CN102543784B - Solid-state hot-compression low-temperature bonding method using nickel micro needle cones - Google Patents
Solid-state hot-compression low-temperature bonding method using nickel micro needle cones Download PDFInfo
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- CN102543784B CN102543784B CN201210085365.XA CN201210085365A CN102543784B CN 102543784 B CN102543784 B CN 102543784B CN 201210085365 A CN201210085365 A CN 201210085365A CN 102543784 B CN102543784 B CN 102543784B
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Abstract
The invention provides a solid-state hot-compression low-temperature bonding method using nickel micro needle cones. A layer of metallic nickel featured by being bestrewed with needle cones is manufactured on one side of a to-be-bonded welding spot, and welding flux is used on the other side of the to-be-bonded welding spot. A colligator is used for being aligned with the electrically interconnected welding spot, the welding spot is heated to a certain temperature not higher than the solder cap melting point, and a bonding pressing force is exerted and maintained for some time so that inlay bonding of needle cones and welding flux at the position of the interconnection point is achieved. A thin layer of precious metal is electroplated on the layer of nickel micro needle cones to prevent the surface from being oxidized prior to bonding. After bonding is finished, the welding spot is placed at a certain temperature for heat treatment for some time to achieve diffusion reaction and remove holes. The solid-state hot-compression low-temperature bonding method using nickel micro needle cones is capable of overcoming some defects in the prior art in novel encapsulation technology application, avoids thermal damage caused to components by reflow soldering process temperature, and resolves the problems of welding flux spreading in molten welding and solid-liquid phase fast reaction.
Description
Technical field
The present invention relates to semiconductor die package field, specifically by the use of surperficial special pin taper looks metal level, realize the method that interelement solid interconnect engages.
Background technology
Micro-interconnection technique of semiconductor die package is just constantly reformed, and in chip manufacturing now, interconnection technique mainly contains: lead frame type; Bonding; Ball grid array; QFN; Flip-chip; Bump bonding; Band carries; The technology such as 3D encapsulation.The innovation of electrical interconnection technology is the key of microelectric technique development, and traditional melting bonding techniques is to make the metal molten at bonding point place drench bonding point both sides by the control of temperature, and cooling rear bonding point solidifies, thereby obtains good welding, for example reflow welding.
More than the techniques such as traditional reflow welding need to be brought up to the fusing point of scolder by welding temperature, high temperature environment can produce ill effect to some chip or substrate, reduces the reliability of product.Need to use to the plumbous salient point of the height of using till today in the Flip Chip Bond Technique of base plate for packaging the lead that environment is produced to harm at chip, and alternative lead-free solder there is no method and reaches identical or lower with it welding temperature.The method of fusion welding needs to prevent the crossover phenomenon occurring between solder joint simultaneously.
In order to reach desirable bond strength, sometimes need to use the organic substances such as scaling powder, binding agent.It is upper that scaling powder need to be added at least one combined surface, and scaling powder comprises matchmaker's liquid and activator.Solder flux matchmaker liquid plays during refluxing for the second time the surface of scolder and isolated from atmosphere is opened, and reduces the risk of scolder high-temperature oxydation, and activator is organic acid or inorganic acid normally, with the oxide-film that removes solder surface, to improve wetability.After welding completes, need to remove solder flux or flux residue, generally include and use solvent clean packaging part, or through baking process, with remaining solvent or lower boiling solder flux or the flux residue of volatilizing.The using and remove residue and will expend certain production time of scaling powder, and when chip and chip chamber, or space between chip and substrate is less time, and flux residue is just more difficult to be removed completely.
Seeking low welding temperature has been a main trend of the development of chip interconnects technology.Nowadays have many pertinent literatures and patent, the chip of describing non-melting method realization arrives the interconnection process of chip-stack to substrate or chip.Comprising utilizing the monometallic of low melting point or alloy (being associated gold etc. as indium), mechanical means to embed the multiple technologies such as metal derby or metal salient point, active reaction layer, nano particle low-temperature sintering.Generally speaking, solid-state electrical interconnection is significantly improved interconnection density because having avoided fusion weld, without scaling powder, and can eliminate the excessive interfacial reaction that bond strength and reliability are had a negative impact occurring between pad on scolder and substrate in melting process, and due to the reduction of technological temperature, technological process and expense are also reduced.
The solid-state bonding of copper-copper has multiple report, and wherein, surface active bonding (SAB) technology can realize temperature and be low to moderate the atom level connection between the various metals under room temperature.Generally pass through meticulous chemico-mechanical polishing to reach nanoscale evenness for realizing the copper surface of surface active bonding, the approach that obtains overactive metal surface comprises ar atmo, ion, plasma treatment etc.After oxide on surface and pollution are eliminated, the chip or the crystal column surface that complete activation need vacuum protection to control the speed of oxidation again, and complete Direct Bonding under higher vacuum degree.Comprise that the solid-state a series of high-flatness metal-metal characteristics of Direct Wafer Bondeds based on surface active in being bonded in of copper-copper have quite high requirement to the processing technology of wafer, and be often used for wafer level interconnection.
For the feature of some device elevated operating temperature, also there are new bonding material and technical system exploitation to replace the tin solder that cannot bear high temperature, for example, indium metal is considered to a kind of promising soldered metal owing to having compared with low fusing point, at present the use of encapsulation field indium is mainly studied to be embodied in and utilize indium and other solder metal layers, as silver, tin, copper, gold etc., reaction produces the intermetallic compound of higher melt.For example utilize silver and the tin thin film of sandwich construction to be aided with contact at approximately 180 DEG C, silver supersaturation and solid products such as generation in the indium of liquid phase, thus realize the welding of technological temperature lower than traditional lead-free solder.
The bonding techniques that uses nano-metal particle to realize also has report widely, what the most often use is nano-Ag particles, because metallic particles is in the time that diameter reaches nanoscale, sintering temperature with size dwindle and surface can increase and obviously reduce, also the temperature of fusion weld can be significantly less than, even be low to moderate sintering bonding under the condition of room temperature, obtain the solder joint with high-temperature stability.The preparation of nano-Ag particles can obtain by the solvent of drying in gel, and for the silver-colored particle that is about 100 nm for diameter, bonding can carry out under the pressure of the temperature of 300 DEG C, 25 MPa, and the shear strength of acquisition is more than 10 MPa.This method, because solder joint has quite high conductivity and thermal conductivity, has wider prospect of the application in high-power components and the encapsulation of large-area chips array type.
Summary of the invention
The present invention is directed to the technical problem existing in above-mentioned prior art, a kind of solid state heat compression low-temperature bonding method that uses nickel micropin cone is proposed, this method can overcome technique some defects in new encapsulation technology application in the past, the fire damage of avoiding reflow soldering process temperature to produce device, and in fusion weld, scolder is sprawled and solid liquid phase rapid-action problem.
For achieving the above object, the technical solution adopted in the present invention is as follows:
A solid state heat compression low-temperature bonding method that uses nickel micropin cone, comprises following steps:
1), select to have mutual coupling electrical interconnection pad treat bonding element;
2), on a wherein side pad for the treatment of bonding idol, form surface part by soft the first metal, the projection that bottom is made up of the second metal;
3), on the pad of opposite side for the treatment of bonding idol, prepare nickel micropin cone layer;
4), engage and treat bonding element, comprise will treat the even surface pads of bonding aim at, make each nickel micropin on multiple projections with soft alloy and opposite side surface bore Region Matching; And contact area is heated to the first temperature, and make contact both sides to complete the electrical interconnection bonding of welding disking area.
Adopt electrodeposition process (including but not limited to the method such as chemical plating, vapour deposition) at element electrical interconnection regional metal piece (as the substrate of flip chip bonding, or the PCB side pad of ball grid array type encapsulation, utilize the method such as photolithography patterning, chemical corrosion to form) on prepare nickel micropin cone layer; Electro-deposition parameter by control including time, current density, additive concentration, controls pin cone height by 200 nanometers to 2000 nanometers not etc.
Prepare after nickel micropin cone film, prepare antioxidation coating on surface, antioxidation coating is oxidation resistant metal or alloy under high temperature, and thickness is about several nanometers to tens nanometer, and does not change the surface topography of pin cone, includes but not limited to plating, CVD (Chemical Vapor Deposition) method;
This noble metal can be Au, Pt, Ag, Pd;
Use connector to aim at and treat that bonding is even, make the identical pin cone film region of shape mate one by one and aim at solder projection region;
The bonding that heating has been aimed at is even to suitable temperature, apply a bonding pressure, wherein bonding pressure need to keep the several seconds to arrive several minutes during the first temperature, then release key resultant pressure, and the optimized results that the retention time is required by solder metal kind, temperature, bonding pressure determines.
According to concrete use occasion, in the scope lower than 5-100 DEG C of solder metal fusing point, select this temperature;
Bonding pressure generally, between 1-20 MPa, determines according to bonding temperature;
Time generally, between 5 s-20 min, determines according to bonding pressure and bonding temperature;
The second metal of salient point lower floor is prepared by electrodeposition process;
Wherein the first metal cap of bump surface has compared with low melting point, prepares by electrodeposition process;
Wherein be heated to the first temperature and can pass through contact or contactless mode of heating, the first temperature is no more than the fusing point of the first metal and solder metal, and the optimized results that the first temperature is required by the first metal species and bonding pressure determines;
To treat that bonding is occasionally positioned over respectively in hot compression connector the first and second fixtures, keep temperature lower than the first temperature, by first or second fixture one or both of movement each other, the pad metal piece that makes the multiple soft alloy projections of a side and opposite side surface be prepared with micropin cone contacts with each other, make temperature reach fast the first temperature and keep by heater, between the first and second fixtures, exert pressure and keep simultaneously, until contact point place realizes bonding, take off from connector the element that bonding completes;
At the second temperature, through after a while
theat treatment, improve Joint Properties
This temperature is generally lower than bonding process technological temperature.
Because nickel micropin wimble structure has that real surface is long-pending large, high reaction activity under micro-nano-scale and the special feature such as sharp-pointed structure and array form, and there are many new functional characteristics, and can be applied in Electronic Packaging industry.The present invention utilizes under it and higher temperature significantly softening solid-state lead-free solder cap to obtain good mechanical snap, thereby the long-pending counterdiffusion that can promote combination interface of huge real surface improves adhesion etc.
The solid state heat compression bonding method of use nickel micropin disclosed in this invention cone is by the temperature lower than scolder fusing point and apply under the condition of certain pressure, and solder layer and nickel micropin cone thin layer generation mechanical snap and diffusion reaction are realized.Advantage and the good effect of the method are: in technical process, scolder does not melt, and solid-state bonding can improve interconnection density and product reliability, have controlled interfacial reaction characteristic, without organic substances such as scaling powders thereby simplified technological process.
Embodiment
Below in conjunction with embodiment, the present invention is described in further detail:
embodiment 1:
on the bare chip with I/O pad, form the tin layer of ubm layer (UBM), copper pillar bump, nickel barrier layer and bump surface by techniques such as standard photolithography patterning, sputtering sedimentation and electrochemical depositions, typical copper pillar bump is of a size of diameter 60 μ m, height 40 μ m.Typical nickel barrier layer thickness is about 1 μ m.Typical tin thickness is 5 μ m, and difference in height is less than 0.5 μ m.Welding disking area at upside-down mounting substrate is prepared nickel micropin cone layer and surface anti-oxidation gold layer by chemical deposition or electrochemical deposition, and integral thickness is about 5 μ m, surperficial pin cone height approximately 1 μ m, golden thickness approximately 10 nm.The gold plate of this thickness can not exert an influence to pin taper looks.To remove the chip of bump surface oxide layer with pickling, and substrate face opposite is fixed on flip-chip bonder and aim at, is warming up to rapidly the bonding temperature of 180 DEG C, and is applied the equivalent static pressure of 10 MPa simultaneously by bonder, keep 5min, complete preliminary bonding.In the process of preliminary bonding, the nickel micropin bore spine that hardness is higher enters block tin, and soldering layer at high temperature hardness significantly declines, and creep rate is accelerated, and becomes to inlay with pin taper by plastic deformation, forms mechanical bond.The distortion that in this process, hot compression produces is between 1-3 μ m.Complete after preliminary bonding; chip is placed in to 140 DEG C of protective atmosphere heat treatment 6h; the nickel fitting tightly in this process and tin generation interfacial reaction form certain thickness intermetallic compounds layer, and in preliminary bonding process, residual hole is eliminated by diffusion simultaneously.
embodiment 2
Form ubm layer (UBM) and tin layer with I/O pad, the back side with passing through interconnecting silicon through holes (TSV) to the positive I/O pad of bare chip of device side in front, typical tin thickness is 2-5 μ m, and difference in height is less than 0.5 μ m.Chip has been thinned to below 100 μ m conventionally, polishes overleaf also exposed TSV filling metal surface and prepares nickel micropin cone layer and surface anti-oxidation gold layer, and integral thickness is about 5 μ m, surperficial pin cone height approximately 1 μ m, golden thickness approximately 10 nm.Use plasma remove surface oxide layer and stain after particle, two or multi-disc are prepared with to stacking being fixed in bonder of silicon chip of this structure, be warming up to the bonding temperature of 180 DEG C, and applied the equivalent static pressure of 7.5 MPa simultaneously by bonder, keep 5min to complete preliminary stacking bonding.Complete after preliminary bonding, chip is placed in to 140 DEG C of protective atmosphere heat treatment 6h to improve bond strength.
embodiment 3
Prepare nickel micropin cone layer and surface anti-oxidation gold layer on for the surface-pasted welding disking area metal derby of ball grid array (BGA) type at printed substrate (PCB), integral thickness is about 5-10 μ m, surface pin cone height approximately 1-2 μ m, golden thickness approximately 10 nm.Carry out pickling processes to remove soldered ball surface oxide layer by being implanted with size at the BGA packaging body of 300-800 μ m ashbury metal soldered balls, and fix in bonder with PCB and aim at, be warming up to the bonding temperature of 180 DEG C, and applied the equivalent static pressure of 10 MPa by bonder simultaneously, keep 5min to complete preliminary stacking bonding.Complete after preliminary bonding, chip is placed in to 140 DEG C of protective atmosphere heat treatment 6h.
In above description, for the purpose of illustrating and many concrete details of setting forth, but protection scope of the present invention is not limited to this, can not exclusively implement the present invention according to the details of the operation providing or instrument here.
For example, stud bump material can be the nickel of electro-deposition and be not limited to copper, and solder caps material can be selected the low-melting-point metals such as indium, or other have the alloy compared with low melting point.Flip-chip interconnection and multi-chip stacking perpendicular interconnection for chip to substrate, the position of salient point side and pin cone flank can exchange.Even not using thermocompression bonding machine, and realize the content of the claims in the present invention with miscellaneous equipment, is easy to do to one skilled in the art.Equally, the order of the cooperation of temperature requirement and pressure in bonding process, also can for example adjust according to the needs of practical operation.
Claims (8)
1. a solid state heat compression low-temperature bonding method that uses nickel micropin cone, is characterized in that, comprises that step is as follows:
1), select to have mutual coupling electrical interconnection pad treat bonding element;
2), on a wherein side pad for the treatment of bonding idol, form surface part by soft the first metal, the projection that bottom is made up of the second metal, described the first metal thickness is 5 μ m, difference in height is less than 0.5 μ m;
3), on the pad of opposite side for the treatment of bonding idol, prepare nickel micropin cone layer, the preparation of nickel micropin cone film realizes by electrodeposition process, electro-deposition parameter by control including time, current density, additive concentration, nickel micropin cone height in 200 nanometers between 2000 nanometers;
4), engage and treat bonding element, to treat that bonding is occasionally positioned over respectively in hot compression connector the first and second fixtures, keep temperature lower than the first temperature, by first or second fixture one or both of movement each other, the pad metal piece that makes the multiple soft alloy projections of a side and opposite side surface be prepared with micropin cone contacts with each other, make temperature reach fast the first temperature and keep by heater, wherein bonding pressure need to keep 5 seconds to 20 minutes during the first temperature, in the scope of described the first temperature lower than 5-100 DEG C of solder metal fusing point; Between the first and second fixtures, exert pressure and keep simultaneously, described bonding pressure is between 1MPa to 20MPa, until contact point place realizes bonding, takes off from connector the element that bonding completes;
5), at the second temperature, through the heat treatment of t after a while, improve Joint Properties.
2. the solid state heat compression low-temperature bonding method of use nickel micropin cone as claimed in claim 1, it is characterized in that, prepare after nickel micropin cone film, prepare antioxidation coating on surface, antioxidation coating is oxidation resistant metal or alloy under high temperature, thickness arrives tens nanometer for counting nanometer, and does not change the surface topography of pin cone.
3. the solid state heat compression low-temperature bonding method of use nickel micropin cone as claimed in claim 1, it is characterized in that, wherein bonding pressure need to keep the several seconds to arrive several minutes during the first temperature, then release key resultant pressure, the optimized results that the retention time is required by solder metal kind, temperature, bonding pressure determines.
4. the solid state heat compression low-temperature bonding method of use nickel micropin cone as claimed in claim 1, is characterized in that, the second metal of its bumps lower floor is prepared by electrodeposition process.
5. the solid state heat compression low-temperature bonding method of use nickel micropin cone as claimed in claim 1, is characterized in that, wherein the first metal cap of bump surface has compared with low melting point, prepares by electrodeposition process.
6. the solid state heat compression low-temperature bonding method of use nickel micropin cone as claimed in claim 1, it is characterized in that, wherein be heated to the first temperature by contact or contactless mode of heating, the first temperature is no more than the fusing point of the first metal and solder metal, and the optimized results that the first temperature is required by the first metal species and bonding pressure determines.
7. the solid state heat compression low-temperature bonding method of use nickel micropin cone as claimed in claim 1, is characterized in that, wherein temperature and contact keep the several seconds by several minutes, are to be determined by the optimized results of the first metal species, temperature, pressure requirement.
8. the solid state heat compression low-temperature bonding method of use nickel micropin cone as claimed in claim 1, is characterized in that, wherein the second temperature is determined by the optimized results of the first metal species and retention time t.
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| CN105097427A (en) * | 2014-04-23 | 2015-11-25 | 中芯国际集成电路制造(上海)有限公司 | Method for monitoring pre-cleaning technology of metal intermediate layer before wafer bonding |
| CN104112707B (en) * | 2014-07-03 | 2018-07-03 | 上海交通大学 | A kind of solid ultrasonic bonding method based on nickel and copper micropin cone foreign structure |
| CN104112682A (en) * | 2014-07-03 | 2014-10-22 | 上海交通大学 | Solid-state ultrasonic bonding method based on nickel microneedle cones of the same structure |
| CN104112681A (en) * | 2014-07-03 | 2014-10-22 | 上海交通大学 | Solid-state ultrasonic bonding method based on copper microneedle cone |
| CN104112684A (en) * | 2014-07-03 | 2014-10-22 | 上海交通大学 | Solid ultrasonic bonding method based on nickel micro cones |
| CN106744665A (en) * | 2016-11-29 | 2017-05-31 | 河南省科学院应用物理研究所有限公司 | A kind of interconnecting method of micro-system three-dimension packaging |
| EP3754706A1 (en) | 2019-06-20 | 2020-12-23 | IMEC vzw | A method for the electrical bonding of semiconductor components |
| CN113809111A (en) * | 2020-06-16 | 2021-12-17 | 华为机器有限公司 | Display panel, display device and preparation method of display panel |
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| JP3706533B2 (en) * | 2000-09-20 | 2005-10-12 | 三洋電機株式会社 | Semiconductor device and semiconductor module |
| JP2005019589A (en) * | 2003-06-25 | 2005-01-20 | Canon Inc | Resin bonding structure of circuit board |
| TW201039383A (en) * | 2009-04-17 | 2010-11-01 | Arima Optoelectronics Corp | Semiconductor chip electrode structure and manufacturing method thereof |
| JP4880055B2 (en) * | 2010-06-04 | 2012-02-22 | 株式会社新川 | Electronic component mounting apparatus and method |
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