JP3172340B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, for example, in a process of manufacturing a semiconductor device, a plasma is generated in a processing chamber, and various kinds of plasma processing such as etching processing is performed on an object to be processed, for example, a semiconductor wafer in this plasma atmosphere. However, in recent years, with the progress of miniaturization of patterns to be applied to this type of workpiece, it has been required to perform plasma processing with higher accuracy in sub-half micron units.

To meet such demands, plasma sources for generating high-density plasma have been developed, and recently, helicon waves, ECR, TCP, HD, etc.
Attempts have been made to etch, for example, an oxide film of a semiconductor wafer with a high selectivity using high-density plasma such as P.

However, in plasmas produced by helicon waves or ECR, the selectivity to silicon is currently 10%.
It is low enough to meet the needs of the sub-half micron era. It is also reported that TCP can perform good etching at a high etching rate and a high selectivity by TCP, but the mechanism is still unknown and control is difficult. Furthermore, in the conventional plasma processing apparatus, since processing is performed in a high-density plasma region in order to obtain a high etching rate and a high selectivity, damage to a silicon substrate cannot be ignored.

[0005]

As described above,
With the conventional plasma processing apparatus, it has not been possible to carry out an etching process with a high etching rate and a high selectivity and with little damage to the silicon substrate, as required in the sub-half micron era. Therefore, the present invention has been made in view of the problems of the prior art,
It is an object of the present invention to provide a new and improved plasma processing apparatus having a high etching rate, a high selectivity, and less damage to a silicon substrate.

[0006]

According to a first aspect of the present invention, there is provided an airtight processing chamber adjustable to a predetermined reduced-pressure atmosphere, and a predetermined processing chamber in the processing chamber. Gas supply means for supplying the processing gas substantially uniformly;
And exhaust means for exhausting the processing chamber, the susceptor means for mounting and fixing the object to be processed in the processing chamber, the said object to be processed in the processing chamber is installed outside the upper part of said processing chamber in the inductively coupled plasma processing apparatus and a inductively coupled plasma generating means for generating an inductively coupled plasma above the processing surface, the inductive coupling
The plasma generation means is equipped with a flat, one-turn antenna.
For example, the susceptor means, said as the inductively coupled <br/> plasma generation means to be processed is to be located in the region of the high-density region beyond the inductively coupled plasma generated, wherein the inductive coupling <br/> plasma The distance from the lower surface of the generating means to the surface of the object to be processed is adjustable, and the gas supply means is provided for the object to be processed which is located in a region far from a high-density region of the inductively coupled plasma. An inductively coupled plasma processing apparatus is provided, in which the gas supply amount can be adjusted to increase so that the selective etching ratio is maintained at a predetermined value or more .

[0007]

According to a second aspect of the present invention, in the apparatus of the present invention, as the processing gas, an arbitrary set of elements selected from the group consisting of carbon (C), fluorine (F) and hydrogen (H). A silicon substrate or a silicon gas using one or more single or compound gases selected from the group consisting of a single gas or a compound gas and all elements constituting the group are introduced into the processing chamber; It is preferable to etch the silicon oxide film (SiO ₂ ) formed on the nitride film (Si ₃ N ₄ ).

According to inductively coupled plasma processing apparatus according to claim 1, induced with the target surface of the workpiece, placed on the outside upper portion of the processing chamber, the one-turn antenna in plane
Position of the coupled plasma generation means beyond the high-density plasma region
The substrate can be processed in a non-high-density region of, for example, inductively coupled plasma. Therefore, damage to the crystal structure due to ion bombardment, and substances such as hydrogen and carbon in the etching gas are injected into the substrate. Such a situation can be alleviated. In addition, by appropriately selecting the type of processing gas and the amount of exhaust gas to be supplied, the component for etching the underlying substrate is converted into another compound while the etching component reaches the processing surface, and this compound is subjected to inductive coupling. Because it is difficult to re-decompose because it is far from the plasma generation area,
High selectivity etching can be achieved. At that time,
Since the consumption of components for etching the film to be processed is suppressed, a high etching rate can be maintained.

[0010]

[0011] Furthermore, as described in claim 2, C the silicon oxide film, a process gas containing H and F, for example C ₄ F ₈ when performing etching by which the addition of H ₂ gas in the gas According to the apparatus of the present invention, F, which damages a silicon substrate or a silicon nitride film, reacts with H and is exhausted while reaching the processing surface from the high-density plasma region. Since it is much larger than F, an etching process with a high etching rate and a high selectivity can be achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which a plasma processing apparatus constructed according to the present invention is applied to an inductively coupled plasma etching apparatus will be described in detail. A schematic sectional view and a schematic plan view of the high-frequency inductively coupled plasma processing apparatus 1 of the present embodiment are shown in FIGS. 1 and 2, respectively. As shown in the figure, the substantially cylindrical processing chamber 2 is air-tightly formed of a conductive material such as stainless steel, and the upper surface of the processing chamber 2 has a central portion 3 formed of an insulating material such as quartz or alumina. The peripheral portion 4 is formed of the same conductive material as the processing chamber 2. In the present embodiment, a quartz plate having an outer diameter of about 230 mm and a thickness of about 10 mm is used as the central portion 3, but the size and material are not limited thereto.

On the outer upper surface of the insulating central portion 3 of the processing chamber 2, for example, a one-turn antenna means 5 formed of a thin copper plate having a thickness of 0.5 mm, for example, is provided. This antenna means 5 is connected to a high frequency power supply 7 via a matching circuit 6. At the time of processing, a high frequency is transmitted into the processing gas in the processing chamber 2 via the antenna means 5, and the processing gas is turned into plasma by the high frequency electromagnetic energy to process, for example, high density plasma of 10 ¹¹ cm ^-3 units. It is configured so that it can be generated in the room. The antenna means 5 only needs to be able to supply a predetermined high frequency into the processing chamber 2, and its material and shape, particularly the number of turns, is not limited to the above example.

A predetermined processing gas, for example, C, is supplied from a gas source (not shown) to the upper side of the processing chamber 2 and the center of the upper surface.
A gas supply unit 8 for supplying HF ₃ gas is provided. As shown in FIG. 2, the gas supply units 8 are radially arranged at equal intervals in the circumferential direction above the peripheral surface of the processing chamber 2.
One gas supply pipe 8A, 8B, 8C, and 8D and one gas supply pipe 8E arranged at the center of the upper surface of the processing chamber so that the processing gas can be uniformly supplied into the processing chamber 2. It is configured.

An exhaust pipe 9 is provided below the side surface of the processing chamber 2 so that the inside of the processing chamber 2 can be depressurized by exhaust means such as a vacuum pump (not shown). As shown in FIG. 2, the exhaust pipes 9 include four exhaust pipes 9 radially arranged at equal intervals in the circumferential direction below the peripheral surface of the processing chamber 2.
A, 9B, 9C, and 9D are configured so that the gas in the processing chamber 2 can be exhausted to the outside from each exhaust pipe without bias.

Further, a susceptor 10 for mounting an object to be processed, for example, a semiconductor wafer W, is provided in the processing chamber 2. The susceptor 10 is connected to a high-frequency power supply 12 via a blocking capacitor 11, so that a bias potential can be applied to the susceptor 10. Further, the susceptor 10 is provided with a refrigerant circulation path (not shown). The object W is cooled to a desired temperature through the susceptor 10 by the refrigerant supplied from the refrigerant supply pipe 13, and then cooled. 14.

The susceptor 10 can be moved up and down in the processing chamber 2 by an elevating device (not shown). The susceptor 10 is located between the processing surface of the object W and the lower surface of the antenna means 5 for generating plasma. Can be adjusted as desired. According to the present embodiment, the distance Z from the lower surface of the antenna means 5 to the processing surface of the object can be set to 50 mm or more and 200 mm or less, preferably more than 50 mm and less than 125 mm. As described above, the gist of the present invention is to perform the etching process with a high etching rate and a high selectivity by applying the distance dependence of the plasma characteristics found by the inventors of the present application from the antenna.
As described in detail below, the distance Z from the lower surface of the antenna to the processing surface of the object to be processed is optimally adjusted.

To understand such a principle, first, the density distribution of the electron density (Ne) and the ion current density (Ji) in the processing chamber 2 of the plasma processing apparatus 1 to which the present invention can be applied will be considered. . In this specification, the plasma generating means, that is, the antenna 5 side is referred to as upstream, and the susceptor 10 side on which the workpiece W is mounted is referred to as downstream.

The one-turn antenna 5 on the quartz plate 3 of the plasma processing apparatus 1 configured as described above is supplied from the high-frequency power source 7 via the matching circuit 6 to, for example, 13.56 MHz.
A high frequency of 12 KW is applied. CHF ₃ as processing gas
Electron density (Ne) and ion current density (J) when plasma is generated at a processing pressure of 20 mTorr using gas.
i) The downstream distribution from the antenna 5 was measured by a Langmuir probe. The result is shown in FIG. As shown, the electron density (Ne) is low near the quartz plate 3,
Once rises and decays. On the other hand, the ion current density (Ji) is constant up to 90 mm from the antenna 5 and then decreases. From the above results, high-density plasma is generated in the vicinity of the antenna 5, and the plasma has a sheet-like structure that rapidly attenuates downstream, that is, has a layered spatial structure substantially parallel to the processing surface. You can see that it is. Also, while the ion current density (Ji) decreases relatively slowly downstream, the electron density (Ne) sharply decreases near and downstream of the antenna, probably due to plasma loss to the walls of the processing chamber 2 and F This is considered to be due to the decrease in the number of electrons due to the generation of negative ions.

Next, C ₂ (5165) in CHF ₃ plasma
Angstroms) and F (6856 angstroms)
The dependence of the intensity ratio of the light emission on the distance from the antenna was measured. The experiment was performed with the distance (Z) from the antenna 5 to the counter electrode set to 300 mm and the pressure set to 20 mTorr. As a result, as shown in FIG. 4, the peak relative intensity of C ₂ with respect to the F atom increases as the distance from the antenna 5 increases, which is consistent with the result described above. This is F
Is considered to have occurred because it reacted with H present in the processing gas and was gradually exhausted as HF gas. Here, generally, the presence of C is determined by CO—O on the surface of the silicon oxide film.
Has the effect of cutting or weakening the bond of Si—O, and the presence of C is known to be important in etching a silicon oxide film. On the other hand, since silicon reacts more easily with fluorine ions than a silicon oxide film, reducing the amount of F present on the etched surface relative to C increases the selectivity of the silicon oxide film with respect to the underlying silicon. Important above. From the above results, it can be seen that the etching characteristics by the plasma greatly depend on the distance from the plasma generating means to the processing surface of the object to be processed.

Next, in order to investigate the dependence of the etching characteristics of the plasma on the distance from the antenna, the same plasma processing apparatus was used, and H ₂ was added to C ₄ F ₈ as a processing gas to obtain a gas from the antenna to the processing surface. The distance (Z) is Z =
50 mm (FIG. 5), Z = 75 mm (FIG. 6), Z = 100
mm (FIG. 7) and Z = 125 mm (FIG. 8), the etching rate and the selectivity of silicon (Si) and silicon oxide (SiO ₂ ) were measured. The experiment was performed at a pressure of 10 mTo
rr, Vdc = 200 V, and a thermal oxide film of a resist mask was used as a sample.

As a result, in the high-density plasma region near Z = 50 mm (FIG. 5), the etching rate is _{high for} both Si and SiO _2, but the selectivity is low, and as the amount of added H ₂ increases, the SiO 2 sharply increases. _2, the etching rate is reduced. However, on the downstream side, Z = 75 mm (FIG. 6) or Z =
100mm (FIG. 7), the etching rate of SiO ₂ is reduced gradually, and the etching rate of Si also monotonously decreases, and in yet additional amount of H ₂ is 30% or more Si
Only in this case, deposition occurs selectively and the selectivity becomes infinite. However, on the further downstream side, Z = 125 mm (FIG. 8), a decrease in the etching rate is observed. The reason for this is that as the distance from the plasma generation source decreases, the number of chemical species for etching SiO ₂ also decreases, so that it is not possible to achieve sufficient etching too downstream. Therefore, the distance between the processing surface and the antenna or the plasma generation region can be optimized.

From the above results, as in the plasma processing apparatus 1 constructed according to the present invention, the plasma generating means installed on the upper outside of the processing chamber 2, that is, the processing surface of the workpiece W from the lower surface of the antenna 5 Distance (Z) to 50mm
Not less than 200 mm, preferably more than 50 mm and 125 mm
By setting the value to less than the above, the processing surface of the object to be processed is kept away from the high-density region of plasma, so that etching with a high etching rate and a high selectivity and with little damage to the silicon substrate can be performed.

Next, the effect of an increase in the gas flow rate on the selection ratio will be described with reference to FIG. As shown
The magnitude of the gas flow rate greatly affects the etching rates of Si and SiO ₂ , that is, the selectivity. That is,
According to the apparatus of the present invention, the distance (Z) from the plasma generation means, that is, the lower surface of the antenna 5 to the processing surface of the object W to be processed.
Is large, F in the processing chamber 2 reacts with H to form HF.
If the formed HF must be removed from the processing chamber 2 promptly,
The HF is re-decomposed, and the etching of the underlying silicon by F is started again, and the selectivity decreases. Therefore,
When processing is performed by the apparatus of the present invention, it is necessary to increase the gas flow rate.
It is preferable to be M or more. It is unlikely that the gas flow rate is too large to cause a problem. The larger the flow rate, the higher the etching rate of the silicon oxide film and the lower the etching rate of the underlying silicon. Processing of the selection ratio can be performed.

In the above embodiment, the plasma processing apparatus constructed based on the present invention has been described in accordance with the inductively coupled plasma processing apparatus. However, the apparatus of the present invention is not limited to such a configuration. For example, as shown in FIG. It can be applied to a simple helicon wave plasma processing apparatus and the like. The illustrated helicon wave plasma processing apparatus 20 includes a gas supply unit 21 that supplies a processing gas G and a gas exhaust unit 2 that exhausts a gas after the processing.
Processing chamber 23 which has a predetermined vacuum degree
And a helicon wave plasma generating means 24 surrounding an application section 23A forming a part of the processing chamber 23. The helicon wave plasma generated by the helicon wave plasma generating means 24 allows the semiconductor wafer W held by the susceptor 25 to be removed. It is configured to perform plasma processing.

Further, the application section 23A of the processing chamber 23
It is formed of an insulating material that transmits electromagnetic waves such as quartz,
The main body 23C connected to the lower end opening of the application section 23A is formed of a conductive material such as stainless steel. The helicon wave plasma generating means 24 includes an antenna 24A provided on the outer peripheral surface of the application section 23A, and an electromagnetic coil 24B surrounding the application section 23A further outside the antenna 24A. The electromagnetic wave from the antenna 24A travels in parallel to the magnetic field formed by the above, and while this electromagnetic wave propagates in the plasma,
A helicon wave is generated under the action of the magnetic field, and a helicon wave plasma is generated while the helicon wave propagates in the plasma. In the figure, 26 is a blocking capacitor, and 27 is a high frequency power supply.

Therefore, when the semiconductor wafer W is physically etched using the CHF ₃ gas, first, the CHF ₃ gas is supplied from the gas supply unit 21 while the semiconductor wafer W is held by the susceptor 25. The gas pressure is adjusted to, for example, 10 mTorr. In this state, the antenna 24A
When a high frequency voltage is applied to the antenna 24A to generate an electromagnetic wave traveling in the axial direction in the processing chamber 23 from the antenna 24A, the CHF ₃ gas obtains activation energy from the electromagnetic wave to turn into plasma to generate plasma. In addition, a parallel magnetic field generated by the electromagnetic coil 24B acts on this electromagnetic wave to generate a low-frequency helicon wave from the electromagnetic wave to form high-density plasma.

At this time, according to the present invention, the antenna 2
The distance Z from the lower surface of 4A to the processing surface of the semiconductor wafer W mounted on the susceptor 25 is 50 mm or more and 200 m
m, preferably more than 50 and less than 125, the etching process can be performed at a place away from the high-density plasma region, and at the same etching rate and high selectivity by the same principle as described above. It is possible to perform an etching process with less damage to the silicon layer.

In the above embodiment, the silicon oxide film (SiO ₂ ) is explained by using an example in which H ₂ is added to CHF ₃ gas or C ₄ F ₈ gas. The present invention is not limited to this, and can be applied to, for example, a silicon nitride film (Si ₃ N ₄ ). Still further, the processing gas is a simple gas or a compound gas composed of a combination of arbitrary elements selected from the group consisting of carbon (C), fluorine (F), and hydrogen (H). It is possible to use one or more single gases or compound gases selected so that all the elements to be introduced into the processing chamber, for example, as a main gas component, a CF-based gas such as CF ₄ , CH
F ₃ , CH ₃ F ₂ , C ₂ F ₆ , C ₂ H ₂ F ₂ , C ₃ F ₈ , C ₄ F ₈ are used, and H ₂ , CO, CH ₄ , C ₂
H ₄ gas can be used.

Further, the present invention is not limited to the inductively coupled plasma processing apparatus or the helicon described in the above embodiment, but may be applied to other types of plasma processing apparatuses. Furthermore, the plasma processing apparatus configured based on the present invention is not limited to an etching apparatus, but can be applied to a CVD apparatus, an ashing apparatus, and the like.

[0031]

As described in the foregoing, according to the inductively coupled plasma processing apparatus constructed in accordance with the present invention, planar
Coupled plasma generator with one turn antenna
Since the plasma processing is performed in a downstream region distant from the high-density plasma region generated from the step, it is possible to perform the plasma processing with a high etching rate, a high selectivity, and less damage to the underlying layer. According to the device of the present invention ,
It is possible to increase the space from the inductively-coupled plasma generating means, which has a flat, one-turn antenna, to the processing surface. Since the object to be processed can be placed, there is no need to move the object to the inductively-coupled plasma generation region by raising and lowering the susceptor on which the object to be processed is mounted at a different position as in the related art. . Furthermore, according to the apparatus of the present invention, an apparatus for uniformly diffusing the processing gas, such as a shower head, can be installed in the space, so that it is possible to adopt an apparatus configuration for improving the etching accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of an inductively coupled plasma processing apparatus configured based on the present invention.

FIG. 2 is a plan view of the apparatus of FIG.

FIG. 3 is a graph showing distributions of electron density (Ne) and ion electron density (Ji) in a processing chamber in a downstream direction from an antenna.

FIG. 4 is a graph showing the dependence of the emission intensity ratio of C ₂ and F in CHF ₃ plasma on the distance from the antenna.

FIG. 5 shows the distance from the antenna Z = 50 mm showing the hydrogen concentration dependence of the etching rate and selectivity of Si and SiO ₂ .
It is a graph in the case of.

FIG. 6 shows the distance from the antenna Z = 75 mm showing the hydrogen concentration dependence of the etching rate and selectivity of Si and SiO ₂ .
It is a graph in the case of.

FIG. 7 shows a distance from an antenna Z = 100 m showing the hydrogen concentration dependence of Si and SiO ₂ etching rates and selectivity.
It is a graph in case of m.

FIG. 8 shows the dependence of the etching rate and the selectivity of Si and SiO ₂ on the hydrogen concentration.
It is a graph in case of m.

FIG. 9 is a graph showing a relationship between an etching rate of Si and SiO ₂ and a total gas flow rate.

FIG. 10 is a schematic cross-sectional view showing one embodiment of a helicon wave plasma processing apparatus configured based on the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 2 Processing chamber 3 Central part (quartz plate) 4 Peripheral part 5 Antenna 6 Matching circuit 7 High frequency power supply 8 Gas supply part 9 Exhaust part 10 Susceptor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-79025 (JP, A) JP-A-5-144779 (JP, A) JP-A-6-279984 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00

Claims (2)

(57) [Claims] 1. An airtight structure that can be adjusted to a predetermined reduced pressure atmosphere.
A predetermined processing gas is substantially introduced into the processing chamber formed and the processing chamber.
Gas supply means for uniformly supplying gas and exhausting the processing chamber
Exhaust means for mounting the object to be processed in the processing chamber;
Susceptor means for determining
Installed in the processing chamber,Sufferedprocessing
Above the planeInductive couplingFor generating plasmaInvitation
Conductive couplingPlasma generating means.Inductive couplingplasma
In the processing unit,The inductively coupled plasma generating means has a planar shape of one turn.
Equipped with an antenna,  The susceptor means is configured to transfer the object to be processed to theInductive couplingPlastic
The above-mentioned generation of the zuma generating meansInductive couplingHigh density of plasma
So that it is located in an area beyond the areaInductive couplingPlastic
From the lower surface of the gap generating means to the surface of the object to be processed
The distance is adjustable, and the gas supply means isInductive couplingHigh density area of plasma
Selection edge for the object located in a region beyond the
So that the gas ratio is maintained at a predetermined value or higher.
Adjustable to increase the amount is possibleInductive couplingPlasma processing equipment. 2. The processing gas is a simple gas or a compound gas composed of a combination of arbitrary elements selected from the group consisting of carbon (C), fluorine (F) and hydrogen (H). Is formed on a silicon (Si) substrate or a silicon nitride film (Si ₃ N ₄ ) using one or more single gases or compound gases selected so that all the elements constituting characterized by etching the silicon oxide film (SiO ₂₎ which is inductively coupled plasma processing apparatus according to claim 1.