JP3559641B2 - Heating method and heating mechanism in vacuum vessel - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heating method and a heating mechanism in a vacuum vessel used for forming, etching, and analyzing a thin film.
[0002]
[Prior art]
Conventionally, as a method for heating the inside of a vacuum vessel, heater heating for generating heat by flowing an electric current through a linear or plate-like resistor, lamp heating using radiant heat emitted from a light emitting body, and the like have been mainly used.
[0003]
[Problems to be solved by the invention]
However, each of the above heating methods has some problems. First, among the methods using heater heating, in direct heating in which the object to be heated is brought into contact with the heater, there are restrictions on operations such as rotating the object to be heated, and in indirect heating through a vacuum, energy is not applied. Loss is large. Further, the power consumption is basically large due to the heating by the heat generated by the resistor.
[0004]
On the other hand, when the lamp is used for a long period of time, the amount of light emission decreases due to the deterioration of the filament, and when the film is formed in a vacuum vessel, the film adheres to the lamp surface and hinders the radiation of heat. Is reduced.
[0005]
On the other hand, in order to bring the inside of the vacuum container into an ultra-high vacuum state, simply heating the vacuum container is not enough to remove impurity gas such as water. By cleaning the inner wall of the container or the like, it becomes easy to obtain an ultra-high vacuum state. However, it is difficult to spread the plasma to each part in the vacuum vessel while maintaining the strength of the plasma.
[0006]
Therefore, an object of the present invention is to provide a heating method in a vacuum vessel with low energy consumption and a heating mechanism for the same, without restricting the operation of the object to be heated and excellent in the desorption effect of impurity gas. Is what you do.
[0007]
[Means for Solving the Problems]
According to the present invention, when plasma is generated using electric power or microwaves in a vacuum vessel, one is grounded, and one is locally strong between two electrically floating opposed conductors. It has been found that plasma is separately generated and completed.
[0008]
That is, the present invention provides at least one electrically grounded vacuum vessel for applying high-frequency power to an electrode to which power can be applied or introducing microwaves to generate plasma in a vessel in the presence of a dilute gas to process plasma. Heating in a vacuum vessel which is provided with a separated conductor and at least one electrically floating conductor facing the conductor, and which is heated by plasma generated secondarily between the at least one pair of conductors. It relates to a method and its mechanism.
[0009]
In the present invention, by adjusting the distance between the pair of conductors, the intensity of plasma generated between the conductors changes, a desired temperature can be obtained, and the temperature of one of the conductors can be further reduced. By detecting the temperature and gradually adjusting the distance between the conductors in accordance with the temperature fluctuation, the temperature can be kept constant.
[0010]
Further, in the present invention, by superimposing DC power on high-frequency power, an electrically floating conductor is greatly applied to the negative electrode, a stronger plasma is generated between the pair of conductors, and a larger calorific value is maintained. It is preferable because it can be performed.
[0011]
Further, in the present invention, since the inner wall of the vacuum vessel also serves as an electrically grounded conductor, the inner wall of the vacuum vessel can be heated, and the removal of impurities attached to the inner wall of the vacuum vessel is further achieved. In addition, a film with less impurities can be formed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Plasma is referred to as a fourth state located next to three states of a substance (solid, liquid, and gas), and refers to a state in which gas atoms are separated into ions and electrons. In addition, plasma generated by high-frequency power is generated secondarily without directly applying power to a place where a potential difference occurs between objects due to electrical grounding. Therefore, the secondary plasma is generated between the grounded conductor and the electrically floating conductor in the present invention. The electrons move in the plasma in accordance with the change in the direction of the electric field, and generate heat when they collide with an object.
[0013]
The heating method and the heating mechanism according to the present invention can be applied to any vacuum vessel that performs processing by generating plasma in an environment reduced to ultra-high vacuum. Examples of the plasma generating means include a high-frequency plasma for applying a high-frequency electric power and a microwave plasma for introducing a microwave, and a method of forming a thin film by physical or chemical vapor deposition using such plasma, etching, and plasma. It can be applied to various analyzers using
[0014]
In the present invention, "electrically floating" refers to a state in which it is not electrically connected to the plasma generating means, and is, for example, at a predetermined position in a vacuum vessel by an insulating support member or the like. Is held. “Electrically grounded” indicates a state in which the plasma generation means is electrically grounded.
[0015]
In the present invention, the electrically grounded conductor and the electrically floating conductor are both made of a conductive material, and may be the same or different. . However, a material that is easily etched by the generated plasma is not desirable because it adversely affects a film to be formed. Therefore, a material that is sufficiently corrosion-resistant, thermally stable, has a small sputtering yield, and emits a small amount of gas is selected. As a material having such a property, a metal material such as stainless steel or aluminum which is usually used as a material for a vacuum container can be given.
[0016]
The shape of the conductor is not particularly limited and may be any shape as long as desired heating can be obtained, but a plate-like conductor is usually used. The size of the vacuum container, the power of the introduced microwave, the distance between the conductors and the like may be appropriately determined so that desired heating is obtained. They may be the same size or different.
[0017]
When such a conductor is placed in a vacuum vessel, it may be placed near or in contact with an object to be heated at a position that does not hinder the target plasma reaction. For example, in order to heat a substrate to be processed, the substrate holder is used as an electrically floating conductor in the vicinity of the substrate holder supporting the substrate or the substrate holder itself. Further, when heating the inner wall of the vacuum vessel, the inner wall of the vacuum vessel itself is made of an electrically grounded conductor, and in contrast to this, for example, when the vacuum vessel is box-shaped, it is applied to each surface of the inner wall of the vessel. What is necessary is just to provide six electrically floating electrical conductors facing each other. Further, when the inner wall of the container has a curvature, for example, a cylindrical shape, a plurality of plate-like conductors having the same curvature may be used as the electrically floating conductor. Such a change in the device configuration can be appropriately made by those skilled in the art when implementing the present invention.
[0018]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to only these Examples.
[0019]
Example 1
FIG. 1 is a schematic diagram of a film forming apparatus of a sputtering method using a heating mechanism of the present invention for heating a substrate. The power from the DC power supply 3 via the high-frequency power supply 1 and the low-pass filter 2 can be applied to a target 5 having a magnet 4 on the back surface. The substrate 6 to be heated is placed on a conductive substrate holder 8 that is rotatable and electrically floated by an insulator 7, and the opening and closing of a shutter 9 can control the progress of film formation. . The electrically conductive plate 10 facing the substrate holder 8 and electrically grounded can be driven up and down via a bellows 11 by a shaft 12 outside the vacuum vessel. The shaft 12 is driven by converting the rotational movement of the servo motor 13 into a linear movement by a ball screw 14. The film forming gas in this apparatus is introduced into the vacuum vessel 16 via the mass flow 15.
[0020]
In this film forming apparatus, a thermocouple 17 is provided on the substrate holder 8 in order to keep the temperature of the substrate 6 constant, and an electric signal from the thermocouple 17 is transmitted to the temperature detector 18. The information is input to an information processing device 19 such as a personal computer. In the information processing device 19, the number of rotations is commanded to the servo motor 13 so as to eliminate the difference between the set temperature and the current temperature, and the distance between the substrate holder 8 and the conductive plate 10 is adjusted. A constant temperature can be maintained by repeatedly performing the temperature measurement and the distance adjustment.
[0021]
Next, in order to verify the heating capability of this heating mechanism, temperature characteristics with respect to parameters such as RF power, the distance between the substrate holder 8 and the conductive plate 10, and DC power were measured. In addition, the value when the substrate temperature became steady was read.
[0022]
FIG. 2 shows the temperature change of the substrate holder when the distance between the substrate holder 8 and the conductive plate 10 is fixed to 50 mm and the DC power is fixed to 0 W, and the RF power is applied to the target 5 in the range of 100 W to 500 W. It is a graph. As can be seen from the figure, the temperature tends to increase as the RF power increases.
[0023]
Next, with the RF power fixed at 300 W and the DC power fixed at 0 W, the distance between the substrate holder 8 and the conductive plate 10 was changed from 25 mm to 150 mm. FIG. 3 shows a graph of the temperature change in the substrate holder 8 at that time. According to the figure, the temperature tends to be highest when the distance is in the range of 75 mm to 100 mm. This is because the distance between the substrate holder 8 and the conductive plate 10 is too small or conversely too large. This is because the intensity of the plasma generated at the time decreases.
[0024]
FIG. 4 shows the temperature characteristics when the DC power was changed in the range of 0 W to 500 W with the RF power fixed at 200 W and the distance between the substrate holder 8 and the conductive plate 10 fixed at 50 mm. It can be understood from this graph that the temperature in the substrate holder is dramatically increased when DC power is superimposed as compared with FIG. 2 in which only RF power is used.
[0025]
Finally, film formation was actually performed using the apparatus having the substrate heating mechanism. Aluminum was used as the target 5, a film-forming gas consisting of argon and oxygen was introduced through the mass flow 15, and the RF power was supplied to the target 5 from the high-frequency power supply 1 by 200 W while the shutter 9 was closed, and the DC power was Of 400 W was applied, and the distance between the substrate holder 8 and the conductive plate 10 was set to 50 mm. When the temperature of the substrate holder 8 reaches 250 ° C., the number of rotations of the servo motor 13 is controlled from the information processing device 19 so as to keep the temperature constant, and the substrate holder 8 is further rotated by rotating means (not shown). Then, the shutter 9 was opened to start forming an alumina film on the substrate 6. After the film formation, when the in-plane film thickness distribution of the alumina film on the substrate 6 was measured, there was almost no variation in the circumferential film thickness with respect to the rotation. In addition, a very high value of 1.83 was obtained as the refractive index of the formed alumina at a wavelength of 248 nm. Further, since the substrate heating mechanism does not require energy such as electric power, the cost required for film formation is reduced to about 比 べ of that in the case of heating with a heater.
[0026]
Example 2
FIG. 5 is a schematic diagram of a film forming apparatus by a chemical vapor deposition method (CVD method) using the heating mechanism of the present invention. The power from the DC power supply 22 via the high-frequency power supply 20 and the low-pass filter 21 can be applied to the rod-shaped electrode 23. The substrate 24 is electrically floating via the substrate holder 25, and the progress of film formation can be controlled by opening and closing the shutter 26. The distance between the conductive plate 28 electrically floating by the insulator 27 and the inner wall of the vacuum container can be adjusted by the shaft 30 from outside the container via the bellows 29. The shaft 30 is driven by converting the rotational movement of the servo motor 31 into a linear movement by a ball screw 32. On the other hand, the introduced gas is introduced into the vacuum vessel 34 via the mass flow 33.
[0027]
In this embodiment, a loop for keeping the temperature of the conductive plate constant will be described. First, the inner wall temperature of the vacuum vessel 34 is detected by a thermocouple 35 and a temperature controller 36, respectively, and the information is input to an information processing device 37 such as a personal computer. Next, the information processing device 37 instructs the servo motors 31 to output the number of rotations so as to eliminate the difference between the set temperature and the current temperature, and adjusts the distance between each conductive plate 28 and the inner wall of the vacuum vessel. . A constant temperature can be maintained by repeatedly performing the temperature measurement and the distance adjustment.
[0028]
Next, an example in which a film is actually formed using the film forming apparatus in this embodiment will be described.
[0029]
Argon, nitrogen, and silane gases were introduced into the container via the mass flow 33 as source gases, and RF power of 500 W was applied to the electrode 23 while the shutter 26 was closed to generate plasma. When the temperature of the inner wall of the vacuum vessel reached 100 ° C., baking and evacuation were performed for 10 minutes while controlling the distance between the conductive plate 28 and the inner wall of the vacuum vessel so as to maintain this temperature. Thereafter, the shutter 26 was opened to start film formation, and an attempt was made to form a SiN film on the substrate. After film formation, the substrate was taken out, and the reflection characteristics were measured with a spectrometer. Then, after leaving for 1 month in an environment of 70 ° C. and 85% RH, the reflection characteristics were measured again. As a result, the shift amount of the reflection characteristics of the SiN film formed only by the ordinary heating of the heater was 15 nm, whereas the SiN film manufactured according to the present invention was 7 nm, and had excellent optical characteristics. It was found that a thin film was obtained. This is considered to be due to the fact that the amount of impurities in the film became extremely small because the desorption of impurities in the vacuum vessel was sufficiently performed by the heating mechanism of the present invention.
[0030]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it became possible to provide the heating method which does not restrict the movement of a to-be-heated body, was excellent in the desorption effect of impurity gas, and consumed little energy.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a film forming apparatus by a sputtering method employing a heating mechanism according to the present invention.
FIG. 2 is a graph showing a change in conductor temperature when the RF power to be introduced is changed while keeping the distance between the conductors constant.
FIG. 3 is a graph showing a change in conductor temperature when the distance between conductors is changed while keeping the introduced RF power constant.
FIG. 4 is a graph showing a change in the conductor temperature when the DC power to be superimposed is changed while keeping the distance of the conductor and the introduced RF power constant.
FIG. 5 is a conceptual diagram showing an example of a film forming apparatus by a CVD method employing a heating mechanism according to the present invention.
[Explanation of symbols]
1, 20 High-frequency power supply 2, 21 Low-pass filter 3, 22 DC power supply 4 Magnet 5 Target 6, 24 Substrate 7, 27 Insulator 8, 25 Substrate holder 9, 26 Shutter 10 Electrically grounded conductive plate 11, 29 Bellows 12 , 30 shaft 13, 31 servo motor 14, 32 ball screw 15, 33 mass flow 16, 34 vacuum vessel 17, 35 thermocouple 18, 36 temperature controller 19, 37 information processor 23 rod-shaped electrode 28 electrically floating conductive plate

Claims (10)

In a vacuum vessel that applies high frequency power to an electrode to which power can be applied or introduces microwaves to generate plasma in the vessel in the presence of a dilute gas and processes the plasma, at least one electrically grounded conductor and A heating method in a vacuum vessel, wherein at least one electrically floating conductor facing the conductor is provided, and heating is performed by plasma generated secondarily between the at least one pair of conductors. The heating method according to claim 1, wherein the temperature is adjusted by adjusting a distance between the conductors. 3. The heating method according to claim 2, wherein the temperature of the at least one of the pair of conductors is detected, and the temperature is kept constant by gradually adjusting the distance between the conductors in accordance with the change in the temperature. The heating method according to any one of claims 1 to 3, wherein a DC current is superimposed on the high-frequency power. The heating method according to any one of claims 1 to 4, wherein the electrically grounded conductor is an inner wall of a vacuum vessel. In a vacuum vessel that applies high frequency power to an electrode to which power can be applied or introduces microwaves to generate plasma in the vessel in the presence of a dilute gas and processes the plasma, at least one electrically grounded conductor and A heating mechanism in a vacuum vessel, comprising: at least one electrically floating conductive plate facing the conductive plate; and generating and heating plasma secondary between the at least one pair of conductive materials. The heating mechanism according to claim 6, further comprising a means for adjusting the distance between the conductors. A means for detecting the temperature of at least one of the pair of conductors, and means for instructing the interconductor distance adjusting means to instruct the interconductor distance so that the detected temperature is constant. 8. The heating mechanism according to 7. The heating mechanism according to any one of claims 6 to 8, wherein a DC current is superimposed on the high-frequency power. The heating mechanism according to any one of claims 6 to 9, wherein the electrically grounded conductor is an inner wall of a vacuum vessel.

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