CN101111772A - Method for forming lithographically produced probe elements - Google Patents

Abstract

A method is provided for shaping tips of probe elements configured for use in a probe card to establish electrical communication with contacts of a semiconductor device to be tested. The method comprises the following steps: lithographically producing a plurality of probe elements, each probe element having a tip portion; and (b) removing material from the tip portions of the plurality of probe elements to form each tip portion into a shape suitable for piercing a contaminant layer of a surface to be probed by the probe elements.

Description

Forming method of probe element produced by lithography

Cross References to Related Applications

This application claims priority to US Provisional Application No. 60/633,017, filed December 3, 2004, the contents of which are incorporated herein by reference.

technical field

The invention relates to devices for testing integrated circuits. More particularly, the present invention relates to a method for shaping a lithographically produced probe element inserted into a probe card for semiconductor integrated circuit testing.

Background technique

In semiconductor integrated circuit fabrication, integrated circuits ("ICs") are typically tested during fabrication and prior to shipment to ensure proper operation. Wafer testing is a well-known testing technique generally used for product testing of semiconductor ICs mounted on a wafer, in which a temporary current is established between an automatic test equipment (ATE) and each IC mounted on a wafer, To prove the normal performance of the IC. Exemplary components used in wafer testing include an ATE test board, which is a multi-layer printed circuit board that connects to the ATE and transmits test signals back and forth between the ATE and the probe card. An exemplary probe card is a printed circuit that typically contains hundreds of probes (or "flex probes") arranged to make electrical contact with a series of connection terminals (or diecontacts) on an IC die. plate.

Known probe cards are available from Kulicke and Soffa Industries, Inc. of Willo Grove, PA. A particular probe card includes: a printed circuit board; a probe head having a plurality of flexible probes; and a space transformer electrically connecting the probes to the printed circuit board. A space transformer may comprise a multilayer ceramic substrate, or alternatively a multilayer organic substrate.

It is known to make multiple flexible probes using lithographic techniques. For example, US Patent Nos. 6,616,966 (Mathier et al.) and 6,677,245 (Zhou et al.) both disclose lithographic methods for fabricating flexible probes.

One difficulty with using probe cards is that the surface of the integrated circuit die contacts or pads that come into contact with the flexible probes is usually formed of a metal such as aluminum or copper that oxidizes easily to form an electrically insulating oxide layer. It is desirable to break this oxide layer by the flex probes to establish proper electrical communication between each die contact and each flex probe. Therefore, it is desirable to form the tip profile of each flexible probe in a manner that improves the ability of the flexible probe to penetrate the oxide layer. However, using conventional lithographic techniques, it is difficult to provide a flexible probe tip with the desired sharp edge best suited to pierce the oxide layer of the die contact.

Accordingly, it would be desirable to provide a method by which lithographically produced probe elements can be shaped to enhance the ability of the probe elements to establish electrical communication with die contacts.

Contents of the invention

According to an exemplary embodiment of the present invention, there is provided a method of processing a probe element configured for use in a probe card. The method includes lithographically fabricating a plurality of probe elements, each probe element having a tip. The method also includes removing material from the tip portions of the plurality of probe elements to form each tip portion into a shape suitable for piercing the contamination layer of the surface to be probed by the probe element.

According to another exemplary embodiment of the present invention, there is provided a method of processing a probe element configured for use in a probe card. The method includes fabricating a plurality of probe elements, each probe element having a tip portion. The method also includes removing material from the tip portions of the plurality of probe elements to form each tip portion into a shape suitable for piercing the contamination layer of the surface to be probed by the probe element. The removal step includes laser ablation of material from the needle tip.

According to yet another exemplary embodiment of the present invention, there is provided a method of processing a probe element configured for use in a probe card. The method includes: lithographically fabricating a plurality of probe elements, each probe element having a tip portion. The method also includes removing material from the tip portions of the plurality of probe elements to form each tip portion into a shape suitable for piercing the contamination layer of the surface to be probed by the probe element, the removing step comprising removing material from the tip portions Laser ablation of material.

The above and other features of the present invention, as well as advantages of the present invention, will become more apparent from the ensuing detailed description of the preferred embodiments shown in the accompanying drawings. As will be realized, the invention is capable of modifications in several respects, all without departing from the invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature and not restrictive.

Description of drawings

For purposes of illustrating the invention, the drawings in its presently preferred form are shown; it is to be understood that the invention is not limited to the precise arrangements and instrumentalities shown. In the attached picture:

1 is a block diagram illustrating a method of providing a probe element according to an exemplary embodiment of the present invention;

Figure 2A shows an exemplary probe tip shape processed according to the exemplary method shown in Figure 1;

Figure 2B shows a specific exemplary probe tip shape that can be made by the method shown in Figure 1;

Figure 3A illustrates an exemplary material removal system using a laser to remove material from a lithographically produced probe tip; and

3B illustrates another exemplary material removal system that uses a laser to remove material from a lithographically fabricated probe tip.

Detailed ways

According to an exemplary embodiment of the present invention, the present invention is directed to a method of forming a lithographically fabricated probe element for use in a probe card that establishes electrical communication with a die contact having an outer oxide layer. The method comprises the steps of: lithographically fabricating a plurality of probe elements; and removing material from each tip of the plurality of probe elements using a subtractive process to form each tip suitable for piercing an oxide layer. shape. For example, the subtractive treatment can be laser ablation. Additionally, the method may include the step of chemically polishing the tip of each probe element.

For example, a plurality of probe elements can be lithographically fabricated in a sheet, with the probe elements connected by tie bars or the like, where the tie bars are also fabricated during the lithographic process. After processing of the probe element according to the invention (e.g. shaping the tip portion of the probe element), the probe can be singulated from the sheet (e.g. by cutting the tie rods holding the probe element to the sheet, etc. ), and then bond (e.g., wedge bond) the separated probe element to a contact location on a substrate (e.g., a space transformer such as an MLO or MLC space transformer, a PCB, etc.), where the substrate is configured as a probe part of the card.

Referring to the drawings, there is shown shaping the tip of a lithographically fabricated probe element 30 used in connection with a probe card to establish electrical communication with a contact portion of a semiconductor device (eg, a semiconductor device in the form of a wafer, not shown). The method 10, wherein the contacts may have a contamination layer (eg, outer oxide layer, not shown). Referring specifically to FIG. 1 , the method 10 includes a step 12 of lithographically (eg, using photolithography, stereolithography, etc.) fabricating a plurality of probe elements 30 . Step 12 is conventional and well known in the field of semiconductor manufacturing. A typical lithographic process generally involves laminating the desired material, masking the laminated material to define a precise product shape, UV imaging the masked material, removing the mask, and then developing the imaged material. Other lithographic processes can also be devised to make probe elements.

Referring to FIG. 2A , the probe elements 30 each have a needle tip 32 . For example, the tip 32 is fabricated/shaped in a first direction by a lithographic process 12 . As shown in the left portion of FIG. 2A , tip 32 is shaped by lithography such that there are ribs in tip 32 , where the ribs are defined by less material in the X direction near tip 32 . Excess material is removed from the probe tip 32 (e.g., as indicated by the Y-direction arrow shown in FIG. Formed into a shape suitable for piercing a contamination layer (not shown) such as an oxide layer.

For example, the shaped probe tip 34 may have a shape other than the pyramidal shape shown in FIG. 2A. FIG. 2B provides side perspective and top views of a probe tip having other exemplary shapes, such as a trapezoidal shape 40 , a parabolic shape 42 , and a contoured shape 44 .

Complete processing can result in a series of specific shapes that further define the dimensions of the contact tip surface. In operation of the probe 30, the amount of friction that the tip 34 applies to the contact surface of the die (or other contact surface of the device to be tested) depends on a variety of parameters including, for example, the die contact material, the size of the tip 34 and shape, overdrive distance and elasticity of probe 30 . The orientation of the shaped tip 34 is designed to act in conjunction with the designed frictional forces of the probe when in contact with the probe and die surface, preferably with contaminants (e.g. Oxide layer) is pushed away from the chip contact surface with minimal debris.

Referring to FIGS. 1 and 3A , the method 10 further includes step 14 : mounting the probe element 30 to the support plate 50 . The support plate 50 is movable relative to the ablation laser 60 . The support plate 50 is oriented relative to the laser 60 so that the beam 62 of the laser is aimed at the probe tip 32 at an angle suitable for removing material from the tip 32 to form the desired tip shape (step 16). The support plate 50 carrying the probe 30 can be tilted at an angle relative to the laser 60 to obtain the desired final tip shape. As shown in FIG. 3A , the support plate 50 is also disposed at an angle relative to the surface 50A supporting the support plate 50 . It should be appreciated that surface 50A may be configured at an angle relative to laser 60 (eg, surface 50A may be the surface of an angled table, etc.) so that a movable (movable to provide an angle) support plate 50 is not employed.

Calibrating the position, power level, and rate of movement of the laser 60 (e.g., along a gantry 66 using a carriage 64) relative to the plurality of probe tips 32 to precisely determine the laser to be removed from each probe tip 32. the correct amount of material. For example, laser 60 is scanned over probe tips 32 along a first pass to remove material from each probe tip 32 (step 18). In certain exemplary embodiments of the invention, laser 60 is then redirected relative to probe tip 32 and scanned along a second pass to remove excess material to form the desired tip shape (step 20). For example, the stylet 30 can be flipped so that opposite sides of each tip 32 can be shaped.

For example, subtraction processing is performed using an ablation laser. An exemplary laser type for this treatment is a diode pumped ND:YAG laser. However, excimer, _CO2 , or other types of laser light may also be used. Optionally, other methods, such as micro-electrode discharge machining (micro-electrode discharge machining, abbreviated as μEDM), can also be used. For μEDM treatment, see "Non-damage Probing and Analysis of ILD Damage at Scrub Marks", J. Yorita, et al., Sumitomo Electric Industries, 2004 Southwest Test Workshop Proceedings, June 7, 2004.

The probe tip can be chemically ground (step 22). The probe material determines the ideal chemical polishing solution to use. For certain BeCu probes, solutions of 0.5% nitric acid, 45.5% phosphoric acid, and 50% acetic acid provided good results. The probe was immersed in the solution for 1 to 5 minutes at room temperature or slightly warmer (35 °C), and then rinsed gently with deionized water. For certain nickel alloys, dilute (10:1) nitric or sulfuric acid grinding solutions at 40°C provide good results. An exemplary technique is to immerse the formed thin-sheet part in an etchant for a short period of time (eg, 1 to 2 minutes), followed by a rinse with deionized water. If residue remains on the edges, the acid concentration and/or time of the etch can be increased. This step can be combined with a surface preparation step for the subsequent plating treatment.

In FIG. 3A , laser 60 is moved along rail 66 by carriage 64 . In contrast, in an alternative configuration shown in FIG. 3B, laser 60A is fixedly positioned relative to rail frame 66A. Mirror 68 is configured to be moved along track 66A by carriage 64A such that beam 62A (emanating from laser 60A) is reflected from mirror 68 to probe tip 32 . Figure 3B is an alternative configuration to Figure 3A, although other configurations are contemplated within the scope of the present invention.

Although FIG. 1 has steps presented in a particular order, the invention is not limited thereto. For example, some of the steps may be omitted, or alternative steps may be substituted. Also, the order of steps may be rearranged in certain configurations of the invention.

Although FIGS. 3A-3B illustrate a probe element 30 having a particular shape (eg, a curved probe element), the invention is not limited thereto. The present invention relates to probe elements fabricated by any type of lithography (eg, using photolithography, stereolithography, etc.).

Although the invention has been described with respect to a particular forming technique (eg, laser ablation, microelectrode release machining, etc.), the invention is not limited thereto. Obviously other techniques can be envisaged.

While FIGS. 3A-3B illustrate an exemplary support structure for arranging sets of probe elements 30 (connected to tie bars, etc. formed during lithography) during a subtractive process, the invention is not limited thereto. For example, the present invention is not limited to the use of support plates that may be oriented at an angle, such as support plate 50 shown in FIGS. 3A-3B. The illustrated structure is exemplary in nature.

In certain exemplary embodiments of the invention, the probe elements may be formed by techniques other than lithographic processing, eg, stamping, etching, plating, and the like.

The present invention may be embodied in other specific forms without departing from the spirit and essential attributes of the invention. While the invention has been described and illustrated with respect to exemplary embodiments of the invention, it should be understood by those skilled in the art that the above and many other changes may be made in and to the invention without departing from the spirit and scope of the invention. other changes, omissions, and additions.

Claims (20)

1. A method of processing a probe element configured for use in a probe card, the method comprising the steps of: lithographically fabricating a plurality of probe elements, each of the plurality of probe elements having a tip portion; and Material is removed from the tip portions of the plurality of probe elements to form each tip portion into a shape suitable for piercing a contamination layer of a surface to be probed by the probe element. 2. The method of claim 1, wherein the removing step includes laser ablation to remove the material. 3. The method of claim 1, wherein the removing step comprises microelectrode electrical discharge machining to remove the material. 4. The method of claim 1, further comprising grinding the tip portion of each probe element after the removing step. 5. The method of claim 4, wherein the grinding step includes chemically grinding the tip portion of the probe element. 6. The method of claim 1, wherein the removing step comprises removing the material to form the tip portion into a trapezoidal shape, a parabolic shape, a contoured shape, or a pyramidal shape. 7. The method of claim 1, wherein the removing step comprises removing the material from the first side of the tip portion in a first removing step, and then removing the material from the tip portion in a second removing step. The material is removed from the second side of the portion. 8. The method of claim 1 , further comprising: supporting the plurality of probe elements with sides of the plurality of probe elements on a support plate, the support plate configured to be at an angle relative to The structure orientation to remove the material from. 9. The method according to claim 8, wherein the supporting step comprises: supporting the plurality of probe elements on the support plate with the sides of the plurality of probe elements, the support plate being supported by configured to be oriented at an angle relative to a laser ablation device for removing said material. 10. A method of processing probe elements configured for use in a probe card, the method comprising the steps of: fabricating a plurality of probe elements each having a tip portion; and Material is removed from the tip portions of the plurality of probe elements to form each of the tip portions into a shape suitable for piercing the contamination layer of the surface to be probed by the probe element, the removing Steps include laser ablation of said material from said needle tip. 11. The method of claim 10, wherein the fabricating step comprises: lithographically fabricating the plurality of probe elements. 12. The method of claim 10, further comprising grinding the tip portion of each of the probe elements after the removing step. 13. The method of claim 12, wherein the grinding step includes chemically grinding the tip portion of the probe element. 14. The method of claim 10, wherein the removing step includes removing the material to form the tip portion into a trapezoidal shape, a parabolic shape, a contoured shape, or a pyramidal shape. 15. The method of claim 10, wherein the removing step comprises removing the material from the first side of the tip portion in a first removing step, and then removing the material from the tip portion in a second removing step. The material is removed from the second side of the portion. 16. The method of claim 10, further comprising: supporting the plurality of probe elements with sides of the plurality of probe elements on a support plate, the support plate configured at an angle relative to The structure orientation to remove the material from. 17. The method according to claim 16, wherein said supporting step comprises: supporting said plurality of probe elements on said support plate with sides of said plurality of probe elements, said support plate being supported by configured to be oriented at an angle relative to a laser ablation device for removing said material. 18. A method of processing probe elements used in a probe card, said method comprising the steps of: lithographically fabricating a plurality of probe elements, each of the plurality of probe elements having a tip portion; and removing material from the tip portions of the plurality of probe elements to form each of the tip portions into a shape suitable for piercing a contamination layer of a surface to be probed by the probe element, the removing step including laser ablation of the material from the needle tip. 19. The method of claim 18, wherein the removing step comprises removing the material to form the tip portion into a trapezoidal shape, a parabolic shape, a contoured shape, or a pyramidal shape. 20. The method of claim 18, wherein the removing step comprises removing the material from the first side of the tip portion in a first removing step, and then removing the material from the tip portion in a second removing step. The material is removed from the second side of the portion.

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