Patent Publication Number: US-2003234657-A1

Title: Method for producing a probe, mask for producing the probe, and probe

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a method for producing a probe used to measure various electric properties of a semiconductor integrated circuit as an object to be inspected, a mask for producing the probe, and a probe.  
       [0003] 2. Description of Related Art  
       [0004] Probes in probe cards used to measure various electric properties of a semiconductor integrated circuit are classified into a type produced by sharpening the tip of a thin line made of tungsten or the like and a type produced by etching a plate-form material having electric conductivity. As the latter type of probes, there are known a probe wherein the tip of a contact portion  600 A is flat (see FIG. 9(A)), a probe wherein the center of a contact portion  600 B is projected (see FIG. 9(B)), a probe wherein the center of a contact portion  600 C is hollow and edges are projected (see FIG. 9(C)), and other probes.  
       [0005] The above-mentioned conventional etched type probe has the following problems. First, in the case of the contact portion  600 A, the tip of which is flat as illustrated in FIG. 9(A), the contact area between the portion  600 A and a conductive pad  700  is large; therefore, when the contact pressure of the contact portion  600 A against the conductive pad  700  is small, the contact pressure per unit area becomes low. Thus, a good connection therebetween cannot be ensured. In the case that the conductive pad  700  is fine, an alignment gap is generated when the contact portion  600 A is inclined to the conductive pad  700  (see a broken line in FIG. 9(A)) As a result, they may not contact each other. In other words, when the contact portion  630 A is inclined, only an edge of the contact portion  600 A contacts the conductive pad  700  since the contact portion  600 A is flat; however, when an alignment gap is generated, it is feared that the edge of the contact portion  60 CA gets out of the conductive pad  700 .  
       [0006] Secondary, in the case of the probes wherein the center of the contact portion  600 B is projected as illustrated in FIG. 9(B), it is difficult in a probe card wherein a great number of the probes are used that the heights of all the probes are made even, that is, that central projected portions  610 B are positioned on the same plane. When an alien substance is sandwiched between a side edge portion  620 B and the conductive pad  700 , the contact portion  600 B is raised away from the conductive pad  700  so that electric conduction may not be ensured.  
       [0007] Thirdly, in the case of the probe wherein the center of the contact portion  600 C is hollow and edges are projected as illustrated in FIG. 9(C), an alignment gap is caused when the conductive pad  700  is fine and the contact portion  600 C is inclined to the conductive pad  700  (see a broken line in FIG. 9(C)). As a result, they may not contact each other. That is, the number of sites in which the contact portion  600 C can contact the conductive pad  700  is originally only two; therefore, when the contact portion  600 C is inclined, only one site of the contact portion  600 C contacts the conductive pad  700 . When an alignment gap is caused at this time, it is feared that the only one site also gets out of the conductive pad  700 . Moreover, an alien substance is sandwiched between the contact portion  600 C arid the conductive pad  700  so that electric conduction may not be ensured since only two sites are present as the sites wherein the contact portion can contact the conductive pad  700 .  
       [0008] In light of the above-mentioned situation, the present invention has been made. An object of the present invention is to provide a method for producing a probe capable of keeping sure electric conduction between the probe and a conductive pad, a mask used in the method for producing the probe, and a probe.  
       SUMMARY OF THE INVENTION  
       [0009] The probe producing method according to the present invention is a method for producing a probe comprising a sharpened contact portion which can contact a conductive pad, which is an object to be inspected, comprising the step of: applying photo resists onto the front and rear faces of a conductive plate-form material, which is to make the probe; masking one face of the plate-form material with a first mask, and masking the other face of the plate-form material with a second mask; subjecting the photo resists to exposure to light and development; and using the photo resists remaining in the exposure and development step as mask materials to etch the plate-form material, wherein in a first opening in the first mask and a second opening in the second mask, there is a difference in shape between their portions corresponding to the contact portion.  
       [0010] The mask for producing a probe according to the present invention comprises a first mask used when a photo resist applied onto one face of a conductive plate-form material, which is to make the probe, is exposed to light and a second mask used when a photo resist applied onto the other face of the plate-form material is exposed to light, wherein in a first opening in the first mask and a second opening in the second mask, there is a difference in shape between their portions corresponding to the contact portion.  
       [0011] The probe according to the present invention is a probe comprising a sharpened contact portion which can contact a conductive pad, which is an object to be inspected, wherein the contact portion is hollowed from the side thereof. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 are views of a probe produced in a probe producing method according to an embodiment of the present invention, FIG. 1(A) is a schematic front view thereof, and FIG. 1(B) is a schematic side view thereof.  
     [0013]FIG. 2 is a schematic plan view of a first mask used in the probe producing method according to the embodiment of the present invention.  
     [0014]FIG. 3 is a schematic plan view of a second mask used in the probe producing method according to the embodiment of the present invention.  
     [0015]FIG. 4 are schematic explanatory views illustrating steps of the probe producing method according to the embodiment of the present invention.  
     [0016]FIG. 5 is a schematic explanatory view illustrating the effect of the probe produced by the probe producing method according to the embodiment of the present invention.  
     [0017]FIG. 6 is a schematic perspective view of another probe produced in the same producing method.  
     [0018]FIG. 7 are schematic enlarged views of the tip of another probe, FIG. 7(A) is a schematic front view thereof, FIG. 7(B) is a schematic side view thereof, and FIG. 7(C) is a schematic rear view thereof.  
     [0019]FIG. 8 are schematic enlarged views of the tip of another probe, FIG. 8(A) is a schematic front view thereof, FIG. 8(B) is a schematic side view thereof, and FIG. 8(C) is a schematic rear view thereof.  
     [0020]FIG. 9 is a schematically explanatory view for showing problems of conventional probes.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0021]FIG. 1 are views of a probe produced in a probe producing method according to an embodiment of the present invention, FIG. 1(A) is a schematic front view thereof, FIG. 1(B) is a schematic side view thereof, FIG. 2 is a schematic plan view of a first mask used in the probe producing method according to the embodiment of the present invention, FIG. 3 is a schematic plan view of a second mask used in the probe producing method according to the embodiment of the present invention, FIGS.  4 (A) to  4 (E) are schematic explanatory views illustrating steps of the probe producing method according to the embodiment of the present invention, FIG. 5 is a schematic explanatory view illustrating the effect of the probe produced by the probe producing method according to the embodiment of the present invention, FIG. 6 is a schematic perspective view of another probe produced in the same producing method, FIGS.  7 (A) to  7 (C) are schematic enlarged views of the tip of another probe, FIG. 7(A) is a schematic front view thereof, FIG. 7(B) is a schematic side view thereof, and FIG. 7(C) is a schematic rear view thereof, FIG. 8(A) is a schematic front view thereof, FIG. 8(B) is a schematic side view thereof, and FIG. 8(C) is a schematic rear view thereof.  
     [0022] First, a probe  100  produced in the probe producing method according to an embodiment of the present invention will be described referring to FIGS.  1 (A) to  1 (B). This probe  100  has a base portion wherein projected portions  111  and  112 , which are substantially parallel to each other, are formed a curved portion  120  curved into a substantial U-shape from an end of this base portion  110 ; an arm portion  130  extended from this curved portion  120 ; and a contact portion  140  at the tip of this arm portion  130 .  
     [0023] The tip of the projected portion  111  is sharpened. The other projected portion  112  is formed into a straight line.  
     [0024] In the contact portion  140 , the tip thereof is hollowed from the front side to the rear side. That is, the tip is not merely tapered from the front side to the rear side but the tip is made of a hollow curved face. This contact portion  140  is positioned just under the projected portion  112 .  
     [0025] The curved portion  120  is a portion which warps when the contact portion  140  is brought into contact with a conductive pad of a semiconductor integrated circuit, which is an object to be measured, under pressure so as to keep a given contact pressure between the contact portion  140  and the conductive pad.  
     [0026] In a first mask  200  for producing this probe  100 , a first opening  210  is made. This first opening  210  is an opening corresponding to portions other than the contact portion  140  of the probe  100  to be produced, that is, the base portion  110  including the projected portions  111  and  112 , the curved portion  120  and the arm portion  130 .  
     [0027] In a second mask  300 , a second opening  310  is made. This second opening portion  310  is an opening corresponding to the whole including the contact portion  140  of the probe  100 . Accordingly, this second opening  310  has the same shape as the probe  100  when the second opening  310  is viewed from the front.  
     [0028] The external form of the first mask  200  and that of the second mask  300  are set to the same size. Thus, when the front and rear faces of a plate-form material  400  having electric conductivity, which is to make the probe  100 , are masked, portions except the contact portion  140  are consistent in the front and rear faces of the plate-form material  400 .  
     [0029] A method of using the first mask  200  and the second mask  300  to produce a probe will be described, referring to FIGS.  4 (A) to  4 (E). In FIGS.  4 (A) to  4 (E), the dimensions of respective members or portions are exaggeratingly drawn for the convenience of the drawing of FIG. 4.  
     [0030] This probe producing method has the step of applying photo resists  500  onto the front and rear faces of the plate-form material  400  having electric conductivity, which is to make the probe  100 , the step of masking one of the front and rear faces of the plate-form material  400  with the first mask  200  and masking the other face with the second mask  300 , the step of subjecting the photo resists  500  to exposure to light and development, and the step of using the photo resists  500  remaining in this exposure and development step as mask materials  510  to etch the plate-form material  400 .  
     [0031] As the plate-form material  400 , for example, beryllium copper, stainless steel, or the like is used. Since the thickness of this plate-form material  400  is equal to the thickness of the probe  100  to be produced, the plate-form material  400  having a thickness of 60 μm is used.  
     [0032] The photo resists  500  are applied onto the front and rear faces by an ordinary method such as spray coating or spin coating (see FIG. 4(A)). In the same way as usual, this photo resists  500  are subjected to pre-baking or the like. As the photo resists  500 , photo resists of a type in which exposed portions remain after development are used.  
     [0033] In the step of masking the front and rear faces of the plate-form material  400  onto which the photo resists  500  are applied with the first mask  200  and the second mask  300 , portions except the contact portion  140  are made consistent in the front and rear faces of the plate-form material  400 , as described above (see FIG. 4(B)).  
     [0034] In this state, the photo resists  500  are subjected to exposure to light and development. After the development, a mask material  510 A having no portion corresponding to the contact portion  140  is formed on the face with which the first mask  200  is masked, as illustrated in FIG. 4(C). A mask material  510 B having a portion corresponding to the contact portion  140  is formed on the other face with which the second mask  300  is masked. In FIGS.  4 (A) to  4 (E), only the portion which is to make the contact portion  140  (i.e., a section taken on A-A line in FIG. 1) is shown.  
     [0035] The mask materials  510  are used to perform etching. As a result, in the mask material  510 A formed through the first mask  200 , the portion corresponding to the contact portion  140  is also etched, as illustrated in FIG. 4(D), since the mask material  510 A has no portion corresponding to the contact portion  140 . On the other hand, in the mask material  150 B formed through the second mask  300 , the portion corresponding to the contact portion  140  is not etched since the mask material  510 B has the portion corresponding to the contact portion  140 .  
     [0036] Since the mask material  510 A formed through the first mask  200  and the mask material  5103  formed through the second mask  300  have portions corresponding to the portions other than the contact portion  140 , these portions are not etched.  
     [0037] About the portion corresponding to the contact portion  140 , the one face thereof is etched but the other face thereof is not etched; therefore, the other face has the same plane as the other portions but the one face does not have the same plane as the other portion. In other words, the portion corresponding to the contact portion  140  is formed to have a smaller thickness than the other portions. Furthermore, in the case that the etching is isotropic etching, the portion corresponding to the contact portion  140  has such a shape that this portion is hollowed from the one side (see FIG. 4(E)).  
     [0038] When the etching is completed, the photo resists  500  remaining as the mask materials  510 A and  510 B are removed. As a result, the probe is completed.  
     [0039] In the case that the thus-produced probe  100  contacts a conductive pad of a semiconductor integrated circuit, the contact area therebetween is small; therefore, the contact pressure per unit area is easily ensured even if the contact pressure is small. In the case that the conductive pad  700  is very small, the fear of poor conduction resulting from an alignment gap is far smaller in the probe  100  than in conventional probes even if the contact portion  140  is inclined to the conductive pad  700  (see a broken line in FIG. 5).  
     [0040] Needless to say, the probe according to the present invention is not limited to the probe  100  described as the above-mentioned embodiment, and embraces probes having other shapes. For example, the probe according to the present invention embraces probes as illustrated in FIGS. 6 and 7 or  8 .  
     [0041] The probe producing method according to the present invention is a method for producing a probe comprising a sharpened contact portion which can contact a conductive pad, which is an object to be inspected, comprising the steps of: applying photo resists onto the front and rear faces of a conductive plate-form material, which is to make the probe; masking one face of the plate-form material with a first mask, and masking the other face of the plate-form material with a second mask; subjecting the photo resists to exposure to light and development; and using the photo resists remaining in the exposure and development step as mask materials to etch the plate-form material, wherein in a first opening in the first mask and a second opening in the second mask, there is a difference in shape between their portions corresponding to the contact portion.  
     [0042] Thus, the shape difference between the portion corresponding to the contact portion in the first opening in the first mask and the portion corresponding to the contact portion in the second opening in the second mask causes a result that the front and rear faces are etched into different forms in the etching step. Therefore, the shape of the contact portion can be made into an unprecedented shape, specifically such a shape that this portion is hollowed from the side thereof. This contact portion makes it possible to ensure the contact pressure easily, as described above. Thus, the fear of poor conduction resulting from an alignment gap is very small, and a probe having a high reliability can be produced.  
     [0043] Moreover, the first opening is an opening for exposing portions corresponding to the portions other than the contact portion of the probe to the light, and the second opening is an opening for exposing the whole including the contact portion of the probe to the light; and in the masking step, portions corresponding to the portions other than the contact portion in the first opening in the first mask and portions corresponding to the portions other than the contact portion in the second opening in the second mask are made consistent in the front and rear faces of the plate-form material.  
     [0044] As a result, only the portion corresponding to the contact portion can be made different from the shape of the other portions.  
     [0045] The mask for producing a probe according to the present invention comprises a first mask used when a photo resist applied onto one face of a conductive plate-form material, which is to make the probe, is exposed to light and a second mask used when a photo resist applied onto the other face of the plate-form material is exposed to light, wherein in a first opening in the first mask and a second opening in the second mask, there is a difference in shape between their portions corresponding to the contact portion.  
     [0046] As a result, this producing mask is used to cause a result that the front and rear faces are etched into different forms in the step of etching the portion corresponding to the contact portion. Therefore, the shape of the contact portion can be made into an unprecedented shape, specifically such as a shape that the portion is hollowed from the side thereof. This contact portion makes it possible to ensure the contact pressure easily, as described above. Thus, the fear of poor conduction resulting from an alignment gap is very small, and a probe having a high reliability can be produced.  
     [0047] Furthermore, the probe according to the present invention is a probe comprising a sharpened contact portion which can contact a conductive pad, which is an object to be inspected, wherein the contact portion is hollowed from the side thereof. According to this probe, the contact pressure is easily ensured, and the fear of poor conduction resulting from an alignment gap can be made very small.