Patent Application
20060076967
(1) Field of the Invention
The present invention relates to a membrane with bumps for testing a fine electrical circuit formed on a semiconductor wafer, a liquid crystal display panel, a solar battery, or the like by causing the bumps to have surface contact with contacting parts of the fine electrical circuit so as to have plural electrical contacts simultaneously, as well as relating to a method of manufacturing a probe card including such membrane with bumps, and the like.
(2) Description of the Related Art
In recent years, there has been an active effort underway to achieve higher accuracy and higher speed as well as larger semiconductor devices in order to provide more sophisticated semiconductor devices or the like and to reduce their costs. For example, there has been an ongoing effort to achieve a finer patterning of electrical circuits formed on a semiconductor wafer as well as a larger wafer of a semiconductor wafer. Therefore, for a test of the operation of an electrical circuit, pitch intervals between contacting parts are required to be smaller and thus the number of electrical contacts to be provided simultaneously is required to be larger.
The following describes a conventional method of manufacturing a probe card (for example, refer to Japanese Laid-Open Patent application No. 08-235935).
Referring to
However, since such rivet-shaped convex electrode 1104 is formed by a metal plating method, it is difficult to control its shape. It is extremely difficult to control the size of the diameters of the swollen portions 1103 since their diameters are greatly affected by a various factors such as the accuracy of forming a hole on the polyimide film 1101, the shape and surface roughness of such hole, as well as chamfered shape.
The result of the evaluation conducted by the inventor of the present invention (hereinafter simply referred to as “the present inventor”) shows that, when 1000 rivet-shaped convex electrodes 1104 whose swollen portions are 100 μm in diameter were formed, the diameters of the resulting swollen portions were in the range φ100±10 μm, and thus that it was difficult to have equal and normal electrical contacts by all the electrodes. In the case where the number of convex electrodes is increased, it is possible that there will be increased variations in the shape of their swollen portions.
Meanwhile, in the case where a rivet-shaped convex electrode 1104 is formed by a plating method, its swollen portion does not have a beautiful semispherical shape but a squashed shape as shown in
A probe card is used to have plural electrical contacts simultaneously by causing convex electrodes 1104 and contacting parts of an electrical circuit to have surface contact. Thus, in the case where the diameters of the convex electrodes 1104 are not uniform and do not have a beautiful semispherical shape, the following problems occur: the size of contacting parts to come in contact with such convex electrodes 1104 are required to be big more than necessary, which results in a defect in the case of a fine electrical circuit; and a predetermined electrical contact cannot be assured unless a greater pressing force is applied.
Furthermore, since it is difficult to control the swollen portions 1103, which are grown by means of natural plating growth, there is also a serious problem that many defects occur and thus the costs for probe cards increase due to lowered yields.
The following describes a method of manufacturing a probe card according to a second conventional technology (for example, refer to Patent Document 2).
The method disclosed in this Patent Document 2 is a solution to the problems of the technology disclosed in Patent Document 1. Referring to
However, since this method uses the anisotropic conductive film 1302, which is relatively expensive, there is a problem of an increased cost and a shortened useful lifetime due to deterioration of the anisotropic conductive film 1302. More specifically, the anisotropic conductive film 1302 is made of elastic film in which conductive particles are arranged, and by being pressed to a certain degree, conductive particles in such pressed portion adhere to one another to allow electricity to flow. However, in the case where an operation test of the electrical circuit 1301 is conducted under the temperatures in the range between 20° C. and 100° C. or higher, the elastic film expands and contracts greatly in the plane direction of the film due to thermal expansion. Furthermore, the above test is conducted, in general, for plural times by exchanging test subjects, and the elastic film is pressed with a certain degree of force every time a test is conducted, as is disclosed in Patent Document 2. Under these circumstances, the electrical resistance values of the conductive particles included in the anisotropic conductive film 1302 vary with time since the shape of the elastic film constantly changes by being pressed, although such electrical resistance values are stable when the conductive particles are in the original arrangement. In other words, since the original arrangement of the conductive particles changes due to distortion caused by thermal expansion and contract and distortion caused by repeatedly applied load, their electric resistance values become unstable.
The result of the evaluation conducted by the present inventor shows that, the electric resistance values of the contacting parts of the anisotropic conductive film 1302 tend to be greater after the operation test of the electrical circuit 1301 is conducted several hundred times, and thus that stable test results cannot be achieved.
The present invention has been conceived in view of the above problems of the conventional technologies, and it is an object of the present invention to provide a membrane with bumps that is capable of providing electrical contacts with high accuracy and allowing electrical circuit tests to be stably conducted even when such membrane is used repeatedly, in tests of electrical circuits formed on a semiconductor wafer, a liquid crystal display panel, a solar battery, or the like, even in the case where electrodes on such electrical circuits have narrower pitch intervals therebetween and thus there are an increased number of electrodes.
In order to solve the above problems, the membrane with bumps according to the present invention includes: a plurality of bumps, each of which is made up of a probe and an electrode, the probe having a diameter which becomes smaller from one end toward the other end of the probe, and the electrode having a diameter which is larger than the diameter of the one end of the probe; and an insulating base where the bumps are positioned at predetermined locations so that the bumps are insulated from each other, wherein the probe is positioned, penetrating the insulating base in a thickness direction, and a metal film is placed in between the electrode and the insulating base.
Since the diameter of each bump of this membrane with bumps is smaller from one end toward the other end of the probe, even in the case where the pitch intervals between parts to be contacted, e.g., electrodes of an electrical circuit, are small, it is possible to receive signals from the respective electrodes by causing the bumps to come in contact with the respective electrodes in an accurate manner.
Furthermore, since the electrodes equipped to the respective bumps are bonded to the insulating base by the metal film that supports such bumps, their bonding strength is increased, and thus it becomes difficult for bumps to fall from the insulating base.
Furthermore, it is preferable that in the membrane with bumps according to the present invention, a part of each of the bumps is an isotropic elastic conductor.
Accordingly, even in the case where (a) there are slight variations in the height of parts to be contacted, e.g., electrodes, (b) there are common differences in the shape of bumps themselves, and (c) there are differences in the degree of frictional wear of bumps as a result of a repeated use of the membrane with bumps, it is possible to assure highly accurate, stable electrical contacts by absorbing such variations and differences.
Moreover, in order to solve the above problem, the method of manufacturing a membrane with bumps according to the present invention includes: preparing a lamellar body in which a metal film layer, an insulating body layer, a mold base layer, and a stop layer are laminated in order of mention; forming micro holes in the lamellar body, each of the micro holes having a diameter which is smaller from the metal film layer toward the mold base layer; forming a resin pattern layer on a surface of the metal film layer that does not face the insulating base layer, the resin pattern layer having apertures, each of which is continuous with the micro hole and whose diameter is larger than the diameter, of the micro hole, at the surface of the metal film layer that does not face the insulating base layer; forming bumps, each of which has a probe and an electrode, by filling the micro holes and the apertures with a conductive material, the probe having a diameter which becomes smaller from one end toward the other end of the probe, and the electrode having a diameter which is larger than the diameter of the one end of the probe; removing a part of the metal film layer so that the bumps become insulated from each other; removing the mold base layer from the insulating base layer; and removing the resin pattern layer.
Accordingly, it is possible to form a large number of bumps having uniform shape and thus to provide a membrane with bumps whose shape is stable. In particular, since the present method produces bumps with uniform height, it is possible to have stable electrical contacts at all contacting parts.
Furthermore, the same effect is produced by a probe card made up of a wiring circuit board having wiring patterns corresponding to plural semiconductor devices formed on a wafer and of the above-described membrane with bumps.
Furthermore, a significant solution to the above-described problems is achieved in the case where a test of semiconductor devices is conducted, using the above probe card, by causing the bumps to come in contact with the electrodes of the respective semiconductor devices.
It should be noted that in the present specification and claims, the term “diameter” refers to not only the diameter of a circle, but also the diameter of a circle whose area size is the same as the size of a non-circular area.
It should be also noted that in the present specification and claims, the metal is not limited to one kind of metal, but it also refers to an alloy including plural kinds of metallic elements or elements other than metal.
The membrane with bumps according to the present invention is capable of providing electrical contacts with high accuracy and allowing electrical circuit tests to be stably conducted even when such membrane is used repeatedly, in tests of electrical circuits formed on a semiconductor wafer, a liquid crystal display panel, a solar battery, or the like, even in the case where electrodes on such electrical circuits have narrower pitch intervals therebetween and thus there are an increased number of electrodes.
The disclosure of Japanese Patent Application No. 2004-296948 filed on Oct. 8, 2004 including specification, drawings and claims is incorporated herein by reference in its entirety.
These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings that illustrate a specific embodiment of the invention. In the Drawings:
Referring to the drawings, a description is given of a membrane with bumps and a method of manufacturing the same, each of the bumps serving as an electrical contact terminal of a probe card that is used to test the operation of an electrical circuit formed on an eight-inch wafer.
The bumps 32, which are positioned at predetermined locations, are kept insulated from each other by the insulating base 12 serving as an insulating base layer. The convex conductive part 31 which forms a part of each bump 32 penetrates the insulating base 12 in the thickness direction, so that the tip of the convex conductive part 31 protrudes from the insulating base 12. Each bump 32 is firmly bonded to the insulating base 12 by at least the square electrode 30 and the insulating base 12 being bonded by the metal film 11.
First, a laminated sheet 10 is prepared as a lamellar body (S101).
Referring to
Used as the resist making up the mold base 13 is a resist that cures with ultraviolet and heat, and that tacks well with the insulating base 12 and the stop layer 14 positioned above and below the mold base 13.
The polyimide resin making up the insulating base 12 and the mold base 13 are formed as layers by means of lamination, but they are laminated by applying the least possible tension. This lamination method makes it possible to minimize a positional deviation of each bump 32 to 5 μm or less when the mold base 13 is separated. This applies to the lamination of the mold base 13 and the stop layer 14.
Meanwhile, the metal film 11 is formed on one surface of the insulating base 12 by means of spattering which is one of the physical vapor deposition methods. Spattering is suitable as a method of forming the metal film 11 on the insulating base 12 with a high adhesion.
Next, referring to
The resin pattern layer 20 is formed in the following manner: a patterning resist with the thickness of 20 μm is applied over the outer surface of the metal film 11; and approximately 20 thousands apertures 21, having a 80 μm by 220 μm square form, are formed by means of exposure at positions to come in contact with an electrical circuit formed on the eighth-inch wafer.
Note that the number of apertures 21 differs depending on the type of devices formed on the wafer, since the number of apertures 21 corresponds to the number of bumps 32 to come in contact with an electrical circuit formed on the wafer. The result of the evaluation conducted by the present inventor shows that, in the present embodiment, apertures 21 can be formed at the maximum of some 40 thousands positions and thus the same number of bumps 32 can be formed.
Next, referring to
As supplemental remarks, a description is given of the performance of a current-technology laser beam apparatus. The sizes of holes formed in hole formation are mainly greater than φ50 μm. Thus, the laser stage of the current-technology laser beam apparatus is specified to have the positional accuracy that corresponds to the diameter of the holes, i.e., ±10 μm or greater. Regarding the number of holes to be formed, since it is not usual to form as many as 5000 or more holes in an eight-inch level area, it is more than the requirements defined in the laser stage specification to have to satisfy the positional accuracy of each of all 20 thousand holes that are required to be formed according to the present embodiment.
The laser alignment method to be used in the present embodiment is a preferable method since it utilizes the laser stage of the current-technology laser beam apparatus, while solving the problems thereof. While the shape and position of each aperture 21, which serves as an alignment mark, are of course required to be highly accurate, there is no problem, with the current technology of exposure and resist material, in assuring the accuracy in submicron units in terms of both cost and technology. However, in the case where a square-shaped aperture 21 serving as an alignment mark has an area larger than 0.04 mm2, it is not possible to obtain effective results since such area is not in the recognition range of a CCD camera that can only recognize the positional accuracy of ±5 μm or lower. Thus, a cross-sectional area of each aperture 21 serving as an alignment mark is preferably 0.04 mm2 or smaller in the plane direction.
Next, a description is given of hole formation by means of laser beam irradiation. While a certain amount of power is required to penetrate the metal film 11, the output power of a laser beam to be irradiated should be low so as to stop the hole formation at the surface of the stop layer 14 after penetrating the insulating base 12 made of a polyimide resin and the mold base 13 made of a resist. The present inventor has achieved the penetration of the metal film 11 by irradiating the YAG third harmonic with the wavelength of 355 nm for 0.02 seconds at the output power of 200 mw. Note that the irradiation time is calculated by the following equation, where 0.01 indicates the time required to penetrate the unit length by the irradiation of a laser beam under the above conditions, and 2 indicates the thickness of the metal film 11:
Irradiation time=0.01 (second/μm)×2 (μm)=0.02 seconds.
Here, the wavelength of 355 nm is used so that the diameter of each micro hole 19 formed by the hole formation is 50 μm or smaller. This is because the shorter the wavelength is, the smaller the diameter of a light collecting spot becomes, but the same result is achieved by using the YAG second harmonic with the wavelength of 532 nm in the case where the diameter of each micro hole 19 formed by the hole formation is wished to be 50 μm or smaller. However, the use of a wavelength greater than 550 nm is not preferable since it becomes extremely difficult to have a small hole diameter.
Regarding the output power, when the value is less than 80 mW, defects can be caused such as variations in the diameter of holes in the metal film 11. Meanwhile, when the value is greater than 500 mW, there is a possibility that the laser beam penetrates or even scrapes off the stop layer 14 regardless of irradiation time. Thus, the output power of the laser beam that can penetrate the metal film 11 with the thickness of 2 μm is preferably in the range between 80 mW and 500 mW inclusive.
In the case where the metal film 11 is thinner than 1 μm, the output power of the laser beam should be further limited. The present inventor has confirmed that the YAG second harmonic with the wavelength of 532 nm reaches and partially resolves the stop layer 14. Thus, by irradiating the YAG third harmonic with the wavelength of 355 nm at the output power of 80 nW, the same result was achieved as that for the case where the thickness of the metal film 11 is 1 μm or greater. In the case where the thickness of the metal film 11 is less than 1 μm, the output power of a laser beam used for the hole formation is preferably in the range between 60 mW and 100 mW inclusive since (i) in the case where the output power is less than 60 mW, the metal film 11 cannot be penetrated in a round shape in a stable manner and (ii) in the case where the output power is greater than 100 mW, there occurs oxidation around holes due to the thinness of the metal film 11 and the subsequent processes are adversely influenced by such oxidation.
As a condition for penetrating the insulating base 12 made of a polyimide resin and the mold base 13 made of a resist and then stopping the hole formation at the surface of the stop layer 14, the YAG third harmonic with the wavelength of 355 nm, as in the case of the condition for penetrating the metal film 11, and the output power of 30 mW are set. Furthermore, as the diameter of a hole, i.e., the diameter of a collected laser beam, φ15 μm±2 μm is set. The reason for selecting such wavelength is as described above. Regarding the output power of a laser beam, at the output power less than 10 mW, laser beams cannot be outputted in a stable manner or cannot form holes in a stable manner even in the resist making up the mold base 13 that is relatively easy to scrape off at a lower power. Meanwhile, the output power greater than 50 mW is not preferable since there occurs the removal or dissolve of the outer surface of the stop layer 14. Thus, the output power of a laser beam is preferably in the range between 10 mW and 50 mW inclusive.
The conditions for laser beam irradiation are summarized below.
(1) A preferable condition for penetrating the metal film 11 with the thickness in the range between 1 μm and 5 μm inclusive is: the wavelength of a laser beam to be irradiated is 550 nm or less; the output power of the laser beam is in the range between 80 mW and 500 mW inclusive; and the irradiation time is
Irradiation time=0.01 (second/μm)×the thickness of the metal film 11 (μm)±50%.
(2) A preferable condition for penetrating the metal film 11 with the thickness in the range between 0.1 μm and 1 μm inclusive is: the wavelength of a laser beam to be irradiated is 400 nm or less; the output power of the laser beam is in the range between 60 mW and 100 mW inclusive; and the irradiation time is
Irradiation time=0.05 (second/μm)×the thickness of the metal film 11 (μm)±50%.
(3) A preferable condition for penetrating the insulating base 12 and the mold base 13 whose total thickness is in the range between 1 μm and 500 μm inclusive without penetrating the stop layer, so that the outer surface of such stop layer serves as the undersurface of micro holes 19, is: the wavelength of a laser beam to be irradiated is 400 nm or less; and the output power of a laser beam is in the range between 10 mW and 50 mW inclusive.
Note that the thickness of the stop layer 14 is preferably 1 μm or greater for the reason that the stop layer 14 needs to have the thickness that can provide the resistance to the irradiation of laser beams.
It has been proved that, when the hole formation is carried out, in the case where the hole formation should be stopped at the surface of the stop layer 14, by use of the YAG fourth harmonic with the wavelength of 266 nm at the output power in the range between 10 mW and 50 mW inclusive, the outer surface of the stop layer 14 serving as the undersurface of the holes has the center line average roughness of 1 to 3 μm, and thus that such surface roughness is transferred to the bumps 32, resulting in a highly favorable effect in the conductivity between each bump 32 and an electrical circuit formed on the wafer when they are in contact with each other.
The contacting part of an electrical circuit on the wafer is made of a conductive film, typically aluminum or the like. However, since a natural oxide film is attached on the outer surface of such contacting part, effective electrical continuity cannot be assured unless such natural oxide film is removed or physically broken through at the time of contact. However, according to the present embodiment, the use of the bumps 32 to which the surface roughness of the stop layer 14 has been transferred makes it possible to physically break through the above oxide film with ease and thus to assure favorable electrical continuity. This structure leads to a significant reduction in cost since there is no need to newly add a process of removing the oxide film of each electrical circuit on the wafer or no need to transport the wafer in a nitride atmosphere to prevent the formation of natural oxide films.
In the case where the surface roughness of the stop layer 14 serving as the undersurface of the holes is less than 1 μm, it becomes hard to break through the above oxide film. Meanwhile, the surface roughness greater than 3 μm makes it difficult to assure favorable electrical continuity since an area to be in contact with an electrical circuit becomes small. Thus, the surface roughness is preferably in the range between 1 μm and 3 μm inclusive.
It should be noted that the same surface roughness as the one described above can be achieved in the case where the hole formation is carried out by irradiating a krF excimer laser with the wavelength of 248 nm at the output power in the range between 10 mW and 50 mW inclusive.
Next, cleaning is performed to remove a smear (S104).
Next, referring to
Next, referring to
Next, referring to
Next, referring to
Through this process, the outer edges of each square electrode 30 and each remaining metal film 11 become approximately flat. Note that the etching process is controlled so that a common difference in the size of the outer edge of each metal film 11 is ±10 μm relative to the size of the outer edge of the corresponding square electrode 30. Such control is necessary since (i) the bonding strength between the insulating base 12 and each bump 32 becomes low in the case where the outer edge of each metal film 11 comes 10 μm inside the outer edge of the corresponding square electrode 30, and (ii) there is a high possibility that a short circuit occurs between adjacent square electrodes 30 in the case where the outer edge of each metal film 11 protrudes the outer edge of the corresponding square electrode 30 by 10 μm.
Note that especially in the case where pitch intervals between square electrodes 30 is small (around 100 μm), it is preferable that the etching process is strictly controlled so that a common difference in the size of the outer edge of each metal film 11 is ±5 μm relative to the size of the outer edge of the corresponding square electrode 30.
In the present embodiment, the metal film 11 is grown, on the outer surface of the insulating base 12 made of a polyimide resin, to the thickness of 2 μm by means of spattering. As a result, the strength of adhesion between the insulating base 12 and the metal film 11 is high, and the peel strength of 3N/cm has been achieved.
As described above, since a high adhesion strength is ensured between the metal film 11 and the insulating base 12 first, and then square electrodes 30 are formed using plating which can be highly adhesive to such metal film 11, the insulating base 12 and the square electrodes 30 are firmly bonded by the metal film 11. As a result, the bumps 32 are prevented from falling off from the insulating base 12.
Furthermore, in addition to the filling of a conductive material by a plating method, it is also possible to prevent the bumps 32 from falling off from the insulating base 12 by filling each micro hole 19 and aperture 21 with conductive silver paste by means of screen print since conductive silver paste makes it hard for each metal film 11 and each square electrode 30 to be separated from each other. This is because, since an organic film (e.g., polyimide resin) has a poor wettability to conductive silver paste, in general, a metal film having a high adhesion is applied to the organic film, and then conductive silver paste is applied over such metal film.
Next, referring to
Through the above processes, convex conductive parts 31, each serving as a probe, are formed on the opposite side on which the square electrodes 30 are formed.
The present embodiment has an advantage of being able to process the mold base 13 and the resin pattern layer 20 by the same wet etching apparatus since the same material is used for the mold base 13 and the resin pattern layer 20.
In the present embodiment, the diameter of the tip of each convex conductive part 31 is φ18 μm±2 μm for the reason that the diameter of the tip of each micro hole 19 is slightly larger at the time of the hole formation carried out by means of laser beam irradiation, after smear cleaning or the like is performed.
Note that the amount of enlargement in the diameter of each micro hole 19 due to smear cleaning or the like is stable, and thus it is possible to control the diameter size of the tip of each convex conductive part 31 so that it has a desirable diameter size by previously setting the expected diameter size of each convex conductive part 31 at the time of hole formation.
Furthermore, the height of each convex conductive part 31 protruding from the other surface of the insulating base 12 is determined depending on the thickens of the mold base 13. In the present embodiment, it has been possible to control the height of all the convex conductive parts 31 to be within 30 μm±0.5 μm. As described above, since there are few variations in the height of the bumps 32 which exist in large number, it is possible to make a significant improvement in the performance in electrical contact between each bump 32 and each electrical circuit on the wafer.
As described above, by creating a mold using the laminated sheet 10 serving as a lamellar body and the resin pattern layer 20, and then by filling such mold with a conductive material, it becomes possible to easily control the shape as well as accuracy of each bump 32. Compared with the conventional technology that creates a rivet-shaped bump using plating by having such plating swell freely, the method of the present embodiment is easy and effective. Thus, it is possible for the present invention to make a significant improvement in the yields of the membrane with bumps 32.
Furthermore, since the resin pattern layer 20 is formed using the technology of exposure and resist material, and using such pattern both as a mold of a bump 32 and as an alignment mark, it is possible for the present invention to produce, at the same time, the contradictory effects of improving the positional accuracy of each bump 32 and reducing the manufacturing cost of bumps 32.
Referring to the drawings, a description is given of the second embodiment of the present invention.
In this drawing, the membrane with bumps is the same as the one described in the first embodiment except that the membrane with bumps of the second embodiment include isotropic elastic conductors 51 bonded above the respective square electrodes 30, wherein each of the isotropic elastic conductor 51 is electrically continuous with the corresponding bump 32.
Each of the above isotropic elastic conductors 51, which is made of isotropic conductive rubber, has the elasticity of being able to deform when applied with a force and recovering its shape when the force is released, and whose conductivity does not change even when applied with pressure.
First, a laminated sheet 10 is prepared as in the case of the first embodiment (S601).
Next, a resin pattern layer 20 is formed on the outer surface of the above laminated sheet 10 on which the metal film 11 is formed (S602). Such resin pattern layer 20 serves as a mask at the time of etching the metal film 11. On such resin pattern layer 20, resist is applied at each position where a square electrode 30 is formed, and no resist is applied to the other part.
Next, as a process of removing the metal film, the metal film 11 is etched to remove unnecessary portions (S603).
Next, using each remaining metal film 11 as an alignment mark, a micro hole 19 is formed by means of laser beam irradiation, while modifying the position of the hole formation using a CCD camera (S604). The same conditions for laser beam irradiation as the ones described above are used here. By using each remaining metal film 11 as an alignment mark, a mark and a position of hole formation are on the same plane, which enables hole formation to be performed with a higher accuracy.
After cleaning is carried out (S605), a resin pattern layer 20 is additionally formed (S606). The thickness of this resin pattern layer 20 made of patterning resist is 5 μm.
Such newly formed resin pattern layer 20 is intended for controlling the shape of each square electrode 30, and an aperture 21 is formed, on such resin pattern layer 20, at a position corresponding to each remaining metal film 11.
Next, bumps 32 are formed by filling the apertures 21 with a conductive material, as in the case of the first embodiment (S607).
Next, the resin pattern layer 20 is removed (S608), and the mold base 13 and the like are removed (S609).
Through the above processes, referring to
Next, referring to
In the present embodiment, an isotropic elastic conductor 51 provides spring-like elasticity in the height direction when a convex conductive part 31 is pressed against an electrical circuit on the wafer. It has been confirmed that, by causing an electrical contact in a state where the thickness of each isotropic elastic conductor 51 is reduced to 15 μm from 20 μm through the application of pressure, all of the bumps 32 which are positioned with a very high density of, for example, 0.32 bumps/mm2 or higher, easily have electrical continuity with an electrical circuit.
The manufacturing method employed in the second embodiment is suitable for the case where the metal film 11 and the bumps 32 are etched using the same etching agent.
The total thickness of an isotropic elastic conductor 51, a square electrode 30, and a convex conductive part 31 is about 71 μm, but it is desirable that the thickness of the isotropic elastic conductor 51 changes at least by 10% (compressed) relative to such total thickness in order to make a stable electrical contact. This is because, if a change in thickness is less than 10%, it is impossible to assure favorable electrical contacts by absorbing slight variations in the thicknesses of the bumps 32. Meanwhile, a change in the thickness greater than 50% is not preferable since such a change is too much load on a test subject, and thus may cause damage to such test subject. Furthermore, the isotropic elastic conductors 51 are also capable of absorbing slight variations in the height of contacting parts formed on the wafer being tested. The present inventor has confirmed that, in the case where variations in the height of the contacting parts is 40 μm or less, isotropic elastic conductors 51 with the thickness of 200 μm can support such variations.
Furthermore, as a method of applying an isotropic elastic conductor 51 onto a square electrode 30, an isotropic elastic conductor 51 sheet may be cut out using a mold, to be applied onto a square electrode 30.
Referring to the drawings, a description is given of the third embodiment of the present invention.
The processes from the preparation of a laminated sheet 10 (S801) up to the cleaning (S805) are the same as those described in the second embodiment, and therefore descriptions thereof are not given.
Next, a resin pattern layer 20 made of patterning resist with the thickness of 25 μm is formed on the outer surface of the laminated sheet 10 on which the metal film 11 is formed (S806). Such newly formed resin pattern layer 20 is intended for controlling the shape of each square electrode 30 as well as the shape of each isotropic elastic conductor 51 which is relatively great in height, and an aperture 21 is formed, on such resin pattern layer 20, at a position corresponding to each remaining metal film 11.
In the third embodiment, as in the case of the second embodiment, after the metal film 11 is etched, the hole formation is performed using each remaining metal film 11 as an alignment mark, and then another resin pattern layer 20 is additionally formed. This is done for the reason that, since the lastly formed resin pattern layer 20 is relatively thick, there is a possibility that the positional accuracy of the hole formation is decreased in the case where the apertures 21 formed on such thick resin pattern layer are used as alignment marks.
Next, as shown in
Next, as shown in
Note that since the isotropic elastic conductor 51 to be filled into each aperture 21 cannot function, when in a pasty state, as an isotropic elastic conductor 51 that maintains electrical continuity, while deforming and recovering its shape, elasticity is given to such isotropic elastic conductor 51 in a pasty state filled into the aperture 21 by a known vulcanization method (S809).
Finally, an unnecessary portion, i.e., the resin pattern layer 20 is removed (S810), and the mold base 13 is removed (S811). The method of removing them is the same as the one described in the second embodiment.
As described above, it is possible to bond the isotropic elastic conductors 51 to the respective bumps 32, while controlling the shape of the isotropic elastic conductors 51 which are relatively great in height.
Furthermore, since the greater the height of the isotropic elastic conductors 51, the higher the compressibility of the whole bumps, it is possible to assure effective electrical contacts, that is, electrical conductivity at the contacting parts, by absorbing the variations, if any, in the height of portions on a test subject such as an electrical circuit.
As shown in this drawing, a probe card 1000 includes the above-described membrane with bumps 1001, and a wiring circuit board 1002 for transferring electric signals obtained by the respective bumps 32.
The wiring circuit board 1002 is made of a card board 1003, having an insulating property, on the outer surface of which the following are provided as patterns: connection parts 1004 that are connected to the respective bumps; and wirings 1005 that connect such connection parts 1004 with a measuring device not illustrated in
Despite that an area of electrical continuity between each bump 32 and connection part 1004 is small, 0.04 mm2 or less, this probe card 1000 uses the isotropic elastic conductors 51, which are normal conductors, rather than using anisotropic conductive rubber used in the conventional technologies. The use of isotropic elastic conductors produces a highly favorable effect in terms of lifetime compared with the case of using anisotropic conductive rubber. This is because isotropic elastic conductors such as isotropic elastic rubber do not undergo any changes in resistance values caused by changes in the arrangement of conductive particles that occur over time.
The present inventor uses isotropic elastic conductors 51 that are obtained by adding, to silicon rubber paste, silver fillers as conductive particles. Furthermore, the present inventor focuses on the shape of the conductive particles, and uses spherical conductive particles. Compared with needle-shaped and scaly conductive fillers, spherical conductive fillers, when their shapes change, do not give much damage to the base rubber, and thus there is an advantage of being able to lengthen the lifetime of the base rubber. Furthermore, in order to respond to the increasingly infinitesimal areas of the square electrodes 30, the average diameter of spherical conductive particles is set to 20 to 30 μm, as a result of which stable resistivity is assured. This is because it has been proved that, if the diameter of spherical conductive particles is greater than 30 μm, the number of conductive particles that can be arranged in a limited area decreases, resulting in unstable resistance values, whereas if the diameter of spherical conductive particles is less than 20 μm, it is difficult for the conductive particles to be dispersed equally throughout the rubber.
It should be noted that although the above description has been given using isotropic elastic conductors, the present invention is not limited to this. Therefore, other conductors may be used as long as they are elastic conductors.
It should be also noted that although the above-described embodiments use polyimide resin as the insulating base 12, the present invention is not limited to this. Therefore, an arbitrary resin may be used as long as such resin is an insulating resin whose linear expansion coefficient is large and whose form stability is high.
Furthermore, although the above-described embodiments use square electrodes, the present invention is not limited to square as the shape of the electrodes. Therefore, the electrodes may have an arbitrary shape such as round, triangle, and the like.
Also, although the above-described embodiments use a copper thin film as an example of the metal film, the present invention is not limited to copper. Therefore, an arbitrary metal may be used as a material of the metal film.
<Evaluation of Probe Card>
Probe cards having the membranes with bumps manufactured according to the respective methods of the first to third embodiments were prepared, and electrical characteristics tests were conducted using such probe cards. In the tests, plural electrical contacts were simultaneously generated by causing each of the membranes with bumps of the first to the third embodiments to have surface contact with an electrical circuit formed on the wafer. The results of the tests show that stable electrical contacts were assured even in the case where the diameter of the contacting parts of an electrical circuit being tested is φ100 μm.
Furthermore, ten membranes with a large number of bumps 32 were prepared each for a 200 mm wafer and a 300 mm wafer, and the above electrical characteristics tests were also conducted for all of 20 membranes. The results of the tests show that favorable electric signals were obtained from all the membranes with bumps. It has been confirmed, therefore, that probe cards using the membranes with bumps according to the present invention produce highly favorable yields.
Moreover, several kinds of test subjects having different pitch intervals between adjacent contacting parts of electrical circuits were prepared, and membranes with bumps having the corresponding pitch intervals were created, so as to conduct the above electrical characteristics tests by using them. The results of the tests show that even in the case where the pitch interval between the contacting parts of an electrical circuit is 80 μm, it was possible to obtain favorable electric signals from the membrane with bumps having the same pitch interval. The diameter of the tip of each convex conductive part 31 was φ18 μm±2 μm. It has been also proved that the pitch intervals can be reduced to 30 μm by sharpening the shape of the bumps 32.
More specifically, each of the electrical characteristics tests are conducted as described below.
First, a wafer 2000, and the probe card 1000 corresponding to the wiring pattern of electrical circuits 2001 formed on such wafer 2000 are prepared according to the above-described procedures.
Next, as shown in
Next, a signal application unit 2002 applies a high-frequency signal to the electrical circuits 2001 through the probe card 1000. Note that bumps 32 included in the probe card 1000 are categorized into two types, one for signal application and the other for signal reception, depending on how they are wired in the wiring circuit board 1002.
Meanwhile, the signal measurement unit 2003 receives signals by bumps 32, included in the probe card 1000, for signal reception.
As described above, an electrical characteristics test is conducted by comparing a high-frequency signal to be applied and high-frequency signals to be received.
Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.
The method of manufacturing a membrane with bumps according to the present invention contributes to the sophistication, lower cost, and stabilized quality of probe cards, and is suitable for probe cards in general that are used to test fine electrical circuits formed on a semiconductor wafer, a liquid crystal display panel, a solar battery, or the like, by causing each of such probe cards to have surface contact with electrodes on an electrical circuit to simultaneously generate electrical contacts.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-296948 | Oct 2004 | JP | national |
