JP2008004730A - Chuck for prober - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a chuck for prober of simple structure in which measurement can be performed with high precision by reducing leak current. <P>SOLUTION: The chuck for prober for holding a mounted wafer comprises a chuck top 31 made of a conductive material and mounting a wafer, an insulation member 32 made of an insulating material and supporting a bottom surface of the chuck top, and a back plate 34 provided on the underside of the insulation member and arranged to contain a member internally and exhibiting conductivity at least partially on the surface. The insulation member 32 has an upper surface conductive layer 32A provided on the upper surface and a lower surface conductive layer 32B provided on the lower surface wherein the upper surface conductive layer 32A and the lower surface conductive layer 32B are insulated from each other. The upper surface conductive layer touches the bottom surface of the chuck top 31 and the lower surface conductive layer 32B touches the conductive surface of the back plate 34. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a prober chuck for holding a wafer in a prober used for electrical inspection of a semiconductor circuit (die) of an electronic device formed on a wafer.

  In the manufacturing process of an electronic element such as a semiconductor element, a large number of semiconductor circuits (dies) are formed on a thin plate-like wafer such as a semiconductor wafer. The dies formed on the wafer are separated and assembled as electronic components and packaged. Before the separation, a die sort test (probe test) is performed to check the operation of each die formed on the wafer.

  In the probe test, the wafer is placed on the prober stage and fixed, and the probe is brought into contact with the electrode of the die. Then, power and signals are supplied from the tester to some probes, and the output signal is detected by the tester to check whether the die operates normally. There are various types of inspection contents depending on the die to be inspected, but a minute current may be measured with high accuracy for analysis of a transistor or the like. The present invention is directed to a prober probe capable of measuring such a minute current with high accuracy.

  The probe test may be performed at a high or low temperature depending on the specifications of the die usage environment. Such a measurement is performed by setting the chuck on which the wafer is placed to a predetermined temperature, The process is performed at a predetermined temperature.

  FIG. 1 is a diagram illustrating a configuration example of a prober for a prober described in Patent Document 1 and capable of measuring at a high temperature and measuring a minute current. As shown in FIG. 1, the prober chuck includes a conductive chuck top 11 on which a wafer is placed, an insulating member 12 that holds the conductive chuck top 11 so as to be electrically insulated from other parts, and an insulating material. A back plate 14 that supports the member 12 and a heater 13 provided in the back plate 14 are included. A guard layer 12A is formed on the lower surface of the insulating member 12 with a conductive material such as nickel plating. Further, when the back plate 14 is made of a metal material or is made of an insulating material, a guard layer is formed on the surface thereof with a conductive material such as nickel plating. By applying the same potential to the conductive chuck top 11 and the guard layer, noise current and leakage current are suppressed.

  When the stage is cooled in order to inspect the wafer at a low temperature, it is generally performed by flowing a cooling fluid through a cooling liquid or air conduit provided inside or below the conductive chuck 22. is there. The present invention is directed to a chuck provided with a temperature adjustment mechanism capable of controlling at least one of high temperature and low temperature.

  The back plate 14 is not connected to the frame ground FG, and the frame is insulated by a high insulating material and electrically separated.

  Further, a non-conductive (insulating) chuck top such as ceramics may be used instead of the metal chuck top. FIG. 2 is a diagram showing a configuration example of a prober probe capable of measuring at a high temperature and measuring a minute current using an insulating chuck top.

  As shown in FIG. 2, a conductive layer 21 </ b> A is provided on the surface of the insulating chuck top 21. The insulating chuck top 21 is supported by a metal spacer 22, the metal spacer 22 is supported by a back plate 24, and a heater 23 is provided inside the back plate 24. The heater 23 is electromagnetically shielded from heater noise by a shield plate bonded to the metal spacer 22 and insulated. The cooling mechanism is provided inside the insulating chuck top 21 or inside the metal spacer 22.

  Patent Documents 2 to 4 describe a ceramic chuck integrally formed so as to have a conductor layer on the surface, a guard layer made of a conductive material inside, and a heating element on the bottom surface.

JP 2004-63486 A JP 2001-33484 A JP 2001-135680 A JP 2001-135681 A

  When measurement is performed using the prober for a prober described in Patent Documents 2 to 4, the leakage current is very small even at high and low temperatures, and high-precision measurement can be performed. On the other hand, when the prober chuck shown in FIGS. 1 and 2 is used, it is small when measured at high or low temperatures, but leaks compared to the case where the prober chucks described in Patent Documents 2 to 4 are used. It was found that the current increased and the measurement accuracy decreased.

  As described above, the prober chucks described in Patent Documents 2 to 4 are superior in measurement accuracy compared to the prober chucks of FIGS. 1 and 2, but the problem is that the structure is complicated and the manufacturing cost is high. was there.

  It is an object of the present invention to reduce the leakage current and perform highly accurate measurement even with the prober chuck having the simple structure shown in FIGS.

  In order to achieve the above object, the prober chuck of the present invention is characterized in that a conductive layer is formed on the surface of an insulating member in contact with a metal member.

  In other words, the prober chuck according to the present invention is a prober chuck for holding a mounted wafer, made of a conductive material, made of a chuck top on which the wafer is mounted, and an insulating material. An insulating member that supports the bottom surface of the top; and a back plate that is provided on the lower side of the insulating member and configured to accommodate the member therein, and at least a part of the surface of which is conductive. The member includes an upper surface conductive layer provided on the upper surface and a lower surface conductive layer provided on the lower surface, and the upper surface conductive layer and the lower surface conductive layer are insulated from each other, and the upper surface conductive layer is the chuck top. The lower conductive layer is in contact with the conductive surface of the back plate.

  The prober chuck of the present invention is a prober chuck for holding a mounted wafer, made of an insulating material, and made of a conductive material and a chuck top on which the wafer is mounted. A conductive member that supports the bottom surface of the chuck top; and a back plate that is provided on the lower side of the conductive member and is configured to accommodate the member therein, and at least a part of the surface is conductive. The chuck top includes a lower conductive layer provided on a lower surface, and the lower conductive layer is in contact with a surface of the conductive member.

  The inventor of the present application made various attempts to reduce the leakage current, and found that the leakage current can be reduced by forming a conductive layer on the surface of the insulating member in contact with the metal member. The reason is considered as follows.

  The prober chuck has a part formed of a metal material having a high coefficient of thermal expansion and a part formed of an insulating material such as ceramics having a coefficient of thermal expansion smaller than that of the metal material, and is configured to be in close contact with each other. Has been. As described above, when the temperature of the heater or the cooling mechanism is changed in order to change the temperature of the chuck top, the other parts of the prober chuck including the surface of the chuck top are brought into the temperature of the heater or the cooling mechanism by heat conduction. It changes to approach. It has been considered that the metal member used and the insulating material are high thermal conductive materials having good thermal conductivity, and the constituent members are at a uniform temperature.

  However, even in the case of a high thermal conductivity material, in practice, a certain temperature difference occurs between the side closer to the heater or the cooling mechanism and the side farther away. For example, when the cooling mechanism is provided in the metal spacer 22 in the prober chuck of FIG. 2, the thickness of the metal spacer 22 increases to some extent. With such a structure, when the heater 23 disposed below the metal spacer 22 is heated to raise the temperature of the metal spacer 22, a temperature difference occurs between the upper and lower surfaces of the metal spacer 22. When such a temperature difference occurs, as shown in FIG. 3A, the amount of thermal expansion between the upper and lower surfaces of the metal spacer 22 is different, and the metal spacer 22 is warped.

  The temperature of the insulating chuck top 21 changes due to heat conduction from the metal spacer 22, but similarly, a temperature difference occurs between the upper and lower surfaces, and the insulating chuck top 21 warps as shown in FIG. Arise.

  As shown in FIGS. 3A and 3B, when one or both of the insulating chuck top 21 and the metal spacer 22 are warped, an air layer is formed between them. When such an air layer is generated, it is considered that in this air layer, air is violated by heat and a noise current is generated, which increases a leakage current.

  By forming a conductive layer on the surface of the insulating member in contact with the metal member, even if an air layer is generated between them and the air is violated, the air layer has the same potential as the conductive layer of the metal member and the insulating member. It is thought that it will not affect the outside.

  Note that the upper surface conductive layer and the lower surface conductive layer of the insulating member must be insulated from each other.

  In the structure of FIG. 1, a guard layer 12A made of a conductive material is formed on the lower surface of the insulating member 12, but no conductive layer is provided on the upper surface of the insulating member 12 in contact with the metal chuck top 11. This is because there is a guard layer 12A and the metal chuck top 11 is present on the upper surface of the insulating member 12, so that it has been considered that no further conductive layer is required.

  In the structure of FIG. 2, the conductive layer 21 </ b> A is formed on the upper surface of the insulating chuck top 21, but the conductive layer is not provided on the lower surface of the insulating member 12 in contact with the metal spacer 22. The conductive layer 21A is a conductive layer for defining the potential of the back surface of the wafer to be placed. This is because it has been considered that there is no need to provide a conductive layer because the metal spacer 22 exists on the lower surface of the insulating chuck top 21 to form a guard layer.

  As described above, the present invention has been obtained with a different idea by investigating a cause that has not been considered at all.

  The conductive layer provided on the member made of an insulating material is preferably formed by plating or ion plating capable of making the coating thickness uniform.

  The insulating member is preferably made of an oxidation-based high-purity alumina ceramic that maintains high insulation even at high temperatures.

  In order to suppress the leakage current on the side surface, it is desirable to further include a conductive guard ring that covers the side surface of the prober chuck in a ring shape, is connected to the conductive surface of the back plate, and is insulated from the chuck top. . It has been confirmed that by providing the conductive guard ring, the guard layer on the lower surface of the insulating layer has an effect of suppressing the leakage current even if there is no surface conductive layer of the back plate.

  According to the present invention, even if a low-cost prober chuck with a simple structure is used, the leak current can be reduced and high-precision measurement can be performed.

  FIG. 4 is a diagram showing the configuration of the prober chuck according to the first embodiment of the present invention. The prober chuck of the first embodiment has a conductive chuck top 31, an insulating member 32, a back plate 34, and a heater 33. A conductive material guard layer 32B is formed on the lower surface of the insulating member 32. Is formed. The above configuration is the same as the conventional example of FIG. The prober chuck of the first embodiment is different from the configuration of FIG. 1 in that a conductive layer 32A is formed on the upper surface of the insulating member 32 and a guard ring 35 is provided on the side surface. The conductive layer 32A is insulated from the guard layer 32B. A cooling mechanism may be provided.

  FIG. 5 is a diagram for explaining the effect of the conductive layer 32A. As shown in FIG. 3, when the prober chuck is heated to a high temperature or a low temperature, the conductive chuck top 31 and the insulating member 32 are warped, and the upper surfaces of the conductive chuck top 31 and the insulating member 32 are shown in FIG. That is, an air layer is formed between the conductive layers 32A. The air in the air layer is violated by a temperature change and generates a minute current. However, since the conductive chuck top 31 and the conductive layer 32A are in contact with each other and have the same potential, even if the air in the air layer between the electrodes having the same potential is violated, noise current and leakage current are not generated. Does not affect the measurement.

  The conductive layer 32A and the guard layer 32B are formed by plating or ion plating that can make the coating thickness uniform.

  It is desirable that the insulating member is made of high-purity alumina ceramic that maintains high insulation even at high temperatures. Since the carbonized ceramic material has low insulation resistance, it is not suitable for the prober chuck of this embodiment. Zirconia, mullite and the like have a high heat insulation effect, but are not suitable because of large thermal strain and poor temperature change characteristics.

  The guard ring 35 is made of metal and is connected to the back plate 14. Therefore, the guard ring 35 extends to the side surface of the conductive chuck top 31 so as not to contact the conductive chuck top 31, and noise and leakage current are suppressed by applying the same potential as the conductive chuck top 31. it can.

  FIG. 6 is a diagram showing a configuration of a prober chuck according to a second embodiment of the present invention. The prober chuck of the second embodiment includes an insulating chuck top 41 having a conductive layer 41A on the surface, a metal spacer 42, a back plate 44, and a heater 43. The above configuration is the same as the conventional example of FIG. The prober chuck of the second embodiment is different from the configuration of FIG. 1 in that a conductive layer 41B is formed on the lower surface of the insulating chuck top 41 and a guard ring 35 is provided on the side surface. The conductive layer 41B is insulated from the conductive layer 41A on the surface. In the second embodiment, a cooling mechanism may be provided similarly.

  Even in the prober chuck of the second embodiment, as in the first embodiment, even if the insulating chuck top 41 and the metal spacer 42 are warped and an air layer is formed, the conductive layer 41B and the metal spacer on both sides of the air layer are formed. Since 42 has the same potential, noise current and leakage current are not generated, and measurement is not affected.

  The conductive layers 41A and 41B and the insulating member are desirably configured in the same manner as in the first embodiment. The guard ring 45 is preferably configured in the same manner as in the first embodiment.

  Measurements for confirming the effect of the present invention were actually performed. In the conventional example of FIG. 2, the leakage current was 2.4 pA, but the leakage current was hardly detected in the prober chuck of the second embodiment.

  The present invention is applicable to any prober chuck that performs a highly accurate measurement with a small leakage current.

It is a figure which shows the structural example of the conventional chuck | zipper for probers. It is a figure which shows another structural example of the conventional prober chuck. It is a figure explaining the problem in the conventional prober chuck of FIG. It is a figure which shows the structural example of the probe chuck | zipper of 1st Example of this invention. It is a figure explaining the effect | action in the prober chuck | zipper of 1st Example. It is a figure which shows the structural example of the probe chuck | zipper of 2nd Example of this invention.

Explanation of symbols

31 Conductive chuck top 32 Insulating member 32A Conductive layer 32B Guard layer 33 Heater 34 Back plate 35 Guard ring

Claims (9)

A prober chuck for holding a mounted wafer,
A chuck top made of a conductive material on which the wafer is mounted;
An insulating member made of an insulating material and supporting the bottom surface of the chuck top;
A back plate provided on the lower side of the insulating member, configured to accommodate the member therein, and at least a part of the surface being conductive
The insulating member includes an upper surface conductive layer provided on the upper surface and a lower surface conductive layer provided on the lower surface,
The upper conductive layer and the lower conductive layer are insulated from each other;
The upper conductive layer is in contact with the bottom surface of the chuck top;
The prober chuck according to claim 1, wherein the lower conductive layer is in contact with a conductive surface of the back plate.   The prober chuck according to claim 1, wherein the upper surface conductive layer and the lower surface conductive layer are formed by plating or ion plating.   The prober chuck according to claim 1, wherein the insulating member is made of an oxidation-based high-purity alumina ceramic.   4. The conductive guard ring according to claim 1, further comprising a conductive guard ring that covers a side surface of the prober chuck in a ring shape, is connected to a conductive surface of the back plate, and is insulated from the chuck top. The chuck for the prober described in 1. A prober chuck for holding a mounted wafer,
A chuck top made of an insulating material on which the wafer is mounted;
A conductive member made of a conductive material and supporting the bottom surface of the chuck top;
A back plate provided on the lower side of the conductive member, configured to accommodate the member therein, and having at least a part of the surface being conductive,
The chuck top includes a lower surface conductive layer provided on a lower surface,
The prober chuck according to claim 1, wherein the lower conductive layer is in contact with a surface of the conductive member.   The prober chuck according to claim 5, wherein the chuck top includes an upper surface conductive layer provided on an upper surface.   The prober chuck according to claim 6, wherein the upper surface conductive layer and the lower surface conductive layer are formed by plating or ion plating.   The probe chuck according to any one of claims 5 to 7, wherein the chuck top is made of an oxidation-type high-purity alumina ceramic.   The prober according to claim 6, further comprising a conductive guard ring that covers a side surface of the prober chuck in a ring shape, is connected to the conductive member, and is insulated from the upper surface conductive layer of the chuck top. Chuck.

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