the sample to a predetermined temperature of 150° C. or higher and 250° C. or lower while a complexation gas is supplied to the layer of transition metal oxide, a third step of subliming and removing a reactant generated by an reaction between the complexation gas and the transition metal oxide formed in the first step while the temperature of the sample is maintained at 150° C. or higher and 250° C. or lower, and a fourth step of cooling the sample.
1. An etching method for a transition metal film that is formed on a sample and contains a transition metal element, the etching method comprising:
a first step of isotropically generating a layer of transition metal oxide on a surface of the transition metal film while a temperature of the sample is maintained at 100° C. or lower;
a second step of concurrently raising the temperature of the sample to a predetermined temperature of 150° C. or higher and 250° C. or lower and supplying a complexation gas to the layer of transition metal oxide, and chemisorbing and activating materials of the complexation gas absorbed on the surface of the layer of the transition metal oxide which is obtained in the first step;
a third step of subliming and removing a reactant generated by a reaction between the complexation gas and the transition metal oxide formed in the first step while the temperature of the sample is maintained at 150° C. or higher and 250° C. or lower; and
a fourth step of cooling the sample.
2. The etching method according to claim 1 , wherein
the first to the fourth steps are repeated.
3. The etching method according to claim 1 , wherein
in the first step, the layer of the transition metal oxide is formed by irradiating the transition metal film with an oxygen radical.
4. The etching method according to claim 1 , wherein
the complexation gas contains a β-diketone.
5. The etching method according to claim 4 , wherein
the complexation gas contains the β-diketone that contains no halogen element.
6. The etching method according to claim 1 , wherein
in the second step, the temperature of the sample is raised by an electromagnetic wave.
7. The etching method according to claim 1 , wherein
the transition metal film contains Co (cobalt).
8. A plasma processing apparatus comprising:
a plasma source;
a processing chamber provided with a stage on which a sample is placed, a transition metal film that contains a transition metal element being formed on the sample;
a gas supply unit that supplies an oxidizing gas to the plasma source;
a complexation gas supplier that supplies a complexation gas to the processing chamber;
a slit plate disposed between the plasma source and the stage;
an exhaust mechanism that exhausts the processing chamber; and
a control unit, wherein
the control unit executes:
a first step of, while a temperature of the sample is maintained at 100° C. or lower, generating a layer of transition metal oxide on a surface of the transition metal film and thereafter exhausting the processing chamber by the exhaust mechanism, the layer of transition metal oxide being generated by generating plasma while the oxidizing gas is supplied from the gas supply unit to the plasma source and irradiating the sample with a neutral oxidizing gas and a neutral radical that pass through the slit plate;
a second step of concurrently raising the temperature of the sample to a predetermined temperature of 150° C. or higher and 250° C. or lower and supplying the complexation gas from the complexation gas supplier to the processing chamber, and chemisorbing and activating materials of the complexation gas absorbed on the surface of the layer of the transition metal oxide;
a third step of subliming a reactant generated by a reaction between the complexation gas and the transition metal oxide formed in the first step by maintaining the temperature of the sample at 150° C. or higher and 250° C. or lower and thereafter exhausting the processing chamber by the exhaust mechanism; and
a fourth step of cooling the sample.
9. The plasma processing apparatus according to claim 8 , wherein
the control unit repeatedly executes the first to the fourth steps.
10. The plasma processing apparatus according to claim 8 , further comprising:
a lamp unit that heats the sample, wherein
the control unit causes the temperature of the sample to be raised by an electromagnetic wave generated by the lamp unit.
11. The plasma processing apparatus according to claim 10 , further comprising:
a chiller that supplies and circulates a refrigerant in a refrigerant flow path formed inside the stage, wherein
the control unit controls the chiller to cool the sample.
12. The plasma processing apparatus according to claim 11 , further comprising:
a thermometer that measures a temperature of the stage, wherein
the control unit controls the lamp unit and the chiller based on the temperature of the stage measured by the thermometer, as well as information on temperature distribution of the sample determined based on wavelength dependency data of an spectral intensity of an electromagnetic wave absorbed by the sample, the sample being irradiated with the electromagnetic wave.
13. The plasma processing apparatus according to claim 11 , wherein
the gas supply unit supplies a cooling gas that cools the sample between the sample and the stage, and
the control unit causes the gas supply unit to supply the cooling gas in the first step and the fourth step.
14. The plasma processing apparatus according to claim 8 , wherein
the complexation gas contains a β-diketone.