JP3076641B2 - Dry etching apparatus and dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus and a dry etching method used in a manufacturing process of a semiconductor integrated circuit or the like.

[0002]

2. Description of the Related Art A dry etching technique is one of the semiconductor manufacturing techniques. In this etching, a parallel plate type electrode structure is conventionally used, for example, an RI in which a substrate is placed on a cathode.
An E type device or the like is used.

One of the conditions for obtaining a highly anisotropic etched shape in the RIE method is that the pressure of the etching gas is sufficiently low to suppress scattering of ions incident on the substrate due to collision with molecules. . However, when the pressure is reduced, the etching active species in the gas phase are also reduced, so that the etching rate is reduced. For this reason, in order to increase the number of processed wafers per time, it is conceivable to process a plurality of wafers at the same time. However, there is a problem that the etching apparatus inevitably becomes large. Since semiconductor devices are generally manufactured in a clean room, an increase in the installation area of the device leads to an enormous increase in clean room maintenance costs, which increases the device manufacturing costs.

[0004] In this respect, in the magnetron etching apparatus, the number of times that electrons perform cycloidal motion and collide with molecules to ionize the molecules increases due to the interaction between the magnetic field and the electric field of the plasma sheath orthogonal to the magnetic field. Even at a low pressure (10 ^-2 to 10 ^-3 Torr), a high etching rate (1 μm / min) can be obtained, and a short processing per one substrate can be performed, thereby improving the etching reliability. Also,
Since the average energy of ions is also reduced, there is an advantage that irradiation damage to the wafer is reduced.

[0005]

However, in the conventional magnetron etching method, the uniformity of the etching rate is deteriorated due to the non-uniformity of the strength and direction of the magnetic field, and the directionality of ions is disturbed. There is a problem that the light is obliquely incident on the substrate and makes etching with high anisotropy difficult.

FIG. 5 is a schematic view showing an example of a conventional magnetron etching apparatus.
2 form a pair of parallel plate electrodes,
A silicon wafer 14 as an object to be processed is placed on the reference numeral 0. On the back surface of the counter electrode 12, two permanent magnets 16, 16 'whose thickness direction is the magnetization direction are provided,
These are magnetically coupled via the yoke 18,
It is driven to rotate about the rotation shaft 18a. In the apparatus as described above, etching with high anisotropy can be performed at the central portion B of the wafer as shown in the cross-sectional view B of FIG. A in FIG.
As shown in the C cross-sectional view, an inclined shape having poor anisotropy results.

Although the cause of such deterioration of the machined shape is not strictly clear, the following mechanism can be considered.

That is, the lines of magnetic force formed at the peripheral portion of the wafer 14 are, as shown by dotted lines in FIG.
4 are not formed parallel to the surface, but form a loop. In the plasma, the electric field is relatively small, so that the electrons are strongly affected by the magnetic field, and perform a spiral motion having a radius of about 1 mm so as to surround the lines of magnetic force. Therefore, when the magnetic field lines and the wafer 14 intersect, electrons enter obliquely along the magnetic field lines. On the other hand, since ions directly involved in the etching reaction have a large mass, the effect of directing the direction of movement by the magnetic field is small. But,
When an electron is obliquely incident on the groove of the substrate being processed, it hits only one of the walls, so that the electric charges accumulated on the left and right walls are not equal. It is considered that as a result of the asymmetry of the charge, an electric field newly generated in the left and right directions of the wall acts on the ions to bend the direction of movement, thereby deteriorating the shape anisotropy.

On the other hand, as shown in FIG. 6A, if the permanent magnets 16 and 16 ′ are arranged on both ends of the parallel plate electrode formed by the substrate electrode 10 and the counter electrode 12, Can be supplied with a more parallel magnetic field. Therefore, in this case, an etched shape with high anisotropy as shown in FIG.

However, when the permanent magnets 16 and 16 'are arranged as shown in FIG. 1A, it is not possible to rotate the permanent magnets 16 and 16' due to the positional relationship of the wafer transfer mechanism and the like. It is extremely difficult. On the other hand, unless the permanent magnets 16 and 16 'are driven to rotate, it is impossible to achieve uniform etching. Also, with this configuration, the wafer 1
To realize a uniform magnetic field on the four surfaces, the permanent magnets 16, 16
'Must be quite large.

Further, an apparatus has been proposed in which coiled electromagnets are arranged at both ends of a vacuum processing chamber in place of the permanent magnets 16 and 16 '. This device is characterized in that the direction of the magnetic field can be rotated by passing an alternating current with a phase shift of 90 ° to two sets of coils that are orthogonal to each other. However, in order to supply a uniform magnetic field to the entire surface of the wafer, it is necessary to make the diameter of the coil sufficiently large with respect to the interval between the coils, that is, the size of the container. The larger the diameter of the wafer, the larger the coil becomes. There is a problem that can not be obtained. At the same time, the current flowing through the coil also increases, and the power supply increases. In addition, a strong magnetic field extends to unnecessary parts inside and outside the container, making it impossible to use electronic and mechanical parts that are sensitive to magnetism and requiring magnetic shielding to the outside of the device. .

It is an object of the present invention to form a uniform magnetic field over a wide area of the electrode surface with a relatively small magnet, thereby maintaining a uniform plasma over the entire wafer surface. Along with providing a high-precision dry etching apparatus, the object to be processed such as a metal such as silicon, metal silicide, an insulator, aluminum, tungsten, or copper or a metal alloy can be accurately and low-produced using the dry etching apparatus. An object of the present invention is to provide a dry etching method which can be processed by damage.

[0013]

The gist of the present invention is to enable a uniform horizontal magnetic field to be supplied to a wafer surface in dry etching using a magnetron discharge, and to use a magnetron discharge by an electric field orthogonal to the magnetic field. Is generated.

That is, in the dry etching apparatus according to the first aspect of the present invention, a vacuum vessel, a first electrode on which an object to be processed is placed in the vacuum vessel, and a second electrode facing the first electrode are provided. Parallel electrodes comprising electrodes, means for introducing an etching gas into the vacuum vessel, and main magnetic poles of opposite polarity provided on both end faces of the magnet block, and the magnet blocks on both end faces have a stepped or tapered shape. a magnetic field generating magnetic circuit recess is formed, and the recess is disposed relative to the rear surface of the second electrode recessed, the magnetic
Means for rotating a field generating magnetic circuit about a rotation axis; and means for applying an electric field to at least one of the electrodes, wherein a discharge is induced between the parallel electrodes to etch the object to be processed. And A dry etching apparatus according to a second aspect of the present invention is the dry etching apparatus according to the first aspect, wherein a vertical component of the magnetic field applied between the electrodes by the magnetic field generating magnetic circuit on the surface of the workpiece is 1/1 / the horizontal component. It is characterized by being suppressed to 4 or less. According to a third aspect of the present invention, in the dry etching apparatus according to the first aspect, the first electrode has an area larger than the object to be processed, and a portion where the object is not placed. Is a conductive material or 1 mm thick
It is characterized by being covered with the following insulator.

According to a fourth aspect of the present invention, in the dry etching method, an etching gas is introduced into a vacuum vessel, and an object to be processed is placed on a first electrode provided in the vacuum vessel. On the back side of the second electrode facing the first electrode, both end faces of the magnet block have main poles of opposite polarity, and the magnet block between the both end faces is recessed in a stepped or tapered shape. A magnetic field generating magnetic circuit in which a concave portion is formed and a compensating magnetic pole having a polarity opposite to that of the main magnetic pole is provided on a surface of the concave portion behind the main magnetic pole to generate the magnetic field.
By rotating a magnetic circuit , a substantially parallel magnetic field is generated in the vicinity of the first electrode, and an electric field is applied between the electrodes to induce a discharge to etch the workpiece. A dry etching method according to a fifth aspect of the present invention is the dry etching method according to the fourth aspect , wherein a vertical component of the magnetic field on the first electrode surface is suppressed to １ ／ or less of a horizontal component. A dry etching method according to a sixth aspect of the present invention is characterized in that, in the fourth aspect , the pressure of the etching gas is controlled to 10 −2 Torr or more. A dry etching method according to a seventh aspect of the present invention is the dry etching method according to the fourth aspect , wherein the temperature of the first electrode is controlled, and the object to be processed is attached to the first electrode by using an electrostatic chuck. It is characterized in that the temperature of the object to be processed is controlled by securing the thermal contact by fixing. An eighth aspect of the present invention is directed to the dry etching method according to the fourth aspect , wherein the etching gas is a mixed gas containing at least either hydrogen or helium.

[0016]

[0017]

[0018]

According to the first and fourth aspects of the present invention, the magnetic field generating magnetic circuit has a stepped shape with both end surfaces in the magnetization direction as walls.
Alternatively, since the magnetic block is formed of a magnet block having a concave portion depressed in a tapered shape, the lines of magnetic force formed between the inner surface and the outer surface of the wall surface can be trapped near the apex of the wall portion.

The curved lines of magnetic force formed between the opposed inner surfaces of the wall portion are also trapped in the concave portions formed in the magnet block.

As described above, in the magnetic field generating magnetic circuit, the lines of magnetic force having a relatively small radius of curvature can be confined only in the vicinity of the magnet, so that one of the opposing wall surfaces of the concave portion is more confined to the other outer wall surface. It is possible to obtain a long magnetic field line in a parallel region toward the head.

Therefore, by arranging the concave portion relative to the wafer, a uniform horizontal magnetic field can be supplied over the surface of the wafer.

Next, an experiment conducted to clarify the effect of the direction of the magnetic field lines on the processed shape will be described. In this experiment, as shown in FIG. 7A, etching was performed using an experimental apparatus similar to that shown in FIG. 6A with the magnet inclined with respect to the electrode.

FIG. 7B shows the inclination of the processed shape at the center of the wafer, that is, the cross section B, with respect to the inclination θ of the magnet with respect to the electrode surface. As for the inclination of the shape, θ is 1
When the angle is 5 ° or less, it is negligibly small. When the angle is 5 ° or less, the angle rapidly increases with θ. Therefore, it is possible to achieve extremely directional etching by keeping the inclination between the high-precision magnetic field and the wafer surface at 15 ° or less, that is, the ratio of the vertical component of the magnetic field to the horizontal component at tan15 ° = 1/4 or less. Was found. Therefore, according to each of the second and fifth aspects of the invention, the vertical magnetic field component can be suppressed to １ ／ or less of the horizontal magnetic field. According to the third aspect of the present invention, the gradient of the plasma density tends to be large at the electrode end in the direction perpendicular to the line of magnetic force, and the uniformity and the anisotropy of the processed shape tend to be impaired. . Therefore, the first
By making the electrode large, it is possible to prevent the influence of non-uniformity of the end of the electrode from affecting the processing, and to improve the uniformity of the etching rate in the direction orthogonal to the line of magnetic force. In particular, at the end of the electrode on which the object is not placed, the applied electric field is distributed.
The electric field in the peripheral portion is reduced. For this reason, it is necessary to use an electrode larger than the object to be processed in terms of uniformity and prevention of gate destruction. Further, it is desirable that the electrode end portion is formed up to the surface with a conductive material such as metal or carbon. However, when an insulator is unavoidably used to protect the electrodes and prevent contamination of the object to be processed, it is desirable to minimize the thickness to 1 mm or less .

According to the sixth aspect of the present invention, in a configuration in which the parallel magnetic field in the horizontal direction that is uniform with respect to the surface of the workpiece and the electric field generated between the electrodes are orthogonal to each other, the electrons are converted into both the magnetic field and the electric field Perform a drift motion in the orthogonal direction. For this reason, a bias in the electron density occurs on the electrode surface in a direction orthogonal to the magnetic field. Since electrons collide with molecules and promote ionization, the higher the electron density, the higher the frequency of ionization. In addition, when there is a bias in the density of electrons having negative charges, positive ions are attracted to maintain electrical neutrality, so that the density of plasma increases. Therefore, the bias of the electrons due to the drift motion causes non-uniform discharge.

The electron density is smallest at the end of the electrode opposite to the direction of the drift movement, increases in the direction of movement, and becomes largest at the end of the electrode on the side of movement. Therefore, in the dry etching method according to the sixth aspect of the present invention, by increasing the pressure of the etching gas to a certain level or more and sufficiently increasing the mean free path of electrons, it is possible to increase the frequency of collision between electrons and molecules, To increase the plasma density gradient.

[0026] That is, in the dry etching method according to claim 6, together with obtaining a magnetic field parallel to the wafer, the pressure of the etching gas by setting the pressure of more than 10 @ -2 Torr, better uniformity of discharge As a result, fine processing with excellent anisotropy of the processing shape and uniformity of the etching rate becomes possible.

At the above gas pressure, a large amount of activated radicals and atoms other than ionized particles are present in the plasma. These particles also contribute to the etching reaction and have a significant effect on the processed shape and the etching rate, but the reaction is extremely sensitive to the temperature of the substrate. Therefore, it is possible to improve the processing accuracy by precisely controlling the temperature of the substrate in the above invention, by controlling the processing shape to be tapered or vertical, or by improving the selectivity by cooling to a low temperature. it can. Claim 7
According to the invention described in (1), the temperature of the first electrode is controlled, the object to be processed is fixed using an electrostatic chuck, and the temperature difference between the object to be processed and the first electrode is suppressed to, for example, 5 ° C. or less. be able to. Thereby, as shown in Table 2, for example, the selectivity is improved, and the effect is particularly large when the temperature of the object to be processed is 0 ° C. or lower, and the processed shape can be made favorable by reducing the undercut.

According to the eighth aspect of the invention, when the electron density is uneven, the local electric neutrality in the plasma is not perfect, the drift direction is negative, and the opposite direction is positively charged. . Even if the charge amount is small, an electric field is generated in a direction parallel to the electrode, and the direction of ions which should be incident perpendicularly is inclined to cause deterioration of anisotropy.

In order to alleviate such bias of electric charge, it is effective to add an element having a relatively small mass to the etching gas. That is, when hydrogen or a light element gas such as helium is added to a heavy element that directly contributes to the etching reaction, highly mobile hydrogen ions and helium ions are generated. Even if a lateral electric field is generated due to the bias of the electron density, these light ions move quickly, neutralize the electric charge, and have an effect of shielding the electric field. Therefore, ions having a large mass, such as heavy elements, are not significantly affected by the electric field in the lateral direction and are incident perpendicularly on the substrate. In addition, since the charge of electrons is neutralized by light element ions that do not contribute much to the etching reaction, heavy elements that have large mass and are difficult to move
Has a function of improving the uniformity of the etching rate by making the ion concentration gradient gentler.

[0030]

[0031]

[0032]

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the dry etching apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram thereof.

In FIG. 1, the vacuum processing chamber 20 can be evacuated to a degree of vacuum of about 10 ⁻⁶ Torr, for example, and a lower electrode 22 is supported inside the vacuum processing chamber 20. The upper plate 24 on the wall of the processing chamber 20 constitutes a parallel plate electrode. The lower electrode 22 is provided with temperature control means (not shown), and the wafer is fixed using an electrostatic chuck, so that the temperature difference between the wafer and the electrode can be suppressed to 5 ° or less. .

The vacuum processing chamber 20 is provided with a gas inlet 20a through which an etching gas can be introduced, so that the etching gas can be introduced into the parallel plate electrode.

In this embodiment, the anode coupling (P
E) or cathode coupling (RIE) can be selected as an alternative, and the lower electrode 22 is grounded via a switch 26a or connected to a high frequency power supply 28a. On the other hand, the upper electrode 24 is connected to the grounded state,
The voltage application state by b can be switched via the switch 26b.

When a high-frequency voltage is applied to the upper electrode 24 by the high-frequency power supply 28b and the lower electrode 22 is grounded, the device operates as a PE system. On the other hand, when a high frequency voltage is applied to the lower electrode 22 by the high frequency power supply 28a, the device operates as an RIE method.

On the back side of the upper electrode 24, a permanent magnet 30 having a stepped concave portion 32 is supported by a magnet holder 34 made of a non-magnetic material, for example, aluminum, and is connected to the magnet holder 34. By driving the rotating shaft 36 of the non-magnetic material, the permanent magnet 30 can be driven to rotate.

Next, the details of the permanent magnet 30 will be described with reference to the top view and the cross-sectional view of FIGS. 2A and 2B. The stepped recess 32 is formed on both sides in the magnetization direction as walls, and the depth of the stepped recess 32 increases stepwise from the end toward the center. It is configured to be deep in shape. As shown in FIG. 2A, the permanent magnet 30 has an oval shape, its longitudinal axis direction is used as a magnetization direction, an outer surface of a wall on one side in this magnetization direction is used as an S pole, and the other is used as an S pole. The outer surface of the wall is magnetized so as to have an N pole. The permanent magnet 30 according to the present embodiment is configured by assembling small pieces of ferrite as shown in FIG. 2A, and then magnetizing the pieces according to the magnetization direction.

By forming the stepped concave portion 32 in the permanent magnet 30, the first step wall portion 40 and the second step wall portion 4 each having a step in the vertical direction are provided at both ends in the magnetization direction.
Second, four-stage wall portions of a third step wall portion 44 and a fourth step wall portion 46 are formed. Then, the outermost first step wall portion 4
With respect to 0, the horizontal step portion 48 is formed such that the distance between the opposing first step wall portions 40, 40 becomes shorter toward both sides of the longitudinal center axis of the permanent magnet 30.
This is to prevent the magnetic field intensity from decreasing as the distance from the central axis increases. Here, the first to fourth step wall portions are magnetized with magnetic poles having polarities opposite to the magnetic poles on the back surface.

Next, the operation will be described.

As shown in FIG. 2B, there are roughly three types of magnetic lines of force formed on the permanent magnet 30 having the stepped recess 32. The first magnetic line of force 50 is a magnetic line of large curvature formed between the inner surface and the outer surface of the first step wall portion 40. The first magnetic line of force 50 is formed near the top surface of the first step wall portion 40. From the surface of the permanent magnet 30, for example, 5
The magnetic field on the wafer 14 set at a distance of 2 mm has no influence. The second magnetic line of force 52 is a magnetic line of force formed between the opposing surfaces of the walls 40 to 46 of each step, and most of the second magnetic line of force 52 is formed by the stepped recess 32 formed in the permanent magnet 30. And has no effect on the magnetic field similarly formed in the vicinity of the wafer 14. In this embodiment, the third magnetic field lines 54 are used as a parallel magnetic field formed near the wafer 14. The third magnetic lines of force 54 are formed on the outer surface of the permanent magnet 30 at both ends in the magnetization direction, and the magnetic field formed at a position facing the wafer 14 is a magnetic field parallel to the surface of the wafer 14. I have. Therefore, when electrons spinning about the third magnetic line of force 54 as a central axis jump out in the tangential direction, the electrons are symmetrically incident on the groove being processed, so that highly anisotropic etching can be performed. . In particular, such an effect can be achieved by forming the above-mentioned parallel third magnetic lines of force 54 in a discharge dark portion (sheath portion) formed in the vicinity of the wafer 14 so that etching with higher anisotropy can be performed. confirmed. Moreover, in this embodiment, the magnetic flux density on the surface of the wafer 14 is reduced to about 100 G while forming the permanent magnet 30 with a relatively inexpensive material such as ferrite.
And a parallel magnetic field of sufficient strength necessary for magnetron etching can be formed.

In this embodiment, since the permanent magnet 30 as described above is set on the back side of the upper electrode 24, the permanent magnet 30 is located at a position different from the mechanism for carrying the wafer 14 in and out of the magnetron etching apparatus. The permanent magnet 30 can be disposed, and therefore, a mechanism for rotating the permanent magnet 30 can be easily adopted. Thus, the permanent magnet 3
By rotating 0, the parallel magnetic field formed as described above is rotated on the surface of the wafer 14, and as a result, the intensity of the parallel magnetic field can be set almost uniformly on the wafer 14. As a result, uniformity of the etching rate over the entire surface of the wafer 14 can be ensured.

[0044]Comparative example  The present inventors initially thought that a magnetron magnet as shown in FIG.
A switching device was prototyped. This device is the same as the device shown in FIG.
The difference is that it is arranged on the back side of the upper electrode 24.
The permanent magnet has a configuration as shown in FIG.
As shown in the figure, both ends of a yoke 60 made of iron or the like are provided.
Fixed curved permanent magnets 62 with a predetermined height H to the ends
A non-magnetic material such as aluminum is provided at the center of the yoke 60.
A rotating shaft 64 made of a material or the like is fixed. Said yo
The magnetic force generated from the lower surface of the permanent magnets 62
The thickness is formed so as to be saturated with the line. And Yo
The thickness of the magnet 60 and the shape of the permanent magnets 62, 62 are selected as desired.
By setting, an almost horizontal magnetic force on the surface of the wafer 14
And that the magnetic field density can be uniform.
Was.

However, in the device shown in FIG. 3, the magnetic field intensity is absorbed by the yoke 62,
It is difficult to secure the intensity of the parallel magnetic field formed on the surface of the wafer 14 at a magnetic flux density of about 100 G, which is optimal for magnetron etching. Such a magnetic flux density cannot be secured when the permanent magnet 62 is formed of a relatively inexpensive ferrite material, and is 10 to 2 times larger than that of the ferrite magnet.
The permanent magnet 62 must be made of samarium-cobalt (SmCo), which is a rare earth whose cost is about 0 times.

Moreover, even when the expensive permanent magnet as described above was used, it was confirmed that the intensity of the parallel magnetic field and the uniformity of the magnetic field were inferior to those of the above-described embodiment.
In particular, as the diameter of the magnet decreases, it is disadvantageous to form a parallel magnetic field. However, according to the magnet 30 having the structure of the present embodiment, even when the diameter is 320 mm, the perpendicular component of the magnetic force lines on the end side of the wafer 14 is reduced. It was confirmed that it can be reduced as compared with the conventional case and can be suppressed to 1/4 or less of the horizontal magnetic field. As described above, this embodiment is superior to the comparative example in both cost and performance.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

The recesses formed in the permanent magnet 30 include:
The present invention is not limited to the four-step recessed portion 32 as in the above-described embodiment, and may be a one-stage recessed portion as long as the magnet is small. It was confirmed that the formation of the concave portions in multiple stages was more advantageous for forming a uniform parallel magnetic field than the steps. This is because the first and second lines of magnetic force 5 described above are formed by forming a multi-stage recess.
This is considered to be because the effect of confining 0 and 52 in the vicinity of the permanent magnet 30 or inside the recess is increased, and a more uniform parallel magnetic field can be formed. Further, the recess formed in the permanent magnet 30 is not limited to the one in which the depth of the recess changes in a stepwise manner as in the above-described embodiment. May be changed. However, the permanent magnet 3
When assembling 0 with small pieces of ferrite or the like, the stepped concave portion is easier to manufacture in consideration of the processing.

Next, an embodiment of a dry etching method according to the present invention using the above-described dry etching apparatus according to the present invention will be described by taking resist etching in a multilayer resist process as an example. The multilayer resist method is a means for maintaining high lithographic accuracy equivalent to that on a flat surface even on a substrate having an uneven surface. A typical example of the three-layer resist method is to apply a resist to a stepped surface, flatten the resist, then form an inorganic compound film such as spin-on-glass (SOG) as an intermediate layer, and then perform normal lithography. Burn the pattern in the process. Thereafter, the SOG and the resist side are sequentially etched by reactive ion etching (RIE) to form a pattern. As shown in the cross-sectional view of the process in FIG. 8A, the object to be processed used in this embodiment is a first layer resist 81 having a thickness of 2 μm, an already etched SOG 82 and an upper layer resist on a substrate 80. Reference numeral 83 denotes a laminate.

A constant pressure oxygen is introduced into the vacuum processing chamber of the dry etching apparatus shown in FIG. 1, and discharge is performed by a cathode couple system in which 13.56 MHz RF power is applied to the electrode on which the wafer is placed. Induced and processed.

First, in order to clarify the relationship between the magnetic field generated by the magnet (magnetic field generating magnetic circuit) and the etching characteristics, the etching rate distribution was measured with the rotation of the magnet stopped. FIG. 9 shows a pressure of 3.5 mTorr.
shows its distribution at r. (A) in the figure shows the distribution in the direction along the line of magnetic force, and although the distribution is higher at the periphery than at the center, the distribution is almost symmetrical. On the other hand, (B) in the figure
In the direction perpendicular to the lines of magnetic force indicated by, an asymmetric distribution increases monotonically to the left.

When the processed shape of the cross section along this direction was observed, as shown in FIG. 8B, the resist portion 84 of the thin repeated pattern was wide despite being processed vertically. In the resist portion 85 facing the groove,
It has been clarified that constriction occurs only on the side wall facing the direction in which the etching rate is high.

When the magnet is rotated, the etching speed is averaged, but the unevenness of the etching speed between the center and the periphery is not eliminated, and it is also clear that the periphery is higher than the center of the wafer. Further, although the processed shape becomes symmetrical by rotation, constriction of the side wall cannot be eliminated.

In the magnetron discharge, electrons perform cycloidal motion in the directions orthogonal to the electric field and the magnetic field, respectively, mainly due to the action of the electric field generated between the cathode and the plasma and the magnetic field component orthogonal to the electric field. This phenomenon has the effect of increasing the frequency of collision between electrons and gas molecules and increasing the density of plasma. At the same time, this causes a gradient of plasma density in a direction orthogonal to the magnetic field in the electrode surface, resulting in the non-uniformity of the etching rate and the asymmetry of the processed shape. In order to remove the non-uniformity, there is a method in which the concentric circles of the magnets make the streak of electrons in a cycloid motion a closed circuit and repeat the orbital motion.
Greater non-uniformity occurs between the electron passage and other parts. Further, it is impossible to sufficiently suppress the vertical magnetic field with a concentric magnet.

As described above, the gradient of the plasma density is the cause of the maximum non-uniformity of the etching rate and the processed shape. By suppressing this, the features of the etching apparatus according to the present invention can be maximized. Thus, an experiment was conducted on the effect of gas pressure, which strongly affects the uniformity of plasma.

First, the state of discharge in a direction perpendicular to the line of magnetic force was visually observed, and at 3.5 mTorr, the state of FIG.
As shown schematically in FIG. 2A, it was found that the portion 91 protruding outside the electrode 90 emits strong light. It is considered that such a strong light emitting portion 91 was generated by the concentration of electrons drifting on the electrode 90. Next, the gas pressure was increased to 25 to 50 mTorr.
When observed in the same manner with the temperature increased to r, as schematically shown in FIG. 10 (B), a strong light emitting portion 92 is generated in a sheath portion of about several mm over the entire cathode, and uniform discharge in the cathode surface is caused. It became clear that the sex was significantly improved. When the pressure increases, the frequency of collision between electrons and gas molecules drifting as a result of cycloidal motion increases, and the density of the plasma reaches a constant state over a relatively short distance, so that the state of discharge changes in this way. Conceivable.

FIG. 8C shows a processed shape of the resist etched by using the etching apparatus of FIG. 1 at a pressure of 50 mTorr. This means that the flow rate of the oxygen gas is 50 s.
ccm, RF applied power is 600W, diameter 150mm
Is the result of processing the wafer of FIG. No constriction of the side wall seen in FIG. 8B was observed at all, and it became clear that a processed shape with high anisotropy was obtained. As a result of closely observing the relationship between the processing shape and the pressure, the asymmetrical necking of the side wall was reduced to a practically acceptable level of 500 angstrom or less at a pressure of 25 mTorr or more. It became clear that there was a response. At a pressure of 125 mTorr or more,
It was also clarified that since the scattering of ions became intense, the constriction of the side wall was remarkable and started to occur irrespective of the direction and width of the pattern.

FIG. 11 shows the distribution of the etching rate at 50 mTorr. (A) shows the velocity distribution in the direction of the line of magnetic force, and (b) shows the velocity distribution in the direction perpendicular to this. In (b), there is no change in the tendency to increase toward the left, but the etching rate is improved as a whole and the uniformity is improved.

FIG. 12 shows the relationship between the uniformity of the etching rate and the discharge pressure when the magnet is rotated. As an index representing uniformity, a value obtained by dividing the difference between the maximum value and the minimum value by the average value was used. It is clear from the figure that the higher the pressure, the better the uniformity.

According to the present embodiment, when processing the resist using the dry etching apparatus of the present invention, the uniformity and processing can be achieved by setting the pressure of the etching gas within the range of 25 mTorr or more, and preferably 125 mTorr or less. It was shown that etching having an excellent shape was realized.

Next, a helium gas was added to oxygen to clarify the effect of adding a gas containing a light element to the etching gas. FIG. 13A shows an etching rate distribution in a direction perpendicular to the lines of magnetic force when the magnet is fixed. (A) uses a mixed gas of 100% oxygen and (b) a gas mixture of 33% oxygen and 67% helium as an etching gas, and the flow rate of oxygen gas is 50 scc, respectively.
m, a pressure of 50 mTorr, an applied power of RF of 400 W, and a result of processing a wafer having a diameter of 150 mm.
Comparing (a) and (b), it is clear that the addition of helium gas improves the uniformity although the etching rate is reduced by about 5% on average.
The uniformity when the magnet was rotated and etched was about 10% with oxygen alone, but was improved to 6% by adding helium.

Further, (a) and (b) of FIG.
Although the processed shape of the sample etched by rotating the magnet is illustrated in detail, in FIG.
Constriction of about 0 angstrom is observed, and it is clear that in FIG.

Since the helium ion has a small mass, even if it collides with the substrate, its physical action is slight. Also, it is extremely stable chemically and does not directly participate in the etching reaction. Nevertheless, the reason why the uniformity and the processed shape are improved is that the effect of the bias of the electron density inherent to the magnetron RIE having no closed circuit as in the dry etching apparatus of the present invention is reduced. Conceivable.

Next, the relationship between the object to be processed, the size of the electrode, and the material will be described. In the above embodiment, the electrode has a radius of 7
A wafer 15 mm larger in radius than a 5 mm wafer is used. The electrodes around the wafer play an important role in improving the uniformity of the etching rate. As a comparative example,
FIG. 11C shows the uniformity of the etching rate in the direction perpendicular to the lines of magnetic force when the size of the electrode and the wafer is the same. It is clear that the gradient of the speed at the left and right ends becomes more remarkable, and the uniformity is deteriorated.

Next, as another embodiment of the dry etching method of the present invention, a dry etching method in which the above-described cathode coupling type dry etching apparatus is applied to processing of a gate electrode of a silicon MOS LSI device will be described.

FIG. 14A is a sectional view of the object to be processed used in this embodiment. The object to be processed is the silicon substrate 1
After forming a silicon dioxide film having a thickness of 100 angstroms by thermal oxidation on polycrystalline silicon film
3 is deposited, doped with phosphorus, and a resist mask 104 is formed thereon. The polycrystalline silicon 103 doped with phosphorus is widely used as a constituent material of a gate electrode of a MOS capacitor or a MOS transistor. Here, the silicon dioxide film 102 is used as a dielectric. In the processing of the polycrystalline silicon film 103 having such a structure, the uniformity, the processed shape, the high selectivity to the underlying oxide film 102, and the like, as well as the gate oxide film 102, damage the insulating characteristics. Not required. Also, it is well known that if the uniformity of the plasma is not good, a strong electric field is generated in the oxide film 102 to easily cause dielectric breakdown.

An experiment was conducted to examine the relationship between the gas pressure, which has a great correlation with the plasma uniformity, and the breakdown voltage of the oxide film. The apparatus shown in FIG. 1 was used as the apparatus, chlorine was used as an etching gas, the high-frequency power applied to the electrodes was 150 W, the substrate temperature was 0 ° C., and the object was etched.
The MOS capacitor shown in FIG. 4 (b) was prepared, the current-voltage characteristics between the substrate and the gate polycrystalline silicon were measured, and the failure rate of the breakdown voltage was obtained.

Table 1 shows the results.

[Table 1] At a pressure of 5 mTorr (5 × 10 ⁻³ Torr), 10%
However, at 10 mTorr, it decreased to 7%, and at 40 mTorr or more, no defect occurred.
The reason for this is that the higher the pressure, the better the uniformity of the plasma is, and no electric field is generated in the gate oxide film 102 that may cause a defect. As a result of examining the presence / absence of gate breakdown in more detail, it was found that a pressure of 25 mTorr was the boundary of whether or not breakdown would occur. It was also confirmed that the uniformity of the etching rate was improved as the pressure was increased, as in the above-described resist etching example.

The selectivity to the oxide film is also higher as the pressure is higher, and is higher at 40 mTorr and at 80 mTorr,
A selectivity of 5 was obtained. On the other hand, the pressure is 160 mTorr
It has been clarified that when the value exceeds the above, problems such as the occurrence of undercut under the mask occur.

Table 2 shows the relationship between the etching rate of the polycrystalline silicon and SiO ₂ films and the substrate temperature. As the substrate temperature is lowered, the selectivity is improved, and the effect is particularly large at a substrate temperature of 0 ° C. or lower. In addition, the processed shape is improved because undercut is reduced.

[Table 2] Next, when the etching gas is switched from a 100% chlorine gas to a mixed gas of 80% chlorine and 20% helium, the boundary of whether or not destruction occurs due to the above-mentioned electric field shielding effect by helium ions is reduced to a pressure of 10 mTorr. It was confirmed that. Therefore, the addition of such a light element gas has the effect of expanding the pressure range in which processing can be performed without destruction.

Also, in the etching of polycrystalline silicon,
As in the resist embodiment described above, the size of the electrode strongly affects the uniformity of the etching rate. FIG. 15 is a characteristic diagram of the etching rate of Poly.Si in the wafer surface when the size of the electrode of the apparatus shown in FIG. 1 is variously changed. FIG. 15C shows an etching rate distribution in a direction perpendicular to the magnetic pole by an electrode having a radius larger than the wafer by 15 mm. Contrary to the case of the resist, the etching rate is smaller on the left side in the direction in which the electrons gather. The cause is unknown, but the slope is relatively small. On the other hand, (b) shows a comparative example in which electrodes having the same size as the wafer are used, and the uniformity is deteriorated. (A)
An electrode 15 mm larger than the same wafer as in (c) was used,
The results are obtained when the surface is covered with quartz glass having a thickness of 2 mm to protect the peripheral surface. Again, the uniformity is worse than in (c). This is because in the peripheral area, the applied high-frequency electric field is distributed to both the quartz plate and the plasma sheath,
This is because the electric field at the peripheral portion is smaller than the electric field at the wafer surface.

Further, the frequency of occurrence of gate destruction is (c)
It becomes higher in the order of (a) and (b). Therefore, it is necessary to use an electrode larger than the wafer in terms of uniformity and prevention of gate destruction. Also. The surrounding area is
It is desirable that the surface is made of a conductive material such as metal or carbon. However, when an insulator is unavoidably used to protect the electrodes and prevent contamination of the wafer, it is desirable to minimize the thickness to 1 mm or less.

Next, dry etching characteristics of various materials to be processed will be described.

[0074] As shown in Figure 1, using a dry etching apparatus of the present invention, in performing the processing of the gate electrode of the silicon MOSLSI device, a method of using the above-described chlorine is dominant, other 10 ^-2 Even if a gas containing bromine such as Br ₂ or HBr under a pressure of Torr or higher is used, etching excellent in processing shape and selectivity can be performed. Further, by adding a fluorine-containing gas such as SF _{6 to} these gases, deposition during etching is reduced and a good shape is obtained.

The dry etching method of the present invention is also effective for processing metal silicides such as WSi, MoSi, and TiSi used as low-resistance electrode materials. In this case, a gas containing chlorine or a gas containing bromine is also used. Or a mixed gas of a gas containing bromine and a gas containing fluorine can be used to obtain a good processing shape and selectivity.

For etching the silicon substrate, SiO _{2 was used.}
In order to use the film as a mask and secure selectivity to this SiO ₂ film, a gas containing chlorine or bromine is effective. For example, using a mixed gas of Cl ₂ : 90% and SiCl ₄ : 10%, the pressure is 10 mTorr to 50 mT.
orr range, 600 W RF power is applied and SiO
_A selectivity of 15 was obtained for ₂ . The processing shape depends on the substrate temperature and is vertical at 70 ° C, forward tapered at 50 ° C,
Above ° C, it became reverse tapered. Since it is difficult to embed a thin film in a reverse tapered shape, it is preferable to process at 70 ° C. or less.

Further, HBr is removed by etching the silicon substrate.
And Br ₂ can also be used as an etching gas, but since a deposit is easily generated, it is preferable to use a mixture with a gas containing fluorine such as SF ₆ .

Al-Si 1% -C used for wiring material
Undercutting is performed by using a gas of Cl ₂ and BCl ₃ in a mixing ratio of 3: 7 to 7: 3 for the processing of u (2%) and applying 200 W of RF power in a pressure range of 10 mTorr to 80 mTorr. No anisotropic etching was observed. The etching rates are Cl ₂ and BCl
_With a mixed gas of 3: 7: 3, 6000 Å / min was obtained. Also, Br ₂ and BBr ₃ etc.
Good anisotropic etching can be realized even by using a gas containing bromine. In addition, when the Al alloy is etched, heating the substrate to room temperature or higher can prevent the occurrence of etching residue.

CHF ₃ gas can be used for processing the SiO ₂ film, the phosphor-doped silica glass, and the boron-phosphorus-doped silica glass used as the insulating material. Table 3
Shows the relationship between the etching conditions when etching with such a material, the etching rate, and the inclination angle on the wall side.

[Table 3] The inclination angle on the wall side tends to be smaller as the pressure is higher and the substrate temperature is lower, and the inclination angle can be freely set by these parameters. Also, C
The addition of F ₄ tends to increase the inclination angle, and the addition of CH ₂ F ₂ tends to decrease the inclination angle. By adding these gases, the inclination angle of the side wall can be controlled.

The general formula Cl Hm Fn (m + n = 2l + 2)
Any gas can be used for processing the above-mentioned silica glass or the like.

As described above, when processing the resist and polycrystalline silicon by the method of the embodiment of the present invention, the uniformity of the etching rate is ensured by setting the etching gas pressure to a range of 10 mTorr or more. At the same time, it was revealed that abnormalities in the processed shape due to non-uniform plasma and damage to the gate oxide film can be reduced. Such a relationship between gas pressure and discharge uniformity is a general one that is relatively independent of gas type. That is, in addition to the above-described embodiment, Cl Hm
The same pressure range is applied to the relationship between various etching gases and a processing object such as etching of a SiO ₂ film using Fn (m + n = 2l + 2) gas and etching of single crystal silicon using a Br-based gas. By using, it is possible to realize uniform etching.

Further, by adding helium gas to oxygen and chlorine, uniformity and processed shape are improved, and gate breakdown is less likely to occur. This effect depends on the mobility of the light element ions, and the same effect can be obtained by adding hydrogen. Similar effects can be obtained by using a compound gas containing hydrogen in a molecule such as HCl or HBr.

In this embodiment, the processing of resist, polycrystalline silicon, single crystal silicon, metal silicide, silica glass, and Al alloy has been described. However, the present invention is not limited to these. Glass, Al
Alternatively, the present invention can be applied to various thin films such as Al alloys or metals such as copper and tungsten, or fine processing of the surface.

The embodiment of the dry etching method according to the present invention described above can be carried out not only using the dry etching apparatus shown in FIG. 1 but also using an embodiment apparatus shown in FIGS. is there.

FIG. 16 is a schematic structural view of an apparatus according to another embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this apparatus, the first
Electrode 111, a second electrode 112 opposed thereto, and a third electrode 113 which is grounded and serves also as a reaction vessel. High-frequency power is applied to both the first electrode 111 and the second electrode 112. Can be applied.

After the output signal of the high-frequency oscillator 114 is amplified by the amplifier 115, a high frequency is applied to the first electrode 111 via the impedance matching device 116.
For the second electrode 112, after the output signal of the oscillator 114 is amplified by the amplifier 118 via the phase adjuster 117,
High frequency is applied via the impedance matching device 119. Therefore, since the same oscillator 114 is used for both electrodes, the high frequency applied to both electrodes is maintained in a constant phase relationship set by the phase adjuster 117, so that a stable discharge occurs. Will be retained. Further, by optimally adjusting the phase relationship, the etching rate is maximized.

In this embodiment, the amplifiers 115 and 11
By adjusting 8, the self-bias voltage generated at both electrodes can be set to an arbitrary ratio. As a result, the drift of electrons on the upper electrode and the lower electrode can be balanced, and uniform etching can be performed.

Further, according to the structure of this embodiment, the electric field generated at both electrodes can be freely set according to the material to be etched and the required processing characteristics. Etching can be performed under excellent conditions.

Further, two oscillators 114 may be provided to apply electric fields having different frequencies to both electrodes. For example, by applying a high frequency to the second electrode 112 such that ions cannot follow the electrode and applying a low frequency voltage to the first electrode 111, the second electrode 112 can be prevented from being consumed. , Only the wafer 14 on the first electrode can be selectively etched.

FIG. 17 is a schematic structural view of an apparatus according to still another embodiment of the present invention. The same parts as those in FIG. 16 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, instead of directly applying a high frequency to the second electrode 112, a capacitor 121 and a variable inductor 122 connected to the ground are connected in series and grounded. The capacitor 121 has an effect of insulating the electrode 112 in a DC manner.
By adjusting 2, the phase of the high-frequency signal guided to the second electrode 112 can be adjusted, and the self-bias voltage generated on the surface of the second electrode 112 can be varied. As a result, similarly to the above-described embodiment, the electron drift on the upper electrode and the lower electrode can be balanced, and uniform etching can be performed. Further, by adjusting the phase of the high frequency applied to the second electrode 112, plasma can be collected at the center of the electrode, and the plasma density at the center can be increased. Also, the plasma can be dispersed around the electrodes.

It is preferable that the impedance of the inductor 122 and the capacitor 121 connected to the second electrode 112 match the impedance of the high-frequency oscillator 114 including the resistance of the wiring. Also, the third electrode 11
Although a ground wire is connected to 3, an induced voltage is partially generated due to the presence of an impedance and thus has a potential.

Although this embodiment has a narrower variable range of the self-bias electrode generated on the surface of the upper electrode 112 than the above-described apparatus, it has a feature that the structure is relatively simple and can be realized at low cost. Note that the inductor 122 may have a fixed value optimized in advance. Conversely, a high frequency voltage may be applied to the second electrode 112 side, and the capacitor 121 and the variable inductor 122 may be inserted between the first electrode and the ground.

[0095]

According to the first and fourth aspects of the present invention, the magnetic field generating magnetic circuit has a stepped shape with both end surfaces in the magnetization direction as walls.
Or, because it is constituted by a magnet block having a concave portion depressed in a tapered shape, the magnetic field lines formed between the inner surface and the outer surface of the wall surface can be closed near the apex of the wall portion, and a uniform magnetic field is obtained, Magnetron etching with high accuracy and little damage can be realized. According to each of the second and fifth aspects, the vertical magnetic field component can be suppressed to １ ／ or less of the horizontal magnetic field. According to the third aspect of the present invention, it is possible to improve the uniformity of the etching rate in the direction perpendicular to the line of magnetic force .

According to the sixth aspect of the invention, by setting the pressure of the etching gas to a pressure of 10 -2 Torr or more, the uniformity of the discharge can be improved, the anisotropy of the processed shape, and the uniformity of the etching rate Excellent fine processing is possible.
According to the seventh aspect of the present invention, the selectivity can be improved, and the processed shape can be made favorable by reducing the undercut. According to the invention of claim 8 , even if a lateral electric field is generated due to the bias of the electron density, these light ions move quickly, neutralize the charge, and can shield the electric field. Also, the uniformity of the etching rate is improved .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a dry etching apparatus of the present invention.

FIGS. 2A and 2B are a plan view and a cross-sectional view, respectively, of a permanent magnet used in an apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a magnetron etching apparatus as a comparative example.

FIG. 4 is a schematic perspective view of a permanent magnet used in the device of FIG.

FIGS. 5A and 5B are explanatory views for explaining problems of the conventional magnetron etching apparatus.

FIGS. 6A and 6B are explanatory views for explaining problems of different conventional magnetron etching apparatuses.

FIG. 7A is a schematic configuration diagram of an experimental device, and FIG. 7B is a characteristic diagram of an experimental result.

FIGS. 8A to 8C are explanatory diagrams for explaining resist etching according to an embodiment of the dry etching method of the present invention.

FIG. 9 is a characteristic diagram of resist etching according to an embodiment of the dry etching method of the present invention.

FIGS. 10A and 10B are explanatory diagrams for explaining gas pressure and plasma uniformity, respectively.

FIG. 11 is a characteristic diagram of resist etching according to an embodiment of the dry etching method of the present invention.

FIG. 12 is a characteristic diagram for explaining uniformity of an etching rate according to an embodiment of the dry etching method of the present invention.

FIGS. 13A and 13B are explanatory diagrams for explaining the effect of a light element gas in an embodiment of the dry etching method of the present invention.

FIGS. 14A and 14B are schematic cross-sectional views of an object to be processed used in an embodiment of the dry etching apparatus of the present invention.

FIG. 15 is a characteristic diagram of polycrystalline silicon etching according to an embodiment of the dry etching apparatus of the present invention.

FIG. 16 is a schematic configuration diagram showing another embodiment of the dry etching apparatus according to the present invention.

FIG. 17 is a schematic configuration diagram showing another embodiment of the dry etching apparatus according to the present invention.

[Explanation of symbols]

Reference Signs List 20 vacuum processing chamber 22, 24 parallel plate electrode 30 permanent magnet 32 stepped recess 36 rotation axis 40-46 wall 80, 101 wafer 81 resist 82 SOG 83 resist 91, 92 strong light emitting section 102 SiO ₂ film 103 polycrystalline silicon 111 First electrode 112 Second electrode 113 Third electrode 114 Oscillator 115, 118 Amplifier 116, 119 Impedance matcher 117 Phase adjuster 120 Insulator 121 Capacitor 122 Variable inductor
TE039101

Continuing from the front page (72) Inventor Haruo Okano 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Prefecture Within Toshiba Research Institute, Inc. Inside the Toshiba Tamagawa Plant (72) Inventor Shinji Kubota 2-3-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo Tokyo Electron Limited (72) Inventor Hirohiro Kumagai 2-3-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo East Inside Kyoto Electron Co., Ltd. (72) Inventor Junichi Arami 2-3-1, Nishi Shinjuku, Shinjuku-ku, Tokyo Tokyo Electron Co., Ltd. (56) References JP-A-2-174227 (JP, A) JP-A-2 JP-A-201923 (JP, A) JP-A-63-184333 (JP, A) JP-A-2-224239 (JP, A) JP-A-61-63021 (JP, A) JP-A-1-302726 (JP, A) JP-A-1-251735 (JP, A) JP-A-2-298024 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01 L 21/3065 C23F 4/00

Claims (8)

(57) [Claims] 1. A vacuum vessel, a pair of parallel electrodes including a first electrode on which an object to be processed placed in the vacuum vessel is placed, and a second electrode opposed to the first electrode, Means for introducing an etching gas into the magnet block, main magnet poles of opposite polarity are provided on both end faces of the magnet block, and the magnet block between the both end faces is formed with a stepped or tapered recess, and the recess is formed. A magnetic field generating magnetic circuit disposed opposite to the back surface of the second electrode, and means for driving the magnetic field generating magnetic circuit to rotate about a rotation axis
And a means for applying an electric field to at least one of the electrodes, and a dry etching apparatus for inducing a discharge between the parallel electrodes to etch the workpiece. 2. The method according to claim 1, wherein a vertical component of the magnetic field applied between the electrodes by the magnetic field generating magnetic circuit on the surface of the workpiece is suppressed to に or less of a horizontal component. Features a dry etching device. 3. The device according to claim 1, wherein the first electrode has an area larger than the object to be processed, and the portion on which the object to be processed is not placed is made of a conductive material or a thick material. A dry etching apparatus, which is covered with an insulator having a thickness of 1 mm or less. 4. An etching gas is introduced into a vacuum vessel, and a workpiece is placed on a first electrode provided in the vacuum vessel, and a second electrode facing the first electrode is provided. On the back side of the magnet block, both end faces of the magnet block have main magnetic poles of opposite polarities, and the magnet block between the both end faces is formed with a concave portion recessed in a stepped or tapered shape, and a concave portion behind the main magnetic pole is formed. the on face the main magnetic pole by placing the field generating magnetic circuit compensating magnetic poles of opposite polarity are provided, the magnetic field onset
A dry etching method for generating a substantially parallel magnetic field in the vicinity of the first electrode by rotating a raw magnetic circuit, and applying an electric field between the electrodes to induce a discharge to etch the workpiece. 5. The dry etching method according to claim 4 , wherein a vertical component of the magnetic field on the surface of the first electrode is suppressed to １ ／ or less of a horizontal component. 6. The dry etching method according to claim 4 , wherein the pressure of the etching gas is controlled to 10 −2 Torr or more. 7. The method according to claim 4 , wherein the temperature of the first electrode is controlled, and the object is fixed to the first electrode by using an electrostatic chuck to secure thermal contact. And controlling the temperature of the object to be processed. 8. The dry etching method according to claim 4 , wherein the etching gas is a mixed gas containing at least one of hydrogen and helium.