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WO2015125134A1 - A method and apparatus for internal marking of ingots and wafers - Google Patents

A method and apparatus for internal marking of ingots and wafers Download PDF

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Publication number
WO2015125134A1
WO2015125134A1 PCT/IL2015/050168 IL2015050168W WO2015125134A1 WO 2015125134 A1 WO2015125134 A1 WO 2015125134A1 IL 2015050168 W IL2015050168 W IL 2015050168W WO 2015125134 A1 WO2015125134 A1 WO 2015125134A1
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WO
WIPO (PCT)
Prior art keywords
single crystal
orientation
wafer
mark
silicon
Prior art date
Application number
PCT/IL2015/050168
Other languages
French (fr)
Inventor
Moshe Finarov
Ehud Tirosh
Giora Dishon
Alexander GUSAROV
Original Assignee
Gem Solar Ltd.
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 Gem Solar Ltd. filed Critical Gem Solar Ltd.
Publication of WO2015125134A1 publication Critical patent/WO2015125134A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/544—Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/544—Marks applied to semiconductor devices or parts
    • H01L2223/54406—Marks applied to semiconductor devices or parts comprising alphanumeric information
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/544—Marks applied to semiconductor devices or parts
    • H01L2223/54413—Marks applied to semiconductor devices or parts comprising digital information, e.g. bar codes, data matrix
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/544—Marks applied to semiconductor devices or parts
    • H01L2223/5442—Marks applied to semiconductor devices or parts comprising non digital, non alphanumeric information, e.g. symbols
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/544—Marks applied to semiconductor devices or parts
    • H01L2223/54426—Marks applied to semiconductor devices or parts for alignment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/544—Marks applied to semiconductor devices or parts
    • H01L2223/54433—Marks applied to semiconductor devices or parts containing identification or tracking information
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/544—Marks applied to semiconductor devices or parts
    • H01L2223/54453—Marks applied to semiconductor devices or parts for use prior to dicing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/544—Marks applied to semiconductor devices or parts
    • H01L2223/54493—Peripheral marks on wafers, e.g. orientation flats, notches, lot number
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

  • the present invention relates to a field of marking single crystals in general and particularly of marking single-crystalline semiconductor silicon ingots and wafers.
  • Wafers are grown from crystal ingots having a regular crystal structure. When ingots are cut into wafers, the surface is aligned in one of several relative directions known as crystal orientations. Crystal orientation is defined by the Miller index with [100] or [111] faces being the most common for silicon.
  • Wafers are used for semiconductor chip manufacturing and wafer processing and properties are dependent on the orientation of their crystallographic planes orientation. Wafers are usually marked to indicate their pre-defined crystallographic orientation. The marking could alsoindicate wafer serial number, chip ID and alike.
  • Marks or fiducial marks occupy on the wafer certain area that could be used to increase yield of manufactured components.
  • orientation marks such as flats and notches and replace them by marking at the wafer backside. Marking at the back side would avoid loss of wafer area at the notch/flat area and also to eliminate stresses due to the irregularity introduced by the presence of aflat/notch.
  • backside marking There is still an issue associated with backside marking, namely, the survivability in terms of visibility of these marks during and after the processing steps, for example etching, that the wafer undergoes. Also, backside marks may be source of contamination which may be detrimental to chip manufacturing yield. There is, therefore, a need to introduce a method for creation of the marks which will still be visible and useful and contamination-free, regardless of the wafer processing steps.
  • Japanese Patent application JP2001080297 describes a method for the creation of graphic characters inside silicon bulk using a laser at a wavelength between 0.3 ⁇ and 1.1 ⁇ and beam conversion angle of 5° to 20°.
  • US patent 4,534,804 describes a method for scribing alignment marks using a laser beam on the back side of a lightly doped substrate of a silicon wafer containing a heavily doped internal layer.
  • the wavelength of the laser beam is chosen such that it passes through the lightly doped substrate without absorption but is absorbed in the heavily doped internal layer to produce therein a defect which has the same position as the scribed alignment mark.
  • Subsequent heating of the wafer causes the defect to migrate upwardly through a lightly doped epitaxial layer to the front side of the wafer and produce therein a visible mirror image of the scribed alignment mark.
  • the fiducial marks can be located at a controlled depth inside the silicon ingot or wafer bulk and the fiducial marks can be made of almost any shape.
  • the fiducial marks can include different geometrical shapes alpha-numeric characters, bar codes and QR codes. Since the fiducial marks are locatedat a controlled depth at the interior of the silicon ingot or wafer bulk, they are not affected by different wafer processing steps such as thinning. They are also not affected by exposure to high temperature and therefore remain optically-recognizable through the whole steps of wafer processing.
  • the apparatus for creation at controlled depth in the inside of the single crystal silicon ingot or wafer of the fiducial marks includes a high energy pulsed femtosecond laser and a high NA (typically, larger than 0.6) focusing optics.
  • the wavelength of the laser is selected to be in a wavelength rangewhere the single crystal silicon ingot or wafer issubstantially transparent, and in particular at a wavelength longer than 1.1 ⁇ .
  • Figure 1 is an example of fiducial marks at the wafer backside used to mark wafer orientation
  • Figure2 is a schematic illustration of creation of fiducial marks in in the interior of a wafer silicon bulk according to the present method
  • Figure 3 and 4 illustrateexamples of fiducial marks created in the interior of a silicon wafer using the present method
  • Figure 5 is an example of fiducial marks created in the interior of a silicon wafer using the present method useful for determination of the wafer orientation
  • Figure 6 illustrates an additional example of fiducial marks created in the interior of a silicon wafer using the present method
  • Figure 7 illustratesan example of fiducial marks created in accordance with the present method and their visibility before and after being exposed to a thermal load
  • Figure 8 is an example of marking of a single crystal silicon ingot according to a pre-defined crystallographic orientation
  • Figure 9 is a schematic illustration of an example of an apparatus for marking orientation of single crystal ingots and wafers.
  • Figure 10 is an example of a wafer sliced from an ingot wafer with an orientation mark written in the ingot according to the present method.
  • Patent Cooperation Treaty Publication WO 2011/089592 to the same assigneeand the same inventors describes a method for processing the interior of silicon wafer by laser radiation for waveguide creation. The method described is based on modifying crystalline structure of silicon due to interaction with high power pulsed laser radiation in a spectral range where silicon is transparent.
  • Figure 1 illustrates an example of fiducials marks written at the backside of awaferlOO as has been suggested at G450C450mm Industry Briefing at Semicon Japan, December 2013.
  • the mark or marks which are one of examples, indicate the orientation of the wafer relative to a pre-defined crystallographic axes or planes orientation.
  • Themark 104 consists of isolated dots 108that once recognized by an optical imaging device, includeall of the information related to the crystallographic axes or planes orientation.
  • Numeral 112 marks edge of wafer 100.
  • Figure 2 is a schematic illustration of fiducial marks writtenin the interior of a wafer silicon bulk. Shown is a segment of a silicon wafer 200 having a front side 204 and a backside 208. Front side 204 is the side where the semiconductors chips will be created and backside208 is the side where the fiducial marks are created according to the prior art.
  • laser beam212 is focused by an optical objective 216 to create a focused laser radiation beam illustrated as focusing beams 212-1 and 212-2 with optical pass in the air and inside the silicon bulk, respectively to create an optically recognizable mark or dot 224 that consists of a local volume of modified crystalline structurein the interior of the wafer.
  • the energy of the pulsed laser for thecreation the fiducial mark would generally be 0.1 ⁇ to 10 ⁇ J.
  • the laser wavelength could be 1.55 ⁇ and pulse width would be approximately 0.8psecto ⁇ Marks can also be created by applying the laser illumination from the backside of the wafer 208.
  • Such lasers are commercially available from Polaronyx, San Jose, California under the name Uranus 1500-1550-0800 and from RayDiance, Petaluma, California under the name RayDiance R-200.
  • objective 216 is the Olympus LCPLNI OOXIR achromatic infrared objective with Numerical Aperture (NA)of 0.85 and Magnification oflOOX.
  • Objective 216 includes a correction mechanism to compensate for aberration inside siliconof any depth between 0- lmm.
  • the objective and the wafer are mounted to support relative movementbetween them such that a desired location of the focal spot inside the wafer can be archived. This can be done using the X-Y axes of an X- Y-Z stage (not shown) that are available from a large number of suppliers.
  • the target depth 228 ( Figure 2)can be achieved by relatively moving the wafer 200 and/or the objective 216 at the vertical (z) direction using the Z axis motion capability of the same X-Y-Z stage, until the desired depth 216 in is reached.
  • the aberration compensation mechanism of objective 216 described above, is operated to achieve optimal optical performance at the focal plane of objective 216 spot 224. If necessary, fine tuning of the location of point 224 may be further accomplished by introducing slight, controlled tilt of laser beam 212, using a scanning mirror, a technique known in the art.
  • Figure 3 and 4 are examples of fiducial marks created in the interior of a silicon wafer using the present method.
  • the images of these fiducial marks were acquired with a near IR microscope, using 20X objective and standard halogen lamp illumination.
  • Various mark patterns with different sizes and depths illustrated in Figures 4-6 can be produced using the method described above.
  • FIG. 5 is an example of fiducial marks useful for determination of the wafer orientation created in the interior of a silicon wafer using the present method.
  • Fiducial marks 500 were written at depth of 300 ⁇ , as opposed to 150 ⁇ of previous marks, to demonstrate the ability of the present invention to control the depth at which the fiducial marks are created to any pre-determineddesired value.
  • Figure 6 illustrates an additional example of a fiducial mark created in the interior of a silicon wafer using the present method.
  • 600 is the image of the fiducial acquired using an IR microscope while 604 is an image of the same fiducial acquired using a high resolution X-Ray device such as, for example,XRD- I system commercially available from Jordan Valley Semiconductors Ltd., Migdal HaEmek 23100 Israel, and described in US patent 6,782,076.
  • XRD- I system commercially available from Jordan Valley Semiconductors Ltd., Migdal HaEmek 23100 Israel
  • Figure 7 illustrates an example of fiducial marks created in accordance with the present method and their visibility after the fiducial marks have been exposed to a thermal load, which is typical of the steps in wafer manufacturing process.
  • Figure 7 A shows fiducial marks 700 immediately after the marks have been created.
  • Figure 7B shows the same fiducial marks 700 after the marks have been exposed for 1 hour to a temperature of 800°C, and
  • Figure 7C shows the same fiducial marks after being exposed for additional 2 hours at temperature of 800°C.
  • Figure 8 is an example of marking process of a single-crystal silicon ingot according to a predefined crystallographic orientation.
  • Figure 8 illustratesthe silicon ingot 800 prior to its slicing into individual silicon wafers.
  • single crystal silicon ingot 800 has a cylindrical shape with a diameter substantially equal to that of the resulting wafers (for example 450mm).
  • a typical height of single crystal silicon ingot 800 could be 0.5m to 2m.
  • the pre-defined crystallographic direction is first determined by an X-Ray crystallographic axis orientation determination system and an orientation mark 804is made on single crystal silicon ingot 800.
  • Figure 9 A is a schematic illustration of an example of an apparatus for marking orientation of single crystal ingots.
  • Apparatus 900for marking single crystal ingots includes a load port 904, an orienting device 908 configured to determining crystalline orientation of a single crystal silicon ingot 800. Orienting device 908 could also orient and proper position for creating fiducial marks 924 in single crystal silicon ingot 800.
  • Apparatus 900 includes a fiducial mark writing system 910 that can be similar to writing system of Figure 2.
  • Writing system 910 includes a laser scanner912 configured to mark orientation of silicon ingot or wafers and an optical system 930 configured to focus the fiducial marks 924 writing laser beam inside ingot 800 at practically any depth.
  • Relative movement between writing system 910 facilitates fiducial marks 924 writing inside cylindrical ingot 800 and along the length of the cylindrical ingot 800.
  • an additional cylindrical lens 934 is added to optical system 930 to compensate for the ingot radial curvature.
  • the method of marking a single crystal silicon ingot results in a single crystal ingot of cylindrical shape which includes at least one optically recognizable fiducial mark located inside the single crystal ingot.
  • the optically recognizable mark indicates orientation of the single crystal along the cylindrical shape length and inside the single crystal ingot.
  • the optically recognizable fiducial mark may characterize a pre-defined crystallographic orientation.
  • the mark canbe such as a point mark, a line mark or other geometrical shape facilitating the characterization of a pre-defined crystallographic orientation.
  • the created fiducial marks are optically recognizable and canbe represented a local volume of modified crystalline structure.
  • the modified crystalline structure can belocated at a depthof50 ⁇ to 1.0 mm from the cylindrical shape surface.
  • Theoptically recognizable fiducial mark indicating orientation of the crystallographic axes in the wafer can be created and located inside the wafer, between a front and back surfaces.
  • the optically recognizable fiducial marks consist of alocal volume of modified crystalline structure.
  • Thefiducial mark can be recognized by an optical microscope working in an IR spectral range and with a spatial resolution of about 1 urn.
  • Figure 10 illustrates a wafer 1000 after being sliced from ingot 800, wherein orientation mark 1004 is created within the ingot by apparatus described and according to the present method.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Mechanical Treatment Of Semiconductor (AREA)
  • Laser Beam Processing (AREA)

Abstract

A method of marking ingots and wafers using a laser to create fiducial marks in the bulk of the ingot or wafer. Disclosed is a method for creating durable, optically-recognizable fiducial marks for indicating single crystal ingot and wafer orientation and other types of information required by the chips manufacturers. The fiducial marks can be located at a controlled depth inside the silicon ingot or wafer bulk and the fiducial marks can be made of almost any shape.

Description

A METHOD AND APPARATUS FOR INTERNAL MARKING OF INGOTS AND
WAFERS
This application claims priority to and the benefit of US provisional patentapplication No. 61/941,494 filed February 19, 2014 and to patent Cooperation Treaty Publication WO 2011/089592 the entire disclosure of whichis herein incorporated by reference.
TECHNOLOGY FIELD
[001] The present invention relates to a field of marking single crystals in general and particularly of marking single-crystalline semiconductor silicon ingots and wafers.
BACKGROUND
[002] Wafers are grown from crystal ingots having a regular crystal structure. When ingots are cut into wafers, the surface is aligned in one of several relative directions known as crystal orientations. Crystal orientation is defined by the Miller index with [100] or [111] faces being the most common for silicon.
[003] Wafers are used for semiconductor chip manufacturing and wafer processing and properties are dependent on the orientation of their crystallographic planes orientation. Wafers are usually marked to indicate their pre-defined crystallographic orientation. The marking could alsoindicate wafer serial number, chip ID and alike.
[004] Marks or fiducial marks occupy on the wafer certain area that could be used to increase yield of manufactured components. Despite the growth of the wafer size, specifically at the 450mm wafers, there is a requirementto eliminate orientation marks such as flats and notches and replace them by marking at the wafer backside. Marking at the back side would avoid loss of wafer area at the notch/flat area and also to eliminate stresses due to the irregularity introduced by the presence of aflat/notch.
[005] There is still an issue associated with backside marking, namely, the survivability in terms of visibility of these marks during and after the processing steps, for example etching, that the wafer undergoes. Also, backside marks may be source of contamination which may be detrimental to chip manufacturing yield. There is, therefore, a need to introduce a method for creation of the marks which will still be visible and useful and contamination-free, regardless of the wafer processing steps.
[006] There is also a need to mark the ingot orientation prior to wafer slicing as to have orientation indication on the wafers just after slicing.
[007] Japanese Patent application JP2001080297describes a method for the creation of graphic characters inside silicon bulk using a laser at a wavelength between 0.3 μηι and 1.1 μιη and beam conversion angle of 5° to 20°.
[008] US patent 4,534,804 describes a method for scribing alignment marks using a laser beam on the back side of a lightly doped substrate of a silicon wafer containing a heavily doped internal layer. The wavelength of the laser beam is chosen such that it passes through the lightly doped substrate without absorption but is absorbed in the heavily doped internal layer to produce therein a defect which has the same position as the scribed alignment mark. Subsequent heating of the wafer causes the defect to migrate upwardly through a lightly doped epitaxial layer to the front side of the wafer and produce therein a visible mirror image of the scribed alignment mark.
SUMMARY
[009] Disclosed is a method for creating durable, optically-recognizablefiducial marks for indicating single crystalingot and wafer orientation and other types of information required by the chips manufacturers. The fiducial marks can be located at a controlled depth inside the silicon ingot or wafer bulk and the fiducial marks can be made of almost any shape. The fiducial marks can include different geometrical shapes alpha-numeric characters, bar codes and QR codes. Since the fiducial marks are locatedat a controlled depth at the interior of the silicon ingot or wafer bulk, they are not affected by different wafer processing steps such as thinning. They are also not affected by exposure to high temperature and therefore remain optically-recognizable through the whole steps of wafer processing. [0010] The apparatus for creation at controlled depth in the inside of the single crystal silicon ingot or wafer of the fiducial marks includes a high energy pulsed femtosecond laser and a high NA (typically, larger than 0.6) focusing optics. The wavelength of the laser is selected to be in a wavelength rangewhere the single crystal silicon ingot or wafer issubstantially transparent, and in particular at a wavelength longer than 1.1 μηι.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 is an example of fiducial marks at the wafer backside used to mark wafer orientation;
[0012] Figure2 is a schematic illustration of creation of fiducial marks in in the interior of a wafer silicon bulk according to the present method;
[0013] Figure 3 and 4 illustrateexamples of fiducial marks created in the interior of a silicon wafer using the present method;
[0014] Figure 5 is an example of fiducial marks created in the interior of a silicon wafer using the present method useful for determination of the wafer orientation;
[0015] Figure 6 illustrates an additional example of fiducial marks created in the interior of a silicon wafer using the present method;
[0016] Figure 7 illustratesan example of fiducial marks created in accordance with the present method and their visibility before and after being exposed to a thermal load;
[0017] Figure 8 is an example of marking of a single crystal silicon ingot according to a pre-defined crystallographic orientation; and
[0018] Figure 9 is a schematic illustration of an example of an apparatus for marking orientation of single crystal ingots and wafers; and
[0019] Figure 10 is an example of a wafer sliced from an ingot wafer with an orientation mark written in the ingot according to the present method.
DESCRIPTION
[0020] As indicated above there is a need for a method for creation of marks which will still be visible and useful, regardless of the wafer processing steps. [0021] There is also a need to mark the ingot orientation prior to wafer slicing such as to have orientation indication on the wafers just after slicing.
[0022] Patent Cooperation Treaty Publication WO 2011/089592 to the same assigneeand the same inventors describes a method for processing the interior of silicon wafer by laser radiation for waveguide creation.The method described is based on modifying crystalline structure of silicon due to interaction with high power pulsed laser radiation in a spectral range where silicon is transparent.
[0023] Figure 1 illustrates an example of fiducials marks written at the backside of awaferlOO as has been suggested at G450C450mm Industry Briefing at Semicon Japan, December 2013. The mark or marks, which are one of examples, indicate the orientation of the wafer relative to a pre-defined crystallographic axes or planes orientation. Themark 104, consists of isolated dots 108that once recognized by an optical imaging device, includeall of the information related to the crystallographic axes or planes orientation. Numeral 112 marks edge of wafer 100.
[0024] Figure 2is a schematic illustration of fiducial marks writtenin the interior of a wafer silicon bulk. Shown is a segment of a silicon wafer 200 having a front side 204 and a backside 208. Front side 204 is the side where the semiconductors chips will be created and backside208 is the side where the fiducial marks are created according to the prior art. According to the present example, laser beam212 is focused by an optical objective 216 to create a focused laser radiation beam illustrated as focusing beams 212-1 and 212-2 with optical pass in the air and inside the silicon bulk, respectively to create an optically recognizable mark or dot 224 that consists of a local volume of modified crystalline structurein the interior of the wafer.The energy of the pulsed laser for thecreation the fiducial mark would generally be 0.1 μΐ to 10μJ. The laser wavelength could be 1.55 μιη and pulse width would be approximately 0.8psecto Ιμβεα Marks can also be created by applying the laser illumination from the backside of the wafer 208.
[0025] Such lasers are commercially available from Polaronyx, San Jose, California under the name Uranus 1500-1550-0800 and from RayDiance, Petaluma, California under the name RayDiance R-200.An example of objective 216 is the Olympus LCPLNI OOXIR achromatic infrared objective with Numerical Aperture (NA)of 0.85 and Magnification oflOOX.Objective 216 includes a correction mechanism to compensate for aberration inside siliconof any depth between 0- lmm.
[0026] Since silicon is transparent for single-photon absorption at the wavelength of 1.55μη (α~3χ10-8 cm-1), laser light willpropagatewith no absorption from surface 204 to focal point 224. At focal point 224, due to a combination of the high laser pulseenergyand the short laser pulse duration, an extreme power density is developed. This power density creates multiple photon absorption at focal point 224, and a mark or dot is created in the bulk of silicon wafer 200. The mark consists of a local volume of modified crystalline structure and since it has a different refraction index it can be recognized by optical means. Typical pulse energy supporting creation of such dot or mark with an objective with NA=0.85 and pulse duration of 1.0 picosecondwas approximately Ι.Ο Ι to 2.0μΙ. The mark or dot can be created in silicon wafer 200 at the predetermined location and depthusing the following process:
[0027] The objective and the wafer are mounted to support relative movementbetween them such that a desired location of the focal spot inside the wafer can be archived. This can be done using the X-Y axes of an X- Y-Z stage (not shown) that are available from a large number of suppliers.
[0028] The target depth 228 (Figure 2)can be achieved by relatively moving the wafer 200 and/or the objective 216 at the vertical (z) direction using the Z axis motion capability of the same X-Y-Z stage, until the desired depth 216 in is reached. Concurrently, the aberration compensation mechanism of objective 216, described above, is operated to achieve optimal optical performance at the focal plane of objective 216 spot 224. If necessary, fine tuning of the location of point 224 may be further accomplished by introducing slight, controlled tilt of laser beam 212, using a scanning mirror, a technique known in the art.
[0029] Figure 3 and 4 are examples of fiducial marks created in the interior of a silicon wafer using the present method. The images of these fiducial marks were acquired with a near IR microscope, using 20X objective and standard halogen lamp illumination. Various mark patterns with different sizes and depths illustrated in Figures 4-6 can be produced using the method described above. [0030] In a particular case, marks 300 and 304 were created at depth (d) of 150μηι inside the silicon bulk, using NA=0.85 optics and pulse energy of 1.1 μ5. Location of fiducial marks at deeper of shallower wafer levels could require different energy.
[0031] Figure 5 is an example of fiducial marks useful for determination of the wafer orientation created in the interior of a silicon wafer using the present method. Fiducial marks 500 were written at depth of 300μηι, as opposed to 150μηι of previous marks, to demonstrate the ability of the present invention to control the depth at which the fiducial marks are created to any pre-determineddesired value.
[0032] Figure 6 illustrates an additional example of a fiducial mark created in the interior of a silicon wafer using the present method. 600 is the image of the fiducial acquired using an IR microscope while 604 is an image of the same fiducial acquired using a high resolution X-Ray device such as, for example,XRD- I system commercially available from Jordan Valley Semiconductors Ltd., Migdal HaEmek 23100 Israel, and described in US patent 6,782,076. The visibility of the internal fiducial marks with X-Ray imaging is clearly demonstrated
[0033] Figure 7 illustrates an example of fiducial marks created in accordance with the present method and their visibility after the fiducial marks have been exposed to a thermal load, which is typical of the steps in wafer manufacturing process. Figure 7 A shows fiducial marks 700 immediately after the marks have been created. Figure 7B shows the same fiducial marks 700 after the marks have been exposed for 1 hour to a temperature of 800°C, and Figure 7C shows the same fiducial marks after being exposed for additional 2 hours at temperature of 800°C.
[0034] Generally, single crystal ingots typicallyhave a cylindrical shape.Figure 8 is an example of marking process of a single-crystal silicon ingot according to a predefined crystallographic orientation. Figure 8illustratesthe silicon ingot 800 prior to its slicing into individual silicon wafers. As shown in 8, single crystal silicon ingot 800 has a cylindrical shape with a diameter substantially equal to that of the resulting wafers (for example 450mm). A typical height of single crystal silicon ingot 800 could be 0.5m to 2m. The pre-defined crystallographic direction is first determined by an X-Ray crystallographic axis orientation determination system and an orientation mark 804is made on single crystal silicon ingot 800. [0035] Figure 9 A is a schematic illustration of an example of an apparatus for marking orientation of single crystal ingots. Apparatus 900for marking single crystal ingots includes a load port 904, an orienting device 908 configured to determining crystalline orientation of a single crystal silicon ingot 800. Orienting device 908 could also orient and proper position for creating fiducial marks 924 in single crystal silicon ingot 800. Apparatus 900 includes a fiducial mark writing system 910 that can be similar to writing system of Figure 2. Writing system 910 includes a laser scanner912 configured to mark orientation of silicon ingot or wafers and an optical system 930 configured to focus the fiducial marks 924 writing laser beam inside ingot 800 at practically any depth. Apparatus 900canalso include an optional inspection device 920 and an unload port924 to unload from apparatus 900 single crystal silicon ingot 800 with properly embedded inside the ingot fiducial marks 924.
[0036] Relative movement between writing system 910 facilitates fiducial marks 924 writing inside cylindrical ingot 800 and along the length of the cylindrical ingot 800. In some examples (Figure 9B) an additional cylindrical lens 934is added to optical system 930 to compensate for the ingot radial curvature. By using relative movement between the ingot 800 and the writing system 910, as illustrated by arrow 938 the whole length of ingot 800 is marked.
[0037] Although this descriptionuses in most of the examplessilicon, it is clear to those skilled in the art that the method of creating fiducial marks is applicable to a plurality of materials such as for example, silicon, gallium arsenide, gallium nitride, silicon carbide, sapphire, diamond and quartz.
[0038] The method of marking a single crystal silicon ingot results in a single crystal ingot of cylindrical shape which includes at least one optically recognizable fiducial mark located inside the single crystal ingot. The optically recognizable mark indicates orientation of the single crystal along the cylindrical shape length and inside the single crystal ingot.The optically recognizable fiducial mark may characterize a pre-defined crystallographic orientation. The mark canbe such as a point mark, a line mark or other geometrical shape facilitating the characterization of a pre-defined crystallographic orientation. The created fiducial marks are optically recognizable and canbe represented a local volume of modified crystalline structure. The modified crystalline structure can belocated at a depthof50 μη to 1.0 mm from the cylindrical shape surface.
[0039] Marking of the orientation of crystallographic axes or planes by optically recognizable fiducial marks in a single crystal wafer can be done in a similar process. Theoptically recognizable fiducial mark indicating orientation of the crystallographic axes in the wafer can be created and located inside the wafer, between a front and back surfaces. As disclosed above, the optically recognizable fiducial marks consist of alocal volume of modified crystalline structure. Thefiducial mark can be recognized by an optical microscope working in an IR spectral range and with a spatial resolution of about 1 urn.
[0040] Figure 10 illustrates a wafer 1000 after being sliced from ingot 800, wherein orientation mark 1004 is created within the ingot by apparatus described and according to the present method.

Claims

WHAT IS CLAIMED IS:
LA single crystal ingot of cylindrical shape which includes at least one optically recognizable mark located inside the single crystal ingot, the optically recognizable mark indicates orientation of thesingle crystal along the cylindrical shape length and inside the single crystal ingot.
2. A single crystal ingot according to claim 1, wherein the at least one optically recognizable mark consists of at least one local volume of modified crystalline structure located at a distance of 50 μιη to 5.0 mm from the cylindrical shape surface.
3. A single crystal ingot according to claim 2, wherein the modified crystalline structure is produced by locally focused pulsed laser radiation witha pulse shorter than l sec and with a wavelength at which said single crystal is transparent.
4. An ingot according to claim 1 , wherein said optically recognizable mark is at least one from the following group: a point, a line or other geometrical shape, which may characterize a pre-defined crystallographic orientation.
5. A single crystal ingot according to claim 1, wherein said crystal is at least one of the following materials: silicon, gallium arsenide, gallium nitride, silicon carbide, sapphire, diamond and quartz.
6. A single crystal wafer having front and back surfaces and thickness of 50 μπι to 5.0 mm, the single crystal wafer includes at least one optically recognizable mark located inside the wafer, between said front and back surfaces, and wherein said mark indicates a crystallographic orientation of said crystal.
7. A single crystal wafer according to claim 6, wherein the at least one optically recognizable mark consists of at least one local volume of modified crystalline structure.
8. A single crystal wafer according to claim 6, wherein the wafer is at least one of the group of materials consisting of silicon, gallium arsenide, gallium nitride, silicon carbide, sapphire, diamond and quartz.
9. A single crystal wafer according to claim 6, wherein the modified crystalline structure is produced by locally focused pulsed laser radiation with a pulse shorter than 1 psec and a wavelength at which said single crystal is transparent.
10. A single crystal wafer according to claim 6 made of silicon, wherein the modified crystalline structure is produced by locally focused pulsed laser radiation with a pulseradiation with a pulse shorter than 1 psec with a wavelength longer than 1.1 um, and a power greater than 0.1 J/pulse.
11. A single crystal wafer according to claim 6, wherein the optically recognizable mark is at least one of a group of marks consisting of a point, a line, an arrow or other geometrical shape, wherein the geometrical shape indicates a pre-defined crystallographic orientation.
12. A single crystal wafer according to claim 10 made of silicon, wherein the mark is recognizable by an optical microscope working in an IR spectral range and with a spatial resolution of about 1 um.
13. An apparatus for marking orientation of single crystal ingots and wafers comprising:
a load port,
an orienting device configured to determining crystalline orientation of a said single crystal and orienting it in said apparatus,
a laser scanner configured to locally modify the crystalline structure inside said single crystal,
an optional inspection device and
an unload port.
14. An apparatus according to claim 13, wherein said orienting device applies an X- ray diffraction.
15. An apparatus according to claim 13 for marking orientation of silicon ingots or wafers, wherein said laser scanner applies a pulsed laser radiation with a wavelength greater than 1.1 um, pulse duration shorter than 1 psec and a pulse power greater than 0.1 J/pulse.
16. A method of internal marking single crystal orientation including
- providing X-ray and optical means for single crystal orientation and marking,
- determining the crystallographic orientation of the single crystal with help of X-ray metrology,
- positioning the crystal in the optical system according to the determined crystallographic orientation,
focusing a high power short pulse laser radiation at a controlled depth beneath the crystal surface in order to modify crystal structure providing a dot mark indicating the crystal orientation,
scanning said focused laser beam in order to create an orientation mark consisting of at least one said dot mark.
17. A method according to claim 16, which additionally includes creating at least one mark of the following group: alpha-numeric characters, bar codes and QR codes for indicating the crystal's serial number or other related data.
18. A method according to anyone of Claims 16 and 17 wherein the single crystal is a cylindrical ingot or circular wafer.
19. A method according to Claims 16 and 17 wherein the single crystal is made of one of a group of materials consisting of silicon, gallium arsenide, gallium nitride, silicon carbide, sapphire, diamond and quartz.
PCT/IL2015/050168 2014-02-21 2015-02-15 A method and apparatus for internal marking of ingots and wafers WO2015125134A1 (en)

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US12213295B2 (en) 2023-03-15 2025-01-28 EllansaLabs Inc. Diamond-based electromagnetic interference shield

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