GB2316534A

GB2316534A - Probe head and method for measuring electrical properties of multi-port circuit

Info

Publication number: GB2316534A
Application number: GB9704777A
Authority: GB
Inventors: Udomoto Junichi; Komaru Makio; Sasaki Yoshinobu
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1996-08-23
Filing date: 1997-03-07
Publication date: 1998-02-25
Anticipated expiration: 2017-03-07
Also published as: JPH1064962A; GB9704777D0; GB2316534B

Abstract

A probe head 5, 5a, 5b, for measuring electrical properties of a circuit (20) having n ports (n* <------ solidus *3) on a semiconductor chip (9), includes a pair of signal terminals 6a, 6b, to/from which an RF measuring signal is input/output; a grounding terminal 11; n-2 terminating circuits 4 terminated by 50 ohm; a pair of first probe groups A 1 , A 2 comprising a first port probe 1 connected to the signal terminal 6a or 6b and a pair of grounding probes 2 connecting to the grounding terminal 11; and n-2 second probe groups B comprising a second port probe 3 connected to the terminating circuit 4 and a pair of grounding probes 2 connecting to the grounding terminal (11). In testing a semiconductor chip, all ports of the chip except a pair of ports connected to the terminals 6a,6b are terminated by 50 ohm equal to the characteristic impedance of the system to obtain a matched state. This permits a precise measurement of electrical properties, e.g. S-parameter, isolation, when the chip is in wafer state.

Description

PROBE HEAD AND METHOD FOR MEASURING ELECTRICAL PROPERTIES OF MULTI-PORT CIRCUIT FITTED OF THE INVENTION The present invention relates to a probe head and a method for measuring electrical properties of a multi-port circuit. More particularly, the invention relates to a probe head and a method which can precisely measure, in a wafer state, electrical properties of a multi-port circuit realized on a semiconductor chip by putting a port not to be measuring object in one measuring, in a matched state.

BACKGROUND OF THE INVENTION Figure 9 is a top view illustrating a method for measuring, in a wafer state, electrical properties of a semiconductor chip provided with an electrical circuit having a pair of an input port and an output port. A wafer 25 that is a measuring object comprises plural semiconductor chips 9. Each semiconductor chip 9 is provided with an electrical circuit 20 having a pair of an input port and an output port, and a grounding via hole 18. On opposite sides of the top surface of the semiconductor chip 9, there are disposed an input port pad and an output port pad which are respectively connected to the input port and the output port of the electrical circuit 20. A pair of grounding pads 22 connected to the grounding via hole 18, face each other across an input port pad 21 and an output port pad 23.

A prior art probe head 5 serving as a measuring device, comprises a pair of an input-side probe head 5a and an output-side probe head 5b. At the tip of a main body 10 of the input-side probe head 5a, a pair of grounding pads 2 face each other across a port probe 1 at the same pitch as in the input port pad 21 and the grounding pads 22 of the semiconductor chip 9. The end of the port probe 1 is connected to a first signal terminal 6a, and the end of the grounding probe 2 is connected to a grounding terminal 11.

At the tip of the main body 10 of the output-side probe head 5b, the grounding probes 2 face each other across the port probe 1 at the same pitch as in the output port pad 23 and the grounding pads 22 of the semiconductor chip 9. The end of the port probe 1 is connected to a second signal terminal 6b, and the end of the grounding probe 2 is connected to the grounding terminal 11. The grounding probe 2 and the grounding pads 22 are ones that ground the semiconductor chip 9.

A description will be given of a method for measuring S-parameter of the wafer 25, with the prior art probe head.

The measurement of the wafer 25 is performed for each semiconductor chip 9. The wafer 25 is fixed to a fixture (not shown). The input-side probe head 5a and the outputside probe head 5b are respectively mounted on a stage (not shown) so that the tips of the port probe 1 and the grounding probes 2 of the probe heads 5a, 5b are positioned above the input port pad 21 and the grounding pads 22, and above the output-side port pad 23 and the grounding pads 22 in the semiconductor chip 9. The grounding terminals 11 of the input probe heads Sa, 5b are grounded, and the first signal terminal 6a and the second signal terminal 6b are respectively connected to an output terminal and an input terminal of radio frequency (hereinafter referred to as "RF") signals of such as a network analyzer (not shown), as a measuring apparatus.

The input-side probe head 5a and the output-side probe head 5b are descended so that the probes 1, 2 come into contact with each corresponding pad 21, 22, 23, and the RF signals from the network analyzer is input to the first signal terminal 6a. The RF signals thus input pass through the electric circuit 20 of the semiconductor chip 9 and are output from the second signal terminal 6b, and then input to the network analyzer, thereby making an S-parameter measurement. This measurement is made successively for all the semiconductor chips 9.

Meanwhile, some semiconductor chips are provided with a multi-port electric circuit (hereinafter referred to as "multi-port circuit"), which has three or more ports including at least one input port and at least one output port.

Figure 10 is a circuit diagram illustrating one example of the multi-port circuit. In the figure, reference numeral 41 designates an element. Each input terminal or each output terminal of the element 41 is successively branched and connected to realize the multi-port circuit having 32 input ports P1-P32 and 32 output ports P33-P64, as a whole.

In the semiconductor chip having the above multi-port circuit, if its electrical properties, such as S-parameter and isolation, are measured in a wafer state, by means of the prior art probe head as it is, ports except a pair of ports as a measuring object are in open state and then a floating state in the RF, failing to make a satisfactory measurement. Thus in the semiconductor chip having the multi-port circuit, an actual circuit should be connected to measure electrical properties such as S-parameter and isolation, making it impossible to measure the electrical properties in a wafer state.

Japanese Patent Unexamined Publication No. 7-209374 discloses a prior art probe head that is given consideration of the influence of a signal line not to be measuring object, in which lines facing each other across a main line of a probe contacting such a signal line are respectively connected to a matched termination. This probe head is directed to measure the isolation of a semiconductor package and more particularly to measure a semiconductor chip that is mounted on a package. It is therefore impossible to measure a semiconductor chip itself in a wafer state.

Further, not all signal lines not to be measuring object are connected to the matched termination at the probe head side, failing to measure precisely electrical properties of a multi-port circuit.

SUMMARY OF THE TNVENTTON It is an object of the present invention to provide a probe head for measuring electrical properties of a multiport circuit, by which electrical properties, such as Sparameter and isolation, of a semiconductor chip having a multi-port circuit can be measured precisely in a wafer state.

It is another object of the present invention to provide a method for measuring electrical properties of a multi-port circuit, by which electrical properties, such as S-parameter and isolation, of a semiconductor chip having a multi-port circuit can be measured precisely in a wafer state.

Other objects and advantages of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific embodiment are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to the those skilled in the art from this detailed description.

According to a first aspect of the present invention, a probe head is one that measures electrical properties of a multi-port circuit having at least one input port and at least one output port realized on a semiconductor chip, the sum of which is n pieces (n is an integer of not less than 3). This probe head includes a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; n-2 (n13) terminating circuits terminated by 50 ohm; a pair of first probe groups each comprising a first port probe and a pair of grounding probes facing each other across the first port probe, each grounding probe being connected to the grounding terminal; and n-2 second probe groups each comprising a second port probe connected to the terminating circuit, and a pair of grounding probes facing each other across the second port probe, each grounding probe being connected to the grounding terminal.

Therefore, in measuring a semiconductor chip provided with n pad groups each having port pads each being connected to each port, and a pair of grounding pads facing each other across the port pad, all the ports except a pair of ports to be measured in the above multi-port circuit are terminated by 50 ohm equivalent to the characteristic impedance of system of measurement, resulting in a matched state. This leads to a precise measurement of electrical properties, such as S-parameter and isolation, of a semiconductor chip having n ports, in a wafer state.

According to a second aspect of the present invention, the first probe groups of the above probe head are adjacent to each other. Thus it is possible to precisely measure the isolation of the semiconductor chip having a multi-port circuit, in a wafer state.

According to a third aspect of the present invention, at least one of the first probe groups is replaceable with at least one of the second probe groups. Thus the number of the probe heads needed in measuring n ports of the multi-port circuit can be reduced in proportion to the number of the second probe groups being replaceable with the first probe group.

According to a fourth aspect of the present- invention, a probe head is one that measures electrical properties of a multi-port circuit having at least one input port and at least one output port realized on a semiconductor chip, either of which sums into m (m is an integer of not less than 2), both of which sum into not less than three. This probe head includes a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; m terminating circuits terminated by 50 ohm; and m probe groups each comprising a port probe to be changed over and connected to the signal terminal or the terminating circuit, and a pair of grounding probes facing each other across the port probe, each grounding probe being connected to the grounding terminal.

Thus, by putting that the port probes of the probe group corresponding to the ports to be measured are respectively connected to the respective signal terminal, and the rest of the port probes are connected to the respective terminating circuits, an S-parameter measurement of a semiconductor chip having a multi-port circuit including m input or output ports, can be made by a single probe head.

According to a fifth aspect of the present invention, a probe head is one that measures electrical properties of a multi-port circuit having at least one input port and at least one output port realized on a semiconductor chip, the sum of which is n (n is an integer of not less than 3).

This probe head includes a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; n terminating circuits terminated by 50 ohm; and n probe groups each comprising a port probe to be changed over to be connected to the signal terminal or the terminating circuit, and a pair of grounding probes facing each other across the port probe, each grounding probe being connected to the grounding terminal.

Thus, by putting that the port probes of the probe group corresponding to the ports to be measured are respectively connected to the respective signal terminals, and the rest of the port probes are respectively connected to the terminating circuit, S-parameter and isolation measurements for a semiconductor chip having a multi-port circuit in which the input and output ports sum into n, can be made by a single probe head.

According to a sixth aspect of the present invention, a probe head is one that measures electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, either of which sums into 2 through m (m is not less than 2), and both of which sum into not less than three. This probe head includes a signal terminal to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; 2m-2 terminating circuits terminated by 50 ohm; a first probe group comprising a first port probe and a pair of grounding probes facing each other across the first port probe, each grounding probe being connected to the grounding terminal; and 2m-2 second probe groups each comprising a second port probe connected to the terminating circuit and a pair of grounding probes facing each other across the second port probe and being connected to the grounding terminal, the second probe groups being disposed linearly or circularly at uniform intervals on both sides of the first probe group, each second probe group position being adjustable in a direction in which the probe head comes into contact with the semiconductor chip.

Thus, in measuring S-parameter of a semiconductor having a multi-port circuit including not more than m input or output ports, in which no more than m pad groups each having port pads respectively connected to each port and a pair of grounding pads facing each other across the port pad are disposed linearly or circularly, the number of the second probe groups facing each other across the first probe group and the positions of the first and second probe groups in a direction in which the probe head comes into contact with the semiconductor chip, are adjusted so that the first probe group comes into contact with the pad group corresponding to a port to be measured; the respective second probe groups come into contact with all pad groups except the above pad group; and the rest of the second probe groups do not come into contact with the semiconductor.

This leads to that not more than m input or output ports can be measured by a single probe head.

According to a seventh aspect of the present invention, a probe head is one that measures electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, the sum of which is n (n is an integer of not less than 3). This probe head includes a pair of signal terminals, to which an RF measuring signal is input, and from which the RF signal is output; a grounding terminal to be grounded; n-2 terminating circuits terminated by 50 ohm; a pair of first contact groups each comprising a first port contact and a pair of grounding probes facing each other across the first port contact; n-2 second contact groups each comprising a second port contact and a pair of grounding contacts facing each other across the second port contact; a flexible membrane member, whose undersurface central part being provided with the first and second contact groups, whose outer peripheral part being provided with an intermediate connecting terminal connected to each contact of the first and second contact groups; and a housing member which holds an outer peripheral part of the membrane member by pressing downward the central part of the membrane member, and is provided with the signal terminals and being connected to each first port contact of the first contact group through the intermediate connecting terminal of the membrane member; the grounding terminal being connected to each grounding terminal of the first and second contact groups through the intermediate connecting terminal; and the terminating circuits each being connected to the second port contact of the second contact group through the intermediate connecting terminal.

Since the probe head is composed of the membrane member, it is possible to readily.make electrical measurements of a multi-port circuit in a further minute semiconductor chip.

According to an eighth aspect of the present invention, a method for measuring, in RF, electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip of a wafer state, the input and output ports summing into n (n is an integer of not less than 3), comprises the steps of connecting an output terminal and an input terminal of measuring signals of an measuring apparatus to a pair of the input port and the output port of the multi-port circuit; and connecting terminating circuits terminated by resistance equal to characteristic impedance of system of measurement to all ports except the above input and output ports.

Therefore, every port that will not become an measuring object in a multi-port circuit is in a matched state during one measurement, allowing to precisely measure electrical properties such as S-parameter and isolation, in a wafer state.

BRIEF DESCRTPTION OF THE DRAWINGS Figure 1 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit according to a first embodiment of the present invention.

Figure 2 is a top view illustrating a method for measuring electrical properties of a semiconductor chip having a multi-port circuit, by using the probe head shown in Figure 1.

Figure 3 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to a second embodiment of the present invention.

Figure 4 is a perspective view illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to a third embodiment of the present invention.

Figure 5 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to a fourth embodiment of the present invention.

Figure 6 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to a fifth embodiment of the present invention.

Figure 7 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to a sixth embodiment of the present invention.

Figure 8(a) and Figure 8(b) are an undersurface view and a sectional view, respectively, illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to a seventh embodiment of the present invention.

Figure 9 is a top view illustrating a method for measuring electrical properties of a semiconductor chip in a wafer state, by using a prior art probe head.

Figure 10 is a circuit diagram illustrating one example of a multi-port circuit provided with a semiconductor chip.

flETATLED DESCRIPTION OF THE PREFERRED EMBODIMENT [Embodiment 1] Figure 1 a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to the embodiment 1 of the present invention. With reference to Figure 1, description will be given of the constitution of the probe head. A probe head 5 comprises a pair of an input-side probe head 5a and an output-side probe head 5b.

At the tip of a probe main body 10 of the input-side probe head 5a, a first probe group A1 and m-1 (m is an integer of not less than 2) second probe groups B are linearly disposed at a prescribed pitch.

The first probe group A1 comprises a first port probe 1 and a pair of grounding probes 2 facing each other across the probe 1, all of which are disposed at a prescribed pitch. The end of the probe 1 is connected to a first signal terminal 6a, and each end of the grounding probes 2 is connected to a grounding terminal 11.

The second probe group B comprises a second port probe 3 and a pair of grounding probes 2 facing each other across the probe 3, all of which are disposed at the same pitch as in the first probe group. The end of the probe 3 is connected to a terminating circuit 4 terminated by a terminal resistance 4a of 50 ohm, and each end of the probes 2 is connected to the grounding terminal 11.

The output-side probe head 5b has a first probe group A2 and m-l second probe groups B, and has the same constitution as the input-side probe head 5a, except that the first port probe 1 of the first probe group A2 is connected to a second signal terminal 6b.

Figure 1 illustrates the constitution of a probe head in the case where a measurement of such as S-parameter is made against a pair of an input port and an output port in a multi-port circuit which has m input ports and m output ports, and the sum of both is n=2m. In order to make Sparameter measurements for all ports of the multi-port circuit, it is necessary to prepare m input-side probe heads and m output-side probe heads, in which each position of the first probe groups A1, A2 is changed in response to the position of a port to be measured. In cases where in a multi-port circuit the number of input ports does not agree with that of output ports, it should be adjusted that the number of the first probe groups A1 and the second probe group B of the input-side probe head does not agree with that of the first probe groups A2 and the second probe group B of the output-side probe head.

Figure 2 is a top view illustrating a method for measuring, in a wafer state, electrical properties of a semiconductor chip having a multi-port circuit, by using the probe head 5 as shown in Figure 1.

A wafer 25 is a measuring object and is provided with plural rectangular semiconductor chips 9. The chip 9 is provided with a multi-port circuit 20 (electric circuit) having m input ports and m output ports, and grounding via holes (not shown). On opposite sides of the top surface of the semiconductor chip 9, m input-side pad groups D and m output-side pad groups E are provided at the same pitch as in the probe groups of the input-side probe head 5a and the output-side probe head 5b. The input-side pad group D comprises an input port pad 21 and a pair of grounding pads 22 facing each other across the pad 21, all of which are disposed at the same pitch as in the probe group of the input-side probe head Sa. The input port pad 21 is connected to an input port (not shown) of the multi-port circuit 20, and the grounding pad 22 is connected to a via hole (not shown). The output-side pad group E comprises an output port pad 23 and a pair of grounding pads 22 facing each other across the pad 23, all of which are disposed at the same pitch as in the probe group of the output-side probe head 5b. The output port pad 23 is connected to an output port (not shown) of the multi-port circuit 20, and the grounding pad 22 is connected to a via hole (not shown).

With reference to Figures 1 and 2, description will be given of a method of S-parameter measurement of the wafer 25, by using the aforementioned probe head 5.

The wafer 25 is fixed to a fixture (not shown). The input-side probe head 5a and the output-side probe head Sb are mounted on a stage (not shown). At this time, each tip of the respective probes 1, 2 of the probe heads 5a, 5b are set so that each tip is positioned above the respective pad 21, 22, 23 of the semiconductor chip 9. Then, the grounding terminals 11 of the probe heads 5a, 5b are grounded, and the first signal terminal 6a and the second signal terminal 6b are respectively connected to an output terminal and an input terminal of RF signals from a network analyzer (not shown). The characteristic impedance of the network analyzer is normally 50 ohm.

Then, the probe heads 5a, 5b are descended, and each probe 1, 2 is brought into contact with the respective pad 21, 22, 23 of the semiconductor chip 9. The RF signal from the output terminal of the network analyzer is input to the first signal terminal 6a. The RF signal thus input is input to the input port of the multi-port circuit 20 of the semiconductor chip 9 through the first port probe 1 of the first probe group A1, then output from the output port of the multi-port circuit 20 to the second signal terminal 6b through the first port probe 1 of the first probe group A2, and input to the input terminal of the network analyzer, thus completing the S-parameter measurement.

Since all ports except the ports to be measured are terminated by the terminal resistance 4a, which is connected to the second port probe 3, and has 50 ohm equivalent to the characteristic impedance of the multi-port circuit.

Therefore, every port not to be measuring object is in a matched state, permitting a precise S-parameter measurement.

Thereafter, the probe heads 5a and 5b are ascended to the original positions, thus completing the measurement for a single semiconductor chip 9. The same measurement is made for other semiconductor chips 9 of the wafer 25.

After that, the probe heads 5a or 5b is replaced with one that corresponds to the next port to be measured, followed by the above measurement. The aforementioned steps are repeated to make an S-parameter measurement for a desired port of the multi-port circuit.

Thus in the embodiment 1, the probe head includes a pair of the probe groups A1, A2 each having the first port probe 1 connected to the signal terminal and a pair of the grounding probes 2 facing each other across the first port probe 1; and n-2 (n=2m) of the second probe groups each having the second port probe 3 connected to the terminating circuit 4 terminated by 50 ohm, and a pair of the grounding probes 2 facing each other across the second port probe 3.

Therefore, in measuring the semiconductor chip 9 having the multi-port circuit including n input ports and n output ports, all the ports except the measuring object in the multi-port circuit 20 are terminated by the terminal resistance 4a which is connected to the second port probe 3, and has 50 ohm equivalent to the characteristic impedance of system of measurement, and all the ports not to be measuring object are in a matched state, permitting a precise Sparameter measurement in wafer state.

Further in the embodiment 1, in measuring electrical properties of a multi-port circuit, each of the input and output terminals of measuring signals of a measuring apparatus is connected to a pair of ports in the multi-port circuit 20 having n ports, and all the port except the above ports being system of measurement are connected to the terminating circuit 4 terminated by a resistance value equivalent to the characteristic impedance of the system of measurement, to measure the electrical properties of the multi-port circuit 20 in RF.

Accordingly, all the ports not to be measuring object in the multi-port circuit 20 are in a matched state at the time of the measuring, leading to precise measurements of electrical properties such as S-parameter and isolation, in a wafer state.

[Embodiment 2] Figure 3 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to the embodiment 2 of the present invention. In the figure the same reference numerals as used in Figure 1 designate the same or corresponding parts. The embodiment 2 has the same constitution as shown in Figure 1 (the embodiment 1), except that a pair of the first probe groups A1, A2 are disposed so that they are adjacent to each other on a probe head 5a, and a second probe group B alone is disposed on a probe head 5b.

Figure 3 illustrates the case where the first probe groups A1, A2 are disposed on the input-side probe head 5a, but in measuring the isolation between output ports of a multi-port circuit, a pair of the first probe groups A1, A2 are disposed on the output-side probe head 5b.

In the embodiment 2, a wafer being measuring object is the same as in the embodiment 1 (see Figure 2).

With reference to Figures 2 and 3, description is now given of a method for measuring the isolation of the wafer 25 by using the probe head 5 as described.

In the same manner as in the embodiment 1, the inputside probe head 5a and the output-side probe head 5b are mounted on a stage and then descended, and each of the probe groups A1, A2, B of the probe heads 5a, 5b are brought into contact with the respective pad groups D, E of the semiconductor chip 9. RF signals from the network analyzer is input to the first signal terminal 6a. The RF signal thus input is input to a certain input port of the multiport circuit 20 of the semiconductor chip 9 through the first port probe 1 of the first probe group A1. In reply to this input, an output from an input port adjacent to the above certain input port of the above multi-port circuit 20, is output from the second signal terminal 6b through the first port probe 1 of the first probe group A2, and then input to the input terminal of the network analyzer, thus making an isolation measurement.

Since all the ports except the measuring object in the multi-port circuit 20 are terminated by the terminal resistance 4a, which is connected to the second port probe 3, and has 50 ohm equivalent to the characteristic impedance of the system of measurement, all the ports not to be a measuring object are in a matched state, permitting a precise isolation measurement.

Then in the same manner as in the embodiment 1, the probe heads 5a, 5b are ascended to the original positions, thus completing the measurement for a single semiconductor chip 9. The above measurement is made for other semiconductor chips 9 of the wafer 25, thus completing the measurements against all the semiconductor chips 9 of the wafer 25.

Thereafter, the above probe head 5a or 5b is successively replaced with one that corresponds to a port to be measured, followed by the aforementioned measurement, thereby making the isolation measurement for a desired port in the multi-port circuit.

Thus the embodiment 2 in which a pair of the prove groups A1, A2 are disposed so that they are adjacent to each other, realizes the probe head by which the isolation between adjacent ports in a multi-port circuit can be measured precisely in a wafer state.

[Embodiment 3] Figure 4 is a perspective view illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to the embodiment 3 of the present invention. In the figure, the same reference numerals as used in the Figure 1 designate the same or corresponding parts. In the input-side probe head 5a and the output-side probe head 5b, the tip of the probe main body 10 is in the shape of a housing whose tip surface 10a is realized on a slope inclined backward. The tip surface 1Oa is provided with a slide groove 15 comprising by connecting an upper horizontal groove 15a and a lower horizontal groove 15b which are disposed horizontally in parallel, with four longitudinal grooves 15c which are disposed longitudinally at regular intervals. The slide grove 15 is equipped with four probe holding members 14 so that they are slidable. Each probe 1, 2 of the first probe group A1 or A2 is fixed into one of the four probe holding members 14, and each probe 2, 3 of the second probe groups B1, B2, B3 is fixed into each of other three probe holding members, at a predetermined pitch.

Each probe 1, 2, 3 of the probe group A1 or A2, and B1, B2, B3 is connected to the signal terminal or the grounding terminal or the terminating circuit (which are not shown), by such as a coaxial cable, etc. In the embodiment 3, the probe groups of the input-side probe head 5a or the outputside probe head 5b are four in number, and the first probe group A1 or A2 is replaceable with each of the second probe groups B1, B2, B3.

With reference to Figure 4, description is now given of the handling of the probe heads 5a, 5b as described. Each probe holding member 14 is normally located in the lower horizontal groove 15b. Assuming that a measurement is terminated with a layout of the probe groups as shown in the figure, followed by a measurement against a port located in a position corresponding to the second probe group B2.

Firstly the second probe group B2 is moved to the upper horizontal groove 15a through the longitudinal groove 15c, and then moved to the left end in the groove 15a. Next, the first probe group A1 is moved to the groove 15a through the groove 15c and then moved to the position in the groove 15 in which the probe group B2 has been located, through the grooves 15a and 15c. Thereafter, the second probe group B2 at the left end in the groove 15a is moved to the position in the groove 15b in which the probe group A1 has been located, through the grooves 15a and 15c. Accordingly, the replacement of the probe group A1 by the probe group B2 is completed, followed by a measurement.

As described above, by replacing the first probe group A1 with one of the second probe groups B1, B2, B3 so that the probe group A1 is located in a position corresponding to a port to be measured, S-parameter measurements against all ports of a multi-port circuit having four input ports and four output ports can be accomplished by a pair of the input-side probe head 5a and the output-side probe head 5b.

The above description is given of the case where the probe group is set for four in number, the number of the probe groups may be any arbitrary number of not less than two.

Although all the second probe groups B1, B2, B3 are J replaceable with the first probe group A1, part of the second probe groups may be replaceable with the first group A1. In such a case, the number of the input-side probe head 5a or the output-side probe head 5b can be reduced in reply to the number of the replaceable second probe group.

Although a single first probe group A is provided with each probe head 5a, 5b in accordance with the embodiment 1, two first probe groups may be disposed so that they are adjacent to each other in each probe head 5a, 5b, in accordance with the embodiment 2. In such a case, the isolation measurements for all ports of a multi-port circuit can be made by a pair of the input-side probe head 5a and the output-side probe head 5b. It is also possible that part of the second probe groups is replaceable with a pair of the first probe groups.

Thus in the embodiment 3, at least one of the first probe groups A1, A2 is replaceable with at least one of the second probe groups B1, B2, B3. Therefore, the number of the probe heads needed in measuring all ports of a multiport circuit can be reduced in reply to the number of the second probe group being replaceable with the first probe group.

[Embodiment 4] Figure 5 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to the embodiment 4 of the present invention. In the figure, the same reference numerals as used in the Figure 1 designate the same or corresponding parts. A changeover switch 8 changes over to connect a third port probe 7 to the terminating circuit 4 terminated by the terminal resistance 4a of 50 ohm, or to the signal terminal, i.e., the first signal terminal 6a for the input-side probe head 5a; and the second signal terminal 6b for the output-side probe head 5b.

A third probe group C comprises the third port probe 7 and a pair of grounding probes 2 facing each other across the port probe 7. The embodiment 4 differs from the embodiment 1 in that all probe groups of the input-side probe head 5a and the output-side probe head 5b are composed of the third probe groups C.

With reference to Figure 5, description will be given of a method of S-parameter measurement by using the probe head 5 as described.

In the same manner as in the embodiment 1, the inputside and output-side probe heads 5a, 5b are mounted on a stage. A pair of third port probes 7a, 7b corresponding to a pair of ports to be measured by the probe heads 5a, 5b, are respectively connected to the first signal terminal 6a and the second signal terminal 6baby the changeover switch 8. All the third port probes 7 except the above probes 7a, 7b in the probe heads 5a, 5b are respectively connected to the terminating circuit 4 by the changeover switch 8.

Then in the same manner as in the embodiment 1, an Sparameter measurement is made. The aforementioned steps are repeated to complete S-parameter measurements for all ports of the multi-port circuit.

As describe above, the embodiment 4 includes m probe groups C which has the port probe 7 being changed over to be connected to the signal terminal 6a or 6b or the terminating circuit 4 terminated by 50 ohm, and a pair of the grounding probes 2 facing each other across the port probe 7.

Therefore, by connecting each probe 7a, 7b of the probe group C that corresponds to a port to be measured to each signal terminal 6a, 6b, and connecting the rest of the probe groups C to the terminating circuit 4, the S-parameter measurement of a semiconductor chip having a multi-port circuit including m input or output ports, can be accomplished by a single probe head.

[Embodiment 5] Figure 6 is a top view schematically illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to the embodiment 5 of the present invention. In the figure, the same reference numerals as used in Figure 1 designate the same or corresponding parts. A changeover switch 16 changes over to connect a fourth port probe 17 to the terminating circuit 4 terminated by the terminal resistance 4a of 50 ohm, or the first signal terminal 6a or the second signal terminal 6b. A fourth probe group F comprises the port probe 17 and a pair of grounding probes 2 facing each other across the port probe 17. The embodiment 5 differs from the embodiment 1 or 2 in that all the probe groups of the probe heads 5a, 5b are composed of the fourth probe groups F.

With reference to Figure 6, description will be given of a method of measuring isolation by using the probe head 5 as described.

In the same manner as in the embodiment 2, the inputside and output-side probe heads 5a, 5b are mounted on a stage. In a pair of fourth port probes 17a and 17b that correspond to a pair of ports to be measured by the inputside probe head 5a are respectively connected to the first signal terminal 6a and the second signal terminal 6b, respectively, by the changeover switch 16. All the fourth port probes 17 except the above probe 17a, 17b in the inputside probe head 5a are respectively connected to the terminating circuit 4 by the changeover switch 16. The fourth port probes 17 of all probe groups F in the outputside probe head 5b are respectively connected to the terminating circuit 4 by the changeover switch 16.

Then in the same manner as in the embodiment 2, an isolation measurement is made. The aforementioned steps are repeated to complete isolation measurements against all the ports of the multi-port circuit.

A description will be given of a method of measuring Sparameter by using the probe head 5 as described.

In the same manner as previously described, the inputside and output-side probe heads 5a, 5b are mounted on a stage. A pair of the fourth port probes 17 that correspond to a pair of ports to be measured by the probe heads 5a, 5b, are respectively connected to the first signal terminal 6a and the second signal terminal 6b, by the changeover switch 16. All the fourth port probes 17 except the above pair probes 17 in the probe heads 5a, 5b are respectively connected to the terminating circuit 4 by the changeover switch 16.

Then in the same manner as in the embodiment 1, an Sparameter measurement is made. The aforementioned steps are repeated to complete S-parameter measurements against all ports of the multi-port circuit.

As described above, the embodiment 5 includes n (n=2m) fourth probe groups F each having the fourth port probe 17 that is changed over to be connected to the signal terminal 6a or 6b or the terminating circuit 4 terminated by 50 ohm, and the grounding probes 2 facing.each other across the port probe 17. Therefore, by connecting the probes 17 of the fourth probe group F that corresponds to a pair of ports to be measured to each signal terminal 6a, 6b, and connecting all the probes 17 of the rest of the probe groups F to each terminating circuit 4, S-parameter and isolation measurements of a multi-port circuit having n ports can be made by a single probe head S.

[Embodiment 6] Figure 7 is a top view illustrating a constitution of a probe head for measuring electrical properties of a multiport circuit, according to the embodiment 6 of the present invention. In the figure the same reference numerals as used in Figure 1 designate the same or corresponding parts.

In the input-side probe head 5a, the first probe group A1 and the second probe groups B are disposed at the tip of the probe main body 10, so that both sides of the probe group A1, m-1 second probe groups B are disposed linearly at a predetermined pitch. Each probe group B is fixed into a probe holding member 12 provided for each probe group B.

The probe holding member 12 is slidable up and down with respect to the probe main body 10, and has a screw hole (not shown) that goes through up and down. A screw 13 that is inset in the screw hole is installed rotatably to the probe main body 10. Therefore, by turning the screw 13 right and left, the probe holding member 12.can move up and down.

The output-side probe head 5b has the same constitution as the input-side probe head 5a, except that the first port probe 1 of the first probe group A2 is connected to the second signal terminal 6b.

A wafer as a measuring object in the embodiment 6 is the same as that of the embodiment 1 (see Figure 2).

Referring to Figures 2 and 7, description will be given of a method for measuring S-parameter of the wafer 25, by employing the probe heads 5a and 5b as described.

In the same manner as in the embodiment 1, the inputside probe head 5a and the output-side probe head 5b are respectively mounted on a stage in which the input-side probe head 5a and the output-side probe head 5b are movable in the direction of the array of the probe groups A1, A2, B.

Then, in order that the first probe groups A1, A2 are positioned above a pair of an input-side pad group D and an output-side pad group E each corresponding to a port to be measured in the multi-port circuit 20 of the semiconductor chip 9, each probe head 5a, 5b is moved in the direction of the array of the probe groups. Further, in order that among the second probe groups B, those which are positioned above the input-side pad group D and the output-side pad group E of the semiconductor chip 9 come into contact with each pad group D, E; and the rest do not come into contact with the semiconductor chip 9 at the time of measuring, the height of each probe is adjusted accordingly by turning the screw 13.

Thereafter, an S-parameter measurement is made in the same manner as in the embodiment 1, and the above steps are repeated to complete S-parameter measurements against all ports of the multi-port circuit.

Although in the above description the probe groups A1, A2, B, and the pad groups D, E of the semiconductor chip are disposed linearly, they may be disposed circularly.

As described above, the embodiment 6 is characterized in having 2m-2 second probe groups B that are capable of adjusting their positions when they contact with a semiconductor chip of the probe head, and disposed linearly or circularly on both sides of the first probe group A1 (A2), which comprises the first port probe 1 connected to the signal terminal 6a (6b); the first probe group A1 (A2) having a pair of grounding probes 2 facing each other across the first port probe 1; the second port probes 3 each being connected to the terminating circuit 4 terminated by 50 ohm; and a pair of grounding probes 2 facing each other across the second port probe 3.

Thus, when an S-parameter is made for a semiconductor chip on a multi-port circuit having not more than m input or output ports, and provided with not more than m pad groups being disposed linearly or circularly, which pad group comprises port pads connected to each port and a pair of grounding pads facing each other across the port pad, the above input or output ports can be managed with a single probe head by adjusting the number of the second probe groups B facing each other across the first probe group, and the position of the first and second probe groups in a direction in which the probe head comes into contact with the semiconductor chip, so that the first probe group A1 (A2) comes into contact with a pad group corresponding to a port to be measured; the second probe group B comes into contact with all the pad groups except the above pad group; and the rest of the second probe groups B do not come into contact with the semiconductor chip.

[Embodiment 7] Figure 8(a) and Figure 8(b) are an undersurface view and a sectional view, respectively, illustrating a constitution of a probe head for measuring electrical properties of a multi-port circuit, according to the embodiment 7 of the present invention. The probe head is composed of an outer housing 31 in the form of a hollow disk, and an inner housing 32 that is inset into the inner periphery of the outer housing 31.

The inner housing 32 has a circular membrane 35 (membrane member). A substrate 45 is disposed at the center part of the membrane 35. Under surface of the substrate 45 is provided with plural patterned contacts 36, and the top surface of the substrate 45 is provided with a pressure plate 46. The top surface of the outer peripteral part of the membrane 35 is provided with a stiffener 37, and the outer peripheral part of the membrane 35 is provided with plural intermediate connecting terminals 51 so that they pass through the stiffener 37 (its situation is not shown), which terminal is connected to each contact 36. A flange is formed at the lower end of the outer periphery of an inner housing member 39 in the shape of an approximate disk, and a recess is formed at the center part of the undersurface of the inner housing member 39. A spring 40 whose tip is provided with a center pivot 42, is fit into the recess.

The outer peripheral part of the membrane 35 is fixed into the flange of the inner housing member 39 by a screw 34 through the stiffener 37. The center part of the membrane 35 is pressed downward by the spring 40 through the center pivot 42 and the pressure plate 46.

The outer housing 31 has a probe card 43 in the shape of an approximate hollow disk. The inner periphery of the probe card 43 is fit into the outer periphery of the flange of the inner housing member 39 in the inner housing 32. The inner peripheral part of the probe card 43 is provided with a substrate 50. The undersurface of the substrate 50 is provided with plural patterned interconnects 38 at such positions that they correspond to the respective intermediate connecting terminals 51 of the membrane 35.

Plural outer connecting terminals 49 that are connected to each interconnect 38, are radially disposed on the outer part of the substrate 50 of the probe card 43. The outer peripheral part of the probe card 43 is provided with screw holes 33. When the probe head is mounted on a stage (not shown), a pogo pin contact 44 comes into contact with the outer connecting terminal 49.

To fix the inner housing into the outer housing 31, the inner housing member 39 is fit into the inner peripheral part of the probe card 43 of the outer housing 31 and, using a top plate 47, a screw 48 is tightened up so that the probe card 43 is sandwiched with the top plate 47 and the stiffener 37 of the inner housing 32.

Similarly to the first probe group A and the second probe group B in the embodiment 1 (see Figure 1), the contact 36 is composed of a pair of first contact groups each comprising a pair of first port contacts respectively connected to the first signal terminal and the second signal terminal; a pair of grounding contacts being connected to each grounding terminal and facing each other across the first port contact; and n-2 second contact groups each comprising n-2 second port contacts connected to each terminating circuit terminated by a terminal resistance of 50 ohm, and a pair of grounding contacts being contacted to each grounding terminal and facing each other across the second port contact. The outer connecting terminal 49 is composed of the first signal terminal, the second signal terminal and the grounding terminal. Each terminating circuit is provided on the outer housing 31 (its situation is not shown).

Each semiconductor chip of a wafer 30 is provided with the first contact group and a pad group corresponding to the second contact group, as in the embodiment 1 (see Figure 2).

Referring to Figure 8, a method of S-parameter measurement using the aforementioned probe head will be described.

The wafer 30 is fixed into a fixture (not shown), and the probe head is mounted on a stage (not shown) by tightening a screw hole 33 of the outer housing by a screw.

The outer connecting terminal 49 is connected to input and output terminals of measuring signals of a measuring apparatus, or grounded, through the pogo pin contact 44.

Then, the contact 36 of the probe head is positioned above a semiconductor chip to be measured in the wafer 30, and the probe head is descended to a predetermined position. The contact 36 thus descended has a contact with the pad group of the semiconductor under pressure of the spring 40, thus making an S-parameter measurement in the same manner as in the embodiment 1.

The above description relates to the S-parameter measurement, however, it is possible to make an isolation measurement by disposing a pair of the first contact groups so that both are adjacent to each other, and utilizing the same method as in the embodiment 2.

As described above, the embodiment 7 utilizes the membrane member in the probe head, facilitating electrical measurements against a multi-port circuit of a further minute semiconductor chip.

Although the above embodiments describe the cases where a pad connected to an input port of a multi-port circuit and a pad connected to an output port are disposed on two opposed sides of a semiconductor chip, the present invention is applicable to the cases where the pad connected to the input port and the pad connected to the output port are disposed on one side or adjacent sides of the semiconductor chip.

Although in the above embodiments the input-side probe head and the output-side probe head are separated, both may be integrated.

Claims

WHAT TS CLAIMED TS:

1. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, the input port and the output port summing into n (n is an integer of not less than 3), including: a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; n-2 terminating circuits terminated by 50 ohm; a pair of first probe groups each comprising a first port probe and a pair of grounding probes facing each other across the first port probe, each grounding probe being connected to the grounding terminal; and n-2 second probe groups each comprising a second port probe connected to the terminating circuit, and a pair of grounding probes facing each other across the second port probe, each grounding probe being connected to the grounding terminal.

2. A probe head of claim 1 wherein the first probe groups are adjacent to each other.

3. A probe head of claim 1 wherein at least one of the first probe groups is replaceable with at least one of the second probe groups.

4. A probe head of claim 2 wherein at least one of the first probe groups is replaceable with at least one of the second probe groups.

5. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, either of the input port and the output port summing into m (m is an integer of not less than 2), both of which summing into not less than three, including: a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; m terminating circuits terminated by 50 ohm; and m probe groups each comprising a port probe that is changed over to be connected to either of the signal terminal and the terminating circuit, and a pair of grounding probes facing each other across the port probe, each grounding probe being connected to the grounding terminal.

6. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, the input port and the output port summing into n (n is an integer of not less than 3), including: a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; n terminating circuits terminated by 50 ohm; and n probe groups each comprising a port probe that is changed over to be connected to either of the signal terminal and the terminating circuit, and a pair of grounding probes facing each other across the port probe, each grounding probe being connected to the grounding terminal.

7. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, either of the input port and the output port summing into m (m is not less than two), both summing into not less than three, including: a signal terminal to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; 2m-2 terminating circuits terminated by 50 ohm; a first probe group comprising a first port probe and a pair of grounding probes facing each other across the first port probe, each grounding probe being connected to the grounding terminal; and 2m-2 second probe groups each comprising a second port probe connected to the terminating circuit and a pair of grounding probes facing each other across the second port probe and being connected to the grounding terminal, the above second probe groups being disposed at uniform intervals on both sides of the first probe group in either of linearly and circularly, each second probe group position being adjustable in a direction in which the probe head contacts the semiconductor chip.

8. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, the input port and the output port summing into n (n is an integer of not less than 3), including: a pair of signal terminals, to which an RF measuring signal is input, and from which the RF signal is output; a grounding terminal to be grounded; n-2 terminating circuits terminated by 50 ohm; a pair of first contact group each comprising a first port contact and a pair of grounding contacts facing each other across the first port contact; n-2 second contact groups each comprising a second port contact and a pair of grounding contacts facing each other across the second port contact; a flexible membrane member whose undersurface central part being provided with the first and second contact groups, whose outer peripheral part being provided with an intermediate connecting terminal connected to each contact of the first and second contact groups; and a housing member pressing downward a central part of the membrane member and holding an outer peripheral part of the membrane member, the housing member having the signal terminals being connected to each first port contact of the first contact group through the intermediate connecting terminal of the membrane member, the grounding terminal being connected to each grounding terminal of the first and second contact groups through the intermediate connecting terminal, and the terminating circuits each being connected to the second port contact of the second contact group through the intermediate connecting terminal.

9. A method for measuring electrical properties in RF against a multi-port circuit having at least one input port and at least one output port on a semiconductor chip of a wafer state, the input and output ports summing into n (n is an integer of not less than 3), comprising the steps of: connecting an output terminal and an input terminal of measuring signals of an measuring apparatus to a pair of the input port and the output port of the multi-port circuit; and connecting terminating circuits terminated by resistance equal to characteristic impedance of system of measurement to all ports except the above input and output ports.

10. A method of using an RF signal to measure electrical properties of a multi-port circuit substantially as herein before described with reference to Figures 1 and 2; or Figure 3; or Figure 4; or Figure 5; or Figure 6; or Figure 7; or Figures 8(a) and 8(b) of the accompanying drawings.

10. A probe head for measuring electrical properties of multi-port circuit substantially as hereinbefore described with reference to Figures 1 and 2; or Figure 3; or Figure 4; or Figure 5; or Figure 6; or Figure 7; or Figures 8(a) and 8(b) of the accompanying drawings.

11. A method of measuring electrical properties in RF against a multi-port circuit substantially as hereinbefore described with reference to Figures 1 and 2; or Figure 3; or Figure 4; or Figure 5; or Figure 6; or Figure 7; or Figures 8(a) and 8(b) of the accompanying drawings.

Amendments to the claims have been filed as follows

1. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, the total number of input and output ports being n, where n is an integer of not less than 3; the said head including: a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; n-2 terminating circuits terminated by 50 ohm; a pair of first probe groups each comprising a first port probe and a pair of grounding probes facing each other across the first port probe, each first port probe being connected to a respective one of the signal terminals and each grounding probe being connected to the grounding terminal; and n-2 second probe groups each comprising a second port probe connected to a respective one of the terminating circuits, and a pair of grounding probes facing each other across the second port probe, each grounding probe being connected to the grounding terminal.

3. A probe head according to claim 1 or 2, wherein at least one of the first probe groups is interchangeable with at least one of the second probe groups.

4. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, where either of the total number of input ports and the total number of output ports is m, where m is an integer of not less than 2, and the total number of input and output ports is not less than three; the said head including: a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; m terminating circuits terminated by 50 ohm; and m probe groups each comprising a port probe that is selectively connectable to either of the signal terminals or a respective one of the terminating circuits. and a pair of grounding probes facing each other across the port probe, each grounding probe being connected to the grounding terminal.

5. A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, the total number of input and output ports being n, where n is an integer of not less than 3, the said head including a pair of signal terminals, to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; n terminating circuits terminated by 50 ohm; and n probe groups each comprising a port probe that is selectively connectable to either of the signal terminals or a respective one of the terminating circuits, and a pair of grounding probes facing each other across the port probe, each grounding probe being connected to the grounding terminal.

6 A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, where either of the total number of input ports and the total number of output ports is m, where m is not less than two, and the total number of input and output ports is not less than three, the said head including.

a signal terminal to which an RF measuring signal is input, and from which the RF measuring signal is output; a grounding terminal to be grounded; 2m-2 terminating circuits terminated by 50 ohm; a first probe group comprising a first port probe and a pair of grounding probes facing each other across the first port probe, the first port probe being connected to the signal terminal and each grounding probe being connected to the grounding terminal; and 2m-2 second probe groups each comprising a second port probe connected to a respective one of the terminating circuits and a pair of grounding probes facing each other across the second port probe and being connected to the grounding terminal, the above second probe groups being disposed at uniform intervals on both sides of the first probe group so as to define either a line or part of a circle, each second probe group position being adjustable in a direction in which the probe head contacts the semiconductor chip, so as to determine whether or not it can contact the semiconductor chip.

7 A probe head for measuring electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip, the total number of input and output ports being n, where n is an integer of not less than 3; the said head including: a pair of signal terminals, to which an RF measuring signal is input, and from which the RF signal is output; a grounding terminal to be grounded; n-2 terminating circuits terminated by 50 ohm; a pair of first contact groups, each comprising a first port contact and a pair of grounding contacts facing each other across the first port contact; n-2 second contact groups each comprising a second port contact and a pair of grounding contacts facing each other across the second port contact; a flexible membrane member whose rear surface is provided with the first and second contact groups in a central region thereof, and, in a peripheral region thereof, with an intermediate connecting terminal connected to each contact of the first and second contact groups; and a housing member biassing the central region of the membrane member away therefrom and holding the peripheral region of the membrane member, the housing member also supporting the signal terminals, which are connected to each first port contact of the first contact group through the intermediate connecting terminal of the membrane member, the grounding terminal being connected to each grounding contact of the first and

second contact groups through the intermediate connecting terminal, and the terminating circuits each being connected to the second port contact of the second contact group through the intermediate connecting terminal.

8. A method of using an RF signal to measure electrical properties of a multi-port circuit having at least one input port and at least one output port on a semiconductor chip of a semiconductor wafer, the total number of input and output ports being n, where n is an integer of not less than 3; the said method comprising the steps of: connecting a measuring signal output terminal and a measuring signal input terminal of a measuring apparatus to a pair of the ports of the multi-port circuit; and connecting terminating circuits terminated by a resistance of 50 n to all of the ports except the said pair.

9 A probe head for measuring electrical properties of multi-port circuit substantially as hereinbefore described with reference to Figures 1 and 2; or Figure 3; or Figure 4; or Figure 5; or Figure 6; or Figure 7; or Figures 8(a) and 8(b) of the accompanying drawings.