JPH0436484A - plasma etching equipment - Google Patents

Abstract

PURPOSE:To generate stable high density plasma under low pressure, to easily control ion energy and to satisfactorily etch a wafer by generating a magnetic field perpendicular to the wafer and undergoing periodic changes in the intensity and converting a reactive gas into plasma. CONSTITUTION:A magnetic field perpendicular to a wafer 16 is applied with ringlike coils 11, 12 and the magnetic flux density of the magnetic field is periodically changed. By this change, an electric field is generated to a direction perpendicular to the magnetic field and electrons start circular motion. Electrons moving circularly and parallel to the wafer are liable to collide with molecules of a reactive gas and high density plasma can be generated even under low pressure. Negative ions are attracted to the wafer 16 by applying bias VB to the wafer 16 and plasma etching is carried out.

Description

[Detailed Description of the Invention] [Summary] Regarding a new structure of a plasma etching device, the purpose of this invention is to stably generate high-density plasma at a low degree of decompression and to make it easier to control ion energy. (1) This is a magnetic field plasma etching device in which an electromagnet is placed perpendicular to the wafer placed on an electrode and generates a magnetic field whose intensity changes at a constant period, and the magnetic flux density is uniform over at least the same area as the wafer. The method is characterized in that a negative bias is applied to the wafer and the reaction gas is turned into plasma by electrons that move circularly approximately perpendicular to the magnetic field.

(2) In a magnetic field parallel plate plasma etching device that performs reactive ion etching by applying high-frequency power, a magnetic field is generated that is perpendicular to the wafer placed on the lower electrode and whose intensity changes at regular intervals. It is characterized in that electromagnets are arranged so that the magnetic flux density is uniform between the upper electrode and the lower electrode at least in the same area as the wafer.

(3) A magnetic field plasma etching apparatus, in which an electromagnet that generates a magnetic field that is parallel to the wafer placed on the electrode and whose intensity changes at a constant period is arranged so that the magnetic flux density is at least at a predetermined area on the wafer. The area is uniform, and the wafer is characterized in that a negative bias is applied to the wafer so that the reactive gas is turned into plasma by electrons that move circularly approximately perpendicular to the magnetic field.

[Industrial application field]

The present invention relates to a novel structure of a plasma etching apparatus used in a method of manufacturing a semiconductor device.

Dry processing has become an extremely important technology for miniaturization and high integration of semiconductor devices, and plasma etching equipment has become widely used. However, as the diameter of wafers increases, uniform etching within the surface becomes difficult, and countermeasures are desired.

[Prior Art] For example, as an etching device in a dry process, microwaves are coupled to a magnetic field to generate electron cyclotron resonance (ECR).
A microwave plasma etching apparatus (ECR apparatus) is known in which etching is performed using excited plasma gas by causing resonance.

FIG. 5 shows a cross-sectional view of the main parts of a conventional microwave plasma etching apparatus. In the figure, symbol 1 is a microwave waveguide, 2 is a magnetron, 3 is a microwave transmission window, and 4 is a cylindrical coil ( electromagnet).

5 is an etching chamber, 6 is a wafer (substrate to be etched), 7 is an electrode, and 8 is a reaction gas introduction tube.

9 is an exhaust port.

As shown in the figure, microwave plasma etching equipment (EC
R device) is a microwave (
For example, a microwave with a frequency of 2.45 GHz) is introduced into the microwave transmission window 3 through the microwave waveguide 1, and the microwave is transmitted from the microwave transmission window to the etching chamber 5, and the microwave and the coil 4 generate the microwave. This device causes electrons to rotate due to resonance with a magnetic field, and the electrons collide with a reactive gas to turn the reactive gas into plasma, and the wafer 6 is etched by the plasma gas. Further, the magnetic field (indicated by a dotted line) generated by the coil 4 has a magnetic field gradient that becomes weaker in the direction in which the wafer is placed, and the plasma gas is accelerated in one direction of the wafer.

Further, the microwave transmission window 3 is a window that allows only microwaves to pass through while vacuum sealing the inside of the etching chamber 5.
This window is made of alumina, etc.

Thus, for example, freon (CF) is introduced and turned into plasma to generate F9 ions and neutral active species (radical species), and silicon is etched by these excited gases.

[Problem to be solved by the invention] By the way, the ECR device as described above has a degree of decompression of 10-
The pressure is set to be as low as Torr or less in order to reduce the loading effect (differences in etching rate and shape depending on pattern density). Since microwaves are introduced into the etching chamber 5 during the etching process, the microwave transmission window 3 is gradually contaminated with reactive gas, resulting in poor transmittance and a decrease in plasma density.

In addition, the magnetic field generated by the coil (shown by the dotted line) is parallel to the wafer, which tends to make the plasma gas non-uniform in the plane, and furthermore, the rotation of electrons occurs in the plane perpendicular to the magnetic field. Therefore, there is a drawback that electrons easily collide with the wafer surface and cause damage.

Other devices include magnetic field reactive ion etching, which performs etching at low pressure to reduce loading effects.
; RIE) device is being considered, and this is a normal RIE device.
The purpose is to make the plasma density equivalent to that of a normal RIE device by lowering the pressure to a lower pressure than the device (degree of vacuum: about 10-'Torr), but the effect of increasing plasma density has not yet been sufficiently achieved.

Further, similar to the ECR apparatus, the magnetic field RIE apparatus also has the disadvantage that large diameter wafers are likely to be etched non-uniformly within the plane, and the wafer may be damaged. Furthermore, RIE equipment uses high-frequency discharge and applies a bias to draw negative ions to the wafer side, but if the voltage is low, matching becomes difficult, causing abnormal discharge and reducing ion energy. There is a problem of poor controllability.

The present invention proposes a plasma etching apparatus which aims to reduce these problems, stably generate high-density plasma at a low degree of vacuum, and facilitate control of ion energy.

[Means to solve the problem]

The problem is a magnetic field plasma etching device,
An electromagnet that generates a magnetic field whose intensity changes at regular intervals is arranged perpendicular to the wafer placed on the electrode, and the magnetic flux density is uniform at least over the same area as the wafer, and the wafer is negatively biased. A plasma etching device is configured such that a reactive gas is turned into plasma by electrons that move circularly perpendicularly to the magnetic field, or a magnetic field parallel plate that performs reactive ion etching by applying high frequency power. In a type plasma etching apparatus, an electromagnet that generates a magnetic field that is perpendicular to the wafer placed on the lower electrode and whose intensity changes at a constant period is placed, and the magnetic flux density is at least as high as the wafer between the upper electrode and the lower electrode. A plasma etching system configured so that the same area is uniform, or a magnetic field plasma etching system that generates a magnetic field that is parallel to the wafer placed on the electrode and whose intensity changes at regular intervals. A negative bias is applied to the wafer, and the reactive gas is turned into a plasma by the electrons moving in a circular motion almost perpendicular to the magnetic field. The problem is solved by a plasma etching apparatus configured to etch.

[For production]

That is, the present invention is configured to generate a magnetic field whose intensity (magnetic flux density) changes at regular intervals, and the reaction gas is turned into plasma by the change in the magnetic field.

In this way, stable high-density plasma can be obtained at low pressure,
Moreover, since microwaves are not introduced, the plasma density does not decrease (it can be configured as an etching device superior to ECR devices).Also, stable high-density plasma can be obtained at low pressure, and no high-frequency power source is used. for,
The ion energy can be easily controlled, and an etching apparatus superior to a magnetic field RIE apparatus can be constructed.

〔Example] Examples will be described in detail below with reference to the drawings.

Figure 1 shows a plasma etching device according to the present invention. & (
I) shows a cross-sectional view of the main parts, and symbols 1) and 12 in the figure are shown.
1 is a ring-shaped coil, 15 is an etching chamber, 1
6 is a wafer, 17 is an electrode, 18 is a reaction gas introduction tube, 1
9 is an exhaust port IV, and Vl is a bias. This ring-shaped coil 1). 12 causes a magnetic field perpendicular to the wafer 16 (
(shown by the dotted line), the magnetic flux density is made uniform over the same area as the wafer, and this magnetic field (B) changes the magnetic flux density at a constant period (ω) (B(t) = Bo s
in (1) t).

Then, as shown in Figure 2, due to the magnetic field B, an electric field E is generated in a direction perpendicular to the magnetic field due to Faraday's electromagnetic induction, and the electron e (indicated by .) accelerates into a nearly circular shape. Begin circular motion (betatron motion). Electrons moving in a circular motion parallel to the wafer easily collide with gas molecules, making it possible to generate high-density plasma even at low pressure. Moreover, since the circular motion of the electrons is in a direction parallel to the wafer, the probability of the electrons colliding with the wafer surface is low (and therefore, it is difficult to cause damage).

In this way, this plasma etching apparatus has a change in strength (magnetic flux density) due to the coil (electromagnet) (B(t) = Bo
This method is characterized in that plasma is generated by the wafer (sinωt), and negative ions are attracted to the wafer by applying a bias (2) to perform plasma etching.

Using a cylindrical etching chamber (quartz bell jar) with a diameter of 250 mm, S etching was performed on a wafer with a diameter of 8 inches.
In the example in which the i0g film was etched using trifluoromethane (CHF, ) as the reaction gas, the bias V++
Etching can be performed at high speed at 100 V and a reduced pressure of 0.005 Torr. Further, when a W Si 2 (tungsten silicide)/polycrystalline silicon multilayer film is etched using hydrogen bromide (HBr) as a reaction gas, the etching can be performed satisfactorily at a bias Vl of 20 V and a power of 0°005 Torr.

The plasma etching apparatus shown in FIG. 1 above can be considered to be an improved type of ECR apparatus, but next, an improved type of magnetic field RIE apparatus will be explained.

FIG. 3 shows a plasma etching apparatus (II) according to the present invention.
), in which symbols 21 and 22 are ring-shaped coils, 23 is an upper electrode, 24 is a lower electrode,
25 is an etching chamber, 26 is a wafer, 28 is a reaction gas introduction pipe, 29 is an exhaust port, and S is a high frequency power source. As in FIG. 1, a perpendicular magnetic field (indicated by a dotted line) is applied to the wafer 26 by ring-shaped coils 21 and 22, and the magnetic flux density is uniform over the same area as the wafer, and this magnetic field The intensity (magnetic flux density) is changed (B (t) = B, sin ωt) at a constant period (ω).

Then, due to the magnetic field B, an electric field E is generated in a direction perpendicular to the magnetic field due to Faraday's electromagnetic induction, and the electrons accelerate and move in a circular motion (betatron motion). Electrons moving in a circular motion parallel to the wafer tend to collide with gas molecules, generating high-density plasma even at low pressure. Moreover, since the circular motion of the electrons is parallel to the wafer, the probability of the electrons colliding with the wafer surface is low, making it difficult to cause damage, and the same effect as the plasma etching apparatus shown in FIG. 1 can be obtained.

This plasma etching device generates plasma using a high-frequency power source and changes the magnetic flux density (B) using a coil.
(t) = Bo sin ωt ), the plasma is multiplied, and the plasma gas is used to perform etching.

To explain one example, magnetic flux density B(t)=B.

Bo=80 Gauss at sin π/T-t, period T
-1 second condition, frequency 13.56M on the wafer side
Connect the H2 high frequency power supply to cool the wafer and maintain it at 2°C. Then, in order to etch a 5in2 film on a wafer with a diameter of 8 inches, CHF3 gas was flowed at a flow rate of 30 seconds, and the degree of decompression was 0.02To2.
When etching is performed using rr and electric power IKW, uniform etching can be achieved.

Next, FIG. 4 shows a sectional view of the main parts of the plasma etching apparatus 1 (I[[) according to the present invention, in which symbol 3L 32 is a ring-shaped coil, 35 is an etching chamber, and 36 is a wafer. , 37 is an electrode, 38 is a reaction gas introduction pipe, and 39 is an exhaust port +Vl is a bias.

This device applies a horizontal magnetic field (indicated by dotted lines) to the wafer 36 using ring-shaped coils 31 and 32, and the magnetic field (B) changes the magnetic flux density (B (
t) = Bo sin ωt). The electrons move due to the electric field E perpendicular to the magnetic field B, and the movement of the electrons becomes close to circular motion under certain conditions.

Moreover, this circular motion of the electrons makes it easier for the electrons to collide with gas molecules. On the other hand, ions also move in the opposite direction to the electrons, but if the period of the electric field is in the high frequency range, the ions cannot follow the movement of the electrons, and a part separated from the electrons forms near the wafer, creating a potential difference. Due to the potential difference and bias V generated in a plane perpendicular to the wafer, the plasma gas is accelerated in one direction of the wafer and etching is performed.

In this plasma etching apparatus, the ion energy can be controlled independently regardless of the bias VB.
This device has the advantage of easily making the plasma gas uniform, and this device has the advantage of making the plasma gas uniform.
It can be said to be an improved version of the ECR device similar to the IE device.

For example, it is possible to etch a Sin film on a wafer with a diameter of 8 inches φ using CHF3 gas with a time modulation of magnetic flux density of 13.56 MH2, an intensity of 80 Gauss, a bias Vm of 200 V, and a degree of vacuum of 0.005 Torr. can.

〔Effect of the invention〕

As is clear from the above explanation, all of the plasma etching apparatuses according to the present invention are characterized by generating or multiplying plasma by changing the intensity (magnetic flux density). For example, it can generate high-density plasma at low pressure and can uniformly etch even large-diameter wafers, greatly contributing to higher quality and higher reliability of semiconductor devices such as ICs and LSIs.

Furthermore, there is less etching damage to the wafer, which was a problem with conventional plasma etching equipment.
This also has the effect of significantly improving controllability of ion energy.

[Brief explanation of drawings]

Figure 1 shows a plasma etching apparatus (1) according to the present invention.
FIG. 2 is a diagram showing the movement of electrons. FIG. 3 is a plasma etching apparatus (n) according to the present invention.
FIG. 4 is a cross-sectional view of the main parts of the plasma etching apparatus (I[
FIG. 5 is a sectional view of the main part of a conventional plasma etching apparatus. In the figure, 1), 12.21.22.3L 32 is a ring-shaped coil, 15, 25.35 is an etching chamber, 16, 2
6.36 is the wafer 17, 37 is the electrode, 18, 28.38 is the reaction gas introduction tube, 19, 29.39 is the exhaust port, 23 is the upper electrode, 24 is the lower electrode, ① is the bias, S is the high frequency power supply It shows. iF琐≦萌1埠1>17U, Z・nx−,chishi7・1moxibustionf(r)−平tp粁向Gri Fig. 1’tJ, 4–motion t, tv Fig. 21II Fig. Figure 1 Mei 7 Q Ta β 7 # Las' Maenchi 37-5 LtJ
)'Envious Darkness Figure 5

Claims (3)

[Claims] (1) A magnetic field plasma etching device, in which an electromagnet that generates a magnetic field that is perpendicular to the wafer placed on an electrode and whose intensity changes at a constant cycle is arranged, and the magnetic flux density is at least the same area as the wafer. is uniform, and is configured such that a negative bias is applied to the wafer and a reactive gas is turned into plasma by electrons that move circularly substantially perpendicular to the magnetic field. (2) In magnetic field parallel plate plasma etching equipment that performs reactive ion etching by applying high-frequency power, a magnetic field is generated that is perpendicular to the wafer placed on the lower electrode and whose intensity changes at regular intervals. 1. A plasma etching apparatus characterized in that electromagnets are arranged so that the magnetic flux density is uniform between an upper electrode and a lower electrode at least over an area equal to the wafer. (3) A magnetic field plasma etching apparatus, in which an electromagnet that generates a magnetic field that is parallel to the wafer placed on the electrode and whose intensity changes at a constant period is arranged, and the magnetic flux density is at least at a predetermined area on the wafer. A plasma etching apparatus having a uniform area and configured such that a negative bias is applied to the wafer and a reactive gas is turned into plasma by electrons moving circularly almost perpendicular to the magnetic field. .