JPH05196639A - Probe device - Google Patents

Abstract

PURPOSE:To provide a probe device for surely preventing collision between a sample to be detected and a probe needle. CONSTITUTION:The height of a probe needle is recognized based on the information on the height of a probe needle 47 read from a memory element provided on a probe card holder 22, and a semiconductor wafer is driven in such a way that it first approaches the probe needle 47 at high speed in a first interval and then at low speed in a second interval, and an electrode pad is made into contact with the probe needle 47 at a contact point. The height of the contact point at a first wafer is detected, and a next wafer approaches the probe needle 47 at high speed in the second interval longer than the first one, based on the information on the height of the contact point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe device for measuring the electrical characteristics of a device under test such as a semiconductor device.

[0002]

2. Description of the Related Art As is well known, many semiconductor devices are formed on a semiconductor wafer by using a precision photo transfer technique or the like.
After this, the wafer is cut into individual semiconductor devices. In the manufacturing process of such a semiconductor device, conventionally, a probe device is used to perform a test determination of the electrical characteristics of a semi-finished semiconductor device in a semiconductor wafer state, and the result of this test measurement is determined to be a non-defective product. It is being done to improve productivity by sending only waste products to subsequent processes such as packaging.

The probe apparatus includes a wafer holder that is movable in the XYZ-θ directions, and a large number of probes corresponding to the electrode pads of semiconductor devices are mounted on the wafer holder. A probe card with a needle is fixed. Then, the semiconductor wafer is set on the wafer holder, the wafer holder is driven to bring the probe needle into contact with the electrode of the semiconductor device, and the test measurement is performed by the tester via the probe needle.

In such a probe device, the height of the probe needle tip differs depending on the probe card. Therefore, the height of the probe needle tip is recognized by raising the semiconductor wafer on the wafer holding table at a very low speed before starting the measurement and detecting the position (contact point) where the probe needle tip contacts the semiconductor wafer. Is being done. However, in such a height recognizing step of the probe needle tip, if the wafer holder is raised at a low speed from the home position (lowermost position), it takes a very long time to detect the contact position. For this reason, the semiconductor wafer is usually raised at a high speed to a height where the probe needle tip does not exist, and then the semiconductor wafer is raised at a low speed.

[0005]

In recent years, semiconductor devices tend to be highly integrated, and the electrode pads of semiconductor devices also tend to be narrowed in pitch and increased in number. Therefore, instead of the probe card 2 in which the probe needles 1 are arranged obliquely as shown in FIG. 1A, the probe card 1 in which the probe needles 1a are arranged almost vertically as shown in FIG. 1B. 2a is being developed and is being put to practical use. However, in the probe card 2a in which the probe needle 1a is arranged almost vertically, when the probe card 2a is fixed to the probe device, the height of the probe needle tip is significantly larger than that of the conventional probe card 2, for example, about several centimeters. It is in a low position (indicated by h in the figure). Therefore, in the above-described step of recognizing the height of the probe needle tip, it is necessary to set the amount of rise of the wafer holding table 3 for holding a semiconductor wafer or the like to be small, but if this setting is incorrect, the height of the probe needle tip will be decreased. At the time of recognition, there is a possibility that an object to be inspected such as a semiconductor wafer may collide with a probe needle and damage the semiconductor wafer or the probe card.

An object of the present invention is to provide a probe device capable of surely preventing a collision between an object to be inspected and a probe needle and preventing damage to the object to be inspected and a probe card. Is.

[0007]

A probe device according to an aspect of the present invention includes a probe card means having a probe needle and a storage element having height information of the probe needle, and a probe card means under the probe card means. The height of the probe needle of the probe card means is recognized by means for supporting the inspection body and vertically moving the detected body and the information read from the storage element of the probe card means, It is provided with a means for bringing the object to be inspected into contact with the probe needle by controlling the distance between the object to be inspected and the tip of the probe needle and driving them so as to approach each other.

A probe device according to another aspect of the present invention has a probe card means having a probe needle and a storage means having height information of the probe needle, and a plurality of electrode pads below the probe card means. The height of the probe needle of the probe card means is supported by means for supporting a wafer having at least one semiconductor element, which is capable of moving the wafer in the vertical direction, and information read from the memory element of the probe card means. Recognizing and controlling the distance between the electrode pad of the wafer and the tip of the probe needle to drive the supporting means so that the electrode pad comes into contact with the probe needle at a contact point at a high speed and then at a low speed. It is equipped with.

A probe apparatus according to still another aspect of the present invention is a probe card means having a probe needle and a first storage means having height information of the probe needle, and a position below the probe card means. Supporting means on which a wafer having at least one semiconductor element having a plurality of electrode pads at the initial position is placed, and driving means for vertically moving the supporting means between the initial position and the inspection position. Recognizing the height of the probe needle of the probe card means on the basis of the information read from the storage element of the probe card means, controlling the driving means to move the support means first at the first distance at high speed, Control means for driving the electrode pad to contact the probe needle at a contact point by driving the distance of 2 at a low speed to approach the inspection position;
Second, the height of the contact point on the first wafer is detected, and the height information of the contact point is stored.
Storage means, means for inspecting a semiconductor element via a probe needle that is in contact with the electrode pad, and supporting means for supporting the wafer on which the semiconductor element has been inspected by the driving means are returned to the initial position. And removing the wafer that has been inspected, and mounting the next wafer to be inspected on the supporting means, wherein the control means is based on the stored contact point height information,
The control means is controlled to cause the supporting means to approach the probe card means at a high speed at a second distance longer than the first distance.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a probe apparatus for performing test measurement of a semiconductor device formed on a semiconductor wafer will be described below with reference to the drawings. First, the overall configuration of the probe device will be schematically described with reference to FIG.

In FIG. 2, reference numeral 10 indicates a probe apparatus main body, and a main stage 11 is provided at substantially the center. The semiconductor wafer 1 is mounted on the main stage 11.
2, a mounting table 13 for measurement described later is attached. The main stage 11 is movable in the horizontal direction along with the mounting table 13 in the X and Y directions. A probe mechanism 1 to be described later is provided above the mounting table 13.
4 are provided. Although not shown, the device body 10
An alignment unit is provided on the front side of the center of the. This unit is provided with a camera as an image recognition device for alignment. The mounting table 13 is moved below the camera for alignment. An auto loader 15 is provided on the right side of the apparatus main body 10, and a probe card exchange 16 is provided on the left side.

In the autoloader 15, a wafer cassette 17 that accommodates a large number of semiconductor wafers 12 at a predetermined interval in the vertical direction is exchangeably arranged on a cassette mounting table 18. The wafer cassette 17 and the mounting table 1 described above.
3 is a loader stage 19 movable in a horizontal plane
And a wafer handling arm 20 that can be driven by a Y-direction drive mechanism and a Z-direction lift mechanism (not shown). When the semiconductor wafer 12 is subjected to the probe inspection, the wafer is transferred to the vicinity of the mounting table 13 by the loader stage 19, and the mounting table 13 is mounted by the handling arm 20.
Moved to the top. After the inspection, the wafer is transferred onto the loader stage 19 by the handling arm 20 and transferred to the wafer cassette 17 by the loader stage 19.

A probe card 21 is attached to a card holder 22.
Assembly or probe card means 23 mounted on the
Are stored in the storage rack 24 at a predetermined interval in the vertical direction.

Reference numeral 25 denotes a microscope or a television camera for monitoring the wafer located below and the tip of the probe needle of the probe card 21 through an opening formed in the center of the probe card 21 and the card holder 22. The automatic probe replacement operation of the probe device as described above is described, for example, in US Pat. 4, 966, 520. The mounting table 13 will be described in more detail with reference to FIG.

The mounting table 13 extends in the X direction 2
X stage 31 that can move in the X direction along the rails of the book
a and 2 extended on the X stage 31a in the Y direction
Y stage 31 movable in the Y direction along the rails of the book
b and. The X and Y stages 31a and 31b are
It is driven in a horizontal plane in the X and Y directions by a conventional drive mechanism including a pulse motor and the like. Y stage 31b
The chuck 32 mounted on the top is driven in the vertical direction (Z direction) by a conventional lifting mechanism, and is rotated by a conventional rotating mechanism around a center line passing through the center thereof and parallel to the Z axis. The drive mechanism, the elevating mechanism, and the rotating mechanism are denoted by reference numerals 54, 55, and 56 in FIG. 6, respectively, and their respective drives are controlled by a control system described later.

A lifting mechanism 34 is provided on the side surface of the Y stage 31b.
Is fixed. The elevating mechanism 34 holds a movable camera 33 that can be vertically moved. The moving camera 33 includes a high magnification section 33a and a low magnification section 33b.

On the side surface of the chuck 32, a small piece 35 which is horizontally projected in the radial direction is fixed. This small piece 35
Is a strip-shaped transparent plate on the surface of which a target 35a defined by the center of a cross mark drawn using a conductive thin film such as an ITO (indium tin oxide) thin film or chrome is formed. This functions as a reference point for detection by the camera 33. Around the cross-shaped thin film, a conductive transparent thin film such as I
A thin film of TO is provided. The conductive transparent thin film is provided to enable the electrostatic capacitance sensor to detect the position in the Z direction.

Small piece 35 on which target 35a is formed
Is movable on the optical axis of the high-magnification portion of the moving camera 33 by the rotation of the chuck 32 and can be retracted from there. The small piece 35 may also be configured to be removably attached to the chuck 32.

The alignment operation of the wafer by the mounting table 13 having the above-mentioned structure is performed in Japanese Patent Application Nos. 3-216068 and 3-2.
Since it is described in detail in No. 16067, it is omitted here. The probe card-card holder assembly 23,
This will be described in detail with reference to FIGS. 4 and 5.

In FIG. 4, reference numeral 40 denotes an insert ring mounted on the upper part of the apparatus main body 10 (see FIG. 2), and a contact ring 41 is mounted on the step portion on the peripheral side surface of the central opening. The contact ring 41 is both of these 4
The mounting position is defined by two positioning pins provided at positions 0 and 41 in the radial direction. A test head 42 is provided on the upper surface of the contact ring 41 in a state of being electrically connected by a contact arranged between them. The test head 42 is electrically connected to a known tester 43, and the printed circuit board 40a of the insert ring 40 is electrically connected to a control system 44, which will be described later, so as to supply an output signal to them. A support ring 45 is provided on the apparatus main body 10 so as to be movable in the vertical direction.
In the upper position, the peripheral portion of the card holder 22 is sandwiched between the card holder 22 and the insert ring 40, and the assembly 23 is replaceably attached to the lower side of the contact ring 41. The assembly 23 is attached at a predetermined position by two positioning pins arranged between the three members 40, 22, 45.

On the upper surface of the probe card 21, a substrate 46 made of, for example, a printed substrate is provided.
In the central portion of the substrate 46, a large number of probe needles 47 are provided so as to be arranged substantially vertically downward, corresponding to the electrode pads of the semiconductor device on the semiconductor wafer 12. In this case, even if the probe needle 47 is arranged corresponding to the electrode pad of one semiconductor device,
It may be arranged corresponding to the electrode pads of a plurality of semiconductor devices. The probe needle 47 extends vertically downward through the central opening of the card holder 22, and has a tip slightly protruding from the lower surface of a cylindrical block projecting from the lower surface of the card holder 22. The printed circuit board on the upper surface of the probe card 21 is electrically connected to the contacts provided on the lower surface of the contact ring 41 when the assembly 23 is loaded in the apparatus main body 10, and as a result, the printed circuit board, and thus the probe. The needle 47 is electrically connected to the tester 43 described above via the test head 42.

On the upper surface of the probe card-card holder assembly 23, memory means 48 (first storage means) and electrical connecting means 49 are provided as shown in FIG. The memory means 48 and the electrical connection means 49 are provided on the card holder 22 in this embodiment, but may be provided on the upper surface of the probe card 21. The memory means 48 is composed of two memory elements 48a, preferably two EEPs.
ROM is used. One ROM 48a stores various information about the probe card 21 set before the test, and the other ROM 48a stores various information about the probe card 21 rewritten by the test. The information includes, in addition to Z-direction movement data that controls movement of the mounting table 13 in the Z-direction, for example, the number of contacts (total and trip), relative position of the needle, probe card serial number, probe card type,
Number of pins, number of multis, multilocation, needlework execution timing and number of contacts, overdrive allowance, execution of slide after contact, execution of needlework, implementation of alarm and rejection in case of defective probe card. The Z-direction movement data includes the distance or height Hh at which the chuck 32 having the semiconductor wafer 12 loaded thereon is moved upward at high speed and the chuck 32 has a predetermined distance, that is, the height H.
For example, the height limit for stopping the drive when moving upward. Here, when testing a semiconductor device, that is, an element, the upward movement of the chuck 32 is performed at high speed up to a predetermined height Hh near the probe card 21 and then at low speed as described in the related art. The height Hl at which the probe needle 47 contacts the terminal of the semiconductor element.
Stopped when (contact point) is detected.
Actually, in order to secure the electrical contact between the probe needle 47 and the electrical pad of the semiconductor element, the probe needle 47 is stopped slightly above the contact point (overdrive). The limit distance H is H = high speed distance Hh + low speed distance Hl + allowable distance ΔH. That is, even if the semiconductor wafer is moved by a predetermined distance H, the contact point cannot be detected.
It means that an abnormality has occurred in either of the above, and it is necessary to stop the measurement. This high-speed distance H
It is preferable that h is set as close as possible to the distance between the upper surface of the semiconductor wafer 12 and the lower end of the probe needle 47 in order to shorten the operation time, but if it is too close, the speed remains high. Are likely to come into contact with each other and be damaged, so that they are set with a margin in consideration of manufacturing errors of the semiconductor wafer 12 and the assembly 23. In this preferred embodiment, Hh is about 20 mm and Hl is 3-4 mm.
Is set to.

The electrical connecting means 49 comprises a plurality of contact holes, is electrically connected to the memory means 48, and is electrically connected to the printed circuit board 40a of the insert ring 40.
The contact pins projecting from the lower surface of are inserted when the assembly 23 is mounted and electrically contact with them. As a result, at the same time when the assembly 23 is attached to the apparatus main body 10,
The memory means 48 is electrically connected to the control system 44.

The control system 44 has a CPU 50 having a memory as shown in FIG. This CPU has Z
Directional movement control circuit 51 and XY direction movement control circuit 52
And the θ direction movement control circuit 53 are connected to each other.
These control circuits are connected to an elevating mechanism 54, a driving mechanism 55, and a rotating mechanism 56, which move the mounting table 13 shown in FIG. 3, respectively. As a result, the CPU 50
The memory means 48, the Z-direction movement control circuit 51,
X-Y direction movement control circuit 52 and θ direction movement control circuit 5
The control described later with respect to 3 is performed.

Next, the main drive control of the mounting table 13 by the control system 44 will be described with reference to FIG. The aggregate 23 is conveyed from the probe card exchanger 16 to a position below the insert ring 40 by a conveying mechanism (not shown), and then the support ring 45 moves up to sandwich the aggregate 23 between the insert ring 40 and the support ring 45. .. Thus, the probe card 21. The device body 10 is loaded (S1). At this time, the memory means 48 of the assembly 23 is controlled by the control system 44 via the printed board 40a of the insert ring 40.
In addition, the probe needle 47 is connected to the tester 43 via the contact ring 41 and the test head 42, respectively. As a result, the high speed height data (about 20 mm) stored in the memory means 48 is input to the CPU 50 (S2). Next or before this, the first semiconductor wafer 12 is transferred from the autoloader 15 onto the chuck 32, XYθ alignment is performed, and one or a plurality of parts are first inspected immediately below the contact ring 41 with high accuracy. The semiconductor element of is positioned. Based on the read information in step S2, the elevating mechanism 54 is driven via the Z-direction movement control circuit 51 by a command from the CPU 50, and the chuck 32, that is, the semiconductor wafer 12 is driven.
Is at high speed (10 mm) for high speed distance Hh (about 20 mm).
/ Minute to 20 mm / minute) to approach the lower end of the probe needle 47 of the probe card 21 (S3). Subsequently, the chuck 32 is further raised at a low speed (500 μm / sec) (S4), and when it is raised about 3 to 4 mm, the contact point is detected when it is normal (S5). The height information of this contact point is stored in the memory (second storage means) of the CPU 50 (S6). That is, the height information of the probe card 21 currently used is stored in the control system 44 side. The detection of the contact point at this time can be performed by detecting a current flowing between the electrode pad of the semiconductor element and the probe needle 47 by electrical contact, as in the conventional technique. If the ascent of the chuck 32 reaches the limit distance stored in the memory means 48, the control system 44 outputs an abnormal signal Z.
The signal is sent to the direction movement control circuit 51, and the driving of the lifting mechanism 54 is stopped (S7). When a contact point is detected,
The chuck 32 is further raised at a low speed by about 50 μm,
The electrical contact between the electrode pad and the probe needle 47 is made more reliable (S8). In this state, electrical information from the electrode pad is output to the tester 43 via the probe needle 47 or the like, and the electrical characteristics of this semiconductor element are inspected. When the inspection is completed, the chuck 32 moves slowly at a low speed (about 500
μm) and the probe needle 47 is separated from the contact point (S9). Then, based on the information stored in the memory means 48 or the information stored in the CPU 50 in advance, the semiconductor wafer 12 is XY.
The semiconductor element to be tested next by the mounting table 13 via the direction movement control circuit 52 and the drive mechanism 55 is the probe needle 4.
It is moved in the XY directions so that it is directly below 7 (S1
0). Then, the chuck 32 is lifted at the same low speed as above (S11), and the contact point is detected (S12). Then, the semiconductor device is tested. When the steps (S8 to S12) are repeated and the test of all the semiconductor elements formed on one semiconductor wafer 12 is completed (S13), necessary data such as the number of contacts is stored in the memory means 48 via the CPU 50. Stored in. After this, this tested semiconductor wafer 1
2 is transferred to the autoloader 15, and instead, the second semiconductor wafer 12 is transferred onto the chuck 32, and XYθ alignment is performed in the same manner as the above step (S1).
5). The high-speed height Hh is corrected by the CPU 50 based on the contact point information stored in step S6, and the high-speed height Hh is corrected slightly below the contact point (about 500 μm).
The high speed height Hh is set high up to the position m). For example, in the first semiconductor wafer 12, the high speed distance Hh is 20
mm, and if the low speed distance from this point to the contact point is 3 mm, the high speed height Hh is 20 mm + (3
mm-500 μm). Based on this reset value, the chuck 32 has a contact point of 500
Ascending at the same high speed as before (S16), and thereafter, in order to detect the contact point,
The speed is increased at the same low speed as above (S17). After this, the second semiconductor wafer 12 is inspected through the same steps as steps S5 to S14. In the case of inspecting the second and subsequent semiconductor wafers 12, the height information of the contact points obtained on the first semiconductor wafer 12 is used, and writing of this information is not performed. Alternatively, it may be sequentially rewritten.

The first contact of the semiconductor wafer 12 within the range in which the contact between the semiconductor wafer 12 and the probe needle 47 can be reliably prevented by the combination of the assembly 23 to which the memory means 48 is added as described above and the control system 44. Based on the point measurement, the second and subsequent semiconductor wafers 12
The high-speed moving distance can be increased.

FIG. 8 schematically shows the structure of a probe apparatus according to another embodiment. The same parts as those in the above-mentioned embodiment are designated by the same reference numerals. In this embodiment, for example, a bar code 60 is provided on the aggregate 23 as a display means of the identification mark. On the other hand, the probe device is provided with a barcode reader 61 as a means for recognizing the identification mark by reading the barcode 60, and further stores information on the probe card of the identification mark read from the barcode 60. Storage device 50b for the CPU 50a
It is provided separately from. The storage device 50b stores at least information about the height of the probe needle as information about the probe card specified by each identification mark.

Then, the probe device reads the bar code 60 of the assembly 23 by the bar code reader 61, the CPU 50b identifies the probe card, reads the information about the height of the corresponding probe needle from the storage device 50b, and the probe device Recognizing the approximate position of the needle tip,
Similar to the above-described embodiment, it is configured to control the vertical movement of the chuck 32. Also in the embodiment configured in this way, it is possible to obtain the same effects as the above-described embodiments. In addition, as a display means of the identification mark,
As with the barcode 60, the ASCII code or the like may be replaced with the barcode reader 31 to use a character recognition mechanism or the like.

FIG. 9 shows an embodiment in which a jumper wire 70 is provided on the probe card as a means for displaying an identification mark. That is, the assembly 23 is provided with a plurality of jumper wires 70, and the identification mark is displayed by a combination of the open and short of the jumper wires 70. In addition, the probe device,
Detection mechanism 7 for detecting the states of these jumper wires 70
1 is provided. Then, the CPU 50a reads the information regarding the height of the corresponding probe needle from the storage device 50b from the state of these jumper wires 70 as in the above-described embodiment, and recognizes the approximate position of the tip of the probe needle, Similar to the above-described embodiment, the vertical movement of the chuck 32 is controlled. Also in this embodiment, the same effect as that of the above-described embodiment can be obtained.

In addition to the above, the identification means provided on the probe card means 23 is, for example, a combination of transmitted light and reflected light for each predetermined area, or a combination of letters, numbers, symbols, etc. for identifying solids. Anything that can be used can be used.
In addition to the information about the height of the probe needle of the probe card, the storage device 50b stores various information about the probe card described above, and various controls can be performed according to the information.

[0031]

As described above, according to the probe device of the present invention, it is possible to reliably prevent the collision between the object to be inspected and the probe needle, and to prevent the object to be inspected and the probe card from being damaged. be able to.

[Brief description of drawings]

FIG. 1 is a view for explaining a difference in height of a needle tip due to a difference in arrangement of conventional probe needles.

FIG. 2 is a diagram showing the overall configuration of a probe device according to an embodiment of the present invention.

FIG. 3 is a perspective view showing the configuration of the measurement mounting table shown in FIG.

FIG. 4 is a diagram showing the probe mechanism shown in FIG.

FIG. 5 is a perspective view showing a part of a probe mechanism.

FIG. 6 is a block diagram showing a control system of a mounting table for measurement.

FIG. 7 is a flowchart illustrating a wafer inspection under the control of the control system shown in FIG.

FIG. 8 is a schematic diagram for explaining a probe device according to another embodiment.

FIG. 9 is a schematic view for explaining a probe device according to still another embodiment.

[Explanation of symbols]

10 ... Probe device, 12 ... Semiconductor wafer, 13 ... Measurement mounting table, 14 ... Probe mechanism, 21 ... Probe card, 22 ... Card holder 22, 23 ... Probe card-card holder assembly, 43 ... Tester, 44 ... Control system , 47 ... Probe needle, 48 ... Memory means, 50 ... C
PU

Claims (3)

[Claims] 1. A probe card having a probe needle and a storage element having height information of the probe needle, an object to be inspected below the probe card means, and the object to be inspected in a vertical direction. The height of the probe needle of the probe card means is recognized based on the movable means and the information read from the storage element of the probe card means, and the supporting means is approached by controlling the distance between the DUT and the probe needle tip. A probe device comprising means for bringing an object to be inspected and a probe needle into contact with each other by driving so as to drive the probe needle. 2. A probe card means having a probe needle and a storage means having height information of the probe needle, and at least one semiconductor element having a plurality of electrode pads below the probe card means. The wafer having the wafer is supported and the height of the probe needle of the probe card means is recognized by means of the means capable of moving the wafer in the vertical direction and the information read from the storage element of the probe card means, and the supporting means A probe apparatus comprising: a means for controlling the distance between the electrode pad and the tip of the probe needle so that the electrode pad is brought into contact with the probe needle at a contact point by driving the electrode pad so that the probe pad approaches first at high speed and then at low speed. 3. A probe card means having a probe needle and a first storage means having height information of the probe needle, and a plurality of electrode pads located below the probe card means and in an initial position. A support means on which a wafer having at least one semiconductor element is placed, a drive means for vertically moving the support means between an initial position and an inspection position, and a storage element of the probe card means. The height of the probe needle of the probe card means is recognized by the information obtained, and the driving means is controlled to first set the supporting means first.
At a high speed and then a second distance at a low speed so as to approach the inspection position so as to bring the electrode pad into contact with the probe needle at a contact point, and a height of the contact point on the first wafer. Second, which detects the height and stores the height information of this contact point
Storage means, means for inspecting a semiconductor element via a probe needle that is in contact with the electrode pad, and support means for supporting the wafer on which the semiconductor element has been inspected by the driving means are returned to the initial position, and then the support means And a means for mounting a wafer to be inspected next on a supporting means while removing the inspected wafer, the control means based on the stored contact point height information, and the control means. Is controlled to cause the supporting means to approach the probe card means at a high speed at a second distance that is longer than the first distance.