WO2020190919A1 - Sample holder, system and method - Google Patents

Sample holder, system and method Download PDF

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Publication number
WO2020190919A1
WO2020190919A1 PCT/US2020/023108 US2020023108W WO2020190919A1 WO 2020190919 A1 WO2020190919 A1 WO 2020190919A1 US 2020023108 W US2020023108 W US 2020023108W WO 2020190919 A1 WO2020190919 A1 WO 2020190919A1
Authority
WO
WIPO (PCT)
Prior art keywords
sample
sample holder
holder according
radiation
placement surface
Prior art date
Application number
PCT/US2020/023108
Other languages
French (fr)
Inventor
Thomas Anthony Case
Susan CANDELL
Naomi KOTWAL
Allen GU
Zheren WU
Wayne BRODERICK
Original Assignee
Carl Zeiss Smt Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Carl Zeiss Smt Inc. filed Critical Carl Zeiss Smt Inc.
Priority to KR1020217033494A priority Critical patent/KR102564495B1/en
Priority to CN202080022103.1A priority patent/CN113785192A/en
Publication of WO2020190919A1 publication Critical patent/WO2020190919A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/046—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/06—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption
    • G01N23/083—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption the radiation being X-rays
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/03—Investigating materials by wave or particle radiation by transmission
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/10—Different kinds of radiation or particles
    • G01N2223/101—Different kinds of radiation or particles electromagnetic radiation
    • G01N2223/1016—X-ray
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/30—Accessories, mechanical or electrical features
    • G01N2223/307—Accessories, mechanical or electrical features cuvettes-sample holders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/40—Imaging
    • G01N2223/419—Imaging computed tomograph
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/611—Specific applications or type of materials patterned objects; electronic devices
    • G01N2223/6113—Specific applications or type of materials patterned objects; electronic devices printed circuit board [PCB]

Definitions

  • the present disclosure relates to a sample holder for holding a sample during an X-ray imaging process, to a system comprising such a sample holder and to a method for performing an X-ray imaging process using such a sample holder.
  • 3D X-ray imaging techniques such as X-ray microscopy (XRM) and microCT have become established failure analysis (FA) tools for bridging fault isolation and physical failure analysis (PFA), because they enable the visualization of defects without having to destroy the device under test. Furthermore, these tools provide FA analysts with better information for determining the best approach to conduct PFA for root cause analysis.
  • the XRM advantages of non-destructive, high- resolution imaging make it an excellent option for routine inspection of semicon ⁇ ductor package features such as traces, C4 bumps, and micro-bumps.
  • MicroCT is also valuable, although its resolution when applied to larger sample geometries is lower than the resolution that can be achieved with XRM. Since XRM and mi ⁇ croCT share significant similarities, the terms will be used interchangeably in the rest of the document.
  • XRM set-up and acquisition times have limited its proliferation and adoption be ⁇ yond FA and manual measurement applications.
  • XRM workflow improvements offer the opportunity to realize the efficiency and throughput benefits of auto ⁇ mated device handling for productivity in high-resolution, site-specific inspection and measurement applications.
  • sample holder For performing XRM, there is a need to accurately and repeatably fix one or more samples, for example integrated circuit (IC) packages, to a sample holder such that the sample remains securely held without movement in the presence of X- ray radiation. It is indispensable that the sample’s placement on the sample holder does not significantly vary in all three spatial dimensions between differ ⁇ ent sample holders or repeated uses on the same sample holder.
  • IC integrated circuit
  • a sample holder for holding a sample during an X-ray imaging pro cess.
  • the sample holder comprises a sample placement surface on which the sample is placed for positioning the sample in a depth direction of the sample holder, a first alignment portion for aligning the sample in a width direc ⁇ tion of the sample holder, and a second alignment portion for aligning the sample in a height direction of the sample holder.
  • the sample holder Due to the fact that the sample holder has the sample placement surface and the two alignment portions, it is possible to accurately and repeatably position the sample in all three spatial directions. Hence, the sample remains securely held without movement in the presence of X-ray radiation.
  • the placement of the sam ⁇ ple does not significantly vary in the three spatial directions between different sample holders or repeated uses on the same sample holder.
  • the X-ray imaging process preferably is XRM.
  • the sample can be an electronic device, in particular an IC package.
  • the sample placement surface is preferably a flat surface of the sample holder on which the sample can be placed.
  • the align ⁇ ment portions are preferably bar-shaped and are arranged on two different edges of the sample placement surface.
  • the sample placement surface preferably is rec ⁇ tangular.
  • the sample placement surface can easily be adapted to different sizes of the sample.
  • the sample placement surface in particular is a plane that is de ⁇ fined by the width direction and the height direction.
  • the first alignment portion runs along the height direction.
  • the second align ⁇ ment portion runs along the width direction.
  • the first alignment portion can be named vertical ledge.
  • the second alignment portion can be named horizontal ledge.
  • a first edge of the sample abuts the first alignment portion and a second edge of the sample abuts the second alignment portion.
  • the sample is therefore guided by the alignment portions into a corner of a sample receiving section of the sample holder.
  • the corner is a right bottom corner of the sample receiving section.
  • the alignment portions can also serve as X-ray alignment marks, in par ⁇ ticular as so-called fiducials.
  • the sample holder preferably has a coordinate system with a first spatial direc ⁇ tion or x-direction, a second spatial direction or ydirection and a third spatial direction or z-direction.
  • the spatial directions are arranged perpendicular to each other.
  • the z-direction has to be understood as the depth direction.
  • the x-direction has to be understood as the width direction.
  • the ydirection has to be understood as the height direction.
  • the sample can be positioned on the sample holder as follows. In a first step, the sample is placed on the sample placement surface for positioning the sample in the depth direction of the sample holder. In a second step, the sample is abutted on the first alignment portion for aligning the sample in the width direction of the sample holder. In a third step, the sample is abutted on the second alignment portion for aligning the sample in the height direction of the sample holder.
  • the afore-mentioned steps can be performed at the same time or one after another. The third step can be performed after the second step or vice versa.
  • the first alignment portion is arranged perpendicu ⁇ lar to the sample placement surface, wherein the second alignment portion is ar ⁇ ranged perpendicular to the sample placement surface and perpendicular to the first alignment portion.
  • the sample placement surface, the first alignment portion and the second align ⁇ ment portion in this way form the box-shaped sample receiving section which re ceives and aligns the sample in all three spatial directions.
  • the sam ⁇ ple receiving section is open on two sides, whereas two other sides are closed by the alignment portions that work as side walls of the sample receiving section.
  • a cut-out is placed at an intersection of the first alignment portion and the second alignment portion.
  • the cut-out is circular.
  • the cut-out can be a bore that is placed at the intersection of the two alignment portions.
  • the cut-out receives a corner of the sample.
  • the sample holder further comprises a fixing element for pressing the sample against the sample placement surface, against the first alignment portion and against the second alignment portion.
  • the fixing element allows a user to exert an adequate holding force between the sample and the sample holder.
  • time is saved by the quick-assembly, quick-release of the samples by means of the fixing element. No cleaning of the samples and/or the sample holder is needed since no adhesive is used to fix the sample to the sample holder.
  • the fixing element can be used several times.
  • the fixing element runs diagonally over the sample placement surface.
  • the fixing element runs between two transversely oppo ⁇ site corners of the sample placement surface. Hence, the fixing element also runs diagonally over the sample thus fixing it securely to the sample holder.
  • the fixing element is made of a flexible and radiation-stable material, in particular of ethylene propylene diene methylene rubber.
  • the fixing element is therefore flexible or elastic.
  • the fixing ele ⁇ ment can be stretched.
  • the fixing element can be named elastic fixing element.
  • the fixing element can be an Oring.
  • the sample holder further comprises a first hook portion and a second hook portion, wherein the fixing element is hooked into the first hook portion and into the second hook portion.
  • the first hook portion and the second hook portion are preferably arranged at two opposite corners of the sample placement surface.
  • the sample placement surface is arranged between the first hook portion and the second hook portion.
  • the hook portions are arranged diagonally so that the fixing element runs diago ⁇ nally over the sample and fixes it to the sample holder.
  • the sample holder further comprises a rear surface which is arranged opposite the sample placement surface, wherein the first hook portion has a first notch which is provided in the rear surface for re ⁇ ceiving the fixing element, and wherein the second hook portion has a second notch which is provided in the rear surface for receiving the fixing element.
  • the fixing element is thus prevented from slipping off the hook portions.
  • the first hook portion is arranged flush with the sample placement surface, wherein the second hook portion protrudes from the sample placement surface in the depth direction.
  • the sample holder further comprises a sam ⁇ ple receptacle which has a plurality of sample receiving sections, wherein each sample receiving section has a sample placement surface, a first alignment por ⁇ tion and a second alignment portion.
  • sample receiving sections are arbitrary. For example, there are provided three sample receiving sections. Each sample receiving section is capa ⁇ ble of receiving one sample. Each sample receiving section has a fixing element. When regarded along the height direction, the sample receiving sections are ar ⁇ ranged in a row.
  • the sample receptacle is integrally formed.
  • the phrase "integrally formed" refers to a structure formed from the same mate ⁇ rial or materials using a single, continuous process.
  • the three-dimensional printer can emit the same material or materials during the printing process to form the sample receptacle as a single piece.
  • the sample receptacle is preferably made of a material that allows the radiation to readily pass through the sample receptacle.
  • the materials used for producing the sample receptacle can include aluminum, glassy carbon, epoxy filled with glass fiber or other low-attenuating and structurally-stable materials.
  • the sample holder further comprises a post to which the sample receptacle is attached and a gripper disc to which the post is attached, wherein the post is fixed to the gripper disc in a form-locking manner by means of a key connection.
  • the post can be made of aluminum or any other suited material.
  • the post prefer ⁇ ably has a circular cross-section.
  • the sample receptacle can be attached to the post by means of fixing elements like screws.
  • a pin connection be ⁇ tween the sample receptacle and the post can be provided.
  • the pin connection comprises an alignment pin and two bores for receiving the alignment pin.
  • One bore is provided at the sample receptacle and one bore is provided at the post.
  • the gripper disc is suitable for being gripped by a gripper or robot.
  • the gripper disc has a central bore which receives an end of the post.
  • the sample holder fur ⁇ ther comprises a base plate to which the gripper disc is attached.
  • a "form locking" connection can be created by two elements engaging and blocking each other.
  • the post can have a keyway for receiving a key, in particular a woodruff key.
  • the cen ⁇ tral bore of the gripper disc has a notch for
  • the system comprises a radiation source that emits radiation, a radiation detector that receives the radiation emitted from the radiation source, and at least one sample holder as explained before, wherein the sample holder is arranged be ⁇ tween the radiation source and the radiation detector.
  • the system is preferably an XRM system.
  • the System can have a plurality of sample holders. Each sample holder can hold a plurality of samples.
  • the sample holder holds at least one sample.
  • the radiation detector receives or detects radiation that passed through the sample and the sample holder.
  • a method for performing an X-ray imaging process using such a sample holder comprises the following method steps : a) placing the sample on the sample holder, b) emitting radiation by means of a radiation source, and c) receiving radiation passed through the sample by means of a radi ⁇ ation detector.
  • the radiation also passes through the sample holder.
  • the method steps a) to c) can be performed all at the same time or one after another.
  • the sample holder with the sample or the samples is preferably rotated stepwise into a plurality of positions. In each posi ⁇ tion, at least one X-ray image is taken. All the gathered X-ray images together form a three-dimensional data set of the sample, in particular of a region of in ⁇ terest of the sample.
  • sample holder The features disclosed for the sample holder are applicable to the system as well as to the method and vice versa.
  • Fig. 1 shows a schematic perspective view of one embodiment of a sample holder
  • Fig. 2 shows a schematic exploded view of the sample holder according to Fig. V
  • Fig. 3 shows a schematic cross-sectional view of the sample holder according to Fig. i;
  • Fig. 4 shows a schematic perspective view of one embodiment of a sample recep ⁇ tacle for the sample holder according to Fig. V,
  • Fig. 5 shows a schematic front view of the sample receptacle according to Fig. 4;
  • Fig. 6 shows a schematic rear view of the sample receptacle according to Fig. 4;
  • Fig. 7 shows a schematic cross-sectional view of the sample receptacle according to the intersection line VII -VII of Fig. 5;
  • Fig. 8 shows a schematic block diagram of one embodiment of a method for per ⁇ forming an X-ray imaging process using the sample holder according to Fig. 1.
  • Fig. 1 shows a schematic perspective view of one embodiment of a sample holder 100 for holding samples (not shown) during X-ray imaging, in particular X-ray CT imaging, of the samples.
  • Fig. 2 shows an exploded view of the sample holder 100.
  • Fig. 3 shows a cross-sectional view of the sample holder 100. In the follow ⁇ ing, Figs. 1 to 3 are referred to at the same time.
  • the sample holder 100 is used for high-resolution 3D X-ray micros ⁇ copy (XRM) of semiconductor package interconnects.
  • the sample holder 100 has a base plate 102.
  • the base plate 102 has a flattened cylindrical shape and is pro ⁇ vided with a lateral flattening 104.
  • the base plate 102 further has an upper side 106 and a lower side 108.
  • the sides 106, 108 are arranged parallel to each other.
  • the base plate 102 has a stepped bore 110 which is arranged centrally in the base plate 102.
  • the bore 110 breaks through the base plate 102.
  • Further stepped bores 112 are provided in the base plate 102.
  • the number of bores 112 is arbi ⁇ trary. For example, there are provided three bores 112.
  • Fixing elements 114, 116 are encompassed in the bores 110, 112.
  • the fixing ele ⁇ ments 114, 116 can be screws.
  • the lower side 108 is placed on a stage (not shown).
  • the stage can laterally move the sample holder 100 in a first spatial di ⁇ rection or x-direction x, a second spatial direction or ydirection y and a third spa tial direction or z-direction z.
  • the x-direction x is named width direction of the sample holder 100
  • the ydirection y is named height direction of the sample holder 100
  • the z-direction z is named depth direction of the sam ple holder 100.
  • the stage can also rotate the sample holder 100 around the height direction y.
  • the base plate 102 is preferably made of metal.
  • the base plate 102 can be made of aluminum, steel or other suitable materials.
  • the sample holder 100 further comprises a gripper disc 118.
  • the gripper disc 118 has a flat cylindrical shape with an upper side 120 and a lower side 122.
  • the sides 120, 122 are arranged parallel to each other.
  • the lower side 122 is placed on the upper side 106 of the base plate 102.
  • the gripper disc 118 is laterally flat ⁇ tened on two sides.
  • One of the sides has a notch 124, whereas the other side has a conical bore 126.
  • the notch 124 and the bore 126 can be used to grip the sample holder 100 by means of a gripping robot (not shown).
  • the gripper disc 118 has a number of threaded bores 128 into which the fixing elements 116 are screwed to fix the gripper disc 118 to the base plate 102.
  • the bores 128 can break through the gripper disc 118.
  • the gripper disc 118 comprises a central bore 130 which breaks through the gripper disc 118.
  • the bore 130 is provided with a notch 132 which runs in the height direction y.
  • the gripper disc 118 is made of metal.
  • the gripper disc 118 is made of aluminum.
  • the gripper disc 118 can also be made of steel or other suitable materials.
  • a post 134 is received in the bore 130.
  • the post 134 has a keyway 136 which re ⁇ ceives a key 138.
  • the key 138 is a woodruff key.
  • the key 138 engages with the notch 132 of the gripper disc 118 and prevents the post 134 from rotating rela ⁇ tively towards the gripper disc 118.
  • the post 134 is fixed to the base plate 102 by means of the fixing element 114 which is screwed into a central bore 140 of the post 134.
  • the woodruff key 138 other keys can also be used.
  • the post 134 is preferably made of metal.
  • the post 134 can be made of alumi ⁇ num.
  • the post 134 has a lateral flattening 142 with two threaded bores 144, 146.
  • the bores 144, 146 receive fixing elements 148, 150.
  • the fixing elements 148, 150 can be screws.
  • Between the bores 144, 146 a further bore 152 is arranged.
  • the bore 152 receives an alignment dowel or alignment pin 154.
  • the sample holder 100 has a source side 156 which faces a radiation source 500, in particular an X-ray source, and a detector side 158 which faces a radia ⁇ tion detector 600, in particular an X-ray detector.
  • the radiation source 500 emits radiation 502, in particular X-rays.
  • the radiation detector 602 detects radiation 504 passed through the sample holder 100 and the sample placed in the sample holder 100.
  • the sample holder 100, the radiation source 500 and the radiation detector 600 are part of a system 1000 for performing an X-ray imaging process, in particular an XRM process.
  • the system 1000 is an XRM system or an X-ray CT system.
  • the sample holder 100 comprises a sample receptacle 200 which is fixed to the post 134 by means of the alignment pin 154 and the fixing elements 148, 150.
  • the sample receptacle 200 is shown in different views in Figs. 4 to 7. In the fol ⁇ lowing, Figs. 4 to 7 are referred to at the same time.
  • the sample receptacle 200 is made of a material that allows the radiation 502 to readily pass through the sample receptacle 200.
  • the sample recep ⁇ tacle 200 may be formed from a polymeric material such as plastic.
  • the sample receptacle 200 may be formed using a three-dimensional print ⁇ ing apparatus ("3D printer") allowing the sample receptacle 200 to include a va ⁇ riety of customizable sizes and shapes to carry a variety of samples.
  • 3D printer three-dimensional print ⁇ ing apparatus
  • a "three- dimension printer” refers to a printing apparatus that emits a polymeric material in order to form a three-dimensional structure.
  • the sample receptacle 200 may be formed by other methods.
  • the sample receptacle 200 may include a polymeric material which is injec ⁇ tion molded into a mold cavity that defines the size and shape of the sample re ⁇ ceptacle 200.
  • the sample receptacle 200 may be formed from a block of polymeric or metal material that undergoes a material removal process.
  • the ma ⁇ terials used for producing the sample receptacle 200 can include aluminum, glassy carbon, epoxy filled with glass fiber or other low-attenuating and structur- allystable materials.
  • the sample receptacle 200 is preferably integrally formed.
  • the sample receptacle 200 is bar-shaped and has a base portion 202 which is fixed to the post 134.
  • the base portion 202 has two stepped bores 204, 206 for receiving the fixing elements 148, 150 and one bore 208 for receiving the alignment pin 154.
  • the alignment pin 154 is used for exactly positioning the sample receptacle 200 at the post 134.
  • the fixing elements 148, 150 are used for attaching the sample receptacle 200 to the post 134.
  • the sample receptacle 200 comprises a number of sample receiving sections 210, 212, 214.
  • the number of sample receiving sections 210, 212, 214 is arbitrary. For example, there are provided three sample receiving sections 210, 212, 214.
  • the sample receptacle 200 may accommodate more or less sample receiving sections 210, 212, 214, depending on the scanning range of the system 1000.
  • Each sample receiving sections 210, 212, 214 is capable of receiving one sample 300 (see Fig.
  • the sample 300 can be an electronic device like an integrated circuit.
  • the sample receiving sections 210, 212, 214 are arranged in a row when being viewed in the height direction y.
  • the sample receiving sections 210, 212, 214 are at ⁇ tached to each other.
  • the sample receiving sections 210, 212, 214 are integrally formed. All sample receiving sections 210, 212, 214 have the same technical fea- tures. For this reason, in the following only the sample receiving sections 214 is referred to.
  • the sample receiving section 214 is generally plate shaped and has a sample placement surface 216 and a rear surface 218.
  • the sample placement surface 216 is oriented towards the radiation detector 600 and the rear surface 218 is oriented towards the radiation source 500.
  • the sam ⁇ ple 300 is placed on the sample placement surface 216.
  • the sample receiving sec ⁇ tion 214 has a first alignment portion 220 and a second alignment portion 222.
  • the sample 300 can be positioned in the depth direction z.
  • the sample holder 100 can be placed such that the sample placement surface 216 faces the radiation source 500 and the rear surface 218 faces the radiation detector 600. So, the sample 300 can be positioned to face the radiation detector 600 or to face the ra ⁇ diation source 500.
  • the first alignment portion 220 runs along the height direction y and is capable of positioning the sample 300 in the width direction x.
  • the first alignment por ⁇ tion 220 is a vertical ledge or can be named vertical ledge.
  • the second alignment portion 222 runs along the width direction x and is capable of positioning the sample 300 in the height direction y.
  • the second alignment portion 222 is a hori ⁇ zontal ledge or can be named horizontal ledge.
  • the alignment portions 220, 222 are arranged perpendicular to each other.
  • the alignment portions 220, 222 can also serve as X-ray alignment marks, in particular as so-called fiducials.
  • the sample 300 can have four lateral edges 302, 304, 306, 308.
  • two of the edges 306, 308 of the sample 300 are guided along the first alignment portion 220 and the second alignment portion 222 till the sample 300 is positioned in a bottom right corner (see Fig. 5) of the sample receiving section 214.
  • the sample re ⁇ DCving section 214 is capable of positioning the sample 300 in all three spatial directions x, y, z.
  • Other alignment portions can be used such that the origin of the sample 300 is elsewhere than the bottom right corner of the sample receiving section 214.
  • a circular cut-out 224 is arranged where the alignment portions 220, 222 inter ⁇ sect.
  • the cut-out 224 receives a corner of the sample 300.
  • the sample placement surface 216 can be bordered by an upper edge 226.
  • the sample receiving section 210 does not have such an upper edge 226.
  • a circular cut-out 228 is provided where the upper edge 226 and the first alignment portion 220 intersect each oth ⁇ er.
  • the sample receiving section 214 further comprises a first hook portion 230 and a second hook portion 232 which are arranged diagonally.
  • each hook portion 230, 232 has a notch 234, 236.
  • the first hook portion 230 has a first notch 234.
  • the second hook portion 232 has a second notch 236.
  • the hook portions 230, 232 are capable of receiving an elastic fixing element 400 (see Fig.
  • the second hook portion 232 is arranged between two notches 238, 240 that break through the alignment portions 220, 222.
  • the fixing element 400 runs through the notches 238, 240. By means of the fixing element 400, the sample 300 can be pressed against the sample placement surface 216 and against the alignment portions 220, 222.
  • the fixing element 400 runs through the notches 234, 236.
  • the fixing element 400 can be an O-ring.
  • the fixing element 400 is made of a flexible and radiation-stable material.
  • the fixing element 400 can be made of ethylene propylene diene methylene rubber (EPDM).
  • EPDM ethylene propylene diene methylene rubber
  • the sample 300 is placed on the sample placement surface 216 for positioning the sample 300 in the depth direction z of the sample holder 100.
  • the sample 300 is abutted on the first alignment portion 220 for aligning the sample 300 in the width direction x of the sample holder 100.
  • the sample 300 is abutted on the second alignment portion 222 for aligning the sample 300 in the height direction y of the sample holder 100.
  • the third step can be performed after the second step or vice versa.
  • the afore mentioned steps can be performed at the same time or one after another.
  • the last two steps can be performed by applying the fixing element 400.
  • the fixing element 400 press ⁇ es the sample 300 against the alignment portions 200, 222.
  • the fix ⁇ ing element 400 can be applied after performing aligning the sample 300.
  • each sample receiving section 210, 212, 214 a sample 300 is placed.
  • the sam ⁇ ples 300 are aligned on the sample placement surface 216 of each sample receiv ⁇ ing section 210, 212, 214 by means of the alignment portions 220, 222.
  • fixing elements 400 are hooked into the hook por ⁇ tions 230, 232 of each sample receiving section 210, 212, 214.
  • the fixing elements 400 press the samples 300 against the sample placement surface 216 and the alignment portions 220, 222. So, a secure and reproduceable positioning of the samples 300 is guaranteed.
  • the X-ray scanning pro ⁇ cedure is done.
  • a number, for example fourteen, of sample holders 100 is equipped with samples 300. These sample holders 100 can be tested in the sys ⁇ tem 1000 one after another. Thereby reducing the operator setup time signifi ⁇ cantly.
  • sample holder 100 By means of the afore-mentioned sample holder 100 it is possible to accurately and repeatably fix one or more samples 300, in particular IC packages, for X-ray imaging such that the sample 300 or the samples 300 remain securely held with ⁇ out movement in the presence of radiation 502.
  • the placement of the sample 300 or the samples 300 does not significantly vary in the three spatial directions x, y, z between different sample holders 100 or repeated uses on the same sample holder 100.
  • the sample holder 100 allows for the efficiency of repetitive X-ray CT imaging of like samples 300, optimized for maximum throughput, ease of use, and without altering the physical sample 300.
  • the sample holder 100 thus enables automa ⁇ tion of the X-ray CT imaging workflow.
  • the sample holder 100 supports high- resolution imaging amidst the exposure to radiation 502, in particular X-rays, for the duration of 3D tomographies. Due to the materials used for the sample holder 100 and the fixing element 400, insignificant degradation of the sample holder 100 and its components over time is to be expected.
  • the sample holder 100 is ad ⁇ vantageously suitable for holding samples 300 vertically.
  • the fixing element 400 allows a user to exert an adequate holding force between the sample 300 and the sample receptacle 200.
  • the radiation-resistance material being used for the fixing element 400 enables longevity and stability to accommodate high-resolution X-ray imaging.
  • EPDM rubber is a suitable material for the fixing element 400.
  • the sample holder 100 enables accurate and repeatable positioning of samples 300 on the sample holder 100, wherein the positioning is done by the alignment portions 220, 222. With the sample holder 100 it is possible to accommodate one or more samples 300 per sample holder 100.
  • the sample holder 100 is designed for re ⁇ peatable sample mounting accuracy on the sample holder 100, in particular for sample-to-sample, holder-to-holder and holder-to-system.
  • the sample holder 100 is optimized for maximum X-ray imaging throughput.
  • the sample holder 100 does not damage or modify the sample 300 to be held and scanned.
  • the sample holder 100 is preferably com ⁇ pletely made of non-magnetic materials. Thus, the sample holder 100 does not affect the X-rays.
  • a thermallystable material is used for the sample holder 100. The material coef ⁇ ficient of thermal expansion accommodates highest resolution scans.
  • the key 138 enables accurate and repeatable assembly of the sample holder 100. The key 138 ensures that the sample 300 maintains a repeatable angular orientation in the X- ray beam path.
  • the sample holder 100 can be shape-optimized to optimize X-ray transmission.
  • Registration features so called fiducials
  • Unique identifiers for example barcodes
  • laser-engraved identifiers can be used.
  • the sample holder 100 has a scalable design which can be easily customized for each new sample geometry.
  • a CAD model of the sample holder 100 may be used as input for collision avoidance guidance on the instrument.
  • the sample holder 100 can be packaged with a 3D printer and a design template library.
  • the scala ⁇ ble design allows one to create a new design quickly and with minimal effort to optimize for fast X-ray imaging of samples 300 with slightly different geometry.
  • Fig. 8 shows a block diagram of one embodiment of a method for performing an X-ray imaging process using the sample holder 100.
  • the X-ray imaging process is a repetitive 3D imaging and/or measurement process.
  • a method step Si the sample 300 is placed on the sample holder 100 as mentioned before.
  • a plurality of samples 300 can be attached to the sample holder 100 by means of a plurality of fixing elements 400.
  • a method step S2 radiation 502 is emitted by means of the radiation source 500.
  • radiation 504 passed through the sample 300 is received by means of the radiation detector 600.
  • the method steps Si to S3 can be performed all at the same time or one after an ⁇ other.
  • the sample holder 100 with the sample 300 or the samples 300 is rotated stepwise into a plurality of posi ⁇ tions. In each position, at least one X-ray image is taken. All the gathered X-ray images together form a three-dimensional data set of the sample 300, in particu- lar of a region of interest of the sample 300.

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Abstract

A sample holder for holding a sample during an X-ray imaging process, the sample holder comprising a sample placement surface on which the sample is placed for positioning the sample in a depth direction of the sample holder, a first alignment portion for aligning the sample in a width direction of the sample holder, and a second alignment portion for aligning the sample in a height direction of the sample holder.

Description

SAMPLE HOLDER, SYSTEM AND METHOD
The present disclosure relates to a sample holder for holding a sample during an X-ray imaging process, to a system comprising such a sample holder and to a method for performing an X-ray imaging process using such a sample holder.
This application incorporates by reference in its entirety commonly owned U.S. Provisional Patent Application Serial Number 62/821,090, entitled "Method for imaging a region of interest of a sample using a tomographic X-ray microscope, microscope, system and computer program" and filed on March 20, 2019.
3D X-ray imaging techniques such as X-ray microscopy (XRM) and microCT have become established failure analysis (FA) tools for bridging fault isolation and physical failure analysis (PFA), because they enable the visualization of defects without having to destroy the device under test. Furthermore, these tools provide FA analysts with better information for determining the best approach to conduct PFA for root cause analysis. The XRM advantages of non-destructive, high- resolution imaging make it an excellent option for routine inspection of semicon¬ ductor package features such as traces, C4 bumps, and micro-bumps. MicroCT is also valuable, although its resolution when applied to larger sample geometries is lower than the resolution that can be achieved with XRM. Since XRM and mi¬ croCT share significant similarities, the terms will be used interchangeably in the rest of the document.
XRM set-up and acquisition times have limited its proliferation and adoption be¬ yond FA and manual measurement applications. XRM workflow improvements offer the opportunity to realize the efficiency and throughput benefits of auto¬ mated device handling for productivity in high-resolution, site-specific inspection and measurement applications.
For performing XRM, there is a need to accurately and repeatably fix one or more samples, for example integrated circuit (IC) packages, to a sample holder such that the sample remains securely held without movement in the presence of X- ray radiation. It is indispensable that the sample’s placement on the sample holder does not significantly vary in all three spatial dimensions between differ¬ ent sample holders or repeated uses on the same sample holder.
Against this background, it is one object of the present disclosure to provide an improved sample holder.
Accordingly, a sample holder for holding a sample during an X-ray imaging pro cess is provided. The sample holder comprises a sample placement surface on which the sample is placed for positioning the sample in a depth direction of the sample holder, a first alignment portion for aligning the sample in a width direc¬ tion of the sample holder, and a second alignment portion for aligning the sample in a height direction of the sample holder.
Due to the fact that the sample holder has the sample placement surface and the two alignment portions, it is possible to accurately and repeatably position the sample in all three spatial directions. Hence, the sample remains securely held without movement in the presence of X-ray radiation. The placement of the sam¬ ple does not significantly vary in the three spatial directions between different sample holders or repeated uses on the same sample holder.
The X-ray imaging process preferably is XRM. The sample can be an electronic device, in particular an IC package. The sample placement surface is preferably a flat surface of the sample holder on which the sample can be placed. The align¬ ment portions are preferably bar-shaped and are arranged on two different edges of the sample placement surface. The sample placement surface preferably is rec¬ tangular. The sample placement surface can easily be adapted to different sizes of the sample. The sample placement surface in particular is a plane that is de¬ fined by the width direction and the height direction. The first alignment portion runs along the height direction. The second align¬ ment portion runs along the width direction. The first alignment portion can be named vertical ledge. The second alignment portion can be named horizontal ledge. In use of the sample holder, a first edge of the sample abuts the first alignment portion and a second edge of the sample abuts the second alignment portion. The sample is therefore guided by the alignment portions into a corner of a sample receiving section of the sample holder. In a front view of the sample placement surface, the corner is a right bottom corner of the sample receiving section. The alignment portions can also serve as X-ray alignment marks, in par¬ ticular as so-called fiducials.
The sample holder preferably has a coordinate system with a first spatial direc¬ tion or x-direction, a second spatial direction or ydirection and a third spatial direction or z-direction. The spatial directions are arranged perpendicular to each other. The z-direction has to be understood as the depth direction. The x-direction has to be understood as the width direction. The ydirection has to be understood as the height direction.
The sample can be positioned on the sample holder as follows. In a first step, the sample is placed on the sample placement surface for positioning the sample in the depth direction of the sample holder. In a second step, the sample is abutted on the first alignment portion for aligning the sample in the width direction of the sample holder. In a third step, the sample is abutted on the second alignment portion for aligning the sample in the height direction of the sample holder. The afore-mentioned steps can be performed at the same time or one after another. The third step can be performed after the second step or vice versa.
According to an embodiment, the first alignment portion is arranged perpendicu¬ lar to the sample placement surface, wherein the second alignment portion is ar¬ ranged perpendicular to the sample placement surface and perpendicular to the first alignment portion. The sample placement surface, the first alignment portion and the second align¬ ment portion in this way form the box-shaped sample receiving section which re ceives and aligns the sample in all three spatial directions. Preferably, the sam¬ ple receiving section is open on two sides, whereas two other sides are closed by the alignment portions that work as side walls of the sample receiving section.
According to a further embodiment, a cut-out is placed at an intersection of the first alignment portion and the second alignment portion.
Preferably, the cut-out is circular. The cut-out can be a bore that is placed at the intersection of the two alignment portions. The cut-out receives a corner of the sample.
According to a further embodiment, the sample holder further comprises a fixing element for pressing the sample against the sample placement surface, against the first alignment portion and against the second alignment portion.
The fixing element allows a user to exert an adequate holding force between the sample and the sample holder. When using the sample holder, time is saved by the quick-assembly, quick-release of the samples by means of the fixing element. No cleaning of the samples and/or the sample holder is needed since no adhesive is used to fix the sample to the sample holder. The fixing element can be used several times.
According to a further embodiment, the fixing element runs diagonally over the sample placement surface.
"Diagonally" means that the fixing element runs between two transversely oppo¬ site corners of the sample placement surface. Hence, the fixing element also runs diagonally over the sample thus fixing it securely to the sample holder. According to a further embodiment, the fixing element is made of a flexible and radiation-stable material, in particular of ethylene propylene diene methylene rubber.
The fixing element is therefore flexible or elastic. In other words, the fixing ele¬ ment can be stretched. The fixing element can be named elastic fixing element. The fixing element can be an Oring.
According to a further embodiment, the sample holder further comprises a first hook portion and a second hook portion, wherein the fixing element is hooked into the first hook portion and into the second hook portion.
The first hook portion and the second hook portion are preferably arranged at two opposite corners of the sample placement surface.
According to a further embodiment, the sample placement surface is arranged between the first hook portion and the second hook portion.
The hook portions are arranged diagonally so that the fixing element runs diago¬ nally over the sample and fixes it to the sample holder.
According to a further embodiment, the sample holder further comprises a rear surface which is arranged opposite the sample placement surface, wherein the first hook portion has a first notch which is provided in the rear surface for re¬ ceiving the fixing element, and wherein the second hook portion has a second notch which is provided in the rear surface for receiving the fixing element.
In this way, a good hold of the fixing element is ensured. The fixing element is thus prevented from slipping off the hook portions. According to a further embodiment, the first hook portion is arranged flush with the sample placement surface, wherein the second hook portion protrudes from the sample placement surface in the depth direction.
This has the effect that the fixing element runs inclined with regard to the sam¬ ple placement surface. This ensures that the sample is securely pressed against the sample placement surface as well as against the alignment portions. "Flush" means that the first hook portion does not protrude over the sample placement surface.
According to a further embodiment, the sample holder further comprises a sam¬ ple receptacle which has a plurality of sample receiving sections, wherein each sample receiving section has a sample placement surface, a first alignment por¬ tion and a second alignment portion.
The number of sample receiving sections is arbitrary. For example, there are provided three sample receiving sections. Each sample receiving section is capa¬ ble of receiving one sample. Each sample receiving section has a fixing element. When regarded along the height direction, the sample receiving sections are ar¬ ranged in a row.
According to a further embodiment, the sample receptacle is integrally formed.
The phrase "integrally formed" refers to a structure formed from the same mate¬ rial or materials using a single, continuous process. For example, when the sam¬ ple receptacle is formed using a three-dimensional printer, the three-dimensional printer can emit the same material or materials during the printing process to form the sample receptacle as a single piece. The sample receptacle is preferably made of a material that allows the radiation to readily pass through the sample receptacle. The materials used for producing the sample receptacle can include aluminum, glassy carbon, epoxy filled with glass fiber or other low-attenuating and structurally-stable materials. According to a further embodiment, the sample holder further comprises a post to which the sample receptacle is attached and a gripper disc to which the post is attached, wherein the post is fixed to the gripper disc in a form-locking manner by means of a key connection.
The post can be made of aluminum or any other suited material. The post prefer¬ ably has a circular cross-section. The sample receptacle can be attached to the post by means of fixing elements like screws. Additionally, a pin connection be¬ tween the sample receptacle and the post can be provided. The pin connection comprises an alignment pin and two bores for receiving the alignment pin. One bore is provided at the sample receptacle and one bore is provided at the post. The gripper disc is suitable for being gripped by a gripper or robot. The gripper disc has a central bore which receives an end of the post. The sample holder fur¬ ther comprises a base plate to which the gripper disc is attached. A "form locking" connection can be created by two elements engaging and blocking each other. The post can have a keyway for receiving a key, in particular a woodruff key. The cen¬ tral bore of the gripper disc has a notch for receiving the key. The key connection securely prevents the post from rotating relative to the gripper disc.
Furthermore, a system for performing an X-ray imaging process is provided. The system comprises a radiation source that emits radiation, a radiation detector that receives the radiation emitted from the radiation source, and at least one sample holder as explained before, wherein the sample holder is arranged be¬ tween the radiation source and the radiation detector.
The system is preferably an XRM system. The System can have a plurality of sample holders. Each sample holder can hold a plurality of samples. The sample holder holds at least one sample. In particular, the radiation detector receives or detects radiation that passed through the sample and the sample holder. Further, a method for performing an X-ray imaging process using such a sample holder is provided. The method comprises the following method steps: a) placing the sample on the sample holder, b) emitting radiation by means of a radiation source, and c) receiving radiation passed through the sample by means of a radi¬ ation detector.
In particular, the radiation also passes through the sample holder. The method steps a) to c) can be performed all at the same time or one after another. During performing the X-ray imaging process, the sample holder with the sample or the samples is preferably rotated stepwise into a plurality of positions. In each posi¬ tion, at least one X-ray image is taken. All the gathered X-ray images together form a three-dimensional data set of the sample, in particular of a region of in¬ terest of the sample.
The features disclosed for the sample holder are applicable to the system as well as to the method and vice versa.
Further possible implementations or alternative solutions of the disclosure also encompass combinations - that are not explicitly mentioned herein - of features described above or below with regard to the embodiments. The person skilled in the art may also add individual or isolated aspects and features to the most basic form of the disclosure.
Further embodiments, features and advantages of the present disclosure will be¬ come apparent from the subsequent description and dependent claims, taken in conjunction with the accompanying drawings, in which:
Fig. 1 shows a schematic perspective view of one embodiment of a sample holder;
Fig. 2 shows a schematic exploded view of the sample holder according to Fig. V, Fig. 3 shows a schematic cross-sectional view of the sample holder according to Fig. i;
Fig. 4 shows a schematic perspective view of one embodiment of a sample recep¬ tacle for the sample holder according to Fig. V,
Fig. 5 shows a schematic front view of the sample receptacle according to Fig. 4;
Fig. 6 shows a schematic rear view of the sample receptacle according to Fig. 4;
Fig. 7 shows a schematic cross-sectional view of the sample receptacle according to the intersection line VII -VII of Fig. 5; and
Fig. 8 shows a schematic block diagram of one embodiment of a method for per¬ forming an X-ray imaging process using the sample holder according to Fig. 1.
In the Figures, like reference numerals designate like or functionally equivalent elements, unless otherwise indicated.
Fig. 1 shows a schematic perspective view of one embodiment of a sample holder 100 for holding samples (not shown) during X-ray imaging, in particular X-ray CT imaging, of the samples. Fig. 2 shows an exploded view of the sample holder 100. Fig. 3 shows a cross-sectional view of the sample holder 100. In the follow¬ ing, Figs. 1 to 3 are referred to at the same time.
In particular, the sample holder 100 is used for high-resolution 3D X-ray micros¬ copy (XRM) of semiconductor package interconnects. The sample holder 100 has a base plate 102. The base plate 102 has a flattened cylindrical shape and is pro¬ vided with a lateral flattening 104. The base plate 102 further has an upper side 106 and a lower side 108. The sides 106, 108 are arranged parallel to each other. The base plate 102 has a stepped bore 110 which is arranged centrally in the base plate 102. The bore 110 breaks through the base plate 102. Further stepped bores 112 are provided in the base plate 102. The number of bores 112 is arbi¬ trary. For example, there are provided three bores 112.
Fixing elements 114, 116 are encompassed in the bores 110, 112. The fixing ele¬ ments 114, 116 can be screws. The lower side 108 is placed on a stage (not shown). The stage can laterally move the sample holder 100 in a first spatial di¬ rection or x-direction x, a second spatial direction or ydirection y and a third spa tial direction or z-direction z. In the following, the x-direction x is named width direction of the sample holder 100, the ydirection y is named height direction of the sample holder 100 and the z-direction z is named depth direction of the sam ple holder 100. The stage can also rotate the sample holder 100 around the height direction y. The base plate 102 is preferably made of metal. The base plate 102 can be made of aluminum, steel or other suitable materials.
The sample holder 100 further comprises a gripper disc 118. The gripper disc 118 has a flat cylindrical shape with an upper side 120 and a lower side 122. The sides 120, 122 are arranged parallel to each other. The lower side 122 is placed on the upper side 106 of the base plate 102. The gripper disc 118 is laterally flat¬ tened on two sides. One of the sides has a notch 124, whereas the other side has a conical bore 126. The notch 124 and the bore 126 can be used to grip the sample holder 100 by means of a gripping robot (not shown).
The gripper disc 118 has a number of threaded bores 128 into which the fixing elements 116 are screwed to fix the gripper disc 118 to the base plate 102. The bores 128 can break through the gripper disc 118. The gripper disc 118 comprises a central bore 130 which breaks through the gripper disc 118. The bore 130 is provided with a notch 132 which runs in the height direction y. The gripper disc 118 is made of metal. Preferably, the gripper disc 118 is made of aluminum. The gripper disc 118 can also be made of steel or other suitable materials.
A post 134 is received in the bore 130. The post 134 has a keyway 136 which re¬ ceives a key 138. The key 138 is a woodruff key. The key 138 engages with the notch 132 of the gripper disc 118 and prevents the post 134 from rotating rela¬ tively towards the gripper disc 118. The post 134 is fixed to the base plate 102 by means of the fixing element 114 which is screwed into a central bore 140 of the post 134. Instead of the woodruff key 138, other keys can also be used.
The post 134 is preferably made of metal. The post 134 can be made of alumi¬ num. Opposite the keyway 136, the post 134 has a lateral flattening 142 with two threaded bores 144, 146. The bores 144, 146 receive fixing elements 148, 150. The fixing elements 148, 150 can be screws. Between the bores 144, 146 a further bore 152 is arranged. The bore 152 receives an alignment dowel or alignment pin 154. The sample holder 100 has a source side 156 which faces a radiation source 500, in particular an X-ray source, and a detector side 158 which faces a radia¬ tion detector 600, in particular an X-ray detector. The radiation source 500 emits radiation 502, in particular X-rays. The radiation detector 602 detects radiation 504 passed through the sample holder 100 and the sample placed in the sample holder 100. The sample holder 100, the radiation source 500 and the radiation detector 600 are part of a system 1000 for performing an X-ray imaging process, in particular an XRM process. The system 1000 is an XRM system or an X-ray CT system.
The sample holder 100 comprises a sample receptacle 200 which is fixed to the post 134 by means of the alignment pin 154 and the fixing elements 148, 150.
The sample receptacle 200 is shown in different views in Figs. 4 to 7. In the fol¬ lowing, Figs. 4 to 7 are referred to at the same time.
The sample receptacle 200 is made of a material that allows the radiation 502 to readily pass through the sample receptacle 200. For example, the sample recep¬ tacle 200 may be formed from a polymeric material such as plastic. In this re¬ gard, the sample receptacle 200 may be formed using a three-dimensional print¬ ing apparatus ("3D printer") allowing the sample receptacle 200 to include a va¬ riety of customizable sizes and shapes to carry a variety of samples. A "three- dimension printer" refers to a printing apparatus that emits a polymeric material in order to form a three-dimensional structure.
However, the sample receptacle 200 may be formed by other methods. For exam¬ ple, the sample receptacle 200 may include a polymeric material which is injec¬ tion molded into a mold cavity that defines the size and shape of the sample re¬ ceptacle 200. Further, the sample receptacle 200 may be formed from a block of polymeric or metal material that undergoes a material removal process. The ma¬ terials used for producing the sample receptacle 200 can include aluminum, glassy carbon, epoxy filled with glass fiber or other low-attenuating and structur- allystable materials.
The sample receptacle 200 is preferably integrally formed. The sample receptacle 200 is bar-shaped and has a base portion 202 which is fixed to the post 134. The base portion 202 has two stepped bores 204, 206 for receiving the fixing elements 148, 150 and one bore 208 for receiving the alignment pin 154. The alignment pin 154 is used for exactly positioning the sample receptacle 200 at the post 134. The fixing elements 148, 150 are used for attaching the sample receptacle 200 to the post 134.
The sample receptacle 200 comprises a number of sample receiving sections 210, 212, 214. The number of sample receiving sections 210, 212, 214 is arbitrary. For example, there are provided three sample receiving sections 210, 212, 214. The sample receptacle 200 may accommodate more or less sample receiving sections 210, 212, 214, depending on the scanning range of the system 1000. Each sample receiving sections 210, 212, 214 is capable of receiving one sample 300 (see Fig.
5). The sample 300 can be an electronic device like an integrated circuit. The sample receiving sections 210, 212, 214 are arranged in a row when being viewed in the height direction y. The sample receiving sections 210, 212, 214 are at¬ tached to each other. The sample receiving sections 210, 212, 214 are integrally formed. All sample receiving sections 210, 212, 214 have the same technical fea- tures. For this reason, in the following only the sample receiving sections 214 is referred to.
The sample receiving section 214 is generally plate shaped and has a sample placement surface 216 and a rear surface 218. In use of the sample holder 100, the sample placement surface 216 is oriented towards the radiation detector 600 and the rear surface 218 is oriented towards the radiation source 500. The sam¬ ple 300 is placed on the sample placement surface 216. The sample receiving sec¬ tion 214 has a first alignment portion 220 and a second alignment portion 222. When placing the sample 300 on the sample placement surface 216, the sample 300 can be positioned in the depth direction z. However, the sample holder 100 can be placed such that the sample placement surface 216 faces the radiation source 500 and the rear surface 218 faces the radiation detector 600. So, the sample 300 can be positioned to face the radiation detector 600 or to face the ra¬ diation source 500.
The first alignment portion 220 runs along the height direction y and is capable of positioning the sample 300 in the width direction x. The first alignment por¬ tion 220 is a vertical ledge or can be named vertical ledge. The second alignment portion 222 runs along the width direction x and is capable of positioning the sample 300 in the height direction y. The second alignment portion 222 is a hori¬ zontal ledge or can be named horizontal ledge. The alignment portions 220, 222 are arranged perpendicular to each other. The alignment portions 220, 222 can also serve as X-ray alignment marks, in particular as so-called fiducials.
The sample 300 can have four lateral edges 302, 304, 306, 308. When placing the sample 300 on the sample placement surface 216, two of the edges 306, 308 of the sample 300 are guided along the first alignment portion 220 and the second alignment portion 222 till the sample 300 is positioned in a bottom right corner (see Fig. 5) of the sample receiving section 214. Hence, by means of the sample placement surface 216 and the two alignment portions 220, 222, the sample re¬ ceiving section 214 is capable of positioning the sample 300 in all three spatial directions x, y, z. Other alignment portions can be used such that the origin of the sample 300 is elsewhere than the bottom right corner of the sample receiving section 214.
A circular cut-out 224 is arranged where the alignment portions 220, 222 inter¬ sect. The cut-out 224 receives a corner of the sample 300. The sample placement surface 216 can be bordered by an upper edge 226. The sample receiving section 210 does not have such an upper edge 226. A circular cut-out 228 is provided where the upper edge 226 and the first alignment portion 220 intersect each oth¬ er.
The sample receiving section 214 further comprises a first hook portion 230 and a second hook portion 232 which are arranged diagonally. On the rear surface 218, each hook portion 230, 232 has a notch 234, 236. The first hook portion 230 has a first notch 234. The second hook portion 232 has a second notch 236. The hook portions 230, 232 are capable of receiving an elastic fixing element 400 (see Fig.
5). The second hook portion 232 is arranged between two notches 238, 240 that break through the alignment portions 220, 222. The fixing element 400 runs through the notches 238, 240. By means of the fixing element 400, the sample 300 can be pressed against the sample placement surface 216 and against the alignment portions 220, 222.
On the rear surface 218, the fixing element 400 runs through the notches 234, 236. The fixing element 400 can be an O-ring. The fixing element 400 is made of a flexible and radiation-stable material. For example, the fixing element 400 can be made of ethylene propylene diene methylene rubber (EPDM). By means of the fixing element 400, the sample 300 can be easily fixed to the sample holder 100 in a non-permanent way. The fixing element 400 imparts a securing force to mate the sample 300 against the sample placement surface 216 and the alignment por¬ tions 220, 222. The function of the sample holder 100 is as follows. In a first step, the sample 300 is placed on the sample placement surface 216 for positioning the sample 300 in the depth direction z of the sample holder 100. In a second step, the sample 300 is abutted on the first alignment portion 220 for aligning the sample 300 in the width direction x of the sample holder 100. In a third step, the sample 300 is abutted on the second alignment portion 222 for aligning the sample 300 in the height direction y of the sample holder 100. The third step can be performed after the second step or vice versa. The afore mentioned steps can be performed at the same time or one after another. In particular, the last two steps can be performed by applying the fixing element 400. In other words, the fixing element 400 press¬ es the sample 300 against the alignment portions 200, 222. Alternatively, the fix¬ ing element 400 can be applied after performing aligning the sample 300.
On each sample receiving section 210, 212, 214 a sample 300 is placed. The sam¬ ples 300 are aligned on the sample placement surface 216 of each sample receiv¬ ing section 210, 212, 214 by means of the alignment portions 220, 222. Before or after aligning the samples 300, fixing elements 400 are hooked into the hook por¬ tions 230, 232 of each sample receiving section 210, 212, 214. The fixing elements 400 press the samples 300 against the sample placement surface 216 and the alignment portions 220, 222. So, a secure and reproduceable positioning of the samples 300 is guaranteed. After fixing the samples 300, the X-ray scanning pro¬ cedure is done. Preferably, a number, for example fourteen, of sample holders 100 is equipped with samples 300. These sample holders 100 can be tested in the sys¬ tem 1000 one after another. Thereby reducing the operator setup time signifi¬ cantly.
By means of the afore-mentioned sample holder 100 it is possible to accurately and repeatably fix one or more samples 300, in particular IC packages, for X-ray imaging such that the sample 300 or the samples 300 remain securely held with¬ out movement in the presence of radiation 502. The placement of the sample 300 or the samples 300 does not significantly vary in the three spatial directions x, y, z between different sample holders 100 or repeated uses on the same sample holder 100.
The sample holder 100 allows for the efficiency of repetitive X-ray CT imaging of like samples 300, optimized for maximum throughput, ease of use, and without altering the physical sample 300. The sample holder 100 thus enables automa¬ tion of the X-ray CT imaging workflow. The sample holder 100 supports high- resolution imaging amidst the exposure to radiation 502, in particular X-rays, for the duration of 3D tomographies. Due to the materials used for the sample holder 100 and the fixing element 400, insignificant degradation of the sample holder 100 and its components over time is to be expected. The sample holder 100 is ad¬ vantageously suitable for holding samples 300 vertically. The fixing element 400 allows a user to exert an adequate holding force between the sample 300 and the sample receptacle 200.
The radiation-resistance material being used for the fixing element 400 enables longevity and stability to accommodate high-resolution X-ray imaging. As men¬ tioned before, EPDM rubber is a suitable material for the fixing element 400. The sample holder 100 enables accurate and repeatable positioning of samples 300 on the sample holder 100, wherein the positioning is done by the alignment portions 220, 222. With the sample holder 100 it is possible to accommodate one or more samples 300 per sample holder 100. The sample holder 100 is designed for re¬ peatable sample mounting accuracy on the sample holder 100, in particular for sample-to-sample, holder-to-holder and holder-to-system.
Tools for fixing the samples 300 are not necessary. This eases the installation.
The sample holder 100 is optimized for maximum X-ray imaging throughput.
This is done by using low attenuation materials and a minimal profile depth of the sample receptacle 200. The sample holder 100 does not damage or modify the sample 300 to be held and scanned. The sample holder 100 is preferably com¬ pletely made of non-magnetic materials. Thus, the sample holder 100 does not affect the X-rays. A thermallystable material is used for the sample holder 100. The material coef¬ ficient of thermal expansion accommodates highest resolution scans. The key 138 enables accurate and repeatable assembly of the sample holder 100. The key 138 ensures that the sample 300 maintains a repeatable angular orientation in the X- ray beam path. The sample holder 100 can be shape-optimized to optimize X-ray transmission. This can be done by using cut-outs. Registration features, so called fiducials, may be added to the sample holder 100 for alignment thereof. Unique identifiers, for example barcodes, may be added for auto-recognition of the sam¬ ple holder 100 and the samples 300. Also, laser-engraved identifiers can be used.
The sample holder 100 has a scalable design which can be easily customized for each new sample geometry. A CAD model of the sample holder 100 may be used as input for collision avoidance guidance on the instrument. The sample holder 100 can be packaged with a 3D printer and a design template library. The scala¬ ble design allows one to create a new design quickly and with minimal effort to optimize for fast X-ray imaging of samples 300 with slightly different geometry.
When using the sample holder 100, time is saved by the quick-assembly, quick- release of the samples 300. No cleaning of the samples 300 and/or the sample holder 100 is needed since no adhesives are used. Locating regions of interest on the samples 300 for X-ray imaging is easier, since the samples 300 are placed in a repeatable position on the sample holder 100. This position is defined by the de¬ sign of the sample receptacle 200. Manual alignment steps of the samples 300 can be replaced by automation. A higher yield in imaging can be achieved be cause due to the exact positioning of the samples 300, it is less likely to have a failed scan and a need to re-image. Built-in features of the sample holder 100 like the alignment portions 220, 222 may be used as fiducial marks for alignment in the automation recipe. This improves the X-ray scan positional accuracy for all samples 300, saving the time and labor of re-scanning or placement of manual fiducial marks. Fig. 8 shows a block diagram of one embodiment of a method for performing an X-ray imaging process using the sample holder 100. The X-ray imaging process is a repetitive 3D imaging and/or measurement process. In a method step Si, the sample 300 is placed on the sample holder 100 as mentioned before. A plurality of samples 300 can be attached to the sample holder 100 by means of a plurality of fixing elements 400. In a method step S2, radiation 502 is emitted by means of the radiation source 500. In a method step S3, radiation 504 passed through the sample 300 is received by means of the radiation detector 600. The method steps Si to S3 can be performed all at the same time or one after an¬ other. During performing the X-ray imaging process, the sample holder 100 with the sample 300 or the samples 300 is rotated stepwise into a plurality of posi¬ tions. In each position, at least one X-ray image is taken. All the gathered X-ray images together form a three-dimensional data set of the sample 300, in particu- lar of a region of interest of the sample 300.
Although the present disclosure has been described in accordance with preferred embodiments, it is obvious for the person skilled in the art that modifications are possible in all embodiments.

Claims

WHAT IS CLAIMED IS:
1. A sample holder for holding a sample during an X-ray imaging process, the sample holder comprising
a sample placement surface on which the sample is placed for positioning the sample in a depth direction of the sample holder,
a first alignment portion for aligning the sample in a width direction of the sample holder, and
a second alignment portion for aligning the sample in a height direction of the sample holder.
2. The sample holder according to claim 1, wherein the first alignment portion is arranged perpendicular to the sample placement surface, and wherein the sec¬ ond alignment portion is arranged perpendicular to the sample placement sur¬ face and perpendicular to the first alignment portion.
3. The sample holder according to claim 1, wherein a cut-out is placed at an intersection of the first alignment portion and the second alignment portion.
4. The sample holder according to claim 1, further comprising a fixing element for pressing the sample against the sample placement surface, against the first alignment portion and against the second alignment portion.
5. The sample holder according to claim 4, wherein the fixing element runs diagonally over the sample placement surface.
6. The sample holder according to claim 4, wherein the fixing element is made of a flexible and radiation-stable material, in particular of ethylene propylene diene methylene rubber.
7. The sample holder according to claim 4, further comprising a first hook por¬ tion and a second hook portion, wherein the fixing element is hooked into the first hook portion and into the second hook portion.
8. The sample holder according to claim 7, wherein the sample placement sur¬ face is arranged between the first hook portion and the second hook portion.
9. The sample holder according to claim 7, further comprising a rear surface which is arranged opposite the sample placement surface, wherein the first hook portion has a first notch which is provided in the rear surface for receiving the fixing element, and wherein the second hook portion has a second notch which is provided in the rear surface for receiving the fixing element.
10. The sample holder according to claim 7, wherein the first hook portion is arranged flush with the sample placement surface, and wherein the second hook portion protrudes from the sample placement surface in the depth direction.
11. The sample holder according to claim 1, further comprising a sample recep¬ tacle which has a plurality of sample receiving sections, wherein each sample re¬ ceiving section has a sample placement surface, a first alignment portion and a second alignment portion.
12. The sample holder according to claim 11, wherein the sample receptacle is integrally formed.
13. The sample holder according to claim 11, further comprising a post to which the sample receptacle is attached and a gripper disc to which the post is attached, wherein the post is fixed to the gripper disc in a form-locking manner by means of a key connection.
14. A system for performing an X-ray imaging process, the system comprising a radiation source that emits radiation, a radiation detector that receives the radiation emitted from the radiation source, and
at least one sample holder according to claim 1,
wherein the sample holder is arranged between the radiation source and the radiation detector.
15. A method for performing an X-ray imaging process using a sample holder according to claim 1, the method comprising the following method steps:
a) placing the sample on the sample holder,
b) emitting radiation by means of a radiation source, and
c) receiving radiation passed through the sample by means of a radiation detector.
PCT/US2020/023108 2019-03-20 2020-03-17 Sample holder, system and method WO2020190919A1 (en)

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Citations (2)

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US20140064445A1 (en) * 2012-09-05 2014-03-06 David Lewis Adler High speed x-ray inspection microscope
US9557282B1 (en) * 2013-06-17 2017-01-31 U.S. Department Of Energy High precision detector robot arm system

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JP2986556B2 (en) * 1991-01-21 1999-12-06 株式会社マック・サイエンス Sample positioning mechanism
EP1720006A1 (en) * 2005-05-02 2006-11-08 F. Hoffmann-La Roche Ag Method and apparatus for x-ray diffraction analysis
EP3101406B1 (en) * 2015-06-05 2022-12-07 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Method for preparing a sample for the microstructure diagnosis and sample for micro structure diagnosis
EP3432338B1 (en) * 2017-07-20 2019-10-23 FEI Company Specimen preparation and inspection in a dual-beam charged particle microscope

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US20140064445A1 (en) * 2012-09-05 2014-03-06 David Lewis Adler High speed x-ray inspection microscope
US9557282B1 (en) * 2013-06-17 2017-01-31 U.S. Department Of Energy High precision detector robot arm system

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CN113785192A (en) 2021-12-10
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KR20210141595A (en) 2021-11-23

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