Endpoint detection in the fabrication of electronic devices

• US 6,406,924 B1
• Filed: 04/05/1999
• Issued: 06/18/2002
• Est. Priority Date: 04/17/1998
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Lill, Thorsten B., Grimbergen, Michael N.
• Primary Examiner(s): Powell, William A.
• Application Number:
  US09/286,493
• Time in Patent Office: 1,170 Days
• Field of Search: 438/9, 438/14, 438/16, 438/723, 438/743, 216/56, 216/60, 156/345.MT, 356/357
• US Class Current: 438/9
• CPC Class Codes: G01B 11/0683 measurement during deposition or removal of the layer
• CPC Class Codes: H01L 21/32137 of silicon-containing layers
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

A chamber 28 comprises a radiation source 58 capable of emitting radiation having a wavelength that is substantially absorbed in a predetermined pathlength in a thickness of a layer 22 on a substrate, and a radiation detector 62 adapted to detect the radiation. The radiation is substantially absorbed in a first thickness of the layer 22, and after at least partial processing of the layer 22, is at least partially transmitted through a second thickness of the layer 22 and reflected by one or more underlayers 24 of the substrate 20.

Claims

1. A chamber for processing a substrate, the chamber comprising:

(a) a radiation source capable of emitting radiation having a wavelength that is substantially absorbed in a pathlength in a thickness of a layer on the substrate; and

(b) a radiation detector adapted to detect the radiation.

2. A chamber according to claim 1 wherein the radiation is at least partially reflected by one or more underlayers on the substrate, and the radiation detector detects a change in the intensity of the radiation.

3. A chamber according to claim 2 wherein the radiation is substantially absorbed in a first thickness of the layer, and is at least partially transmitted through a second thickness of the layer and reflected by the underlayers.

4. A chamber according to claim 1 wherein the layer has an extinction coefficient for the wavelength of the radiation that is sufficiently high for the radiation to be absorbed in a first thickness of the layer and sufficiently low for the radiation to be at least partially transmitted through a second thickness of the layer, the second thickness being smaller than the first thickness.

5. A chamber according to claim 1 wherein the radiation source is outside the chamber.

6. A chamber according to claim 1 wherein the radiation source comprises a lamp, light emitting diode or laser.

7. A chamber according to claim 1 wherein the radiation source comprises an emission from a plasma.

8. A chamber according to claim 1 wherein the radiation source provides radiation comprising nonpolarized light.

9. A chamber according to claim 1 further comprising a filter in a path of the radiation, the filter adapted to selectively pass through the radiation.

10. A chamber according to claim 1 further comprising a diffraction grating in a path of the radiation, the diffraction grating adapted to selectively pass through the radiation.

11. A chamber according to claim 1 further comprising a controller adapted to receive a signal from the radiation detector and analyze the signal to detect a characteristic feature that corresponds to an endpoint of a stage of the process.

12. A chamber according to claim 11 wherein the controller changes a process condition in the chamber upon detecting the characteristic feature, the process condition comprising one or more of gas composition, gas flow rate, an operating power level of a gas energizer, gas pressure and temperature.

13. A chamber for processing a substrate, the chamber comprising a radiation source capable of emitting radiation having a wavelength that is substantially absorbed in a pathlength of a thickness of a layer on the substrate, a radiation detector adapted to detect the radiation, and a filter in a path of the radiation, the filter adapted to selectively pass through the radiation.

14. A chamber according to claim 13 wherein the radiation is at least partially reflected by the substrate, and the radiation detector detects a change in the radiation.

15. A chamber according to claim 14 wherein the radiation is substantially absorbed in a first thickness of the layer, and is at least partially transmitted through a second thickness of the layer and reflected by one or more underlayers.

16. A chamber according to claim 13 wherein the filter comprises a radiation absorbing material.

17. A chamber according to claim 13 wherein the filter comprises a diffraction grating.

18. A chamber according to claim 13 further comprising a controller adapted to receive a signal from the radiation detector and analyze the signal to detect a characteristic feature corresponding to an endpoint of a stage of the process.

19. A chamber according to claim 18 wherein the controller changes a process condition in the chamber upon detecting the characteristic feature, the process condition comprising one or more of gas composition gas flow rate, an operating power level of a gas energizer, gas pressure and temperature.

20. A method of processing a substrate, the method comprising the steps of:

(a) placing the substrate in a process zone;

(b) maintaining process conditions in the process zone for processing a layer on the substrate, the process conditions comprising one or more of gas composition, gas flow rate, an operating power level of a gas energizer, gas pressure and temperature;

(c) providing radiation having a wavelength that is absorbed in a pathlength of a thickness of the layer being processed on the substrate; and

(d) detecting a change in the substrate reflected radiation after processing of the thickness of the layer.

21. A method according to claim 20 wherein the change in the radiation occurs from partial reflection of the radiation by one or more underlayers on the substrate.

22. A method according to claim 20 comprising the step of providing radiation that is substantially absorbed in a first thickness of the layer, and is at least partially transmitted through a second thickness of the layer and reflected by one or more underlayers.

23. A method according to claim 20 comprising the step of providing radiation having a wavelength for which an extinction coefficient of the layer is sufficiently high for the radiation to be substantially absorbed in a first thickness of the layer, and sufficiently low for the radiation to be at least partially transmitted through a second thickness of the layer, the second thickness being smaller than the first thickness.

24. A method according to claim 20 comprising the step of providing radiation comprising nonpolarized light.

25. A method according to claim 20 comprising the step of filtering the radiation to selectively pass through the radiation.

26. A method according to claim 20 further comprising the step of determining a stage of processing of the layer upon detecting the change in the radiation.

27. A method according to claim 26 further comprising the step of changing a process condition upon detecting the change in the radiation.

28. A method according to claim 27 comprising the step of changing a process condition for altering a rate of etching or deposition of the layer on the substrate.

29. A method according to claim 26 comprising the step of changing a process condition by adding a cleaning gas in a volumetric flow ratio sufficiently high to clean a surface in a chamber enclosing the substrate.

30. A method of etching a layer on a substrate, the method comprising the steps of:

(a) placing the substrate in a process zone;

(b) maintaining process conditions in the process zone for etching the layer on the substrate;

(c) providing radiation having a wavelength that is substantially absorbed in a pathlength in a thickness of the layer being etched on the substrate; and

(d) detecting a change in the substrate reflected radiation.

31. A method according to claim 30 comprising the step of providing radiation that is at least partially reflected by one or more underlayers on the substrate after partial etching of the layer.

32. A method according to claim 31 comprising the step of providing a radiation that is substantially absorbed in a first thickness of the layer, and is at least partially transmitted through a second thickness of the layer, the second thickness being smaller than the first thickness.

33. A method according to claim 31 further comprising the step of changing a process condition in the chamber upon detecting a change in the radiation, the process condition comprising one or more of gas composition, gas flow rate, an operating power level of a gas energizer, gas pressure and temperature.

34. A method according to claim 30 further comprising the step of determining a stage of etching of the layer upon detecting a change in the radiation.

35. A method according to claim 30 further comprising the step of changing a rate of etching of the layer upon detecting a change in the radiation.

36. A method of processing a substrate, the method comprising the steps of:

(a) placing the substrate into a process zone;

(b) maintaining process conditions in the process zone to process a layer on the substrate, the process conditions comprising one or more of gas composition, gas flow rate, an operating power level of gas energizer, gas pressure and temperature;

(c) providing a radiation having a wavelength that is substantially absorbed in a pathlength in a first thickness of the layer being processed on the substrate, and that is at least partially transmitted through a second thickness of the layer and reflected by one or more underlayers, the second thickness being smaller than the first thickness; and

(d) detecting a change in the radiation upon reflection of the radiation by the underlayers.

37. A method according to claim 36 wherein step (d) comprises the step of detecting the intensity of the radiation.

38. A method according to claim 37 wherein step (d) comprises the step of detecting a characteristic feature of a trace of the intensity of the radiation.

39. A method according to claim 38 comprising the step of comparing the characteristic feature to a reference feature, and when the two features are substantially similar, changing the process conditions in the chamber.

40. A method of processing a substrate, the method comprising the steps of:

(a) placing the substrate in a process zone, and maintaining process conditions in the process zone to process a layer on the substrate;

(b) providing light on the substrate, the light having a wavelength that is substantially absorbed in a pathlength in a thickness of the layer on the substrate; and

(c) detecting a change in an intensity of the light that occurs upon at least partial reflection of the light by one or more underlayers on the substrate.

41. A method according to claim 40 wherein step (c) comprises the step of detecting a characteristic feature of the intensity of the light.

42. A method according to claim 40 comprising the step of radiating unpolarized light on the substrate.

43. A method of selecting a wavelength for determining an endpoint of a process being performed on a substrate, the method comprising the step of determining a wavelength of a radiation characterized in that when the radiation having the wavelength is incident on the substrate, upon approaching the endpoint of the process, there occurs a detectable change in intensity of the reflected radiation that arises from a transition between substantial absorption of the radiation by the layer being processed on the substrate to at least partial reflection by one or more underlayers on the substrate.

44. A method according to claim 43 comprising the step of computing the radiation having the wavelength.

45. A method according to claim 43 wherein the layer comprises a dielectric, semiconductor or metal.

46. An apparatus for detecting an endpoint of a process being performed on a substrate, the apparatus comprising:

(a) a radiation source capable of emitting radiation having a wavelength that is substantially absorbed in a pathlength of a thickness of a layer on the substrate;

(b) a radiation detector adapted to detect the radiation and generate a signal; and

(c) a memory comprising a computer-readable medium having a computer-readable program embodied therein, the computer readable program including a set of instructions to detect a change in the signal to determine the endpoint of the process.

47. An apparatus according to claim 46 wherein the computer-readable program comprises a set of instructions to provide an endpoint signal to a controller to change a process condition of the process being conducted on the substrate.

48. An apparatus according to claim 46 wherein the computer-readable program comprises a set of instructions to detect a change in intensity or a rate of change of an intensity of the signal.

49. An apparatus according to claim 46 wherein the computer-readable program comprises a set of instructions to detect a characteristic feature of the signal.

50. An apparatus according to claim 49 wherein the computer-readable program comprises a set of instructions to model a trace of the signal for an operator to select a suitable characteristic feature.

51. A substrate processing apparatus comprising:

(a) a chamber comprising a support adapted to support a substrate in the chamber, a gas delivery system adapted to introduce gas into the chamber, a plasma generator adapted to energize the gas in the chamber, an exhaust comprising a throttle valve adapted to control the pressure of gas in the chamber, and a controller adapted to control one or more of the gas delivery system, plasma generator or throttle valve, to change a process condition in the chamber in relation to an endpoint signal; and

(b) an endpoint detection system comprising a radiation source capable of emitting radiation having a wavelength that is substantially absorbed in a pathlength in a thickness of the layer, a radiation detector adapted to detect the radiation and generate a signal, and a memory coupled to the controller of the chamber, the memory comprising a computer-readable medium having a computer-readable program embodied therein for directing operation of the substrate processing apparatus, the computer-readable program including a set of instructions to detect a change in the signal to determine an endpoint of the process and provide an endpoint signal to the controller.

52. A substrate processing apparatus according to claim 51 wherein the computer-readable program comprises a set of instructions to detect a change in intensity or a rate of change of an intensity in the signal.

53. A substrate processing apparatus according to claim 52 wherein the computer-readable program comprises a set of instructions to detect a characteristic feature of the signal.

54. A substrate processing apparatus according to claim 51 wherein the computer-readable program comprises a set of instructions to model the signal for an operator to select a suitable characteristic feature.

55. A method of etching a layer on a substrate in a chamber, the method comprising the steps of:

(a) placing the substrate in the chamber;

(b) providing in the chamber, a process gas comprising etchant gas and cleaning gas, and maintaining process conditions to etch the layer on the substrate and simultaneously clean a surface of the chamber; and

(c) prior to etching through the layer, changing the composition of the process gas to remove the cleaning gas.

56. A method according to claim 55 wherein the etchant gas comprises one or more of Cl₂, HBr, N₂, O₂, or He—

O₂.

57. A method according to claim 55 wherein the cleaning gas comprises one or more of NF₃, CF₄, or SF₆.

58. A method according to claim 55 wherein the volumetric flow ratio of cleaning gas to etchant gas is from about 1:

20 to about 1;

1.

59. A substrate etching method comprising:

(a) placing a substrate in a process zone, the substrate comprising a layer;

(b) maintaining process conditions in the process zone for etching the layer on the substrate, the process conditions comprising at least one of gas composition, gas flow rate, an operating power level of a gas energizer, gas pressure and temperature;

(c) providing radiation that is incident on the substrate, the radiation having a wavelength that is substantially absorbed in a pathlength in the layer on the substrate; and

(d) determining an endpoint of the etching process by detecting a change in the intensity of the radiation reflected from the substrate that arises from the onset of an interference fringe.

60. A method according to claim 59 wherein the onset of the interference fringe occurs after an intensity trace of the reflected radiation that is substantially absent periodic maxima and minima.

61. A method according to claim 59 wherein the onset of the interference fringe occurs after an intensity trace of the reflected radiation comprising a substantially constant intensity level.

62. A method according to claim 59 wherein the change in intensity of the reflected radiation arises from the transition between (i) substantial absorption of the incident radiation by the layer being etched on the substrate, to (ii) at least partial reflection of the incident radiation by one or more underlayers on the substrate and transmission of the reflected radiation through the remaining portion of the layer being etched.

63. A method according to claim 59 wherein the layer comprises a thickness of less than about 50 angstroms.

64. A method according to claim 59 wherein the layer comprises a gate oxide or polysilicon layer.

65. A substrate etching method comprising:

(a) placing a substrate in a process zone, the substrate comprising a layer composed of gate oxide or polysilicon, the layer comprising a thickness of less than about 50 angstroms;

(b) maintaining process conditions in the process zone for etching the layer on the substrate, the process conditions comprising at least one of gas composition, gas flow rate, an operating power level of a gas energizer, gas pressure and temperature;

(c) providing radiation that is incident on the substrate, the radiation having a wavelength that is substantially absorbed in a pathlength in the layer on the substrate; and

(d) determining an endpoint of the etching process by detecting a change in the intensity of the radiation reflected from the substrate that arises from an onset of an interference fringe that occurs after an intensity trace of the reflected radiation that is substantially absent periodic maxima and minima.

66. A method according to claim 65 wherein the onset of the interference fringe occurs after an intensity trace comprising a substantially constant intensity level.

67. A method according to claim 65 wherein the change in intensity of the reflected radiation arises from the transition between (i) substantial absorption of the incident radiation by the layer being etched on the substrate, to (ii) at least partial reflection of the incident radiation by one or more underlayers on the substrate and transmission of the reflected radiation through the remaining portion of the layer being etched.

68. A substrate etching method comprising:

(a) placing a substrate in a process zone, the substrate comprising a layer;

(b) maintaining process conditions in the process zone for etching the layer on the substrate, the process conditions comprising at least one of gas composition, gas flow rate, an operating power level of a gas energizer, gas pressure and temperature;

(c) providing radiation that is incident on the substrate; and

(d) determining an endpoint of the etching process by detecting a change in the intensity of the radiation reflected from the substrate that arises from an onset of an interference fringe after an intensity trace of the reflected radiation that is substantially absent periodic maxima and minima.

69. A method according to claim 68 wherein the radiation has a wavelength that is capable of being substantially absorbed in a pathlength in the layer on the substrate.

70. A method according to claim 69 wherein the change in intensity of the reflected radiation arises from the transition between (i) substantial absorption of the incident radiation by the layer being etched on the substrate, to (ii) at least partial reflection of the incident radiation by one or more underlayers on the substrate and transmission of the reflected radiation through the remaining portion of the layer being etched.

71. A method according to claim 68 wherein the intensity trace comprises a substantially constant intensity level.

72. A method according to claim 68 wherein the layer comprises a thickness of less than about 50 angstroms.

73. A method according to claim 68 wherein the layer comprises a gate oxide or polysilicon layer.

74. A substrate etching method comprising:

(a) placing a substrate in a process zone, the substrate comprising a layer;

(b) maintaining process conditions in the process zone for etching the layer on the substrate, the process conditions comprising at least one of gas composition, gas flow rate, an operating power level of a gas energizer, gas pressure and temperature;

(c) providing radiation that is incident on the substrate; and

(d) determining an endpoint of the etching process by detecting a change in the intensity of radiation reflected from the substrate that arises from the transition between substantial absorption of the incident radiation by the layer being etched on the substrate to at least partial reflection of the incident radiation by one or more underlayers on the substrate and transmission of the reflected radiation through a remaining portion of the layer being etched.

75. A method according to claim 74 wherein the change in the intensity of the reflected radiation represents an onset of an interference fringe.

76. A method according to claim 75 wherein the onset of the interference fringe occurs after an intensity trace of the reflected radiation that is substantially absent periodic maxima and minima.

77. A method according to claim 75 wherein the interference fringe occurs after an intensity trace comprising a substantially constant intensity level.

78. A method according to claim 74 wherein the layer comprises a thickness of less than about 50 angstroms.

79. A method according to claim 74 wherein the layer comprises a gate oxide or polysilicon layer.

80. A substrate processing apparatus comprising:

(a) a chamber comprising a support to support a substrate, a gas delivery system to introduce gas into the chamber, a plasma generator to energize the gas, and an exhaust comprising a throttle valve adapted to control the pressure of the gas in the chamber;

(b) a radiation source capable of emitting radiation having a wavelength that is substantially absorbed in a pathlength of a layer on the substrate;

(c) a radiation detector adapted to detect radiation reflected from the substrate and generate a signal; and

(d) a controller adapted to (i) control one or more of the gas delivery system, plasma generator, and throttle valve, of the chamber, and (ii) receive the signal from the radiation detector and determine an endpoint of the etching process by detecting a change in the intensity of the signal that arises from the onset of an interference fringe in the reflected radiation.

81. An apparatus according to claim 80 wherein the onset of the interference fringe occurs after an intensity trace that is substantially absent periodic maxima and minima.

82. An apparatus according to claim 80 wherein the onset of the interference fringe occurs after an intensity trace that is at a substantially constant intensity level.

83. An apparatus according to claim 80 wherein the change in intensity of the signal arises from the transition between (i) substantial absorption of the incident radiation by the layer being etched on the substrate, to (ii) at least partial reflection of the incident radiation by one or more underlayers on the substrate and transmission of the reflected radiation through the remaining portion of the layer being etched.

84. An apparatus according to claim 80 wherein the layer on the substrate comprises a thickness of less than about 50 angstroms.

85. An apparatus according to claim 80 wherein the layer on the substrate comprises a gate oxide or polysilicon layer.

86. A substrate processing apparatus comprising:

(a) a chamber comprising a support to support a substrate, a gas delivery system to introduce gas into the chamber, a plasma generator to energize the gas, and an exhaust comprising a throttle valve adapted to control the pressure of the gas in the chamber;

(b) a radiation source capable of emitting radiation having a wavelength that is substantially absorbed in a pathlength of a layer on the substrate;

(c) a radiation detector adapted to detect radiation reflected from the substrate and generate a signal; and

(d) a controller adapted to (i) control one or more of the gas delivery system, plasma generator, and throttle valve, of the chamber, and (ii) receive the signal from the radiation detector and determine an endpoint of the etching process by detecting a change in the intensity of the radiation reflected from the substrate that arises from an onset of an interference fringe after an intensity trace of the reflected radiation that is substantially absent periodic maxima and minima.

87. An apparatus according to claim 86 wherein the intensity trace comprises a substantially constant intensity level.

88. An apparatus according to claim 86 wherein the change in intensity of the signal arises from the transition between (i) substantial absorption of the incident radiation by the layer being etched on the substrate, to (ii) at least partial reflection of the incident radiation by one or more underlayers on the substrate and transmission of the reflected radiation through the remaining portion of the layer being etched.

89. An apparatus according to claim 86 wherein the layer on the substrate comprises a thickness of less than about 50 angstroms.

90. An apparatus according to claim 86 wherein the layer on the substrate comprises a gate oxide or polysilicon layer.

91. A substrate processing apparatus comprising:

(a) a chamber comprising a support to support a substrate, a gas delivery system to introduce gas into the chamber, a plasma generator to energize the gas, and an exhaust comprising a throttle valve adapted to control the pressure of the gas in the chamber;

(b) a radiation source capable of emitting radiation that is incident on the substrate;

(c) a radiation detector adapted to detect radiation that is reflected from the substrate and generate a signal; and

(d) a controller adapted to (i) control one or more of the gas delivery system, plasma generator, and throttle valve, of the chamber, and (ii) receive the signal from the radiation detector and determine an endpoint of the etching process by detecting a change in the intensity of the radiation reflected from the substrate that arises from an onset of an interference fringe after an intensity trace of the reflected radiation that is substantially absent periodic maxima and minima.

92. An apparatus according to claim 91 wherein the radiation source emits radiation having a wavelength that is capable of being substantially absorbed in a pathlength in the layer on the substrate.

93. An apparatus according to claim 91 wherein the intensity trace comprises a substantially constant intensity level.

94. An apparatus according to claim 91 wherein the change in intensity of the signal arises from the transition between (i) substantial absorption of the incident radiation by the layer being etched on the substrate, to (ii) at least partial reflection of the incident radiation by one or more underlayers on the substrate and transmission of the reflected radiation through the remaining portion of the layer being etched.

95. An apparatus according to claim 91 wherein the layer on the substrate comprises a thickness of less than about 50 angstroms.

96. An apparatus according to claim 91 wherein the layer on the substrate comprises a gate oxide or polysilicon layer.