JPH05279877A - Etching device by plasma - Google Patents

Abstract

PURPOSE:To suppress the deposition of gaseous molecules on the surface subjected to etching and to increase anisotropic etching by providing the electron emitting part in a chamber with a reflector and regulating the electron current value flown therethrough to the minimum. CONSTITUTION:Electrons (e) emitted from an electron emitting hole 75a of the electron emitting part 7 provided in an etching chamber 1 are reflected on an electron reflector 8 set in the chamber 1 to increase their running distance in the chamber. Therefore, the probability of their collision with the molecules of a gas introduced from a gas introducing part 6 for etching increases. Thus, etching capable of sufficiently generating ions even at a gaseous density lower than that in the case where outer electrons are not introduced, i.e., in an environment of a higher vacuum is smoothly executed. Furthermore, at the time of regulating the electron current density flown between the electron emitting part 7 and reflector 8 to the minimum, the diffusion of the electron beams from the electron emitting part 7 is suppressed, and good anisotropic etching can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching apparatus.

[0002]

2. Description of the Related Art A plasma etching apparatus is shown in FIG.
As shown in FIG. 3, an RF power source (13.
56 MHz) 94, a high frequency voltage is applied, and thereby the etching gas introduced from the gas introducing portion 96 between the electrodes is turned into plasma, and the ions collide with the object to be etched 95 with energy corresponding to the self-bias of the plasma P. Then, the surface of the object to be etched is etched. In this case, the ionization efficiency of the neutral gas for etching is usually 10 ^−4.
It is a degree.

[0003]

As described above, in the conventional apparatus, since the ionization efficiency of the neutral gas is about 10 ⁻⁴ , the gas supply amount must be increased in order to increase the etching rate. However, increasing the gas supply is contrary to the recent tendency to perform etching in a high vacuum environment to enhance anisotropic etching.

Further, there is a problem that when the gas supply amount is increased, the phenomenon that gas molecules are deposited on the object to be etched. Here, let us first take up the problem of deposition of gas molecules on the object to be etched. Number of gas molecules F ₀ flowing into the object to be etched under the conditions of pressure P and temperature T
Is defined as follows.

F ₀ = n · c / 4 c: average molecular velocity c = (8 kT / πm) ^1/2 (where k is Stefan-Boltzmann constant) n: gas density n = 9.6 × 10 ¹⁸ × P / T (P: torr,
T: ° K) For example, when the pressure is 100 mmtorr and the temperature is 300 ° K in argon molecules, the number of molecules flowing into the object to be etched is as follows.

F₀= 3 × 10¹⁹n / cm²sec On the other hand, the normal plasma density is 10^Tenn / cm³Regarded as
ing. Gas molecule density at 100 mmtorr is 3 × 1
0¹⁵n / cm³Therefore, the ionization efficiency is about 10^-FourThought
Be done. Therefore, the inflow amount F of ions into the object to be etched is
_iIs as follows.

F _i = n _i · v / 4 n _i : ion density v: speed at which ions reach the object to be etched by the bias voltage. For example, assuming that the ions reach the object to be etched by the bias voltage of 500 V, F _i = 1 × 10 ¹⁶ n / cm ² sec.

That is, for the deposition of gas molecules, 2 to 3 digits
It means that the etching is performed by an ion flow that is an order of magnitude lower. For this reason, it is necessary to carry out etching under a high vacuum which reduces the supply amount of etching gas. Next, how the degree of vacuum contributes to aligning the directionality of ions will be described. Now, the probability that the parallel molecular flow does not change direction without colliding with the residual gas molecules while traveling the distance X can be defined as follows.

P (X) = exp (-X / λ) λ: Mean free path Assuming that the molecular diameter is 3.7Å and the temperature is 20 ° C., λ = 0.005 / P (cm) Now, etching from plasma is performed. The sheath distance to the object is 1
Assuming about cm, the change in the probability of not changing the directionality of the molecule with respect to pressure is as follows.

[0010] From this, as the degree of vacuum is improved, the ions extracted from the plasma enter the object to be etched without changing the direction.

Although etching is usually performed in the range of 10 to 100 mmtorr, most of the ions collide with gas molecules and enter the object to be etched. Therefore, the etching anisotropy is deteriorated. Therefore, the present invention provides a plasma etching apparatus that enables smooth etching under high vacuum, can suppress deposition of gas molecules on the surface of an object to be etched, and can enhance anisotropic etching. It is an issue.

[0012]

Means for Solving the Problems The present inventor has conducted extensive research to solve the above problems, and ionization of an etching gas is not sufficient only by high frequency discharge under a high vacuum, but ionization from the outside Of the electrons, a reflection electrode for electrons is provided in the etching chamber, and the supplied electrons are reflected by the electrons to increase the traveling distance of the electrons, thereby improving the ionization efficiency. It was found that the plasma density required for etching can be obtained even in a low density state, that is, in a high vacuum state.

In order to increase the plasma density uniformly in each part of the plasma region, it is necessary that electrons are evenly distributed in the plasma region. To this end, a plurality of electron emission parts are provided in the etching chamber. Attached, equalizing the electron current value flowing through the reflective electrode facing each electron emitting portion,
It has been found that the electron reflection voltage applied to the reflective electrode may be controlled so that the electron current value flowing through the chamber wall is made as small as possible while being made as small as possible.

Based on the above findings, the present invention applies a high frequency voltage to an etching gas to convert the gas into plasma,
A plurality of electron emission units are attached to an etching chamber for etching an object to be etched under the plasma so that electrons can be injected into the chamber, and the electron emission units are provided at positions facing each electron emission unit in the chamber. Reflecting electrodes for reflecting the incoming electrons are provided, a reflecting power source for applying an electron reflecting voltage is connected to each of the reflecting electrodes, and means for detecting an electron current value flowing in each of the reflecting electrodes, the etching. A means for detecting an electron current value flowing in a chamber wall and a current value detected by each of the detecting means are read to make the electron current value flowing in each of the reflective electrodes equal to the minimum (to be as small as possible), and the etching chamber. Voltage adjustment that adjusts the voltage applied by each of the reflection power supplies so that the electron current value flowing through the wall is minimized (as small as possible). There is provided an etching apparatus using plasma, characterized in that a means.

In the plasma etching apparatus, the difference between the electron current value from each electron emitting portion and the electron current value flowing through the reflecting electrode when the reflecting electrode facing the electron emitting portion is grounded. Means may be provided to adjust the power output at each electron emitter to minimize it. The reason is that when the electron current value flowing in the reflective electrode is very small compared to the electron current value from the electron emission part when the reflective electrode is grounded, the electron beam diverges so much that the electrons collide with the etching chamber wall. Since it is more likely that the electron beam is not reflected by the potential of the reflective electrode in such a situation,
This is because it is desirable to suppress the divergence of the electron beam in order to avoid this.

The number of the electron emitting portions is, for example, 3 or more in order to increase the traveling distance of the electrons in the plasma region in the etching chamber and make the distribution uniform to improve the positional uniformity of the plasma density. It is conceivable to attach them to the chamber at equal center angular intervals. When the etching gas in the chamber is a reactive gas and does not want to enter the electron emission portion, a small-diameter electron having conductance capable of preventing the electron emission portion from flowing into the electron emission portion. It is conceivable to connect to the chamber by a passage.

Various types of the electron emitting portion can be adopted, and examples thereof include those that generate microwave plasma to extract electrons. In general, it is desirable that the chamber be at a ground potential, and in this case, the potential of the electron emitting portion is negative with respect to the potential of the plasma in the chamber. Here, a simple consideration will be made to evaluate the improvement of ionization efficiency by external electrons. 1. The plasma density can be defined as follows.

N _i = τ _i · n _o · σ (Ee) · v _e · n _e n _o : Gas density n _e : Electron density v _e : Electron velocity τ _i : Ion confinement time τ _i = 2.63 · (T _i / T _e ) ^1/2 · V / S · v _i where T _i is the ion temperature, T _e is the electron temperature, and v _i is the average ion velocity.

Now, in the case of a plasma generating chamber having a radius B and a length L, V / S is as follows. V / S = 0.5 · B (B / L + 1) σ (Ee): Ionization cross section at electron energy E Generally, the maximum value is obtained when the energy is 100 eV, and the values are as follows.

Σ (Ee) = 3 × 10 ^-16 cm ² 2. The product of the electron density n _e and the electron velocity v _e can be estimated from the electron discharge current value. Now, assume that an electron current of 1 A is obtained. At this time, the electron current density can be defined as follows. J _e = e · v _e · n _e / 4 (e: charge) The electron current density drawn through the 0.2 cm gap at an applied voltage of 100 V is obtained from the Langmuir equation as follows.

J _e = 60 mA / cm ² Here, when the relational expression of the electron current density is modified, v _e · n _e = 4 · J _e / e Therefore, v _e · n _e = 1.5 × 10 ¹⁸ / Cm ² sec 3. Next, the ion confinement time is evaluated.

The plasma generation chamber has a radius of 15 cm and a height of 5 cm. Also, at 500 ° K, the average velocity of the ions has the following values. v _i = 5 × 10 ⁴ cm / sec Therefore, the ion confinement time has the following value. However,
It was assumed that T _i = 1 eV and T _e = 10 eV.

Τ _i = 5 × 10 ^-4 sec 4. Finally, the ion density becomes as follows, and the ionization efficiency can be obtained. n _i: 0.23 · n _o In other words, the ionization efficiency will exceed 20%. 5. This teaches that lower gas densities are required to obtain the same ion density.

[0024] In the conventional method, the ionization efficiency because it was of the order of _{^{10 -4, n i = 10 -4}} · n o next, in order to obtain a plasma density of ^{10 10 n / cm 2 10 15} n / cm ³ Gas density was needed. This corresponds to 30 mmtorr. on the other hand,
According to the present invention, even if n _i = 10 ⁻¹ · n _o , a gas density of 10 ¹¹ n / cm ³ is sufficient to obtain the same plasma density. This corresponds to 0.003 mmtorr.

From this, it is understood that the apparatus of the present invention enables etching under high vacuum due to high ionization efficiency. 6. Further, the deposition of gas molecules on the object to be etched is evaluated. The number of molecules F ₀ flowing into the object to be etched at 30 mmtorr has the following values.

F _o = 9 × 10 ¹⁸ n / cm ² sec On the other hand, the number of inflowing molecules at 0.003 mmtorr F ₀
Is reduced by 4 digits and has the following value. F _o = 9 × 10 ¹⁴ n / cm ² sec As previously calculated, assuming that ions reach the object to be etched at a bias voltage of 500 V, the ion inflow amount F _i to the object to be etched is F _{i Since i} = 1 × 10 ¹⁶ n / cm ² sec, when comparing the two, F _i increases by about one digit. In the conventional device, the ratio of the ion inflow number F _i and the molecule inflow number F _o is γ = F _i / F _o = 3 × 10 ⁻³ , whereas in the device of the present invention, γ = 10. ..

This shows that the ion inflow for etching is dominant as compared with the deposition of unnecessary gas. Therefore, it is mainly etched by the ions in the same direction that are extracted from the plasma sheath,
Etching with good anisotropy is possible. Next, the point of making the electron distribution uniform in the plasma region by adjusting the voltage applied to the reflective electrode will be further described.

First, when electrons are extracted from the electron emitting portion facing the reflecting electrode without applying a voltage to the reflecting electrode, a current flows in the reflecting electrode facing the reflecting electrode. The value of the electronic current can be known from this current value. When the voltage of the reflective electrode is gradually lowered in the negative direction, the electrons are reflected and the current value decreases. When the absolute value of the voltage of the reflective electrode falls below the absolute value of the electron extraction voltage of the electron emitting portion, the electrons are completely reflected and the current value becomes zero. As a matter of course, electrons collide with the other reflective electrodes, and the current value of these electrodes increases.
Therefore, the voltage value of the reflective electrode is adjusted so that the value of the current flowing through all the electrodes is equal to the minimum (preferably zero). It is also conceivable that the electrons pass through between the reflective electrodes and reach the wall of the chamber. Therefore, the voltage value of the reflective electrode is adjusted so that the current value flowing in the chamber is also minimized. From the above, the distribution of electrons in the plasma region in the chamber can be made uniform, and thus the positional uniformity of plasma density can be improved.

It is not impossible to manually adjust these voltages, but the operation becomes complicated when the number of parameters increases. Therefore, it is desirable to provide the voltage adjusting means as described above.

[0030]

According to the etching apparatus of the present invention, in plasma etching of the object to be etched in the etching chamber, electrons are extracted from the electron emitting portion attached to the etching chamber and are made incident into the chamber.
The electrons are reflected by the electron reflecting electrode installed in the chamber, increasing the travel distance in the chamber. Therefore, the probability of collision with the gas molecules for etching increases, and the ionization efficiency of the gas increases accordingly. Therefore, a gas density lower than that when external electrons are not introduced, that is, ions that contribute to etching are sufficiently generated under a higher vacuum environment.

Further, the electron current value flowing through each reflection electrode and the electron current value flowing through the etching chamber wall are detected by the current detecting means, and the detected values are read by the voltage adjusting means. On the basis of the read value, the voltage adjusting means causes the reflection power source connected to each reflection electrode so that the current value at each reflection electrode is equal and minimized, and further, the current value at the chamber wall is minimized. Adjust the voltage. As a result, the distribution and movement of electrons in the plasma region in the chamber are made uniform, and the plasma density in each part of the plasma region is made uniform.

As described above, the object to be etched is smoothly etched with good anisotropy. In such an etching apparatus using plasma, the difference between the electron current value from each electron emitting portion and the electron current value flowing through the reflecting electrode when the reflecting electrode facing the electron emitting portion is grounded is minimized. When the means for adjusting the power output of each electron emitting portion is provided in the above, by adjusting the power output of the electron emitting portion by this means, the divergence of the electron beam from the electron emitting portion is suppressed and the reflection of incident electrons by the reflecting electrode is suppressed. Will be more certain.

When each electron emitting portion is connected to the chamber by a small-diameter electron passage having a conductance capable of preventing the etching gas from flowing into the electron emitting portion, the chamber etching gas enters the electron emitting portion. do not do.

[0034]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an etching apparatus using plasma according to an embodiment, more specifically, a vertical cross-sectional view taken along a plane parallel to the center line of the cylinder of the cylindrical etching chamber 1, and FIG. It is a cross-sectional view cut by a plane perpendicular to the center line.

This apparatus has a cylindrical etching chamber 1
The chamber 1 is equipped with parallel plate electrodes 2, 3
Are placed one above the other. The upper electrode 2 is a ground electrode and is grounded via the chamber 1. Lower electrode 3
Is a high-frequency electrode which also serves as a support holder for the substrate A to be etched.
3.56 Hz)) 4 is connected.

Further, the chamber 1 is connected to an exhaust device 5 for evacuating the inside thereof, and a pressure detector PT for detecting the introducing portion 6 of the etching gas and the pressure inside the chamber 1, and further the chamber 1 Electronic current I flowing on the wall
A detector 12 for detecting _W is connected. This introduction part 6
A gas flow rate control unit M _O is connected to. Further, three electron emitting portions 7 are fixed to the outer surface of the peripheral side wall 1W of the chamber 1 at intervals of 120 degrees.

Each electron emitting portion 7 has the same structure,
This example is of a type that can generate microwave plasma by utilizing electron cyclotron resonance (ECR), and is continuously connected to the outer surface of the chamber peripheral side wall 1W, more specifically, the peripheral side wall body in an insulated state via an insulating member 76. It is attached to the outer surface of the electrode member 11. More specifically, the antenna 72 passed through the ferromagnetic member 71 is surrounded by a permanent magnet 73 to form a plasma generation chamber 74, and a member 75 having an electron emission hole 75a is provided at the front opening of the plasma generation chamber 74. There is. The electron emission hole 75a is provided on the side wall of the chamber around the electrode member 11
Of the electron entrance hole (electron extraction hole) 11a.

The antenna 72 is formed of stainless steel having good corrosion resistance, and a microwave power source (2.54 GHz) 77 is connected to the antenna 72. Electron emission part 7
Is connected to the minus side of the electron extraction power source 78, and the plus side of the power source is connected to the electrode member 11 of the chamber 1. Thus, a positive voltage can be applied to the electron entrance hole (electron extraction hole) 11a. Between each power source 78 and the electron emitting portion 7, the electron current value i emitted from the electron emitting portion is
A detector 78a for detecting _i (i ₁ , i ₂ or i ₃ ) is connected.

The highest ionization cross-sectional area is that electron energy is about 100 eV, so that electrons are extracted from a gap of about 0.2 cm (gap between members 75 and 11; approximately the thickness of member 76). .. Further, in the plasma generation chamber 74, a gas introduction part 74 for a gas serving as a plasma source is provided.
1 is provided, to which a gas flow rate control unit M _i is connected. In this example, the gas introduced from here is a gas different from the etching gas introduced into the chamber 1, for example, an argon gas.

The etching gas in the chamber 1 is the member 7
5 does not enter the electron emitting portion 7 due to the conductance of the portion from the electron emitting hole 75a to the electron incident hole 11a.
Here, the influence of another gas (for example, argon gas) introduced into the electron emission portion 7 on etching will be examined. For example, if the holes 75a and 11a are both 0.4 cm in diameter and electrons are extracted by the two electrodes 75 and 11, how effective the differential pumping is is to first describe one orifice. The conductance has the following values.

Con = 1.3 liter / sec The orifices are connected in series (length 0.2 c
Therefore, the total conductance is as follows. C = 0.65 liter / sec When the plasma in the electron emitting portion 7 is generated at the pressure P ₁ , the vacuum degree of the chamber 1 is P ₂ , and the exhaust capacity is S, the following relational expression holds.

Q = C · (P ₁ −P ₂ ) = P ₂ · S (Q: flow rate) Now, it is assumed that each parameter is given as follows. If P ₁ = 10 ⁻³ torr S = 100 liters / sec, P ₂ has the following value.

P ₂ = 7 × 10 ^-6 torr Since this degree of vacuum is sufficiently lower than the degree of vacuum caused by the etching gas in the chamber 1, it is considered that there is no effect on etching. Inside the chamber 1, a total of three electron-reflecting electrodes 8 are arranged on the outer peripheral side of the electrodes 2 and 3 and facing the electron-emitting portions 7 at 120-degree intervals. Each electrode 8 is arranged on the circumference centered on the cylindrical center line of the chamber 1 and has a concave reflection surface 81 that is substantially parallel to the inner surface of the chamber peripheral side wall. The size of the reflective electrode 8 is limited to the extent that electrons are surely incident into the chamber 1. Each electrode 8 can be connected to a voltage-adjustable reflection power source 82 capable of applying a higher potential (negative voltage) than the energy of electrons entering the chamber 1. Each electrode 8 can also be grounded. This switching is performed by the switching device 82a. Furthermore, the electron current value I _i (I ₁ , I ₁ ,
A detector 80 for detecting I ₂ or I ₃ ) is connected.

The entire operation of the apparatus described above is controlled by the controller 10 shown in the control block circuit of FIG. The controller 10 is mainly composed of a microcomputer and is configured to input information from the outside and output instructions to the outside through an interface circuit (not shown).

From the pressure in the chamber 1 detected by the pressure detector PT, the electron current value I _W in the chamber wall detected by the current value detector 12, and the electron emission parts 7 detected by the current value detectors 78a. Electron current value i _i (i ₁ , i ₂ or i ₃ ), and electron current value I _i (I ₁ , I ₂ or I ₃ ) in each electron reflecting electrode 8 detected by each current value detector 80
Are input to the controller 10.

[0046] The on-off control of the high frequency power source 4, the on-off control of the exhaust system 5, the flow rate control of the flow rate control unit M _O for introducing an etching gas into the chamber 1, a microwave power in the electron-emitting portions 7 Output control of 77, voltage setting of electron extraction power source 78 in each electron emitting portion 7, flow rate setting of gas flow rate control unit M _i in each electron emitting portion 7, each reflecting electrode 8 is connected to the reflecting power source 82 or grounded. The control of the switching device 82a and the voltage control of each reflection power source 82 are performed based on an instruction from the controller 10.

According to the above-described etching apparatus, for example, as the object to be etched, there is prepared a substrate A on which an etching pattern is drawn on the surface with an appropriate mask material and which is etched by plasma of a reactive gas such as chlorine gas or fluorine gas. To be done. Initially, the inside of the chamber 1 is evacuated to a predetermined vacuum degree by the exhaust device 5, and then the gas introduction part 6
Reactive gas for etching into the chamber 1 from a gas source (not shown) on the basis of the flow rate control of the flow rate control unit M _O is introduced in, the chamber 1 is set to a predetermined etch vacuum.

On the other hand, the plasma generation chamber 7 of each electron emission section 7
4, a flow rate control unit M _i in the gas introduction unit 741 introduces a predetermined amount of argon gas, for example. In this state, each reflective electrode 8 is grounded. Next, in each electron emission unit 7, the microwave power supply 77 supplies microwaves to the antenna 72, and the voltage of the electron extraction power supply 78 is set to a predetermined value, whereby a positive voltage is applied to the electron extraction hole 11a. To do. Then, plasma is generated in the electron emission portion 7 by the microwave discharge from the antenna 72, and electrons are incident from the plasma toward the counter reflection electrode 8 in the chamber 1. Here, in each current value detector 80, the electron current value I _i (
I ₁ , I ₂ or I ₃ ) is detected, and the electron current value i _i (i ₁ , i ₂ or i ₃ ) emitted from each electron emitting portion 7 is detected by each current value detector 78a. .

This current value I_iAnd i_iAnd ε = i_i-I
_iIs calculated in the controller 10, and this is a predetermined minimum
It is determined whether it is a value. Some are not the minimum value
And the minimum value under the instruction of the controller 10
The output of the microwave power supply 77 related to the state is adjusted.
And adjusted toward the minimum value. Next, each reflective electrode 8
Connect to the corresponding reflected power supply 82,
Under the direction of the controller 10, electrons flowing through each electrode 8
Current value I_i(I₁, I ₂, I₃) Are equal and can
Adjust so that it is smaller (zero is desirable), then
And the electron current value I flowing through the chamber wall_WIs as small as possible
Adjust to make it smaller.

As a result, the distribution of electrons in the plasma region of the chamber 1 is made uniform, and the positional uniformity of the plasma density can be improved. When the etching preparation is completed in this way, the substrate A to be etched is set on the high frequency electrode 3 from the closed substrate loading / unloading chamber (not shown) connected to the chamber 1 by the substrate transfer device (not shown), and the high frequency power source 4 is turned on. The etching gas is turned into plasma, and etching is started under the plasma.

During this etching, electrons e are made to enter the chamber 1 from each electron emitting portion 7. The electron e thus injected travels in the chamber 1, but a negative voltage is applied from the reflection power source 82 to the reflection electrode 8 arranged at the opposite position, so that the energy of the electron e is held by the electrode 8 By being set to a higher potential, the electrons e collide with the reflective electrode 8 and are reflected, and the repetitive motion is repeated in the chamber 1 as shown by the line a in FIG.

As described above, by supplying electrons into the chamber 1 from the outside, the ionization efficiency of the plasma P region in the chamber can be enhanced. Therefore, even when the neutral gas density in the plasma region is low, the same ion density as in the case where the gas density is high can be obtained. Therefore, etching can be performed under a high vacuum as compared with the case where there is no electron supply from the outside, the deposition of gas molecules on the substrate A is reduced, and the directionality of ions can be aligned. Further, as described above, the uniform distribution of electrons in the plasma region improves the positional uniformity of the plasma density. These enable etching with good anisotropy.

Next, the operation of the controller 10 will be described with reference to the flowchart of FIG. 4 showing its outline. When the program starts, the chamber 1 is evacuated to a predetermined degree of vacuum by the exhaust device 5 in step S1. Then
In step S2, the introduction of the etching gas from the gas introduction unit 6 into the chamber 1 is started, and the introduction of, for example, argon gas from the gas introduction unit 741 in each electron emission unit 7 into the plasma generation chamber 74 is started.

In step S3, the flow rate control unit M _O in the gas introduction unit 6 is adjusted, and the flow rate control unit M _i in the gas introduction unit 741 of each electron emission unit 7 sets the gas flow rate into the plasma generation chamber 74 and inflows. Let In step S4, the pressure detector PT measures the degree of vacuum P _T in the chamber 1, and in step S5, it is determined whether or not the pressure in the chamber has reached a predetermined etching degree of vacuum P _T set.
If “NO”, the process returns to step S3, and the flow rate control unit M
Readjust _O. If "YES", step S6
At step S7, the microwave power source 77 in each electron emitting portion 7 is turned on, and in step S7, the electron extraction power source 7 in each electron emitting portion 7 is turned on.
The voltage of 8 is set to a predetermined value.

Next, in step S8, the current I _i in the reflecting electrode 8 facing each electron emitting portion 7 is measured, and in step S8
At 9, the electron extraction current i _i from each electron emission portion 7 is measured. In step S10, the difference ε = i _i −I _i is obtained, and in step S11 it is determined whether or not each difference ε is a predetermined minimum value. If either is "NO", step S12
Then, the microwave power supply output related to the state other than the minimum value is adjusted, and the process returns to step S8. All "YE
In the case of "S", the process proceeds to step S13, the respective reflection electrodes 8 are connected to the reflection power source 82 and turned on, and the power source voltage is increased in the electron reflection direction in step S14. In step S15, the current I _i in each reflective electrode 8 is measured, and in step S1
In step 6, it is determined whether or not these are the predetermined minimum values, and if any of them is "NO", the process returns to step S14 to readjust the reflected power supply voltage related to the state that is not the minimum value.

If all are "YES", step S1
In step 7, the respective reflection electrode currents are compared with each other, and in step S18, it is determined whether or not they are all equal and close to zero. "N
If it is "O", the voltage of each reflection power source is readjusted to approach zero in step S19. If "YES", the current I _W in the chamber wall is measured in step S20, and it is determined in step S21 whether or not it is substantially zero. If "NO", the voltage of each reflection power supply is determined in step S22. Readjust and bring it closer to zero. If "YES", the step S
At 23, the etching preparation is completed.

Next, in step S24, the substrate A is placed on the chamber high-frequency electrode 3, and in step S25, the substrate A is etched.

[0058]

As described above, according to the present invention,
It is possible to provide a plasma etching apparatus that enables smooth etching under high vacuum, can suppress deposition of gas molecules on the surface of an object to be etched, and can enhance anisotropic etching. Further, in such an etching apparatus, the difference between the electron current value from each electron emitting portion in the apparatus and the electron current value flowing through the reflecting electrode when the reflecting electrode facing the electron emitting portion is grounded is minimized. When a means for adjusting the power supply output in each electron emitting portion is provided, by adjusting the power supply output of the electron emitting portion by this means, divergence of the electron beam from the electron emitting portion is suppressed, and incident electrons by the reflecting electrode are suppressed. More reliable reflection,
As a result, the plasma density is increased and good anisotropic etching can be performed, and unnecessary electron collision with the chamber wall and the like is prevented.

When each electron emitting portion is connected to the chamber by a small-diameter electron passage having a conductance capable of preventing the etching gas from flowing into the electron emitting portion,
As a result, it is possible to prevent an etching gas, such as a reactive gas, which is not desired to enter into the electron emission portion.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an embodiment of the present invention.

2 is a schematic cross-sectional view of the embodiment of FIG.

FIG. 3 is a schematic block diagram of a circuit that controls the operation of the device.

FIG. 4 is a flowchart showing an outline of the operation of the controller shown in FIG.

FIG. 5 is a sectional view of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 etching chamber 1W peripheral wall of chamber 1 11 electrode member 11a electron entrance hole (electron extraction hole) of member 11 detector of electron current in chamber wall 2 ground electrode 3 high frequency electrode 4 high frequency power supply 5 exhaust device 6 introduction of etching gas part M _O flow controller RT chamber 1 in the pressure detector P plasma 7 electron-emitting portion 71 ferromagnetic member 72 antenna 73 permanent magnets 74 plasma generation chamber 741 the gas inlet portion M _i flow control unit 75 electron-emitting member 75a electron emission holes 77 microwave power supply 78 electron extraction power supply 78a electron extraction current detector 8 reflection electrode 80 electron current detector in electrode 8 81 concave surface of electrode 8 reflection power supply 82a switching device e electron 10 controller

Claims (6)

[Claims] 1. A plurality of electrons are introduced into an etching chamber in which a high-frequency voltage is applied to an etching gas to turn the gas into plasma, and an object to be etched is etched under the plasma. A reflection electrode for reflecting incident electrons is provided at a position facing each electron emission portion in the chamber, and a reflection power source for applying an electron reflection voltage is connected to each reflection electrode. In addition, a means for detecting an electron current value flowing in each of the reflection electrodes, a means for detecting an electron current value flowing in the etching chamber wall, and a current value detected by each of the detecting means are read, The respective reflected power supply voltages are set so that the electron current value flowing through the electrodes is equalized to the minimum, and the electron current value flowing through the etching chamber wall is also minimized. An etching apparatus using plasma, which is provided with voltage adjusting means for adjusting. 2. The plasma etching apparatus according to claim 1, wherein an electron current value from each electron emission portion and an electron current flowing through the reflection electrode when the reflection electrode facing the electron emission portion is grounded. A plasma etching apparatus comprising means for adjusting the power supply output in each electron emitting portion so as to minimize the difference with the value. 3. The plasma etching apparatus according to claim 1, wherein the electron emitting portion is provided in an odd number of 3 or more, and these electron emitting portions are attached to the chamber at equal center angular intervals. 4. The electron-emitting portion is connected to the chamber by a small-diameter electron passage having a conductance capable of preventing the etching gas in the chamber from flowing into the electron-emitting portion. Plasma etching equipment. 5. The plasma etching apparatus according to any one of claims 1 to 4, wherein each of the electron emitting portions generates microwave plasma to extract electrons. 6. The plasma etching apparatus according to claim 1, wherein the chamber has a ground potential, and the potential of each of the electron emitting portions is negative with respect to the plasma potential in the chamber.