WO2014142448A1

WO2014142448A1 - Wafer level chip scale light emitting diode package

Info

Publication number: WO2014142448A1
Application number: PCT/KR2014/001527
Authority: WO
Inventors: Jin Sung Park
Original assignee: Jin Sung Park
Priority date: 2013-03-12
Filing date: 2014-02-25
Publication date: 2014-09-18
Also published as: KR101578266B1; KR20140111905A

Abstract

A light emitting diode package includes an electrically non-conductive carrier substrate (100). A first and a second via (101, 102) are formed by laser-drilling the carrier substrate before wafer bonding. The first and the second via are to be located under an LED chip. A growth substrate (200) on which epitaxial layers including a first, an active and a second epitaxial layer (201, 202, 203) are grown is included. A first and a second electrode (301, 302) are formed on the growth substrate and in electrical contact with the first and the second epitaxal layer. A bonding layer (304) is formed on the carrier substrate having the laser drilled vias for wafer-bonding the carrier and the growth substrate. A first and a second pad (405, 408) are formed on the carrier substrate and in electrical contact with the first and the second electrode.

Description

WAFER LEVEL CHIP SCALE LIGHT EMITTING DIODE PACKAGE

[Technical Field]

The present invention relates to a light emitting diode (LED) package, and more particularly to Wafer Level Chip Scale LED Package (CSP) and methods of fabricating the same.

[Background Art]

The fabrication of conventional LED package includes the epitaxial (epi) process of growing epi layers on a growth substrate, FAB of machining the epi layers to form LED chips by metallization, patterning, etching and dielectric layer deposition, and the packaging process of mounting an LED chip diced off from the growth substrate to a carrier substrate, electrically connecting electrodes on the LED chip to pads on the carrier substrate by wire bonding and encapsulating the LED chip on the carrier substrate by molding.

In conventional LED packaging, an LED chip, adhesive, gold wire, a submount and/or a carrier substrate are produced in other manufacturers and supplied to LED package manufacturers. LED packages are fabricated by processes to assemble individual LED chips with them supplied as raw materials. Thus, the packaging process may be costly, time consuming and low productivity.

In recent years a Wafer Level Package (WLP) technique of fabricating an LED package at wafer level has been applied, while the conventional packaging processes are carried out using individual LED chips diced off from the growth substrate as metioned before. WLP is a technique to produce wafers which have thousands of LED chips per wafer. However, in WLP not all of the processes are carried out at wafer level. Some processes of WLP are still carried out using individual LED chips. Moreover, WLP is not the wafer batch process that produces several tens of wafers from one single process because some processes of conventional packaging are applied.

An existing WLP technique is a complicated packaging method including dicing individual LED chips, attaching an LED chip to a carrier substrate (wafer) larger than a growth substrate, and electrically connecting electrodes on the individual LED chips to pads on the carrier substrate using wire bonding or Flipchip bonding process. Thus, the existing WLP does not have productivity as much as that of the wafer batch process.

Existing LED packages are about 2 - 3 times larger than the LED chip. Thus, the existing

WLP does not have package integration density per wafer as much as LED chip integration density per wafer. LED packages must have an area equal to LED chip for maximizing package integration density per wafer without any loss of LED chip integration density per wafer. Package productivity is decreased as much as the loss of LED chip integration density per wafer, even though the wafer batch process is applied for LED package fabrication.

Chip Level Process (CLP) is herein used as the term against the wafer batch process for easy descriptions. CLP means the packaging process using individual LED chips, while the wafer batch process means the process which produces several tens of wafers having thousands or ten thousands of LED chips per wafer from one single fabrication step.

For example, if CLP produces 1,000 packges per hour using individual LED chips, its productivity is 1,000 packages/hour. If wafer batch process produces hourly 10 wafers having 5,000 packages per wafer, its productivity is 50,000 packages/hour. Finally, the productivity of wafer batch process depends on package integration density per wafer. The productivity of wafer batch process is maximized when an LED package has an area equal to LED chip.

In accordance with international standards, Chip Scale Package (CSP) means the package which has an area no greater than 1.2 times that of the chip. CSP reduces the size of package so that the production cost can be reduced.

The embodiments of Chip Scale LED Package (CSP) are disclosed in US Laid-open Patent Application No. US 11/171,893 and Korean Laid-open Patent No. 10-1128261. The LED packages may be fabricated through wafer batch process. They have the two vias formed on the carrier substrate. One of the two vias is located outside the LED chip, not under the LED chip. Thus, the LED packages are not equal to the areas of their LED chips because space outside the LED chip is needed for the via outside the LED chip. Their chip and package integration density are decreased as much as the area is needed for the via outside the LED chip, compared to the LED package which has an area equal to the LED chip. In addition, the passivation layer is needed to prevent the electrical short of the two electrodes.

Another embodiment of US Laid-open Patent Application No. US 13/240,418 shows a structurally similar LED package to that of the present invention. However, the embodiment may have several problems which are described below using FIG. 19A - 19C and the same terms in its specification.

Etching or laser drilling may be used to form the second via holes 908, as described in the specification of US Laid-open Patent Application No. US 13/240,418. The specification shows that the second via holes 908 are formed after wafer bonding. However, there may be some constraints of forming the second via holes 908 after wafer bonding. The constraints will be described below. As shown in FIG. 19 A, the first via holes 907 formed on the polymer layer 903 and the second via holes 908 formed on the package substrate 904 are in a straight line without any misalignment due to inevitable process variance and tolerance, even though the first and the second via holes 907 and 908 are formed respectively in separate processes. However, the second via holes 908 may be larger than the first via holes 907 as shown in FIG. 19B. Forming the second via holes 908 larger than the first via holes 907 is to prevent any intrusion of the first via holes 907 shown in FIG. 19C.

As shown in FIG. 19C, the intrusion is that the edge of the first via holes 907 is formed out over the edge of the second via holes 908 due to misalignment of inevitable process tolerance and variance. If any intrusion of the first via holes 907 occurs as shown in FIG. 19C, the electrodes 906 may not be completely formed on the sidewall of the first via holes 907. Thus, a part of the polymer layer 903 may need to be overlapped with the second via holes 908 so that the second via holes 908 larger than the first via holes 907 are formed as shown in FIG. 19B.

The overlapped part may be deformed by etching the package substrate 904. Otherwise, the overlapped part may be etched by etching to form the second via holes 908 on the package substrate 904, even though the first via holes 907 are formed before wafer bonding (bonding the light emitting structure 901 and the package substrate 904) by patterning the polymer layer 903.

That is, forming the first via holes 907 before wafer bonding may not be necessary because the polymer layer 903 may be etched by etching the package substrate 904 after wafer bonding. If the overlapped part is etched by etching the package substrate 904, the first via holes 907 and the second via holes 908 may be formed in a straigt line.

When applying etching technique to form the second via holes 908, the material of the package substrate 904 must be substantially etchable like Silicon. However, Alumina (A1₂0₃) and Aluminum Nitride (A1N) which may be applied for the package substrate 904 may not be substantially machined by etching due to their intrinsic etching characteristics.

Forming the second via holes 908 by etching may make the fabrication steps more complex, compared to forming vias before wafer bonding by laser drilling. An etch mask layer including fiducial marks needs to be deposited and patterned on the package substrate 904 before wafer bonding, the second via holes 908 are etched after wafer bonding, and then the etch mask is finally removed. If the etch mask is formed after wafer bonding, fiducial marks may need to be deposited and patterned on the light emitting structure 901 for aligning the second via holes 908 to the first via holes 907.

In addition, when etching the package substrate 904 and removing the etch mask layer, the electrode pads 902 must not be deformed or damaged. That is, the electrod pads 902 must be a substance to resist the processes of removing the etch mask layer and etching to form the second via holes 908 on the package substrate 904.

If the second via holes 908 are formed by laser drilling, the fiducial marks may be formed simultaneously by the laser drilling during forming the second via holes 908 before wafer bonding. However, forming the second via holes 908 by etching requires additional processes to form and remove the etch maks and the fiducial marks on the package substrate 904, as metioned before.

Moreover, when applying laser drilling to form the second via holes 908 on the package substrate 904 of Silicon, Alumina A1N or the like, laser drilling must enable to form the second via holes 908 after wafer bonding in order for the invention to be realized. However, laser drilling cannot form the second via holes 908 after wafer bonding without any damage of the polymer layer 903 and the electrode pads 902. That is why the laser energy to drill these materials of the package substrate 904 is much higher than the laser energy to machine the polymer layer 903 and the electrode pads 902 under the package substrate 904. In other words, low laser energy which cannot deform polymers and metals of the electrode pads 902 must be used to prevent any damage of the polymer layer 903 and the electrod pads 902. However, the low laser energy cannot form the second via holes 908 on the package substrate 904 because these materials of the package substrate 904 require higher laser energy to drill them.

Laser drilling machines materials by local heating up to high temperature to locally melt and burn out materials.

On the one hand, etching to form the first via holes 907 before wafer bonding requires a process to form a patterned etch mask layer on the polymer layer 903. Otherwise, the polymer layer 903 may be patterned of a photosensitive material using photolithography process. Thus, some additional process steps may be needed after coating the polymer layer 903 on the light emitting structure 901 in order to form the first via holes 907.

In summary, the invention may be only realized when an etchable material of the package substrate 904 is applied and the second via holes 908 are formed by etching, while the present invention is to apply both of etchable and unetchable package substrates on which vias are formed by laser drilling before wafer bonding. In addition, the invention may require additional processes of fiducial marks and/or etch mask to form the second via holes 908, and of patterning the polymer layer 903 to form the first via holes 907 after coating the polymer layer 903. Thus, the invention requires more complex fabrication steps than the present invention.

A conventional LED package may include a phosphor layer and a lens covering an LED Chip on a carrier substrate. Space around the LED chip may be needed to form the phosphor layer and the lens on the carrier substratd Thus, the LED package is much greater than the LED chip. In conventional WLP, individual LED chips which are diced off from a growth substrate are attached on a carrier substrate (wafer) greater than the growth substrate. One of the reasons why the carrier substrate is greater than the growth substrate is to make enough space around the LED chip to form a phosphor layer and a lens covering the LED chip on the carrier substrate. Finally, conventional LED packages with a lens may not be a type of Chip Scale Package.

[Disclosure of Invention]

The present invention provides LED packages which are produced through wafer batch process. Unlike the conventional WLP and packaging, the LED packages are fabricated without using an individual LED chip, a submount and/or a carrier substrate that are separately fabricated in other sites as finished products, forming an LED chip and a carrier substrate simultaneously.

In addition, the LED packages which the present invention provides are the type of CSP equal to their LED chip area because any space around their LED chip is not required. Thus, the package integration density per wafer is maximized without any loss of the chip integration density per wafer. Thus, the productivity is much increased.

One of the problems described before is that the fabrication steps are complex. However, the present invention provides LED packages which are produced by much simplified fabrication steps.

According to some embodiments of the present invention, an LED PKG includes an electrically non-conductive carrier substrate. A first and a second via are formed by laser-drilling the carrier substrate before wafer bonding. The first and the second via are to be located under an LED chip. A growth substrate on which epitaxial layers including a first, an active and a second epitaxial layer are grown is included. A first and a second electrode are formed on the growth substrate and in electrical contact with the first and the second epitaxial layer. A bonding layer is formed on the carrier substrate having the laser-drilled vias for wafer-bonding the carrier and the growth substrate. A first and a second pad are formed on the carrier substrate and in electrical contact with the first and the second electrode.

In some embodiments, an LED package includes an electrically non-conductive and unetchable carrier substrate. A first and a second via are formed by laser-drilling the carrier substrate before wafer bonding. The first and the second via are to be located under an LED chip. A growth substrate on which epitaxial layers including a first, an active and a second epitaxial layer are grown is included. A first and a second electrode are formed on the growth substrate and in electrical contact with the first and the second epitaxial layer. A bonding layer is formed on the growth substrate for wafer-bonding the carrier substrate having the laser-drilled vias and the growth substrate. The bonding layer is etched through the first and the second via after wafer bonding in order for the first and the second electrode to be exposed. A first and a second pad are formed on the carrier substrate and in electrical contact with the first and the second electrode.

In some embodiments, an LED package may further include via filler filled inside the first and the second via on which a seed and a conductor layer are formed. In the LED package having the via filler, only the growth substrate may be removed with the epitaxial layers and the electrodes left on the carrier substrate.

In some embodiments, an LED PKG includes an electrically non-conductive carrier substrate. A first and a second via are formed by laser-drilling the carrier substrate before wafer bonding. The first and the second via are to be located under an LED chip. A growth substrate on which epitaxial layers including a first, an active and a second epitaxial layer are grown is included. A first and a second electrode are formed on the growth substrate and in electrical contact with the first and the second epitaxial layer. A bonding layer is formed on the carrier substrate having the laser-drilled vias for wafer-bonding the carrier and the growth substrate. Electrically conductive filler is filled inside the first and the second via without forming a seed layer and a conductor layer on the inside walls of the vias. The electrically conductive filler is in electrical contact with the first and the second electrode. A first and a second pad are formed on the carrier substrate and the electrically conductive filler, and in electrical contact with the first and the second electrode through the electrically conductive filler.

In some embodiments, an LED package includes an electrically non-conductive and unetchable carrier substrate. A first and a second via are formed by laser-drilling the carrier substrate before wafer bonding. The first and the second via are to be located under an LED chip. A growth substrate on which epitaxial layers including a first, ah active and a second epitaxial layer are grown is included. A first and a second electrode are formed on the growth substrate and in electrical contact with the first and the second epitaxial layer. A bonding layer is formed on the growth substrate for wafer-bonding the carrier substrate having the laser-drilled vias and the growth substrate. The bonding layer is etched through the first and the second via after wafer bonding in order for the first and the second electrode to be exposed. Electrically conductive filler is filled inside the first and the second via without forming a seed layer and a conductor layer on the inside walls of the vias. The electrically conductive filler is in electrical contact with the first and the second electrode. A first and a second pad are formed on the carrier substrate and the electrically conductive filler, and in electrical contact with the first and the second electrode through the electrically conductive filler. In the LED packages having the electrically conductive filler, only the growth substrate may be removed with the epitaxial layers and the electrodes left on the carrier substrate.

In some embodiments, an LED package may further include a passivation layer formed on the growth substrate having the epitaxial layers and the electrodes in electrical contact with the first and the second epitaxial layer. The passivation layer is etched through the vias after wafer bonding in order for the first and the second electrode to be exposed.

In some embodiments, an LED package comprises a lens with a chip nest resccesed in order for an LED chip to be mounted, a phosphor layer formed on the chip nest, and an LED chip attached to the phosphor layer. The LED chip has a growth substrate or dose not have only a growth substrate as it is removed from the LED chip. A reflective layer is filled in the gap between the inside wall of the chip nest and the LED chip. In further embodiments, the phosphor layer may be multilayer.

In further embodiments, the LED packages including the lens may further include an optical diffuser or an anti-reflection layer formed on the surface of the chip nest. The anti-reflection layer may be formed on the exterior surface of the lens.

In further embodiments, the LED packages including the lens may further include an adhesive layer formed between the LED chip and the phosphor layer.

In order to solve the problems that a carrier substrate may not be laser-drilled after wafer bonding without any damage of a bonding layer and an electrode on a growth substrate, the carrier substrate is machined by laser drilling before wafer bonding. Moreover, when applying an unetchable carrier substrate, the bonding layer is etched through the vias laser-drilled before wafer bonding as the unetchable carrier substrate is applied as an etch mask. Thus, additional processes of etching a carrier substrate and patterning a bonding layer are not needed. The present invention provides LED packages fabricated through further simplified fabrication steps.

In some embodiments, additional processes of patterning a bonding layer is not needed as the bonding layer is spray-coated on the carrier substrate having the vias laser-drilled before wafer bonding.

The present invention also provides LED packages which are attached to the lens. Thus, the lens does not influence package and chip integration density per wafer. On the other hand, conventional LED packages may have a lens attached to a carrier substrate to cover an LED chip. In the conventional LED packages including wafer level LED packages, the lens may make LED packages greater than LED chip and decrease package integration density per wafer because space on a carrier substrate around an LED chip is needed for forming the lens. [BRIEF DESCRIPTION OF DRAWINGS]

FIG. 1 is a cross-sectional view after forming epi layers on a growth substrate.

FIG. 2 is a cross-sectional view after etching the epi layers on the growth substrate.

FIG. 3 is a plan view after etching the epi layers on the growth substrate.

FIG. 4 is a cross-sectional view after forming a first and a second electrode on the epi layer. FIG. 5 is a plan view after forming a first and a second electrode on the epi layer.

FIG. 6 is a cross-sectional view after forming a passivation layer on the growth substrate. FIG. 7 is a cross-sectional view after forming a first and second via on a carrier substrate. FIG. 8A is a cross-sectional view after forming a bonding layer on the carrier substrate. FIG. 8B is a cross-sectional view after forming a bonding layer on the growth substrate.

FIG. 9A and 9B are a cross-sectional and a bottom view after wafer-bonding the carrier and the growth substrate.

FIG. 10 is a cross-sectional view after etching the bonding and the passivation layer through the vias.

FIG. 11 is a cross-sectional view after forming a seed and a conductor layer on the carrier substrate.

FIG. 12A and 12B are a cross-sectional view and a bottom view illustrating an LED package after forming a first and a second pad oh the carrier substrate.

FIG. 13 is a cross-sectional view illustrating an LED package having via filler filled inside of the vias.

FIG. 14 is a cross-sectional view illustrating an LED package having electrically conductive filler filled inside the vias, and a first and a second pad formed on the carrier substrate and the filler.

FIG. 15 is a plan view illustrating a lens module and a cross-sectional view illustrating a lens. FIG. 16 is a cross-sectional view after coating a phosphor layer and attaching an LED chip to the phosphor layer.

FIG. 17 is a cross-sectional view after forming a reflective layer surrounding the LED chip. FIG. 18 is a cross-sectional view illustrating an LED package from which only a growth substrate is removed.

FIG. 19A - 19C are drawings illustrating the LED package of US Laid-open Patent Application No. US 13/240,418 as a prior art. [Best Mode for Carrying Out the Invention]

Exemplary embodiments of the present invention will become more apparent by describing detailed embodiments of the present invention with reference to the accompanying drawings.

The terms used herein is for descrbing embodiments of the invention and is not intented to be limiting of the invention. Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this invention belongs.

Descriptions of well-known functions, elements, components or layers may be omitted so as not to unnecessarily obscure the embodiments of the present disclosure.

When an element or layer is referred to as being "on", "connected to", "bonded to/on", "attached to/on", "filled in/inside", "formed on", and "deposited to/on" another element or layer, there may be (an) intervening layer(s), component(s) or element(s) present between them, unless otherwise specified clearly.

The terms, first and second are only used herein to distinguish layers, elements and/or components for ease of description. These layers, elements and/or components should not be limited by the terms. Thus, they are not intended to correspond with each other.

In the drawings, each of elements are not exactly proportionate to actual sizes, thicknesses and lengths but may be exaggerated or simplified for ease of description and understanding. Furthermore, the various layers and regions illustrated in the figures are shown schematically. Accordingly, the present disclosure is not limited to the relative size and spacing illustrated in the accompanying drawings. In addition, embodiments of the present invention should not be construed as limited to the particular shapes and patterns illustrated herein. Thus, the present invention is not limited to the patterns, locations and shapes of the elements illustreated herein.

The terms LED chip and LED package may be used withtout distinction for ease of description and understanding. As the present invention is to form an LED package with an LED chip being formed simultaneously, an LED chip and an LED package may not be distinguishable clearly. On the other hand, a conventional LED package is fabricated through the three fabrication steps as metioned before. An LED chip and an LED package are clearly distinguishable in the conventional LED package. Thus, the present invention should not be limited by the terms.

The sigular forms "a", "ah", and "the" may be intended to include the plural forms. "A layer" may be multiple layers including various materials.

FIG. 12A and 12A are a cross sectional view and a bottom view showing first embodiments of the present invention. As shown in FIG. 12, the LED package includes a carrier substrate 100, two vias 101 and 102, a growth substrate 200, epi layers 201, 202 and 203, two electrodes 301 and 302, a passivation layer 303, a bonding layer 304 and two pads 405 and 408.

The LED package shown in FIG. 12 will be described in more details with reference to the embodiments of FIG. 1 through 12.

FIG. 1 shows the epiwafer which includes a growth substrate 200 and epi layers 201 , 202 and 203. The epi layers grown on the growth substrate 200 include a first epi layer 201, a second epi layer 203 and an active layer 202 between them. The active layer 202 is the epi layer to emit light. However, other epitaxial layers such as an electron-blocking layer and a buffer layer may be further disposed above or below the epi layers. All or some of the epi layers may be referred to as "an epi layer" or "the epi layer" with no particular limitation for ease of description.

The growth substrate 200 may include sapphire (AI2O3), Si, GaAs, GaN, A1N or any other suitable substrates. The first epi layer 201 is typically an n-type semiconductor layer and the second epi layer 203 is typically a p-type semiconductor layer. However, the first epi layer 201 may be a p-type and the second epi layer 203 may be an n-type.

FIG. 2 illustrates a cross sectional view of one single LED chip. The epi layer is masked, patterned and etched in order for the first epi layer 201 to be exposed for electrical conection.

FIG. 3 is a plan view of four LED chips and one single LED chip after eching the epi layer. A few or tens of thousands of LED chips may be formed on the growth substrate 200 according to the LED chip size.

Embodiments of the present invention will be described with reference to the figures of A-A' cross section line.

Refering to FIGS. 4 and 5, an electrically conductive layer is deposited and patterned on the epi layer in order for a first and a second electrode 301 and 302 to be formed. The first electrode 301 is connected to the first epi layer 201 and the second electrode 302 is connected to the second epi layer 203. The electrodes 301 and 302 may include Ni, Au, ITO, Ti, Al, Ag, and/or the like. The two electrodes 301 and 302 may be one single layer with one of theses materials or multiple layers including some of these materials.

The electrodes 301 and 302 are not only to electrically connect to the first and the second epi layer 201 and 203 but also to reflect the light emitted from the active layer 202 for improving optical performance.

As shown in FIG. 6, a passivation layer 303 is deposited on the growth substrate 200. The passivation layer 303 is to prevent a leakage current of the epi layers 201, 202 and 203. However, the passivation layer 303 may be removed because a bonding layer 304 which will be described below may prevent the leakage current. The passivation layer 303 may be formed of silicon oxide, silicon nitride, or the like.

FIG. 7 is a cross sectional view showing a carrier substrate 100 after forming two vias 101 and 102 per LED chip before wafer bonding described below. The vias 101 and 102 are formed by laser drilling. The vias 101 and 102 are routes through which the electrodes 301 and 302 are electrically connected to two pads 405 and 408 to be described in more details below.

The carrier substrate 100 may include A1N, Alumina, BeO, Silicon, or the like which is electrically non-conductive. If the carrier substrate 100 is an electrically conductive material, an electrical insulation layer must be formed on the carrier substrate and on the vias to prevent an electrical short. Thus, the fabrication step may become more complex. If the carrier substrate 100 has high thermal conductivity, the thermal resistance of LED package may be low.

As shown in FIG. 8 A, a bonding layer 304 is coated on the carrier substrate 100 by spray coating. The bonding layer 304 is for wafer-bonding the carrier substrate 100 and the growth substrate 200. Spray coating allows coating the boding layer 304 on the carrier substrate 100 without blocking the vias 101 and 102. Thus, the bonding layer 304 does not need to be machined further for electrically connecting the electrodes 301 and 302 to the pads 405 and 408 which will be described below.

However, as shown in FIG. 8B, a bonding layer 304 may be formed on the growth substrate 200 by spray or spin coating. The bonding layer 304 on the growth substrate 200 is etched through the vias 101 and 102 after wafer-bonding the carrier substrate 100 and the growth substrate 200. Patterning the bonding layer 304 before wafer bonding makes the fabrication steps more complex, compared to etching the bonding layer 304 through the vias 101 and 102 after wafer bonding, as metioned in details before. Etching the bonding layer 304 through the vias 101 and 102 will be described in more details below.

The bonding layer 304 is made from a polymer. The polymer may include BCB

(Benzocyclobutene), PI (Polyimide) or the like. The bonding layer 304 must be electrically non- conductive. The bonding layer 304 may prevent the leakage current of the epi layers 201, 202 and 203. Thus, the passivation layer 303 may be removed.

FIG. 9A and 9B illustrate a sectional view and a bottom view after wafer-bonding the carrier substrate 100 having the two vias 101 and 102 shown in FIG. 7 and the growth substrate 200 having the bonding layer 304 shown in FIG. 8B. Then, as shown in FIG. 10, the bonding layer 304 is etched through the vias 101 and 102. When the passivation layer 303 is under the bonding layer 304, the passivation layer 303 is etched through the vias 101 and 102. The passivation layer 303 may be etched by etching the bonding layer 304. When the bonding layer 304 is etched through the vias 101 and 102 after wafer bonding, the carrier substrate 100 must not be etched by the etching process of the bonding layer 304. In other words, the carrier substrate 100 must be applied as an etch mask while the bonding layer 304 is being etched.

A polymer which is used for the bonding layer 304 is typically etched by fluorine based chemistries such as CF4 and SF6. Thus, when the bonding layer 304 is etched through the vias 101 and 102 after wafer bonding, Silicon which is etched by fluorine based chemistries may not be used for the carrier substrate 100. However, A1N which is not etched by fluorine based chemistries can be used for the carrier substrate 100.

In further embodiments, FIG. 10 also shows a sectionval view after wafer-bonding the carrier substrate 100 having the spray-coated bonding layer 304 shown in FIG. 8 A and the growth substrate 100 shown in FIG. 6. In this case, the bonding layer 304 does not need to be machined further. When the passivation layer 303 is under the bonding layer 304, the passivation layer 303 is etched through the vias 101 and 102.

When an unetchable material is used for the carrier substrate 100, the bonding layer 304 is spray-coated on the carrier substrate 100 as shown in FIG. 8 A or formed the growth substrate 200 as shown in FIG. 8B.

However, when an etchable material is used for the carrier substrate 100, the bonding layer 304 is spray-coated on the carrier substrate 100 having the laser-drilled vias 101 and 102, as shown in FIG. 8 A. Thus, patterning the bonding layer 304 is not required.

As metioned in details before, laser drilling cannot be applied to form vias after wafer bonding. Thus, when an unetchable material is used for a carrier substrate, the vias must be laser- drilled before wafer bonding because the vias cannot be laser-drilled after wafer bonding or formed by etching. When an etchable material is used for a carrier substrate, the vias are laser- drilled before wafer bonding or formed by etching. However, laser drilling may be preferable for process simplification regardless of the etching characteristics of the carrier substrate 100.

In addition, the present invention does not require the additional processes of fiducial mark and/or etch mask and/or of forming the first via holes which are needed for the invention of US Laid-open Patent Application No. US 13/240,418.

"Etchable" means herein that a carrier substrate cannot be substantially used as an etch mask while a bonding layer is being etched and/or vias can be substantially formed on a carrier substrate by etching. In contrast, "unetchable" means herein that a carrier substrate can be substantially used as an etch mask while a bonding layer is being etched and/or vias cannot be substantially formed on a carrier substrate by etching. FIG. 11 shows a sectional view after forming a seed layer 401 and a conductor layer 402. The seed layer 401 may include Ti* Ni, Cr, Cu or the like to have good adhesion to the carrier substrate 100. The conductor layer 402 may include Ni, Cu, Au, Sn, or the like. However, the conductor layer 402 may be formed on the carrier substrate 100 without the seed layer 401. Then, as shown in FIG. 12A and 12B, a first and a second pad 405 and 408 are formed by patterning the seed layer 401 and the conductor layer 402 or the conductor layer 402 when the conductor layer 402 is only formed on the carrier substrate 100.

The first and the second pads 405 and 408 may be formed by Semi-Additive process technique that the seed layer 401 is deposited on the carrier substrate 100, a dry film is laminated and patterned, the conductor layer 402 is deposited by plating, the dry film is removed, and then the part of the seed layer 401 under the dry film is flash-etched.

The pads 405 and 408 are to be soldered to solder pads on an LED module. Thus, the pads 405 and 408 may further include a metal finish layer solderable. The metal finish layer is formed by Ni/Au plating, OSP (Organic Solder Preservative), HASL (Hot Air Solder Leveling), Ni/Pd/Au plating, or the like after patterning the seed layer 401 and the conductor layer 402. However, the metal finish layer may be doposied before patterning the seed layer 401 and the conductor layer 402, and then the metal finish layer, the seed layer 401 and the conductor layer 402 may be patterned.

The pads 405 and 408 are comprised of the seed layer 401, the conductor layer 402 and the metal finish layer. However, they may be comprised of the seed layer 401 and the metal finish layer without the conductor layer 402, when the metal finish layer is electrically conductive. Or, they may be comprised of the conductor layer 402 and the metal finish layer without the seed layer 401.

Further embodiments of the present invention are illustrated in FIG. 13 and 14. As shown in FIG. 13, via filler 501 of resin or conductive paste may be filled inside the vias 101 and 102 on which the seed layer 401 and the conductor layer 402 are formed. However, the via filler may be filled inside the vias 101 and 102 on which the conductor layer 402 is only formed without the seed layer 401. Then, the metal finish layer is formed. Thus, the pads 405 and 408 may be comprised of the seed layer 401, the conductor layer 402 and the metal finish layer, or they may be comprised of the conductor layer 402 and the metal finish layer.

As shown in FIG. 14, electrically conductive filler 502 may be filled inside the vias 101 and 102 without forming the seed layer 401 and the conductor layer 402. After filling the conductive filler 502, a first and a second pad 405 and 408 are formed on the carrier substrate 100 and the conductive filler 502. Thus, the conductive filler 502 electrically connects the electrodes 301 and 302 to the pads 405 and 408. In this case, the pads 405 and 408 my be comprised of the seed layer 401, the conductor layer 402 and the metal finish layer, or they may be comprised of the conductor layer 402 and the metal finish layer, or they may be comprised of the seed layer 401 and the metal finish layer, or they may have the metal finish layer only.

The fillers 501 and 502 are filled by screen printing.

Some applications of LED package may need a phosphor layer and an optical lens. The LED packages which the present invention provides are fabricated by wafer batch production. Forming a phosphor layer and an optical lens at wafer level is desirable, but it decreases package and chip integration density per wafer as metioned before. Thus, the present invention provides LED packages which are attached to a lens including a phosphor layer.

FIG. 15 illustrates a plan view of lens module and a sectional view of a lens. The lens module includes lens arrays. The lens 600 includes a chip nest 601 for an LED chip to be mounted. The lens module is made from PC (polycarbonate), COC (Cyclic Olefin Co-polymer), Silicone resin, or the like and by injection molding or the like.

The lens 600 may further include an optical diffuser (not shown in FIG. 15) which is a pyramid shape, a prism shape, or the like. The optical diffuser is formed on the surface of the chip nest 601. The optical diffuser may reduce the light reflected back towards the LED chip. Thus, the optical diffuser may improve light extraction efficiency.

The lens 600 may further include an anti-reflection layer (not shown in FIG. 15) to reduce the light reflected back towards the LED chip. The anti-reflection layer may be formed on the exterior surface of the lens 600 and/or the surface of the chip nest 601. The anti-reflection layer may be a thin film layer or multilayer thin films.

Refering to FIG. 16, a phosphor layer 701 is coated on the chip nest 601 by dispensing or sreen printing, and then an LED chip is attached to the phosphor layer 701. The phosphor layer 701 may be one single layer including one kind of phosphor or various kinds of phosphors, or the phosphor layer 701 may be multilayer.

An adhesive layer (not shown in FIG. 16) may be further formed between the phosphor layer 701 and the LED chip. The adhesive layer is to have the phosphor layer 701 not to attach directly to the LED chip. The phosphor layer 701 which is remote from the LED chip may reduce the light reflected back towards the LED chip.

As shown in FIG. 16, when an LED chip is mounted on the chip nest 601 , there may be a gap between the inside wall of the chip nest 601 and the LED chip. The light emitted from the LED chip may go out through the gap. Thus, as shown in FIG. 17, a reflective layer 702 is filled in the gap. The reflective layer 702 is formed of a white ink, a white resin or the like which has high reflection in order to make the light going out through the phosphor layer 701 and the lens 600.

In the LED packages described before, as shown in FIG. 18, only the growth substrate 200 may be removed with the epi layer and the electrodes 301 and 302 left on the carrier substrate 100. There may be light loss when the light is extracted through the growth substrate 200. Removing only the growth substrate 200 may improve light extraction efficiency.

The present invention has been shown and described with reference to exemplary embodiments thereof. Nevertheless, it will be understood by those of skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A light emitting diode package comprising;

an electrically non-conductive carrier substrate;

a first and a second via formed by laser-drilling the carrier substrate before wafer bonding, the first and the second via to be located under an LED chip;

a growth substrate on which epitaxial layers including a first, an active and a second epitaxial layer are grown;

a first and a second electrode formed on the growth substrate having the epitaxial layers, and in electrical contact with the first and the second epitaxial layer;

a bonding layer formed on the carrier substrate having the laser-drilled vias for wafer-bonding the carrier and the growth substrate; and

a first and a second pad formed on the carrier substrate and in electrical contact with the first and the second electrode.

2. A light emitting diode package comprising;

an electrically non-conductive and unetchable carrier substrate;

a first and a second electrode formed on the growth substrate having the epitaxial layers and in electrical contact with the first and the second epitaxial layer;

a bonding layer formed on the growth substrate for wafer-bonding the carrier substrate having the laser-drilled vias and the growth substrate, the bonding layer etched through the first and the second via after wafer bonding in order for the first and the second electrode to be exposed; and a first and a second pad formed on the carrier substrate and in electrical contact with the first and the second electrode.

3. The light emitting diode package of claim 1, further comprising;

via filler filled inside of the first and the second via on which a seed layer and a conductor layer are formed.

4. The light emitting diode package of claim 2, further comprising;

5. The light emitting diode package of claim 3, wherein only the growth substrate is removed with the epitaxial layers and the electrodes left on the carrier substrate.

6. The light emitting diode package of claim 4, wherein only the growth substrate is removed with the epitaxial layers and the electrodes left on the carrier substrate.

7. A light emitting diode package comprising;

an electrically non-conductive carrier substrate;

a bonding layer formed on the carrier substrate having the laser-drilled vias for wafer-bonding the carrier and the growth substrate;

electrically conductive filler filled inside the first and the second via without forming a seed layer and a conductor layer on the inside walls of the vias, the electrically conductive filler in electrical contact with the first and the second electrode; and

a first and a second pad formed on the carrier substrate and the electrically conductive filler, and in electrical contact with the first and the second electrode through the electrically conductive filler.

8. A light emitting diode package comprising;

an electrically non-conductive and unetchable carrier substrate;

a first and a second via formed by laser-drilling the carrier substrate before wafer bonding, the first and the second to be located under an LED chip;

a bonding layer formed on the growth substrate for wafer-bonding the carrier having the laser- drilled vias and the growth substrate, the bonding layer etched through the first and the second via after wafer bonding in order for the first and the second electrode to be exposed;

electrically conductive filler filled inside the first and the second via without forming a seed layer and a conductor layer on the inside walls of the vias, the electrically conductive filler in electrical contact with the first and the second electrode; and a first and a second pad formed on the carrier substrate and the electrically conductive filler, and in electrical contact with the first and the second electrode through the electrically conductive filler.

9. The light emitting diode package of claim 7 or 8, wherein only the growth substrate is removed with the epitaxial layers and the electrodes left on the carrier substrate.

10. The light emitting diode package of claim 1, 2, 7, or 8, furher comprising;

a passivation layer formed on the growth substrate having the epitaxial layers and the electrodes in electrical contact with the first and the second epitaxial layer, and the passivation layer etched through the vias after wafer bonding in order for the first and the second electrode to be exposed.

11. A light emitting diode package comprising;

a lens with a chip nest recessed in order for an LED chip to be mounted;

a phosphor layer formed on the chip nest;

an LED chip attached to the phosphor layer, the LED chip having a growth substrate; and a reflective layer filled in the gap between the inside wall of the chip nest and the LED chip.

12. A light emitting diode package comprising;

a lens with a chip nest recessed in order for an LED chip to be mounted;

a phosphor layer formed on the chip nest;

an LED chip attached to the phosphor layer, the LED chip from which only a growth substrate is removed; and

a reflective layer filled in the gap between the inside wall of the chip nest and the LED chip.

13. A light emitting diode package comprising;

a lens with a chip nest recessed in order for an LED chip to be mounted;

a phosphor layer formed on the chip nest, the phosphor layer is multilayer;

14. A light emitting diode package comprising;

a lens with a chip nest recessed in order for an LED chip to be mounted;

a phosphor layer formed on the chip nest, the phosphor layer is multilayer;

15. The light emitting diode package of claim 11, 12, 13 or 14, further comprising;

an optical diffuser formed on the surface of the chip nest.

16. The light emitting diode package of claim 11, 12, 13 or 14, further comprising; an anti-reflection layer formed on the surface of the chip nest.

17. The light emitting diode package of claim 11, 12, 13 or 14, further comprising; an anti-refelction layer formed on the exterior surface of the lens.

18. The light emitting diode package of claim 11, 12, 13 or 14, further comprising; an adhesive layer formed between the LED chip and the phosphor layer.