Device for electrically testing semiconductor components

Abstract

The invention relates to a device for electrically testing semiconductor components, such as wafers (18) or chips, comprising a test head (7) with a plurality of test needles (2), in particular a test head (7) in the form of a vertical probe card (1), wherein the test needles (2) are movably guided in holes of a guide plate (5b) and protrude beyond the guide plate (5b) in the direction of the semiconductor component to be tested. A protective plate (9) is provided on the guide plate (5b) and the test needle (2) ends which protrude beyond the guide plate (5b) and have the tips (3) pass through the protective plate (9).

Description

[0001]DEVICE FOR ELECTRICALLY TESTING SEMICONDUCTOR COMPONENTS The invention relates to a device for electrically testing semiconductor components with the features of the introductory part of patent claim 1. These devices contain test heads in their probe cards, which can be designed as so-called vertical probe cards. A vertical probe card is known, for example, from AT 14209 A1. The test probes are received in guide plates and movably guided in holes relative to the lower guide plate adjacent to the semiconductor component (e.g., a chip). Vertical probe cards have a plurality of test probes, all of which engage through holes in the lower guide plate (ceramic plate) and are movably guided in these holes relative to the lower guide plate. When placed on the power semiconductor chip to be tested, they elastically deform (bend out) above the lower guide plate, so that the tips of the test probes are resiliently flexible.When testing microchips ("power chips"), very high currents are sometimes used, currently up to 3000 amperes. To ensure that these currents can be introduced into the chip without overloading the contact points to the chip under test and with the most homogeneous current distribution possible, a very large number of test probes are used, distributed almost evenly across the surface of the chip under test. With a nominal current of 1 ampere per test probe, this results in a vertical probe card with approximately 3000 test probes. If there is a defect in the chip under test (a so-called "hot spot"), very high power losses occur at certain points on the surface of the chip. Depending on the metallization material, this can cause the chip's metallization to melt and explosively splash or evaporate.This can lead to metal deposits forming on the test needles of the vertical probe card and on the lower guide plate (ceramic plate) of the test head, in which the test needles are slidably guided. If there is a defect in the chip under test (a so-called "hot spot"), high power losses occur at the defect in the chip during electrical testing. Depending on the energy input during testing of the chip and the material of the metallization in the chip, this can cause the metallization material to melt and explosively splash or vaporize. This can lead to metal deposits forming on the ends (tips) of the test needles protruding above the lower guide plate and / or on the lower guide plate (ceramic plate) of the test head, in which the test needles are slidably guided.If metal is deposited on the tips of the test needles protruding beyond the lower guide plate and / or on the lower guide plate, the mobility of the test needles relative to the guide plate is impaired or prevented. JP 2000-241454 A describes a device for testing semiconductor components, wherein a protective plate is provided on a guide plate and the ends of the test needles protruding beyond the guide plate penetrate the protective plate (see Fig. 1). The protective plate is attached to the surface of the guide plate facing the semiconductor component to be tested. CN 217181007 U and CN 218180937 U describe devices for electrically testing semiconductor components. The object of the invention is to ensure the mobility of test needles even if metal from the chip evaporates and / or splashes during testing due to a defect in the chip.This object is achieved with a device having the features of patent claim 1. Preferred and advantageous developments of the device according to the invention are the subject of the dependent claims. The invention proposes attaching (for example, gluing) a cover in the form of a protective plate to the underside of the lower guide plate - the side facing the semiconductor component (chip) to be tested - wherein the test needles engage through holes in the protective plate so as to be movable relative to the protective plate. The protective plate shields (like an umbrella) splashes of liquid metal and / or vaporized metal from the probe card, in particular from the lower guide plate. A protective plate, for example in the form of a plastic plate, has the advantage that the mobility of the needles is maintained even when the needles carry metal deposits from the (power) chip.Another advantage of a protective plate made of plastic is that metal adheres poorly or not at all to the plastic, so that the test needles remain movable. If the protective plate is made of a (relatively) soft material, the test needles remain movable relative to the guide plate, even if metal has deposited on the tips of the needles. Metal deposited on the test needles may cause the holes in the protective plate to widen, so that the test needles remain movable relative to the lower guide plate (and the protective plate). The holes in the protective plate through which the test needles pass can be dimensioned such that there is play between the holes and the test needles, so that the tips of the test needles can move relative to the protective plate, even if metal has deposited in the area of ​​the holes and / or on the tips of the test needles.The protective plate (plastic plate) is preferably connected to the probe card's test head by adhesive. Measures can be taken to prevent adhesive from being sucked into the center of the protective plate by capillary action and "sticking" the test needles. This measure can include openings, such as slit-shaped ones, arranged around the center, i.e., the area where the test needles of the test head penetrate the protective plate. Such openings interrupt the capillary action, so that no adhesive can penetrate between the guide plate and the protective plate into the area of ​​the test needles. Since the precise guidance of the test needle tips is ensured by the lower guide plate of the test head, the holes in the protective plate can be dimensioned such that the test needle tips fit into the holes in the protective plate with some clearance.Play between the test needles and the holes in the protective plate also has the advantage that the risk of metal deposited in the area of ​​the holes on the protective plate impairing the mobility of the tips of the test needles is prevented or at least reduced. Further details, advantages and features of the invention will emerge from the following description of exemplary embodiments with reference to the drawings. There shows: Fig. 1 a vertical needle card, known for example from AT 14209 U1, Fig. 2 a basic representation of a test head of a needle card with protective plate, Fig. 3 a detail of the test head from Fig. 2 in an enlarged representation and in section and Fig. 4 a view obliquely from below of a test head of a needle card with protective plate. A test head 7 of a vertical needle card 1 comprises a plurality of, for example angled, test needles 2. In Figs.1 and 4, the test needles 2 and their tips 3 are symbolically represented. In practice, for example, up to 3,000 or more test needles 2 are provided. Guides comprising an upper guide plate 5a and a lower guide plate 5b are provided in the test head 7. The tips 3 of the test needles 2 protrude beyond the lower guide plate 5b and are slidably guided in holes in the lower guide plate 5b. The test head 7 has a pressure chamber 6, which can be pressurized with compressed gas via lines 8. In the device according to the invention, a pressure chamber 6 is not mandatory in the test head 7. When the vertical probe card 1 with the test head 7 is placed on a semiconductor component to be tested, in the example shown a wafer 18 held on a holder (chuck) 19, the tips 3 of the test probes 2 move upwards relative to the lower guide plate 5b (double arrow 15 in Fig.3), wherein the regions of the test needles 2 lying between the guide plates 5a and 5b bend (bend out) under elastic deformation, as indicated by dashed lines (idealized!) for a test needle in Fig. 2. A protective plate 9 (cf. Figs. 2 and 3) is attached to the test head 7 of the vertical probe card 1 on the outer side (underside) of the lower guide plate 5b facing the wafer 18. Holes 10 are provided in the protective plate 9 for the ends of the test needles 2 which project downwards beyond the lower guide plate 5b and the protective plate 9 and carry the tips 3. The test needles 2 can have play relative to the holes 10 in the protective plate 9. The play arises because the diameter “D” of the holes 10 in the protective plate 9 is larger than the diameter “d” of the test needles 2. For example, the diameter “D” is in the order of 63 µm and the diameter “d” is in the order of 80 µm.The play of the test needles 2 in the holes 10 of the protective plate 9 also ensures that the mobility of the test needles 2, which are accommodated in the bores of the lower guide plate 5b (made of ceramic material) with sliding guide (linear plain bearing), is not impeded by the protective plate 9. This is the case even if the axes of the holes 10 in the protective plate 9 are offset from the axes of the bores in the lower guide plate 5b. The play of the test needles 2 relative to the holes 10 in the protective plate can be 10 µm to 20 µm, and in particular 17 µm. The protective plate 9 is made, for example, of an electrically insulating and preferably elastically deformable plastic, for example a polyimide.The protective plate 9 prevents metal components that have been thrown off (splashed) from the wafer 18 due to defects in the wafer 18 during testing of the wafer 18 due to explosive melting and / or evaporation of metal from the metallization of the wafer 18 from accumulating on the test needles 2 in the region of the lower guide plate 5b. Thus, movements of the test needles 2 relative to the lower guide plate 5b are not restricted or prevented. If there is play between the holes 10 in the protective plate 9 and the test needles 2, the test needles 2 are still movable even if metal that has been splashed from the wafer 18 or chip due to explosive melting and / or evaporation of metal from the metallization has accumulated in the region of the holes 10 in the protective plate 9 and / or on the test needles 2. As shown in Fig.4, the protective plate 9 is designed such that it covers the entire underside of the test head 7 facing the semiconductor component to be tested (wafer 18), and thus also the underside of the lower guide plate 5b of the vertical probe card 1. For fastening the protective plate 9 to the housing of the test head 7 of the vertical probe card 1, an adhesive technique is preferably considered. In the protective plate 9, in an area 13 that lies outside the area 12 in which the holes 10 for the test probes 2 are provided, a plurality of holes 17, for example circular, are provided. (Flowable) adhesive can be applied through the holes 17. The adhesive is distributed between the protective plate 9 and the lower guide plate 5b by capillary action.In order to prevent adhesive from being sucked into the area 12 with the test needles 2 by capillary action from the area 13 outside the area 12 of the lower guide plate 5b and the protective plate 9, in which the test needles 2 protrude with their tips 3 through the protective plate 9, openings, which have the shape of slit-shaped holes 11, for example, are provided around the area 12. The holes 11 are arranged in two rows (“double row”) in the embodiment of Fig. 4. The slit-shaped holes 11 ensure that no adhesive is sucked into the area 12 with the test needles 2 by capillary action from the area 13 outside the area 12 in which the test needles 2 are provided, and the movement of the test needles 2 relative to the lower guide plate 5b is hindered or prevented by sticking (adhering) the test needles 2 to the protective plate 9 and / or to the lower guide plate 5b.Outwardly open recesses 20 are provided in the protective plate 9, through which access to mounting screws 16 of the test body 7 is possible. The guide plates 5a and 5b are made of electrically insulating material, in particular ceramic, so that the test needles 2 are electrically insulated from one another. In summary, an embodiment of the invention can be described as follows: A device for testing wafers 18 or chips has a test head 7 in the form of a vertical probe card 1, the test needles of which are guided in a ceramic guide plate 5b with a sliding guide. A protective plate 9 is glued to the underside of the guide plate 5b facing the wafer 18 or chip to be tested. The test needles 2 protrude with play through holes 10 in the protective plate 9. Holes 17 are provided in the protective plate 9, through which adhesive can be introduced between the protective plate 9 and the lower guide plate 5b.Slit-shaped holes 11 are provided in the protective plate 9 surrounding the area 12 containing the holes 10 for the test needles 2. The holes 11 prevent adhesive from being sucked into the area 12 by interrupting the capillary action occurring between the protective plate 9 and the lower guide plate 5b.

Claims

Claims:

1. A device for electrically testing semiconductor components, such as wafers (18) or chips, comprising a test head (7) with a plurality of test needles (2), in particular comprising a test head (7) in the form of a vertical probe card (1), wherein the test needles (2) are slidably guided in holes in a guide plate (5b) and project beyond the guide plate (5b) in the direction of the semiconductor component to be tested, characterized in that a protective plate (9) is provided on the guide plate (5b), and in that the ends of the test needles (2) projecting beyond the guide plate (5b) and carrying the tips (3) pass through the protective plate (9).

2. A device according to claim 1, characterized in that the protective plate (9) is attached to the surface of the guide plate (5b) facing the semiconductor component to be tested. 3.Device according to claim 1 or 2, characterized in that the protective plate (5b) is attached to the guide plate (5b) outside the area (12) in which the test needles (2) are provided.

4. Device according to claim 2 or 3, characterized in that the protective plate (9) is attached to the guide plate (5b) by adhesive bonding.

5. Device according to claim 3 or 4, characterized in that holes (11) are provided in the protective plate (9) around the area (12).

6. Device according to claim 5, characterized in that the holes are slit-shaped holes (11).

7. Device according to claim 5 or 6, characterized in that the holes (11) are located in two mutually parallel rows surrounding the area (12).

8. Device according to one of claims 1 to 7, characterized in that the protective plate (9) has holes (17) provided in the area of ​​the outer edge of the protective plate (9).

9. Device according to claim 8, characterized in that the holes (17) are circular.

10. Device according to claim 8 or 9, characterized in that the holes (17) are provided in an area (13) of the protective plate (9) outside the area (12) in which the test needles (2) are provided, in particular in an area (13) of the protective plate (9) lying outside the slit-shaped holes (11).

11. Device according to one of claims 1 to 10, characterized in that the protective plate (9) consists of electrically insulating material. 12.Device according to one of claims 1 to 11, characterized in that the protective plate (9) is made of elastic material.

13. Device according to one of claims 1 to 12, characterized in that the test needles (2) are received in holes (10) in the protective plate (9).

14. Device according to claim 13, characterized in that the test needles (2) are accommodated in the holes (10) with some clearance.

15. Device according to one of claims 1 to 14, characterized in that the protective plate (9) extends over the entire surface of the test head (7) facing the semiconductor component to be tested.

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