DE102005015334A1 - Prober for testing substrate of e.g. semiconductor chip, has chuck with retaining surface to retain and cool substrate and fixed on carrier such that it is thermally uncoupled from another chuck and connected to cold head by connecting unit - Google Patents

Abstract

The prober has a chuck (5) that is moved between a retaining area and a working area by a drive and includes holding unit to fix a substrate carrier. A chuck (6) with a retaining surface for retaining and cooling a test substrate is fixed on the carrier in such a manner that the chuck (6) is thermally uncoupled from the chuck (5) and connected with a cold head (23) of a refrigerator (24) by a good heat conducting connecting unit (22).

Description

The This invention relates to a sampler for testing substrates at temperatures in the range of the boiling temperature of helium with a chuck, whereby the Chuck by means of a Chuck drive between a recording and a working area in the prober and thermally moved by the Chuck drive is decoupled and holding means for fixing a comprising a test substrate receiving substrate carrier.

The exam of electronic components, such as semiconductor chips, hybrid components, Micromechanical components or the like, on their reliability takes place in Probern primarily under the environmental conditions, which correspond to the conditions of use of the respective component, or under such environmental conditions, which has the least disturbance of the Signal behavior during The examination cause. One focus is the measurement of components at low temperatures, especially in the boiling temperature range of nitrogen and below. For example, the functional test of highly sensitive optical sensors or superconducting transistors at lows, that is up to the order of magnitude of only a few Kelvin, the range of the boiling point of helium.

In German Offenlegungsschrift 102 46 282 a Prober is described, the for testing of various components at low temperatures is used. The components to be tested (test substrate) are cooled in this sampler under vacuum conditions by working with a substrate receptacle, a chuck, brought into good thermal contact and the chuck cooled directly becomes. For cooling of the chuck it is traversed by a coolant and at the same time from the environment and the adjacent components by a likewise directly cooled Heat radiation shield and by appropriate material selection for the parts, which a heat transfer represent, thermally decoupled.

to Recording a test substrate will also be the chuck of one Work area moved into a receiving area, so that both a variety of types of test substrates are receivable, that is, the feeds not limited to magazines stored, similar test substrates are limited and Nevertheless, the Prober for substrate change are not fully opened has to, what a lot of cooling time and Energy saves.

The Achievable with this Prober low temperature is due to the coolant limited, which for cooling the chuck is used. Because the chuck is moving in the workspace of the prober after recording a test substrate and for positioning of the device relative to the probe needles with which the loading and the tapping of the signals on the device takes place in a relative huge Area must be movable, is for its cooling a relatively large coolant circuit with as possible flexible coolant lines required.

Especially because of this great Cooling circuit is the use of liquid Helium as a coolant however excluded so that the described prober is for use at cryogenic temperatures can not be used. The reason for this is to one in the big one Evaporation amount of helium from the big circle and the size as well Number of cooling with it Components results. On the other hand, for cost reasons and because of limited availability helium requires the creation of a closed helium cycle, which in turn with such a large refrigeration cycle a high technical equipment Effort and to a significant restriction of the mobility of the Chucks brings.

Furthermore is due to the temperature difference between one at helium temperature cooled Chuck and the minimum at nitrogen temperature coolable surrounding components as well as due to the relatively large surfaces this chuck the heat entry by heat radiation so big that the test substrate is not on the boiling point of helium cooled but is an equilibrium temperature well above 4 Kelvin established. An inclusion of the heat radiation shield in the Cooling circuit of helium to reduce the heat input from the surrounding However, because of the associated enormous increase in the Circulatory excluded.

Also the flexibility the coolant lines is at cryogenic temperatures so reduced that the mobility of the Chucks clearly limited is. But just in this temperature range is the method of Chucks from a receptionist to a workspace especially cost saving, as with decreasing temperature significantly longer cooling times and more energy for cooling are required and therefore the case of a change of the test substrate components exposed to warm environment should be minimized.

Thus, the invention has the object to represent a Prober, with which with minimum coolant requirements in particular Helium is the universal testing of a variety of test substrates up to a temperature in the range of the boiling point of helium and at the same time the mobility of the substrate recording from a recording into a working area is possible.

According to the invention Task solved by that the Prober a chiller (Refrigerator) with a cold head (cold heat) that has on the substrate carrier a second chuck with a second receiving surface for receiving and cooling a Test substrate is fixed such that the second chuck thermally is decoupled from the first chuck and that the second chuck over well thermally conductive Connecting means is connected to the cold head.

The Using a second chuck, which between the substrate carrier and otherwise usually directly on the substrate carrier inserted fixed test substrate is, together with the use of a refrigerator, which their Cool the cold head to a few Kelvin can, and by means of the good heat-conducting Connecting means, for example, made of copper, good thermal connection of the cold head only with the second and not with the first chuck, allowing the minimization of energy and the coolant expense while maintaining the mobility of the first chuck by means of his Chuck drive, especially for the process of the first and thus also the second chuck between the working position where the actual measurement takes place and the Recording position, where the change or placement of the first chuck with the second chuck and test substrate having, substrate carrier carried out can.

As a result the thermal decoupling of the second chuck from the first chuck is only the second chuck and no further component on the exact Test temperature to cool and to stabilize this temperature, so that the stability and the Reproducibility of the test temperature are significantly improved. About that In addition, the second chuck can be very flexible in its size and shape respective test substrate to be adjusted, without regard to the first chuck existing mechanical and thermal interfaces. The adaptation the second chuck to these seams by means of a changing to be designed substrate carrier. To realize the thermal decoupling, the substrate carrier is preferably from a bad heat-conducting Made of plastic, making it a very reasonably priced and mainly represents variable to be designed component.

Provided according to a further, particularly advantageous embodiment the invention of the second Chuck solvable on the substrate carrier is fixed, the optimization of the shape and size of the second Chucks further improved with respect to the test substrate and thus the time and energy required to set the test temperature and the coolant requirement further reduced. About that In addition, a substrate carrier be equipped to record different, second chucks can, if necessary, only the second chuck and not more of the entire substrate carrier must be exchanged when changing the test substrate.

by virtue of the task of making the substrate holder movable, it is necessary the connecting means between cold head and second Chuck to shape the movement of the second chuck can follow. This can be done, for example, by using it in several sections subdivided connecting means be realized, wherein the individual Sections with joints or comparable, movable pontics connected to each other.

Regarding the Freedom of movement of the second chuck, it has to be particularly advantageous proved that the connecting means flexible and / or detachable with connected to the second chuck. Are they flexible, for example from wires or ribbons, can they follow immediately the movement of the chuck, whereby their length and Arrangement variable to be carried out Travel to the precise Measuring position are to be adjusted. Are the connecting means detachable with connected to the second chuck, the substrate holder can proceed as required and are positioned and then carried out only the production the connection with the second chuck for the purpose of cooling it. Of course it is also the combination of both design options executable, so that, for example, the larger distances for pre-positioning with separate connection between connecting means and second Chuck overcome and then the fine positioning takes place when the connection is made.

Provided the connecting means are detachable from the chuck, the inventive arrangement allows a second, the test substrate receiving Chucks on the substrate carrier, that on the substrate carrier at least a third chuck in the shape of the second chuck accomplished is, is fixable. In this way, the substrate carrier in a sequence equipped with several test substrates be successively after loosening the connecting means means drove the Chuck drive in their respective measurement position, there thermally connected to the cold head of the refrigerator and after the temperature setting checked can be.

Likewise, it proves to be useful that the connecting means in addition to their detachable connection on the second chuck also releasable with the cold head are connected. This allows the change of the connecting means, for example because of changing requirements in terms of flexibility or length, and also their disassembly for repair and cleaning purposes. If the prober is to be operated at temperatures for which the refrigerator is not required, it may also be advantageous to remove the connecting means.

Corresponding a particularly favorable embodiment the invention is the contacting of the test substrate for the signal application and / or the signal tap instead of using contact pins by wire bridges. The jumpers are able to absorb vibrations from the refrigerator the test arrangement are transmitted or displacements due to different expansion behavior of different materials during the cooling process compensate. Execution the wire bridges can because of the detachable Fixation of the substrate carrier on the first chuck and the arrangement of the test substrate by means of the second chuck on the substrate carrier in particularly favorable Way also outside of Probers done without requiring a full opening of the test room is required.

Because of the described reduction of cooling to cryogenic temperatures Components and optimization of their volumes, allows the prober invention a targeted and therefore particularly effective shielding of this Components before heat radiation the environment. Therefore, an advantageous embodiment of the Invention that the connecting means between the cold head and the second chuck are thermally shielded by the entire Connection from a first heat radiation shield is surrounded. Therefore is the heat radiation shield in such a way that both the connection means themselves, regardless of their design, as well as the Kotakte the cold head and the second Chuck from the heat radiation shield across from the warmer Environment are shielded. conveniently, also the cold head can be surrounded by the first heat radiation shield is, resulting in a significant reduction of the refrigerator applied cooling effort leads.

Provided a second heat radiation shield at least arranged around the area of the second chuck, which is the heat input in the second chuck and thus in the test substrate by thermal radiation minimized, can the effectiveness the cooling continues be improved. With a good thermal decoupling of the second Chuck from the first chuck is such a small one, just surrounding the second chuck second heat radiation shield sufficient, however, several second chucks are arranged on the substrate carrier be or other components are cooled on the substrate carrier can this heat radiation shield also the entire substrate carrier, including shield the first chuck.

The same, energy-saving effect has that embodiment of the invention, in which the refrigerator surrounded by a third heat radiation shield is. First, the warming the cold components of the second, cooling on helium temperature Stage of the refrigerator reduced by the ambient radiation. On the other hand, the radiation of the opposite is clear warmer parts the first stage of the chiller shielded, in which preferably liquid nitrogen as the refrigerant serves.

By doing according to further embodiments of the invention one, two or all three heat shields at least for an initial period of cooling directly cooled and optionally at least the cooling of the first and the second Thermal radiation shield by means of the refrigerator independent cold source takes place, reaching the test temperature is much faster possible. The direct cooling takes place preferably by means of flow or flow around the Shields with a coolant until the time the shield reaches the coolant temperature Has. The exam is done of the test substrate at a temperature which is in the range of the coolant temperature is, for example, the liquid Nitrogen, a permanent cooling of the shields can be done. But if temperatures are to be set below the coolant temperature, in particular, of some Kelvin, would further cooling the Shields do exactly the opposite, and the shields are called continuous heat source across from the colder Test substrate and the other colder Act components.

A thermal connection of the first with the second heat radiation shield causes a uniform temperature regime for the shields of the connecting means and the second chuck and leads thus stabilizing and accelerating the cooling process. This effect occurs in particular when, moreover also the first and the third heat radiation shield thermally connected, since in this case the usually of Refrigerator with refrigerated third heat radiation shield from the other shields with cooled becomes.

A further, particularly advantageous embodiment of the invention provides that the first chuck is coolable and / or heatable. In this way, a conversion of the Probers on the test operation at higher, that is achievable by direct cooling by means of a coolant temperatures very quickly and easily possible. For this purpose, a test substrate may be arranged on the substrate carrier in the known manner so that it is in good heat Mekontakt to the first chuck is and is cooled by this. The second chuck is, like the refrigerator, not needed in this case or, if it is detachably mounted, not arranged on the substrate carrier. In this way, the range of application of the tester according to the invention, depending on the coolant used for cooling the first chuck can be significantly expanded, practically up to room temperatures, without any special modifications are required. In addition, by means of the heating of the first chuck, any temperature, irrespective of the coolant temperature, can be set and also the heating process of the cooled chuck can be accelerated, for example, for a change of the test arrangement.

By doing in a special version the invention the directly and indirectly cooled parts of both chucks, the refrigerator, the connecting means and the heat radiation shields made of good thermally conductive material exist and the cooled Parts of the Chucks have highly reflective surfaces, the heat exchange with the surrounding components minimized by heat radiation as well with the to be cooled Split by heat conduction optimized.

Furthermore it is useful if the substrate carrier is symmetrical, based on at least one axis of symmetry is executed. With this, for example rotationally symmetric Execution can for a thermal stress during the cooling and on the other hand with central support of the substrate carrier Tilting due to uneven loading resulting from only a second chuck be prevented.

A Reduction of cooling capacity can also be achieved by such an embodiment that the substrate carrier its mass reducing recesses, thus its heat capacity is reduced, with only the stability of the substrate carrier and if necessary, its symmetry must be taken into account.

by virtue of the working principle of the refrigerator as a compressor proves it particularly advantageous when the refrigerator is mounted on a receptacle which is the vibration isolation of the refrigerator to the Prober realized. The vibration decoupling ensured compliance with the required tolerances in the test geometry, because of the orders of magnitude the contacts of the test substrates are very low. This is especially true when using contact pins too, where no firm connection between the needle tip and the test substrate.

The Invention will be explained in more detail with reference to an embodiment. The associated Drawing shows in

1 the schematic sectional view of a Probers invention and

2 the schematic representation of a substrate carrier with connecting means and first heat radiation shield in plan view.

As in 1 illustrated, the tester according to the invention for cryogenic testing a vacuum chamber, surrounded by a chamber housing 1 on, on one side a loading opening 2 with a vacuum-tight lockable flap 3 and in the middle, above the work area, an inspection opening closed by infrared radiation-reflecting quartz glass 4 includes. The vacuum chamber is connected to a vacuum unit not shown for evacuation. In the vacuum chamber is a first chuck 5 arranged, with a chuck drive 7 , preferably a motorized cross table, is connected. By means of the Chuck drive 7 is the first chuck 5 movable in the vacuum chamber.

The cylindrical first chuck 5 Made of copper with a gold coating, is over the flexible coolant line 8th with a coolant tank 33 connected and can be cooled according to the coolant used in different temperature ranges by the coolant through inside the first chuck 5 existing cannulas 9 to be led. The bottom of the first chuck 5 has a chuck heater 9 to set temperatures above the coolant temperature and the first chuck 5 for the opening of the Prober to warm to ambient temperature. The attachment of the first chuck 5 on the chuck drive 2 via an intermediate piece 11 from a glass fiber tube, which has a slightly smaller cross-section than the first chuck 5 and a wall thickness of about 1 mm.

On the flat and smooth, on top of the first chuck 5 located first receiving surface 12 is concentric a substrate carrier 13 with its base element 14 , which also consists of copper with a gold coating, placed and fixed by means not shown tensioning mechanism. The main body of the substrate carrier 13 forms a made of plastic, substantially disc-shaped insulating 15 , which several, to the base element 14 spaced first recesses 16 having. In one of the first recesses 16 is a second chuck 6 arranged on the flat and smooth second receiving surface 17 a test substrate 18 placed on and fixed by means not shown clamping elements.

Due to the flat support of the test substrate 18 with its also smooth and flat bottom will be a good thermal contact with the second chuck 6 produced. The electrical contacting of the test substrate 18 takes place in the present embodiment by means of wire bridges 19 , Alternatively, however, contact needles may also be used which are then preferably on the substrate carrier 13 are arranged.

The, based on the first chuck 5 , off-center in the substrate carrier 13 arranged second chuck 6 is by means of the chuck drive 7 in such a measuring position that the test substrate 18 through the lid of the chamber housing 1 arranged inspection opening 4 with a microscopy unit 20 can be observed. For changing the substrate carrier 13 may be the first chuck 5 continue in the direction of the flap 3 in the chamber housing 1 are moved to the receiving position in which the change through the loading opening 2 can be done through.

One at the bottom of the second chuck 6 trained contact element 21 is by means of connecting means 22 , which are executed sections flexible and rigid, with the cold head 23 a refrigerator 24 thermally connected. The refrigerator 24 has a first cold stage 25 on, in which liquid nitrogen serves as a refrigerant, and then a second stage of refrigeration 26 , with helium as refrigerant. The cold head 23 is through the second cold stage 26 cooled to about 4 Kelvin and via the thermal contact of the bonding agent 22 also the second chuck 6 and over this also the test substrate 18 ,

The refrigerator 24 is by a vibration-damping mounting element so on the chamber housing 1 mounted that its first and second cold stage 26 as well as the cold head 23 through an opening in the chamber housing 1 protrude into the vacuum chamber. The vibration-damping mounting element 27 prevents the from the compressor unit of the refrigerator 24 in the liquefaction of helium generated vibrations on the housing and on the chuck and the substrate carrier 13 on the test substrate 18 be transmitted.

Above the substrate carrier 13 in almost the entire chamber size and under the substrate carrier 13 in about the size of the substrate carrier 13 itself is arranged at a small distance in each case a heat radiation shield with a downward or upwardly angled annular border. These two heat radiation shields together form the second heat radiation shield according to the invention 30 , which is the shielding of the substrate carrier 13 and thus the second chuck 6 serves. The second heat radiation shield 30 is, as well as the first chuck 5 , via a not shown, flexible coolant line with a coolant tank 33 connected and is cooled by the coolant through inside the second heat shield 30 existing cannulas 9 to be led. It is made of highly thermally conductive material with a highly reflective surface. To the second heat radiation shield 30 Subsequently, in the illustrated embodiment, an additional, also directly cooled heat radiation shield 32 executed, which is the first chuck 5 shields.

The first heat radiation shield according to the invention 29 encloses the connecting means 22 between the second chuck 6 and the cold head 23 as well as the cold head 23 himself, closing the second heat radiation shield 30 at. The first heat radiation shield 29 is in thermal contact with the third heat radiation shield 31 the refrigerator 24 shielded from the surrounding components of the Prober and the first cold stage 25 of the refrigerator 24 is cooled to about 77 Kelvin.

About a not shown measuring and control unit is the test substrate for testing 18 required temperature both on the second chuck 6 as well as on the heat radiation shields 29 . 30 . 31 regulated.

The in 2 illustrated substrate carrier 13 is from the lower part of the second heat radiation shield 30 surrounded and consists essentially of a disc-shaped insulating 15 which centrally a concentrically arranged base element 14 having, with the aid of the substrate carrier 13 on the first chuck 5 can be fixed. On a circumference around the base element 14 and at a distance there are a plurality of circular first recesses 16 formed, which the mass and thus the heat capacity of the substrate carrier 13 Reduce. One of the first recesses 16 is formed such that the second chuck according to the invention 6 can be fixed by means not shown clamping means. On a perimeter around this second chuck 6 are other, circular second recesses 34 formed, which are significantly smaller than the first recesses 16 but have the same function.

The second chuck 6 has a stepped cylindrical shape and has on its underside an elongate contact element 21 on. At this contact element 21 are the lanyards 22 , consisting of copper bands 35 which are on a rigid fork 36 are attached to the thermal con timing with the cold head 23 of the refrigerator 24 connected. The copper bands 35 are dimensioned so long that the necessary travels of the second chuck 6 can be performed in existing thermal connection. The contacting of the connecting means 22 at the cold head 23 happens by a firm mounting of the fork 36 on the cold head 23 ,

The cold head 23 and the connecting means 22 are from a common, first heat radiation shield 29 surrounded, which is divided in the middle and by twisting each half around the center of the cold head 23 the connecting means 22 can expose for the preparation of the compound and then enclose again.

1

chamber housing

2

loading opening

3

flap

4

inspection opening

5

first Chuck

6

second Chuck

7

Chuck drive

8th

Coolant line

9

needles

10

Chuck Heating

11

connecting piece

12

first receiving surface

13

substrate carrier

14

base element

15

insulating

16

first recesses

17

second receiving surface

18

test substrate

19

jumpers

20

microscopy purity

21

contact element

22

connecting means

23

cold head

24

refrigerator

25

first cold stage

26

second cold stage

27

mounting element

28

compressor unit

29

first Thermal radiation shield

30

second Thermal radiation shield

31

third Thermal radiation shield

32

additional Thermal radiation shield

33

Coolant tank

34

second recess

35

copper strips

36

fork

Claims (20)

Prober for testing substrates at temperatures in the range of the boiling point of helium with a chuck, wherein the chuck is moved by a Chuck drive between a recording and a working area in the Prober and thermally decoupled from the Chuck drive and holding means for fixing a substrate receiving a test substrate, characterized in that the prober is a refrigerator (Refrigerator) ( 24 ) with a cold head (Cold Heat) ( 23 ), that on the substrate carrier ( 13 ) a second chuck ( 6 ) with a second receiving surface ( 17 ) for receiving and cooling a test substrate ( 18 ) is fixed so that the second chuck ( 6 ) thermally from the first chuck ( 5 ) is decoupled and that the second chuck ( 6 ) via highly thermally conductive connecting means ( 22 ) with the cold head ( 23 ) connected is. Prober for testing substrates according to claim 1, characterized in that the substrate carrier ( 13 ) is made of poor thermal conductivity plastic. Prober for testing substrates according to one of claims 1 or 2, characterized in that the second chuck ( 6 ) detachable on the substrate carrier ( 13 ) is fixed. Prober for testing substrates according to one of claims 1 to 3, characterized in that connecting means ( 22 ) are flexible and / or detachable with the second chuck ( 6 ) are connected. Prober for testing substrates according to one of claims 1 to 4, characterized in that on the substrate carrier ( 13 ) a third chuck in the shape of the second chuck ( 6 ) is fixable. Prober for testing substrates according to claim 4, characterized in that the connecting means ( 22 ) detachable with the cold head ( 23 ) are connected. Prober for testing substrates according to one of claims 1 to 5, characterized in that the contacting of the test substrate ( 18 ) for the signal application and / or the signal tapping by means of wire bridges ( 19 ) is executed. Prober for testing substrates according to one of claims 1 to 7, characterized in that the entire connection between cold head ( 23 ) and the second chuck ( 6 ) from a first heat radiation shield ( 29 ) are surrounded. Prober for testing substrates according to claim 8, characterized in that also the cold head ( 23 ) from the first heat radiation shield ( 29 ) is surrounded. Prober for testing substrates after egg nem of claims 1 to 9, characterized in that at least the second chuck ( 6 ) from a second heat radiation shield ( 30 ) is surrounded. Prober for testing substrates according to one of claims 1 to 10, characterized in that the refrigerator ( 24 ) from a third heat radiation shield ( 31 ) is surrounded. Prober for testing substrates according to one of claims 8 to 11, characterized in that one, two or all three thermal radiation shields ( 29 . 30 . 31 ) are cooled directly at least for an initial period of cooling. Prober for testing substrates according to claim 12, characterized in that at least the cooling of the first ( 29 ) and the second heat radiation shield ( 30 ) by means of the refrigerator ( 24 ) independent cooling source takes place. Prober for testing substrates according to one of claims 1 to 13, characterized in that the first ( 29 ) and the second heat radiation shield ( 30 ) are thermally connected. Prober for testing substrates according to one of claims 1 to 14, characterized in that also the first ( 29 ) and the third heat radiation shield ( 31 ) are thermally connected. Prober for testing substrates according to one of claims 1 to 15, characterized in that the first chuck ( 5 ) is coolable and / or heatable. Prober for testing substrates according to one of claims 1 to 16, characterized in that the directly and indirectly cooled parts of both chucks ( 5 . 6 ), the refrigerator ( 24 ), the connecting means ( 22 ) as well as the heat radiation shields ( 29 . 30 . 31 ) consist of good thermally conductive material and the cooled parts of Chucks ( 5 . 6 ) have highly reflective surfaces. Prober for testing substrates according to one of claims 1 to 17, characterized in that the substrate carrier ( 13 ) symmetrically, based on at least one axis of symmetry, is executed. Prober for testing substrates according to one of claims 1 to 18, characterized in that the substrate carrier ( 13 ) has its mass reducing recesses. Prober for testing substrates according to one of claims 1 to 19, characterized in that the refrigerator ( 24 ) is mounted on a receptacle which the vibration isolation of the refrigerator ( 24 ) to the prober.