JP3143733B2 - Method and apparatus for detecting thickness of semiconductor thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for detecting the thickness of a metal thin film formed by a CVD (chemical vapor deposition) technique or the like.

[0002]

2. Description of the Related Art According to microfabrication technology such as CVD (Chemical Vapor Deposition) technology which has remarkably progressed in recent years, it is possible to form a metal thin film on the order of tens of angstroms, and to detect the thickness of the metal thin film. A method and apparatus is needed.

[0002]

However, heretofore, there has been no method and apparatus for simply and reliably detecting the thickness of a metal thin film on the order of tens of angstroms. Therefore, an object of the present invention is to form a thin film thermocouple on the order of tens of angstroms by a fine processing technique such as a CVD (chemical vapor deposition) technique and utilize the characteristics of the thermocouple formed by the thin film. An object of the present invention is to provide a method and an apparatus for easily and reliably detecting the thickness of a metal thin film on the order of tens of angstroms.

[0003]

A feature of the present invention is that the magnitude of the thermoelectromotive force generated in the thermocouple by the heat applied to the thermocouple in which the two kinds of minute metal thin films are joined is reduced. The thickness of the metal thin film constituting the thermocouple is detected based on the thickness.

[0004]

DETAILED DESCRIPTION OF THE INVENTION A semiconductor chip is currently a thickness of several hundred [mu] m, the length of one side over the tip about several mm, transistors, resistors, semiconductor devices such as capacitors 10 ⁶ or more, provided ing. And, by mounting this highly integrated semiconductor chip at high density, the speed of signal transmission is increased. Therefore, the heat generation density reaches several tens of W / cm ² at present and is expected to increase further in the future. The semiconductor chip generates high heat in this way, but unless the temperature is controlled so as to cool the semiconductor chip to a predetermined temperature or lower, the reliability of the operation of the semiconductor element cannot be ensured. Conventionally, as a technique for cooling a semiconductor element on a semiconductor chip, a technique using a fluid such as a cooling liquid or air as a cooling medium is generally used.

However, in the conventional cooling method using a fluid as in the conventional example, it takes a relatively long time from the detection of the temperature to the cooling by changing the flow velocity of the fluid, and the efficiency is low. There is. In addition, a mechanism for flowing a cooling liquid or air is required, and there is a problem that the size of the entire apparatus is increased.

[0006] On the other hand, when a temperature difference occurs at the junction of two metals joined together, an electromotive force is generated (thermal electromotive effect). As described above, a thermocouple is configured by joining two kinds of metals and generating a thermoelectromotive force due to a temperature difference. The temperature can be detected from the magnitude of the thermoelectromotive force generated in the thermocouple. As a temperature detection method using a thermocouple in which two kinds of metals are joined, a large thermocouple is conventionally used.

On the other hand, according to microfabrication technology such as CVD (Chemical Vapor Deposition) technology, which has made remarkable progress in recent years, it is possible to form a thin film thermocouple on the order of tens of angstroms. It has become.

However, in such a thin film, since the movement of electrons is restricted, the relationship between the film thickness and the magnitude of the thermoelectromotive force (thermoelectromotive characteristic) is different from that of the known large thermocouple. It is expected to be different. Unless the thermoelectromotive force characteristics are elucidated, practical use is impossible.

The present inventors have clarified the thermoelectromotive force characteristics of a thin-film thermocouple by quantum mechanical research.
That is, by simultaneously solving the Schrodinger equation and the Poisson equation shown in Table 1 below, the behavior of the electrons moving on the joint surface between the two metals could be analyzed.

[Table 1] In this Table 1, V is the electric potential, e is the elementary charge, ε is the dielectric constant of vacuum, n is the charge density, h is the Planck constant divided by 2π, m is the mass of the electron, and Ψ is the wave function. .

FIG. 3 is a graph showing the relationship between the film thickness and the thermoelectromotive force obtained by the present inventors.
In this graph, the horizontal axis represents the film thickness, and the vertical axis represents the thermoelectromotive force. The thermoelectromotive force on the vertical axis represents the ratio of the thermoelectromotive force when the film thickness is changed with respect to a case where the thickness is sufficient (1000 angstrom order or more).
This graph shows experimental values confirmed by the experiments of the present inventors and theoretical values obtained by the quantum mechanical research of the present inventors.

From the graph of FIG. 3, it was found that the theoretical value based on the quantum mechanical research by the present inventors was almost equal to the experimental value, and the theory was correct. As a result, a phenomenon in which the thermoelectromotive force of the thin film thermocouple was suspended and decreased as the film thickness was reduced could be quantitatively determined. Thus, the thin film thermocouple was actually usable. The present inventors have invented a method for simultaneously detecting and cooling the temperature of an electronic device based on the result.

That is, a thermocouple in which two kinds of thin metal films are bonded is provided in an electronic device, and a thermoelectromotive force is generated in the thermocouple by the heat of the electronic device. Then, the electronic device is cooled by applying a voltage from the power supply to the thermocouple in a direction opposite to the thermoelectromotive force in accordance with the detected temperature. In addition, it proposes to measure the thickness of the metal thin film by using the electromotive force characteristics of a thermocouple in which two kinds of minute metal thin films are joined.

An embodiment relating to a temperature detection and a cooling system of an electronic device will be described below with reference to FIGS. First Embodiment First, a first embodiment will be described with reference to FIGS. The first embodiment is a method and apparatus for controlling the temperature of an electronic device that detects the temperature of the electronic device and cools the electronic device according to the detected temperature. FIG. 1 shows a temperature control device for an electronic device according to a first embodiment. The temperature control device includes a thermocouple (hereinafter, referred to as a micro-thin film thermocouple) 2 composed of a fine thin film provided on a surface of a semiconductor chip 1 as an electronic device, for example.
A power supply control circuit 4 as power supply driving means connected to the thermocouple 2; and a power supply 5 driven by the power supply drive circuit 4.
And Here, the micro thin-film thermocouple 2 is C
The semiconductor chip 1 is formed by laminating two kinds of fine metal thin films 2A and 2B on a semiconductor chip 1 by a fine processing technique such as VD.

The semiconductor chip is mounted with a large number of semiconductor elements such as transistors, resistors, capacitors and the like connected by lead wires 6. The semiconductor chip 1 of the present embodiment is a super LSI (ultra large scale integrated circuit). Semiconductor chip 1
In view of the microscopic view, the device has an actual heat generating portion that actually generates heat, and a heat conductive portion that merely conducts heat generated in the actual heat generating portion. In the present embodiment, the micro thin-film thermocouple 2 is formed only in the actual heating portion of the semiconductor chip 1 (see FIG. 2), so that the cooling efficiency is further improved. FIG. 1 exemplifies a lead wire 6 as an actual heating portion forming the micro thin-film thermocouple 2. The lead wire 6 of the present embodiment has a width of 1 μm. Reference numeral 7 denotes a semiconductor substrate, and reference numeral 8 denotes an insulating layer. Semiconductor chip 1 of the present embodiment
Is a super LSI as described above and has a heat generation density on the order of several tens of W / cm ² . In order to cool this effectively, in this embodiment, the micro thin film thermocouple 2 is provided at a density of about 10 ³ pieces / cm ² .

The micro thin film thermocouple 2 is formed by laminating two kinds of metals, in this embodiment, gold Au and platinum At. However, the type of metal is not limited to this. According to the current fine processing technology, the thin films 2A and 2B can be formed as thin as several tens angstroms.
The two types of metal thin films 2A and 2B are respectively provided with conductors 9
A and 9B are connected to the power supply 5.

Due to Joule heat generated in the lead wire 6,
A thermoelectromotive force is generated between the two types of thin films 2A and 2B. This thermoelectromotive force is input to the temperature detection circuit 3. The temperature detection circuit 3 is set so as to detect the temperature based on the magnitude of the thermoelectromotive force generated in the micro thin-film thermocouple 2 and output a signal of the temperature to the power supply control circuit 4.

The power supply control circuit 4 includes a temperature detection circuit 3
The temperature is known from the signal input from the microcomputer, a voltage (temperature control voltage) required for cooling is calculated according to the temperature, and the power supply 5 is applied so that the temperature control voltage is applied to the micro thin film thermocouple 2. Is set to issue a command.

The power supply 5 applies a voltage in a direction opposite to the direction of the thermoelectromotive force to the micro thin-film thermocouple 2 via conductors 9A and 9B as a temperature control voltage. The micro thin-film thermocouple 2 to which the temperature control voltage is applied performs a cooling action by the Peltier effect. In the temperature control device for an electronic device configured as described above, temperature detection and cooling are performed as follows.

The temperature of the actual heating portion such as the lead wire 6 of the semiconductor chip 1 rises, and a thermoelectromotive force is generated in the micro thin-film thermocouple 2. The temperature detection circuit 3 to which the thermoelectromotive force is input detects the temperature from the magnitude of the thermoelectromotive force. Subsequently, the signal of the detected temperature is input to the power supply control circuit 4. After calculating the value of the temperature control voltage required for cooling according to the temperature value, the power supply control circuit 4 issues a voltage application command to the power supply 5. Based on this command, the power supply 5 applies a temperature control voltage in a direction opposite to the direction of the thermoelectromotive force to the micro thin-film thermocouple 2 via the conductors 9A and 9B. Thereby, the micro thin-film thermocouple 2 cools the actual heat-generating portion such as the lead wire 6 by the Peltier effect.

In this embodiment, the semiconductor chip 1
The temperature is detected by the micro thin-film thermocouple 2 directly formed on the surface of the substrate, and at the same time, the substrate is directly cooled. Therefore, the cooling can be performed at high speed and efficiently as compared with the conventional case of cooling by flowing a fluid. Further, a device for flowing the fluid is not required, which contributes to the overall downsizing of the devices. In particular, in this embodiment, only the actual heat generating portion is cooled.
It is further cooled at high speed and high efficiency. According to the present embodiment, high-speed and high-efficiency temperature control of the semiconductor chip 1 and other electronic devices can be performed, so that a high-speed and high-performance computer can be further developed.

(Second Embodiment) Next, a second embodiment will be described. The second embodiment is a temperature detection method and an apparatus therefor. The temperature detecting device of the present embodiment is the same as the device of the first embodiment shown in FIG.
It is composed only of In this embodiment, since the micro thin film thermocouple is formed directly on the surface of the detection target, the temperature is detected at high speed.

Third Embodiment Next, a third embodiment will be described. The third embodiment relates to a temperature distribution detecting method and a heat flow distribution detecting method. In the third embodiment, a plurality (a large number) of the temperature detecting devices of the above-described second embodiment are provided in a predetermined region of a detection target, and a temperature distribution or a heat flow velocity distribution in the predetermined region is detected. Is what you do.

In the present embodiment, by arranging a large number of micro thin film thermocouples in a region having a micro area,
It is possible to detect temperature distribution or heat flow velocity distribution in a micro area. Further, high-resolution temperature distribution detection or heat flow distribution detection can be performed. Therefore, for example, it can be said that this is a measurement technique suitable for elucidating a turbulent heat transfer surface and a microscopic heat transfer on an engine wall surface.

(Fourth Embodiment) Next, a fourth embodiment according to the present invention will be described. The fourth embodiment is a method for detecting the thickness of a metal thin film and an apparatus therefor. As described in the section for solving the above-mentioned problem, the present inventors have clarified the relationship between the thickness of the thin film and the thermoelectromotive force in a quantum mechanical manner. Therefore, in the embodiment according to the present invention, the thickness of the micro metal thin film is detected based on the magnitude of the thermoelectromotive force generated in the micro thin film thermocouple. The film thickness detecting device for a metal thin film of the present invention is connected to a micro thin film thermocouple provided on a detection target, and calculates and detects the thickness of the thin film constituting the micro thin film thermocouple from the magnitude of the thermoelectromotive force. It has a film thickness calculation circuit (not shown) as a thickness calculation means.

[0024]

According to the present invention described above, the following effects can be obtained. Since the thickness of the metal thin film is detected using the thermoelectromotive force characteristics generated in the micro thin film thermocouple, the CV
It is possible to accurately detect the thickness of a thin film such as D, which is a target of a semiconductor fine processing technique.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a temperature control device of an electronic device.

FIG. 2 is a partially enlarged view of the electronic device of FIG. 1 as viewed from above.

FIG. 3 is a graph showing a relationship between a thermoelectromotive force generated in a micro thin-film thermocouple and a film thickness.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip (electronic device) 2 Micro thin film thermocouple 2A, 2B thin film 3 Temperature detection circuit (temperature detection means) 4 Power supply drive circuit (power supply drive means) 5 Power supply 6 Lead wire (actual heating part)

Claims (2)

(57) [Claims] 1. A method for detecting a thickness of a metal thin film forming a thermocouple based on a magnitude of a thermoelectromotive force generated in the thermocouple by heat applied to the thermocouple in which two kinds of minute metal thin films are joined. A method of detecting the thickness of a thin film. 2. A thermocouple in which two kinds of metal thin films are joined and a thickness of a metal thin film constituting the thermocouple is detected from a magnitude of a thermoelectromotive force generated in the thermocouple connected to the thermocouple. A thin film thickness detecting device comprising: a film thickness calculating means.