Image sensor comprising a curved sensor chip and method of manufacturing the image sensor

Abstract

An image sensor (10) comprises a carrier (100) having a curved surface portion (101), an opening (105) extending from the curved surface portion (101) to a second main surface (102) of the carrier (100). The image sensor (10) further comprises a curved sensor chip (110) arranged in the curved surface portion (101), a second main surface (112) of the curved sensor chip (110) being adjacent to the curved surface portion (101), and an electrical contact element (107) arranged in the opening (105) and extending from the curved surface portion (101) to the second main surface (102) of the carrier (100).

Description

[0001] IMAGE SENSOR COMPRISING A CURVED SENSOR CHIP AND METHOD OF MANUFACTURING THE IMAGE SENSOR

[0002] The present disclosure relates to an image sensor compri sing a curved sensor chip and to a method of manufacturing the image sensor .

[0003] Image sensors for use e . g . in an imaging device such as a camera, a mobile phone camera, a consumer electronic camera, a surveillance video camera or an automotive driver assistance device usually receive electromagnetic radiation having a curved wave front . Therefore , attempts are being made to provide an image sensor comprising a curved semiconductor sensor chip .

[0004] Generally, attempts are being made to provide an improved image sensor and to provide an improved method for manufacturing an image sensor .

[0005] SUMMARY

[0006] An image sensor comprises a carrier having a curved surface portion . An opening extends from the curved surface portion to a second main surface of the carrier . The image sensor further comprises a curved sensor chip arranged in the curved surface portion, a second main surface of the curved sensor chip being adj acent to the curved surface portion . The image sensor still further comprises an electrical contact element arranged in the opening and extending from the curved surface portion to the second main surface to the sensor chip .

[0007] For example , the curved surface portion is formed in a first main surface of the carrier opposite to the second main surface of the carrier . According to embodiments , the image sensor further comprises a contact opening formed in the second main surface of the curved sensor chip .

[0008] The contact opening may be arranged adj acent to the opening arranged in the carrier .

[0009] The image sensor may further comprise an anisotropic conductive film between the carrier and the curved sensor chip .

[0010] According to further embodiments , the image sensor further comprises an anisotropic conductive paste or a solder ball between the carrier and the curved sensor chip .

[0011] The image sensor may further comprise a lens over the first main surface of the curved sensor chip .

[0012] According to embodiments , a method of manufacturing an image sensor comprises forming a curved surface portion in a first main surface of a carrier and forming an opening extending from the curved surface portion to a second main surface of the carrier . The method further comprises forming an electrical contact element in the opening, the electrical contact element extending from the curved surface portion to the second main surface of the carrier . The method further comprises arranging a flat sensor chip in the curved surface portion, and applying pressure and heat so that a second main surface of the curved sensor chip is adj acent to the curved surface portion .

[0013] The method may further comprise applying an anisotropic conductive film in the curved surface portion after forming the electrical contact element and before arranging the flat sensor chip in the curved surface portion .

[0014] According to further embodiments , the method further comprises applying an anisotropic conductive paste or placing solder balls in the curved surface portion after forming the electrical contact element and before arranging the flat sensor chip in the curved surface portion .

[0015] The method may further comprise thinning the flat sensor chip to a thickness less than 100 pm before arranging the flat sensor chip in the curved surface portion .

[0016] For example , a contact opening may be formed in the second main surface of the sensor chip before arranging the sensor chip in the curved surface portion .

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this speci fication . The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles . Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description . The elements of the drawings are not necessarily to scale relative to each other . Like reference numbers designate corresponding similar parts .

[0019] Fig . 1A shows a cross-sectional view of an image sensor according to embodiments . Fig. IB shows a cross-sectional view of an image sensor according to further embodiments.

[0020] Fig. 1C shows an exploded perspective view of an image sensor according to embodiments.

[0021] Figs. 2A to 2H illustrate processes for manufacturing a lidless thin sensor chip.

[0022] Figs. 3A to 3F illustrate processes for forming a carrier having a curved surface portion.

[0023] Figs. 4A to 4D illustrate cross-sectional views of a carrier when performing a method of manufacturing an image sensor according to embodiments.

[0024] Figs. 5A to 5D illustrate cross-sectional views of a carrier when performing a method for manufacturing an image sensor.

[0025] Figs. 6A to 6D show cross-sectional views of a carrier when performing a method for manufacturing an image sensor according to embodiments.

[0026] Fig. 7 summarizes a method according to embodiments.

[0027] DETAILED DESCRIPTION

[0028] In the following detailed description reference is made to the accompanying drawings, which form a part hereof and in which are illustrated by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology such as "top", "bottom", "front", "back", "over", "on", "above", "leading", "trailing" etc. is used with reference to the orientation of the Figures being described. Since components of embodiments of the invention can be positioned in a number of di f ferent orientations , the directional terminology is used for purposes of illustration and is in no way limiting . It is to be understood that other embodiments may be utili zed and structural or logical changes may be made without departing from the scope defined by the claims .

[0029] The description of the embodiments is not limiting . In particular, elements of the embodiments described hereinafter may be combined with elements of di f ferent embodiments .

[0030] The terms " lateral" and "hori zontal" as used in this speci fication intends to describe an orientation parallel to a first surface of a substrate or semiconductor body . This can be for instance the surface of a wafer or a die .

[0031] The term "vertical" as used in this speci fication intends to describe an orientation which is arranged perpendicular to the first surface of a substrate or semiconductor body .

[0032] As employed in thi s speci fication, the terms "coupled" and / or "electrically coupled" are not meant to mean that the elements must be directly coupled together - intervening elements may be provided between the "coupled" or "electrically coupled" elements . The term "electrically connected" may describe a low- ohmic electric connection between the elements electrically connected together .

[0033] According to further embodiments and where appropriate , the term "electrically connected" may mean that the respective elements are "directly connected" or are "directly and permanently connected" . Fig . 1A shows a cross-sectional view of an image sensor 10 according to embodiments . The image sensor 10 comprises a carrier 100 having a curved surface portion 101 . An opening 105 extends from the curved surface portion 101 to a second main surface 102 of the carrier 100 . The image sensor 10 further comprises a curved sensor chip 110 that is arranged in the curved surface portion 101 . A second main surface 112 of the curved sensor chip 110 is adj acent to the curved surface portion 101 . The image sensor further comprises an electrical contact element 107 which is arranged in the opening 105 and which extends from the second main surface 102 to the sensor chip 110 .

[0034] The curved sensor chip 110 comprises an optoelectronic semiconductor device and may comprise a photodiode or any other semiconductor device configured to absorb electromagnetic radiation . In particular, a first main surface 111 of the curved sensor chip 110 may be sensitive to electromagnetic radiation 15 . For example , the photodiode region of the curved sensor chip 110 may be arranged adj acent to the first main surface 111 of the curved sensor chip 110 . By way of example , the curved sensor chip 110 may be implemented as a CMOS ("complementary metal- oxide semiconductor" ) sensor device or may be implemented as a CCD ("charge-coupled device" ) . For example , peripheral circuitry or a sensor circuit 113 may be arranged in the curved sensor chip 110 . The sensor circuit 113 may comprise e . g . a trans fer transistor, a reset transistor, a floating di f fusion and further components which are commonly used in a CMOS image sensor .

[0035] The curved sensor chip 110 may be a semiconductor chip and may e . g . comprise silicon or any other suitable material for implementing a sensor chip . Photodiodes or light-absorbing elements and the sensor circuit 113 may be integrated in the curved sensor chip 110 . A second main surface 112 of the curved sensor chip 110 is adj acent to the curved surface portion 101 . In the context of the present speci fication, the term "adj acent" is intended to mean "neighboring" . In particular, the second main surface 112 of the curved sensor chip 110 does not need to be directly adj acent to the curved surface portion 101 . For example , a conductive material may be arranged between the second main surface 112 of the curved sensor chip 110 and the curved surface portion 101 of the carrier 100 .

[0036] As is further illustrated in Fig . 1A, the contact element 107 extends from the curved surface portion 101 to the second main surface 102 of the carrier 100 . A contact pad 108 may be arranged at the second main surface 102 of the carrier 100 . Further, a contact opening 114 may be formed in the second main surface 112 of the sensor chip . A wiring element 115 may be arranged in the opening 114 . The wiring element 115 may e . g . be configured to electrically connect the sensor circuit 113 or components of the sensor circuit 113 to the contact pad 108 . For example , the opening 105 arranged in the carrier 100 may be disposed adj acent or directly adj acent to the contact opening 114 in the curved sensor chip 110 . In thi s manner, an electrical contact between the electrical contact element 107 and the wiring element 115 may be accomplished .

[0037] Fig . IB shows a cross-sectional view of the image sensor 10 according to further embodiments . As is shown, in addition to elements that are illustrated in Fig . 1A, the image sensor 10 further comprises a lens 120 which is arranged over the first main surface 111 of the sensor chip 110 . The lens 120 or any other optical elements may be used for focusing or shaping electromagnetic radiation 15 which is incident on the image sensor 10 . The lens 120 may be attached via spacers 121 that are attached to the carrier 100 . In this manner, the combination of carrier 100 , lens spacer 121 and lens 120 establishes a housing 122 for the image sensor 10 .

[0038] Fig . 1C shows an exploded perspective view of elements of the image sensor 10 illustrated in Fig . IB . As is shown, the carrier 100 comprises a curved surface portion 101 . Openings 105 are arranged in the curved surface portion 101 . Further, a lens 120 is placed over the curved surface portion 101 . A second main surface 112 of the sensor chip is arranged adj acent to the curved surface portion 101 . A lens 120 and a lens spacer 121 are placed over the curved sensor chip 110 .

[0039] As has been illustrated with reference to Figs . 1A to 1C , the image sensor 10 implements an image sensor 10 comprising a curved sensor chip 110 . Moreover, electrical contacts are arranged in openings 105 which extend from the curved surface portion 101 to the second main surface 102 of the carrier 100 . Accordingly, interconnections to the curved sensor chip 110 are accomplished by TSVs ( " through-silicon via" ) . As a consequence , connections may be reliably accomplished while reducing the package si ze . In more detail , the curved sensor chip 110 now is packaged in a chip-scale package ("CSP" ) .

[0040] In the following, methods for manufacturing the image sensor will be explained .

[0041] Referring to Figs . 2A to 2H, a method for preparing a sensor chip will be explained . A sensor wafer 124 comprising a plurality of flat sensor chips including sensor elements , e . g . photodiodes , and sensor circuitry 113 is attached to a suitable handling carrier 130 . For example , the handling carrier 130 may comprise glass or any other suitable material . A first main surface 111 of the sensor wafer 124 is attached to the handling carrier 130 ( Fig . 2A) . Thereafter, a thinning process is performed so as to reduce the thickness of the sensor wafer 124. For example, a resulting thickness of the sensor wafer 124 may be less than 100 pm or even less than 20 pm or less than 10 pm, depending on the size of the sensor elements. Fig. 2B shows an example of a resulting workpiece 20.

[0042] Thereafter, contact openings 114 are formed in the second main surface 112 of the sensor wafer 124. For example, the contact openings 114 may extend to a sensor circuit (not shown in Fig. 2C) . The contact opening 114 may be formed by etching. Fig. 2C shows an example of a resulting workpiece 20.

[0043] Then, as is illustrated in Fig. 2D, wiring elements 115 are formed in the contact openings 114.

[0044] Referring to Fig. 2E, the resulting workpiece 20 is placed on a suitable mount 131. Thereafter, a carrier debonding is performed so as to remove the handling carrier 130. Fig. 2F shows an example of a resulting workpiece 20.

[0045] Thereafter, referring to Fig. 2G, a singulating process, e.g. a dicing process is performed so as to singulate the single sensor chips 125. Thereafter, the single flat sensor chips 125 may be picked up by a pickup head 132. As is shown in Fig. 2H, the flat sensor chip 125 may be removed from the mount 131.

[0046] Figs. 3A to 3F illustrate processes for preparing a carrier 100. Fig. 3A shows a cross-sectional view of a carrier 100 having a first and a second main surface 103, 102. For example, the carrier may be made of a mechanically stable and insulating material. Examples comprise glass, aluminium oxide, AIN, SiC or a liquid crystal polymer. As is illustrated in Fig. 3B, curved surface portions 101 are formed in the first main surface 103 of the carrier 100. For example, this may be accomplished by CNC ("computerized numerical control") machining or by molding. For example, this process may be performed so that protruding portions 109 of the carrier material are arranged between adjacent curved surface portions 101. Further, openings 105 are formed in the curved surface portion 101. The openings 105 extend to the second main surface 102. For example, the openings 105 may be formed by drilling. The openings 105 do not need to extend at an angle of 90° .

[0047] Thereafter, as is illustrated in Fig. 3D, the openings 105 may be filled with a conductive material to form electrical contact elements 107. For example, contact pads 108 may be formed adjacent to the second main surface 102 of the carrier. Fig. 3D shows an example of a resulting carrier 100.

[0048] Fig. 3E shows a top view on the curved surface portion 101. Fig.

[0049] 3F shows a back side view of the second main surface 102 of the carrier 100.

[0050] The next Figures illustrate a method of assembling the flat sensor chip 125 on the curved carrier 100. The following figures further show the process of electrically connecting the elements of the sensor chip 125 to the contact pad 108.

[0051] As is illustrated in Fig. 4A, for example, an anisotropic conductive film 116 may be formed over the curved surface portion 101. The term "anisotropic conductive film" is intended to define a film which may be electrically conductive in a first direction, e.g. the vertical direction and which is not electrically conductive in a horizontal or nearly horizontal direction. In this way, along a vertical direction, an electrical connection may be accomplished whereas a lateral isolation is provided .

[0052] Fig . 4B shows a membrane 133 that is placed over the workpiece 20 . Further, air pressure is applied so that the anisotropic conductive film 116 is attached to the curved surface portion 101 of the carrier 100 . The membrane 133 is used for providing a uni form pressure . According to embodiments , the membrane 133 may be dispensed with .

[0053] Then, as is illustrated in Fig . 4C , the flat sensor chips 125 are placed over the anisotropic conductive film 116 arranged in the curved surface portions 101 . The flat sensor chips 125 are placed so that the wiring element 115 faces the curved surface portion 101 of the carrier 100 . In particular, the flat sensor chip 125 is placed so that the wiring element 115 faces the electrical contact element 107 arranged in the carrier 100 .

[0054] Further, as is illustrated in Fig . 4D, a membrane 133 may be placed over the workpiece 20 . Thereafter, pressure and heat may be applied so that the sensor chip is curved . As is further illustrated in Fig . 4D, the anisotropic conductive element 116 is placed between the curved sensor chip 110 and the carrier 100 so that an electrical contact is accomplished between the wiring element 115 and the electrical contact element 107 in the carrier 100 .

[0055] According to further embodiments , instead of an anisotropic conductive film 116 , an anisotropic conductive paste 117 may be employed . This will be explained with reference to Figs . 5A to 5D .

[0056] As is shown in Fig . 5A, the anisotropic conductive paste 117 may be applied to the curved surface portion 101 , e . g . using a dispenser. Thereafter, in a similar manner as has been explained with reference to Fig. 4C, the flat sensor chip 125 is placed over the anisotropic conductive paste 117 (Fig. 5B) .

[0057] As is shown in Fig. 5C, for example, a membrane 133 may be arranged over the carrier 100 and the flat sensor chips 125. Pressure and heat may be applied as is illustrated in Fig. 5D. As a result, the sensor chips 110 are curved. Moreover, the wiring elements 115 are brought into electrical contact with the electrical contact element 107. In this way, the wiring element 115 and thus, the sensor circuit 113 is electrically connected to the contact pad 108 which is arranged on the second main surface of the carrier 100.

[0058] According to further embodiments, an electrical contact between the wiring element 115 and the electrical contact element 107 may be accomplished using solder balls 118. This will be explained while referring to Figs. 6A to 6D.

[0059] As is illustrated in Fig. 6A, a flux 134 may be applied to the electrical contact elements in the carrier via the curved surface portion 101. Thereafter, as is illustrated in Fig. 6B, the flat sensor chips 125 are placed over the curved surface portion 101 in a similar manner as has been explained with reference to Fig. 5B.

[0060] Thereafter, a membrane 133 may be arranged over the workpiece 20, as is illustrated in Fig. 6C. As is illustrated in Fig. 6D, then, in a similar manner as has been explained with reference to Figs. 4D and 5D, pressure and heat are applied in order to provide curved sensor chips 110 and to provide an electrical contact between the wiring element 115 and the contact element 107 in the carrier 100. The workpiece 20 obtained e.g. in Figs. 4D, 5D and 6D may be singulated into single image sensors 10 or chip-scale packages. For example, this may be accomplished using dicing along the protruding portions 109.

[0061] Fig. 7 summarizes a method according to embodiments. As is shown, a method of manufacturing an image sensor comprises forming (S100) a curved surface portion in a first main surface of a carrier. The method further comprises forming (S110) an opening extending from the curved surface portion to a second main surface of the carrier. The method further comprises forming (S120) an electrical contact element in the opening, the electrical contact element extending from the curved surface portion to the second main surface of the carrier. The method further comprises arranging (S130) a flat sensor chip in the curved surface portion, and applying (S140) pressure and heat so that a second main surface of the curved sensor chip is adjacent to the curved surface portion.

[0062] The method described provides a method to form a curved image sensor in a low-cost and miniature package. Further, electrical contacts are provided in a compact manner. As a result, a chipscale image sensor having a curved surface may be provided. As a further consequence, it becomes possible to greatly simplify an optical stack of a camera so that height in a vertical direction may be gained. Since the curved image sensor may be manufactured in a chip-scale package (CSP) , the image sensor may be very compact and the cost of packaging may be lowered.

[0063] While embodiments of the invention have been described above, it is obvious that further embodiments may be implemented. For example, further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above. Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein .

[0064] LIST OF REFERENCES image sensor electromagnetic radiation workpiece carrier curved surface portion second main surface of carrier first main surface of carrier opening electrical contact element contact pad protruding portion curved sensor chip first main surface of sensor chip second main surface of sensor chip sensor circuit contact opening wiring element anisotropic conductive film anisotropic conductive paste solder ball lens lens spacer housing sensor wafer flat sensor chip handling carrier mount pickup head membrane flux

Claims

CLAIMS1. An image sensor (10) comprising: a carrier (100) having a curved surface portion (101) , an opening (105) extending from the curved surface portion (101) to a second main surface (102) of the carrier (100) ; a curved sensor chip (110) arranged in the curved surface portion (101) , a second main surface (112) of the curved sensor chip (110) being adjacent to the curved surface portion ( 101 ) , and an electrical contact element (107) arranged in the opening (105) and extending from the curved surface portion(101) to the second main surface (102) of the carrier (100) .

2. The image sensor (10) according to claim 1, wherein the curved surface portion (101) is formed in a first main surface (103) of the carrier (100) opposite to the second main surface(102) of the carrier (100) .

3. The image sensor (10) according to claim 1 or 2, further comprising a contact opening (114) formed in the second main surface (112) of the curved sensor chip (110) .

4. The image sensor (10) according to claim 3, wherein the contact opening (114) is arranged adjacent to the opening (105) arranged in the carrier (100) .

5. The image sensor (10) according to any of the preceding claims, further comprising an anisotropic conductive film (116) between the carrier (100) and the curved sensor chip (110) .

6. The image sensor (10) according to any of the preceding claims, further comprising an anisotropic conductive paste(117) between the carrier (100) and the curved sensor chip(110) .

7. The image sensor (10) according to any of the preceding claims , further comprising a solder ball (118) between the carrier (100) and the curved sensor chip (110)8. The image sensor (10) according to any of the preceding claims, further comprising a lens (120) over the first main surface (111) of the curved sensor chip (110) .

9. A method of manufacturing an image sensor (10) comprising : forming (S100) a curved surface portion (101) in a first main surface (103) of a carrier (100) , forming (S110) an opening (105) extending from the curved surface portion (101) to a second main surface (102) of the carrier (100) , forming (S120) an electrical contact element (107) in the opening (105) , the electrical contact element (107) extending from the curved surface portion (101) to the second main surface (102) of the carrier (100) , arranging (S130) a flat sensor chip (125) in the curved surface portion (101) , and applying (S140) pressure and heat so that a second main surface (112) of the curved sensor chip (110) is adjacent to the curved surface portion (101) .

10. The method according to claim 9, further comprising applying an anisotropic conductive film (116) in the curved surface portion (101) after forming the electrical contact element (107) and before arranging the flat sensor chip (125) in the curved surface portion (101) .

11. The method according to claim 9, further comprising applying an anisotropic conductive paste (117) in the curved surface portion (101) after forming the electrical contact element (107) and before arranging the flat sensor chip (125) in the curved surface portion (101) .

12. The method according to claim 9, further comprising placing solder balls (118) in the curved surface portion (101) after forming the electrical contact element (107) and before arranging the flat sensor chip (125) in the curved surface portion ( 101 ) .

13. The method according to any of claims 9 to 12, further comprising thinning the flat sensor chip (125) to a thickness less than 100 pm before arranging the flat sensor chip (125) in the curved surface portion (101) .

14. The method according to any of claims 9 to 13, further comprising forming a contact opening (114) in the second main surface (112) of the flat sensor chip (125) before arranging the flat sensor chip (125) in the curved surface portion(101) .

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