US 20080157110A1
`
`(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2008/0157110 A1
`(43) Pub. Date: Jul. 3, 2008
`
`Huang et al.
`
`(54) LED CHIP HAVING MICRO-LENS
`STRUCTURE
`
`(75)
`
`Inventors:
`
`Tien—Fu Huang, Hsinchu (TW);
`Shih-Hao Hua, Hsinchu (TW);
`Kuo-Chang Hu, Hsinchu (TW)
`
`Correspondence Address:
`RABIN & Berdo, PC
`1101 14TH STREET, NW, SUITE 500
`WASHINGTON, DC 20005
`
`(73) Assignee:
`
`Industrial Technology Research
`Institute, Hsinchu (TW)
`
`(21) Appl. No.:
`
`11/826,469
`
`(22)
`
`Filed:
`
`Jul. 16, 2007
`
`(30)
`
`Foreign Application Priority Data
`
`Dec. 29, 2006
`
`(TW)
`
`................................. 095150067
`
`Publication Classification
`
`(51)
`
`Int. Cl.
`(2006.01)
`H01L 33/00
`(52) use. ................................... 257/98; 257/E33.068
`
`(57)
`
`ABSTRACT
`
`A light-emitting diode (LED) chip having a micro-lens struc-
`ture includes a light-emitting structure and a light guide lens.
`The light-emitting structure emits a light from a light-emit-
`ting surface upon being applied with a current, and the light
`guide lens is stacked on the light-emitting surface and used
`for emitting the light from a light guide surface of the light
`guide lens. The light guide surface has an annular ridge por-
`tion and a scatter region, such that the lights close to the
`central optical axis of the light-emitting surface (the region
`having the maximum light-emitting intensity) are deflected in
`a direction away from the central optical axis, and the lights
`far away from the central optical axis are deflected towards
`the central optical axis, so as to obtain a light with a uniform
`overall optical intensity.
`
`
`
`«.mma-ammmmmm
`~.,‘-.‘-.\‘It->.‘-f-f-K-,
`
`APPLE 1044
`
`1
`
`APPLE 1044
`
`

`

`Patent Application Publication
`
`Jul. 3, 2008 Sheet 1 0f 5
`
`US 2008/0157110 A1
`
`100
`
`
`
`
`110
`
`FIG.2 (PRIOR ART)
`
`2
`
`2
`
`

`

`Patent Application Publication
`
`Jul. 3, 2008 Sheet 2 0f 5
`
`US 2008/0157110 A1
`
`130
`
`V
`
`.
`
`O O O O
`'O'O'O;Q;0.0.0.0.0.0 _
`o o’o’o‘o‘o’o
`.9 O O O 0 0.9.0.0 ‘
`
`132
`
`9 Q O O 9
`;
`‘O'O'O'O'O'O;0;O
`9 ’
`- 0.0.:.9.:.O’9.9 O
`
`136
`
`
`
`""
`
`FIG.4 (PRIOR ART)
`
`3
`
`

`

`Patent Application Publication
`
`Jul. 3,
`
`2008 Sheet 3 of 5
`
`US 2008/0157110 A1
`
`.fimaaammM.am.
`
`\‘wn’\‘flfl’m’ra.
`
`4
`
`

`

`Patent Application Publication
`
`Jul. 3, 2008 Sheet 4 0f 5
`
`US 2008/0157110 A1
`
`
`
`1000/0
`
`50°0
`
`.
`
`50%
`
`100%
`
`
`
`5
`
`

`

`Patent Application Publication
`
`Jul. 3, 2008 Sheet 5 0f 5
`
`US 2008/0157110 A1
`
`I
`
`--.-_-
`_m I
`
`314
`
`FIG.9
`
`6
`
`

`

`US 2008/0157110 A1
`
`Jul. 3, 2008
`
`LED CHIP HAVING MICRO-LENS
`STRUCTURE
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] This non-provisional application claims priority
`under 35 U.S.C. §119(a) on Patent Application No(s).
`095150067 filed in Taiwan, R.O.C. on Dec. 29, 2006, the
`entire contents of which are hereby incorporated by refer-
`ence.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of Invention
`[0002]
`[0003] The present invention relates to a light-emitting
`diode (LED) chip having a micro-lens structure, and more
`particular to an LED chip for providing a uniform plane light
`source.
`
`2. RelatedArt
`[0004]
`[0005] Referring to FIG. 1, the light-emitting chip having a
`micro-lens structure is a packaged LED chip 100, and it can
`be found from FIG. 1 that, an N-type semi-conductive layer
`102, an active layer 104, and a P-type semi-conductive layer
`106 are sequentially stacked on a transparent substrate 110.
`Then, the LED chip 100 is placed on a substrate 110 (e.g., a
`lead frame), and after the N-type semi-conductive layer 102
`and the P-type semi-conductive layer 106 are respectively
`guided to two electrode points 116 and 118 of the substrate
`110 through leads 112 and 114, a lens 120 is integrally pack-
`aged, and thus, an LED chip 100 is finished. The N-type
`semi-conductive layer 102 and the P-type semi-conductive
`layer 106 can be exchanged with each other.
`[0006] When being used, as long as a current is applied on
`the two electrode points 116 and 118 of the substrate 110,
`light 122 is produced by the interaction of electrons and holes
`between the N-type semi-conductive layer 102 and the P-type
`semi-conductive layer 106 and the active layer 104. The
`wavelength of the light 122 is relevant to the material of the
`active layer 104. The produced light 122 is emitted by the lens
`120 after being reflected and refracted, and thus, the lens 120
`has both functions of guiding the light-emitting angle and
`protecting the chip.
`[0007] Although the above structure is capable of produc-
`ing lights, the direction of the light emitted from the lens is
`difficult to be controlled due to the internal total reflection and
`
`refraction, and a distribution diagram of the light-emitting
`angle and intensity shown in FIG. 2 is usually produced. As
`known from FIG. 2 that, the design of the lens 120 makes the
`light-emitting angle 124 (the angle for emitting the light)
`between about positive 350 and negative 350 from the central
`optical axis 126 (0° position), and the closer the distance from
`the central optical axis is, the higher intensity is. As seen from
`FIG. 2 that, the region 128 having a higher intensity is about
`positive/negative 12° from the central optical axis 126, and
`thus, the uniformity of the light source is poor, and it is not
`suitable for the application requiring a plane light source.
`[0008]
`FIG. 3 shows a technique of controlling the light
`emitting direction, which is disclosed in the US. Pat. No.
`6,987,613. FIG. 3 shows a flip chip LED chip 130 with a
`Fresnel lens layer 134 added above a top layer 132. Therefore,
`the light 138 emitted from the active layer 136 performs a
`total reflection in the LED chip 130 (at the left side, right side,
`and lower side ofthe figure), and the light 138 is emitted from
`the light-emitting surface (the upper side of the figure)
`
`through the Fresnel lens layer 134. Since the Fresnel lens
`layer 134 is characterized in emitting the light in parallel
`(so-called parallel light), a plane light source is produced.
`[0009] Although the above US. Pat. No. 6,987,613 can
`achieve the object of a plane light source, due to the compli-
`cated process for fabricating the Fresnel lens layer 134, it is
`diflicult to be produced.
`[0010] Moreover, FIG. 4 shows a technique of fabricating a
`lens on the surface from which the LED emits the light, which
`is disclosed in US. Pat. No. 7,023,022. It is characterized in
`disposing a micro-lens array layer 162 on a light-emitting
`surface of the LED chip 160, such that a total reflection does
`not occur when the light is emitted from the active layer 164
`to the micro-lens array layer 162, but the light passes there
`through, so as to enhance the overall light-emitting perfor-
`mance. However, as for the direction of the light, it cannot
`provide a uniform plane light source.
`
`SUMMARY OF THE INVENTION
`
`[0011] The present invention provides an LED chip having
`a micro-lens structure, which has a light transmissive layer
`stacked on a light-emitting surface of the LED chip to be
`fabricated as a lens. Through the lens, the light emitted from
`the LED is made to be uniform in the light-emitting angle, and
`thus, the region having the maximum optical intensity distri-
`bution (close to the region of the optical axis) moves out-
`wardly from the optical axis, so that the overall light-emitting
`region becomes larger and more uniform (having a higher
`optical intensity), so as to provide a uniform plane light
`source.
`
`[0012] The LED chip having a micro-lens structure of the
`present invention includes a light-emitting structure and a
`transparent substrate having a micro-lens The light-emitting
`structure emits a light from a light-emitting surface upon
`being applied with a current. The light-emitting surface has a
`central optical axis, and the transparent substrate has a stack-
`ing surface and a micro-lens surface. The transparent sub-
`strate is stacked on the light-emitting surface through the
`stacking surface, so as to emit the light from the micro-lens
`surface. The micro-lens surface has an annular ridge with the
`central optical axis as the center, so as to form an annular
`converge region. The micro-lens surface is recessed from the
`annular ridge portion towards the central optical axis, so as to
`form a diverge region.
`[0013] The light-emitting structure includes at least an
`N-type semi-conductive layer, an active layer, and at least a
`P-type semi-conductive layer. Once a current is applied on the
`N-type semi-conductive layer and the P-type semi-conduc-
`tive layer, the active layer produces the light and emits the
`light from the light-emitting surface.
`[0014] Moreover, the annular converge region deflects the
`light passing through the annular condense region and emits
`the light towards the central optical axis. The diverge region
`deflects the light pas sing through the diverge region and emits
`the light away from the central optical axis.
`[0015] Therefore, the region close to the optical axis and
`having a higher optical intensity may become larger due to the
`refraction ofthe diverge region, and the region having a lower
`optical intensity focuses close to the central optical axis
`through the deflection of the annular converge region, so as to
`enhance the overall light-emitting uniformity and meet the
`requirements of the application of the plane light source.
`[0016]
`Further scope of applicability of the present inven-
`tion will become apparent from the detailed description given
`
`7
`
`

`

`US 2008/0157110 A1
`
`Jul. 3, 2008
`
`the
`it should be understood that
`hereinafter. However,
`detailed description and specific examples, while indicating
`preferred embodiments of the invention, are given by way of
`illustration only, since various changes and modifications
`within the spirit and scope of the invention will become
`apparent to those skilled in the art from this detailed descrip-
`tion.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`invention will become more fully
`[0017] The present
`understood from the detailed description given herein below
`for illustration only, which thus is not limitative ofthe present
`invention, and wherein:
`[0018]
`FIG. 1 is a schematic view of a structure of a con-
`ventional LED;
`[0019]
`FIG. 2 is a distribution diagram ofthe light-emitting
`angle and intensity of the conventional LED;
`[0020]
`FIG. 3 is a schematic structural view of a conven-
`tional LED chip having a micro-lens structure;
`[0021]
`FIG. 4 is a schematic structural view of another
`conventional LED chip having a micro-lens structure;
`[0022]
`FIG. 5 is a schematic structural view of a first
`embodiment of the present invention;
`[0023]
`FIG. 6 is a light energy distribution diagram of the
`first embodiment of the present invention;
`[0024]
`FIG. 7 is a distribution view of the light-emitting
`angle and intensity of the first embodiment of the present
`invention;
`[0025]
`FIG. 8 is a schematic structural view of a second
`embodiment of the present invention; and
`[0026]
`FIG. 9 is a schematic structural view of a third
`embodiment of the present invention.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`FIG. 5 is a schematic structural view of a first
`[0027]
`embodiment of the present invention. As seen from FIG. 5,
`the LED chip 200 having a micro-lens structure ofthe present
`invention includes a light-emitting structure 210 and a trans-
`parent substrate 230. The light-emitting structure 210 emits a
`light 202 from a light-emitting surface 204 once a current is
`applied, and the light-emitting surface 204 has a central opti-
`cal axis 206. The transparent substrate 230 is a micro-lens and
`has a stacking surface 232 and a light guide surface 234, and
`the light guide lens 230 is stacked on the light-emitting sur-
`face 204 through the stacking surface 232, so as to emit the
`light from the micro-lens surface 234. The micro-lens 234 has
`annular ridge portions 236 and 238 with the central optical
`axis 206 as the center, so as to form an annular condense
`region. The micro-lens 234 is recessed from the annular ridge
`portions 236 and 238 towards the central optical axis 206, so
`as to form a diverge region 240. The transparent substrate 230
`is to guide the light emitted from the light-emitting structure
`210 and passing through the transparent substrate 230. There-
`fore, the light guided by the transparent substrate 230 is not
`limited to visible light, but includes invisible light emitted
`from the light-emitting structure 210.
`[0028] The light emitted from the light-emitting structure
`210 is a visible light (with a wavelength between 380 nm and
`760 nm), an ultraviolet light (with a wavelength smaller than
`380 nm), and an infrared light (with a wavelength larger than
`760 nm).
`[0029] The above light-emitting structure 210 is formed by
`sequentially growing an N-type semi-conductive layer 214,
`
`an active layer 216, and at least a P-type semi-conductive
`layer 218 on a transparent substrate 212 through a semicon-
`ductor process. Once a current is applied to the N-type semi-
`conductive layer 214 and the P-type semi-conductive layer
`218 (i.e., a current is applied to two electrodes 226 and 228),
`the active layer 216 produces a light and emits the light from
`the light-emitting surface 204. The light-emitting surface 204
`herein is an upper surface in the figure, i.e., the light 202 is
`emitted from the active layer, and scattered in all directions.
`At this time, if the light contacts other surfaces except the
`light-emitting surface 204 (i.e., the left side 220, the lower
`side 222, and the right side 224 in the figure), a total reflection
`occurs until the light 202 is emitted out of the light-emitting
`surface 204, i.e., the light-emitting surface 204 is defined as a
`surface from which the light is penetrated directly.
`[0030] The central optical axis 206 of the above light-emit-
`ting surface 204 is the central position of the whole light-
`emitting surface 204, if the light-emitting surface 204 is
`square-shaped or a rectangle-shaped (viewed from the top of
`the figure), the central optical axis 206 is an intersection point
`of the diagonal lines. As seen from the structure of the LED
`200, the central optical axis 206 is at a position with the
`densest light rays ofthe whole LED 200, i.e., the position with
`the maximum optical intensity.
`[0031] The above transparent substrate 230 is made of a
`light-transmissive material for being penetrated by the light
`202. The light-transmissive material is, but not limited to, an
`optical glass (such as an optical glass with a high refraction
`index), a semiconductor material (such as III-V semiconduc-
`tor material, II-VI semiconductor material, an organic semi-
`conductor material with a high refraction index), or an
`organic compound (such as an organic compound with a high
`refraction index). The transparent substrate 230 is formed
`through the following procedures. A transparent layer is
`grown on the P-type semi-conductive layer 218; next, the
`annular ridge portions 23 6 and 238 and diverge region 240 are
`formed through an etching process. From the top view of the
`annular ridge portions 236 and 238, they are rings with the
`central optical axis 206 as the center as a convex curved
`surface, and the scatter region 240 is a round-shaped concave
`curved surface in the radial inner side ofthe ring, such that the
`light 202 passing through the diverge region 240 is deflected
`and emitted away from the central optical axis 206, i.e., the
`region with the maximum optical intensity distribution moves
`outwardly from the central optical axis 206 due to the deflec-
`tion of the scatter region 240. Therefore, although the bright-
`ness of the light spot with the maximum optical intensity is
`weakened, the overall uniformity is improved.
`[0032] The annular ridge portions 236 and 238 are disposed
`in the inner side of the light-emitting angle 208 (referring to
`FIG. 7) as a convex curved surface. The convex curved sur-
`face of the annular ridge portions 236 and 238 and the con-
`cave curved surface ofthe diverge region 240 are a continuous
`curved surface, such that when the light 202 passes through
`the annular ridge portions 236 and 238 (annular converge
`region), it is emitted towards the central optical axis 206 due
`to the refraction of the annular converge region. Therefore,
`the weaker light at the inner edge of the light-emitting angle
`208 is focused towards the central optical axis 206, and the
`light 202 close to the central optical axis 206 diverge towards
`the radial external side due to the diverge region 240, so as to
`form a uniform plane light source, which is shown in FIGS. 6
`and 7. The whole region with the maximum light-emitting
`intensity (e.g., calculated by less than 50% of the maximum
`
`8
`
`

`

`US 2008/0157110 A1
`
`Jul. 3, 2008
`
`intensity of the light spots) is expanded to positions of posi-
`tive/negative 45° from the central optical axis 206 due to the
`transparent substrate 230, so as to make the substantive
`effects of the present invention be more prominent.
`[0033] The above stacking surface 232 and the micro-lens
`surface 234 are two surfaces corresponding to each other, and
`the stacking surface 232 is stacked on the light-emitting sur-
`face 204, such that the light 202 penetrates from the light-
`emitting surface 204 and then directly emitted through the
`micro-lens surface 234, and the emitted light 202 is made
`more uniform through the appropriate allocations of the
`annular ridge portions 236 and 238 and the diverge region 240
`on the micro-lens surface 234.
`
`[0034] Then, FIG. 8 is a view of a second embodiment of
`the present invention. A transparent substrate 320 is stacked
`on a light-emitting structure 302, and the light-emitting struc-
`ture 302 may be a flip chip light-emitting-diode (LED) chip.
`In addition, the light 340 emitted by the LED chip 302 is made
`more uniform through the appropriate allocations of the
`annular ridge portions 322 and 324 and the diverge region 326
`on the transparent substrate 320, so as to achieve the same
`effect as the first embodiment. Only a brief introduction on
`the light-emitting structure 302 is given herein, an N—type
`semi-conductive layer 304, an active layer 306, a P-type
`semi-conductive layer 308, a reflection layer 310 are sequen-
`tially stacked on the light guide lens 320 (i.e., a transparent
`substrate 110) without forming the annular ridge portions
`322, 324 and the diverge region 326, and they are electrically
`connected to the two electrodes 312 and 314 of the N—type
`semi-conductive layer 304 and the P-type semi-conductive
`layer 308. When using, as long as a current is applied to the
`two electrodes 312 and 314, the active layer 306 emits the
`light 340. The annular ridge portions 322 and 324 and the
`diverge region 326 (i.e., micro-lens surface) ofthe transparent
`substrate 320 ofthis embodiment can only be formed through
`an etching process after the above light-emitting structure 3 02
`is completed.
`[0035]
`Finally, FIG. 9 is a schematic view of a third
`embodiment ofthe present invention, which has substantially
`the same structure as the second embodiment. The only dif-
`ference between them lies in that, the annular ridge portions
`322a and 324a of the third embodiment are designed as a
`convex curved surface and also as a Fresnel rough surface,
`and the diverge region 326a is a concave curved surface,
`which is also a Fresnel rough surface, and thus achieving the
`objects and effects of the present invention.
`[0036] The invention being thus described, it will be obvi-
`ous that the same may be varied in many ways. Such varia-
`tions are not to be regarded as a departure from the spirit and
`scope ofthe invention, and all such modifications as would be
`obvious to one skilled in the art are intended to be included
`
`within the scope of the following claims.
`What is claimed is:
`
`1. A light-emitting diode (LED) chip having a micro-lens
`structure, comprising:
`a light-emitting structure, for producing the light and emit-
`ting the light from a light-emitting surface upon being
`applied with the current, wherein the light-emitting sur-
`face has a central optical axis; and
`a transparent substrate, having a stacking surface and a
`micro-lens surface, wherein the micro-lens is stacked on
`the light-emitting surface via the staking surface thereof,
`so as to emit the light from the micro-lens surface; and
`the micro-lens surface has an annular ridge portion with
`
`the central optical axis as a center, so as to form an
`annular converge region, and the micro-lens surface is
`recessed from the annular ridge portion towards the cen-
`tral optical axis, so as to form a diverge region.
`2. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the light-emitting structure comprises at
`least an N—type semi-conductive layer, an active layer, and at
`least a P-type semi-conductive layer, and once a current is
`applied to the N—type semi-conductive layer and the P-type
`semi-conductive layer, the active layer produces the light and
`emits the light from the light-emitting surface.
`3. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the light is a visible light.
`4. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the light is an ultraviolet light.
`5. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the light is an infrared light.
`6. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the micro-lens is made of a light-trans-
`missive material.
`
`7. The LED chip having a micro-lens structure as claimed
`in claim 6, wherein the light-transmissive material is an opti-
`cal glass.
`8. The LED chip having a micro-lens structure as claimed
`in claim 6, wherein the light-transmissive material is at least
`one selected from a group consisting of III-V semiconductor
`material, II-VI semiconductor material, and organic semicon-
`ductor material.
`
`9. The LED chip having a micro-lens structure as claimed
`in claim 6, wherein the light-transmissive material is an
`organic compound.
`10. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the annular converge region deflects the
`light passing through the annular converge region and emits
`the light towards the central optical axis.
`11. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the diverge region deflects the light pass-
`ing through the scatter region and emits the light away from
`the central optical axis.
`12. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the light-emitting structure has a light-
`emitting angle with the central optical axis as a center, and the
`annular ridge portion is located at an inner side of the light-
`emitting angle.
`13. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the annular ridge portion is a convex
`curved surface.
`
`14. The LED chip having a micro-lens structure as claimed
`in claim 13, wherein the convex curved surface is a Fresnel
`rough surface.
`15. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the diverge region is a concave curved
`surface.
`
`16. The LED chip having a micro-lens structure as claimed
`in claim 15, wherein the concave curved surface is a Fresnel
`rough surface.
`17. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the diverge region and the converge region
`are a continuous curved surface.
`
`18. The LED chip having a micro-lens structure as claimed
`in claim 1, wherein the LED chip is a flip chip light-emitting
`diode chip.
`
`9
`
`