Patent Application
20140273318
This application claims priority to, and benefit of, Korean Patent Application No. 10-2013-0028185 filed on Mar. 15, 2013, with the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference.
The present disclosure relates to a method of forming a metallic bonding layer, and more particularly, to a method of manufacturing a semiconductor light emitting device therewith.
A technology of bonding a target object such as an electronic device to another object such as a substrate by using a bonding metal has been widely used. In particular, when manufacturing an electronic device such as a semiconductor light emitting device and transferring the manufactured electronic device to a different substrate, a bonding technology of using a eutectic metal has been used to transfer the manufactured electronic device to a permanent substrate.
However, unnecessary voids may be generated within a eutectic metal bonding layer formed by a reaction between bonding metals, thereby deteriorating bonding strength. In particular, a problem as described above may easily occur when a bonding surface is uneven, and thus, it may become a main causative factor in generating a defect in bonding between target objects.
The present disclosure provides a method of forming a metallic bonding layer having improved connection reliability to suppress the generation of voids and maintain solid bonding at the time of bonding target objects, and a method of manufacturing a semiconductor light emitting device using the metallic bonding layer formed thereby.
An aspect of the inventive concept relates to a method of forming a metallic bonding layer, including forming a first bonding metal layer and a second bonding metal layer on surfaces of first and second bonding target objects, respectively. The second bonding target object is disposed on the first bonding target object to allow the first and second bonding metal layers to face each other. A eutectic metal bonding layer is formed through a reaction between the first and second bonding metal layers. At least one of the first and second bonding metal layers includes a reaction delaying layer formed of a metal for delaying the reaction between the first and second bonding metal layers.
The at least one of the first and second bonding metal layers may include a metal selected from the group consisting of tin (Sn), indium (In), zinc (Zn), bismuth (Bi), lead (Pb), nickel (Ni), gold (Au), platinum (Pt), copper (Cu), cobalt (Co), and an alloy thereof.
In this case, the reaction delaying layer may include a metal selected from the group consisting of titanium (Ti), tungsten (W), chromium (Cr), tantalum (Ta), and an alloy thereof. The reaction delaying layer may have a thickness of 10 Å to 1000 Å.
The at least one of the first and second bonding metal layers may include a first reaction layer formed on one surface of the first or second bonding target object and containing at least one of nickel (Ni), platinum (Pt), gold (Au), copper (Cu) and cobalt (Co) and a second reaction layer formed on the first reaction layer, reacting with a metal of the first reaction layer to provide a eutectic metal, and containing a metal selected from the group consisting of tin (Sn), indium (In), zinc (Zn), bismuth (Bi), gold (Au), cobalt (Co), and an alloy thereof, and in this case, the reaction delaying layer may be located between the first reaction layer and the second reaction layer.
The at least one of the first and second bonding metal layers may further include a cap layer formed on the second reaction layer and containing at least one of platinum (pt) and lead (pb).
The surfaces of the first and second bonding target objects, on which the first bonding metal layer and the second bonding metal layer are formed, respectively, may be uneven surfaces. The surfaces, as bonding surfaces, may have a step portion or a concave-convex portion.
Another aspect of the inventive concept encompasses a method of manufacturing a semiconductor light emitting device, including preparing a light emitting laminate including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer sequentially formed on a temporary substrate. A first bonding metal layer is formed on the light emitting laminate and a second bonding metal layer is formed on a permanent substrate. The light emitting laminate is disposed on the permanent substrate to allow the first and second bonding metal layers to contact each other. A eutectic metal bonding layer is formed through a reaction between the first and second bonding metal layers to bond the light emitting laminate to the permanent substrate. At least one of the first and second bonding metal layers includes a reaction delaying layer formed of a metal for delaying the reaction between the first and second bonding metal layers.
The permanent substrate maybe a conductive substrate. The method of manufacturing a semiconductor light emitting device may further include removing the temporary substrate, a semiconductor growth substrate, after the forming of the eutectic metal bonding layer.
Still another aspect of the inventive concept relates to a method of forming a metal bonding layer, including forming a first bonding metal layer and a second bonding metal layer on surfaces of first and second bonding target objects, respectively. The first and second bonding metal layers include first and second reaction delaying layers formed of a metal, respectively. A first mixture layer, including a eutectic metal resulting from a reaction between the first and second bonding metal layers, is formed. A first residual reaction delaying layer and a second residual reaction delaying layer are formed. A first residual reaction delaying layer and a second residual reaction delaying layer are positioned in a vicinity of the first mixture layer through a reaction between the first and second bonding metal layers.
The method may include forming a second mixture layer at an edge of the first residual reaction delaying layer and forming a third mixture layer at an edge of the second residual reaction delaying layer.
The eutectic metal may be formed of NiSn or NiSnAu.
The reaction delaying layer may include a metal selected from the group consisting of titanium (Ti), tungsten (W), chromium (Cr), tantalum (Ta), and an alloy thereof.
The first and second residual reaction delaying layers maybe formed of the same material as a material of the reaction delaying layer. The first and second residual reaction delaying layers may be warped or partially disconnected.
The above and other aspects, features and other advantages will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters may refer to the same or similar parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments of the inventive concept. In the drawings, the thickness of layers and regions may be exaggerated for clarity.
Embodiments of the present inventive concept will now be described in detail with reference to the accompanying drawings.
Embodiments of the present inventive concept may, however, be embodied in many different forms and should not be construed as being limited to embodiments set forth herein. Rather, these embodiments of the present inventive concept are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art.
With reference to
In the embodiment of
The respective first and second bonding metal layers 12 and 22 may include a metal (including an alloy) thereof selected from tin (Sn), indium (In), zinc (Zn), bismuth (Bi), lead (Pb), nickel (Ni), gold (Au), platinum (Pt), copper (Cu), cobalt (Co) or an alloy thereof.
In detail, as shown in
The two reaction layers 12a and 12b of the first bonding metal layer 12 react with each other and the two reaction layers 22a and 22b of the second bonding metal layer 22 react with each other, to form a eutectic metal. Although not particularly limited, the second reaction layer 12b of the first bonding metal layer 12 may include a metal (including an alloy) having a relatively high diffusion coefficient as compared with the first reaction layer 12a, and the first reaction layer 12a of the first bonding metal layer 12 may serve to maintain adhesion between the first substrate 11 and the first bonding metal layer 12. Similarly, the second reaction layer 22b of the second bonding metal layer 22 may include a metal (including an alloy) having a relatively high diffusion coefficient as compared with the first reaction layer 22a, and the first reaction layer 22a of the second bonding metal layer 22 may serve to maintain adhesion between the second substrate 21 and the second bonding metal layer 22.
For example, as the first reaction layers 12a and 22a, a metal of at least one of Ni, Pt and Cu may be included therein. The respective second reaction layers 12b and 22b may include a metal selected from tin (Sn), indium (In), zinc (Zn), bismuth (Bi), gold (Au), cobalt (Co), or an alloy thereof,
In the embodiment of
For example, the reaction delaying layer 15 may include a metal selected from titanium (Ti), tungsten (W), chromium (Cr), tantalum (Ta) or an alloy thereof. The reaction delaying layer 15 may have a thickness of 10 Å to 1000 Å.
As shown in
In the molten state, the second reaction layers 12b and 22b may have relatively high fluidity as compared with the first reaction layers 12a and 22a, and respectively react with the first reaction layers 12a and 22a. As a result, as shown in
In the embodiment of
In more detail, molten Sn, SnAu layers, and the like, used as the second reaction layers 12b and 22b may react with different reaction layers (i.e., the first reaction layers 12a and 22a), for example, an Ni layer, a Pt layer, or a Cu layer, to thus form a eutectic metal bonding layer while forming NiSn, NiSnAu, PtSnAu and CuSn phases. Without a reaction delaying layer, e.g., the reaction delaying layer 15, fluidity of the Sn layer, melted during the reaction process described above, may be reduced. Therefore, the Sn layer, the SnAu layer, the NiSn layer, the NiSnAu layer, the PtSnAu layer and the CuSn layer may not fill a step part formed in a bonding surface of a semiconductor layer or a substrate, and thus, voids may be formed in the bonding surface of the semiconductor layer and the substrate. In an embodiment of the present inventive concept, a reaction delaying layer may be formed between two reaction layers to delay a reaction therebetween, thereby securing a sufficient degree of fluidity to realize a relatively high filling rate.
In particular, even when bonding surfaces of first and second substrates of a bonding target object have uneven or rough surfaces, that is, a step structure or a surface having concave-convex portions, the eutectic metal bonding layer EM having an excellent bonding strength through a filling effect using the reaction delay as described above may be obtained.
Hereinafter, operations and effects of the reaction delaying layer according to an embodiment of the present inventive concept will be described with reference to embodiments described below.
Referring to
Subsequently, heat was applied thereto such that the GaN light emitting device A1 and the silicon substrate B1 were bonded to each other through the first and second bonding metal layers, to thereby form a eutectic metal bonding layer.
Referring to
Subsequently, heat was applied thereto such that the GaN light emitting device A2 and the silicon substrate B2 were bonded to each other through the first and second bonding metal layers, to thereby form a eutectic metal bonding layer.
Images obtained by capturing cross sections of the eutectic metal bonding layers formed through embodiment 1 and comparative example 1 are shown in
As shown in
That is, in the case of comparative example 1, the reaction between Ni and SnAu progressed rapidly over a relatively wide region, thereby generating voids in an uneven surface, not yet filled therein, such as the step S, while in the case of embodiment 1, the reaction between Ni and SnAu was delayed by the Ti reaction delaying layer located between the two reaction layers such that even an uneven surface such as the step (S) structure may be maintained with a relatively high fluidity while securing a filling time, whereby the generation of voids may be significantly suppressed.
In this regard, with reference to
As described above, even in the bonded objects having an uneven surface such as a step structure, the reaction between the metal bonding layers may be delayed using a reaction delaying layer, thereby providing a eutectic metal bonding layer having a relatively high bonding strength due to a relatively high filling rate therein.
In addition, further experimentation, as described in embodiment 2A, embodiment 2B, and comparative example 2 below, was carried out in order to observe a reaction delay effect depending on a thickness of a reaction delaying layer.
Referring to
Subsequently, heat was applied thereto such that the GaN light emitting device A4 and the silicon substrate B4 were bonded to each other through the first and second bonding metal layers, thereby forming a eutectic metal bonding layer EM4.
Referring to
Subsequently, heat was applied thereto such that the GaN light emitting device A5 and the silicon substrate B5 were bonded to each other through the first and second bonding metal layers, thereby forming a eutectic metal bonding layer EM5.
Referring to
Subsequently, heat was applied thereto such that the GaN light emitting device A3 and the silicon substrate B3 were bonded to each other through the first and second bonding metal layers, thereby forming a eutectic metal bonding layer EM3.
As shown in
Meanwhile, referring to
As such,
Hereinafter, various examples of a metal bonding system using a reaction delaying layer will be described.
First,
The first bonding metal layer 112 may include a first reaction layer 112a formed on one surface of the first substrate 111 and a second reaction layer 112b formed on the first reaction layer 112a. In a similar manner to the description above, the second bonding metal layer 122 may also include a first reaction layer 122a formed on one surface of the second substrate 121 and a second reaction layer 122b formed on the first reaction layer 122a. In addition, unlike the embodiment illustrated in
In the example of
As described above, the reaction delaying layers 115 and 125 formed of Ti may secure a sufficient degree of fluidity by delaying a reaction process performed in a bonding procedure such that a desired filling rate is obtained and a bonding system having excellent reliability may be provided.
As shown in
In a different form, as shown in
In a different form of bonding system, as shown in FIG. 7C, a eutectic metal bonding layer EM3 may include a first mixture layer R11 including a eutectic metal formed of NiSn or NiSn/Sn/NiSn (alternatively, formed of NiSnAu when the first reaction layer is formed of AuSn) in a central region thereof. The eutectic metal bonding layer EM3 may also include Ti layers 115′ and 125′ positioned in the vicinity of the first mixture layer R11, and a second mixture layer R12 formed of NiSn or NiAuSn at an edge of the eutectic metal bonding layer EM3, on which an Ni layer barely remains due to an overall reaction of the eutectic metal bonding layer EM3.
As such, even when the same metal bonding layer as shown in
With reference to
The first bonding metal layer 212 may include a first reaction layer 212a formed on one surface of the first substrate 211 and a second reaction layer 212b, 212c having a dual-layer structure formed on the first reaction layer 212a. In a similar manner thereto, the second bonding metal layer 222 may also include a first reaction layer 222a formed on one surface of the second substrate 221 and a second reaction layer 222b, 222c having a dual-layer structure formed on the first reaction layer 222a.
In the example of
The reaction delaying layers 215 and 225 may be respectively provided with the first and second bonding metal layers 212 and 222. That is, the reaction delaying layer 215 may be formed between the first reaction layer 212a and the Au layer 212c, and the reaction delaying layer 225 may be formed between the first reaction layer 222a and the Au layer 222c.
The first reaction layers 212a and 222a may be formed of Ni. Besides using Ni, as the first reaction layers 212a and 222a, platinum (Pt), gold (Au), copper (Cu) or cobalt (Co) may be used. The reaction delaying layers 215 and 225 may both be formed of a Ti layer. In addition, as the reaction delaying layers 215 and 225, tungsten (W), chromium (Cr), tantalum (Ta) or an alloy thereof may be used besides using Ti.
As shown in
In a different form, as shown in
In a different form of bonding system, as shown in FIG. 9C, a eutectic metal bonding layer EM3 may include a first mixture layer R21 including a eutectic metal formed of NiSnAu in a central region thereof, Ti layers 215′ and 225′ positioned in the vicinity of the first mixture layer R21, and second mixture layers R22 and R22′ that are formed of NiSnAu at an edge of the Ti layers 215′ and 225′, respectively. In addition, in the form of bonding system as illustrated in
In a different form of bonding system, as shown in
As described above, even when the same metal bonding layer as shown in
In the present example, unlike the structure of the second reaction layer illustrated in
A cap layer may be formed on the metal bonding layer as needed, and both sides of metal bonding layers maybe changed to have an asymmetrical structure. An example thereof is illustrated in
The first bonding metal layer 312 may include a cap layer 312b formed on a first reaction layer 312a formed on one surface of the first substrate 311. The second bonding metal layer 322 may include a first reaction layer 322a formed on one surface of the second substrate 321, a second reaction layer 322c formed on the first reaction layer 322a, and a cap layer 322b formed on the second reaction layer 322c. The cap layers 312b and 322b may be adopted to prevent the first and second bonding metal layers 312 and 322 from being oxidized and may be formed of Pd or Pt. The cap layers 312b and 322b as described above may have relatively low thicknesses of several tens of Å, but are not limited thereto.
In the example as illustrated in
In the example as illustrated in
d illustrate a eutectic metal bonding layer (EM) structure obtained using the first and second bonding metal layers shown in
As shown in
In a different form thereto, as shown in
As such, even when the same metal bonding layer as shown in
Unlike the example illustrated in
In the example as illustrated in
In addition, reaction delaying layers may be applied to both of the first and second bonding metal layers 412 and 422. That is, the reaction delaying layers 415 and 425 may be applied to the first and second bonding metal layers 412 and 422, respectively. The reaction delaying layers 415 and 425 may be formed of Ti. In addition to, or instead of, Ti, W, Cr, Ta or an alloy thereof may be used as necessary.
As shown in
In a different form therefrom, as shown in
In a different form of bonding system, as shown in
As such, even when the same metal bonding layer as shown in
The above-mentioned various forms of bonding systems may be useful for bonding an electronic device such as a semiconductor light emitting device to a substrate. As an example, a method of manufacturing a semiconductor light emitting device using the above-described eutectic metal bonding layer is illustrated in
With reference to
Such a growth process may be performed using, for example, a metal organic chemical vapor deposition (MOCVD) or a molecular beam epitaxy (MBE). The light emitting laminate may be formed of a group III-V-based semiconductor, specifically, a group III nitride semiconductor represented by (AlxGayIn(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). The substrate 701 for growing a nitride semiconductor crystal may be formed using sapphire, silicon carbide (SiC), silicon (Si), MgAl2O4, MgO, LiAlO2 or LiGaO2.
Subsequently, as shown in
The permanent substrate 705 may be a conductive substrate, for example, an Si substrate or an Si—Al alloy substrate. The first and second bonding metal layers 712 and 722 may include reaction delaying layers 715 and 725, respectively. The first bonding metal layer 712 may include a first reaction layer 712a and a second reaction layer 712b, which mutually react and form a eutectic metal, and the reaction delaying layer 715 may be located between the first reaction layer 712a and the second reaction layer 712b. Similarly, the second bonding metal layer 722 may include a first reaction layer 722a and a second reaction layer 722b, which mutually react and form a eutectic metal, and the reaction delaying layer 725 may be located between the first reaction layer 722a and the second reaction layer 722b.
The first reaction layers 712a and 722a are layers respectively bonding to, as the bonding target object, the permanent substrate 705 and the light emitting laminate. The first reaction layers 712a and 722a may include at least one of nickel (Ni), platinum (Pt), gold (Au), copper (Cu) and cobalt (Co). The second reaction layers 712b and 722b may include a metal selected from tin (Sn), indium (In), zinc (Zn), bismuth (Bi), gold (Au), cobalt (Co) or an alloy thereof.
The reaction delaying layers 715 and 725 may include a metal selected from titanium (Ti), tungsten (W), chromium (Cr), tantalum (Ta) or an alloy thereof. The reaction delaying layers 715 and 725 may have a thickness of 10 Å to 1000 Å.
Subsequently, the permanent substrate 705 may be disposed on the second conductive semiconductor layer 704 such that the first and second bonding metal layers 712 and 722 face each other, and heat may be applied thereto to melt the first and second bonding metal layers 712 and 722, thereby forming a eutectic metal bonding layer EM. The molten second reaction layers 712b and 722b may move to react with the first reaction layers 712a and 722a, respectively, to thereby form a eutectic metal. At this time, reaction may be delayed by the reaction delaying layers 715 and 725 adopted in the example as illustrated in
Next, as shown in
Subsequently, as shown in
As such, when a bonding surface of the light emitting laminate or a bonding surface of the permanent substrate 705 has a step structure or a structure such as a concave-convex portion, the generation of voids may be suppressed and a solid eutectic metal bonding layer EM may be formed by appropriately filling even a relatively small space, and bonding reliability may be significantly enhanced.
Such a eutectic metal bonding layer may be usefully applied to other various semiconductor light emitting devices.
As illustrated in
The first electrode layer 820 may be stacked on the conductive substrate 810 and a portion of the first electrode layer 820 may extend through a contact hole 880 penetrating the insulating layer 830, the second electrode layer 840, the second conductive semiconductor layer 804 and the active layer 803 and penetrating up to a portion of the first conductive semiconductor layer 802, so as to contact the first conductive semiconductor layer 802. Thus, the conductive substrate 810 may be electrically connected to the first conductive semiconductor layer 802.
That is, the first electrode layer 820 may electrically connect the conductive substrate 810 to the first conductive semiconductor layer 802, through the contact hole 880. More specifically, the conductive substrate 810 may be electrically connected to the first conductive semiconductor layer 802 through a region having the size of the contact hole 880, e.g., a contact region 890 (see
Meanwhile, the first electrode layer 820 may be provided with the insulating layer 830 formed thereon to electrically insulate the first electrode layer 820 from different layers except for the conductive substrate 810 and the first conductive semiconductor layer 802. That is, the insulating layer 830 may be provided between side portions of the second electrode layer 840, the second conductive semiconductor layer 804 and the active layer 803 exposed to the contact hole 880, and the first electrode layer 820. The insulating layer 830 may be also provided between the first electrode layer 820 and the second electrode layer 840. In addition, the insulating layer 830 may be provided with side portions of predetermined regions of the first conductive semiconductor layer 802.
The second electrode layer 840 may be provided on the insulating layer 830, but may not be formed on predetermined portions thereof through which the contact hole 880 is formed. Here, the second electrode layer 840 may have an exposed region of a portion of an interface contacting the second conductive semiconductor layer 804, that is, at least one exposed region 845 as shown in
In addition, a light emitting laminate may not be formed on the exposed region 845. Further, the exposed region 845 may be provided at an edge of the semiconductor light emitting device 800 as shown in
The second conductive semiconductor layer 804 may be provided on the second electrode layer 840, and the active layer 805 may be provided on the second conductive semiconductor layer 804, and the first conductive semiconductor layer 802 may be provided on the active layer 804. Here, the first conductive semiconductor layer 802 may be an n-type nitride semiconductor, and the second conductive semiconductor layer 804 may be a p-type nitride semiconductor.
As shown in
The eutectic metal bonding layer EM may be formed of a eutectic metal resulting from a reaction between molten metal (including alloys) and may be a eutectic metal containing a metal selected from tin (Sn), indium (In), zinc (Zn), bismuth (Bi), lead (Pb), nickel (Ni), gold (Au), platinum (Pt), copper (Cu), cobalt (Co), or alloys thereof. In addition, the eutectic metal bonding layer EM may include a reaction delaying layer 815. The reaction delaying layer 815 may be formed of a metal selected from titanium (Ti), tungsten (W), chromium (Cr), tantalum (Ta) or an alloy thereof, and may have a function of delaying a reaction process in which a eutectic metal is obtained in a bonding process.
As a result, since the reaction delaying layer 815 is formed during a reaction process in which the eutectic metal is formed, the reaction delaying layer 815 may be present in a form of having a discontinuous or irregular thickness rather than having a complete layer structure.
In the embodiments illustrated in
As set forth above, in a method of forming a metal bonding layer and a method of manufacturing a semiconductor light emitting device therewith according to embodiments of the present inventive concept, the generation of voids within a eutectic metal bonding layer obtained through a reaction of a metal bonding between both bonded objects may be effectively suppressed whereby relatively high bonding strength may be maintained. In particular, the method may be usefully applied to a transfer technology of an electronic device such as a semiconductor light emitting device. Further, the generation of voids that would easily occur in a eutectic metal bonding layer when a bonding surface is an uneven surface having a concave-convex portion or a step structure, may be significantly suppressed.
While the inventive concept has been shown and described in connection with embodiments, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the spirit and scope of the present inventive concept as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2013-0028185 | Mar 2013 | KR | national |
