JP7616877B2 - Probing Equipment - Google Patents

Description

This disclosure relates to a probing device used to inspect semiconductor wafers.

There is a probing device used to inspect semiconductor wafers (hereinafter simply referred to as wafers). The probing device is equipped with a probe card equipped with a probe for electrically inspecting semiconductor chips (hereinafter simply referred to as chips) on the wafer. The probe card is also equipped with an optical system that can acquire an image of the semiconductor chip using an image sensor. To inspect the wafer accurately, it is desirable to set the probe card to a predetermined temperature, and therefore a technology has been proposed that makes it possible to adjust the temperature of the probe card (see Patent Document 1).

Japanese Patent Application Publication No. 4-359445

The above temperature control techniques make it difficult to adjust the temperature locally. For example, as the probe card moves, the temperature distribution on the surface becomes uneven, reducing reliability during testing.

It is desirable to provide a probing device that can improve reliability during testing.

A probing device according to an embodiment of the present disclosure includes a substrate, a probe card having a probe provided on the underside of the substrate and used for electrical inspection of the semiconductor wafer , and an optical system provided in the center of the substrate and used for acquiring an image of the semiconductor wafer , a temperature adjustment mechanism attached to the probe card and having a structure divided into a plurality of divided regions in a plane so as to enable local temperature adjustment, and a temperature controller that controls the temperature of each of the plurality of divided regions in the temperature adjustment mechanism. The temperature controller controls the temperature of each of the plurality of divided regions to a predetermined set temperature so as to suppress temperature changes between the plurality of divided regions and to achieve a desired positional accuracy in the height direction between the semiconductor wafer and the optical system.

In a probing device according to one embodiment of the present disclosure, localized temperature control is possible using a temperature control mechanism having a structure divided into multiple divided regions.

FIG. 11 is an explanatory diagram showing an example of a measurement sequence by a prober according to a comparative example. 11 is a flowchart showing an example of a measurement sequence by a prober according to a comparative example. 11 is an explanatory diagram showing an example of the relationship between the preheat time at the center of the wafer by a prober according to a comparative example and the imaging performance at the outer periphery of the wafer. FIG. 1 is a cross-sectional view showing a configuration example of a probing device according to a first embodiment; 3 is a plan view showing an example of an in-plane structure of a temperature adjustment mechanism in the probing device according to the first embodiment; FIG. 2 is a circuit diagram showing an example of a circuit configuration of a control system of the probing device according to the first embodiment; 10 is an explanatory diagram showing an example of a temperature state of a probe card caused by a positional relationship with a wafer; FIG. FIG. 4 is an explanatory diagram showing an example of division of a temperature adjustment mechanism. 11 is an explanatory diagram showing an example of an in-plane temperature difference of a probe card when the temperature adjustment mechanism is not divided. FIG. 11 is an explanatory diagram showing an example of an in-plane temperature difference of a probe card when a temperature adjustment mechanism is divided. FIG. 1A and 1B are explanatory diagrams showing examples of in-plane distributions of MTFs of images obtained by image sensors in a non-division method and a division method, respectively. 5 is a flowchart showing an example of a flow of a control operation for temperature adjustment in the probing device according to the first embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order.
0. Comparative Example (FIGS. 1 to 3)
1. First embodiment (FIGS. 4 to 12)
1.1 Configuration 1.2 Operation 1.3 Effects 2. Other embodiments

<0. Comparative Example>
(Overview and Problems of the Probing Device According to the Comparative Example)
As one of the semiconductor inspection devices, there is a prober that performs wafer inspection using a probing device. An optical system is mounted on the probe card of the probing device. In the prober, an image of the wafer is captured by an image sensor using an optical system such as a light source and a lens, and wafer-level evaluation is performed. Here, since the wafer becomes a heat source and moves at high and low temperatures, the in-plane temperature of the probe card changes depending on the positional relationship between the wafer and the probe card, and distortion occurs. In addition, since the wafer, which is a heat source, moves, the amount of distortion changes from moment to moment. As a result, the positional accuracy of the optical system mounted on the probe card and the wafer changes from moment to moment, for example, within 15 μm, and the focus of the acquired image and distance measurement errors occur. For the above reasons, it has been considered difficult to perform imaging evaluation and distance measurement evaluation at the wafer level at high and low temperatures.

On the other hand, Patent Document 1 (JP Patent Publication 4-359445A) proposes a technology that allows the temperature of a probe card to be adjusted in order to set the probe card to a predetermined temperature. In the technology described in Patent Document 1, the temperature of a certain point on the probe card is detected by a temperature sensor, and the temperature of the probe card is controlled based on the detection result by a temperature variable part that is uniformly (without division) arranged on the surface of the probe card. In the technology described in Patent Document 1, if the probe card is always on the wafer surface, it is possible to stabilize the temperature on the surface. However, if a part of the probe card is removed from the wafer surface, it is difficult to suppress the temperature change of the removed part. In contrast, in the technology disclosed herein, as described later, a temperature adjustment mechanism that allows local temperature adjustment is provided, making it possible to suppress the temperature change of the removed part even if a part of the probe card is removed from the wafer surface.

In addition, the technology described in Patent Document 1 does not take measures against electromagnetic noise that occurs when the heater of the temperature adjustment mechanism is turned on and off, and is insufficient when performing inspections using, for example, an ultra-low noise image sensor.

As a method for making the focus shift uniform across the wafer, it is possible to use the function of the prober to measure the height of the probe needle tip of the probe card and make the amount of needle pressing into the chip constant. In this case, the temperature of the probe card changes when the height of the probe needle tip is measured, which is not effective. Therefore, it is considered that it is sufficient if the probe card can maintain a state where the focus is adjusted at the center of the wafer when measuring any chip. For example, as shown in Figure 1, a method is considered in which the probe card returns to the center of the wafer 100 for each chip 101A to be measured, warms up the probe card (contact preheat), and then moves it to the chip 101A to be measured. Figure 2 is a flowchart showing an example of a measurement sequence by the prober in this case.

First, the prober moves the probe card to the center of the wafer 100 and performs contact preheating on the central chip 101C (step S11). Next, the prober adjusts the focus on the central chip 101C (step S12). Next, the prober performs contact preheating on the central chip 101C (step S13). Next, the prober moves the probe card and measures the specified chip 101A (step S14).

The prober then determines whether or not the measurement of the specified number of chips has been completed (step S15). If it determines that the measurement of the specified number of chips has not been completed (step S15; N), the prober returns to the process of step S13. If it determines that the measurement of the specified number of chips has been completed (step S15; Y), the prober then moves the probe card to the central chip 101C (step S16).

Figure 3 shows an example of the relationship between the preheat time at the center of the wafer and the imaging performance at the periphery of the wafer when using a prober according to a comparative example that performs the measurement sequence described above. The longer the preheat time is, the more the imaging performance (focus deviation) tends to improve. If the preheat time is 10 minutes, the time required to evaluate one wafer containing, for example, 1000 chips, is 10 minutes x 1000 chips = approximately 7 days, which is not within a realistic evaluation time. The evaluation is required to be completed within 8 hours at most.

In response to this, the technology disclosed herein provides a temperature adjustment mechanism capable of localized temperature adjustment, as described below, making it possible to improve reliability during wafer inspection while avoiding any impact on measurement time.

1. First embodiment
[1.1 Configuration]
Fig. 4 shows an example of the configuration of the probing device according to the first embodiment. Fig. 5 shows an example of the in-plane structure of the temperature adjustment mechanism 2 in the probing device according to the first embodiment. Fig. 6 shows an example of the circuit configuration of the control system of the probing device according to the first embodiment.

The probing device according to the first embodiment includes a probe card 1, a temperature adjustment mechanism 2, and a temperature controller 3.

The probe card 1 has a substrate 10 having, for example, a multi-layer wiring structure, a probe 11 provided on the underside of the substrate 10 and connected to the wiring of the substrate 10, and an optical system 12 provided in the center of the substrate 10.

The temperature adjustment mechanism 2 is a thermostat, which is attached to the probe card 1 and has a structure divided into a plurality of divided regions 2A, 2B, 2C, and 2D within the plane as shown in FIG. 5 so as to enable localized temperature adjustment. Note that FIG. 5 shows a structure divided into four divided regions 2A, 2B, 2C, and 2D as the plurality of divided regions, but the structure may be divided into two, three, five or more divided regions.

The temperature adjustment mechanism 2 has a heater 20 (20A, 20B, 20C, 20D) that has a structure divided into multiple divided regions 2A, 2B, 2C, 2D within its surface.

The temperature adjustment mechanism 2 is attached to the underside of the substrate 10 of the probe card 1, for example, by adhesive and very low head screws 13. The temperature adjustment mechanism 2 is attached to an area of the probe card 1 other than the area where the probe 11 and the optical system 12 are provided. The temperature adjustment mechanism 2 may be provided within the substrate 10.

The heaters 20 (20A, 20B, 20C, 20D) are, for example, silicon rubber heaters. The heaters 20 (20A, 20B, 20C, 20D) are attached to the underside of the substrate 10 of the probe card 1 via a highly thermally conductive sheet 22, which is a highly thermally conductive material. The highly thermally conductive sheet 22 is, for example, an electrically insulating type highly thermally conductive material. This reduces the in-plane thermal resistance between the heaters 20 (20A, 20B, 20C, 20D) and the probe card 1.

The surface of the heater 20 (20A, 20B, 20C, 20D) opposite to the surface attached to the probe card 1 is covered with a heat insulating material 23. This increases the thermal resistance between the heater 20 (20A, 20B, 20C, 20D) and the surrounding atmosphere.

The temperature adjustment mechanism 2 has thermocouples 21 (21A, 21B, 21C, 21D). The thermocouples 21 (21A, 21B, 21C, 21D) are temperature sensors that detect the temperature in each of the multiple divided areas 2A, 2B, 2C, 2D of the heater 20 (20A, 20B, 20C, 20D). The thermocouples 21 (21A, 21B, 21C, 21D) feed back the surface temperature of the probe card 1 to the temperature controller 3 (3A, 3B, 3C, 3D), making it possible for the temperature controller 3 (3A, 3B, 3C, 3D) to control the temperature.

The temperature of each of the multiple divided regions 2A, 2B, 2C, and 2D in the temperature adjustment mechanism 2 can be adjusted by being driven by an AC voltage from, for example, an AC power source 30 (Figure 6).

The temperature controller 3 (3A, 3B, 3C, 3D) controls the temperature of each of the multiple divided regions 2A, 2B, 2C, 2D in the temperature adjustment mechanism 2. As shown in FIG. 6, the control circuit of the temperature adjustment mechanism 2 has an AC power supply 30, a fuse 31, and a switch SW.

The temperature controller 3 (3A, 3B, 3C, 3D) controls the temperature by driving each of the multiple divided regions 2A, 2B, 2C, 2D in the temperature adjustment mechanism 2 on/off with an AC voltage. As described below, the temperature controller 3 (3A, 3B, 3C, 3D) controls the on/off driving of each of the multiple divided regions 2A, 2B, 2C, 2D at the timing when the AC voltage reaches the zero cross point.

With the above structure, it is possible to achieve maximum temperature characteristics within a limited space, even if the distance from the underside of the probe card 1 to the wafer 100 is, for example, about 4 mm.

(Example of temperature characteristics)
FIG. 7 shows an example of the temperature state of the probe card 1 caused by the positional relationship with the wafer 100. In FIG.

As shown in FIG. 7, when a part of the probe card 1 is removed from the surface of the wafer 100, the part of the probe card 1 that is on the surface of the wafer 100 is heated by heat from the wafer 100, while the part that is not on the surface of the wafer 100 is cooled by convection and radiation. The temperature adjustment mechanism 2 has a divided structure so that it is possible to suppress temperature changes in such parts that are not on the surface of the wafer 100.

Figure 8 shows an example of division of the temperature adjustment mechanism 2. Figure 8 shows the difference in structure between when the temperature adjustment mechanism 2 is not divided (non-divided method) and when it is divided (divided method). The sense point refers to the point where the temperature is detected by the thermocouples 21 (21A, 21B, 21C, 21D).

Figure 9 shows an example of the temperature difference within the surface of the probe card 1 when the temperature adjustment mechanism 2 is not divided. Figure 10 shows an example of the temperature difference within the surface of the probe card 1 when the temperature adjustment mechanism 2 is divided.

As shown in FIG. 9, if the temperature adjustment mechanism 2 has a non-split structure, the temperature of the probe card 1 in the part outside the upper surface of the wafer 100 is, for example, 60°C, and the temperature of the probe card 1 in the upper surface of the wafer 100 is, for example, 70°C, and there is an in-plane temperature difference in the probe card 1. In contrast, as shown in FIG. 10, if the temperature adjustment mechanism 2 has a split structure, it is possible to adjust the temperature of the part outside the upper surface of the wafer 100 and the part above the surface of the wafer 100 to, for example, 60°C.

Figure 11 shows an example of the in-plane distribution (out-of-focus) of the MTF of an image obtained by an image sensor in each of the non-split method (Figures 8 and 9) and split method (Figures 8 and 10) described above.

As shown in FIG. 11, the in-plane tendency of focus deviation was significantly improved by stabilizing the in-plane temperature of the probe card 1 using the split method. When the MTF is converted to physical length, the positional relationship in the height direction between the optical system 12 and the wafer 100 has an accuracy of, for example, 15 μm in the case of the non-split method and an accuracy of, for example, 7.5 μm in the case of the split method. In this way, the probing device according to the first embodiment employs a split method as the structure of the temperature adjustment mechanism 2, making it possible to perform imaging evaluation and distance measurement evaluation at the wafer level at high and low temperatures.

On the other hand, a side effect of temperature adjustment by the temperature adjustment mechanism 2 is that, because the temperature adjustment mechanism 2 and the wafer 100 are located in close proximity to each other at a distance of several mm, electromagnetic noise generated by the temperature adjustment mechanism 2 is released into space and reaches the wafer 100, possibly affecting measurements by the image sensor. For example, switching noise from the switch SW (Figure 6) for controlling the on/off of the heaters 20 (20A, 20B, 20C, 20D) may be released into space as electromagnetic noise.

As a countermeasure against noise, the temperature controller 3 (3A, 3B, 3C, 3D) monitors the AC voltage of the AC power supply 30, and controls the heaters 20 (20A, 20B, 20C, 20D) to turn on/off when the AC voltage crosses 0V (zero cross point), that is, when the voltage sign is reversed from positive to negative. This makes it possible to suppress the generation of electromagnetic noise, and to reduce the voltage noise level in the image captured by the image sensor, for example, from several tens of μV to several μV.

1.2 Operation
FIG. 12 is a flowchart showing an example of the flow of a control operation for temperature adjustment in the probing device according to the first embodiment.

First, the temperature controller 3 judges whether the temperature detected by the thermocouple 21 is less than the set temperature (step S21). If it is judged that the detected temperature is not less than the set temperature (step S21; N), the temperature controller 3 repeats the process of step S21. If it is judged that the detected temperature is the set temperature (step S21; Y), the temperature controller 3 then judges whether the AC voltage is at the zero cross point (step S22). If it is judged that the AC voltage is not at the zero cross point (step S22; N), the temperature controller 3 repeats the process of step S22. If it is judged that the AC voltage is at the zero cross point (step S22; Y), the temperature controller 3 then turns on the heater 20 (step S23).

Next, the temperature controller 3 judges whether the temperature detected by the thermocouple 21 is equal to or higher than the set temperature (step S24). If it is judged that the detected temperature is not equal to or higher than the set temperature (step S24; N), the temperature controller 3 repeats the process of step S24. If it is judged that the detected temperature is equal to or higher than the set temperature (step S24; Y), the temperature controller 3 next judges whether the AC voltage is at a zero cross point (step S25). If it is judged that the AC voltage is not at a zero cross point (step S25; N), the temperature controller 3 repeats the process of step S25. If it is judged that the AC voltage is at a zero cross point (step S25; Y), the temperature controller 3 next turns off the heater 20 (step S26).

Next, the temperature controller 3 judges whether or not there is a control stop command from, for example, a higher-level system (step S27). If it is judged that there is no control stop command (step S27; N), the temperature controller 3 returns to the process of step S21. If it is judged that there is a control stop command (step S27; Y), the temperature controller 3 ends the control process.

[1.3 Effects]
As described above, according to the probing device of the first embodiment, local temperature control is made possible by the temperature control mechanism 2 having a structure divided into a plurality of divided regions 2A, 2B, 2C, and 2D, thereby making it possible to improve reliability during inspection.

According to the probing device of the first embodiment, the surface temperature of the probe card 1 is kept constant by the temperature adjustment mechanism 2 with a split structure, thereby suppressing distortion of the probe card 1 when the temperature changes, and the positional accuracy in the height direction between the optical system 12 mounted on the probe card 1 and the wafer 100 can be improved from, for example, 15 μm to 7.5 μm. This makes it possible to perform imaging evaluation and distance measurement evaluation at the wafer level at high and low temperatures.

In addition, according to the probing device of the first embodiment, the timing of turning on/off the heater 20 of the temperature adjustment mechanism 2 is synchronized with the zero crossing point of the AC voltage, which suppresses the generation of switching noise when turning the heater 20 on/off, and makes it possible to reduce the voltage noise level in the image captured by the image sensor from, for example, several tens of μV to several μV.

The effects described in this specification are merely examples and are not limiting, and other effects may also be present. The same applies to the effects of other embodiments described below.

2. Other embodiments
The technology according to the present disclosure is not limited to the above-described embodiment, and various modifications are possible.

For example, the present technology can be configured as follows.
According to the present technology having the following configuration, local temperature adjustment is made possible by a temperature adjustment mechanism having a structure divided into a plurality of divided regions, thereby making it possible to improve reliability during inspection.

(1)
a probe card including a substrate, a probe provided on a lower surface of the substrate, and an optical system provided in the center of the substrate;
a temperature adjustment mechanism attached to the probe card and having a structure divided into a plurality of divided regions in a plane so as to enable local temperature adjustment;
a temperature controller that controls a temperature of each of the divided regions in the temperature adjustment mechanism.
(2)
The temperature adjustment mechanism includes:
a heater having a structure divided into the plurality of divided regions within a plane;
and a plurality of temperature sensors for detecting temperatures in the plurality of divided regions of the heater.
(3)
the temperature of each of the divided regions of the temperature adjustment mechanism can be adjusted by being driven by an AC voltage;
The temperature controller controls the temperature by driving each of the plurality of divided regions in the temperature adjustment mechanism on/off with the AC voltage, and the timing for driving each of the plurality of divided regions on/off is set to coincide with the timing at which the AC voltage reaches a zero cross point.
(4)
The probing device according to any one of (1) to (3) above, wherein the temperature adjustment mechanism is attached to a lower surface of the substrate in the probe card.
(5)
The probing device according to (2) above, wherein the heater is attached to the lower surface of the substrate of the probe card via a highly thermally conductive material.
(6)
The probing device according to (5) above, wherein a surface of the heater opposite to a surface thereof that is attached to the probe card is covered with a heat insulating material.
(7)
The probing device according to any one of (1) to (6) above, wherein the temperature adjustment mechanism has four divided regions as the plurality of divided regions.
(8)
The probing device according to any one of (1) to (7) above, wherein the temperature adjustment mechanism is attached to an area of the probe card other than an area in which the probe and the optical system are provided.

1...probe card, 2...temperature control mechanism (thermostat), 2A, 2B, 2C, 2D...division areas, 3 (3A, 3B, 3C, 3D)...temperature controller, 10...substrate, 11...probe, 12...optical system, 13...ultra-low head screw, 20 (20A, 20B, 20C, 20D)...heater (silicon rubber heater), 21 (21A, 21B, 21C, 21D)...thermocouple (temperature sensor), 22...highly thermally conductive sheet (highly thermally conductive material), 23...insulation material, 30...AC power source, 31...fuse, 100...wafer (semiconductor wafer), 101A...chip (semiconductor chip), 101C...central chip (semiconductor chip), SW...switch.

Claims (8)

a probe card including a substrate, a probe provided on a lower surface of the substrate and used for electrical inspection of the semiconductor wafer , and an optical system provided in the center of the substrate and used for acquiring an image of the semiconductor wafer ;
a temperature adjustment mechanism attached to the probe card and having a structure divided into a plurality of divided regions in a plane so as to enable local temperature adjustment;
a temperature controller for controlling the temperature of each of the plurality of divided regions in the temperature adjustment mechanism ,
The temperature controller controls the temperature of each of the plurality of divided regions to a predetermined set temperature so as to suppress a temperature change between the plurality of divided regions and to obtain a desired positional accuracy in the height direction between the semiconductor wafer and the optical system.
Probing equipment. The temperature adjustment mechanism includes:
a heater having a structure divided into the plurality of divided regions within a plane;
a plurality of temperature sensors for detecting temperatures in the plurality of divided regions of the heater ,
The temperature controller controls the temperature of each of the plurality of divided regions to the predetermined set temperature by turning on the heater of the divided region where the temperature detected by the temperature sensor is lower than the predetermined set temperature and by turning off the heater of the divided region where the temperature detected by the temperature sensor is equal to or higher than the predetermined set temperature.
2. The probing device of claim 1. the temperature of each of the divided regions of the temperature adjustment mechanism can be adjusted by being driven by an AC voltage;
2. The probing device according to claim 1, wherein the temperature controller controls the temperature by driving each of the plurality of divided regions in the temperature adjustment mechanism on/off with the AC voltage, and the timing for driving each of the plurality of divided regions on/off is set to coincide with a zero cross point of the AC voltage. The probing device according to claim 1 , wherein the temperature adjustment mechanism is attached to a lower surface of the substrate in the probe card. The probing device according to claim 2 , wherein the heater is attached to the lower surface of the substrate of the probe card via a highly thermally conductive material. 6. The probing device according to claim 5, wherein a surface of the heater opposite to a surface to be attached to the probe card is covered with a heat insulating material. The probing device according to claim 1 , wherein the temperature adjustment mechanism has four divided regions as the plurality of divided regions. The probing device according to claim 1 , wherein the temperature adjustment mechanism is attached to an area of the probe card other than an area where the probe and the optical system are provided.

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