Thin Film Forming Method and Thin Film Forming Apparatus

• US 20080050538A1
• Filed: 07/19/2005
• Published: 02/28/2008
• Est. Priority Date: 08/06/2004
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Hirata, Toshiharu
• Granted Patent: US 7,972,649 B2
• Time in Patent Office: Days
• US Class Current: 427/585
• CPC Class Codes: C23C 16/4412 Details relating to the exhausts, e.g. pumps, filters, scrubbers, particle traps
• CPC Class Codes: C23C 16/45527 characterized by the ALD cycle, e.g. different flows or temperatures during half-reactions, unusual pulsing sequence, use of precursor mixtures or auxiliary reactants or activations
• CPC Class Codes: C23C 16/45542 Plasma being used non-continuously during the ALD reactions
• CPC Class Codes: C23C 16/45557 Pulsed pressure or control pressure
• CPC Class Codes: H01L 21/0228 deposition by cyclic CVD, e.g. ALD, ALE, pulsed CVD
• CPC Class Codes: H01L 21/28562 Selective deposition
• CPC Class Codes: H01L 21/3141 Deposition using atomic layer deposition techniques [ALD]

Abstract

A thin film formation method is used for forming a thin film by providing a conductance valve on an exhaust path connecting a depressurizable processing chamber and a vacuum pump, arranging a processing object substrate inside the processing chamber, performing once or plural times a cycle including a first step of supplying a first reactive gas and a second step of supplying a second reactive gas into the processing chamber during a film formation processing period to cause a chemical reaction between the first reactive gas and the second reactive gas, and using the chemical reaction to form the thin film on the substrate. The thin film formation method includes a first process of supplying into the processing chamber a predetermined gas by a specified flow while exhausting the inside of the processing chamber, and determining a reference value that is equal to a valve opening level of the conductance valve causing pressure inside the processing chamber to substantially match a specified value, the first process being performed during a preparation period before the film formation processing period starts; and a second process of maintaining the valve opening level of the conductance valve at the reference value at least during the first step and the second step of the cycle performed during the film formation processing period.

Claims

1. A thin film formation method for forming a thin film by providing a conductance valve on an exhaust path connecting a depressurizable processing chamber and a vacuum pump, arranging a processing object substrate inside the processing chamber, performing once or plural times a cycle including a first step of supplying a first reactive gas and a second step of supplying a second reactive gas into the processing chamber during a film formation processing period to cause a chemical reaction between the first reactive gas and the second reactive gas, and using the chemical reaction to form the thin film on the substrate, the thin film formation method comprising:

a first process of supplying into the processing chamber a predetermined gas by a specified flow while exhausting the inside of the processing chamber, and determining a reference value that is equal to a valve opening level of the conductance valve causing pressure inside the processing chamber to substantially match a specified value, the first process being performed during a preparation period before the film formation processing period starts; and

a second process of maintaining the valve opening level of the conductance valve at the reference value at least during the first step and the second step of the cycle performed during the film formation processing period.

2. The thin film formation method according to claim 1 wherein a layer of one atom or one molecule is deposited on the substrate due to the chemical reaction between the first reactive gas and the second reactive gas in one cycle, and

the thin film formed on the substrate has a thickness corresponding to a number of times the cycle is performed.

3. The thin film formation method according to claim 1, wherein the preparation period is within a time period in which the substrate is not present inside the processing chamber.

4. The thin film formation method according to claim 1, wherein the preparation period is within a time period after the substrate has been arranged inside the processing chamber.

5. The thin film formation method according to claim 1, wherein during the preparation period, at least one of the first reactive gas and the second reactive gas is supplied into the processing chamber as pressure controlling gas by a gas flow equivalent to a gas flow in the film formation processing period.

6. The thin film formation method according to claim 5, wherein the first reactive gas is a source gas including as a chemical compound crude material of the thin film, and

the second reactive gas is a reducing gas that reduces the chemical compound.

7. The thin film formation method according to claim 6, wherein the second reactive gas is plasma-excited in the processing chamber to generate a radical and/or an ion.

8. The thin film formation method according to claim 1, wherein the cycle further includes a third step of discharging from the processing chamber the first reactive gas that is excessive, wherein the third step is performed immediately after the first step.

9. The thin film formation method according to claim 8, wherein a purge gas including inert gas is supplied into the processing chamber in the third step.

10. The thin film formation method according to claim 8, wherein the valve opening level of the conductance valve is maintained at the reference value also during the third step.

11. The thin film formation method according to claim 8, wherein the valve opening level of the conductance valve is changed to a value near a maximum value during the third step.

12. The thin film formation method according to claim 1, wherein the cycle further includes a fourth step of discharging from the processing chamber the second reactive gas that is excessive, wherein the fourth step is performed immediately after the second step.

13. The thin film formation method according to claim 12, wherein a purge gas including inert gas is supplied into the processing chamber in the fourth step.

14. The thin film formation method according to claim 12, wherein the valve opening level of the conductance valve is maintained at the reference value also during the fourth step.

15. The thin film formation method according to claim 12, wherein the valve opening level of the conductance valve is changed to a value near a maximum value during the fourth step.

16. The thin film formation method according to claim 1, wherein the first process includes

a third process of variably controlling the valve opening level of the conductance valve by a pressure feedback method such that a detected value of the pressure inside the processing chamber matches the specified value, and

a fourth process of measuring the valve opening level of the conductance valve during the third process.

17. The thin film formation method according to claim 16, wherein the fourth process is performed immediately before the preparation period ends.

18. The thin film formation method according to claim 16, wherein the fourth process includes a fifth process of acquiring instantaneous values of the valve opening level of the conductance valve at fixed time intervals as sample values, and obtaining an average of n (n being a whole number) of the sample values.

19. The thin film formation method according to claim 18, wherein the fifth process includes

a sixth process of adding, at the fixed time intervals, a new sample value to the n (n being a whole number) sample values consecutively acquired and simultaneously excluding an oldest sample value among the n+1 sample values, and

a seventh process of obtaining an arithmetic average of the n consecutive sample values acquired after replacing the oldest sample value with the new sample value in the sixth process.

20. The thin film formation method according to claim 1, wherein the second process includes

an eighth process of detecting a value of the valve opening level of the conductance valve,

a ninth process of obtaining a comparative error by comparing the detected value of the valve opening level and the reference value, and

a tenth process of variably controlling the valve opening level of the conductance valve according to the comparative error.

21. The thin film formation method according to claim 4, wherein the substrate is heated to a specified temperature within the preparation period, and the specified temperature of the substrate is maintained throughout the film formation processing period.

22. The thin film formation method according to claim 1, wherein

the first process includes

supplying a first pressure controlling gas including at least the first reactive gas into the processing chamber, and determining a first reference value that is equal to the valve opening level of the conductance valve causing the pressure inside the processing chamber to substantially match a first specified value, and

supplying a second pressure controlling gas including at least the second reactive gas into the processing chamber, and determining a second reference value that is equal to the valve opening level of the conductance valve causing the pressure inside the processing chamber to substantially match a second specified value, and

the second process includes

maintaining the valve opening level of the conductance valve at the first reference value during the first step, and

maintaining the valve opening level of the conductance valve at the second reference value during the second step.

23. A thin film formation apparatus for forming a thin film by providing a conductance valve on an exhaust path connecting a depressurizable processing chamber and a vacuum pump, arranging a processing object substrate inside the processing chamber, performing once or plural times a cycle including a step of supplying a first reactive gas and a step of supplying a second reactive gas into the processing chamber during a film formation processing period to cause a chemical reaction between the first reactive gas and the second reactive gas, and using the chemical reaction to form the thin film on the substrates the thin film formation apparatus comprising:

an automatic pressure control unit configured to variably control a valve opening level of the conductance valve by a pressure feedback method such that pressure inside the processing chamber matches a specified value;

a valve opening level identifying unit configured to determine a reference value that is equal to the valve opening level of the conductance valve causing the pressure inside the processing chamber to substantially match the specified value; and

a valve opening level holding unit configured to maintain the valve opening level of the conductance valve at the reference value.

24. The thin film formation apparatus according to claim 23, wherein the valve opening level identifying unit includes

a sampling unit configured to acquire sampling values by detecting, at fixed time intervals, the valve opening level of the conductance valve while the automatic pressure control unit is variably controlling the valve opening level of the conductance valve,

a FIFO buffer memory configured to receive the sample values from the sampling unit at the fixed time intervals and hold n (n being a whole number) of the sample values at once by a first in, first out method,

a calculating unit configured to obtain, at the fixed time intervals, an arithmetic average of the n sample values held in the FIFO buffer memory, and

a reference value determining unit configured to latch, at a predetermined timing, the arithmetic average obtained by the calculating unit at the fixed time intervals, and specifying the latched arithmetic average as the reference value.

25. The thin film formation apparatus according to claim 23, wherein the valve opening level holding unit includes

a valve driving unit configured to change the valve opening level of the conductance valve,

a valve opening level detecting unit configured to detect an instantaneous value of the valve opening level of the conductance valve,

a comparing unit configured to generate a comparative error by comparing the instantaneous value of the valve opening level with the reference value, and

a valve control unit configured to control the valve driving unit according to the comparative error.

26. The thin film formation apparatus according to claim 23, further comprising:

a plasma generating unit configured to cause a state of at least one of the first reactive gas and the second reactive gas to be a plasma state in the processing chamber.

27. The thin film formation apparatus according to claim 23, wherein

a layer of one atom or one molecule is deposited on the substrate due to the chemical reaction between the first reactive gas and the second reactive gas in one cycle, and

the thin film formed on the substrate has a thickness corresponding to a number of times the cycle is performed.