Background technology
Development along with semiconductor fabrication, the chip size trend is microminiaturized, chip density on the circuit board substrate increases day by day, traditional encapsulation technology is just becoming the bottleneck that the restriction circuit performance improves, and impelling the encapsulation technology of chip is present flip-chip (Flip chip) technology by original cutting line ball technical development.Flip chip technology (fct) is after chip manufacturing is finished, and goes up at the lead-in wire welding block (Bond Pad) of chip and forms solder projection (Solder Bump), will directly will have the chip attach of solder projection after the chip cutting in printed circuit board (PCB) (PCB) or other substrate.This needs the solder projection on the chip to have excellent mechanical intensity and electric conductivity.Number of patent application is the manufacture method that 200310104780.6 Chinese patent discloses a kind of solder projection.Fig. 1 to Fig. 5 is the generalized section of each step corresponding construction of the manufacture method of the disclosed solder projection of described patent document.
As shown in Figure 1, be formed with lead-in wire welding block 102 in semiconductor substrate 100, be formed with protective layer 104 on the described semiconductor-based end 100, the surface of described lead-in wire welding block 102 is exposed.
As shown in Figure 2, at the surface deposition metal level 106 of described protective layer 104 and lead-in wire welding block 102, described metal level is 106 to be a kind of or combination in the titanium, tungsten, chromium, titanizing tungsten, copper, nickel.
As shown in Figure 3, spin coating photoresist layer 107 on described metal level 106, and form patterns of openings 105 by exposure imaging, described patterns of openings 105 be positioned at described electrode pad directly over, form copper layer 108 on the metal level 106 in described patterns of openings 105.
As shown in Figure 4, on described copper layer 108, electroplate solder projection 109.Described solder projection comprises tin and silver, and is main component with tin.
As shown in Figure 5, remove described photoresist layer 107, with described solder projection 109 is mask, be etched away the metal level 106 that is not covered by described solder projection 109, form spherical solder projection 110 by refluxing, the temperature of backflow is 230 to 270 degree, simultaneously, copper diffuses in reflux course in the described solder projection 110, becomes the part of solder projection.The solder projection that said method forms is the alloy of tin-silver-copper, method by diffusion is mixed copper in solder projection, tin and silver are formed among the solder projection by electric plating method, the average current density of electric current is generally 4 to 6ASD during plating, electroplating velocity is very fast, form the skewness of silver in the solder projection, form the cavity easily, when being subjected to the outside to shearing force, solder projection easily therefrom between the fracture, thereby the solder projection that causes forming can not bear bigger external force when being welded in circuit board or other substrate and rupture, and causes the welding failure.
Summary of the invention
Therefore, the object of the present invention is to provide a kind of manufacture method of solder projection, with the problem pockety of each component in the solder projection that solves the manufacture method formation that has solder projection now.
For achieving the above object, the manufacture method of a kind of solder projection provided by the invention comprises: provide one have the lead-in wire welding block the semiconductor-based end; On described lead-in wire welding block, form a metal level at least; Form photoresist layer on described metal level, and graphically form opening, described opening is positioned at relevant position, described lead-in wire welding block top, and described open bottom is exposed described metal level; Form solder projection with galvanoplastic in described opening, the average current density of electric current is 3 to 4ASD in the described galvanoplastic; The metal level of removing described photoresist layer and not covered by described solder projection; Described solder projection is refluxed.
Described solder projection is a sn-ag alloy.
The step that described plating forms sn-ag alloy is as follows: described metal level is connected to the negative pole of DC power supply, and makes the electric current of first current value flow through described metal level, fill up described opening until described solder projection; At least make an electric current greater than second current value of first current value flow through described metal level, the duration is 3 to 10 minutes.
Described first current value is 0.45 to 0.65A.
Described reflow process step is as follows: under inert gas environment, described solder projection is heated to first temperature, and 30 to 60 minutes duration; Described solder projection is heated above second temperature of first temperature and 30 to 60 minutes duration; Described solder projection is heated above the 3rd temperature of second temperature and 30 to 60 minutes duration; Described solder projection is cooled to the 4th temperature less than first temperature and 10 to 50 minutes duration.
Described metal level is a kind of or combination in titanium, tungsten, chromium, titanizing tungsten, copper, the nickel.
Described first current value is 0.45 to 0.65A.
The present invention also provides a kind of manufacture method of solder projection, comprising: the semiconductor-based end of a metal level is provided, is formed with photoresist layer on described metal level, be formed with the opening that described metal level is exposed in the bottom in described photoresist layer; Described metal level is connected to the negative electrode of DC power supply, make the electric current of first current value flow through described metal level, electroplate to carry out the first step, fill up described opening, and to make the average current density of the electric current of the metal level that flows through described open bottom be 3 to 4ASD until described solder projection; At least make an electric current greater than second current value of first current value flow through described metal level, and to make the average current density of the electric current of the metal level that flows through described open bottom be 3 to 4ASD; Remove described photoresist layer; Remove the metal level that is not covered by described solder projection; Described solder projection is refluxed.
The scolder of described filling is tin and silver.
The content of silver is 1.8 to 2.8% in the described scolder.
Compared with prior art, the present invention has the following advantages:
The present invention forms in the method for solder projection on the one hand the average current density of electric current when reducing to electroplate, and improves the content of silver in electroplating, and the hardness of silver is relatively large, and the content that improves silver can improve the hardness of the solder projection of formation; In addition, because little current density makes that the speed of electroplating is relatively slow, make silver in tin is the solder projection of main component, evenly distribute; On the other hand, the present invention electroplates by the multistep of different current values, make the average current density of plating in each step be 3 to 4ASD, thereby make that the electroplating velocity of whole electroplating process is constant, each uniform component distribution in the solder projection that helps forming, and can not form the cavity, guarantee that the solder projection that forms has bigger intensity, can bear the shearing force of bigger outside.
Method of the present invention forms spherical solder projection by reflux technique.By progressively heating up, make whole solder projection temperature evenly rise to fusing point, depend on the surface tension of liquid solder projection, refluxing forms spherical solder projection.By the method that progressively heats up, make whole solder projection internal temperature and stress distribution uniformity, the solder projection smooth surface that forms does not have burr, easier this solder projection is soldered to circuit board surface and other substrate surface, and adhesive property is better.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the specific embodiment of the present invention is described in detail below in conjunction with accompanying drawing.
Fig. 6 is the flow chart of first embodiment of the manufacture method of solder projection of the present invention.
As shown in Figure 6; at first; semiconductor substrate (S100) is provided; the described semiconductor-based end is a kind of in monocrystalline silicon, polysilicon, the amorphous silicon; the metal interconnected of the device manufacturing of leading portion and back segment finished at the described semiconductor-based end, is formed with the lead-in wire welding block at described semiconductor-based basal surface, and described lead-in wire welding block is aluminium, copper or aluminium copper; semiconductor-based basal surface beyond described lead-in wire welding block is formed with protective layer, and described protective layer is an organic polymer.
For strengthening the solder projection that forms in the subsequent technique and the adhesive property of described lead-in wire welding block, on described lead-in wire welding block and protective layer, form a metal level (S110) at least.Described metal level is a kind of in titanium, tungsten, chromium, titanizing tungsten, copper, nickel, gold, the chromium or combination, and its formation method is any in physical vapour deposition (PVD), chemical vapour deposition (CVD), plasma enhanced chemical vapor deposition, ald, the plating.This metal level also as the electrode cathode in the follow-up plating formation solder projection technology, is connected with dc power cathode.
Spin coating photoresist on described metal level, and by exposure imaging formation opening, described opening is positioned at relevant position, described lead-in wire welding block top, and described open bottom is exposed described metal level (S120).The size of described opening is greater than the size of its below corresponding lead-in wire welding block.
In described opening, fill scolder with galvanoplastic, form solder projection, and to make the average current density of the electric current of the metal level by described open bottom be 3 to 4ASD (S130).Described scolder is tin and silver, and the content of silver is 1.8 to 2.8% in the solder projection of formation.The steps include: described metal level is connected to the negative electrode of DC power supply, and make the electric current of first current value flow through described metal level, fill up described opening until described solder projection; At least make an electric current greater than second current value of first current value flow through described metal level, the duration is 3 to 10 minutes.First current value described in the present embodiment is 0.45 to 0.65A.In this step when reducing to electroplate the average current density of electric current, improve the content of silver in the solder projection that forms, the hardness of silver is relatively large, the content that improves silver can improve the hardness of the solder projection of formation; In addition, because little current density makes that the speed of electroplating is relatively slow, make silver in tin is the solder projection of main component, evenly distribute; , also by carrying out the multistep electroplating technology, silver is evenly distributed in the feasible solder projection that forms, and can not form the cavity, has improved the intensity of the solder projection that forms, and makes the solder projection that forms can bear bigger external shearing force in the present embodiment.
Removing described photoresist layer by oxygen gas plasma ashing and wet-cleaned, is mask layer with described solder projection then, removes the metal level (S140) that is not covered by described solder projection by dry method or wet etching.
Described scolder is carried out reflux technique, so that described solder projection becomes sphere (S150).Its step is as follows: under inert gas environment, described scolder is heated to first temperature, and 30 to 60 minutes duration; Described scolder is heated above second temperature of first temperature and 30 to 60 minutes duration; Described scolder is heated above the 3rd temperature of second temperature and 30 to 60 minutes duration; Described scolder is cooled to the 4th temperature less than first temperature and 10 to 50 minutes duration.In the present embodiment, described first temperature is 120 to 180 degree, and second temperature is 220 to 240 degree, and the 3rd temperature is 240 to 280 degree, and the 4th temperature is 30 to 80 degree.The reflux technique of lowering the temperature then by persistently overheating fusing point to described scolder gradually in this method, the solder projection smooth surface of the feasible sphere that forms, do not have burr, easier this solder projection is soldered to circuit board surface and other substrate surface, and adhesive property is better.
Be described in detail below in conjunction with the manufacture method of profile solder projection of the present invention.Fig. 7 to Figure 14 is the generalized section of each step corresponding structure of manufacture method first embodiment of solder projection of the present invention.
Step 1, as shown in Figure 7, semiconductor substrate 200 is provided, the described semiconductor-based end 200 is a kind of in monocrystalline silicon, polysilicon, the amorphous silicon, the metal interconnected of the device manufacturing of leading portion and back segment finished at the described semiconductor-based end 200, be formed with lead-in wire welding block 202 on surface, the described semiconductor-based ends 200, described lead-in wire welding block 202 is aluminium, copper or aluminium copper, and described lead-in wire welding block 202 is communicated with the metal interconnecting wires of back segment.Surface, the semiconductor-based ends 200 beyond described lead-in wire welding block 202 is formed with protective layer 204, and described protective layer 204 is an organic polymer, and this protective layer 204 is used for protecting the device at this semiconductor-based end not to be subjected to external damage.
Step 2 as shown in Figure 8, forms metal level 206 on described lead-in wire welding block and protective layer, described metal level 206 is one or more layers, and its material is a kind of or combination in titanium, tungsten, chromium, titanizing tungsten, copper, nickel, gold, the chromium.The formation method of described metal level 206 is any in physical vapour deposition (PVD), chemical vapour deposition (CVD), plasma enhanced chemical vapor deposition, ald, the plating.Described metal level 206 is used for strengthening the solder projection that subsequent technique forms and the adhesive property of described lead-in wire welding block, and forms electrode cathode in the solder projection technology as follow-up plating, is connected with dc power cathode.
Step 3, as shown in Figure 9, spin coating photoresist layer 207 on described metal level 206, and by exposure imaging formation opening 205, described opening 205 is positioned at relevant position, described lead-in wire welding block 202 top, and the surface of exposing described metal level 206, described opening 205 bottoms.The size of described opening 205 is greater than the size of its below corresponding lead-in wire welding block 202.
Step 4, carry out first step electroplating technology: electroplating bath is put at the described semiconductor-based end 200 that is formed with opening 205, described electroplating bath fills the electroplate liquid of the ion that comprises the electroplated metal, make described metal level 206 be connected to the negative pole of DC power supply, and the positive pole that makes described DC power supply links the anode of electroplating bath, at described metal level 206, electroplate liquid, pass through the electric current of first current value in the loop that anode is formed, and make that the average current density of electric current of the metal level 206 flow through described opening 205 bottoms is 3 to 4ASD, form solder projection 209 as shown in figure 10 on the metal level 206 of described opening 205 bottoms, described solder projection 209 fills up described opening 205 at least.The metal of electroplated described in the present embodiment is tin and silver, described first current value is 0.45 to 0.65A, the content of silver is 1.8% to 2.8% in the solder projection that forms, and the duration of described first step electroplating technology is 10 to 40 minutes, the solder projection 209 of formation fill up described opening 205.
Then carry out the second step electroplating technology: change the electric current flow through described metal level 206, electroplate liquid, anode loop, make the electric current of second current value flow through this loop, described second current value is 0.55 to 0.65A, and to keep the average density of electroplating be 3 to 4ASD.The duration of the described second step electroplating technology is 3 to 4 minutes,
Then, carry out the 3rd step electroplating technology: changing the electric current that flows through described metal level 206, electroplate liquid, anode loop is the 3rd current value, described the 3rd current value is 0.7 to 0.8A, and average current density is 3 to 4ASD, and described the 3rd electroplating technology duration in step is 3 to 5 minutes.
Follow, carry out the 4th step electroplating technology: changing the electric current flow through described metal level 206, electroplate liquid, anode loop is the 4th current value again, and described the 4th current value is 0.85 to 0.95A, and average current density is 3 to 4ASD, and the duration is 3 to 5 minutes.
Carry out the 5th step electroplating technology: changing the electric current flow through described metal level 206, electroplate liquid, anode loop is the 5th current value, and described the 5th current value is 1 to 1.1A, and average current density is 3 to 4ASD, and the duration is 3 to 5 minutes.
At last, carry out the 6th step electroplating technology: changing the electric current flow through described metal level 206, electroplate liquid, anode loop is the 6th current value, and described the 6th current value is 1.25 to 1.35A, and average current density is 3 to 4ASD, and the duration is 3 to 5 minutes.Through the plating in step of above-mentioned number, form solder projection 209a as shown in figure 11.
The average current density when reducing to electroplate on the one hand in this step, thus improve electroplate in the content of silver because the hardness of silver is relatively large, the content that improves silver can improve the hardness of the solder projection of formation; In addition, because little current density makes that the speed of electroplating is relatively slow, this helps to make the silver electroplated evenly to distribute in tin is the solder projection 209a of main component; The present invention is by the also multistep plating of different current values, make the average current density of plating in each step be 3 to 4ASD, thereby make that the electroplating velocity of whole electroplating process is constant, each component evenly distributes among the solder projection 209a that helps forming, and can not form the cavity, guaranteed that the solder projection that forms has bigger intensity, can bear the shearing force of bigger outside.
Step 5; as shown in figure 12; remove described photoresist layer 207 by oxygen gas plasma ashing and wet-cleaned; then as shown in figure 13; with described solder projection 209a is mask layer; remove the metal level 206 that is not covered by described solder projection 209a, the method for removal is dry plasma or wet etching, and described protective layer 204 surfaces are exposed.
Step 6 is carried out reflux technique to described solder projection 209a, forms the solder projection 209b of sphere as shown in figure 14.Reflow process step is as follows described in the present embodiment: under inert gas environment, described solder projection is heated to 120 to 140 degree, and 30 to 60 minutes duration; Described solder projection is heated to 160 to 180 degree, and under this temperature, continues 40 to 60 minutes; Described solder projection is heated to 180 to 190 degree, and under this temperature, continues 40 to 60 minutes; Described solder projection is heated to 220 to 240 degree, and under this temperature, continues 40 to 60 minutes; Described solder projection is heated to 240 to 280 degree, and under this temperature, continues 40 to 60 minutes; Described solder projection is cooled to 30 to 80 degree, and under this temperature, continues 10 to 50 minutes, then be cooled to room temperature.Step through the described a series of heat temperature raising of present embodiment makes whole solder projection temperature evenly rise to fusing point, depends on the surface tension of liquid solder projection, refluxes to form spherical solder projection.By the method that progressively heats up, make whole solder projection internal temperature and stress distribution uniformity, whole solder projection can evenly melt, the solder projection smooth surface that refluxes, there is not burr, easier this solder projection is soldered to circuit board surface and other substrate surface, and adhesive property is better.
Figure 15 is the flow chart of second embodiment of solder projection manufacture method of the present invention.
As shown in figure 15; at first; the semiconductor substrate is provided; on the described semiconductor-based end, be formed with several lead-in wire welding blocks; be formed with protective layer between the described lead-in wire welding block; on described lead-in wire welding block and protective layer, be formed with metal level, on described metal level, be formed with photoresist layer, in described photoresist layer, be formed with the opening (S200) that described layer on surface of metal is exposed in the bottom.
Then, described metal level is connected to the negative electrode of DC power supply, and make first current value flow through described metal level, electroplate to carry out the first step, fill up described opening until described solder projection, form solder projection on the metal level in described opening, and to make the average current density of the electric current in the metal level that flows through described open bottom be 3 to 4ASD.The tin of solder projection described in the present embodiment, silver alloy, wherein Yin content is 1.8 to 2.8% (S210).
At least make an electric current greater than second current value of first current value flow through described metal level, and to make the average current density of the electric current of the metal level that flows through described open bottom be 3 to 4ASD (S220);
Remove described photoresist layer (S230) by oxygen gas plasma.
Remove the metal level (S240) that is not covered by dry etching or wet etching by described solder projection;
Described solder projection is carried out reflow step, form spherical solder projection (S250).
Though the present invention with preferred embodiment openly as above; but it is not to be used for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; can make possible change and modification, so protection scope of the present invention should be as the criterion with the scope that claim of the present invention was defined.