A PHOTOELECTRON SPECTROSCOPYAPPARATUS AND METHOD OF

USE

BACKGROUND OF THE INVENTION

1). Field of the Invention

[0001] The present invention relates to a method, apparatus, and system for processing

semiconductor substrates, particularly to a metrology tool for use in processing

semiconductor substrates.

2). Discussion of Related Art

[0002] Integrated circuits are formed on semiconductor substrates such as wafers. The

formation of the integrated circuits may include numerous processing steps such as

deposition of various layers, etching some of the layers, and multiple bakes. The integrated

circuits are then separated into individual microelectronic dice, which are packaged and

attached to circuit boards.

[0003] During the various processing steps involved in the creation of the integrated

circuits, various layers of different materials, such as conductors, dielectrics, and

semiconductor, are formed on the surface of the wafer where the integrated circuits are

being formed. The manufacturers of the integrated circuits often test the composition of

the various layers to ensure that the proper materials are being deposited on the substrates.

[0004] The machines used to test the composition of the layers are often referred to as

^et^logys^dliiiVTBd-ilnέirJblbgy tools emit electromagnetic radiation, such as x-rays from

an x-ray source, which are directed to a particular region of a substrate that is being tested.

The metrology tools make use of analysis techniques, such as X-ray Photoelectron

Spectroscopy (XPS), Total Reflection X-ray Fluorescence (TXRF), and ellipsometry, to

measure particular characteristics of the substrate. If, for example, XPS is used,

photoelectrons, or electrons, are emitted from the substrate and captured by a metrological

analyzer, such as an electron spectrometer or hemispherical analyzer. The analyzer and

associated processing algorithms determine the composition of the region of the substrate

by analyzing the kinetic energy, or speed, of the photoelectrons.

[0005] In order to properly position the substrates, specifically the pads on the substrates,

relative to the electromagnetic radiation source, vision systems may be used which utilize

pattern recognition software.

[0006] However, typically the vision systems are only able to view the pads at an angle,

so the image is not ideal. Additionally, the systems are not able to view a particular pad

while it is being tested. Furthermore, the vision systems typically include multiple

actuators and other moving parts, which create contaminates within the tool.

[0007] Often, magnetic field generators, or magnetic lenses, are used to guide the

photoelectrons from the substrate into the analyzers. However, the metrology tools

usually include both a robot to transport the substrates into the tool, and a separate stage to

hold the substrates under the analyzer and above the magnetic lens. The separate stage

occupies a considerable amount of space within the tool, and the magnetic lenses must be

located below the stage, which detrimentally affects the effectiveness of the magnetic lens.

[0008] ,4tpth€ _! ?TOQr^.%e,;iC(pfi^ents of the metrology tools, including the magnetic lens, are

typically held within vacuum chambers. If the magnetic lens requires any sort of

maintenance, the vacuum must be broken, which increases the likelihood that the interior

of the tool will be contaminated.

[0009] One common example of an electromagnetic radiation source that is used in the

metrology tools is the combination of an electron gun, anode, and a monochromator. The

electron gun fires electrons onto a relatively small target portion of the anode, and x-rays

are emitted from the anode onto the monochromator, which deflects and focuses the x-rays

onto the substrate.

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[0011] Embodiments of the present invention provide a substrate processing system. The

system may include a chamber enclosed by a chamber wall, a substrate or specimen

support positioned within the chamber to support a substrate or specimen, an

electromagnetic radiation source to emit electromagnetic radiation onto the substrate on

the substrate support, the electromagnetic radiation causing photoelectrons to be emitted

from the substrate surface, an analyzer to capture the photoelectrons emitted from the

material on the semiconductor substrate, and a magnetic field generator to generate a

magnetic field within the chamber and guide the photoelectrons from the substrate to the

analyzer. In an embodiment of the present invention, the substrate or specimen support,

electromagnetic radiation source, analyzer and magnetic field generator are each connected

to the chamber wall.

[0012] Embodiment of the present invention also provide a substrate processing system

which may include a chamber wall enclosing a vacuum chamber, a substrate or specimen

support positioned within the vacuum chamber to support a substrate, an electromagnetic

radiation source to emit electromagnetic radiation onto the substrate on the substrate

support, the electromagnetic radiation causing photoelectrons to be emitted from the

substrate, an analyzer to capture the photoelectrons emitted from the substrate, and a

magnetic field generator to generate a magnetic field within the vacuum chamber and

guide the photoelectrons from the semiconductor substrate to the analyzer, the magnetic

field generator being positioned outside of the vacuum chamber.

„1001311 _/ TfeiipN!!EMtl<SPSl.Wip>tlbvides a semiconductor substrate processing apparatus which

may include a chamber wall enclosing a chamber having a loading portion and a testing

portion, a robotic stage having a robotic arm connected to the chamber wall and a substrate

or specimen support attached to the robotic arm, the robotic arm being capable of moving

the substrate support between the loading and test portions of the chamber, an

electromagnetic radiation source to emit electromagnetic radiation onto a substrate on the

substrate support when the substrate support is in the testing portion of the chamber, the

electromagnetic radiation causing photoelectrons to be emitted from the substrate, an

analyzer to capture the photoelectrons emitted from the substrate, and a magnetic field

generator to generate a magnetic field within the chamber and guide the photoelectrons

from the substrate to the analyzer, the magnetic field generator being positioned beneath

the substrate support when the substrate support is in the testing portion of the chamber.

[0014] Embodiments of the present invention further provide a substrate processing

apparatus which may include a chamber wall enclosing a chamber, a substrate support

positioned within the chamber to support a semiconductor substrate, an electromagnetic

radiation source to emit electromagnetic radiation onto a portion of the substrate on the

substrate support, the electromagnetic radiation causing photoelectrons to be emitted from

the portion of the substrate, an analyzer to capture the photoelectrons emitted from the

material on the portion of the substrate, and a camera subsystem connected to the chamber

wall to collect visible light that is reflected off the portion of the substrate and capture an

image of the portion of the semiconductor substrate.

,[QQ15l /EiA<sdtmenBMt$hl! present invention further provide a substrate processing

apparatus which may include a chamber wall enclosing a chamber, a substrate support

positioned within the chamber to support a substrate, an electromagnetic radiation source

connected to emit electromagnetic radiation onto a portion of the substrate on the substrate

support, the electromagnetic radiation causing photoelectrons to be emitted from a

material on the portion of the substrate, an analyzer connected to the chamber wall to

capture the photoelectrons emitted from the material on the portion of the substrate, a

magnetic field generator to generate a magnetic field within the chamber and guide the

photoelectrons from the substrate to the analyzer, and a camera subsystem to collect visible

light that is reflected off the portion of the substrate and capture an image of the portion of

the semiconductor substrate.

[0016] Embodiments of the present invention further provide a substrate processing

apparatus which may include a substrate support to support a substrate having an upper

surface, and a camera subsystem to collect visible light that is reflected off a portion of the

substrate and capture an image of the portion of the substrate, the visible light propagating

from the portion of the substrate in a direction that is substantially perpendicular to the

upper surface of the substrate surface.

[0017] Embodiments of the present invention further provide a substrate processing

apparatus which may include a chamber wall enclosing a chamber, a substrate support

positioned within the chamber to support a substrate, an electromagnetic radiation source

connected to emit a beam of electromagnetic radiation onto a portion of the substrate, the

_ffi §l,pc^oππiiasjpι,^^^i3ti^tl ^!l '<!Slulang photoelectrons to be emitted from the portion of the

semiconductor substrate and an analyzer connected to capture the photoelectrons emitted

from the material on the substrate.

[0018] In an embodiment of the present invention the electromagnetic radiation source

includes an electron source for providing an electron beam for irradiating an anode with

electrons to produce electromagnetic radiation, such as X-rays, and a monochromator to

focus the emitted electromagnetic radiation onto the substrate or specimen. In

embodiments of the present invention, the electron source includes shaping means, such as

an octopole or aperture shutters to shape the electron beam into a desired shape or profile.

The electron beam can be shaped into a desired profile, such as but not limited to a circle,

an elongated oval, a square, and a rectangle. In an embodiment of the present invention,

an electron beam is shaped into an elongated oval or rectangle having a length is 1-3 times

larger than its width. Additionally, in an embodiment of the present invention, a large area

monochromator with a large solid angle is utilized to increase the collection efficiency of

the monochromator. A large area monochromator with a large solid angle enables the e-

beam shape to be transferred into an X-ray profile pattern which is highly correlated to the

e-beam shape on the anode.

[0019] The invention is described by way of example with reference to the accompanying

drawings, wherein:

[0020] Figure IA is top plan schematic view of a semiconductor substrate processing

apparatus including a metrology chamber;

[0021] Figures IB, 1C, and ID are cross-sectional side schematic views of the metrology

chamber shown in Figure 1;

[0022] Figure 2 is a cross-sectional side view of an electron source within the metrology

chamber illustrated in Figure 1;

[0023] Figure 3 is a cross-sectional view on 3-3 in Figure 2 of a beam shaper within the

electron source illustrated in Figure 2;

[0024] Figure 4 is a perspective view of an anode within the metrology chamber

illustrated in Figure 1;

[0025] Figure 5 is a perspective view of a focusing objective within the metrology

chamber illustrated in Figure 1;

[0026] Figure 6 is a top plan schematic view of the semiconductor substrate processing

apparatus similar to Figure 1;

[0027] Figure 7 is a top plan view of a semiconductor substrate;

[0028] Figure 8A is a cross-sectional side schematic view of the metrology chamber

similar to Figure 1C;

[0029] Figure 8B is a cross-sectional view of the beam shaper similar to Figure 3;

feQQβO|" ,Fiigiiϊ|-f jgg js ajjpf r^§cjt|ve view of the anode similar to Figure 4;

[0031] Figure 8D is a top plan view of the semiconductor substrate similar to Figure 7;

[0032] Figure 9A is a top plan view of a semiconductor substrate within the metrology

chamber illustrated in Figure 1 showing movement thereof;

[0033] Figure 9B is a cross-sectional view of the beam shaper similar to Figures 3 and 8B;

[0034] Figure 9C is a perspective view of the anode similar to Figures 4 and 8C;

[0035] Figure 9D is a top plan view of the semiconductor substrate similar to Figures 7

and 8D; and

[0036] Figures 1OA - 1OC are cross-sectional side schematic views of the metrology

chamber illustrated in Figure 1.

[0037] In the following description, various aspects of the present invention will be

described, and various details set forth in order to provide a thorough understanding of the

present invention. However, it will be apparent to those skilled in the art that the present

invention may be practiced with only some or all of the aspects of the present invention,

and the present invention may be practiced without the specific details. In other instances,

well-known features are omitted or simplified in order not to obscure the present

invention.

[0038] It should be understood the Figures IA through 1OC are merely illustrative and

may not be drawn to scale.

[0039] An embodiment of the present invention provides what is known in the art as a

"metrology tool." The metrology tool may include load-lock chamber and a metrology

chamber, enclosing a vacuum chamber, with a loading portion and a testing portion. A

robotic stage may be located within loading portion of the metrology chamber to transport

semiconductor substrates from the load-lock chamber to the testing portion of the

metrology chamber. The metrology tool may also include a magnetic lens positioned

below the testing portion of the metrology chamber and outside the vacuum chamber.

[0040] The metrology tool may also include an electromagnetic radiation source capable

of emitting a beam of electromagnetic radiation onto features on the substrates in particular

shapes and sizes. Additionally, the metrology tool may include a viewing, or camera,

subsystem capable of viewing the features on the substrates at an angle normal (i.e.,

electromagnetic radiation is being directed onto

the features.

[0041] The metrology tool may also include an analyzer to capture and analyze

photoelectrons emitted from the features to determine the composition of the features.

[0042] Figure IA illustrates a substrate processing system, or a metrology tool 20,

according to an embodiment of the present invention. The metrology tool 20 may include a

frame 22, wafer cassettes 24, a transport subsystem 26, a load-lock chamber 28, a metrology

chamber 30 enclosed by a chamber wall 38, and a computer control console 32. The frame

22 may be substantially square with the wafer cassettes 14 attached at a first end thereof.

The transport subsystem 26 may lie adjacent to the cassettes 24.

[0043] The wafer cassettes 24 may lie at one end of the frame 22 and may be Front

Opening Unified Pods (FOUPs), as is commonly understood in the art. The cassettes 24

may be sized and shaped to hold a plurality of semiconductor substrates, such as wafers,

with diameters of, for example, 200 or 300 millimeters.

[0044] The transport subsystem 26 may include a transport track 34 and a transport

mechanism 36. The transport track 34 may be connected to the frame 22 and extend

between opposing sides of the frame 22 near the wafer cassettes 24. The transport

mechanism 36 may be able to support semiconductor substrates, such as wafers with

diameters of, for example, 200 or 300 millimeters and transport the substrates between each

of the cassettes 24 and the load-lock chamber 28.

[0045] The load-lock chamber 28 may be connected to the frame 22 between the transport

30. As is commonly understood in the art, the

load-lock chamber 28 may include a first door adjacent to the transport subsystem 26 and a

second door adjacent to the metrology chamber 30. Both doors may be able to hermetically

seal the transport subsystem 26 from the metrology chamber 30.

[0046] Referring to Figure IA in combination with Figure IB, the metrology chamber 30, a

robotic stage 40, an electromagnetic radiation source subsystem 42, a viewing, or camera,

subsystem 44, a magnetic lens 46, and a metrological analyzer 48. The chamber wall 38

may have an inner surface which, when viewed from above, has an "hourglass" shape as

illustrated in Figure IA. The inner surface of the chamber wall 38 may divide the

metrology chamber 30 into first 52 and second 54 portions. As shown, the first portion 52

may be located nearer to the load-lock chamber 28 than the second portion 54. The

metrology chamber 30 may also be hermetically sealed to form a vacuum chamber 50 as

shown schematically in Figure IB.

[0047] The robotic stage 40 may lie within the first portion 52 of the metrology chamber

30 and be directly connected to chamber wall 38. The robotic stage 40 may include a base

56, a robotic arm 58, and a substrate support 60. The robotic arm 58 may be rotatably

connected to the base 56 and include a first segment 62 attached directly to the base 56 and

a second segment 64 attached to an end of the first segment 62. The substrate support 60,

or "blade," may be connected to the second segment 64 of the robotic arm 58 at an end

opposing the first segment 62. As dictated by the structure of the robotic arm 58, the

robotic arm 58 may be able to move the substrate support 60 in a polar coordinate system

,|^~θ)f-y^tilϊ _' ^l|#^t.on^ttφ^ ⁱ .^::fcotation extending through the first portion 52 of the

metrology chamber 30. Additionally, the robotic arm 58 may be able to move the substrate

support 60 vertically (z-motion) within the metrology chamber 30. The substrate support

60 may be sized and shaped to support substrates, such as semiconductor wafers, with

diameters of, for example, 200 or 300 millimeters. The robotic stage 40 may be able to

extend the substrate support 60 into the second portion 65 of the metrology chamber 30, as

well as into the load-lock chamber 28.

[0048] It should be noted that because of the position of the base 56 of the robotic stage 40

(i.e., within the first portion 52 of the metrology chamber 30), when the robotic arm 58

extends the substrate support 60 into the second portion 54 of the metrology chamber 30,

none of the components of the robotic stage 40 are located below the substrate support 60.

[0049] As shown specifically in Figure IB, all of the components within the metrology

chamber 30 may be located within the vacuum chamber 50, except for the base 56 of the

robotic stage 40 and the magnetic lens 46, which both may be positioned below the vacuum

chamber 50.

[0050] Still referring to Figure IB, although not illustrated in detail, the magnetic lens 46,

or magnetic field generator, may be connected to the chamber wall 38 and positioned

below the second portion 54 of the metrology chamber 30. The magnetic lens is utilized to

focus electrons emitted from the substrate or specimen into an analyzer 48. The magnetic

lens produces a magnetic field, which has rotational symmetry about central axis 99. The

magnetic lens 46 may include a coil and be capable of generating a magnetic field within

)..Clin. an embodiment of the present invention, the magnetic lens

is a single pole piece lens sometimes referred to as a "snorkel lens".

[0051] Figure 1C illustrates the electromagnetic radiation source subsystem 42 and the

viewing subsystem 44 in greater detail. The electromagnetic radiation source subsystem 42

may include an electron source 66, an anode 68, and a monochromator 70.

[0052] Looking ahead to Figures 2 and 3, the electron source 66 may include an electron

gun 72 and a beam shaper 74, both held within a casing 76. In cross section, the casing 76

may be substantially rectangular with the electron gun 72 mounted at a first end thereof.

The casing 76 may have an opening 78 through an end thereof opposing the electron gun

72. As illustrated in Figure 2, the electron gun 72 may have a central axis 80, which passes

through the opening 78 in the casing 76.

[0053] Figure 3 illustrates the beam shaper 74 in greater detail. In cross section, the beam

shaper 74 may be substantially circular, include a plurality of poles 82, and have a beam

shaper opening 84 extending therethrough. In the example illustrated in Figure 3, the

beam shaper 74 may have eight poles 82 positioned equally around the beam shaper

opening 84. The central axis 80 of the electron gun 72, illustrated in Figure 2, may extend

through the beam shaper opening 84. As is commonly understood in the art, the poles 82

may form an "octopole" within the beam shaper 74, with each pole 82 being able to retain

either a positive or negative electric charge. In an embodiment of the present invention,

instead of using an "octopole" to shape the beam, an aperture or shutter can be used to

mechanically change and control the shape of the electron beam.

: 68 in greater detail. The anode 68 may be

substantially square with a target surface 86 on an upper side thereof and may be made of,

for example, aluminum. Although not illustrated in detail, the anode 68 may be movably

connected to chamber body 22 within the metrology chamber 30 to be capable of moving in

an x/y/z coordinate system.

[0055] Referring again to Figure 1C, the viewing subsystem 44 may include a camera 88,

an illuminator 90, and a reflective subsystem 92. The reflective subsystem 92 may include a

partial reflector 94, a focusing objective 96, and a deflection or turning mirror 98. The

camera 88 may be positioned directly above the partial reflector 94 and directed, or aimed,

at a central portion of the partial reflector 94. The illuminator 90 may be an optical light

source positioned to the side of the partial reflector 94 and directed, or aimed, at the central

portion of the partial reflector 94. The focusing objective 96 may be positioned to the side

of the partial reflector 94 opposing the illuminator 90. The deflection mirror 98 may be

positioned on a side of the focusing objective 96 opposing the partial reflector 94 and be

positioned directly above the magnetic lens 46. The deflection mirror 98 may be

substantially circular with an opening therethrough at a central portion thereof. As

illustrated in Figure 1C, a central axis 99 of the magnetic lens 46 may pass through the

opening in the primary mirror 98. The central axis 99 may be defined as the axis upon

which the magnetic field generated by the magnetic lens 46 has rotational symmetry.

[0056] Referring to Figure 1C, in combination with Figure 5, the focusing objective 96 may

include a lens 100, a primary mirror 102, and a secondary mirror 106. Referring specifically

mirror 102, and the secondary mirror 106 may be

substantially circular and centered about a common axis. Referring now to both Figures 1C

and 5, the primary mirror 102 may have a concave reflective surface 104 and an opening at

a central portion thereof. As illustrated specifically in Figure 1C, the secondary mirror 106

may have a convex reflective surface 108.

[0057] It should be noted that the viewing subsystem 44, and all of the components

thereof, may not have any moving, mechanical parts and be connected to the chamber wall

38 in a fixed position.

[0058] As illustrated in Figure ID, the metrology chamber 30 may also include a substrate

height detection subsystem 110 including a laser 112, a laser detector 114, and an array of

lenses 116 fixedly attached to chamber wall 38. The laser 112 and the laser detector 114

may be positioned on opposing sides of the metrological analyzer 48 and pointed toward

the central axis 99 of the magnetic lens 46.

[0059] Similarly, as illustrated in Figure 4, anode 68 may include an anode height

detection subsystem 210 including a laser 212, a laser detector 214 and an array of lens 216

in order to determine and precisely control the height of anode 68. The laser 212 and laser

detector 214 may be rigidly attached to chamber wall 38 and sighted at the focal point of

monochromator 70 on anode 68.

[0060] Referring again to Figure IB, the metrological analyzer 48 may include an aperture

positioned directly above the magnetic lens 46 and positioned such that the central axis 99

of the magnetic lens 46 passes therethrough. Although not illustrated in detail, the

include a detector and an electron spectrometer or

hemispherical analyzer, as is commonly understood in the art.

[0061] Although not illustrated in detail, it should be understood that all of the

components of the metrology tool may be connected to the frame and include various

actuators and power supplies to perform the various functions described below. In an

embodiment of the present invention, electrical signal and power are delivered to and

between various components in the vacuum chamber utilizing flex cables, such as

polyimide flex circuits.

[0062] Referring again to Figure IA, the computer control console 32 may be in the form

of a computer having a memory for storing a set of instructions and a processor connected

to the memory for executing the instructions, as is commonly understood in the art. The

instructions stored within the computer control console 32 may include methods and

processes, as well as various algorithms to carry out the methods and processes, for the

substrate movement and calibration, and operation of the metrology tool 20 as described

below. The instructions may further include what is commonly understood to be "pattern

recognition" software and software for translating between Cartesian and polar

coordinates. Also, the instructions may include analytical software for using the

components of the metrology tool 20 to determine the composition, including the

concentrations, of various layers of a substrate, as well as determining the thicknesses of

the various layers and the profile, depth distribution and depth distribution centroid of

different chemical spedes within the layers.

|QlP^^ ^I ^/%^!Iώlri|pπatel»eθlatlrøl»console 32 may be electrically connected to the transport

subsystem 26, the load-lock chamber 28, and the metrology chamber 30, as well as all of the

components within the metrology chamber 30.

[0064] In use, as illustrated in Figure 6, a substrate 118 may be inserted into one of the

substrate or wafer cassettes 24. A substrate for the purposes of the present invention is any

sample, specimen, or article upon which photoelectron spectroscopy is to be carried out in

apparatus 20. A substrate may include, but not limited to, a semiconductor wafer, such as

silicon monocrystalline substrate, a silicon-on-insulator substrate, or other types of

substrates used in the manufacture of integrated circuits, photomasks, flat panel displays,

or optical components. Additionally, a substrate may include one or more thin films or

layers, such as metal layers, semiconductor layers, and dielectric layers used to fabricate

features, such as but not limited to gate dielectric layers, gate electrodes, barrier layers,

interconnects, contacts, passivation layers, and micro-machines. In a specific embodiment

of the present invention, the substrate is a monocrystalline silicon wafer having a gate

dielectric layer, such as a silicon oxynitride dielectric or a metal oxide dielectric, such as

hafnium oxide or aluminum oxide, formed thereon. In an embodiment of the present

invention, apparatus 20 is used to determine the thickness, composition, and dopant

profile of a gate dielectric layer. The transport mechanism 36, may retrieve the substrate

118 from the cassettes 24 and transport the substrate 118 into the load-lock chamber 28.

The robotic stage 40 may then retrieve the substrate 118 from the load-lock chamber and

carry the substrate 118 from the first portion, or loading portion, 52 of the metrology

or testing portion, 54 of the metrology chamber 30.

[0065] Figure 7 illustrates the substrate 118 in greater detail- The substrate 118 may be a

semiconductor wafer, as is commonly understood in the art, with a diameter of, for

example, 200 or 300 millimeters. The substrate 118 may have a plurality of integrated

circuits 120 formed thereon and divided amongst multiple dice. The formation of the

integrated circuits 120 may only be partially completed. The substrate 118 may also

include a plurality of metrology pads 122, as is commonly understood in the art, located

between the integrated circuits 120. The metrology pads 122 may be, for example,

substantially rectangular with dimensions of 120 microns by 50 microns. Rectangular

metrology pads with one side larger man the other are ideal because they enable a large

area pad to be placed in the "scribe lines" between the product dice. The large area pads

enable increase number of electrons to be extracted from the metrology pad during testing

and thereby provide more information about the substrate surface. The integrated circuits

120 and the metrology pads 122 may be formed on an upper surface 124 of the substrate

118.

[0066] As illustrated in Figure 6 in combination with Figure 8A, the robotic stage may

position the substrate 118 between the magnetic lens 46 and the deflection mirror 98 such

that the magnetic lens 46 and the metrological analyzer 48 are on opposing sides of the

substrate support 60. The computer control console 32 may control the robotic stage 40 in

such a way that when the robotic arm 58 is moved, the substrate support 60, the first

segment 62 of the robotic arm 58, and the second segment 64 of the robotic arm 58 do not

,,αS illustrated specifically in Figure 8A, the robotic stage 40

may position the substrate 118 between the deflection mirror 98 and the magnetic lens 46.

[0067] It should be noted that, when the substrate support 60 is holding the substrate 118

within the second portion 54 of the metrology chamber 30, because the base 56 of the

robotic stage 40 is located within the first portion 52 of the metrology chamber 30 and does

not interfere with the positioning of the magnetic lens 46, the distance between the

substrate support 60 and the magnetic lens 46 may be particularly small. The distance

between an upper surface of the magnetic lens 46 and the lower surface of the substrate

support 60 may be less than 5 millimeters, such as between 2 and 4 millimeters.

Additionally, the distance from the upper surface 124 of the substrate 118 and the magnetic

lens 46 may be less than 8 millimeters.

[0068] Still referring to Figure 8A, the robotic stage 40 may position the substrate 118 such

that a particular one of the metrology pads 122, illustrated in Figure 7, is intersected by the

central axis 99 of the magnetic lens 46 (i.e., a first testing position). In order to verify that

the substrate 118 is properly positioned, the computer control console, illustrated in Figure

IA, may utilize the viewing subsystem 44 as illustrated in Figure 8A.

[0069] Referring to Figures 5 and 8A, optical light may be directed by the illuminator 90

through the partial reflector 94 and into the focusing objective 96. The light may pass

through the lens 100 and the opening within the primary mirror 102. The light may then be

reflected off the reflective surface 108 of the secondary mirror 106 back toward the primary

mirror 102. The concave reflective surface 104 of the primary mirror may reflect the light

the deflection mirror 98 as

illustrated in Figure 8A.

[0070] The light may then be reflected by the deflection mirror 98 onto the portion of the

substrate (i.e., the particular metrology pad 122 in the first testing position), which is

intersected by the central axis 99 of the magnetic lens 46. The light being reflected off of the

deflection mirror 98 onto the substrate 118 may be considered to be in a bundle with a

central axis that is coaxial to the central axis 99 of the magnetic lens 46. The light may then

be reflected off the substrate 118 back through the reflective system 92 and into the camera

88. Using the pattern recognition software described above, the computer control console

32, as illustrated in Figure IA, may be able to determine whether or not a metrology pad

122 as illustrated in Figure 7 is located properly in the testing position.

[0071] The viewing subsystem 44 is able to view the portion of the substrate 118 being

tested at an angle normal, or directly downward, on the substrate 118 while the testing is

taking place.

[0072] Still referring to Figure 8A, the electromagnetic radiation source subsystem 42 may

then be activated to direct x-rays onto the substrate 118. Referring now to Figure 2, the

electron gun 72 within the electron source 66 may be activated to emit a beam of electrons

126 through the beam shaper 74 and out of a casing 76 through the opening 78.

[0073] Figure 8B illustrates the beam shaper 74 as the beam of electrons 126 passes

therethrough. Various positive and negative electrical charges may be supplied to the poles

82 within the beam shaper so that a particular electric field is generated within the beam

^pq:.ςpiq^φ _i g _! §f|.,Asi;t|u^tst<|d specifically in Figure 8B, as the beam of electrons 126

passes through the beam shaper opening 84, the beam 126 may be shaped, or defocused, in

a particular direction. In the example illustrated, the beam 126 is shaped to have a

substantially rectangular cross-section, or shape, with a length 128 and width 130. The

length 128 may extend substantially in a first length direction 132 and the width 130 may

extend substantially in a first width direction 134. Referring once again to Figure 8A, the

beam may leave the electron source 66 and be directed onto the anode 68.

[0074] Figure 8C illustrates the anode 68 as the beam of electrons 126, illustrated in Figure

8B, strikes the anode target surface 86. As shown, the beam 126 may still have a

substantially rectangular shape with the length 128 extending in the first length direction

132 and the width extending 130 in the first width direction 134. At the target surface of

the anode, although not illustrated in detail, for example, the length 128 of the beam 126

may be approximately 84 microns and the width of the beam 126 may be approximately 45

microns. The power of the beam 126 may be, for example, more than 100 watts such as

approximately 200 watts. In an embodiment of the present invention, the e-beam is shaped

to produce an elongated e-beam profile having an aspect ratio (lengthrwidth) greater than

1:1 and preferably greater than 2:1 and in some embodiments greater than 3:1. In an

embodiment of the present invention, an e-beam profile having length between 20 and 200

microns and a width between 20 and 200 microns is formed. Additionally, in an

embodiment of the present invention, the power of the e-beam is between 4 and 200 watts.

As is commonly understood in the art, the electrons striking the anode 68 may cause x- rays

tp'lfc 'Iirøtέffifeb'itϊi..theSMati≥iiia.^of the anode 68. It is to be appredated that an anode can

only withstand a certain e-beam power level per area without being damaged. By forming

an elongated beam and by increasing the area of the beam, more power can then be placed

in the beam, thereby enabling more X-rays to be generated without damaging the anode.

Doubling the area of the e-beam enables doubling of the power applied to the anode

without damaging the anode.

[0075] Referring back again to Figure 8A, the beam of x-rays 127 may propagate from the

anode 68 onto the monochromator 70, which redirects and focuses only selected

frequencies of the x-rays toward the substrate 118.

[0076] Figure 8D illustrates the substrate 118 as the beam of x-rays 127 strikes the upper

surface 124 thereof. As shown, the X-ray beam 127 may maintain the same relative shape

and orientation on the substrate 118 as the shape, size and orientation of the e-beam on

anode 68. The x-ray beam 127, however, may take on a slightly larger size than ebeam 126.

The use of a large area monochromator with a large collection angle enables the shape of

the X-ray beam 127 on substrate 118 to be highly correlated with the shape and orientation

of the e-beam 126 on anode 68. In an embodiment of the present invention, the X-ray beam

has an elongated oval or rectangular shape with an aspect ratio (lengthrwidth) of at least

1:1, and preferably greater than 2:1, and in some embodiments greater than 3:1. In a

specific embodiment X-ray 127 may have a length of more than 100 microns, specifically in

the example illustrated, approximately 110 microns and a width of approximately 40

microns to match the dimensions of the metrology pad 122.

|l^)7^\/I#SMjik&aovepαif»oses _/ αespite the fact that the e-beam 126 and X-ray beam 127

have been directed off of several surfaces, the image formed by the beam may still be

considered to have a length extending in the first length direction 132 and a width

extending in the first width direction 134.

[0078] As is commonly understood in the art, referring to Figure 8 A in combination with

Figure IB, as the x-rays 127 bombard the material on the substrate 118, at the atomic level,

electrons within the material on the metrology pad 122 may become energized and be

ejected from their respective orbitals of the atoms within the materials on the metrology

pads of the substrate 118.

[0079] As will be appreciated by one skilled in the art, the magnetic lens 46 may be

activated to generate a magnetic field within the metrology chamber 30, which has a

rotational symmetry about the central axis 99 of the magnetic lens 46. Thus, the electrons,

or photoelectrons 200, may be guided by the magnetic field directly upwards along the

central axis 99, pass through the opening within the deflection mirror 98, and enter the

aperture and the detector of the electron spectrometer or hemispherical analyzer of the

metrological analyzer 48. As the photoelectrons propagate from the substrate 118 to the

analyzer 48, the photoelectrons may be arranged in a bundle with a central axis which is

coaxial with the central axis of the bundle of visible light and the central axis 99 of the

magnetic lens 46. Thus, the direction in which the visible light from the viewing subsystem

44 propagates onto the substrate 118 may be substantially parallel to the direction in which

the photoelectrons propagate from the substrate 118 into the analyzer 48.

J[QQSQl,. ,J£ jsfecpMhe "*P.|ed ^! $ja| because of the close proximity of the magnetic lens 46 to the

substrate 118, the effectiveness of the magnetic field in guiding the photoelectrons is

maximized. Additionally, as illustrated in Figure IB, because the magnetic lens is not

positioned within the vacuum chamber 50, if the magnetic lens requires any maintenance,

the magnetic lens 46 may be accessed without exposing the components within the vacuum

chamber to outside air.

[00811 The electron spectrometer or hemispherical analyzer may determine the

composition of a material on the metrology pad on a substrate 118 based on the kinetic

energy, or speed, of the electrons.

[0082] Additionally, as previously mentioned, the metrology tool 20 may also determine

the thicknesses of the various layers and the profile, distribution and depth distribution

centroid of different chemical species within the layers upon substrate 118.

[00831 As illustrated in Figures 8A and 9A, the substrate support 60 may then be moved

to position a different metrology pad 122 above the central axis 99 of the magnetic lens 46

(i.e., a second testing position). As described above, because of the structure of the robotic

stage 40, the substrate support 60 may move the substrate 118 in a polar coordinate system

(R, θ). Thus, when the substrate 118 is moved to test a different metrology pad 122, the

substrate 118 may undergo a rotation such that the metrology pads 122 are oriented

differently with respect to the remainder of the metrology chamber 30 when compared to

the first testing position.

[0084] Referring again to Figure 8A, the electron source 66 may again be activated to

[0085] Figure 9B illustrates the beam shaper 74 within the electron source 66 as the

substrate 118 is oriented as shown in Figure 9A. As shown in Figure 9B, in order to match

the rotated orientation of the substrate, a different electric field may be generated by the

poles 82. As shown, the beam 126 may still be substantially rectangular in shape, however,

the length 128 and the width 130 of the beam 126 may be rotated relative to the beam 126

illustrated in Figure 8B. As shown in Figure 9B, the length 128 may now extend in a second

length direction 136 and the width 130 may now extend in a second width direction 138.

[0086] Figure 9C illustrates the anode 68 as the beam 126 illustrated in Figure 9B strikes

the anode target surface 86. As shown, the beam 126, as indicated on the anode target

surface 86, may have been rotated relative to the beam 126 on the anode target surface 86

illustrated in Figure 8C.

[0087] Additionally, in order to expose "fresh" material on the anode 68, the anode 68

may have been moved in the x/y plane so that a second portion of the target surface 86 of

the anode 68 may be struck with the beam 126. Therefore, the number of x-rays, which

propagate from the anode 68 may be maximized. The second portion of the anode that is

struck with the beam may at least partially overlap the portion that the beam 126 initially

struck.

[0088] As described above, and illustrated in Figure 8A, x-ray 127 may be propagated

from the anode 68 and redirected by the monochromator 70 onto the substrate 118. Figure

9D illustrates the substrate 118 in the angular orientation shown in Figure 9A, as the beam

f. As shown, the beam 127 has been rotated to

match the angular orientation of the metrology pads 122. Therefore, the beam 127 is

capable of substantially covering the entire metrology pads 122 despite the fact that the

metrology pads 122 have been rotated.

[0089] Referring again to Figure 8A in combination with Figure IB, electrons may be

emitted by the materials on the metrology pad 122 through the opening in the primary

mirror 98 and into the metrological analyzer 48 as described above.

[0090] The rotating, or shaping, the nature of the electron beam described above,

increases the speed at which substrates may be tested, particularly when the robotic stage

moves the substrates in a polar coordinate system. The efficiency and accuracy of the

testing is also improved by moving the beam of electrons on the target surface of the

anode, as the number of x-rays which strike the substrate, as well as the number of

photoelectrons which are collected by the metrological analyzer, is maximized.

[0091] Additionally, it is to be appreciated that the combination of beam shaping and the

viewing system enables a fast and accurate acquisition of metrology targets across the

surface of substrate 118 when utilizing robot 40 as a stage for testing substrate 118. The

location of various metrology pads 122 on substrate 118 are preprogrammed into computer

32. The computer then directs movement of the substrate support 60 to place the

metrology pad 122 beneath the analyzing beam location. However, because the substrate

may be misplaced on the support resulting in the substrate being "off centered" the exact

location of the metrology pads may not be known. Additionally, movement of the robotic

s^b^^e-fπi^^i^e^apfl^^^^^-ll^Rl^ictable and imprecise adding further difficulty because the

exact position of the substrate may not be known. Accordingly, the preprogrammed

locations of the metrology pads may not accurately place the metrology pads directly or

precisely beneath the x-ray beam. Accordingly, in embodiments of the present invention,

the viewing system along with pattern recognition software may be used to move the

substrate support and therefore the metrology pad closer to its proper location. In an

embodiment of the present invention, once the metrology pad is moved closer to the

proper location the e-beam 126 can be precisely steered on the anode and accurately locate

the x-ray beam directly over the metrology pad to be tested. In an embodiment of the

present invention, the robot and viewing system are used to move the metrology pads to

be tested to within about 10-50 microns of the proper location and then the e-beam 126

shaped and moved to locate the x-ray beam 127 precisely over the metrology pad. In this

way, a somewhat imprecise robot can be used to provide a perfectly precise stage for

placing substrate metrology areas under the x-ray beam 127.

[0092] Figures 10 A-IOC illustrate the correction of the height of the substrate 118 relative

the viewing subsystem 44 and the electromagnetic radiation source subsystem 42

illustrated in Figure IB. As shown in Figure 1OA, the laser 112 may direct a beam of laser

light through the array of lenses 116 off of the upper surface of the substrate 118. The laser

light may then strike and be detected by a laser detector 114. As illustrated in Figure 1OB,

as the robotic arm 58 moves the substrate 118 between various positions within the

metrology chamber 30, due to imperfections of the movement of the robotic arm, as well as

iϊηperfeς$qp _$ ©f ^es^ibf trafe 1$L8, such as variations in thickness and changes to the height

of the upper surface 124 due to bowing or warping, the laser light that is reflected from the

upper surface 124 of the substratellδ may not enter the laser detector 114 at the same

location.

[0093] Thus, the laser detector, in combination with the computer control console

illustrated in Figure IA, may be able to detect variations in the height of the upper surface

124 of the substrate 118. As illustrated in Figure 1OC, the robotic arm 58 may then adjust

the height of the substrate support 60, and thus the upper surface 124 of the substrate 118

to maintain a constant distance from the other components within the metrology chamber

30 as illustrated in Figure IB. Additionally, as illustrated in Figure 4, anode 68 is connected

to a stage, which enables anode 68 to be moved in a xy plane as well as in a vertical

direction (z direction). The height detector subsystem 210 enables the height of anode 68 to

be precisely. The height detector subsystem 210 includes a laser beam 212 and an array of

lens 216 to shine a laser light onto the upper surface of anode 68. The laser light may then

be detected by a laser detector 214. The laser and detector enable the anode height to be

precisely measured and controlled.

[0094] The ability to precisely control the anode in the vertical direction (z direction)

allows the surface of the anode to be precisely located at a focal point of the

monochromator even when the anode surface may be nonplanar. In this way, the anode

may be moved in the xy plane, and any nonplanarity in the anode surface compensated for

by adjusting the anode height. Similarly, the ability to precisely control the substrate

SjJ ₍ PpO ₁ Pt fa ψι% direction), allows the surface of the substrate to be

precisely located at a focal point of the monochromator even when the height of the

substrate surface may vary due to substrate nonplanarity, warpage or robot imprecision.

[0095] One advantage is that the robotic stage may be used to retrieve substrates from the

load-lock chamber, as well as position the substrates under the electromagnetic radiation

source subsystem. Therefore, a separate machine is not needed to remove the substrates

from the load-lock chamber, which reduces the cost of the metrology tool.

[0096] Another advantage is that because a single machine is used to remove the

substrates from the load-lock chamber and position them into the test position, when in the

test position, the space immediately below the substrate support may be vacant of any

hardware necessarily for the movements of the substrate. Therefore, the magnetic lens may

be positioned more closely to the substrate support, which increases the effectiveness of the

magnetic field generated by the magnetic lens in guiding the electrons from the substrate

into the metrological analyzer and/or reduces the strength of the magnetic field that is

necessary to effectively guide the electrons into the metrological analyzer.

[0097] A further advantage is that the portion of the substrate that is being tested may be

viewed by the viewing subsystem in a direction that is normal to the upper surface of the

substrate. Additionally, the portion of a substrate that has been tested may be viewed

while the testing is taking place.

[0098] A further advantage is that because the magnetic lens is located outside of the

vacuum chamber, any repairs required on the magnetic lens may be performed without

logy chamber to outside air. Therefore, the likelihood of

any contamination within the metrology chamber is reduced. A further advantage is that

the viewing subsystem contains no moving parts.

[0099] Other embodiments may utilize only certain aspects of the system described above.

For example, the magnetic lens described as being positioned outside of the vacuum

chamber may be used without the particular viewing system described.

[00100] While certain exemplary embodiments have been described and shown in the

accompanying drawings, it is to be understood that such embodiments are merely

illustrative and not restrictive of the current invention, and that this invention is now

restricted to the specific constructions and arrangements shown and described since

modifications may occur to those ordinarily skilled in the art.