TW200541026A - Light emitting diode package structure and manufacturing process thereof - Google Patents

Abstract

A light emitting diode package structure comprises a light emitting diode chip, a plurality of under bump metallurgy (UBM), a package substrate, a plurality of bonding pads, a plurality of bumps and a self-formed intermetallic compound is disclosed. The under bump metallurgy are disposed on the light emitting diode chip, and the material of the under bump metallurgy includes nickel at least. The bonding pads are disposed on the package substrate. The bumps are disposed between and electrically connect the under bump metallurgy and the bonding pads. The self-formed intermetallic compound is self-formed between the under bump metallurgy and the bumps through the reaction of the bumps and copper atom provided by the bonding pads. The self-formed intermetallic compound suits to control the spalling phenomenon of the under bump metallurgy and further maintains the photoelectric characters of the light emitting diode chip.

Description

200541026 V. Description of the invention (1) The invention belongs to the present invention. The present invention relates to a light emitting diode (Light Emitting Diode, LED) packaging structure and its manufacturing process, and in particular to a method using a flip chip package (FI ip chip). package) light emitting diode packaging structure and its manufacturing process. In the prior art, due to the continuous improvement of the luminous efficiency of light-emitting diodes, light-emitting diodes have gradually replaced fluorescent lamps and incandescent bulbs in certain areas, such as scanner lights, LCD backlights or front light sources that require high-speed response. , Car dashboard lighting, traffic lights and general lighting. Compared with traditional light bulbs, light emitting diodes have absolute advantages, such as volume /, long life, low voltage / current drive, non-rupture, no mercury (no pollution problems), and good light emitting efficiency (power saving) And other characteristics. Among various light-emitting diode elements, especially light-emitting diode elements containing compounds of the 丨 丨 group element, such as gallium nitride (GaN), aluminum gallium nitride (A1GaN), indium gallium nitride (GalnN), etc. Of light-emitting diode elements. Group III nitride is a material with a wide band energy gap. Its emission wavelength can cover from ultraviolet light to red light. It can be said that it covers almost the entire visible light band, so it is widely used in industry. FIG. 1 is a schematic cross-sectional view showing a conventional light-emitting diode package structure using a flip-chip package. Please refer to FIG. I, the light emitting diode package structure i00 is mainly composed of a light emitting diode chip U0, two ball-bottom metal layers (Under Bump Metallurgy 'UBMM20, a packaging substrate 13, two connection pads 140, and Consists of two bumps 150. The ball-bottom metal layer 12 is arranged to emit light

13214twf.ptd Page 7 200541026 V. Description of the invention (2) Diode wafer 110, and the far-latch connection pad 140 is arranged on the packaging substrate 13 The bump 1 5 0 is arranged on the bottom of the ball. This is s] u The upper part is as low as between the layer 120 and the connection pad 140. In the material of the bump 150, the early technology used tin error n #, and the advanced industrial areas of the world and the Gang Dang 焱 y y 入 masters into the M mouth fresh materials to reduce the toxicity The metal "Classic, biological and environmental watch treasures ^ ^, L know" to the human bones, and constantly strive to reduce mistakes in various

The proportion and amount of application in the field, so the material of the bump 150 is also a trend of two kinds of lead free solder. Based on human health and overall considerations, Japan and the EU have set a clear timetable to ban: Brother ’s solder. According to Japanese MITI (Mini τ aa τ ^ i ^ Ministry of Trade and Industry) regulations, since 2002, any lead-containing electronic products have been banned from being sold to Japan, and European c〇mmissi〇 under the European Common System. n proposals after 2007, EU countries will not produce any lead-containing electronic products. It is clear that the use of error-free solders has become an inevitable trend in the electronics industry. However, in the conventional light-emitting diode package structure using flip-chip packaging, the use of error-free solder will highlight quite a few problems. In the conventional technology, the 'ball-bottom metal layer 120 is usually a three-layer thin film structure of chromium / copper / gold (Cr / Cu / Au)' or a two-layer thin film structure of chromium / nickel (Cr / Ni). When the bottom metal layer 120 is chromium / copper / gold, the tin in the bump 150 will react with the copper layer in the bottom metal layer 120 to form a Cu-Sn intermetallic compound, and when When the ball-bottom metal layer 120 is chromium, the tin in the bump 150 will react with the nickel layer in the ball-bottom metal layer 120 to form a Sn-Ni intermetallic compound. Whether it is a copper-tin-based metal compound or a tin-nickel-based metal compound, the interface between it and the chromium layer has a very high interface energy.

13214twf.ptd Page 8 200541026 V. Description of the invention (3) During the reflow process of block 150, 4 people MT copper-tin intermetallic compound or tin-nickel bimetallic compound will gradually spheroidize and leave The surface of the chromium layer is suspended in the bumps. This phenomenon is called the peeling phenomenon (spa 丨 丨 丨

Phenomenon), and the above-mentioned peeling phenomenon will seriously affect the strength of the solder joint in the light emitting monolithic package structure. The inventor of the invention The purpose of the invention is to provide a kind of light emitting diode packaging structure, which is suitable for suppressing the peeling phenomenon in the metal layer under the ball. • Another object of the present invention is to provide a light-emitting diode packaging process to maintain the high reflectivity of the metal parts in contact with the metal and good ohmic contact. The invention proposes a light-emitting diode packaging structure, which is composed of a light-emitting diode chip, multiple ball-bottom metal layers, a packaging substrate, multiple connections, multiple bumps, and a self-generating intermetallic compound ( self_fommed intermetallic compound). Is a μ ball? The plutonium is placed on the light-emitting diode wafer, and the material constituting the gold base :: includes at least the recording. The connection pad is disposed on the packaging substrate. The bump 酉 has been placed between the bottom metal layer and the connection pad, so that the bottom metal layer and the connection 塾 ΐ. 1 The generation of the intermetallic compound is generated between the ball-bottom metal layer and the bumps by the copper atoms provided by the connection pads. In the embodiment, the light emitting diode packaging structure further includes, for example, a plurality of :: 's, which are separately arranged on the connection pads. The nickel layer has at least one opening and contacts the bump with 2 pads. The light emitting diode wafer is composed of, for example, a substrate and a conductive layer. The semiconductor layer is formed on the substrate in, for example, an epitaxy. Semiconductor layer

132l4twf.ptd 200541026 V. Description of the invention (4) A bulk layer, a light-emitting layer, and a second type doped semiconductor layer. The first holy doped semi-v-layer layer is located on the substrate, the light emitting layer is located on a partial region of the first type doped semiconductor layer, and the second type doped semiconductor layer is located on the light emitting layer. In addition, the first type doped semiconductor layer and the first type doped semiconductor layer where no light emitting layer is distributed, for example, a plurality of contact layers are respectively arranged. The spherical bottom metal layers described by Θ are disposed on the respective contact metal layers. The present invention further provides a light emitting diode packaging process, which first provides a light emitting diode wafer. Next, a plurality of ball-bottom metal layers are formed on the light-emitting diode. The material constituting the bottom metal layer includes at least nickel. Then, a packaging substrate is provided, and a plurality of connection pads are formed on the packaging substrate. The next step is a solder block between the ball-bottom metal layer and the connection pads, so that the ball-bottom metal layer and the pads are electrically connected. Finally, the solder bump is re-soldered to form a plurality of bumps, and at the same time, a self-generating intermetallic compound is generated between the ball-bottom metal layer and the bump. For example, a nickel layer is formed on the connection pad, and the nickel layer has one opening. In the above two embodiments, the material of the connecting ytterbium is, for example, copper or copper, and the copper alloy is, for example, copper-chromium alloy, copper-nickel alloy, or copper-tungsten alloy. rich). In summary, in the light-emitting diode packaging structure and the manufacturing process of the present invention, the copper atoms provided by the connection pad will react with the tin in the bump, and form a self-generating intermetallic compound in the second process. By the self-generating metallization, the contact between the bump and the metal layer at the bottom of the ball can be blocked, and then 132l4twf.Ptd page 10 200541026 V. Description of the invention (5) The occurrence of the phenomenon. In order to make the above and other objects and advantages of the present invention easy to understand, the preferred embodiments are exemplified below, and the following will be more clearly explained in conjunction with the attached ^ 4. Figure 2 shows the flow chart of the light-emitting diode of a preferred embodiment of the present invention in detail, and Figures 3A to 3F show the present invention—the preferred Fenfeng W diode packaging process. Sectional flow chart_, FIG. 4 shows one of the two examples of light-emitting diodes. The schematic cross-sectional view of the light-emitting diode package structure of the embodiment is another example. Please refer to FIG. 2 for the light-emitting diode package of this embodiment. The main process is to provide the light-emitting diode wafer S1, to form a ball-bottom metal layer, to provide. The steps of flattening the substrate S3, forming the connection pad S4, forming the solder bump S6, and reflowing the solder at the same time naturally generate the self-generating intermetallic compound S7. ‘In addition, between the two steps of forming the connection pad S4 and forming the solder bump% in this embodiment, for example, it further includes forming a nickel layer on the connection pad S5. Referring to FIG. 3A, the light emitting diode packaging process of this embodiment first provides a light emitting diode chip 2 1 0. The light-emitting diode wafer 21 0 is composed of, for example, a base material 220 and a semiconductor layer 230. The material of the substrate 220 may be sapphire, silicon carbide (GaN), or gallium nitride (GaN), but is not limited to the above materials. The semiconductor layer 230 is composed of, for example, a doped semiconductor layer 232, a light-emitting layer 234, and a hybrid semiconductor layer 236, and the formation method thereof is, for example, epitaxy. Wherein, the doped semiconductor layer 232 is located on the substrate 220, the light emitting layer 234 is located on a partial region of the doped semiconductor layer 2 3 2, and the doped semiconductor layer 2 3 6 is

^ 32l4twf.ptd Page 11 200541026

Located on the light-emitting layer 234. The doped semiconductor layer 232 and the doped semiconductor layer 236 are different types of doped semiconductor layers. For example, if a semiconductor is doped; 232 is a p-type doped semiconductor layer, the doped semiconductor layer 236 is an n-type doped semiconductor layer. Conversely, if the doped semiconductor layer 232 g is an N-type doped semiconductor layer, the doped / doped semiconductor layer 236 is a p-type doped semiconductor layer. The light-emitting layer 234 is, for example, a muih weH (mqw) junction. In this embodiment, the light-emitting diode wafer 2 includes, for example, a plurality of contact metal layers 2 4 2, 2 4 4 (herein Two as examples). Contact metal layer 2 4 2

On the doped semiconductor layer 232 where the light emitting layer 234 is not arranged, and the contact metal layer 244 is on the doped semiconductor layer 236. The two contact metal layers 242, 244 are used to strengthen the ohmic contact and serve as electrodes, and preferably have a high reflectivity material. If the doped semiconductor layer contacted by the contact metal layer 242 is a doped semiconductor layer, the contact metal layer 242 preferably has a titanium / metal or titanium / silver layer structure. If the doped semiconductor layer 2 contacted by the contact metal layer 24 2 is a P-type doped semiconductor layer, the contact metal layer 242 preferably has a double structure of nickel / aluminum or nickel / silver. The contact metal layer 244 can also adopt a junction corresponding to the contact metal layer 242 due to the contact = doped semiconductor layer of the same type.

M9 Tianran, the light-emitting diode wafer 21 is not limited to the use of contact metal 244. The main role of the contact metal layers 242, 244 is to strengthen the semiconductor, and the layer 230 is in ohmic contact with subsequent material layers. With the above methods, for example, the surface of the doped semiconductor layer is doped with a 1 ^ -type element, or the N-type doped semiconductor is doped, and the surface is doped with a P-type element. The semiconductor layer 23 and subsequent steps can also be strengthened.

132l4twf.ptd Page 12 200541026 V. Description of the invention (7) Purpose of ohmic contact of material layer. In addition, the light emitting diode wafer 2 10 further includes, for example, a passivation protection layer 250 covering the semiconductor layer 230 but exposed portions contacting the metal layers 242, 244. The material of the passivation protective layer 2 50 is, for example, SiO2, Nitride or Nitride. Next, referring to FIG. 3B, two ball-bottom metal layers 2660,270 are formed on the light-emitting diode wafer 210. The two ball-bottom metal layers 2 60 and 2 70 are respectively disposed on the two contact metal layers 242 and 244, and the materials and materials constituting the ball-bottom metal layers 260 and 270 include at least nickel. The two ball-bottom metal layers 260, 270 are composed of, for example, adhesive layers 262, 272, barrier layers 264, 274, and solderable metal layers 266, 276, respectively. Among them, the materials of the adhesive layers 2 62, 2 72 are, for example, chromium, titanium, titanium tungsten alloy, or nitride buttons, and the materials of the barrier layers 264, 274 are, for example, nickel, platinum, palladium (pd), or copper. Referring next to FIG. 3C, a packaging substrate 28o is provided, which is composed of a conductive and rate path layer 284. The material of the substrate 282 is arranged on the substrate 282 with a high U-road layer m. The material of the substrate is preferably a metal such as silver or aluminum. With reference to FIG. 3D, Yu Yang a Jia, referring to FIG. 3D, two connection pads 286, 288 on the line 280 of the packaging substrate 280 are used to form a copper-nickel alloy or a copper-tungsten alloy on the two sides 84. The connection pad has copper-chromium alloy at 2 °, and the following solder is formed on the solder to make the soldering :: use the system to provide copper and steel atoms to react, and generate as shown in Figure 3F Intermetal

Page 13 200541026 V. Description of the invention (8) ----- Chemical compound 3 2 0 Self-generating intermetallic compound 3 2 0 will be explained later. Next, referring to FIG. 3E, two solder bumps 312a, 31 "are formed on the ball-bottom metal layer 26 0, 2 70 or the connection pads 286, 288, and the diode chip is electrically connected through the solder bumps 312a, 314a. 21 ° ball bottom metal layers 26〇, 270 and the connection pads 286, 288 of the packaging substrate 280. The material of the solder blocks 312a, 31 乜 is, for example, lead-free solder or tin-containing solder. Next, please refer to FIG. 3F and FIG. The solder bumps 312a, 314a are back-zinced to form two bumps 3 1 2, 3 1 4. During the re-soldering, the copper atoms provided by the solder and the connection pads 286, 288 will react to form a self-generated ^ The metal compound 320 is gradually deposited on the side near the ball-bottom metal layer 260, 2 70. The self-generating intermetallic compound 32o is, for example, a ternary phase copper-nickel-tin. Since the self-generating intermetallic compound 3 2 〇It has the effect of blocking the reaction, so it can block the nickel in the ball-bottom metal layers 260 and 270 from contact with the solder, thereby effectively avoiding the depletion of the ball-bottom metal layers 2 60, 2 70. Please refer to FIG. Between the two steps of FIG. 3D and FIG. 3E, a nickel layer 290 can be further formed. On the connection pads 286, 288, the nickel layer 290 has at least one opening 01 'to expose the connection pads 286, 288. In this way, the result is as shown in Fig. 4

The light emitting diode package structure 300a is shown. The thickness of the nickel layer 29 is not limited in any way. The role of the nickel layer 2 90 is to prevent oxidation of the connection pads 286, 288, and also to control the contact area of the connection pads 286, 288 and the bumps 312, 314. Finally, please refer to FIG. 3F and FIG. 4. The two light-emitting diode packaging structures 3 0 0 and 3 0 0 a of the present invention are mainly composed of the light-emitting diode wafer 2 丨 0 and two balls.

200541026 V. Description of the invention (9) The bottom metal layer 260, 270, a dream | 288, two bumps 31 2, 3, 4 and — ^ & As a result, the light-emitting diode encapsulated metal compound 32 ° is structured at 30 ° with more nickel corpuscles 0, and the remaining dichotomy is: synonymous first-diode package junction formation = 'the main spirit of the present invention-self-generated intermetal The compound m family blocks' i. Naturally generated image. Purpose. In order to suppress the peeling of the metal layer at the bottom of the ball, as shown above, in this case, the tL :! body packaging structure provided by the connection pad and its process reaction, and form a self-forming and bumps during reflow The tin compound can block the genus Bump. Since the self-generated metallized nickel will not be in contact with the convex: inside: tin ^, the ball bottom metal layer will be consumed and reacted to ensure that the ball bottom metal layer is not Effectively suppress the peeling of the ball bottom metal layer. Limiting the invention] The red / preferred embodiment is disclosed as above, but it is not intended to be used within the scope, when it can be used] Second, the artist will not deviate from the spirit of the present invention when i φ i = f Movement and retouching, therefore, the protection scope of Jiaming patent of the present invention shall prevail. 13214twf.ptd Page 15 200541026 Brief Description of Drawings Figure 1 shows a schematic cross-sectional view of a conventional light-emitting diode package structure using a flip-chip package. FIG. 2 is a flowchart of a light emitting diode packaging process according to a preferred embodiment of the present invention. 3A to 3F are cross-sectional flowcharts of a light emitting diode packaging process according to a preferred embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a light emitting diode package structure according to another preferred embodiment of the present invention. [Illustration of diagrams and expressions] I 0 0: Light-emitting diode package structure II 0: Light-emitting diode wafer 1 2 0: Ball-bottom metal layer 1 3 0: Packaging substrate 1 4 0: Connection pad 1 5 0: Bump 2 1 0: Light-emitting diode wafer 220: Substrate 23 0: Semiconductor layer 2 3 2, 2 3 6: Doped semiconductor layer 2 3 4: Light-emitting layer 242, 244: Contact metal layer 2 5 0: Purified Protective layer 2 6 0, 2 7 0 · Ball bottom metal layer 2 62, 272: Adhesive layer

13214twf.ptd Page 16 200541026 Brief description of the drawings 264, 274: Barrier layer 2 6 6, 276: Solderable metal layer 2 8 0: Packaging substrate 2 8 2: Substrate 2 8 4: Circuit layer 286, 288: Connection pad 2 9 0: Nickel layer 30 0, 30 0a: Light emitting diode package structure • 3 1 2, 3 1 4: Bump 320: Self-generating intermetallic compound 01 ·· Opening

13214twf.ptd Page 17

Claims (1)

200541026 VI. Scope of patent application 1 · A light emitting diode package structure 'includes: a light emitting diode wafer; a plurality of ball-bottom metal layers arranged on the light-emitting diode wafer to form the ball-bottom metal layers. The material includes at least a packaging substrate; a plurality of connection pads disposed on the packaging substrate; a plurality of bumps disposed between the ball bottom metal layer and the connection pads so that the ball bottom metals A layer is electrically connected to the rhenium connection pad; and a self-generating intermetallic compound is generated between the ball-bottom metal layers and the bumps. 2 · The light emitting diode packaging structure described in item 1 of the scope of the patent application, wherein the material of the connection pads is copper. 3. The light-emitting diode packaging structure described in item 1 of the scope of the patent application, wherein the materials of the connection 栝 are copper alloy. 4 · The light-emitting diode package structure described in item 3 of Shenqing's patent scope, where the material of the connection pads is one of copper-chromium alloy, copper-nickel alloy disk, copper-tungsten alloy. 〃 • The light-emitting diode package junction described in item 1 of Shi Shenqing's patent scope includes a plurality of nickel layers, which are respectively disposed on the connection pads, and the recording layers have at least one opening to The connection pads are brought into contact with the bump. 1 · The light-emitting diode packaging junction as described in item 1 of the scope of the patent application, wherein the materials of the bumps include lead-free solder and tin-containing solder. Page 18, 200541026 VI. Patent application scope The light-emitting diode encapsulation described in item 1 above, wherein the light-emitting diode wafer includes: τ… a substrate; and a semiconductor layer, which is arranged on the substrate. From L 、， 一 型 # 杂 丰 导 俨 ® 11, the semiconductor layer includes a first cedar heterofeng V body layer, a light emitting layer, and a younger layer, wherein the first-type doped semiconductor layer is located at ; ': + Bu the bulk light layer is located on the part of the first type doped semiconductor layer ^, and the second type doped semiconductor layer is located on the light emitting layer. And the side of the furnace Λ Ϊ Γ "" described in the seventh range of the light-emitting diode package junction quot ^ Xi several contact metals [arranged in the luminescent do not distribute the ί-type doped semiconductor On the layer and on the second impurity semiconductor layer =, the ball-bottom metal layers are respectively disposed on the contact metal screens. 9. A light-emitting diode packaging process including: providing a light-emitting diode A plurality of ball-bottom metal layers on the light-emitting diode crystal, and the materials of the ball-bottom metal layers include at least nickel; ▲ forming a package substrate; forming a plurality of connection pads on the package substrate Forming a plurality of solder bumps between the ball-bottom metal layers and the connection pads so that the ball-bottom metal layers are electrically connected to the connection pads; and returning the solder bumps to form a plurality of bumps At the same time, a self-generating intermetallic compound is naturally generated between the ball-bottom metal layers and the bumps. 10. The light-emitting diode packaging process described in item 9 of the scope of patent application, wherein the connection pads The material includes copper. I32l4twf.ptd Page 19 200541026 11 · The light emitting diode packaging process as described in item 9 of the scope of patent application, wherein the material of the connection pads is copper alloy. . 1 2 · The light-emitting diode package as described in item 1 of the patent application scope, wherein the material of the connection pads includes one of copper-chromium alloy, copper-nickel alloy, and steel-tungsten alloy. 1 3 · According to the light-emitting diode packaging system described in item 9 of the scope of patent application, between forming the connection pads and forming the solder bumps, it further includes forming a nickel layer on the connection pads, respectively. And the nickel layers have at least one opening. 1 4 · The light-emitting diode packaging system described in item 9 of the scope of the patent application, wherein the material of the solder bumps includes one of lead-free solder and tin-containing solder. 〇 Page 20