Detection system for nanometer scale topographic measurements of reflective surfaces

• US 20080225275A1
• Filed: 03/03/2008
• Published: 09/18/2008
• Est. Priority Date: 11/18/1998
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation
• Original Assignee: KLA-Tencor Corporation
• Inventors: Nielsen, Henrik K., Nokes, Mark, Kuhlmann, Lionel
• Granted Patent: US 8,384,903 B2
• Time in Patent Office: Days
• US Class Current: 356/73
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

A linear position array detector system is provided which imparts light energy to a surface of a specimen, such as a semiconductor wafer, receives light energy from the specimen surface and monitors deviation of the retro or reflected beam from that expected to map the contours on the specimen surface. The retro beam will, with ideal optical alignment, return along the same path as the incident beam if and only if the surface is normal to the beam. The system has a measurement device or sensor within the path of the retro or reflected beam to measure deviation of the retro beam from expected. The sensor is preferably a multiple element array of detector-diodes aligned in a linear fashion. A unique weighting and summing scheme is provided which increases the mechanical dynamic range while preserving sensitivity. The system further includes a bright field Nomarski Differential Interference Contrast sensor used to split the beam into two beams and for scanning in an orientation orthogonal to the orientation of the optical lever created by the system.

Claims

1-60. -60. (canceled)

61. A detector array configured for use with a light source, comprising:

a plurality of elements configured to detect a reflected beam of light energy provided by the light source and reflected from a component, said reflected beam having a beam diameter; and

a plurality of electrical connections affixed to said plurality of elements, said plurality of electrical connections connectable to at least one inspection device;

wherein said elements have width less than approximately one third the beam diameter.

62. The detector array of claim 61, further comprising:

a first plurality of weighting elements, each weighting element having a first predetermined weight associated therewith and electrically connected to a preamplifier;

a second plurality of weighting elements, said second plurality of weighting elements having a second predetermined weight associated therewith and electrically connected to said preamplifier, wherein said first predetermined weight differs from said second predetermined weight; and

a summing amplifier for receiving signals from selected ones of said first plurality of elements and said second plurality of elements.

63. The detector array of claim 62, wherein each preamplifier is electrically connected to two weighting elements.

64. The detector array of claim 61, wherein movement of said reflected beam is sensed by said detector array, and said movement alters electrical signals transmitted from selected elements of said detector array.

65. The detector array of claim 64, wherein movement of said beam causes altered transmission of signals to a weighting and summing arrangement.

66. The method of claim 61, further comprising:

a plurality of preamplifiers, wherein each element has a preamplifier associated therewith.

67. A method for inspecting a specimen, comprising:

providing light energy to said specimen, thereby creating a retro beam reflected from said specimen;

providing said retro beam to a multi-element sensing device comprising a plurality of linearly oriented sensing elements such that said retro beam is received by at least three of said sensing elements; and

altering a characteristic of said electrical output according to a weighting corresponding to a distance of said plurality of sensing elements from a predetermined point on said multi-element sensing device.

68. The method of claim 67, wherein said multi-element sensing device is employed to assess movement of the retro beam corresponding to anomalies on said specimen.

69. The method of claim 67, wherein providing said retro beam comprises diverting the retro beam via a beamsplitter.

70. The method of claim 67, wherein said sensing device comprises:

a plurality of detector elements having exposed ends and predetermined spacing between said elements;

a plurality of electrical connections affixed to said exposed ends of said detector elements; and

a plurality of preamplifiers, wherein each element has a preamplifier associated therewith.

71. The method of claim 67, wherein said light energy is provided to said specimen in a substantially normal orientation.

72. The method of claim 67, wherein said retro beam creating comprises passing light energy through an optical arrangement to the specimen and the method further comprises the retro beam passing back through the optical arrangement.

73. The method of claim 72, wherein the optical arrangement comprises a plurality of lenses.

74. A method for inspecting the surface of a specimen, comprising:

providing at least three linearly arranged elements having electrical connections to an inspection device and predetermined spacing therebetween; and

imparting a light beam onto said linearly arranged elements, wherein said light beam is expected to move in a predetermined direction substantially collinear with said linearly arranged elements;

wherein said beam spans at least three of said linearly arranged elements.

75. The method of claim 74, further comprising:

providing light energy to a specimen via an optical element arrangement, thereby creating a retro beam reflected from said specimen; and

passing said retro beam back through said optical element arrangement, thereby creating said light beam;

wherein said providing and passing occur prior to said light beam imparting.

76. The method of claim 74, wherein said optical element arrangement comprises:

a birefringent prism; and

a lensing arrangement, said lensing arrangement comprising a plurality of optical lenses.

77. The method of claim 76, wherein said optical element arrangement further comprises:

an optical isolator;

a half wave plate; and

at least one mirror.

78. The method of claim 75, wherein said optical element arrangement comprises a bright field scanning Nomarski Differential Interference Contrast sensor.

79. The method of claim 78, wherein said bright field scanning Nomarski Differential Interference Contrast sensor splits said beam into two beams, and wherein said providing comprises scanning said two beams of light over said specimen at a substantially orthogonal angle to an optical lever.

80. The method of claim 74, wherein said linearly arranged elements further comprise:

a plurality of electrical connections affixed to said exposed ends of said elements; and

a plurality of preamplifiers, wherein each linear diode element has a preamplifier associated therewith.