JPH02213677A - Cooling method - Google Patents

Abstract

PURPOSE:To prevent a tank from freezing therein and to stably cool a material to be cooled by cooling the material to be cooled by a second cooling liquid circulation passage connected to the upstream of a first cooling liquid circulation passage for preventing the tank from freezing. CONSTITUTION:A wafer 1 is cooled by a placing base 3, a probe 4 of a probe card 5 is brought into contact with the electrode of a semiconductor chip formed on the wafer 1 to inspect electric characteristics. A cooling method for the base 3 has steps of cooling cooling liquid 10 by a cooling coil 12 connected to a refrigerator 13 in a tank 11, supplying the liquid 10 to the base 3 via a liquid feed tube 14a by a pump 15 and thermally exchanging to cool the base 3. The thermally exchanged liquid 10 is returned into the tank 11 via a liquid feed tube 14b. A reverse feed tube 16 is connected to the midway of a tube for feeding the liquid 10 from the tank 11 to the base 3 to regulate the part of the liquid 10 to a predetermined quantity by a flowrate regulator 17 interposed on the way of the tube 15 to be returned. The flowrate and flowing speed of the tank 11 are increased to sufficiently agitate in the tank 11 thereby to suppress the freezing of the liquid 10, thereby accurately executing cooling of the base 3.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a cooling method.

(Prior Art) In the manufacture of semiconductor integrated circuits, a fine pattern is formed on the surface of a semiconductor wafer by performing a plurality of processes on the semiconductor wafer. The wafers on which these fine patterns are formed are inspected in an inspection process, and defective products are discarded on a semiconductor chip basis. In such an inspection process, the wafer may be inspected at a low temperature. This is because semiconductor devices are sometimes used at low temperatures in order to speed up computer calculations, so the wafer is cooled and inspected to suit the conditions of use. The technique of testing the electrical characteristics of a wafer in a cooled state was developed, for example, by the Japanese Patent Publication No. 62-3.
This method is disclosed in Japanese Patent No. 6378 and the like.

In order to cool the wafer in this manner, it is generally done by feeding a cooling liquid to a mounting table on which the wafer is mounted. This coolant is cooled by circulating the above-mentioned cooling liquid in a tank where heat exchange is performed, and this cooled liquid is sent by a pump through a flow pipe to a wafer mounting table to cool this mounting table. After that, the liquid is sent into the tank again.

In this way, the mounting table is cooled by circulating the cooling liquid between the tank and the mounting table using a pump.

(Problems to be Solved by the Invention) In order to sufficiently cool the mounting table, it is necessary to circulate the cooling liquid sufficiently in the tank that performs heat exchange. The cooling liquid needs to be circulated within the tank so that it flows near the cooling coil (evaporator) connected to the refrigerator. However, with the above conventional technology, it is not possible to flow more than a certain amount of liquid due to the fluid resistance of the flow conduit used to circulate between the tank and the mounting table, so the flow rate and flow rate of the cooling liquid in the tank are insufficient. Resulting in.

Therefore, the cooling liquid near the cooling coil may freeze, and in this case, only the cooling liquid in a portion where freezing does not occur, that is, a portion away from the cooling coil, cools the mounting table. As a result, the cooling liquid is circulated to the mounting table again before it is sufficiently heat exchanged, that is, cooled, in the tank, so there is a problem that the mounting table cannot be cooled to a desired temperature.

Further, in order to increase the degree of circulation of the coolant in the tank, for example, a stirring motor having a propeller-shaped rotation mechanism may be provided in the tank.

This method is expensive, requires a large cooling mechanism such as a tank, and has problems such as the cooling liquid being heated by the heat generated by the stirring motor.

The present invention has been made in response to the above-mentioned problems, and aims to provide a cooling method that is inexpensive and capable of stably cooling objects to be cooled by preventing freezing inside the tank without increasing the size. It is something.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a tank having a coolant cooling function, a cooled body provided in a first coolant circulation path to the tank,
A cooling method characterized in that the object to be cooled is cooled by a second coolant circulation path that prevents freezing in a tank that is connected upstream of the first coolant circulation path from the object to be cooled. This is what you get.

(Operation and Effect) That is, the present invention provides a tank having a cooling function for cooling liquid;
A cooled object provided in the first coolant circulation path to this tank, and a second cooling device that prevents freezing in a tank connected upstream of the first coolant circulation path from this cooled object. By cooling the object to be cooled through the liquid circulation path,
The second coolant circulation path can increase the flow rate in the tank, thereby increasing the degree of agitation in the tank and preventing freezing in the tank. By preventing this freezing, the coolant can stably flow through the first coolant circulation path, and the object to be cooled can be cooled with high accuracy.

(Example) Hereinafter, an example in which the method of the present invention is applied to an inspection apparatus for inspecting a semiconductor wafer will be described with reference to one drawing.

First, the configuration of the inspection device will be explained.

An inspection apparatus (2) is constructed that inspects the electrical characteristics of an object to be inspected, such as a semiconductor wafer (1), on a chip-by-chip basis. This inspection device (2) is provided with a mounting table (2) which is a cooled object that can be moved and rotated in x-y-z and θ. By placing and holding the wafer ω on the upper surface of the mounting table 1, it is possible to integrally move the wafer 2 in X-Y-Z and θ. Further, above the mounting table ■, there is provided a probe card ■ equipped with a probe for testing the electrical characteristics by contacting the electrodes (not shown) of the wafer ■.
Inspection is made possible by bringing the wafer (2) into contact with the probe of the probe card (2) by raising the mounting table (2). When inspecting the wafer ■ in this way, the wafer ■
The wafer is set at a low temperature and tested under the same conditions as adapted to the usage conditions of the finished IC.The means for setting the wafer at a low temperature is to use a mounting table, which is an object to be cooled, installed in the coolant circulation path. (2) The wafer (2) is indirectly cooled by cooling the mounting table (2) by feeding a coolant, such as an antifreeze liquid, through the coolant circulation path. Also,
As the antifreeze, an aqueous ethylene glycol solution is often used. To explain this cooling means specifically, the above-mentioned mounting stand■
A flow path 0 is provided through the inside, and a flow conduit (7a) is connected to the inlet side of the flow path (Q), and a flow conduit (7b) is connected to the outlet side of the flow path (Q). ) is formed into a flexible bellows shape because the above-mentioned mounting table (3) moves in the x-y-z-θ directions, etc. Therefore, the joint (8a) ( 8b) is provided.A cooling mechanism (2) is provided which is connected to such joints (8a) (8b) and performs heat exchange, that is, cooling, of the cooling liquid that cools the above-mentioned mounting table (2).This cooling mechanism ■ is,
A tank (11) for storing a cooling liquid (10), and a cooling coil (1) immersed in the cooling liquid (10) that exchanges heat, that is, cools the cooling liquid (10) in this tank (1 piece) to a predetermined temperature. evaporator) (12), and this cooling coil (12)
) to cool the cooling coil (12).
13). In addition, the above tank (11
), one end extends to near the bottom of the joint (8a
) is provided with a liquid feed pipe (14a) connected to the pipe. A pump (15) is interposed in the middle of this liquid feed pipe (14a) for feeding the cooled liquid (10) in the tank (11) to the mounting table (1) which is the object to be cooled. There is. Also,
The tank ( 1
1) is connected to a second coolant circulation path, such as a return pipe (I6), which prevents freezing in the cooling liquid. This reverse feed pipe (16).

Cooling liquid is sent to the mounting table ■ by the liquid sending pipe (14a).
It extends into the tank (11) with a flow rate adjustment II (17) interposed therebetween so as to return a portion of the liquid (10) into the tank (11). In addition, the liquid feed pipe (14a
) to the mounting table ■, one end of which is connected to the above-mentioned joint (
8b), and the other end reaches into the tank (11). In this way, the inspection device (2) equipped with the cooling mechanism 0 is constructed.

Next, the operation of the above-mentioned inspection apparatus (1) and the method of cooling the mounting table (2) will be explained.

First, a semiconductor wafer (2), which is an object to be inspected, is transported and placed on a mounting table (2) having an XY stage function using a transport mechanism such as a handling arm (not shown). After completing the 1st position alignment process.

The above-mentioned mounting table (2) is raised, and the probe of the probe card (2) is brought into contact with the electrode of the semiconductor chip formed on the surface of the wafer 0 to test the electrical characteristics. This test is carried out at a low temperature to suit the usage conditions of the finished IC. That is, the above-mentioned wafer (2) is cooled on the mounting table (4) set at a low temperature and then inspected.

The cooling method for the mounting table ■, which is the object to be cooled, is as follows:
1) Cooling liquid (10) stored and cooled inside is sent to the mounting table (2) and circulated to be cooled. That is, in the tank (11), the cooling liquid (10) is heated to a low temperature, for example, -1, by a cooling coil (12) connected to a refrigerator (13).
Cool the cooled liquid (10) to 5 to -25°C.
is supplied to the mounting table (2) through the liquid feed pipe (14a) and the flow pipe (7a) by driving the pump (15).

Then, it flows through the flow path 0 in this mounting table (2), and heat is exchanged by this circulation, so that the temperature of the mounting table (2) is set to about -1θ to 0°C. At this time, in order to exchange heat more efficiently,
It is preferable that the flow path 0 in the above-mentioned mounting table (3) is meandered and made long, and the heat-exchanged cooling liquid (10) is transferred to the above-mentioned tank (
11) Returned within. In this way, the cooling liquid (10) is circulated to cool the mounting table (1), but if the flow rate of the circulating cooling liquid (10) is small, the cooling liquid (10) is cooled.
) The flow rate and flow velocity of the cooling liquid (1o) in the inside are insufficient.

The flow rate of this cooling liquid (10) is limited to a certain amount or more because it is not possible to flow more than a certain amount of the cooling liquid (1o) due to the fluid resistance of the mounting table (2) and each piping.

In particular, the cooling liquid (1o) near the cooling coil (12) freezes, so only the unfrozen cooling liquid (10) in the tank (11) circulates between the mounting tables 0. , the cooling liquid (10) is sent toward the mounting table (2) before it is sufficiently cooled in the tank (11). Due to this, the cooling liquid (1o) cannot be cooled to the desired temperature. To solve this problem, the concentration of the cooling liquid (10), for example, an ethylene glycol aqueous solution, is increased to lower the freezing temperature. It is possible that However, when the concentration of ethylene glycol is increased, the specific heat of the antifreeze decreases, making it impossible to remove a sufficient amount of heat from the mounting table (2).

Generally, the specific heat of water is 1.0, but the specific heat of ethylene glycol is 0.5 to 0.6, and as the concentration of antifreeze increases, the specific heat decreases. In this example, the tank (11
) by returning a part of the cooling liquid (10) sent from the mounting table ■ to the tank (11).
11) is configured to increase the flow rate and flow velocity of the cooling liquid (10) in the cooling liquid (10). That is, in the middle of the pipe that transports the cooling liquid (10) from the tank (11) to the mounting table (2), for example, between the pump (15) and the joint (8a) of the liquid transport pipe (14a),
The reverse feed pipe (16) extending to the tank (11) is connected to the cooling liquid (1) that is being fed through the liquid feed pipe (14a).
0) is returned to the tank (11).

A part of the cooling liquid (10) to be returned is transferred to the above-mentioned return pipe (
16) is adjusted to a predetermined amount by a flow rate regulator (17) interposed in the middle, and then returned.

To explain specifically, 1. For example, Figure 2 shows an example of the performance characteristics of a centrifugal pump, but the conditions conventionally used are:
Discharge pressure at the liquid feed pipe (14a) section: 0.78 kg/dG,
The flow rate was 0.5Q/win. On the other hand, in this embodiment, the pressure of the coolant (10) flowing through the pump (15) is adjusted to 0.7 kg by adjusting the flow rate regulator (17).
A portion of the cooling liquid (10) is returned to the tank (11) via the return pipe (16) so that the temperature drops to /aJG.

Then, the cooling liquid (10) flowing inside the pump (15)
As can be seen from FIG. 2, the flow rate is 2Q/lll1n, which is four times the flow rate in the conventional case. This coolant (1
By increasing the flow rate of the cooling liquid (10) in the tank (11), the flow rate and flow velocity in the tank (11) increase, and the inside of the tank (11) can be sufficiently stirred. ) can be prevented from freezing. Since this freezing can be suppressed, heat exchange in the tank (11), that is, cooling of the cooling liquid (10) can be performed stably, and the cooling of the mounting table (1) can be performed with high precision. Here, the cooling liquid (10
) is 2 Q/win.

A part of this cooling liquid (10) is transferred to the reverse pipe (
16). Generally, since the flow rate is proportional to the square root of the pressure difference due to fluid resistance, the decrease in the flow rate of the cooling liquid (10) which is the joint (8a) and is sent to the external load, ie, the mounting table (1), is extremely small. That is, the flow rate of the cooling liquid (10) supplied to the mounting table (1) is 0.47Q/win,
The flow rate returning from the return pipe (16) is 2.0-0.47=
1.53Q/win. However, the above tank (
11) Since the amount of antifreeze passing through the tank (11) has increased four times, freezing of the coolant (10) in the tank (11) can be prevented, and sufficient heat exchange has become possible. Furthermore, the concentration of antifreeze, such as ethylene glycol, can be lowered. This is compared to the conventional ethylene glycol concentration of, for example, 40% (freezing temperature of approximately -25°C) to 30%.
% (freezing temperature approximately -15℃), the specific heat was 0.75Kca12/kg℃ to 0.85℃.
Kcaff/kg'c can be increased, and as the specific heat increases, the heat exchange efficiency, that is, the cooling efficiency, in the above-mentioned mounting table (3) increases, making it possible to perform highly reliable and stable cooling control. becomes.

In this way, the cooling liquid (10) at a stable temperature is always supplied to the mounting table (1) via the liquid supply pipe (14a) and the flow pipe (7a), and then ) to the tank (11) for cooling, and the wafer (2) placed on the mounting table (2) is inspected at low temperature.

In the above embodiment, the object to be cooled is an example of a mounting table for an inspection device, but any object that requires cooling may be used, such as an etching device, an ashing device,
A similar effect can be obtained with a film forming apparatus or the like.

As described above, this embodiment includes a tank having a cooling function for cooling liquid, an object to be cooled provided in a first cooling liquid circulation path to this tank, and a cooling object connected to the first cooling object from this object to be cooled. It consists of a second coolant circulation path that is connected upstream of the liquid circulation path and prevents freezing in the tank. In other words, when the cooling liquid cooled by the cooling mechanism is sent to the object to be cooled for cooling, a part of the cooling liquid sent to the object to be cooled is returned to the cooling mechanism to cool the object. The flow rate of the cooling liquid within the mechanism increases, and the degree of agitation can be increased. Therefore, it is possible to prevent the coolant from freezing within the cooling mechanism, and it is possible to increase the degree of heat exchange of the coolant. This makes it possible to accurately and stably cool the object to be cooled.

Also, since it only returns part of the coolant,
The device can be constructed at low cost and without increasing its size.

[Brief explanation of the drawing]

1 is a block diagram of an inspection device and a cooling mechanism for explaining an embodiment of the method of the present invention, and FIG. 2 is a diagram showing an example of the pump performance characteristics of FIG. 1. 3... Placement table 9... Cooling mechanism 10...
・Cooling liquid 11... Tank 15... Pump 16... Reverse feed pipe patent applicant Tokyo Electron Ltd.; Tomo I (1/M Gun

Claims (1)

[Claims] A tank having a coolant cooling function, a cooled body provided in a first coolant circulation path to this tank, and a tank connected upstream of the first coolant circulation path from this cooled body. A cooling method characterized in that the object to be cooled is cooled by a second cooling liquid circulation path that prevents freezing inside the object.