JPH1041279A - Method and device for plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the production of exfoliation and foreign matters by reducing the thickness of an unnecessary deposited film as much as possible by providing a mechanism which supplies electromagnetic waves having such a wavelength that is not absorbed by a member from the backside of the member, but by the unnecessary deposited film, at a constant intensity. SOLUTION: A substrate electrode 2 for placing a wafer 1 is provided with a power applying mechanism 4 connected to a power source 3 and a wafer temperature control mechanism 6 connected to a cooler (or heater) 5. An insulator layer 7 is formed around the mechanism 4 for preventing the leakage of electric power and the layer 7 is surrounded with a grounded earth plate 8. In addition, a lamp 9 which mainly emits light having a specific wavelength is buried in the layer 7. When the wafer is irradiated with the light emitted from the lamp 9, foreign matter producing spots can be removed and the cleaning frequency of the wafer 1 can be reduced remarkably. In addition, the number of persons required for the cleaning work of the wafer 1 can be reduced. Furthermore, the temperature of the wafer 1 can be raised easily, because the thin film has a small heat capacity is heated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to etching in the processing of semiconductors and the like, and more particularly to a method for preventing the formation of unnecessary deposited films adhering to the periphery of a wafer during processing.

[0002]

2. Description of the Related Art In a dry etching method using plasma, a side wall protective film is formed to control the cross-sectional shape of a hole to be almost vertical, thereby preventing an etching reaction on a side wall portion. The components of the sidewall protective film are mainly a reaction gas decomposed in the plasma and a reaction product generated by the reaction of the reaction gas with the material to be etched. Adsorbs to low temperature parts around the electrodes. Since the gas component is in a radical state, it easily reacts with other molecules to form a partially polymerized or crosslinked structure.

In general, a deposited film and a film adhered in a state where the stress of the underlying electrode member is different and the temperature during processing is high generate stress when the temperature is lowered after the completion of the processing. As the film thickness increases, the stress increases, and when the thickness exceeds a certain value, peeling occurs. At this time, minute peeled pieces are generated in the processing chamber, and a part thereof adheres to the wafer and becomes foreign matter. Further, the minute peeling pieces deposited in the apparatus are scattered in the atmosphere due to a change in air pressure, electric field, and the like in the wafer processing after the next processing, and a part of the pieces adheres to the wafer. Therefore, when the above-mentioned phenomenon occurs, it is indispensable to perform cleaning, during which the apparatus stops.

[0004] Cleaning is divided into two methods. The first method is a method of opening a processing chamber and exchanging a part to which an unnecessary deposited film has adhered. Although this method is a method that can reliably suppress foreign substances, it can not be executed unless people are always present, after evacuation is started until the atmosphere inside the processing chamber is stabilized due to adsorption of moisture etc. to release to the atmosphere, There is a problem that several to ten and several hours are required.

The second method is a method of removing an unnecessary deposited film by introducing a gas component for etching the unnecessary deposited film into the inside. This method has the advantage of not exposing the interior to moisture in the atmosphere, but it has a slow removal rate of unnecessary deposited films, and is not always correlated with the deposition rate, and unnecessarily scrapes the underlying material or insufficient removal. A spot occurs. For this reason, the second method is often performed in combination with the first method in many cases.

[0006] Once the unnecessary deposited film adheres as in this method, it takes a considerable time to remove it. Therefore, a method in which the unnecessary deposited film does not adhere is desired. However, it is practically difficult to perform etching without generating an unnecessary deposited film, and it is desirable to apply a means for preventing the unnecessary deposited film from intensively adhering and causing peeling in a short time.

As this method, there is a method described in Japanese Patent Application Laid-Open No. 5-283368, in which the periphery of the electrode is heated to lower the probability of adsorbing radicals and prevent the concentrated formation of unnecessary deposited films.

[0008]

Heretofore, the interaction between the wall temperature around the electrode and the plasma has not been sufficiently considered. In other words, the formation speed of the unnecessary deposited film is the highest in the portion close to the plasma, but the radical species reaching this portion has both the etching property and the depositing property. The sedimentation phenomenon is balanced. Looking at the phenomenon when the base member is heated in this part,
As a whole, the rise in temperature lowers the probability of adsorbing radicals, while the rise in temperature promotes the etching reaction, thereby lowering the unnecessary deposition film formation rate. In particular, in the immediate vicinity of the plasma, ions are supplied from the plasma diffused to the periphery, and the etching reaction of the underlying member proceeds in combination with the reduction in the formation speed of the unnecessary deposition film. If the underlying member is partially lacked by the etching, the electric field is further concentrated and the amount of ions increases, so that the etching speed further increases, resulting in a bad circuit. In this case, it is necessary to replace the electrode member in a short period of time.

Even when etching does not occur, there is a case where a phenomenon in which radicals react with the base member and new reaction products adhere to the base member due to constant exposure to the plasma.

As described above, prevention of the formation of an unnecessary deposited film and
Means are required to achieve both protection of the electrode member from radical components.

[0011]

According to the present invention, an unnecessary deposited film for protecting radical components is formed on an electrode member in the present invention. However, peeling is caused by controlling the film thickness as thin as possible. Create a state in which no foreign matter is generated. Specifically, there is provided a mechanism for supplying an electromagnetic wave having a wavelength that is absorbed by the unnecessary deposition film without being absorbed by the member from the back surface of the member or the like at a constant intensity.

By irradiating the member around the electrode with an electromagnetic wave having a wavelength that is transmitted and absorbed by the unnecessary deposition film, the irradiation light strays in the processing chamber and gradually attenuates when the member has a clean surface. As the etching process proceeds, the formation of the unnecessary deposition film on the member starts. When the thickness of the unnecessary deposition film is extremely small, most of the irradiation light is transmitted, the absorption amount in the film is small, and the temperature rise is small.

As the film thickness grows, the amount of light absorbed in the film increases and the heat capacity of the film is small, so that the film temperature easily rises. When the film temperature rises, radical components that have been polymerized and deposited on the film surface after being adsorbed are desorbed in a short time after the adsorption, so that a deposition reaction is less likely to occur. As the number of films increases, the absorption energy of light increases, so that the deposition rate further decreases. On the other hand, the probability that radicals etching the deposited film react on the surface of the deposited film generally increases with an increase in temperature. As a result, the deposited film on the peripheral member of the wafer is balanced at a constant film thickness.

Therefore, since the surface of the member is always covered with the deposited film, the gas (for example, fluorine radicals) that corrodes the underlying member does not come into direct contact with the member. The life of the member can be extended without causing a change in On the other hand, dust generation due to peeling can be prevented by suppressing an increase in the thickness of the deposited film.

As described above, since there is no dust generation and no scraping of the members, the inside of the apparatus is cleaned (including both the case where no manual operation such as plasma is performed and the case where the apparatus is opened and parts are replaced). Frequency can be greatly reduced, and the operation rate of the apparatus can be improved.

[0016]

FIG. 1 is a sectional view of an electrode structure according to an embodiment of the present invention. Substrate electrode 2 on which wafer 1 is placed
Is a power application mechanism 4 connected to a power supply 3 and a wafer temperature control mechanism 6 connected to a cooler (or heater power supply) 5.
An insulating layer 7 is formed around the power application mechanism 4 to prevent leakage of power, and is further surrounded by a ground plate 8 grounded. A lamp 9 mainly emitting a specific wavelength is embedded in the insulator layer 7.
In this case, the lamp 9 has a concentric shape,
A plurality of short lamps may be arranged in the radial direction. The arrangement direction is not limited as long as the light intensity in the circumferential direction is uniform on the surface of the insulator layer 7 around the wafer.

A plasma generating mechanism 10 is arranged opposite to the surface of the wafer opposite to the substrate electrode 2. In the case of the conventional parallel plate type, the plasma generating mechanism 10 is provided with a conductive flat plate connected to a power source at a predetermined interval from the wafer. Further, in the case of the ECR method, a microwave supply mechanism having an electromagnet disposed around is installed (a magnet or the like may be disposed around the wafer depending on the plasma generation mechanism).

The above substrate electrode 2 and plasma generating mechanism 1
Numeral 0 is taken into a vacuum chamber 14 having a gas supply mechanism 11, a vacuum exhaust mechanism 12, and a pressure adjusting mechanism 13.

After the vacuum chamber 14 is evacuated for a certain period of time by the vacuum evacuation mechanism 12 and the wafer 1 is brought to a predetermined temperature by the wafer temperature control mechanism 6, a predetermined amount of a predetermined etching gas is supplied by the gas supply mechanism 11 to adjust the pressure. A predetermined pressure is set by the mechanism 13. Then, the plasma generation mechanism 10
When power or the like is applied to the space, an electromagnetic field 15 is supplied to the space on the wafer 1 and a plasma 16 is generated.

The etching gas is decomposed by the plasma 16 into a radical state. The radicals are adsorbed on the surface of the wafer 1 by gas flow or diffusion. On the other hand, when the ions in the plasma 16 collide with the wafer 1 due to the potential generated between the plasma 16 and the wafer 1, a reaction with the base material occurs due to the interaction with the radicals, the base material is shaved, and a reaction product is generated. . A part of the reaction product is deposited on the side wall of the cut hole to form a protective film so that the side wall does not spread, but the rest is released into the gas phase. The gas of the reaction product has a property that it is easily deposited so as to form a protective film, but the surface of the wafer 1 is hardly deposited because the temperature is increased due to ion incidence. Therefore, the periphery of the wafer 1, that is, the vicinity of the plasma generating section comes into contact with many radicals including the reaction product. In some cases, radicals of etching gas (chlorine and fluorine) are mixed, but gas having a deposition property is dominant, and an unnecessary deposited film is formed.

When the pressure in the vacuum chamber 14 is high, the gas moves along the gas flow and tends to concentrate at a specific location, and when the reaction pressure is low, the diffusion phenomenon becomes strong and the gas accumulates in a widened area. In the deposition of the film, a film adsorbed and polymerized on the uneven portions of the base grows without a direct reaction with the base member.

Here, when light having a wavelength which is easily absorbed by the deposited film and which is hardly absorbed by the underlying member is irradiated by the lamp 9 particularly at a portion where the deposited film is grown in a concentrated manner, the initial state of the deposited film is high. Like the underlying member, most of the irradiation light is transmitted and the deposition phenomenon continues. Further, as the deposition continues, the energy that the deposited film receives from the irradiation light increases, and the volume film surface temperature increases. Even if the gas collides with the surface where the temperature has risen, the adsorption probability is low and the deposition rate decreases. Here, considering the case where the entire base member is heated, the periphery of the plasma is surrounded by an insulator and the heat conduction is low and the heat capacity is large, so that a large amount of energy is required to be supplied, but fine temperature control is difficult. is there. Therefore, if the etching is started in a state where the temperature of the member is high in the initial state, no gas is deposited on the surface of the member, but on the contrary, the gas for etching the underlying member alone reacts with the surface. Erosion of the base member depending on the member,
The generation of new reaction products is likely to be a source of foreign matter. Therefore, for example, the entire heating mechanism is effective in a range where the metal member can be used on the downstream side of the exhaust gas, but it is difficult to apply it around the electrodes.

In the above selective lamp heating, when the film thickness reaches a certain value, the deposition and the etching are in an equilibrium state, and the deposition phenomenon stops apparently. When the film thickness is maintained in a thin state, the stress generated in the deposited film is small, and the generation of foreign matter due to peeling can be avoided. It is difficult to control the entire deposition in the electrode by the selective heating by light irradiation described above, but by applying the present method to a location where the deposition is remarkable, the conventional foreign matter generation location is removed,
The frequency of cleaning can be greatly reduced, and the number of personnel involved in the cleaning operation can be reduced. In addition, since a thin film having a small heat capacity is heated, the temperature can be easily raised, and it is sufficient to perform lamp irradiation only during plasma generation, which is effective in saving energy. Further, it is not necessary to constantly turn on the lamp, and for example, the on / off of the lamp may be controlled in conjunction with the on / off of the plasma ignition power supply.

In the case of etching an oxide film, CF gas is used as a gas.
(For example, CF ₄ , CHF ₃ ) is used, and the film deposited at this time is a polymer film mainly composed of C and F. The absorption characteristics for the wavelength of the polymerization film is shown in FIG. 2, 1100 cm ~ ¹
It can be seen that there is an absorption band around １1300 cm１ ¹ .
On the other hand, in the case of quartz generally used for an electrode peripheral member, the reflectance near 1000 cm to ¹ is high and the deposited film cannot be irradiated with the selective light. On the other hand, the absorption and reflection characteristics of SiC are shown in FIG. 3 (Basic physical property chart, P351, Kyoritsu Shuppan).
It can be seen that light of about 1000 cm- ¹ is transmitted. Also,
In the lamp, selective heating of the oxide film is achieved by using an infrared lamp. The above combination is an example of an oxide film, but other etchings may be designed in the same way.

In the description so far, the film deposited on the member surface is directly heated and controlled. However, there is also a method of forming a thin film absorbing a specific wavelength on the surface in contact with the processing gas in advance.

A CF-based polymer is deposited on the surface by arranging members in a CF-based gas, particularly a gas having a strong depot property (for example, a type having a large C / F ratio such as C ₂ F ₆ ) and generating plasma. Let it.

In general, since the heat capacity of the film to be heated is small, it can be easily heated, so that the supplied light intensity is small. A reflection plate or the like may be provided.

[0028]

According to the present invention, it is possible to prevent the unnecessary deposited film deposited on the wall surface near the electrode from being peeled off, to reduce the frequency of operations such as foreign substance check and maintenance, and to improve the operation rate of the apparatus.

[Brief description of the drawings]

FIG. 1 is a sectional view of a plasma etching electrode according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram of absorption of an unnecessary deposition film at the time of etching an oxide film.

FIG. 3 is a characteristic diagram of reflection and absorption of a silicon carbide member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Substrate electrode, 3 ... Power supply, 4 ... Power application mechanism, 5 ... Cooler, 6 ... Wafer temperature control mechanism, 7 ... Insulator layer, 8 ... Ground plate, 9 ... Lamp, 10 ... Plasma generation Part, 11: gas supply mechanism, 12: vacuum exhaust mechanism, 13 ...
Pressure adjusting mechanism, 14: inside vacuum chamber, 15: electromagnetic field, 16:
plasma.

Claims (6)

[Claims] In a plasma etching process for a semiconductor, a plasma etching method characterized by selectively irradiating a wavelength absorbed by an unnecessary deposition film adhering to the periphery of an electrode and selectively heating only the unnecessary deposition film. 2. The plasma etching method according to claim 1, wherein the irradiation of the unnecessary deposition film absorption wavelength is started and stopped according to the on / off state of the plasma. 3. In a plasma etching apparatus, an electrode peripheral member on which an unnecessary deposition film is formed is made of a lamp mainly emitting light of a wavelength absorbed by the unnecessary deposition film to be adhered, and a material transmitting the wavelength. A plasma etching apparatus characterized in that it includes a plasma etching treatment apparatus. 4. The method according to claim 3, wherein the reaction gas to be introduced is a gas mainly composed of carbon and fluorine, the material of the electrode peripheral member to which the unnecessary deposited film is attached is made of silicon carbide, and the lamp is an infrared lamp. A plasma etching equipment. 5. In a plasma etching apparatus, a thin film for absorbing a wavelength mainly emitted by a lamp is previously formed on a surface of a member on which an unnecessary deposition film is attached around an electrode, and the electrode peripheral member is provided with a light of the lamp. A plasma etching apparatus comprising a material made of a material that transmits light and including the lamp on a side opposite to a surface on which the thin film is formed. 6. The lamp according to claim 3, 4 or 5, wherein a surface of the lamp other than a direction in which the unnecessary deposited film is formed mainly emits a wavelength that is absorbed by the unnecessary deposited film attached to the periphery of the electrode. A plasma etching processing device provided with a reflection plate around it.