WO2010049846A2 - Semiconductor chip, method of manufacturing a semiconductor chip, and method of testing a semiconductor chip - Google Patents

Semiconductor chip, method of manufacturing a semiconductor chip, and method of testing a semiconductor chip Download PDF

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Publication number
WO2010049846A2
WO2010049846A2 PCT/IB2009/054610 IB2009054610W WO2010049846A2 WO 2010049846 A2 WO2010049846 A2 WO 2010049846A2 IB 2009054610 W IB2009054610 W IB 2009054610W WO 2010049846 A2 WO2010049846 A2 WO 2010049846A2
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WIPO (PCT)
Prior art keywords
metal layer
semiconductor chip
layer portions
width
solder bumps
Prior art date
Application number
PCT/IB2009/054610
Other languages
French (fr)
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WO2010049846A3 (en
Inventor
Peter Bancken
Hendrikus Johannes Jacobus Thoonen
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Nxp B.V.
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Publication date
Application filed by Nxp B.V. filed Critical Nxp B.V.
Publication of WO2010049846A2 publication Critical patent/WO2010049846A2/en
Publication of WO2010049846A3 publication Critical patent/WO2010049846A3/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/10—Bump connectors ; Manufacturing methods related thereto
    • H01L24/12—Structure, shape, material or disposition of the bump connectors prior to the connecting process
    • H01L24/14—Structure, shape, material or disposition of the bump connectors prior to the connecting process of a plurality of bump connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/30—Structural arrangements specially adapted for testing or measuring during manufacture or treatment, or specially adapted for reliability measurements
    • H01L22/32—Additional lead-in metallisation on a device or substrate, e.g. additional pads or pad portions, lines in the scribe line, sacrificed conductors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/10—Bump connectors ; Manufacturing methods related thereto
    • H01L24/12—Structure, shape, material or disposition of the bump connectors prior to the connecting process
    • H01L24/13—Structure, shape, material or disposition of the bump connectors prior to the connecting process of an individual bump connector
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/10—Bump connectors; Manufacturing methods related thereto
    • H01L2224/12—Structure, shape, material or disposition of the bump connectors prior to the connecting process
    • H01L2224/13—Structure, shape, material or disposition of the bump connectors prior to the connecting process of an individual bump connector
    • H01L2224/13001—Core members of the bump connector
    • H01L2224/13099—Material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/10—Bump connectors; Manufacturing methods related thereto
    • H01L2224/12—Structure, shape, material or disposition of the bump connectors prior to the connecting process
    • H01L2224/13—Structure, shape, material or disposition of the bump connectors prior to the connecting process of an individual bump connector
    • H01L2224/13001—Core members of the bump connector
    • H01L2224/13099—Material
    • H01L2224/131—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/10—Bump connectors; Manufacturing methods related thereto
    • H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process
    • H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector
    • 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
    • H01L2924/00011—Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
    • 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
    • H01L2924/00014—Technical content checked by a classifier the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
    • 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
    • H01L2924/01—Chemical elements
    • H01L2924/01005—Boron [B]
    • 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
    • H01L2924/01—Chemical elements
    • H01L2924/01006—Carbon [C]
    • 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
    • H01L2924/01—Chemical elements
    • H01L2924/01013—Aluminum [Al]
    • 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
    • H01L2924/01—Chemical elements
    • H01L2924/01033—Arsenic [As]
    • 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
    • H01L2924/01—Chemical elements
    • H01L2924/01079—Gold [Au]
    • 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
    • H01L2924/01—Chemical elements
    • H01L2924/01082—Lead [Pb]

Definitions

  • SEMICONDUCTOR CHIP AND METHOD OF TESTING A SEMICONDUCTOR CHIP.
  • the invention relates to a semiconductor chip having a surface provided with a first set of mutually similar first metal layer portions having a first width along the surface.
  • the invention further relates to a method of manufacturing a semiconductor chip, including applying a first set of first metal layer portions on a surface of a semiconductor chip with a first width along the surface.
  • the invention relates to a method of testing a semiconductor chip by using a testing apparatus provided with a group of mutually similar flexible measurement needles.
  • the invention also relates to an assembly of a semiconductor chip and an external substrate.
  • the invention further relates to a product including a semiconductor chip.
  • the invention relates to use of a semiconductor chip.
  • Semiconductor chips are provided with a plurality of external contact elements such as solder bumps, or layer portions that form contact pads for bonding wires thereon.
  • a subgroup of the plurality of these contacting elements acts as functional contact elements to the semiconductor chip.
  • these functional contact elements are normally used for electrical testing of the semiconductor chip as well. Such electrical testing can take place for quality assessment during manufacturing, or for failure analysis of semiconductor chips returned by customers.
  • another subgroup of the contact elements is dedicated to testing only, without being needed for functionally contacting the semiconductor chip.
  • Semiconductor chips have shown a trend towards smaller feature sizes of circuitry on a semiconductor substrate of the semiconductor chip. As a result, a necessary number of external contact elements per unit of substrate area has increased as well. However, a size of the contact elements has stayed relatively constant. As a result, for many chip types the substrate area needed for placing the contact elements limits a minimum size of the semiconductor substrate, instead of the substrate area that is needed for placing active circuitry and test circuitry of the semiconductor chip. This in general leads to an increased substrate area, which is very costly.
  • the redistributive package for the semiconductor chip provides additional area for placing the contact elements.
  • at least one additional layer for fan out structures from the circuitry of the semiconductor chip towards the contact elements is needed.
  • Such a layer adds to cost and complexity of the packaged chip, thus increasing a probability for errors in manufacturing of the semiconductor chip and introducing reliability issues.
  • the trend towards smaller feature sizes of the circuitry on the semiconductor chip is expected to continue, which may lead to an increasing amount of contact elements.
  • a size of the redistributive package has to increase as well, which again increases cost and can also be expected to worsen the reliability issues. Accordingly, it is an object of the invention to provide a semiconductor chip with improved use of area on the semiconductor chip.
  • the invention provides a semiconductor chip having a surface provided with a first set of mutually similar first metal layer portions that have a first width along the surface, the surface further being provided with a second set of mutually similar second metal layer portions that have a second width along the surface, each first metal layer portion forming an external functional contact surface of the semiconductor chip, and each second metal layer portion forming an external test contact surface of the semiconductor chip, wherein the second width is substantially smaller than the first width.
  • the first width being smaller than the second width enables an improved distribution of the first and second metal layer portions over the surface. Because of the smaller width of the second metal layer portions, part of the surface that is too small for placement of the first metal layer portion, may be used for placing the second metal layer portion.
  • the smaller width of the second metal layer portions enables these to be applied on the surface in a higher number per unit of area of the surface than the first metal layer portions. In this way, a more efficient use of the surface can be achieved.
  • the second metal layer portions are distinct from the first metal layer portions.
  • the semiconductor chip in use is free of external electrical contact via the external test contact surface.
  • the external functional contact surface is arranged for electrically testing the semiconductor chip, for example for quality assessment during manufacturing of the semiconductor chip, or during failure analysis after use of the semiconductor chip.
  • the external functional contact surface may be arranged for both testing and functionally contacting the semiconductor chip.
  • the external test contact surface is arranged for electrical testing only.
  • the first set does not necessarily form all external functional contact surfaces of the semiconductor chip. However, in an embodiment, the first set does form all external functional contact surfaces of the semiconductor chip. It may be clear that the second set does not necessarily form all external test contact surfaces of the semiconductor chip. However, in an embodiment, the second set does form all external test contact surfaces of the semiconductor chip. The two latter embodiments in combination substantially maximize an efficiency of use of the surface.
  • a first separation of a neighbouring pair of the first metal layer portions is larger than a second separation of a neighbouring pair of the second metal layer portions. Preferably, this holds for each neighbouring pair of the first metal layer portions, in comparison with one of the second metal layer portions, preferably in comparison with all of the second metal layer portions.
  • the first separation of the neighbouring pair of the first metal layer portions is larger than a third separation of a neighbouring pair of a first metal layer portion of the first set and a second metal layer portion of the second set.
  • the first metal layer portions have a first height and the second metal layer portions have a second height being substantially smaller than the first height.
  • the second height is at most 70% of the first height. This reliably prevents electrical and/or mechanical contact of the second metal layer portions with the external substrate.
  • the second height is at least 40% of the first height. In this way, a vertical probe apparatus with flexible needles for contacting the first and second metal layer portions, can still contact all of the first and second metal layer portions simultaneously.
  • the second height being in a range from 40% to 70% of the first height combines these two advantages.
  • the inventors realised that, without being bound by the second width being smaller than the first width, it is advantageous to have the second metal layer portions being resistant against chemical and/or mechanical damage, while still being accessible for external electrical testing.
  • the second metal layer portions may therefore be deposited on contact pads that do not have such resistance, i.e. directly on the last metallisation layer of f.i. aluminium. A testing surface of these contact pads is thus replaced by the external test contact surface. These contact pads would normally be used for testing, according to known testing methods.
  • the second metal layer portions are formed by metallisation layer portions, for example electrolessly deposited nickel layer portions, possibly provided with a thin gold coating.
  • the metallisation layer portions may be applied on the contact pads, that are normally used for testing, and that may be formed by the other layer portions that for example contain aluminium.
  • the metallisation layer portions protect the contact pads during later process steps, for example against mechanical damage and/or against chemical degradation like corrosion of the other layer portions that form the contact pads.
  • the metallisation layer portions may enable contacting the semiconductor chip while it is mounted, for example on a printed circuit board. In this way a surprising combination of protection and possibility for electrically contacting is achieved, as protection is normally achieved by applying an isolating material.
  • the first metal layer portions are formed by first solder bumps.
  • first solder bumps may be deposited on under-bump metallisation layer portions that are similar to the metallisation layer portions.
  • the metallisation layer portions and the under-bump metallisation layer portions although preferably being distinct from each other, can be deposited in the same process steps.
  • the first metal layer portions may be arranged for application of a wire thereon for wirebonding the semiconductor chip.
  • the first layer portions contain aluminium.
  • the first metal layer portions are formed by first solder bumps and the second metal layer portions are formed by second solder bumps.
  • the first width equals a diameter of the first solder bumps.
  • the second width equals a diameter of the second solder bumps.
  • the first solder bumps and/or the second solder bumps may be obtained after reflowing so that a curved surface is obtained under the influence of surface tension of a material of the first solder bumps and/or the second solder bumps.
  • the second metal portions have a surface area, when seen in a top view, with a length extending perpendicular to the width of the metal portions, wherein said width is smaller than said length.
  • This embodiment is particularly advantageous when the second metal portions are located at one or more edges of the surface.
  • the location of test surfaces along an edge enables contacting of the second metal layer via the external test contact surfaces after the semiconductor chip is applied to the printed circuit board. It also enables testing of the semiconductor chip during failure analysis of the semiconductor chip, without having to disassemble the semiconductor chip from the printed circuit board. In addition, repackaging of the semiconductor chip for making it fit on a test platform arranged for failure analysis, can be prevented.
  • the second metal layer portions is located in between the first metal layer portions.
  • the second metal layer portions are interposed between the second metal layer portions.
  • the first metal layer portions and the second metal layer portion may be positioned in respectively a first pattern and a second pattern, which may overlap with the first pattern.
  • the first pattern and optionally the second pattern extend substantially over the whole surface, while the first and second layer portions are still separate from each other.
  • the first metal layer portions are individually connected to the surface in first areas, and the second metal layer portions are individually connected to the surface in second areas, wherein the first areas are substantially larger, preferably at least 1.3 times larger, than the second areas.
  • This embodiment combines well with a manufacturing method wherein the first metal layer portions and the second metal layer portions are applied simultaneously in the same process step, optionally as one layer that is subsequently patterned to obtain mutually distinct first and second metal layer portions.
  • the first areas being substantially larger than the second areas than ensures that an individual bump volume of the second metal layer portions is substantially smaller than an individual bump volume of the first metal layer portions.
  • the first and second areas are arranged for being constant during reflowing
  • the first and second areas may be defined as openings in a layer on which material of the first and/or second metal layer portions has a relatively large contact angle, deposited on top of a layer on which material of the first and/or second metal layer portions has a relatively small contact angle.
  • the second metal layer portions are located along an edge of the surface.
  • the invention provides a method of manufacturing a semiconductor chip, including the steps : a) applying a first set of first metal layer portions on a surface of a semiconductor chip with a first width along the surface, each first metal layer portion forming an external functional contact surface of the semiconductor chip! b) applying a second set of second metal layer portions on the surface with a second width along the surface, each second metal layer portion forming an external test contact surface of the semiconductor chip, wherein the second width is substantially smaller than the first width.
  • the second metal layer portions are distinct from the first metal layer portions.
  • the semiconductor chip in use is free of external electrical contact via the external test contact surface.
  • the invention provides a method of testing a semiconductor chip according to the invention or manufactured by a method according to the invention, by using a testing apparatus provided with a group of mutually similar flexible measurement needles, including the steps: c) moving the measurement needles towards the surface for placing a first subgroup of the group of needles in electrical contact with the first metal layer portions! and d) further moving the measurement needles towards the surface for placing a second subgroup of the group of needles in contact with the second metal layer portions, while maintaining electrical contacts established in step c).
  • a testing method combines well with the semiconductor chip.
  • the invention also provides an assembly of an external substrate and a semiconductor chip according to the invention or manufactured by a method according to the invention, the external substrate having conductive circuitry and the semiconductor chip being assembled on the external substrate in electrical connection with the conductive circuitry via the external functional contact surface of the semiconductor chip, wherein the semiconductor chip is free of electrical connection with the conductive circuitry via the external test contact surface.
  • the external substrate may be a printed circuit board.
  • the conductive circuitry may include tracks and contact points of the printed circuit board.
  • the invention further provides a product including a semiconductor chip according to the invention or manufactured by a method according to the invention.
  • the product can for example be a mobile phone, an automotive product such as a car, and/or a computer.
  • the invention provides use of a semiconductor chip according to the invention or manufactured by a method according to the invention, including functionally contacting the semiconductor chip via the external functional contact surface while the semiconductor chip in use is free of external electrical contact via the external test contact surface.
  • Figure IA shows a known semiconductor chip!
  • Figure IB shows a known semiconductor chip 2 in a cross section!
  • Figure 2A shows a semiconductor chip in a first embodiment according to the invention
  • Figure 2B shows a semiconductor chip in a cross section
  • Figure 3B shows a semiconductor chip in a second embodiment according to the invention!
  • Figure 3B shows the semiconductor chip in a cross section
  • Figure 4A shows a semiconductor chip in a third embodiment according to the invention!
  • Figure 4B shows a semiconductor chip in a cross section.
  • Figure 5A shows a semiconductor chip in a fourth embodiment according to the invention.
  • Figure 5B shows a semiconductor chip in a cross section.
  • Figure IA shows a known semiconductor chip 2 having a surface 4.
  • Figure IB shows the known semiconductor chip 2 in a cross section A-A', indicated in figure IA.
  • the surface 4 is provided with a first set of mutually similar first metal layer portions, in this case first solder bumps 6, that have a first width Di, in this case a diameter, along the surface 4.
  • the surface 4 is further provided with a second set of mutually similar second metal layer portions, in this case second solder bumps 8.
  • the diameter of the second solder bumps 8 along the surface 4 is similar to
  • Figure 2A shows a semiconductor chip 12 in a first embodiment according to the invention.
  • Figure 2B shows the semiconductor chip 12 in a cross section B-B', indicated in figure 2A.
  • the semiconductor chip 12 has the surface 4 provided with the first set of mutually similar first metal layer portions 6, in this example being formed by the first solder bumps 6, that have the first width Di along the surface 4.
  • the surface 4 may be formed by a fan out layer arranged for electrically connecting circuitry of the semiconductor chip 12 towards the first solder bumps 6. Such a fan-out layer as such is known to the skilled person. Additionally or alternatively, the surface 4 may be formed by a silicon substrate 13 of the semiconductor chip 12, or by one or more layers (not drawn) deposited on the silicon substrate 13.
  • the surface 4 is further provided with the second set of mutually similar second metal layer portions that have a second width D2 along the surface 4, i.e. in a direction substantially parallel with a plane of the surface 4.
  • the second metal layer portions may be formed by metallisation layer portions 8.
  • the metallisation layer portions 8 may be applied by electroless deposition of nickel, optionally followed by immersion deposition of a thin gold coating.
  • a first height Hi of the metallisation layer portions may be in a range from 1 to 10 micrometer, for example 3 micrometer.
  • a thickness of the thin gold coating may be several tens of nanometers.
  • Each first solder bump 6 individually forms an external functional contact surface 14 of the semiconductor chip 12.
  • the semiconductor chip 12 may be provided with a plurality of external functional contact surfaces 14.
  • the external functional contact surfaces 14 enable, in use, guiding of electrical input signals and electrical output signal respectively to and from the semiconductor chip 12.
  • some of the first solder bumps 6, preferably all first solder bumps 6, can be used for electrically testing the semiconductor chip 12, for example during failure analysis.
  • Each metallisation layer portion 8 individually forms an external test contact surface 16 of the semiconductor chip 12.
  • the semiconductor chip 12 may be provided with a plurality of external test contact surfaces 16. It will be appreciated that the external test contact surfaces 16 may not need to be contacted for normal operation of the semiconductor chip 12.
  • the semiconductor chip 12 may be free of external electrical contact via the external test contact surfaces 16.
  • external electrical contact of the semiconductor chip 12 is exclusively via the external functional contact surfaces 14.
  • the second width D2 is substantially smaller than the first width Di.
  • the width of the first metal layer portions may mutually vary for example at most 5% or at most 10%.
  • the width of the second metal layer portions may mutually vary for example at most 5% or at most 10%.
  • Such variations may be inherent to a manufacturing method of the first and second metal layer portions, for example a stochastic and/or systematic variation therein. However, such variation may not lead to one of the first metal layer portions 6 having a substantially smaller width than another one of the first metal layer portions 6.
  • the second width D2 may be at most 70%, preferably at most 40%, of the first width Di. In this way, a significant improvement in use of the surface 4 is achieved.
  • the width Di may be in a range from 40 to 500 micrometer, for example 300 micrometer.
  • the second width D2 may be in a range from 60 to 80 micrometer.
  • a first separation Si of a neighbouring pair 20 of the first solder bumps 6 may be larger than a second separation S2 of a neighbouring pair 22 of the metallisation layer portions 8.
  • the first separation Si of the neighbouring pair 20 of the first solder bumps 6, may be measured from a center of a first one to a center of a second one of the neighbouring pair 20 of the first solder bumps 6.
  • the second separation S2 of the neighbouring pair 22 of the metallisation layer portions may be measured from a center of a first one to a center of a second one of the neighbouring pair 22 of the metallisation layer portions 8.
  • the first separation Si is typically in a range from 300 to 500 micrometer, for example 400 micrometer or 500 micrometer or a value between 400 and 500 micrometer.
  • the first set and second set together typically include a total number of metal layer portions that is in a range from 64 to 144, although the total number of metal layer portion may be above or below this range.
  • the metallisation layer portions 8 are located along an edge 23 of the surface 4.
  • electrical testing for failure analysis requires disassembling the known semiconductor chip 2 from the printed circuit board in order to make the first metal layer portions 6 accessible.
  • having the metallisation layer portions 8 located along the edge 23 enables contacting the semiconductor chip 12 in the first embodiment without having to disassemble the semiconductor chip 12 from the printed circuit board, in case electrical leads to the first metal layer portions are accessible through the second metal layer portions.
  • Figure 3A shows a semiconductor chip 12 in a second embodiment according to the invention.
  • Figure 3B shows the semiconductor chip 12 in a cross section C-C, indicated in figure 3A.
  • the semiconductor chip 12 has the surface 4 provided with the first solder bumps 6.
  • the second metal layer portions are formed by second solder bumps 8.
  • the width D2 of the second solder bumps 8 along the surface 4 is substantially smaller than the width Di of the first solder bumps 6 along the surface 4.
  • a mutual variation of for example at most 5% or at most 10% in the first and second heights is not considered as causing the second height H2 to be substantially smaller than the first height Hi.
  • the second height my at least be 40% and/or at most 70% of the first height.
  • the first height Hi may be similar to the first width Di.
  • an individual bump volume of the second solder bumps 8 may be substantially smaller than an individual bump volume of the first solder bumps 6.
  • the individual bump volume of the first solder bumps 6 is related to the width Di and the height Hi of the first solder bumps 8.
  • the individual bump volume of the second solder bumps 6 is related to the width D2 and the height H2 of the second solder bumps 8.
  • a third width along the surface 4 measured in a direction transverse to a direction in which the second width D2 is measured, is also related to the individual bump volume of the second solder bumps 8.
  • the third width D3 is similar to the first width Di.
  • the individual bump volume of the second solder bumps 8 being substantially smaller than the individual bump volume of the first solder bumps 6 ensures the second width D2 to be substantially smaller than the first width Di or the second height Hi to be substantially smaller than the first height H2.
  • the third width D3 may be similar to the second width D2 in other embodiments, for example the fourth embodiment.
  • Figure 4A shows a semiconductor chip 12 in a third embodiment according to the invention.
  • Figure 4B shows the semiconductor chip 12 in a cross section D-D', indicated in figure 4A.
  • the semiconductor chip 12 has the surface 4 provided with the first solder bumps 6 and the second solder bumps 8.
  • the width D2 of the second solder bumps 8 is substantially smaller than the width Di of the first solder bumps 6.
  • the first separation Si of the neighbouring pair 20 of the first solder bumps 6 may be larger than the second separation S2 of the neighbouring pair 22 of the second solder bumps 8.
  • another separation S2 of another neighbouring pair of the second solder bumps may be similar to, or even substantially larger than, the first separation Si of the neighbouring pair 20 of the first solder bumps 6.
  • Figure 5A shows a semiconductor chip 12 in a fourth embodiment according to the invention, having the first surface 4.
  • Figure 5B shows the semiconductor chip 12 in a cross section E-E', indicated in figure 5A.
  • the first surface 4 is provided with the first solder bumps 6 and the second solder bumps 8.
  • at least one of the second solder bumps 8 is located in between the first solder bumps 6.
  • Preferably at least half of, more preferably all of, the second solder bumps 8 are located in between the first solder bumps 6, for example in an interleaved fashion.
  • the first separation Si of the neighbouring pair 20 of the first solder bumps 6 may be larger than a third separation S3 of a neighbouring pair 24 of a first metal layer portion 6 of the first set and a second metal layer portion 8 of the second set.
  • the first metal layer portions here the first solder bumps 6, may be individually connected to the surface 4 in first contact areas 28.
  • the second metal layer portions, here the second solder bumps 8 may be individually connected to the surface 4 in second contact areas 30.
  • the first contact areas 28 may be substantially larger, for example at least 1.3 times larger or even at least two times larger, than the second contact areas 30.
  • the first and second contact areas may be formed by under-bump metallisation layer portions similar to the metallisation layer portions 8.
  • a general advantage of the semiconductor chip 12 is that it allows different versions of the semiconductor chip 12 to have a similar pattern of the first and second metal layer portions on the surface 4. As a result, electrical testing can be done without having to adjust testing hardware and/or a testing procedure. This allows for standardisation of the testing hardware.
  • the different versions may for example be arranged to use different functional blocks of the semiconductor chip 12, such as the different a/b/g/n versions of the 802.11 standard. Instead of leaving out several of the first solder bumps related to unused functional blocks, these can now be replaced by the second solder bumps. In this way, a reduction in contacting possibilities for the functional blocks can be prevented or at least reduced. This is important, as some, possibly used, functional blocks can only be reached through other, possibly unused, functional blocks.
  • the semiconductor chips in one of the first, second, third, and fourth embodiment may have features in common that are not described in that one embodiment, but are described for another one of the first, second, third, and fourth embodiment.
  • a first method of manufacturing a semiconductor chip in an embodiment of a method according to the invention, will be now be described with reference to figures 2A and 2B.
  • the first method includes applying the first set of first metal layer portion, in this example the first solder bumps 6, on the surface 4 of the semiconductor chip 12 with the first width Di along the surface 4.
  • the first method further includes applying the second set of second metal layer portions 8, in this example the metallisation layer portions 8, on the surface 4 with the second width D2 along the surface 4.
  • the first and second width are preferably measured in a direction substantially parallel with the plane of the surface 4, for example by using a microscope.
  • the first method may achieve the first and second metal layer portions being formed in mutual separation on the surface 4 of the semiconductor chip 12.
  • the first metal layer portions may be applied simultaneously with, or after, applying the second metal layer portions.
  • the metallisation layer portions 8 may be applied by electroless deposition of nickel, optionally followed by application of the thin gold coating by immersion deposition. Electroless deposition of nickel and immersion deposition of gold as such are known to the skilled person.
  • the first solder bumps 6 may be applied by screen printing a material containing solder through a mask, followed by reflowing the material. This process is especially suitable in case the width Di of the first solder bumps is larger than 180 micrometer.
  • the first solder bumps may be applied by photolithographic patterning and etching a solder layer, followed by reflowing. This process is especially suitable in case the width Di is smaller than 180 micrometer.
  • solder jetting a dispensing method such as ink jet printing, sometimes referred to as solder jetting, for depositing the first solder bumps.
  • Screen printing, photolithographic patterning and etching, and ink jet printing as such are known to the skilled person.
  • the second metal layer portions are applied as metallisation layer portions 8 and the first metal layer portions are applied as the first solder bumps 6, in accordance with the first method.
  • the first metal layer portions may be applied as first solder bumps and the second metal layer portions may be applied as second solder bumps, in accordance with a second method of manufacturing a semiconductor chip, in an embodiment of a method according to the invention.
  • the second solder bumps 8 of the semiconductor chip 12 in the second, third and fourth embodiment are applied in a similar way as the first solder bumps 6 are applied.
  • the second solder bumps 8 of the semiconductor chip 12 in the second, third and fourth embodiment are applied in the same process steps as the first solder bumps 6, preferably simultaneously with applying the first solder bumps 6.
  • the neighbouring pair 20 of the first metal layer portions may be applied with the first separation Si that either is larger than the second separation & at which the neighbouring pair 22 of the second metal layer portions 8 is applied, or is larger than the third separation S3 at which the neighbouring pair 24 of the first metal layer portion 6 of the first set and the second metal layer portion 8 of the second set are applied.
  • the first and second method may include applying the first solder bumps 6 with a first height Hi and applying the second solder bumps 8 with a second height H2, wherein the second height H2 is substantially smaller than the first height Hi.
  • a test method of testing a semiconductor chip in an embodiment of a method according to the invention, will be now be described.
  • the test method is, as an example, described for testing the semiconductor chip 12 in the second embodiment.
  • the test method includes testing the semiconductor chip 12 by using a testing apparatus provided with a group of mutually similar flexible measurement needles.
  • the measurement needles may extend towards, and end at or near, one and the same imaginary plane.
  • the test apparatus is known as such to the skilled person.
  • the test method includes moving the measurement needles towards the surface 4 for placing a first subgroup of the group of needles in electrical contact with the first solder bumps 6.
  • the test method further includes further moving the measurement needles towards the surface 4 for placing a second subgroup of the group of needles in contact with the second solder bumps 8, while maintaining electrical contacts between the first subgroup of needles and the first solder bumps, preferably established earlier.
  • the flexibility of the needles enables the maintenance of these electrical contacts, which is further supported by the needles ending at or near the same imaginary plane.

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Abstract

Semiconductor chip (12) having a surface (4) provided with a first set of mutually similar first metal layer portions (6) that have a first width along the surface (4). The surface is further provided with a second set of mutually similar second metal layer portions (8) that have a second width along the surface (4). Each first metal layer portion (6) forms an external functional contact surface (14) of the semiconductor chip(12). Each second metal layer portion (8) forms an external test contact surface (16) of the semiconductor chip (12). The second width is substantially smaller than the first width.

Description

SEMICONDUCTOR CHIP, METHOD OF MANUFACTURING A
SEMICONDUCTOR CHIP, AND METHOD OF TESTING A SEMICONDUCTOR CHIP.
DESCRIPTION
The invention relates to a semiconductor chip having a surface provided with a first set of mutually similar first metal layer portions having a first width along the surface. The invention further relates to a method of manufacturing a semiconductor chip, including applying a first set of first metal layer portions on a surface of a semiconductor chip with a first width along the surface. Furthermore, the invention relates to a method of testing a semiconductor chip by using a testing apparatus provided with a group of mutually similar flexible measurement needles. The invention also relates to an assembly of a semiconductor chip and an external substrate. The invention further relates to a product including a semiconductor chip. Furthermore, the invention relates to use of a semiconductor chip.
Semiconductor chips are provided with a plurality of external contact elements such as solder bumps, or layer portions that form contact pads for bonding wires thereon. A subgroup of the plurality of these contacting elements acts as functional contact elements to the semiconductor chip. In addition, these functional contact elements are normally used for electrical testing of the semiconductor chip as well. Such electrical testing can take place for quality assessment during manufacturing, or for failure analysis of semiconductor chips returned by customers. Usually, another subgroup of the contact elements is dedicated to testing only, without being needed for functionally contacting the semiconductor chip.
Semiconductor chips have shown a trend towards smaller feature sizes of circuitry on a semiconductor substrate of the semiconductor chip. As a result, a necessary number of external contact elements per unit of substrate area has increased as well. However, a size of the contact elements has stayed relatively constant. As a result, for many chip types the substrate area needed for placing the contact elements limits a minimum size of the semiconductor substrate, instead of the substrate area that is needed for placing active circuitry and test circuitry of the semiconductor chip. This in general leads to an increased substrate area, which is very costly.
One recent development is this field is the use of redistributive chip packaging, described in Keser, et al., "The Redistributive Chip Package: A Breakthrough for Advanced Packaging", 2007 Electronic Components and Technology Conference. The redistributive package for the semiconductor chip provides additional area for placing the contact elements. However, at least one additional layer for fan out structures from the circuitry of the semiconductor chip towards the contact elements is needed. Such a layer adds to cost and complexity of the packaged chip, thus increasing a probability for errors in manufacturing of the semiconductor chip and introducing reliability issues. Furthermore, the trend towards smaller feature sizes of the circuitry on the semiconductor chip is expected to continue, which may lead to an increasing amount of contact elements. As a result, a size of the redistributive package has to increase as well, which again increases cost and can also be expected to worsen the reliability issues. Accordingly, it is an object of the invention to provide a semiconductor chip with improved use of area on the semiconductor chip.
Thereto the invention provides a semiconductor chip having a surface provided with a first set of mutually similar first metal layer portions that have a first width along the surface, the surface further being provided with a second set of mutually similar second metal layer portions that have a second width along the surface, each first metal layer portion forming an external functional contact surface of the semiconductor chip, and each second metal layer portion forming an external test contact surface of the semiconductor chip, wherein the second width is substantially smaller than the first width. The first width being smaller than the second width enables an improved distribution of the first and second metal layer portions over the surface. Because of the smaller width of the second metal layer portions, part of the surface that is too small for placement of the first metal layer portion, may be used for placing the second metal layer portion. Additionally or alternatively, the smaller width of the second metal layer portions enables these to be applied on the surface in a higher number per unit of area of the surface than the first metal layer portions. In this way, a more efficient use of the surface can be achieved. Preferably, the second metal layer portions are distinct from the first metal layer portions. Preferably, the semiconductor chip in use is free of external electrical contact via the external test contact surface. Preferably, the external functional contact surface is arranged for electrically testing the semiconductor chip, for example for quality assessment during manufacturing of the semiconductor chip, or during failure analysis after use of the semiconductor chip. In this embodiment, the external functional contact surface may be arranged for both testing and functionally contacting the semiconductor chip. Optionally, the external test contact surface is arranged for electrical testing only.
It may be clear that the first set does not necessarily form all external functional contact surfaces of the semiconductor chip. However, in an embodiment, the first set does form all external functional contact surfaces of the semiconductor chip. It may be clear that the second set does not necessarily form all external test contact surfaces of the semiconductor chip. However, in an embodiment, the second set does form all external test contact surfaces of the semiconductor chip. The two latter embodiments in combination substantially maximize an efficiency of use of the surface.
In an embodiment, a first separation of a neighbouring pair of the first metal layer portions is larger than a second separation of a neighbouring pair of the second metal layer portions. Preferably, this holds for each neighbouring pair of the first metal layer portions, in comparison with one of the second metal layer portions, preferably in comparison with all of the second metal layer portions. Alternatively or additionally, in this embodiment the first separation of the neighbouring pair of the first metal layer portions is larger than a third separation of a neighbouring pair of a first metal layer portion of the first set and a second metal layer portion of the second set. In an important embodiment, the first metal layer portions have a first height and the second metal layer portions have a second height being substantially smaller than the first height. In this way, electrical and/or mechanical contact of the second metal layer portions with an external substrate, for example a printed circuit board, may be prevented. Preferably, the second height is at most 70% of the first height. This reliably prevents electrical and/or mechanical contact of the second metal layer portions with the external substrate. Preferably, the second height is at least 40% of the first height. In this way, a vertical probe apparatus with flexible needles for contacting the first and second metal layer portions, can still contact all of the first and second metal layer portions simultaneously. The second height being in a range from 40% to 70% of the first height combines these two advantages. According to an aspect of the invention, the inventors realised that, without being bound by the second width being smaller than the first width, it is advantageous to have the second metal layer portions being resistant against chemical and/or mechanical damage, while still being accessible for external electrical testing. The second metal layer portions may therefore be deposited on contact pads that do not have such resistance, i.e. directly on the last metallisation layer of f.i. aluminium. A testing surface of these contact pads is thus replaced by the external test contact surface. These contact pads would normally be used for testing, according to known testing methods.
In an embodiment, the second metal layer portions are formed by metallisation layer portions, for example electrolessly deposited nickel layer portions, possibly provided with a thin gold coating. The metallisation layer portions may be applied on the contact pads, that are normally used for testing, and that may be formed by the other layer portions that for example contain aluminium. The metallisation layer portions protect the contact pads during later process steps, for example against mechanical damage and/or against chemical degradation like corrosion of the other layer portions that form the contact pads. In addition, the metallisation layer portions may enable contacting the semiconductor chip while it is mounted, for example on a printed circuit board. In this way a surprising combination of protection and possibility for electrically contacting is achieved, as protection is normally achieved by applying an isolating material. Preferably, the first metal layer portions are formed by first solder bumps. This combines well with the second metal layer portions being formed by metallisation layer portions, as the first solder bumps may be deposited on under-bump metallisation layer portions that are similar to the metallisation layer portions. The metallisation layer portions and the under-bump metallisation layer portions, although preferably being distinct from each other, can be deposited in the same process steps. Alternatively, the first metal layer portions may be arranged for application of a wire thereon for wirebonding the semiconductor chip. For example, the first layer portions contain aluminium. Using metallisation layer portions, being similar to the under-bump metallisation portions, for wire-bonded chips is rather surprising, as under-bump metallisation layer portions are almost exclusively used in bumped chips, which are generally seen as an alternative to wire-bonded chips.
In an embodiment, the first metal layer portions are formed by first solder bumps and the second metal layer portions are formed by second solder bumps. Preferably, the first width equals a diameter of the first solder bumps. Preferably, the second width equals a diameter of the second solder bumps. The first solder bumps and/or the second solder bumps may be obtained after reflowing so that a curved surface is obtained under the influence of surface tension of a material of the first solder bumps and/or the second solder bumps. According to a further embodiment of the invention, the second metal portions have a surface area, when seen in a top view, with a length extending perpendicular to the width of the metal portions, wherein said width is smaller than said length. This embodiment is particularly advantageous when the second metal portions are located at one or more edges of the surface. The location of test surfaces along an edge enables contacting of the second metal layer via the external test contact surfaces after the semiconductor chip is applied to the printed circuit board. It also enables testing of the semiconductor chip during failure analysis of the semiconductor chip, without having to disassemble the semiconductor chip from the printed circuit board. In addition, repackaging of the semiconductor chip for making it fit on a test platform arranged for failure analysis, can be prevented.
Alternatively, at least one of the second metal layer portions is located in between the first metal layer portions. Preferably, the second metal layer portions are interposed between the second metal layer portions. Alternatively or additionally, the first metal layer portions and the second metal layer portion may be positioned in respectively a first pattern and a second pattern, which may overlap with the first pattern. Preferably, the first pattern and optionally the second pattern extend substantially over the whole surface, while the first and second layer portions are still separate from each other. These all form embodiments with improved efficiency of use of the surface.
In an embodiment, the first metal layer portions are individually connected to the surface in first areas, and the second metal layer portions are individually connected to the surface in second areas, wherein the first areas are substantially larger, preferably at least 1.3 times larger, than the second areas. This embodiment combines well with a manufacturing method wherein the first metal layer portions and the second metal layer portions are applied simultaneously in the same process step, optionally as one layer that is subsequently patterned to obtain mutually distinct first and second metal layer portions. The first areas being substantially larger than the second areas than ensures that an individual bump volume of the second metal layer portions is substantially smaller than an individual bump volume of the first metal layer portions. Preferably, the first and second areas are arranged for being constant during reflowing, The first and second areas may be defined as openings in a layer on which material of the first and/or second metal layer portions has a relatively large contact angle, deposited on top of a layer on which material of the first and/or second metal layer portions has a relatively small contact angle.
In an embodiment, the second metal layer portions are located along an edge of the surface.
It is also an object of the invention to provide a method of manufacturing a semiconductor chip with improved use of area on the semiconductor chip.
Thereto the invention provides a method of manufacturing a semiconductor chip, including the steps: a) applying a first set of first metal layer portions on a surface of a semiconductor chip with a first width along the surface, each first metal layer portion forming an external functional contact surface of the semiconductor chip! b) applying a second set of second metal layer portions on the surface with a second width along the surface, each second metal layer portion forming an external test contact surface of the semiconductor chip, wherein the second width is substantially smaller than the first width. In this way, a more efficient use of the surface can be achieved. Preferably, the second metal layer portions are distinct from the first metal layer portions. Preferably, the semiconductor chip in use is free of external electrical contact via the external test contact surface.
It is a further object of the invention to provide a method of testing a semiconductor chip with improved use of area on the semiconductor chip.
Thereto the invention provides a method of testing a semiconductor chip according to the invention or manufactured by a method according to the invention, by using a testing apparatus provided with a group of mutually similar flexible measurement needles, including the steps: c) moving the measurement needles towards the surface for placing a first subgroup of the group of needles in electrical contact with the first metal layer portions! and d) further moving the measurement needles towards the surface for placing a second subgroup of the group of needles in contact with the second metal layer portions, while maintaining electrical contacts established in step c). Such a testing method combines well with the semiconductor chip.
The invention also provides an assembly of an external substrate and a semiconductor chip according to the invention or manufactured by a method according to the invention, the external substrate having conductive circuitry and the semiconductor chip being assembled on the external substrate in electrical connection with the conductive circuitry via the external functional contact surface of the semiconductor chip, wherein the semiconductor chip is free of electrical connection with the conductive circuitry via the external test contact surface. The external substrate may be a printed circuit board. The conductive circuitry may include tracks and contact points of the printed circuit board.
The invention further provides a product including a semiconductor chip according to the invention or manufactured by a method according to the invention. The product can for example be a mobile phone, an automotive product such as a car, and/or a computer.
Furthermore, the invention provides use of a semiconductor chip according to the invention or manufactured by a method according to the invention, including functionally contacting the semiconductor chip via the external functional contact surface while the semiconductor chip in use is free of external electrical contact via the external test contact surface.
The invention will now be described, in a non-limiting way, with reference to the accompanying drawings, in which: Figure IA shows a known semiconductor chip! Figure IB shows a known semiconductor chip 2 in a cross section!
Figure 2A shows a semiconductor chip in a first embodiment according to the invention!
Figure 2B shows a semiconductor chip in a cross section! Figure 3B shows a semiconductor chip in a second embodiment according to the invention!
Figure 3B shows the semiconductor chip in a cross section!
Figure 4A shows a semiconductor chip in a third embodiment according to the invention! Figure 4B shows a semiconductor chip in a cross section.
Figure 5A shows a semiconductor chip in a fourth embodiment according to the invention! and
Figure 5B shows a semiconductor chip in a cross section.
Unless stated otherwise, the same reference numbers refer to like components throughout the drawings.
Figure IA shows a known semiconductor chip 2 having a surface 4. Figure IB shows the known semiconductor chip 2 in a cross section A-A', indicated in figure IA. The surface 4 is provided with a first set of mutually similar first metal layer portions, in this case first solder bumps 6, that have a first width Di, in this case a diameter, along the surface 4. The surface 4 is further provided with a second set of mutually similar second metal layer portions, in this case second solder bumps 8. In the known semiconductor chip 2, the diameter of the second solder bumps 8 along the surface 4 is similar to
Figure 2A shows a semiconductor chip 12 in a first embodiment according to the invention. Figure 2B shows the semiconductor chip 12 in a cross section B-B', indicated in figure 2A. The semiconductor chip 12 has the surface 4 provided with the first set of mutually similar first metal layer portions 6, in this example being formed by the first solder bumps 6, that have the first width Di along the surface 4. The surface 4 may be formed by a fan out layer arranged for electrically connecting circuitry of the semiconductor chip 12 towards the first solder bumps 6. Such a fan-out layer as such is known to the skilled person. Additionally or alternatively, the surface 4 may be formed by a silicon substrate 13 of the semiconductor chip 12, or by one or more layers (not drawn) deposited on the silicon substrate 13.
The surface 4 is further provided with the second set of mutually similar second metal layer portions that have a second width D2 along the surface 4, i.e. in a direction substantially parallel with a plane of the surface 4. In the first embodiment, the second metal layer portions may be formed by metallisation layer portions 8. The metallisation layer portions 8 may be applied by electroless deposition of nickel, optionally followed by immersion deposition of a thin gold coating. A first height Hi of the metallisation layer portions may be in a range from 1 to 10 micrometer, for example 3 micrometer. A thickness of the thin gold coating may be several tens of nanometers.
Each first solder bump 6 individually forms an external functional contact surface 14 of the semiconductor chip 12. As a result, the semiconductor chip 12 may be provided with a plurality of external functional contact surfaces 14. The external functional contact surfaces 14 enable, in use, guiding of electrical input signals and electrical output signal respectively to and from the semiconductor chip 12. In addition, some of the first solder bumps 6, preferably all first solder bumps 6, can be used for electrically testing the semiconductor chip 12, for example during failure analysis. Each metallisation layer portion 8 individually forms an external test contact surface 16 of the semiconductor chip 12. As a result, the semiconductor chip 12 may be provided with a plurality of external test contact surfaces 16. It will be appreciated that the external test contact surfaces 16 may not need to be contacted for normal operation of the semiconductor chip 12. Thus, in use, the semiconductor chip 12 may be free of external electrical contact via the external test contact surfaces 16. Preferably, in use, external electrical contact of the semiconductor chip 12 is exclusively via the external functional contact surfaces 14.
The second width D2 is substantially smaller than the first width Di. The width of the first metal layer portions may mutually vary for example at most 5% or at most 10%. Analogously, the width of the second metal layer portions may mutually vary for example at most 5% or at most 10%. Such variations may be inherent to a manufacturing method of the first and second metal layer portions, for example a stochastic and/or systematic variation therein. However, such variation may not lead to one of the first metal layer portions 6 having a substantially smaller width than another one of the first metal layer portions 6. In general, the second width D2 may be at most 70%, preferably at most 40%, of the first width Di. In this way, a significant improvement in use of the surface 4 is achieved. In general, the width Di may be in a range from 40 to 500 micrometer, for example 300 micrometer. The second width D2 may be in a range from 60 to 80 micrometer.
A first separation Si of a neighbouring pair 20 of the first solder bumps 6 may be larger than a second separation S2 of a neighbouring pair 22 of the metallisation layer portions 8. The first separation Si of the neighbouring pair 20 of the first solder bumps 6, may be measured from a center of a first one to a center of a second one of the neighbouring pair 20 of the first solder bumps 6. The second separation S2 of the neighbouring pair 22 of the metallisation layer portions 8, may be measured from a center of a first one to a center of a second one of the neighbouring pair 22 of the metallisation layer portions 8. For a wafer-level chip scale package, the first separation Si is typically in a range from 300 to 500 micrometer, for example 400 micrometer or 500 micrometer or a value between 400 and 500 micrometer. The first set and second set together typically include a total number of metal layer portions that is in a range from 64 to 144, although the total number of metal layer portion may be above or below this range. In the first embodiment, the metallisation layer portions 8 are located along an edge 23 of the surface 4. When using the known semiconductor chip 2 of figures IA and IB, electrical testing for failure analysis requires disassembling the known semiconductor chip 2 from the printed circuit board in order to make the first metal layer portions 6 accessible. However, having the metallisation layer portions 8 located along the edge 23 enables contacting the semiconductor chip 12 in the first embodiment without having to disassemble the semiconductor chip 12 from the printed circuit board, in case electrical leads to the first metal layer portions are accessible through the second metal layer portions.
Figure 3A shows a semiconductor chip 12 in a second embodiment according to the invention. Figure 3B shows the semiconductor chip 12 in a cross section C-C, indicated in figure 3A. The semiconductor chip 12 has the surface 4 provided with the first solder bumps 6. In the second embodiment, the second metal layer portions are formed by second solder bumps 8. The width D2 of the second solder bumps 8 along the surface 4 is substantially smaller than the width Di of the first solder bumps 6 along the surface 4.
The first metal layer portions, in this example the first solder bumps 6, have the first height Hi and the second metal layer portions, in this example the second solder bumps 8, have a second height H2 being substantially smaller than the first height Hi. Analogously to the first and second width, a mutual variation of for example at most 5% or at most 10% in the first and second heights is not considered as causing the second height H2 to be substantially smaller than the first height Hi. The second height my at least be 40% and/or at most 70% of the first height. In this embodiment, the first height Hi may be similar to the first width Di.
In general, an individual bump volume of the second solder bumps 8 may be substantially smaller than an individual bump volume of the first solder bumps 6. The individual bump volume of the first solder bumps 6 is related to the width Di and the height Hi of the first solder bumps 8. The individual bump volume of the second solder bumps 6 is related to the width D2 and the height H2 of the second solder bumps 8. A third width along the surface 4 measured in a direction transverse to a direction in which the second width D2 is measured, is also related to the individual bump volume of the second solder bumps 8. In the second embodiment, the third width D3 is similar to the first width Di. In this case, the individual bump volume of the second solder bumps 8 being substantially smaller than the individual bump volume of the first solder bumps 6 ensures the second width D2 to be substantially smaller than the first width Di or the second height Hi to be substantially smaller than the first height H2. However, the third width D3 may be similar to the second width D2 in other embodiments, for example the fourth embodiment.
Figure 4A shows a semiconductor chip 12 in a third embodiment according to the invention. Figure 4B shows the semiconductor chip 12 in a cross section D-D', indicated in figure 4A. The semiconductor chip 12 has the surface 4 provided with the first solder bumps 6 and the second solder bumps 8. The width D2 of the second solder bumps 8 is substantially smaller than the width Di of the first solder bumps 6. The first separation Si of the neighbouring pair 20 of the first solder bumps 6 may be larger than the second separation S2 of the neighbouring pair 22 of the second solder bumps 8. However, in the third embodiment another separation S2 of another neighbouring pair of the second solder bumps may be similar to, or even substantially larger than, the first separation Si of the neighbouring pair 20 of the first solder bumps 6. Figure 5A shows a semiconductor chip 12 in a fourth embodiment according to the invention, having the first surface 4. Figure 5B shows the semiconductor chip 12 in a cross section E-E', indicated in figure 5A. The first surface 4 is provided with the first solder bumps 6 and the second solder bumps 8. In the fourth embodiment, at least one of the second solder bumps 8 is located in between the first solder bumps 6. Preferably at least half of, more preferably all of, the second solder bumps 8 are located in between the first solder bumps 6, for example in an interleaved fashion. The first separation Si of the neighbouring pair 20 of the first solder bumps 6 may be larger than a third separation S3 of a neighbouring pair 24 of a first metal layer portion 6 of the first set and a second metal layer portion 8 of the second set.
The first metal layer portions, here the first solder bumps 6, may be individually connected to the surface 4 in first contact areas 28. The second metal layer portions, here the second solder bumps 8, may be individually connected to the surface 4 in second contact areas 30. The first contact areas 28 may be substantially larger, for example at least 1.3 times larger or even at least two times larger, than the second contact areas 30. The first and second contact areas may be formed by under-bump metallisation layer portions similar to the metallisation layer portions 8.
A general advantage of the semiconductor chip 12 is that it allows different versions of the semiconductor chip 12 to have a similar pattern of the first and second metal layer portions on the surface 4. As a result, electrical testing can be done without having to adjust testing hardware and/or a testing procedure. This allows for standardisation of the testing hardware. The different versions may for example be arranged to use different functional blocks of the semiconductor chip 12, such as the different a/b/g/n versions of the 802.11 standard. Instead of leaving out several of the first solder bumps related to unused functional blocks, these can now be replaced by the second solder bumps. In this way, a reduction in contacting possibilities for the functional blocks can be prevented or at least reduced. This is important, as some, possibly used, functional blocks can only be reached through other, possibly unused, functional blocks.
It is noted that the semiconductor chips in one of the first, second, third, and fourth embodiment may have features in common that are not described in that one embodiment, but are described for another one of the first, second, third, and fourth embodiment. A first method of manufacturing a semiconductor chip, in an embodiment of a method according to the invention, will be now be described with reference to figures 2A and 2B. The first method includes applying the first set of first metal layer portion, in this example the first solder bumps 6, on the surface 4 of the semiconductor chip 12 with the first width Di along the surface 4. The first method further includes applying the second set of second metal layer portions 8, in this example the metallisation layer portions 8, on the surface 4 with the second width D2 along the surface 4. The first and second width are preferably measured in a direction substantially parallel with the plane of the surface 4, for example by using a microscope. The first method may achieve the first and second metal layer portions being formed in mutual separation on the surface 4 of the semiconductor chip 12.
In general, the first metal layer portions may be applied simultaneously with, or after, applying the second metal layer portions. The metallisation layer portions 8 may be applied by electroless deposition of nickel, optionally followed by application of the thin gold coating by immersion deposition. Electroless deposition of nickel and immersion deposition of gold as such are known to the skilled person. The first solder bumps 6 may be applied by screen printing a material containing solder through a mask, followed by reflowing the material. This process is especially suitable in case the width Di of the first solder bumps is larger than 180 micrometer. Alternatively, the first solder bumps may be applied by photolithographic patterning and etching a solder layer, followed by reflowing. This process is especially suitable in case the width Di is smaller than 180 micrometer. Another possibility is to use a dispensing method such as ink jet printing, sometimes referred to as solder jetting, for depositing the first solder bumps. Screen printing, photolithographic patterning and etching, and ink jet printing as such are known to the skilled person.
In the semiconductor chip 12 in the first embodiment, the second metal layer portions are applied as metallisation layer portions 8 and the first metal layer portions are applied as the first solder bumps 6, in accordance with the first method.
In the semiconductor chip 12 in the second, third, and fourth embodiment, the first metal layer portions may be applied as first solder bumps and the second metal layer portions may be applied as second solder bumps, in accordance with a second method of manufacturing a semiconductor chip, in an embodiment of a method according to the invention. Preferably, in the second method, the second solder bumps 8 of the semiconductor chip 12 in the second, third and fourth embodiment, are applied in a similar way as the first solder bumps 6 are applied. Preferably, the second solder bumps 8 of the semiconductor chip 12 in the second, third and fourth embodiment, are applied in the same process steps as the first solder bumps 6, preferably simultaneously with applying the first solder bumps 6.
With reference to figures 2A, 4A, and 5A, in the first and second method the neighbouring pair 20 of the first metal layer portions may be applied with the first separation Si that either is larger than the second separation & at which the neighbouring pair 22 of the second metal layer portions 8 is applied, or is larger than the third separation S3 at which the neighbouring pair 24 of the first metal layer portion 6 of the first set and the second metal layer portion 8 of the second set are applied.
With reference to figure 3B, the first and second method may include applying the first solder bumps 6 with a first height Hi and applying the second solder bumps 8 with a second height H2, wherein the second height H2 is substantially smaller than the first height Hi. A test method of testing a semiconductor chip, in an embodiment of a method according to the invention, will be now be described. The test method is, as an example, described for testing the semiconductor chip 12 in the second embodiment. The test method includes testing the semiconductor chip 12 by using a testing apparatus provided with a group of mutually similar flexible measurement needles. The measurement needles may extend towards, and end at or near, one and the same imaginary plane. The test apparatus is known as such to the skilled person. The test method includes moving the measurement needles towards the surface 4 for placing a first subgroup of the group of needles in electrical contact with the first solder bumps 6. The test method further includes further moving the measurement needles towards the surface 4 for placing a second subgroup of the group of needles in contact with the second solder bumps 8, while maintaining electrical contacts between the first subgroup of needles and the first solder bumps, preferably established earlier. The flexibility of the needles enables the maintenance of these electrical contacts, which is further supported by the needles ending at or near the same imaginary plane.
The invention is not limited to any embodiment herein described and, within the purview of the skilled person, modifications are possible which may be considered within the scope of the appended claims. Equally all kinematic inversions are considered inherently disclosed and to be within the scope of the present invention. The use of expressions like: "preferably", "in especially", "typically", etc. is not intended to limit the invention. The indefinite article "a" or "an" does not exclude a plurality. Features which are not specifically or explicitly described or claimed may be additionally included in the structure according to the present invention without deviating from its scope.

Claims

1. Semiconductor chip having a surface provided with a first set of mutually similar first metal layer portions that have a first width along the surface, the surface further being provided with a second set of mutually similar second metal layer portions that have a second width along the surface, each first metal layer portions forming an external functional contact surface of the semiconductor chip, and each second metal layer portion forming an external test contact surface of the semiconductor chip, wherein the second width is substantially smaller than the first width.
2. Semiconductor chip according to claim 1, wherein the second width is at most 70%, preferably at most 40%, of the first width.
3. Semiconductor chip according to one of claims 1-2, wherein the first metal layer portions have a first height and the second metal layer portions have a second height being substantially smaller than the first height.
4. Semiconductor chip according to claim 3, wherein the second height is at least 40% and/or at most 70% of the first height.
5. Semiconductor chip according to one of claims 1-4, wherein the second metal layer portions are constituted of metallisation layer portions extending through apertures in a chip passivation layer, whereas first solder bumps constitute the first metal layer portions.
6. Semiconductor chip according to one of claims 1-4, wherein the first metal layer portions are formed by first solder bumps and the second metal layer portions are formed by second solder bumps.
7. Semiconductor chip according to one of claims 1-6, wherein the second metal layer portions have a length along the surface extending perpendicular to the width, wherein said width is smaller than the length.
8. Method of manufacturing a semiconductor chip, including the steps: a) applying a first set of first metal layer portions on a surface of a semiconductor chip with a first width along the surface, each first metal layer portion forming an external functional contact surface of the semiconductor chip! b) applying a second set of second metal layer portions on the surface with a second width along the surface, each second metal layer portion forming an external test contact surface of the semiconductor chip, wherein the second width is substantially smaller than the first width.
9. Method according to claim 8, wherein a neighbouring pair of the first metal layer portions is applied in step a) with a first separation that either is larger than a second separation at which a neighbouring pair of the second metal layer portions is applied in step b) or that is larger than a third separation at which a neighbouring pair of a first metal layer portion of the first set and a second metal layer portion of the second set is applied in steps a) and b).
10. Method according to claim 8 or 9, wherein step a) includes applying the first metal layer portions with a first height and step b) includes applying the second metal layer portions with a second height, wherein the second height is substantially smaller than the first height.
11. Method according to one of claims 8-10, wherein in step b) the second metal layer portions are applied as metallisation layer portions and optionally in step b) the first metal layer portions are applied as first solder bumps.
12. Method according to one of claims 8-10, wherein in step a) the first metal layer portions are applied as first solder bumps and in step b) the second metal layer portions are applied as second solder bumps.
13. Method of testing a semiconductor chip according to one of claims 1- 7 or manufactured by a method according to one of claims 8-12, by using a testing apparatus provided with a group of mutually similar flexible measurement needles, including the steps: c) moving the measurement needles towards the surface for placing a first subgroup of the group of needles in electrical contact with the first metal layer portions! and d) further moving the measurement needles towards the surface for placing a second subgroup of the group of needles in contact with the second metal layer portions, while maintaining electrical contacts established in step c).
14. Assembly of an external substrate, and a semiconductor chip according to one of claims 1-7 or obtainable by a method according to one of claims 8-12, the external substrate having conductive circuitry and the semiconductor chip being assembled on the external substrate in electrical connection with the conductive circuitry via the external functional contact surface of the semiconductor chip, wherein the semiconductor chip is free of electrical connection with the conductive circuitry via the external test contact surface.
15. Use of a semiconductor chip according to one of claims 1-7 or obtainable by a method according to one of claims 8-12, including functionally contacting the semiconductor chip via the external functional contact surface while the semiconductor chip in use is free of external electrical contact via the external test contact surface.
PCT/IB2009/054610 2008-10-31 2009-10-20 Semiconductor chip, method of manufacturing a semiconductor chip, and method of testing a semiconductor chip WO2010049846A2 (en)

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