Method of manufacturing probes of a membrane probe card

Abstract

The invention relates to a method of manufacturing probes of membrane probe card. The process includes fixing a metal block on a working substrate, and laying a first dielectric layer on the working substrate, using a photolithography process to construct conductive trace and a dielectric layer layer by layer on the metal block and the working substrate, so that the conductive trace is connected to the metal block, and the first and second dielectric layers isolate the conductive trace, and the membrane metal block device is completed after the working substrate removed, and the metal block is processed into a probe entity. Through this manufacturing method, the probe end of membrane probe has a multi-contact bump structure with mechanical strength enhanced, so that membrane probe can perform function of contacting the side of soder bump in wafer test, thereby simultaneously fixing probe electrical contact resistance issue in wafer test and flip-chip bonding issue in packing process.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer testing, and more specifically, to a thin-film probe card. Prior Technology

[0002] As is well known, semiconductor high-frequency products (RF products) need to meet two basic requirements in wafer testing and packaging processes. The probe length for wafer testing is on the order of micrometers, also known as micro-contact probes, which can avoid probe inductance problems. Therefore, thin-film probe cards are required in the wafer testing stage. In addition, the packaging process adopts flip-chip packaging technology, in which the crystal connection bumps are copper pillar solder bumps.

[0003] In addition, wafer testing processes require low probe electrical contact resistance (C-res), high efficiency in cleaning probe tips during wafer testing, and solder bump appearance specifications that are not affected by the probes. Furthermore, packaging processes require high flip chip bonding.

[0004] To further explain, the part of an electronic device used to connect to an external circuit is called a connection bump. The connection bump of a crystal is located at the top of the crystal and is called a crystal connection bump. The main types are aluminum pads and solder bumps. The purpose of a thin-film probe card is to form an electrical circuit by contacting the crystal connection bump with the probe tip when electrically testing the crystal. The probe tip is called a probe contact bump. Currently, the only type of thin-film probe contact bump is a single contact bump, and it is a planar contact with the top of the crystal connection bump.

[0005] Current industry methods for fabricating thin-film probes are based on patent US 7,533,462 B2. First, a probe-shaped recess is pressed into the surface of a metal substrate. An insulating thin film layer is then deposited around the recess on the metal substrate surface. Next, different metals are sequentially filled into the recess using an electroplating process to obtain the probe. The entire probe is then ground and polished, followed by photolithography. The conductive lines and insulating layers are fabricated layer by layer, and finally the metal substrate is removed with acid to complete the thin film probe device. The entire fabrication method is to first make the probe body by electroplating and then fabricate the conductive lines and insulating layers layer by layer. Under the limitation of the electroplating process, the probe tip is a single planar contact bump and the mechanical strength of the probe is not good, such as pyramid-shaped probes, cylindrical probes, etc., which are all suitable for chips with aluminum pads for crystal connection bumps. However, for chips with solder bumps for crystal connection bumps, these probes are all solder bump top contact probes, as shown in the first figure, which illustrates the crystal connection bump structure and solder bump top contact method. It includes a crystal (200), which is composed of solder bumps (201) and copper pillars (202). The solder bump (201) has a flip-chip area (203) on the top. The solder bump (201) has a diameter d1 and a center line CL1; a thin film probe device (100) (membrane probe) The device consists of a probe (101) and a thin-film conductive wiring device (10). The thin-film conductive wiring device (10) consists of at least one conductive line (103) and an insulating film (102). The probe (101) consists of a base (113) and a contact bump (110). The contact bump (110) has a flat end, a diameter d2, a center line CL2, and a side angle ϴ. The probe (101) base (113) and the conductive line (103) are connected and fixed together in the insulating film (102). The thin-film probe device (100) is assembled on a probe card mechanism to form a thin-film probe card. The complete mechanism is not shown in the figure, only the relevant actions are described.

[0006] During wafer testing, as shown in Figures 1 and 2, the tester drives the wafer upward, causing the crystal (200) to connect to the bump and the probe to contact the bump (110). Further upward movement of the probe overtravel (OT) will produce the following types of results, explained below:

[0007] 1. When d2 > d1, the end face of the probe (101) contacts the bump (110) and flattens the top area of ​​the solder bump (201) with a relatively large flat surface. The probe indentation is shown in Figure 2 (A). The advantage is that it ensures that the appearance of the solder bump (201) meets the quality specifications and provides good conditions for the flip-chip process. However, the probe (101) cannot pierce the oxide layer on the surface of the solder bump (201) to obtain high electrical contact resistance. In addition, it is not easy to remove the accumulated oxide on the probe tip during the test. The test yield is lower than the expected value of the product. The production line must often take the probe card off the line for maintenance.

[0008] 2. When d2 < d1 and the center line CL2 coincides with CL1, i.e. ϵ = 0, the probe (101) contacts the end face of the bump (110) and presses into the top of the solder bump (201), leaving a dent. The probe dent is shown in Figure 2 (B). The advantage is that it can pierce the oxide layer to obtain low electrical contact resistance and the test yield can reach the product expectation value. However, the appearance deformation of the solder bump (201) will affect the flip-chip bonding of the next process.

[0009] 3. When d2 < d1, the bevel angle ϴ of the probe contact bump (110) is > 0 and the alignment error ϵ between the solder bump (201) and the probe (101) is > 0. During the process of the crystal contacting the probe contact bump (110), because the solder bump (201) is a curved surface, ϴ > 0. Furthermore, the insulating film is an elastomer, which causes the probe to push some of the solder bumps (201) outward, eventually resulting in severe deformation of the solder bumps (201). The probe indentation is shown in the second figure (C). The probe (101) can pierce the oxide layer when it contacts the bump (110) to obtain low electrical contact resistance. However, the solder bumps (201) need to be tempered a second time due to severe deformation to ensure the flip-chip bonding of the next process, which increases costs and reduces yield. This is a serious problem. The overall alignment error ϵ is caused by the manufacturing precision of the probe (101) contacting the bump (110), the precision of the crystal solder bumps (201), and the alignment accuracy of the tester. In reality, it is difficult for all probes (101) and their corresponding solder bumps (201) to obtain zero error ϵ=0.

[0010] For the above-mentioned thin-film probes with single contact bumps to solder bump crystals, it is not easy to simultaneously ensure good electrical contact resistance C-res of the probe and appearance quality of the crystal solder bumps during wafer testing. The former will result in low wafer testing yield, and the latter will result in low flip-chip bonding during packaging. Moreover, the overall alignment error problem cannot be solved by this probe tip structure design. All of these will impact product quality and production costs, which is an urgent problem to be solved in the industry.

[0011] Therefore, based on the above, the inventor, drawing on years of rich design, development and practical manufacturing experience in the related industry, has further researched and improved upon the technology to provide a method for manufacturing thin film probes, making it more useful and achieving greater practical value. Summary of the Invention

[0012] The main objective of this invention is to provide a method for manufacturing a thin-film probe, particularly a thin-film probe for testing crystal connection bumps that are solder bumps. This thin-film probe can achieve the side contact function of the solder bump, and at the same time solves the problems of electrical contact impedance of the thin-film probe, and the appearance and specifications of the solder bump are not affected by the probe contact, thus affecting the flip-chip bonding of the packaging process.

[0013] To address the above problems, the main objective and effectiveness of this invention's novel method for fabricating thin-film probes are achieved through the following specific technical means:

[0014] First, the metal block is fixed on the working substrate. Then, the insulating layer and conductive lines are fabricated layer by layer on the metal block and the working substrate using a photolithography process. After removing the working substrate, the thin film metal block device is completed. The metal block is then processed into the probe entity of the original design. The probe tip shape can be diverse, allowing the thin film probe to make side contact with the solder bump, which can solve the problems caused by the top contact method of the solder bump. This method does not use the previous electroplating process to make the probe entity.

[0015] In a preferred embodiment of the present invention, the metal block is precision machined using an ultrashort pulse laser to form the probe entity.

[0016] In a preferred embodiment of the present invention, the probe tip is composed of a plurality of contact bumps.

[0017] In a preferred embodiment of the present invention, the probe contact bump corresponds to a crystal solder bump with a side contact type. Simple Explanation of the Diagram

[0018] Figure 1: A schematic diagram of a single-plane contact bump and a copper pillar solder bump at the tip of a thin-film probe in the prior art. Figure 2: (A) to (C) respectively represent schematic diagrams of probe indentations drawn for the solder bump top contact instance type. Figure 3: Schematic diagram of the appearance of the working substrate of the present invention. Figure 4: Schematic diagram of the appearance of the metal component of the present invention. Figure 5: A cross-sectional schematic diagram of the recessed space created on the working substrate of the present invention. Figure 6: A cross-sectional view of the metal block fixed in the recessed space of the working substrate of the present invention. Figure 7: A cross-sectional schematic diagram of an insulating layer laid on the working substrate of the present invention. Figure 8: A cross-sectional schematic diagram of the thin-film conductive circuit device fabricated layer by layer according to the present invention. Figure 9: Schematic cross-sectional view of the thin-film metal block device of the present invention. Figure 10: A cross-sectional schematic diagram of the multi-contact bump needle tip of the thin film probe device of the present invention. Figure 11: A cross-sectional schematic diagram of the tip of a single contact bump in the thin film probe device of the present invention. Figure 12: A cross-sectional view showing the probe tips of the four contact bumps corresponding to the solder bumps on the crystal copper pillars. Figure 13: A three-dimensional schematic diagram of the probe tip with four contact bumps. Figure 14: A schematic diagram showing four contact bumps in contact with solder bumps with their center lines coinciding. Figure 15: A cross-sectional view of the four contact bumps in Figure 14 from another direction. Figure 16: Cross-sectional view of the force distribution on the solder bump. Figure 17: Top view of probe indentation on crystal solder bump. Figure 18: A schematic diagram showing four contact bumps in contact with solder bumps, but their centerlines do not coincide. Figure 19: A schematic diagram of four claw-shaped contact protrusions in another embodiment of the present invention. Figure 20: Top view showing the probe indentation left on the solder bump. Implementation

[0019] To provide a more complete and clear disclosure of the technical content, inventive purpose, and effects achieved by this invention, the following will specifically describe the embodiments of this invention to enable a better understanding of the technical features and manufacturing method of this invention. As for areas outside the scope of this application, only general descriptions are provided herein. Furthermore, the terms used herein are open-ended, such as "multi-contact bump pin tip," which has a broader scope and includes general terms such as "multi-pointed claw pin tip," "multi-inner vertical surface pin tip," etc.

[0020] First, a thin-film probe card contains a plurality of probes. In order to facilitate the description of its characteristic structure, this invention only describes the fabrication of one probe in detail. The methods for fabricating other probes are the same. The photolithography process is not included in the scope of this invention and will not be described in detail.

[0021] Please refer to Figures 3-10. The present invention provides a method for manufacturing a thin-film probe, the steps of which are as follows:

[0022] S1) is provided with a working substrate (42) and a metal block (41);

[0023] S2) A recessed space (421) is formed on the upper surface of the working substrate (42). The metal block (41) has a first end (411) and a second end (412). The first end (411) of the metal block (41) is embedded in the recessed space (421), thereby positioning and fixing the metal block (41) in the recessed space (421), while the second end (412) is exposed outside the recessed space (421).

[0024] S3) A thin-film conductive circuit device (43) is fabricated on the working substrate (42) at the end face of the second end (412) of the metal block (41) using a photolithography process. First, a first insulating layer (431) is laid on the substrate (42). The first insulating layer (431) is distributed around the second end (412) of the metal block (41).

[0025] S4) Then, using a photolithography process, at least one conductive line (432) and a second insulating layer (433) are fabricated layer by layer on the end face of the second end (412) of the metal block (41) and the first insulating layer (431) to complete the thin film conductive line device (43). The thin film conductive line device (43) is composed of at least one conductive line (432) and the first and second insulating layers (431) and (433).

[0026] S5) Then remove the working substrate (42) to complete a thin film metal block device (410);

[0027] S6) Then, the metal block (41) is precisely machined to produce the probe (44) entity, so as to complete the thin film probe device (400).

[0028] The following describes the actual operation process: In step S1, a working substrate (42) and a metal block (41) are set up. The working substrate (42) can be a metal plate [as shown in the third figure], and the metal block (41) can be a general metal [as shown in the fourth figure], or a high-strength alloy, or a hardened metal, etc., which are metal materials with good conductivity, and are not limited in shape and size. In step S2, a recessed space (421) is established on the upper surface of the working substrate (42). The recessed space (421) can be in any shape. The design is established on the working substrate (42). The recessed space (421) has the function of positioning and fixing the metal block (41) [as shown in Figure 5]. The first end (411) of the metal block (41) is inserted into the recessed space (421) [as shown in Figure 6], while the second end (412) is exposed to the outside. In this way, the metal block (41) is fixed on the working substrate (42). It is further explained that the working substrate (42) is mainly used to fix the metal block (41) and support the entire thin film metal block device process.

[0029] Next, in step S3, a first insulating layer (431) is deposited on the end face of the working substrate (42) using a photolithography process [as shown in Figure 7], and the first insulating layer (431) is distributed around the second end (412) of the metal block (41). Further processing is then performed using tools to grind and polish the entire surface where the first insulating layer (431) is deposited and the end face of the second end (412) of the metal block (41). In step S4, the photolithography process continues. In step S5, the working substrate (42) is removed using an appropriate process to expose the first end (411) of the metal block (41), forming a thin film metal block device (410) (as shown in Figure 9). Finally, in step S6, the first end (411) of the metal block (41) is precision machined to become the final designed probe (44) entity, and the probe (44) can be 50 to 150 micrometers long. Thus, the process of the thin film probe device (400) is completed.

[0030] However, during step S6, the metal block (41) can be processed into a thin-film probe device (400) with multiple contact bumps (444) and needle tips (443) [as shown in Figure 10] or a single contact bump (444) and needle tip [as shown in Figure 11]. During step 6 of the present invention, a photolithography process is first performed on the metal block (41), and then the metal block (41) is precisely processed into a probe (44) entity. The precision processing method can be ultra-short pulse laser precision processing or other suitable processing methods.

[0031] Next, a feasible embodiment of the precision machining of the probe tip of the present invention is further described, which uses triaxial ultra-short pulse laser precision machining technology to make the metal block (41) into a multi-contact bump probe, wherein the figure is represented by a probe tip with four contact bumps (444) [as shown in Figure 12], and the contact method between the probe (444) contact bumps (444) and the side of the crystal (300) solder bumps (301) is further described as follows:

[0032] Please refer to Figure 12, which is a cross-sectional view of the probe tip corresponding to the solder bump of the crystal copper pillar with four contact bumps. The thin film probe device (400) consists of a probe (44) and a thin film conductive circuit device (43). The thin film conductive circuit device (43) consists of at least one conductive line (432) and first and second insulating layers (431) and (433). The probe (44) includes a needle body (441) and a base (442). The needle tip (443) of the needle body (441) is surrounded by four contact bumps (444) [as shown in Figure 13]. Taking the upper right contact bump (444) as an example, the inner side of each contact bump (444) is provided with a Z1 line corresponding to the probe centerline. The relatively parallel vertical surfaces (445), namely the vertical arc surface ABCDA shown in the figure, and the contact front edge (446) at the front end of the vertical surface, namely the arc segment BC, the adjacent outer structure of these vertical surfaces (445) forms a support (447), so that the contact bump structure of the probe tip (443) is strong enough to contact the solder bump (301) [This probe tip contact bump technology is previously filed by the applicant, listed as application No. 113131467].

[0033] During wafer testing, the tester drives the wafer upward, causing the crystal connection bumps [i.e., solder bumps (301)] to contact the probe bumps (444), and then moves the probe overtravel upward. The following situations occur:

[0034] (i) When the centerlines of the solder bump (301) and the probe (44) coincide, i.e., ϵ = 0, the four contact leading edges (446) first simultaneously contact the side of the solder bump (301), achieving stable and effective electrical contact [as shown in Figure 14]. The crystal moves with the probe overtravel. As the number of contacts increases, the contact leading edge (446) cuts into the solder bump (301) and pierces the oxide layer of the solder bump. Further cross-sectional description in the zx direction [as shown in Figure 15] shows that the two symmetrical contact leading edges (446) pierce the side of the solder bump (301). The needle pressure stroke is absorbed by the compression deformation of the elastic body of the probe card (not shown). The resulting action and reaction forces are applied simultaneously to the crystal (300) solder bump (301) and the probe (44) contact bump (444). The contact needle marks on the side of the solder bump (301) mainly depend on the needle pressure stroke OT, the contact bump structure at the needle tip, the number of contact bumps and the elastic coefficient of the elastic body, etc. Appropriate design can obtain the lowest electrical contact resistance C-res and the best needle pressure marks (304).

[0035] Continuing, refer to Figure 16, which is a cross-sectional view of the force distribution (zx) on the solder bump. The probe forces F1 and F2 are symmetrically distributed and have the same value, so the net lateral force is zero. The total net force is balanced by the solder bump structure. The vectors F1 and F2 simultaneously point from the side of the solder bump to the inside of the solder bump, thus they can pierce the oxide layer and ensure sufficient and stable electrical contact, achieving low electrical contact resistance. At the same time, the reaction force also acts on the inside of the probe contact bump. The probe contact bump structure must be strong enough to avoid the contact bump from collapsing. Refer to Figure 17, which is a top view of the probe indentation on the crystal solder bump. The probe indentation mark (304) on the side is a small indentation left by the probe (444) contact bump (444) piercing the oxide layer on the side of the solder bump (301). It is far away from the flip-chip bonding area (303) of the solder bump (301) and does not affect the bonding force of the next process.

[0036] To achieve stable electrical and mechanical contact, the contact bumps are distributed at equal angles on the circumference of the needle diameter to achieve zero net lateral force and present stable contact. As long as the needle tip contact bump structure is strong enough, an appropriate number of contact bumps can provide the optimal electrical contact resistance. The method of the present invention can ensure that the contact bump structure is strong enough to avoid collapse problems.

[0037] (ii) When the center lines of the solder bump and the probe do not coincide, i.e. ϵ > 0, the four contact leading edges (446) of the probe (44) cannot contact the side of the solder bump (301) at the same time. The contact leading edge (446) that contacts first is inserted into the side of the solder bump (301) and the contact position is fixed. Since the four contact bumps (444) are in contact and the film is an elastic body, the final center line distance ϵ1 is almost equal to ϵ, i.e. there is no lateral slippage problem [as shown in Figure 18]. Moreover, this manufacturing method can obtain the minimum ϵ value and obtain a more uniform needle pressure mark (304), which does not affect the quality of the solder bump (301) and the flip-chip bonding area (303).

[0038] Please refer to Figure 19, which is a schematic diagram of four claws contacting the bumps in another embodiment of the present invention, and Figure 20, which is a top view of the probe indentation left on the solder bump. It can achieve the function of the previous embodiment. The method for manufacturing thin film probes of the present invention can indeed solve the problems caused by the previous manufacturing method.

[0039] Based on the above embodiments and analysis, this invention proposes a new method for fabricating thin-film probes that enables the thin-film probes to achieve solder bump side contact function, solves the problem of thin-film probe testing solder bump crystals, ensures good electrical contact impedance C-res and solder bump quality, and thus ensures good flip-chip performance in the packaging process.

[0040] As can be seen from the above description and implementation of the present invention, compared with the prior art, the present invention mainly has the following advantages:

[0041] 1. The thin film probe of the present invention is made by directly fixing the metal block to the working substrate, without the need to use electroplating method to make the probe as in the conventional technology, which has the effect of simplifying the process.

[0042] 2. The method for manufacturing thin-film probe cards of the present invention can be used to manufacture multi-contact bump probe tip test solder bump crystals or single-contact bump test aluminum pad crystals, and has a wide range of versatility.

[0043] 3. Regarding the probe height, the maximum probe height of this invention is determined by the testing frequency and the strength of the probe structure, which in turn determines the height of the metal block. This is completely different from the previous technology where the probe height was limited by manufacturing factors, and can improve the service life of the thin film probe card.

[0044] 4. The probe tip position (x, y, z) of this invention has high accuracy and is determined by the final precision machining process, such as ultra-short pulse laser precision machining, which is completely different from the previous technology where the position was determined before the electroplating process. Therefore, the accuracy of the probe tip position (x, y, z) is greatly improved.

[0045] 5. The probe structure of this invention has high strength. By selecting a metal block to achieve the purpose, it is possible to create a multi-contact bump probe tip and achieve the function of solder bump side contact.

[0046] However, the foregoing embodiments or figures are not intended to limit the product structure or usage of the present invention. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of the present invention.

[0047] In conclusion, the embodiments of the present invention can indeed achieve the expected effects, and the specific structure disclosed therein has not only never been seen in similar products, but has also not been disclosed before the application. It fully complies with the provisions and requirements of the Patent Law. Therefore, we hereby file an application for an invention patent and respectfully request your review and grant of a patent, which would be of great benefit.

[0048] Learned technology 100: Thin Film Probe Device 101: Probe 10: Thin-film conductive circuit device 102: Insulating film 103: Conductive circuit 110: Contact bump 113: Base 200: Crystal 201: Solder bump 202: Copper Pillar 203: Flip-chip region This invention technology 300: Crystal 301: Solder bump 303: Flip Chip Bonding Region 304: Needle indentation marks 400: Thin Film Probe Device 410: Thin-film metal block device 41: Metal block 411: First end 412: Second end 42: Working substrate 421: Recessed Space 43: Thin-film conductive circuit device 431: First insulating layer 432: Conductive circuit 433: Second insulating layer 44: Probe 441: Needle body 442: Base 443: Needle tip 444: Contact bump 445: Vertical plane 446: Contact Leading Edge 447: Support

Claims

1. A method for manufacturing a thin-film probe, comprising the following steps: S1) providing a working substrate and a metal block; S2) establishing a recessed space on the upper surface of the working substrate, the metal block having a first end and a second end, the first end of the metal block being embedded in the recessed space, thereby positioning and fixing the metal block within the recessed space, while the second end is exposed outside the recessed space; S3) fabricating a thin-film conductive circuit device on the end face of the second end of the metal block using a photolithography process on the working substrate, firstly laying a first insulating layer, the first insulating layer being distributed around the second end of the metal block; S4) then continuously fabricating at least one conductive line and a second insulating layer layer by layer on the end face of the second end of the metal block and the first insulating layer using a photolithography process to complete the thin-film conductive circuit device, wherein the thin-film conductive circuit device is composed of at least one conductive line and the first and second insulating layers; S5) then removing the working substrate to complete a thin-film metal block device; S6) then precision machining the metal block to form a probe entity to complete the thin-film probe device.

2. The method for manufacturing a thin-film probe as described in claim 1, wherein in step S6 the metal block is precision machined using an ultrashort pulse laser to form the probe entity.

3. The method for manufacturing a thin film probe as described in claim 2, wherein the probe tip of the thin film probe device is composed of a plurality of contact bumps.

4. The method for manufacturing a thin film probe as described in claim 3, wherein the probe contact bumps of the thin film probe device adopt a side contact type corresponding to the crystal solder bumps.

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