JP2854963B2 - Solid phase bonding method and apparatus - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method and an apparatus for solid-state joining of metals in a low-temperature and low-pressure region, and particularly to a semiconductor package, a liquid crystal device, and a thin-film module substrate. The present invention relates to a joining method suitable for micro joining of thin film components, and various members manufactured by the method.

[Conventional technology]

Conventionally, in the plastic package of semiconductor devices, the connection between the pad on the Si chip and the lead frame is Au.
Wire solid-phase bonding was performed using fine wires of Cu and Cu. FIG. 10 shows this conventional solid-state bonding process. In the figure, first, a Si chip 1 is mounted via a solder foil 5 on a die 4 formed integrally with a lead frame 3. Then, the heating table 7 is placed in a gas atmosphere 6 having an inert or reducing property.
To heat the die bond portion to fix the Si chip to the die. Next, the component is transported to a bonding apparatus, and after pre-heating the bonding portion under an inert or reducing atmosphere, a ball 14 formed at the tip of a wire is solid-phase bonded to the pad 2 and a capillary 15 is connected to the lead. Wedge solid-state bonding is performed to crush the wire.

In this process, in the solid-phase bonding using the Au thin wire 13, the pad 2 is made of Al, and the connection portion of the lead is made of Ag which increases the bonding property.
Alternatively, use a Cu-plated one with a joining temperature of 20
A pre-heating of 0-350 ° C. had been performed. However, due to the necessity of reducing manufacturing costs and improving the reliability of the connection part, it is desired to reduce the plating temperature of the lead and lower the bonding temperature. The problem is that the properties are reduced and the bonding temperature is reduced. On the other hand, in the solid-phase bonding using Cu fine wires, there were problems such as cracking of Si pellets by Cu balls having high hardness and deterioration of bondability due to plating-less connection at the lead side connection.

Also, a method of irradiating a spot to be wire-bonded with a laser beam, locally heating, and then bonding a solid wire by applying ultrasonic vibration to the heated wire-bonded spot by applying ultrasonic vibration. Is also known (JP-A-62-18725). In this one,
By using laser beam irradiation and ultrasonic pressure bonding together, some of the problems of the conventional hot pressing described above have been improved, but laser irradiation is limited to local heating. For this reason, it has been difficult to perform a sufficient surface treatment on a wide surface including the bonding surface because of the fact that the bonding is performed in an air atmosphere.

Further, after the metal wire, the semiconductor chip and the substrate are placed in a vacuum container, the inside of the container is evacuated, and then an ion beam or an atom beam is irradiated to the metal wire tip and the electrode on the chip for a predetermined time. A wire bonding method in which electrodes are overlapped and bonded is also known (JP-A-63-249344). This method can achieve a sufficient surface treatment for removing and joining a contaminated layer (oxide film, moisture, oil, etc.) on the surface to be joined in a vacuum atmosphere, but the means is an ion beam or an atom beam. Therefore, high vacuum evacuation is necessary, and it cannot be said that it is always satisfactory in terms of productivity.

Furthermore, as disclosed in the title of Welding Technology Vol.3 No.7 (1987) “Development of Ultra-High Vacuum Room Temperature Interface Bonding Device” (Mitsubishi Electric), the metal surface is clean without oxide film or adsorbed gas layer. It is already known that a high-strength joint can be obtained only by bringing the joint surfaces into contact with each other on the surface. However, even in this case, it is necessary to perform bonding in an ultra-high vacuum atmosphere, and it is difficult to apply the method to a practical production line considering the time required for evacuation. It is difficult to apply to the manufacturing process.

In addition, in the conventional bonding of the tape carrier and the Si chip,
The Au bump formed on the Al pad of the Si chip and the Sn film formed on the lead of the tape carrier faced, and heat and pressure were applied to form an Au-Sn melt by eutectic reaction and joined. The conventional terminal pitch was as coarse as 200 μm or more. However, in the future, the pad size and terminal pitch will be reduced due to the increase in the number of terminals, and the conventional thermocompression bonding method will result in narrow pitch due to misalignment due to thermal expansion of the film and short-circuit failure due to the bridge of the extruded melt. There is a problem with conversion.

Further, in a semiconductor device represented by a memory, an LSI, or the like, as shown in FIG. 11 at present, the connection pad 76 is arranged outside the active area 75,
Performance degradation or damage of the device due to the bonding process is not a problem unless cracks occur in the Si chip.
However, in the future, connection pads will be formed on the active area for high integration and miniaturization of chips. At this time, there is a concern that the element may be damaged by the pressing force or the ultrasonic vibration.

In the field of semiconductor devices such as large computers, LSI
In the future, high-density and high-density packaging will require multilayer thin-film module substrates in the future.
The process of manufacturing by laminating layers with wiring sequentially one by one passes through a large number of processing steps, resulting in poor productivity,
In addition, the product yield becomes worse due to the large number of steps. As a method of improving productivity and yield, a method of bonding several layers of thin film module substrates to each other and assembling them into a multilayer thin film module substrate can be considered, but a large number of connection pads formed on the upper and lower surfaces of the thin film module are required. There is a problem that it is difficult to bond and assemble without displacement or bonding failure.

[Problems to be solved by the invention]

The problems in the plastic package of a semiconductor device are as described above. 1) In the bonding combination of an Au ball and an Al pad, a fragile Au-Al intermetallic compound is generated at the interface due to heating at the time of bonding, and the connection strength is reduced. 2)
In the combination of Cu ball and Al pad, cracks may occur in the Si chip due to the applied pressure and ultrasonic vibration during the bonding. 3) Solvent on the lead joint surface when joining Au fine wire or Cu fine wire and plating-less lead frame. Even if cleaning or reduction treatment is performed, the heating temperature at the time of joining is set to 320 ° C, and the joining atmosphere is a reducing environment in which a N ₂ + H ₂ mixed gas is blown, the strength variation during mass production is large and very Although the probability is small, the fracture mode is 1 /
In some cases, interfacial peeling may occur over two or more times, and the connection reliability is inferior to the case where plating is provided.

In addition, as a measure to reduce the cost of the package manufacturing process and to improve the reliability of the package, hot-dip plating of solder, which was conventionally performed after assembling as a package, is performed in a lead frame state, at a temperature condition that does not melt solder, that is, at 160 ° C or less A package assembly method can be considered, but at a joining temperature of 160 ° C or less, the connection strength varies greatly even with the combination of materials with the best bondability, that is, the combination of Al pad, Au fine wire, and Ag plating lead. Some breakage occurs, and the connection reliability is significantly reduced.

An object of the present invention is to provide a bonding method that can lower a bonding temperature and a bonding pressure and obtain a connection portion having high bonding strength at an interface under soft bonding conditions.

Also, in the future bonding of the tape carrier and the Si chip, the number of terminals will increase in order to increase the density of elements, and at the same time, the terminal pitch will need to be significantly reduced. In the conventional method of forming and joining a melt by heating, the extruded melt comes into contact with an adjacent melt to form a bridge, thereby causing a circuit failure. In addition, since the thermal expansion of the organic film serving as the substrate of the tape carrier and the Si chip are different from each other, when bonding is performed at a high temperature, the position of the chip pad and the lead of the tape carrier are displaced, and a connection failure occurs. .

Therefore, the above problem can be solved by a joining method that does not form a melt, and if the joining temperature is lowered to near room temperature, the slight oxidation of the joining surface and the adsorption of moisture and gas will greatly increase the joining property. This makes it difficult to perform highly reliable bonding with the conventional solid-state bonding process.

Also, in conventional semiconductor devices, connection pads were arranged around the chip without elements, and damage to elements due to bonding was not a problem, but 64M-DRAM and ASIC
In a future semiconductor device represented by the above, the chip will be arranged immediately above the active element of the bonding pad in order to achieve high integration and miniaturization of the chip. In this case, the pressure and ultrasonic vibration at the time of bonding have a very high possibility of damaging the element under the pad, and it is necessary to perform the bonding while minimizing the pressure and vibration.
In addition, as a form of packaging an increasingly large chip, a method in which an adhesive is bonded to a die and a lead is also bonded to a chip surface has been applied. Due to the problem of bonding, bonding at a low temperature is required. For this reason, a solid-state bonding method with high connection reliability at low temperature and low pressure is required.

Another object of the present invention is to provide a bonding atmosphere at a low temperature of room temperature to 200 ° C. and a relatively high vacuum pressure of 10 ⁻² Pa or more.
An object of the present invention is to provide a method for achieving a solid phase bonding with high reliability.

[Means for solving the problem]

The present inventors have conducted intensive studies, and as shown in FIG. 1 schematically, the airtightness of the sample in the state before one step of solid-phase bonding was once evacuated to vacuum, as schematically shown in FIG. By introducing an inert gas and a reducing gas into a high chamber, and irradiating a laser beam or a hydrogen gas activated in a plasma or atomic state with a laser beam, reduction of an oxide film on a bonding surface and local heating of a surface adsorbed substance. Removal by
If the solid-phase wire bonding is performed in the same atmosphere where oxygen is eliminated as much as possible, it is possible to obtain a practically high strength bonding at a low temperature of room temperature to 200 ° C. even in an ultra-high vacuum atmosphere. I found that.

In FIG. 1, 1 is a Si chip, 2 is an Al pad, 3 is a lead frame, 4 is a die pad, 5 is a half sheet, 6 is a reducing gas shield, 7 is a heating table, 8 is a half fillet, 9 Is a vacuum chamber, 10 is a laser optical system, 11
Indicates a laser beam, 12 indicates a reducing atmosphere composed of an inert gas and a reducing gas in which oxygen gas is suppressed to 3000 ppm or less, 13 indicates a thin metal wire, 14 indicates a metal ball, 15 indicates a capillary, and 16 and 17 indicate a heating table. In the process, after performing die bonding under atmospheric pressure, surface treatment, transport, and solid phase wire bonding were performed in a vacuum chamber 9 maintained in a reduced-pressure reducing atmosphere.

Based on the above findings and to achieve the above object, the present invention relates to a solid-state bonding method used for a method of manufacturing a semiconductor device in which a semiconductor device and a lead are connected by using a thin metal wire, comprising a lead and a device. The present invention discloses and provides a solid-state bonding method characterized by performing laser irradiation or plasma irradiation on a surface of a connection pad under a low-pressure atmosphere and ultrasonically bonding a thin wire to each of the treated surfaces under the same atmosphere.

Low-pressure atmosphere with oxygen partial pressure of 3000 ppm or more and pressure of 10
Inert gas atmosphere ^-2 to 10 ² Pa or oxygen partial pressure 3000P,
It is desirable that the atmosphere be a reducing atmosphere containing hydrogen at a pressure of 10 ^-2 to 10 ² Pa at pm or less.

Preferably, the plasma gas used is an active gas containing hydrogen ions or hydrogen atoms, and the laser is YAG.
It is desirable to use a pulse laser of laser light or excimer laser light.

The present invention further provides an Al pad on the Si chip and a plating-less
A method of manufacturing a plastic package in which a Cu lead is connected with a thin metal wire and molded with a resin, and laser irradiation or laser irradiation and plasma irradiation are simultaneously performed on the bonding surface of the Cu lead under reduced pressure or reduced pressure and in a reducing atmosphere, Also disclosed and provided is a method of manufacturing a plastic package, which uses a solid-state bonding method in which ultrasonic bonding is performed at a temperature of 200 ° C. or less under the same atmosphere.

The solid-phase bonding method used is to oxidize the bonding surface of the plating-less Cu lead in advance, irradiate the bonding surface with a pulsed laser with a peak output of 10 kW or more in a vacuum or an inert or reducing atmosphere, and locally form a surface layer on the bonding surface. It is preferable to use a solid-phase bonding method in which the metal thin wire is ultrasonically bonded to the surface after the melting, and the bonding surface of the plating-less Cu lead is oxidized in advance. Ar and
It is particularly desirable that the mixed gas of O _{2 be} converted into plasma and irradiated and oxidized.

It is particularly effective that the thin metal wire used is Cu.

The present invention further provides a solid-state bonding apparatus used in a semiconductor device manufacturing apparatus for connecting a semiconductor device and a lead using a thin metal wire, comprising a surface treatment space for irradiating a laser or plasma to the surface of the lead and the pad. Also disclosed and provided is a solid-state bonding apparatus characterized in that a bonding processing space for sonic solid-phase bonding is provided in one airtight chamber under a pressure of 10 ^-2 to 10 ² Pa atmosphere.

The present invention further discloses a semiconductor device and the like manufactured by the solid-state bonding method according to the present invention.

(Operation)

The surface of the metal material once exposed to the atmosphere has an oxidized layer and an adsorbed layer of water, oil, fat, gas, etc., forming a chemically stable real surface. The oxidized layer and the adsorbed layer are chemically strongly bonded to the clean metal surface, and the only way to completely remove them is to decompose them by applying heat or to physically remove them. Further, unless the removal is performed in an atmosphere in which oxygen and adsorbed components are completely removed, the oxide layer and the adsorbed layer are immediately regenerated. For this reason, the conventional bonding process using a gas shield as shown in FIG. 10 cannot completely remove the oxide layer or the adsorption layer existing on the initial surface, and also removes oxygen and moisture in the atmosphere. Since complete elimination is not possible, an oxide layer is immediately formed even when a partially clean surface is formed, and these layers become obstacles and lower the bonding property at low temperatures.

On the other hand, in the method according to the present invention, it is possible to remove oxygen gas and moisture from the surrounding atmosphere to a level at which regeneration of the oxide layer and the adsorption layer can be prevented by putting the object to be joined in the vacuum chamber, In this environment, only the very surface of the lead to be bonded is instantaneously heated to a high temperature by irradiating a laser beam in that environment to vaporize moisture and oil adsorbed substances on the surface and almost completely remove it. The layer can also be almost completely metallized by thermal decomposition or reduction reactions, forming a clean and active metal surface.

According to the method of the present invention, as shown in FIG. 2, the surface of the lead to be joined can be almost completely cleaned, and the clean surface of the metal once formed can be retained only in the inert gas adsorption layer. If only the inert gas adsorption layer is used, it can be easily removed by ultrasonic vibration because it has only the bonding force of Van der Waals force, and the removed inert gas is easily removed as a gas from the bonding interface. Therefore, even with a low-temperature bonding process, it is possible to obtain a highly reliable joint due to close contact of a clean metal surface. In particular, by using laser irradiation or plasma irradiation as a cleaning means, the degree of vacuum in the vacuum chamber may be a relatively low degree of vacuum of about 10 ^-2 to 10 ² Pa. A plurality of cassettes loaded with a large number of workpieces in units of about ten minutes can be introduced into the vacuum chamber, and the process can be mass-produced.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 3 is an embodiment showing a joining apparatus for performing the joining process of the embodiment. In the figure, a large number of works 18 to which wires are solid-phase bonded are mounted on a cassette 41 and introduced from a work introduction chamber 37. The work introduction chamber 37 is repeatedly evacuated and opened to the atmosphere by the action of the gate valve 38 and the like. However, a vacuum pump 19 having a high evacuation speed is adopted so that this step does not limit the process. Vacuum chamber
The work 18 is sequentially sent out from the cassette 41 introduced into 34, and is composed of hydrogen gas and argon gas which are turned into plasma inside the quartz glass tube 21 provided in the microwave waveguide 22 of the microwave oscillator 23. The plasma gas 20 is irradiated. Reference numeral 25 denotes a gas introduction valve to the quartz glass tube 21.

In this embodiment, at the same time, the laser beam 26 generated from the laser oscillator 31 is
9, the work 18 is irradiated through the vacuum window 28 and the optical lens system 27.

The work cleaned by the irradiation of the plasma gas containing hydrogen and the laser beam is transported to the position where the bonding device 33 is arranged, and the thin metal wire 32 is solid-phase bonded by ultrasonic bonding without heating. The work after the solid-phase bonding is completed is stored in a take-out cassette 42, taken out through the gate valve 39 and into the atmosphere via the work take-out chamber 40, and the assembly process is completed. The work take-out chamber 40 is also evacuated by the vacuum pump 100 similarly to the work introduction chamber.

In the plasma generating section in the microwave waveguide, heat is generated in accordance with the output of the microwave. Therefore, a cooling mechanism including a water cooling pipe 24 and the like is provided to protect the quartz glass tube. In addition, for the exhaust inside the vacuum chamber, a turbo molecular pump that can continuously exhaust while introducing gas and has a wide operating range is adopted as the vacuum pumps 35 and 36, and the degree of vacuum will be 10 ^-1 Pa or less Control.

According to the present embodiment, in a semiconductor package using a Cu-based lead frame, even when the lead surface to be joined is oxidized or has an adsorption layer of moisture or oil, the surface is cleaned under a completely controlled atmosphere. And solid phase bonding can be performed, so that occurrence of bonding failure can be prevented, and the ratio of the true bonding surface in the bonding surface can be increased to improve the strength of the joint. Therefore, the yield of the product can be improved and the reliability of the joint can be greatly improved.

At this time, although the process of introducing the work into the vacuum chamber and assembling is adopted, the degree of vacuum is not as high as 10 ^-2 to 10 ² Pa, so the throughput is significantly reduced compared to the conventional process performed in ultra-high vacuum. There is no problem as a semiconductor package mass production process. In addition, since the effect of the surface cleaning treatment significantly improves the bondability with Au fine wires and Cu fine wires, a high-strength joint can be obtained even under low-temperature and low-pressure conditions. A low cost semi-advanced assembly process can be employed, such as pre-coating.

Furthermore, the effect of improving the bondability enables high-strength bonding without increasing the amount of crushing of the fine metal wire in wedge bonding. In this case, it is possible to eliminate the variation in strength and the occurrence of peeling failure due to the above, and it is possible to obtain effects such as an increase in the tolerance of the adjustment accuracy of the apparatus and an increase in the use limit of the capillary.

FIG. 4 shows another embodiment of the surface treatment process in FIG. Microwave oscillator 46 in this embodiment
As shown in the figure, the microwave waveguide 45 is provided with a plurality of nozzle openings for irradiating the plasma gas 44, and has a structure for irradiating the strip-shaped region with the plasma gas. The laser beam 48 is arranged so as to irradiate the surface of the work 43 irradiated with the plasma gas, and the shape of the laser beam is also extended linearly to the width of the work by the cylindrical lens 49. In the figure, 47
Denotes a gas introduction pipe to the waveguide 45, 50 denotes an optical system for a laser beam, and 51 denotes an optical fiber.

According to the present embodiment, since the irradiation region of the plasma gas and the laser beam is wide in a band shape, it is necessary to move the work in the feed direction without scanning the plasma gas or the laser beam and to perform the solid-state joining of the work. An effect is obtained that the entire surface can be cleaned and the configuration of the device can be simplified. Also, since large surfaces can be processed at once,
The effect that the time required for the surface treatment can be shortened is also obtained.

In this embodiment, since the laser beam is irradiated while irradiating the same surface with hydrogen plasma, the reduction effect by active hydrogen, the decomposition effect of the oxide layer by the heating of the laser, and the effect of accelerating the reduction phenomenon are obtained. Has the effect of being able to clean the surface more reliably and in a shorter time, and has the effect of preventing the occurrence rate of bonding failures due to insufficient cleaning and preventing the spread of strength variation to a lower level from occurring. is there.

FIG. 5 shows another embodiment of the surface treatment process of FIG. In this embodiment, the surface treatment process is divided into two stages, and an oxidizing gas is used in the first stage and a reducing gas is used in the second stage. In this embodiment, the work introduction chamber is the same as in the first embodiment.
101, having a gate valve 102, a vacuum chamber 103,
The vacuum chamber comprises two chambers, a first vacuum chamber 55 and a second vacuum chamber 69. Work 52 is a work introduction room
The oxygen is introduced from 101 into the first vacuum chamber 55, which is a reduced-pressure oxidizing atmosphere, by the introduction cassette 57, and the work 52 sent out from the cassette is irradiated with the oxygen plasma gas 53 generated by the oxygen plasma generator 54.

At this time, organic substances such as fats and oils on the surface of the lead of the work are oxidized and are removed from the surface of the lead as carbon dioxide, water, nitrogen dioxide and gas. At the same time, the lead surface of the work is oxidized, and the surface of the copper alloy lead frame is discolored.

The workpiece after the first-stage surface treatment is transferred to the transfer cassette 58.
And is sent to the second vacuum chamber 69 via the transfer chamber 61 separated by the gate valves 60 and 62. The second vacuum chamber is in a reduced-pressure reducing atmosphere, and workpieces whose lead surfaces are oxidized are sequentially sent out from a cassette 71 introduced into the second vacuum chamber 69, and a hydrogen plasma gas generated by a hydrogen plasma generator 65 is produced. The laser beam 64 and the laser beam 66 are irradiated simultaneously. In this embodiment, the laser is YAG
A laser is used. In general, light with a wavelength of 1.06 μm is reflected by 98% or more on a metallic glossy surface of a copper alloy, which is extremely inefficient. However, by oxidizing the surface, the absorption rate is improved by one digit or more, and the surface is heated. Can be performed efficiently. After the lead surface to be joined is reformed into a clean metal surface by instantaneous high-temperature heating of the pole surface by an active reducing gas and a laser, a joining step similar to that shown in FIG. In the drawing, 59, 63, and 72 are vacuum pumps for evacuating the respective chambers, and 67 is a laser beam 66.
The optical system 68 is for that purpose.

According to the present embodiment, since the strong oxidation treatment is performed using very active plasma or atomic oxygen in the first-stage surface treatment, the organic film or the press formed intentionally in the lead frame production process is used. Oil and the like adhering in the process are removed from the lead surface by an oxidation reaction, and the low temperature process oxidizes the extreme surface of the copper alloy lead, but the inside of the lead diffuses oxygen very slowly, so the metal cleanliness Can be maintained. As a result, the energy of the laser beam can be effectively activated in the second-stage surface treatment, and the oxide film on the surface can be completely decomposed and removed in a short time. In other words, it is possible to completely and reliably remove organic dirt and adsorbed substances that may become carbon and remain on the surface by simply treating in a reducing atmosphere, and to perform ultrasonic bonding at a low temperature. This makes it possible to remarkably reduce the properties and eliminate the influence of surface inclusions, which has been a major factor in the variation in strength.

Further, according to the present embodiment, since the energy efficiency of the laser beam can be increased, the output of the laser oscillator can be reduced, and the cost of the device can be reduced.

Further, the effect of the present embodiment on the improvement of the strength reliability and the product yield of the wire bonding portion is the same as that of the embodiment shown in FIG.

FIG. 6 shows an assembly structure when a memory device is packaged by applying the low-temperature solid-state bonding method according to the present invention. In this example, the package form of the semiconductor memory is such that the connection pad 76 is an active area 75 of a Si chip 74.
The ball bonding of the thin metal wire 78 needs to be performed with low pressure and low ultrasonic output. In addition, since the elements are densely integrated and the heat generation density increases, the package cooling mechanism is adopted, but the operating temperature rises, and the intermetallic compound grows at the bonding interface with the conventional combination of Al pad and Au ball, Long-term reliability as a device decreases.

Therefore, in the embodiment shown in FIG. 6, at least one metal selected from Ta, Nb, V, Ni, Pd, Pt, Zr, and Hf is formed on an Al pad made of the same material as the wiring material of the element. Is formed to a thickness of 2 μm or less, and the pad surface is irradiated with a laser beam while irradiating a hydrogen plasma gas in a reduced-pressure reducing atmosphere, and in the same atmosphere, the Au thin wire is 40 gf or less with a low load and a low ultrasonic output. A ball bonding 78 is performed, and a bonding surface of a lead 79 made of a copper alloy or an iron-nickel alloy is subjected to the same surface treatment as that of the pad surface, and is then assembled by wedge bonding 80.

According to the present embodiment, since a metal that is less likely to form a compound with Al than Au is provided as an intermediate material on the Al pad,
The growth of the intermetallic compound at the bonding interface during use of the device is small, and the long-term reliability of the device is improved. Also, at the time of ball solid-phase bonding, since the surface oxide layer of the intermediate material provided on the Al pad is easier to decompose and remove than the surface oxide layer of Al, an active clean surface can be obtained and low pressure can be obtained. It becomes possible to obtain a high-strength joint under conditions of weak ultrasonic vibration. This prevents a large stress or strain from being applied to the active layer under the pad, thereby preventing device damage during the assembly process, and improving the bondability, thereby improving the assembly yield. Becomes

As another embodiment of FIG. 6, when a Cu-based alloy is used for the device wiring, the pad is also formed of the Cu-based alloy, and the intermediate material in this case is selected from Au, Pt, and Pd.

In this embodiment, the same effects as in the embodiment of FIG. 6 can be obtained. Furthermore, since these intermediate materials have much higher corrosion resistance than Cu, there is an effect that corrosion of the pad due to humidity during use of the device, and corrosion damage of the wiring due to moisture intrusion from the pad portion caused thereby can be prevented. .

FIG. 7 shows a TAB mounting structure of a semiconductor device assembled by the solid-state bonding process of the present invention. In the figure, a semiconductor device 104 is bonded to a Cu lead 108 on which an Au plating 107 has been applied by a solid-state bonding method of the present invention by an Au bump 106 formed on an Al pad 105 via a barrier metal. 109 is a polyimide film, and 110 is a tape-shaped wiring board.

According to the present embodiment, the Au bump and the Cu lead can be bonded with high strength in the solid state, so that even if the terminal pitch is 60 μm or less, there is no short circuit with the adjacent one and no heating is performed, so that the bump is not heated. The positions of the leads and the leads do not shift due to thermal distortion or the like, and mounting at a fine pitch is possible. In addition, because of the Au / Au junction, a fragile intermetallic compound is not formed at the junction interface, and a semiconductor device with high connection reliability can be manufactured for a long time.

FIG. 8 shows a connection structure of liquid crystal panel terminals assembled by the low-temperature solid-state bonding process of the present invention. In the figure, an Au-plated Cu lead 115 of a flexible wiring board 117 is bonded to a wiring 112 formed on a glass substrate 111 via a thin Au wire 113. The method of bonding was to set the Au thin wire in the direction of the arrangement of the terminals on the glass substrate, clean the surface with a laser or plasma gas in a reduced-pressure atmosphere from above, and perform the surface cleaning treatment in another step. The lead is placed on the Au thin wire in accordance with the terminal position, and pressure is applied while applying ultrasonic waves from above to crush the thin wire for bonding.
After bonding, the Au thin wires between the terminals are cut and removed by a pulse laser of YAG or excimer to prevent short-circuits and finish in a good connection state.

According to the present embodiment, since the liquid crystal glass substrate and the flexible wiring substrate can be joined to each other with a high strength without a half, the joining strength and the fatigue life at a high temperature are high, and the reliability as a liquid crystal display device can be very high.

Also, there is no need to form Au bumps at the junction,
Since it is only necessary to set Au thin wires that do not require alignment, the joining process is simplified and productivity can be improved.

FIG. 9 shows a cross-sectional structure of a thin-film module substrate assembled by the low-temperature solid-state bonding process of the present invention. In the figure, a first thin film element substrate 119 is formed on a ceramic substrate 118 by a thin film process. An Au connection pad 120 for joining the second element substrate 122 is formed on the upper surface of the first element substrate. Au bumps 121 for bonding to the first element substrate are formed on the lower surface of the second element substrate, and Au bonding pads 123 for bonding the third element substrate 125 to the upper surface of the second element substrate. Are formed. On the upper surface of the uppermost element substrate 125, fine connection pads 126 for mounting a Si chip are formed.
The low-temperature bonding method according to the present invention is used for bonding between the element substrates. Also, each element substrate is 1-5
This is a thin-film module substrate including a plurality of wiring layers.

According to the present embodiment, even if the connection pads between the element substrates are fine and the pitch is minute, they are not heated in the bonding process. The displacement can be easily prevented, and the connection strength is high, so that the reliability as a thin film module substrate can be increased. Also, this manufacturing process is different from the conventional sequential assembly method in which all the steps are manufactured by a thin film process. Moreover, the assembly time to the final product can be greatly reduced.

〔The invention's effect〕

As described in detail above, according to the present invention, even when the lead surface to be bonded has an adsorption layer such as an oxidized amount, moisture, oil, or gas, or a coating of an organic substance, the thermal and plasma gas and laser beam The metal surface can be completely cleaned by chemical action, and can be held and bonded in a reduced-pressure reducing atmosphere where there is almost no oxygen or moisture. Under the joining conditions of low pressure and ultrasonic energy, the occurrence of poor joining is very small, and a highly reliable joint having high joint strength and small variation in strength is obtained.

As a result, the assembly yield and reliability of semiconductor packages using plating-less lead frames have been improved, and chip damage and deterioration of element performance due to solid-state coupling of future DRAM memory devices with pads formed in active areas have been prevented. To improve the assembly yield of fine and narrow pitch terminal connections in TAB mounting of semiconductor devices, improve the connection strength and fatigue life of liquid crystal panel terminal connections, shorten the manufacturing process of thin film module substrates, and improve product reliability. You can do it.

[Brief description of the drawings]

FIG. 1 is a view showing a solid-phase wire bonding of a chip according to the present invention, FIG. 2 is a view showing a principle of improving the bonding property in the solid-phase bonding method of the present invention, and FIG. 3 is a joining method of the present invention. Showing an embodiment of a bonding apparatus for performing the bonding, FIG. 4 and FIG.
FIG. 6 is a view showing an embodiment of an apparatus for performing surface treatment, FIG. 6 is a view showing an example of an assembly structure of a memory device to which the present invention is applied, and FIG. FIG. 8 shows an example of a joint structure, FIG. 8 shows an example of a connection structure of a liquid crystal panel terminal to which the present invention is applied, and FIG. 9 shows a cross-sectional structure of a thin film module substrate assembled by applying the present invention. FIG. 10 is a diagram showing a conventional wire bonding process, and FIG. 11 is a diagram showing an assembly structure of a conventional memory device. 1: Si chip, 2: Al pad, 3: Lead frame, 4: Die pad, 5: Half sheet, 6: Reducing gas shield, 7: Heating table,
8: half fillet, 9: vacuum chamber, 10: laser optics, 11: laser beam, 12 reducing atmosphere, 13: thin metal wire, 1
4: Metal ball, 15: Capillary, 16, 17: Heating table, 18: Work, 19: Vacuum pump, 20: Plasma gas, 21: Quartz glass tube, 22: Microwave waveguide, 23: Microwave oscillator, Two
4: water cooling pipe, 25: gas introduction valve, 26: laser beam,
27: Optical lens system, 28: Vacuum window, 29: Lens, 30: Optical fiber, 31: Laser oscillator, 32: Fine metal wire, 33: Bonding device, 34: Vacuum chamber, 35, 36: Vacuum pump, 37: Work Introducing room, 38, 39: gate valve, 40: work take-out room, 41, 42: cassette.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Setsuo Sekine 2880 Kozu, Odawara City, Kanagawa Prefecture Inside the Odawara Plant of Hitachi, Ltd. (56) References JP-A-4-123430 (JP, A) JP-A-3-159143 (JP, A)

Claims (8)

(57) [Claims] 1. A solid-state bonding method used in a method of manufacturing a semiconductor device in which a semiconductor device and a lead are connected by using a fine metal wire, wherein laser irradiation or plasma is applied to the surface of the lead and the connection pad of the device under a low-pressure atmosphere. A solid-phase bonding method comprising irradiating and ultrasonically bonding a fine wire to each treated surface under the same atmosphere. 2. A solid phase bonding method of claim 1, wherein the low pressure atmosphere is an inert gas atmosphere at a pressure below the oxygen partial pressure of 3000ppm 10 ^-2 ~10 ² Pa. 3. A solid phase bonding method of claim 1, wherein the pressure in the low pressure atmosphere less oxygen partial pressure 3000ppm is a reducing atmosphere containing hydrogen of 10 ^-2 ~10 ² Pa. 4. A method of manufacturing a plastic package in which an Al pad of a Si chip and a plating-less Cu lead are connected by using a thin metal wire and molded with a resin, and the bonding surface of the Cu lead is subjected to reduced pressure or reduced pressure and reducing atmosphere. A laser irradiation or a laser irradiation and a plasma irradiation at the same time, and a solid-state bonding method of performing ultrasonic bonding at a temperature of 200 ° C. or lower under the same atmosphere. 5. A solid phase bonding method comprising: oxidizing a bonding surface of a plating-less Cu lead in advance; irradiating the bonding surface with a pulse laser having a peak output of 10 kW or more in a vacuum or an inert or reducing atmosphere; After locally melting the surface layer,
5. The method for manufacturing a plastic package according to claim 4, wherein the method is a solid-state bonding method in which a thin metal wire is ultrasonically bonded to the surface. 6. A method for pre-oxidizing a bonding surface of a plating-less Cu lead by oxidizing the bonding surface of a plating-less Cu lead by irradiating a mixed gas of Ar and O ₂ with plasma. Item 6. The method for producing a plastic package according to Item 5. 7. A solid-state bonding apparatus used in a semiconductor device manufacturing apparatus for connecting a semiconductor device and a lead using a thin metal wire, wherein a surface treatment space for irradiating laser or plasma to the surface of the lead and the pad is provided. A solid-state bonding apparatus, wherein a bonding processing space for sonic solid-phase bonding is provided in one airtight chamber under a pressure of 10 ^-2 to 10 ² Pa. 8. The semiconductor device according to claim 1, wherein Ta, Nb, V,
Metals selected from Ni, Pd, Pt, Zr, and Hf are formed to a thickness of 2 μm or less, and Au or Cu fine wires are ball-solid bonded or wedge solid bonded to the surface. A semiconductor device manufactured by the solid-state bonding method according to claim 1.