Plasma treatment method

Abstract

A plasma treatment method of etching a substrate to be processed by using a gas plasma in a treatment chamber. The method includes exhausting reaction products obtained by etching and released into a vapor phase as a gas from the treatment chamber, wherein the reaction products on an outer periphery of the substrate are more efficiently exhausted and setting a deposition probability of the reaction products in a central part of a plane of the substrate to be low and setting a deposition probability of the reaction products in a peripheral part of a plane of the substrate to be high. The setting of the deposition probability is effected by setting a temperature in the central part of the substrate higher than a temperature in the peripheral part of the substrate.

Description

BACKGROUND OF THE INVENTION

The present invention relates to plasma treatment for performing etching or the like on a substrate to be treated; and, more particularly, the invention relates to a plasma treatment method and plasma treatment apparatus in which the treatment characteristics in the central part of the substrate and those in the peripheral part of the substrate to be treated are uniformized.

Various methods have been devised for the operation conventional plasma treatment apparatuses in order to uniformize the plasma density (ion current value) and ion energy (RF bias voltage) in the plane of a substrate (wafer) and to uniformize the substrate temperature. For example, the Japanese unexamined patent No. 7-18438 discloses a technique for uniformizing the temperature distribution in the substrate by forming roughness on the surface of an insulating material on a substrate supporting face of a flat electrode, changing the density or depth of the rough surface of the insulating material, and distributing the electrostatic adsorption.

As the substrate size increases and the etching size becomes finer, however, the influence of the distribution of etching reaction products in the central part of the substrate and those in the peripheral part of the substrate become significant.

FIG. 15 is a diagram showing the behavior of etching reaction products. As shown in the diagram, etching reaction products, such as Al, Cl, C, and the like, react with a plasma etching gas (ions and radicals) on a substrate (wafer) 2 to be treated, evaporate in a vapor phase, and become Al₂Cl₆ or the like. The reaction products exhibit a complicated behavior in that they are directed again at the substrate 2 to be treated, or they are dissociated again in the plasma and the dissociated species are directed at the substrate 2. That is, etched Al on the bottom of the substrate is released as reaction products into a vapor phase and a part of them is dissociated again in the plasma and is again directed at the substrate 2. A photo resist 25 is likewise etched so that the substrate is again irradiated with the reaction products of the resist. Electrically neutral species among the species dissociated from the reaction products in the plasma are directed also at the side walls of an area to be etched and are deposited. Such species, such as species which are obtained by etching the bottom face and are directly deposited on the side walls, species directed at the side walls sputtered by the incident ions including physical or chemical elements, and the like, are deposited, thereby forming a side wall protection layer 26.

Among the effects, with respect to the re-irradiation of the reaction products, non-uniformity of the amount of irradiation in the plane of the substrate tends to occur for the following reason. The reaction products obtained by etching and which are released into a vapor phase are exhausted as a gas from the etching chamber. The further out one goes on the substrate, the more the reaction products are exhausted efficiently. As shown in FIG. 16, therefore, in the density distribution of the reaction products in the vapor phase, that is, the re-irradiation amount distribution of the reaction products, inevitably, the density or the re-irradiation amount is high in the central part of the substrate and is low in the peripheral part thereof.

As mentioned above, in a peripheral part of the substrate, the amount of the reaction products is smaller than that in the central part of the substrate since they are exhausted together with the etching gas. In case of metal etching, if the side wall protection layer is thick, the etch rate on the side walls due to the ion assisted reaction becomes low. Because of this, when describing a process for a trench as an example, the shape of a part to be etched becomes a so-called tapered shape in which the width is reduced as the etch depth increases. On the contrary, when the side wall protection layer is too thin, the side walls are etched and the part to be etched becomes wider than a target width. Consequently, in order to obtain a vertical shape at an etched part, the amount of deposition of the side wall protection layer has to be optimized so as to obtain a proper thickness and prevent the side walls from becoming fat or thin.

On the other hand, with reduction in the etching size, the need for good processing accuracy with respect dimensions increases. For example, when about 1/10 of a design dimension is a permissible level, the permissible level is ±0.05 μm for the design dimension of 0.5 μm. With reduction in the dimension to 0.25 μm and 0.13 μm, the permissible levels become ±0.025 μm and ±0.013 μm, respectively. In order to achieve such a required specification, factors exerting an influence on the processing dimension have to be made clear and to be accurately controlled.

With the reduction in the etching size, also in dense and sparse patterns in which fine patterns and sparse patterns which are not so dense mixedly exist, the need for a good processing accuracy with respect to dimensions has become increasingly important.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a plasma treatment method and a plasma treatment apparatus in which the influence on treatment characteristics of the reaction products in a plasma treatment, such as etching, is offset, so that uniform treatment characteristics can be obtained in the plane of a substrate.

It is another object of the present invention to provide a plasma treatment method and a plasma treatment apparatus which improves the uniformity in the substrate plane of a shape to be processed in consideration of the influences of reaction products at the time of plasma treatment, such as etching.

It is a further object of the present invention to provide a plasma treatment method and a plasma treatment apparatus which can obtain an etching treatment characteristic in which there is no variation in processing dimension in dense and sparse patterns.

According to a feature of the invention, in a plasma treatment method of performing etch treatment on a substrate to be processed by using a gas plasma via a mask in a treatment chamber, plasma treatment is performed while maintaining the in-plane uniformity of a side wall protection layer formed on the side walls of a part to be etched in the substrate.

According to another feature of the invention, in a plasma treatment method of treating a substrate to be processed by using a gas plasma via a mask in a treatment chamber, plasma treatment is performed while equalizing the amount of deposition of a side wall protection layer formed on the substrate to be processed in the center of the substrate with that in an outer part of the substrate, thereby maintaining the in-plane uniformity of the side wall protection layer.

According to a further feature of the invention, in a plasma treatment method of treating a substrate to be processed with a gas plasma by using a resist as a mask in a treatment chamber, plasma treatment is performed on the substrate while maintaining the uniformity of the amount of deposition of reaction products which are generated by a reaction between the substrate to be processed and the plasma and are directed at and deposited on the substrate in the plane of the substrate to be processed, thereby forming a side wall protection layer having a uniform plane on the substrate.

According to still another feature of the invention, in a plasma treatment method of performing plasma treatment on a substrate to be processed with a gas plasma by using a resist as a mask in a treatment chamber, the plasma treatment is performed while maintaining the in-plane uniformity of a side wall protection layer formed on the substrate by controlling the temperature of the substrate.

It is yet another feature of the invention that the plasma treatment is performed on the substrate to be processed while adjusting the pressure, flow rate, and mixing ratio of a process gas in the treatment chamber.

It is another feature of the invention that the plasma treatment is performed on the substrate to be processed while regulating the amount of the reaction products exhausted from the treatment chamber.

It is another feature of the invention that the plasma treatment is performed on the substrate to be processed while adjusting the kind of process gas or the pressure of the process gas in the treatment chamber.

It is another feature of the invention that variation in a deposition amount of reaction products in the plane of the substrate to be processed is maintained within ±10%.

It is another feature of the invention that the diameter of the substrate to be processed is 200 mm or larger and a pattern formed on the substrate to be processed is 0.35 μm or smaller.

According to another feature of the invention, in a plasma treatment apparatus for treating a substrate to be processed by using a gas plasma, there is a substrate holding electrode on which the substrate to be processed is placed and which controls the temperature of the substrate so that temperatures in the central and peripheral parts of the substrate are different and has a function of maintaining an in-plane uniformity of a deposition amount of reaction products in the plane of the substrate.

In the case of etching, usually, it is an objective to perform etching vertically and faithfully with respect to the processing dimension via a mask. In this case, etching in a direction vertical to the etching direction, that is, etching of side walls exerts an influence on the processing dimension. In the etching of side walls, when the etch pressure is high, injected ions also contribute to the etching. When the etch pressure is sufficiently low, the ion injection can be almost ignored. In such a state where the ion injection can be almost ignored, the etching of side walls largely depends on a chemical reaction between the side walls and radicals. The chemical reaction depends on the temperature and the density and kind of radicals irradiated and deposited. In the case of etching, reaction products which suppress the chemical reaction are deposited on the side walls. It can be said that the amount of the deposition, that is, the thickness of the side wall protection layer, determines the side wall etch rate. In other words, the control of the thickness of the side wall protection layer is the key to improvement in the processing accuracy.

Consequently, in the etching of a finer pattern on which the influence of the reaction products is large, especially, it is necessary to consider distribution characteristics in which the reaction products in the vapor phase are not uniform in the plane of the substrate and the amount of the reaction products is smaller in the peripheral part of the substrate, and to obtain a plasma distribution and a substrate temperature distribution which make the in-plane distribution of the side wall protection layer uniform by offsetting such influence.

According to the invention, in a plasma treatment method of treating a substrate to be processed with a gas plasma via a mask in a treatment chamber, the substrate is subjected to plasma treatment while maintaining the in-plane uniformity of the side wall protection layer formed on the substrate. By maintaining the in-plane uniformity of the side wall protection layer on the substrate to be processed, the etch rate of the side walls by an ion assisted reaction becomes uniform. Even in the case of a fine pattern, a vertical shape of the etched part can be easily obtained.

In order to maintain the in-plane uniformity of the side wall protection layer formed on the substrate to be processed, for example, the temperature distribution in the substrate plane is controlled. The higher the substrate temperature is, the lower will be the probability that the reaction products which are directed again at the substrate will be deposited on the side walls of the part to be etched or the like. That is, when the substrate temperature is constant, the deposition probability of the reaction products in the plane of the substrate becomes constant. Consequently, the amount of deposition on the side walls of the treated part, that is, the thickness of the side wall protection layer is proportional to the re-irradiation amount of the reaction products. As a result, the deposition amount of reaction products on the substrate increases in the center of the substrate and the shape of the treated part and that of a peripheral part become different.

In order to solve the problem and maintain the in-plane uniformity of the side wall protection layer on the substrate to be processed, at the time of the plasma treatment, for example, the temperature is controlled so that the temperature in the center of the substrate is higher as compared with that in the peripheral part. Since the deposition probability of the reaction products is low when the temperature in the center of the substrate is high, even if the re-irradiation amount of the reaction products is large, the amount of reaction products deposited on the side walls of the etched part is therefore small. The temperature of the substrate is regulated to have a characteristic such that the temperatures in and out of the substrate plane are different so that the amount of the reaction products deposited on the side walls in the substrate plane becomes uniform. Thus, the treatment characteristics in the substrate plane can be made uniform.

When the substrate temperature is changed, not only will the deposition probability of the reaction products change, but also the deposition probability of the etching gas plasma (especially, radicals) changes. The rate of etch reaction itself also changes. Consequently, since the amount of the reaction products being generated changes, it is necessary to control the substrate temperature distribution in accordance with the conditions of the plasma treatment, such as etching.

For maintaining the uniformity in the plane of the side wall protection layer, there are various methods of controlling the temperature distribution in the substrate plane. For example, the surface of the electrode is divided into a part which comes into contact with the back face of the wafer and a part (trenches) which does not come into contact with the back face, and the in-plane temperature of the wafer can be controlled by utilizing the fact that the overall heat transfer coefficient in the contact part and that in the trenches are different. The overall heat transfer coefficient can be also changed by varying the depth of the trenches.

Further, the overall heat transfer coefficient can be controlled by coating the trench with a film. Further, by adjusting the kind and thickness of the film coated on the trench, the temperature can be changed according to the process. By coating with a film, cleaning can be carried out easily. The film does not have to be made of plastics, but can be made of a metal or ceramics. The film has to be thin. The temperature of the wafer also can be controlled by coating a part which is in contact with the back face of the wafer with the film.

According to the invention, a plasma treatment method and a plasma treatment apparatus can be provided, in which the influence on the etching characteristics of the reaction products in the plasma treatment is offset and in which uniform treatment characteristics can be obtained in the substrate plane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of control characteristics of an in-plane temperature of a substrate according to the invention;

FIG. 2 is a vertical cross section showing the essential part of an electrode in a plasma etching apparatus according to an embodiment of the invention;

FIG. 3 is a plan view of the essential part of the electrode of FIG. 2;

FIG. 4 is a schematic diagram showing a state where an aluminum wiring is being etched according to the method of the invention;

FIG. 5 is a diagram showing the relation among substrate temperature, and generation amount and re-irradiation distribution of reaction products at the time of plasma etching according to the invention;

FIG. 6 is a graph showing the relation among the depth of recessed parts (or trenches) of an electrostatic adsorption electrode and pressure loss (Pa) on the back face of the electrode;

FIG. 7 is a graph showing the relation between pressure (Pa) on the back face of the electrode and an overall heat transfer coefficient (W/m²×K) by gas molecules;

FIG. 8 is a diagram showing the relation between a distance (d) between the back face of the substrate and the surface of the electrode and the overall heat transfer coefficient by gas molecules when the pressure is constant;

FIG. 9 is a vertical cross section of an electrode according to another embodiment of the invention;

FIG. 10 is a diagram showing the electrode according to another embodiment of the invention;

FIG. 11 is a diagram showing the electrode according to another embodiment of the invention;

FIG. 12 is a diagram illustrating a method of controlling the temperature in the substrate plane according to another embodiment of the invention;

FIG. 13 is a diagram showing the relation between the pressure on the back face of the substrate and the overall heat transfer coefficient;

FIG. 14 is a diagram illustrating an etching treatment method according to another embodiment of the invention;

FIG. 15 is a diagram for showing the behavior of etching reaction products at the time of plasma etching in accordance with a conventional technique;

FIG. 16 is a diagram showing the relation among substrate temperature, and generation amount and re-irradiation distribution of reaction products at the time of the plasma etching in accordance with the conventional technique; and

FIG. 17 is a schematic diagram of a plasma etching apparatus of the type to which the invention is applied.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail hereinbelow.

FIG. 17 is a schematic diagram of a plasma treatment apparatus of the type to which the invention may be applied. The apparatus of FIG. 17 is an etching apparatus employing a plasma generating method using electron cyclotron resonance produced by a microwave. The invention also can be applied to apparatuses of other systems as long as it is a plasma treatment apparatus, and so the invention is not limited to the apparatus of FIG. 17.

Shown in FIG. 17 are an etching chamber 1; a substrate 2 placed on an electrode 3; an RF generator 4 for applying an RF bias to the substrate; a wave guide 5 for guiding a microwave to the etching chamber 1; a quartz window 6; an electromagnetic coil 7 for forming an electron cyclotron resonance region in the etching chamber by applying a magnetic field to the microwave; a vacuum pump 8; a pressure regulating valve 9; and a sensor 10, such as a pressure sensor.

The electrode 3 is an electrostatic adsorption electrode and a part of the electrode surface serves as an electrostatic adsorption face which is in contact with the back face of the substrate 2. As shown in FIGS. 2 and 3, recessed parts 34, 35, and 36 are formed between annular electrostatic adsorption faces 31, 32, and 33 of the electrostatic adsorption electrode 3. Reference numeral 38 denotes a supply port for the supply of a heat transfer gas to the back face of the substrate, and 39 indicates a passage to carry a medium for cooling the electrode. The depth (d) of the recessed parts 34, 35, and 36 becomes smaller as one goes from the center to the outer side of the electrostatic adsorption electrode 3 in accordance with the order of d3>d2>d1. In the case where trenches are formed on the electrostatic adsorption face in place of the recessed parts, it is sufficient to decrease the depth from the center to the outer side of the electrostatic adsorption electrode 3.

As mentioned above, since the depth (d) of the recessed parts 34, 35, and 36 is decreased from the center to the outer side of the electrostatic adsorption electrode 3, the electrostatic adsorption electrode 3 has the function of maintaining the temperature in the central part of the substrate at the time of etching treatment so that it is higher than that in the peripheral part, as shown in FIG. 1. When the temperature in the central part of the substrate is high at the time of etching treatment, the deposition probability of the reaction products becomes low. Consequently, even if the amount of re-irradiation of the reaction products is large, the amount of the reaction products deposited on the side walls of the etched part decreases. The difference between the high and low temperatures of the substrate is adjusted so that the amount of the reaction products deposited on the side walls of the etched part is uniform. In this manner, as will be described hereinbelow, the etching characteristics in the substrate plane can be uniformized.

The mechanism of the plasma treatment will be described by an etching operation applied to an aluminum wiring film as an example.

FIG. 4 is a schematic diagram showing an aluminum wiring film that is being etched. As an aluminum wiring, a film 22 for preventing diffusion, called a barrier, is formed on an SiO₂ oxide film 21 as an underlayer. On the film 21, an aluminum wiring film 23 is formed. The barrier 22 is made of Ti or TiN and the aluminum wiring is made of an alloy such as Al—Cu or Al—Si—Cu. The composition ratio of Cu and Si or Cu is usually about 0.5 to 1.5%.

Further, a cap layer 24 made of TiN or the like is formed on the aluminum wiring. The cap layer 24 has thereon a resist 25. Since light reflected directly from the aluminum wiring is too strong when a fine pattern is exposed by lithography, the cap layer 24 is provided as a reflection preventing film for preventing deterioration in the resolution of the exposure.

The aluminum is etched using chlorine gas. Usually, since it is also necessary to etch a natural oxide film of aluminum, a mixed gas of BCl₃/Cl₂ is used. Aluminum and chlorine evaporate as Al₂Cl₆. This reaction easily occurs even at an ordinary temperature and progresses even when chlorine gas and aluminum come into contact with each other.

As shown in FIG. 4, therefore, when intending to obtain a vertical shape anisotropically by using the resist as a mask, the side walls of the aluminum wiring film have to be prevented from being etched. In the plasma etching, however, since the mixed gas of BCl₃/Cl₂ reaches a plasma state, in addition to Cl ions and the like, neutral activated species such as Cl radicals are generated. Since the neutral activated species are not influenced by the electric field or the magnetic field, they flit about in random directions in the etching chamber and a number of them are directed at the side walls. Consequently, the reaction between the Cl radicals and the aluminum side walls has to be prevented. A side wall protection layer 26 functions to prevent this.

Although the Cl radicals and Al react with each other, in order to obtain a vertical shape and to perform etching at a higher speed, an RF bias is applied by the RF generator 4 to the substrate 2, thereby allowing ions to be directed vertically at the substrate. The ions are accelerated by the RF bias, reach a high energy state, and are directed at the etching bottom of the aluminum wiring film. By ion irradiation, Cl adsorbed on the etching bottom promptly reacts with Al. Etching in which the ion kinetic energy is transformed to the reaction between Cl and Al on the etching bottom is called ion assisted etching.

The aluminum etched on the bottom is released as reaction products into the vapor phase. A part of the reaction products dissociates again in the plasma and is again directed at the substrate. Since the resist is likewise etched, the substrate is also irradiated with the reaction products of the resist. Electrically neutral species among species which are obtained by dissociation of those reaction products in the plasma are directed also at the side walls of the etched part. Such species, such as species obtained by etching the bottom face and which are directly deposited on the side walls, species directed at the side walls sputtered by the incident ions including physical or chemical elements, and the like, are deposited, thereby forming the side wall protection layer. Among them, due to the re-irradiation of the reaction products, non-uniformity in the plane of the substrate easily occurs for the following reason. The reaction products released into the vapor phase by the etching are exhausted as a gas from the etching chamber. As described with reference to FIG. 16, the reaction products on the outer periphery of the substrate are more efficiently exhausted. When the substrate temperature distribution is uniform in the plane, inevitably, the density distribution of the reaction products in the vapor phase is higher over the center of the substrate and is lower in the peripheral part thereof.

According to the invention, therefore, by setting the temperature in the central part of the substrate higher, as shown in FIG. 1, the deposition probability of the reaction products is changed in the plane of the substrate, as shown in FIG. 5, and the deposition amount of the reaction products serving as the side wall protection layer is uniformized in the plane of the substrate. That is, the deposition probability of the reaction products is set to be low in the central part of the plane of the substrate and is set to be high in the peripheral part thereof. As a result, the thickness distribution characteristic of the side wall protection layer can be uniformized in the plane of the substrate, as shown in FIG. 5.

In order to obtain the characteristic to make the temperature in the central part of the substrate higher as compared with that in the peripheral part of the substrate, for example, the depth (d) of the recessed parts 34, 35, and 36 (or trenches) decreases sequentially from the central part to the outer side of the electrostatic adsorption electrode 3.

FIG. 7 shows the relation between pressure (Pa) on the back face of the substrate and the overall heat transfer coefficient (W/m²×K) by the gas molecules. It will be understood from FIG. 7 that the higher the pressure on the back face is, the larger the overall heat transfer coefficient is. Consequently, the relation between the distance (d) between the back face of the substrate and the surface of the electrode and the overall heat transfer coefficient by the gas molecules when the pressure is set to be constant is obtained as shown in FIG. 8.

Using the characteristics of FIG. 8, therefore, by setting a varying depth (d) of the recessed parts 34, 35, and 36 (or trenches) on the surface of the electrostatic adsorption electrode from the center to the outer side, the temperature distribution as shown in FIG. 1 can be obtained.

In practice, it is sufficient to set the depth (d) of each of the recessed parts 34, 35, and 36 (or trenches) on the surface of the electrostatic adsorption electrode so that the deposition amount of the reaction products in the plane of the substrate can be maintained at an in-plane uniformity of ±10%.

The method according to the invention can be especially effective when applied to a case where the diameter of the substrate is 200 mm or larger and a pattern formed on the substrate is 0.35 μm or smaller.

In order to set the depth (d) of the recessed parts 34, 35, and 36 (or trenches) on the surface of the electrostatic adsorption electrode so as to be changed from the center to the outer side, as shown in FIG. 9, it is also possible to preliminarily set the depth of the recessed parts to be uniform and to adjust the depth thereafter by arranging spacers 37 having different thicknesses.

Instead of changing the thickness of the spacers 37, it is also possible to change the thermal conductive characteristics by coating the gap (trench) between the electrode surface and the substrate with a polyimide film or the like, thereby obtaining a predetermined temperature distribution in the plane of the substrate. Further, the temperature can be changed according to the processes by adjusting the kind or thickness of a film. By sticking the film again, cleaning can be easily done. The film does not have to be made of plastics material, but can be made also of a metal or ceramics.

As shown in FIG. 10, the width W (W1, W2, and W3) of the recessed parts 34, 35, and 36 (or trenches) on the surface of the electrostatic adsorption electrode is changed so as to become narrower from the center of the electrode to the outer side thereof, thereby making it possible to obtain a temperature distribution in the plane of the substrate as shown in FIG. 1. Further, as shown in FIG. 11, both the depth (d) (d1, d2, d3) and the width W (W1, W2, W3) of the recessed parts 34, 35, and 36 (or trenches) on the electrostatic adsorption surface are sequentially changed from the center of the electrode to the outer side, thereby making it possible to obtain the temperature distribution in the substrate plane as shown in FIG. 5.

Another method also can be employed. As shown in FIG. 12, the temperature in the substrate 2 is measured by sensors 42, 43, and 44 and the pressure of gas for heat transfer, which is supplied between the substrate 2 and the electrode 3 via the passage 38, is controlled by a valve 46 via a controller 45 on the basis of the measured temperatures, thereby making it possible to obtain the temperature distribution in the plane of the substrate as shown in FIG. 1.

The pressure of the gas for heat transfer to the back face of the substrate can be increased by increasing the flow of the heat transfer gas. On the other hand, the pressure to the back face and the overall heat transfer coefficient have the relation as shown in FIG. 13. The depth of the recessed part (or trench) of the electrostatic adsorption electrode 3 and the pressure loss (Pa) on the back face of the electrode have the relationship as shown in FIG. 6. It will be understood from FIG. 6 that the larger the trench depth (d) is, the smaller the pressure loss ΔPa is. Consequently, the supply pressure of the heat transfer gas is adjusted so that a pressure loss occurs due to the shapes of the radial recessed parts or trenches of the electrostatic adsorption electrode 3 which communicate with the recessed parts 34, 35, and 36, and the pressure of the heat transfer gas to the recessed parts 34, 35, and 36 is properly regulated, thereby making it possible to obtain the temperature distribution in the substrate plane as shown in FIG. 1.

Independent passages for supplying the heat transfer gas also can be provided for the respective recessed parts 34, 35, and 36 so that the pressures of the heat transfer gas supplied to the recessed parts 34, 35, and 36 can be adjusted.

Further, as another embodiment of the invention, as shown in FIG. 14, by etching the substrate 2 while regulating the exhaust amount of the reaction products from the etching chamber 1 by exhaust means 50, the deposition amount of the reaction products can be made uniform in the substrate plane.

A method of adjusting a process gas in order to uniformize the deposition amount of the reaction products in the substrate plane during the etching will now be described. That is, the process gas is adjusted by changing the parameters in the range and the manner described below.

• • (1) kinds of gasses: BCl₃, Cl₂
    • addition gases: CHF₃, CF₄, CH₂F₂, Ar+CH₄
  • (2) gas flow rate
    • BCl₃; 10 ml/min to 100 ml/min
    • Cl₂; 50 ml/min to 400 ml/min
  • (3) gas pressure: 0.1 Pa to 6 Pa
  • (4) microwave (2.45 GHz) output: 200 W to 2000 W
  • (5) RF output: 10 W to 500 W (frequency to be used: 100 KHz to 13.56 MHz)
  • (6) substrate temperature range: 50° C. to 100° C.
  • (7) resist is used as a mask

Within the above parameter adjustment range, in order to reduce the difference (the density in the center of the substrate is high and that in the peripheral part is low) in the density distribution of the reaction products in the plane, the following methods can be used.

(1) reduction in the gas pressure (0.1 Pa to 1 Pa)

The gas pressure is lowered, the gas residence time is shortened, and the volatility of the products is increased, thereby reducing the number of re-deposition times of the reaction products after etching. In such a state, since the number of collisions with other gas molecules is small in both the center and the peripheral part of the substrate until the reaction products are exhausted, a difference does not easily occur between the exhaust speed in the center of the substrate and that in the peripheral part. Consequently, the variation in the deposition amount distribution of the reaction products in the plane of the substrate is reduced.

(2) increase in both the gas flow rate and the chlorine flow ratio (>80%)

By shortening the gas residence time by an increase in the flow rate, the volatility of the products is increased and the number of deposition times of the reaction products after etching is reduced.

By reducing BCl₃ ions having a large mass, the amount of deposition on the side walls from the resist by the ion attack is decreased, thereby reducing the variation in the in-plane reaction product deposition density distribution.

(3) increase in the whole substrate temperature (70° C. to 100° C.)

By increasing the temperature of the whole substrate, the number of re-deposition times can be reduced.

Although the increase itself in the substrate temperature does not directly contribute to solve a solution in-plane vibration problem, when the temperature in the substrate is controlled, for example, when the substrate temperature is increased, the probability of deposition of the irradiated reaction products decreases. Consequently, the deposition amount itself of the in-plane reaction products is reduced, so that the absolute value of the variation in the deposition density distribution of the reaction products in the substrate plane can be reduced.

(4) reduction in the plasma density (decrease in the microwave output)

By lowering the density of the plasma, the amount of reaction products is suppressed and the variation in the in-plane reaction product deposition density distribution is reduced.

(5) reduction in the energy of ions directed at the substrate (decrease in the RF output)

By decreasing the RF output, the amount of the deposition on the side walls from the resist by the ion attack is reduced and the variation in the in-plane reaction product deposition density distribution is reduced.

By optimizing the parameters so as to be applicable to various areas to be etched, preferably, to a wiring process of a semiconductor in which the diameter of the substrate is 200 mm or larger and a pattern formed on the substrate is 0.35 μm or smaller, etching which does not cause a variation in the processing dimension in the plane of the substrate can be performed.

Also, in so-called dense and sparse patterns in which fine patterns and sparse patterns which are not so fine mixedly exist in almost the same place on the substrate, the variation in the processing dimension can be reduced. That is, the finer the pattern becomes, the more the incident particles enter deep inside the pattern and the probability of deposition on the side walls is reduced, so that the side wall protection layer becomes thinner. According to the invention, however, the uniformity in the dense and sparse patterns can be also achieved in a way similar to that of the uniformization of the side wall protection layer in the plane of the substrate.

As mentioned above, according to the invention, a plasma treatment method and a plasma treatment apparatus can be provided, in which the influence exerted on the etching characteristics of the reaction products during the plasma treatment is offset and uniform treatment characteristics in the substrate plane are obtained.

According to the invention, the in-plane distribution of the plasma treatment characteristics can be uniformized by a simple method, for instance, by changing the temperature in the substrate plane, so that an effect can be attained wherein the yield of the devices is improved. Since the substrate temperature can be changed according to the process, there is also an advantage that the invention is applicable to various specifications in the treatment of etching or the like.

According to the invention, further, a plasma treatment method and a plasma treatment apparatus can be provided, which can obtain etching treatment characteristics causing no variation in the processing dimension in the dense and sparse patterns.

Claims

1. A plasma treatment apparatus for etching a substrate to be processed by using a gas plasma in a treatment chamber, comprising: an electrode disposing the substrate to be processed thereon; a vacuum pump for exhausting reaction products obtained by etching and releasing into a vapor phase as a gas from the treatment chamber; the vacuum pump providing a more efficient exhaustion of the reaction products from the outer periphery and redistributing the amount of reaction products between the central part of the substrate and the peripheral part of the substrate; and a controller for regulating pressure of the heat transfer gas supplied to each part between the substrate and the electrode by independent passages provided for the respective parts to which the heat transfer gas is supplied, and for controlling a temperature distribution in a plane of the substrate to be processed to increase the temperature in the central part greater than that of the peripheral part to provide increased uniformity of the re-irradiation effect of the reaction products.

2. A plasma treatment apparatus for etching a substrate to be processed by using a gas plasma in a treatment chamber according to claim 1, wherein the vacuum pump provides more efficient exhaustion of the reaction products from substantially the entire outer periphery.