JPH07316823A - Plasma cvd method and device therefor - Google Patents

Abstract

PURPOSE:To flatten the surface of a substrate to be treated by cooling the substrate in a plasma CVD chamber below the dew point of the deposition species by a substrate stage cooling means and irradiating the substrate with helicon wave plasma. CONSTITUTION:A substrate stage 2 is provided coaxially with a bell jar 5 in a CVD chamber 15. A substrate 1 to be treated is placed on the stage 2 and cooled by a cooling means 3. The deposition species is supplied on the substrate 1 from a second gas showering 14, liquefied and condensed. A gas supplied to the bell jar 5 from a first gas showering 13 is converted into the reaction species by the helicon wave plasma formed by the helicon wave antenna 6 and solenoid coil assembly 9, and the reaction species is injected into the substrate 1. The deposition species and reaction species are alternately injected to apply plasma CVD. The liquefaction and densification are alternately and continuously applied, and the substrate surface is flattened. A dense and good- quality film is formed in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD apparatus and a plasma CVD method, and more specifically, it can form a flat surface on a substrate to be processed having a step or a concave portion and is excellent in film quality. The present invention relates to a plasma CVD apparatus and a plasma CVD method that are useful when forming an insulating film such as a silicon-based film.

[0002]

2. Description of the Related Art As semiconductor devices such as LSIs have been highly integrated and their design rules have been miniaturized from the sub-half micron level to the quarter micron level, the pattern width of internal wiring has been reduced. . On the other hand, in order to keep the wiring resistance at a low level and prevent delay of signal propagation and various migrations, it is necessary to secure the cross-sectional area of the wiring while adopting a wiring material of low resistance such as Cu. That is, since the height of the wiring is required to some extent, the aspect ratio of the wiring tends to increase. When such fine wiring is used as a multilayer wiring, a process of forming a flattened interlayer insulating film on a step or a recess formed by the lower layer wiring to secure a flat surface and forming an upper layer wiring thereon is repeated. Will be required.

In addition, trench isolation for avoiding mutual interference between elements formed on the same semiconductor chip, trench capacitors of DRAM, etc., formed on a semiconductor substrate with a large aspect ratio, are made of insulating material. The method of flatly filling with a dielectric material is indispensable for the manufacturing process of highly integrated semiconductor devices. in this way,
The so-called global flattening technique of filling the steps, recesses and grooves formed on the substrate to be processed with an insulating film having excellent film quality and flattening the surface thereof is one of the key processes of the highly integrated semiconductor device. .

Conventionally, various methods for forming a planarized interlayer insulating film have been developed. For example, a monthly review of these forming methods can be found in Monthly Semiconductor World magazine (published by Press Journal) November 1989, page 81. ing. Of these, TEOS (Tetraethyl or
thosilicate, or Tetraeth
A silicon oxide-based insulating film formed by a CVD method using an organic silane gas such as oxysilane) and O ₂ or O ₃ as a source gas can absorb a step difference in a base during film formation to obtain a good step coverage. , Is attracting attention as a so-called self-flow process. Above all, since the reaction temperature can be lowered to about 400 ° C. or lower by plasma CVD, it can be used as an interlayer insulating film on Al-based metal wiring.

However, in response to the recent demand for higher aspect ratio and perfect flatness of the device structure, TEOS-
The CVD method alone is not satisfactory either, and further flattening by secondary processing after film formation is required. For example, U.S. Pat. No. 4,954,459 discloses that a convex portion of a deposited insulating film is partially removed by etching, and CMP (Chemi) is used.
cal-Mechanical Polishing)
A flattening method in which the above is combined is disclosed. According to this method, almost complete global flattening is possible, but problems such as contamination and an increase in the number of steps due to deterioration of the particle level due to abrasive particles remain.

In view of the above situation, a method for forming a planarizing oxide film has recently been proposed based on a new idea called liquid phase CVD method or low temperature CVD method. This is because the depositing species in the vapor phase are condensed and liquefied on the cooled substrate to be flowed into the groove, and the condensed phase is oxidized to a solid phase. The groove with a high aspect ratio is buried flatly.

In this liquid phase CVD method, an organosilane compound is condensed on a substrate to be processed cooled to about -30 ° C.,
A method has been reported in which this is reacted with O atoms to form an oxide, which fills a groove with a high aspect ratio (Extended.
d Abstracts of 19th Conf
Rence on Solid State Devi
ces and Materials, Tokyo, 1
987, p451). According to this method, when the condensation rate of the organosilane compound is faster than the oxidation rate, bubbles are generated in the deposited film to form a porous film, or the oxidation reaction is incomplete and alkyl groups remain in the deposited film. There is a problem such as doing.

As another liquid phase CVD method, there is a method of condensing a precursor using SiH ₄ as a source gas on a substrate to be processed which has been cooled to a low temperature of −110 ° C. and oxidizing the condensed precursor to fill a trench. It is reported in Proceedings p633 of the 38th Joint Lecture on Applied Physics (1991 Spring Annual Meeting), Lecture No. 29p-V-11. This method
Since the film growth is carried out at an extremely low temperature, a large amount of H is taken into the deposited film, so that problems remain in terms of film quality and reliability.

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to reliably fill a step, a recess or a groove having a large aspect ratio formed on a substrate to be processed with an insulating film having a good film quality to obtain a flat surface. A plasma CVD apparatus and a plasma CVD method capable of achieving the above are provided.

Another object of the present invention is a plasma capable of obtaining a dense and highly reliable insulating film having a small amount of residual organic substances and hydrogen in the formed planarizing insulating film and no bubbles in the film. A CVD apparatus and a plasma CVD method are provided.

Still another object of the present invention is to form a flattened insulating film having good film quality by only one CVD process without requiring secondary processing such as etching back or polishing after forming an insulating film. A plasma CVD apparatus and a plasma CVD method are provided. Problems other than the above of the present invention,
This will be made clear by the description of the present specification and the accompanying drawings.

[0012]

Means for Solving the Problems Plasma CVD of the present invention
An apparatus is proposed in order to solve the above-mentioned problems, and a substrate stage cooling means capable of cooling a substrate to be processed in a plasma CVD chamber below a dew point of a deposition species and a helicon connected to this plasma CVD chamber. And a wave plasma generation source.

The helicon wave plasma generation source is, for example, as disclosed in US Pat. No. 4,990,229, a helicon wave antenna for high-frequency excitation of an inductively coupled antenna wound around a dielectric bell jar as a plasma generation chamber, The main component is a solenoid coil that generates a magnetic field in the bell jar axial direction. The helicon wave antenna includes, for example, a type in which a pair of upper ring-shaped antenna and lower ring-shaped antenna are driven in mutually opposite phases, but is not particularly limited to this antenna shape. The plasma CVD apparatus of the present invention is characterized by further having an intermittent means for intermittently supplying the solenoid coil current.

The plasma CVD method of the present invention uses the above-described plasma CVD apparatus to liquefy and condense the deposition species on the substrate to be processed that has been cooled to below the dew point of the deposition species, and to generate a helicon wave plasma source on the substrate to be processed. The plasma CVD is performed by irradiating the reactive species generated in (1).

The plasma CVD method of the present invention uses the plasma CVD apparatus described above to liquefy and condense the deposition species on the substrate to be processed that has been cooled below the dew point of the deposition species, and a helicon wave plasma on the substrate to be processed. Plasma CVD is performed by alternately performing the step of irradiating the reactive species generated in the generation source.

[0016]

The point of the present invention is that a helicon wave plasma source is adopted as the plasma source of the low temperature plasma CVD apparatus. As is well known, the helicon wave plasma generation source generates a helicon wave (Heusler wave) by the helicon wave antenna and the solenoid coil as described above, and generates a high density plasma of 10 ¹¹ / cm ³ to 10 ¹³ / cm ^3. It is possible to 10 ⁹ / cm ³ of a parallel plate type plasma device which is a conventional general plasma generation source
The plasma density is 2 to 4 orders of magnitude higher than the plasma density of the table. The high flux density ion flow based on this high density plasma propagates along the magnetic field created by the solenoid coil, and supplies high density reactive species with ion bombardment onto the substrate to be processed. For this reason, the organic components and hydrogen contained in the deposited species condensed on the substrate to be processed are decomposed and removed with an order of magnitude higher efficiency than the conventional low temperature CVD, and the quality and the densification of the formed insulating film are improved. It will be achieved.

Further, since the plasma CVD apparatus of the present invention has an intermittent means for intermittently supplying the solenoid coil current of the helicon wave plasma generation source, the helicon wave mode and ICP (Inductively) in the plasma CVD chamber.
It is possible to appropriately switch and use the plasma processing in the Coupled Plasma mode. That is, when the solenoid coil is energized, the helicon wave is propagated in the plasma in the helicon wave mode to increase the ion current density, and when the solenoid coil is turned off, the ICP mode discharge is performed to reduce the ion current density to some extent. It is possible to operate freely.

As is well known, the ICP generation mechanism supplies a high frequency wave to a multi-turn antenna wound around the outer circumference of a plasma chamber made of a dielectric material, and rotates electrons according to an alternating magnetic field formed in the multi-turn antenna. This causes the electrons and gas molecules to collide with high probability. In the plasma CVD apparatus of the present invention, the function of this multi-turn antenna is exhibited by the helicon wave antenna. In ICP, the radical generation rate itself is generally higher than that of helicon wave plasma.

As is clear from the above description, the helicon wave plasma generation source can be regarded as an ICP generation source with a solenoid coil added. That is, according to the plasma CVD apparatus of claim 2 of the present invention, when the solenoid coil is energized, the treatment with the helicon wave plasma having a high ion flux density is performed, and when the solenoid coil is turned off, the treatment with the radical-based ICP is performed. Is applied. Moreover, by controlling the duty ratio of the current application to the solenoid coil, plasma CVD utilizing the characteristics of both modes can be achieved.

Therefore, by utilizing the function of the plasma CVD apparatus of the present invention, helicon wave plasma mode processing is performed when film quality improvement and densification are required, and ICP mode is performed when liquefaction condensation is desired. Can be treated with. By intermittently energizing the solenoid coil, it is possible to alternately and continuously perform the liquefaction and densification treatments. That is, the original flattening effect of the liquid phase CVD method and the dense and excellent film quality can be achieved at the same time.

In the plasma CVD method of the present invention, this C
It is possible to completely flatten the insulating film deposited only by the VD process. In other words, there is no need for post-processing such as the prior art of depositing a film thicker than the required film thickness and then flattening it by etching back or CMP.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

Example 1 First, a configuration example of a helicon wave plasma CVD apparatus used in this example will be described with reference to the schematic sectional view shown in FIG.

The helicon wave plasma source comprises a helicon wave antenna 6, which circulates around a bell jar 5 made of quartz or alumina, a helicon wave plasma power source 7, a matching network 8 and a solenoid coil assembly 9. Of these, solenoid coil assembly 9
Consists of an inner peripheral coil that contributes to the propagation of the helicon wave and an outer peripheral coil that contributes to the transport of the generated plasma. DC power is supplied to each coil from the solenoid coil power supply 10 via the intermittent connection / disconnection means 11. CVD chamber 15
A substrate stage 2 on which the substrate 1 to be processed is placed is arranged coaxially with the bell jar 5, and an RF bias is supplied to the substrate stage 2 from a substrate bias power supply 4. Further, the substrate stage 2 is equipped with a substrate stage cooling means 3 including a cooling pipe for supplying a refrigerant such as ethanol or liquid nitrogen from a chiller (not shown). The substrate stage may be equipped with a heater for temperature control, a temperature detecting means, a substrate chuck, a backside heat transfer gas supplying means, and the like.

Further, the bell jar 5 in the CVD chamber 15
Immediately below, there are a first gas shower ring 13 that mainly supplies a reactive species gas into the bell jar 5, and a second gas shower ring 14 that mainly supplies a deposition species gas toward the target substrate 1. It is arranged directly above the substrate stage 2. Reference numeral 12 is a multi-pole magnet arranged on the outer periphery of the CVD chamber 15, which controls the plasma flow of each mode by converging the divergent magnetic field in the vicinity of the substrate stage 2. In the figure, details of the device such as the gate valve and the vacuum pump are omitted. According to this plasma CVD apparatus, liquid phase CV using high density plasma by helicon wave
It is possible to apply D.

Next, the plasma CVD method of the present invention will be described. This embodiment uses the plasma CVD apparatus described above and
MS (Tetramethyl Silane) and O ₂
This is an example in which a trench is filled by forming a flattening insulating film made of SiO _{2 by using} as a source gas. This will be described with reference to FIGS. 1 and 3A to 3B.

As a substrate to be processed, as shown in FIG. 3A, a semiconductor substrate 21 made of Si or the like has a thickness of 0.25 μm to 2.0 μm.
A trench 22 having various opening diameters was used. The depth of the trench 22 is 1 μm, for example.

The substrate 1 to be processed was set on the substrate stage 2, and as an example, SiO ₂ was deposited under the following conditions. The state after the deposition is shown in FIG. From the second gas shower ring 14 TMS 100 sccm From the first gas shower ring 13 O ₂ 100 sccm Gas pressure 0.5 Pa Helicon wave plasma power supply power 2500 W (13.
56MHz) Substrate bias power supply power 50W (2MH
z) Substrate temperature −30 ° C. In this embodiment, the solenoid coil power is always on.
Then, the process was performed in the helicon wave plasma mode.

In the plasma CVD process, the TMS introduced from the second gas shower ring 14 remains in a molecular state or partially condenses to form a precursor such as a dimer or trimer to form a deposition species. Then, it is liquefied and condensed on the cooled substrate 1 to be processed and quickly flows into the trench 22. On the other hand, O ₂ introduced from the first gas shower ring 13 is dissociated in the bell jar 5 to become active species such as O ⁺ , and the plasma C is generated by the magnetic field formed by the solenoid coil assembly 9.
It is propagated to the VD chamber 15. The active species also contributes to the applied substrate bias to give an ion bombardment to the substrate to be processed, oxidize and remove the methyl groups, and the film densification progresses at the same time. As shown in FIG. 3, the trench 22 has a flattening insulating film 23 made of SiO _{2 with} good film quality.
Can be embedded evenly.

According to this embodiment, since the oxidation rate exceeds the condensation liquefaction rate of TMS, bubbles are not generated in the flattening insulating film 23 and organic substances such as methyl groups do not remain, so that reliability is improved. It is possible to form high trench capacitors and trench isolation.

Embodiment 2 This embodiment is an example of the construction of an apparatus using an intermittent interrupting means for the solenoid coil current of a helicon wave plasma generating source, which will be described with reference to the schematic sectional view shown in FIG.

Since the present apparatus is basically the same as the apparatus shown in FIG. 1, only the characteristic portions will be described, and the overlapping components will be denoted by the same reference numerals and the description thereof will be omitted. The characteristic part of the plasma CVD apparatus of this embodiment is that the installation location of the gas shower ring is changed. That is, the first gas shower ring 13 is installed in the upper part of the bell jar 5, and the second gas shower ring 14 is installed in the opening of the bell jar 5 facing the CVD chamber 15. Along with this, the installation location of the matching network 8 is also changed from the top of the bell jar 5 to the side.

This embodiment is an example in which a flattened interlayer insulating film is formed on an Al-based metal wiring by using monosilane (SiH ₄ ) and O ₂ as source gases by using the above plasma CVD apparatus. 4 (a)-(b) will be described.

As a substrate to be processed, a plurality of A having a width of, for example, 0.35 μm are formed on the lower insulating film 24 as shown in FIG.
The one in which the 1-system metal wiring 25 is formed is used. The space between the Al-based metal wirings 25 is, for example, 0.35 μm to 2.
It is distributed between 0 μm. The height of the Al-based metal wiring 25 is, for example, 0.5 μm, and an adhesion layer or a barrier metal layer may be formed in the lower layer of the Al-based metal wiring 25, and an antireflection layer or the like may be formed in the upper layer. Illustration of these layers is omitted.

The substrate 1 to be processed is placed on the substrate stage 2.
And, for example, SiO under the following conditions ₂The deposition of
It was The state after the deposition is shown in FIG. From the second gas shower ring 14 SiH_Four 3 sccm H₂ 97 sccm O from the first gas shower ring 13₂ 100 sccm gas pressure 0.5 Pa helicon wave plasma power supply power 2500 W (13.
56MHz) Substrate bias power supply power 50W (2MH
z) Substrate temperature −110 ° C. In this embodiment, the intermittent interrupting means 1 such as a switch is used.
1 energizes the solenoid coil assembly 9
I controlled. Specifically, turn ON / OFF for 5 seconds each
Repeat (duty ratio 50%), Helicon wave mode
Alternate processing in ICP mode was performed.

In the present plasma CVD process, the high-order silane-based deposition species formed by the reaction of SiH _{4 in} the plasma becomes a highly fluid film-forming precursor on the cooled substrate 1. It is condensed and liquefied and flows into the space between the Al-based metal wirings 25. Since a large amount of O ⁺ flux generated when the solenoid coil assembly 9 is energized enters there, the removal and densification of hydrogen in the deposited film proceed rapidly. Next, when the intermittent connection means 11 is turned off,
The higher-order silane-based deposition species again become a highly fluid film-forming precursor and are condensed and liquefied on the cooled substrate 1 to be processed. By repeating this process, the flattening insulating film 23 having a completely flat surface is formed as shown in FIG.

According to the present embodiment, since the liquefaction process of the deposited species and the oxidation process of the reactive species are separated to form the insulating film,
Each process condition such as selection of duty ratio can be optimized, and it is possible to form a flattening insulating film having a small H content and excellent film quality.

Although the present invention has been described with reference to the two examples, the present invention is not limited to these examples.

For example, T is used as a source gas which becomes a deposition seed.
MS and monosilane are shown as examples, but other examples are Tetraeth
yl orthosilicate (TEOS), Te
tramethy orthosilicate (T
MOS), Diacetoxy digitally
butoxy silane (DADBS), Tetr
Other organic silane-based gas such as ethylsilane (TES) or inorganic silane gas such as Si ₂ H ₆ and Si ₃ H ₈ may be used.

Further, PH ₃ , B ₂ H ₆ , AsH ₃ and Tri
methylphosphate (TMP), Ttime
It is also possible to form an silicate glass such as PSG, BSG, BPSG, AsSG by adding an impurity source gas such as tylborate (TMB).

[0041] O ₃ in addition to O ₂ as a source gas as a _{reactant, H 2 O, H 2 O} 2, N 2 O, may be used an oxidizing gas such as NO _2, NO. Since the addition of a small amount of a basic gas such as NH ₃ , N ₂ H ₄ or alkylamine acts as a catalyst for the dehydration condensation reaction of the organic silane-based gas such as TEOS, the film quality can be further improved. Further, if a gas that serves as a nitriding agent such as N ₂ is adopted, it is possible to form a flattening insulating film such as Si ₃ N ₄ or SiON. Also, CF ₄ , C ₂
If a gas such as F ₆ , C ₃ F ₈ , SiF ₄ or NF ₃ that can generate active species of F is added to the plasma, a SiOF-based flattening insulating film having a low dielectric constant can be formed.

In the above embodiment, the helicon wave mode and the ICP mode are switched by turning ON / OFF the power supply to the solenoid coil assembly 9.
The upper part of the VD chamber 15 may be composed of a cylinder made of a dielectric material such as quartz, and an ICP coil may be separately wound around this cylinder. By adopting this configuration, it becomes possible to control the structure of the deposited species by improving the radical generation rate by the ICP coil, and the degree of freedom of the process factor is improved.

In the second embodiment described above, the case of forming the interlayer insulating film on the Al-based metal wiring was illustrated, but the case of using another wiring material layer such as polysilicon, silicide, refractory metal, or the final passivation film. It goes without saying that it can be applied when used as.

[0044]

As is apparent from the above description, according to the present invention, a liquid phase CVD apparatus equipped with a substrate stage cooling means and a helicon wave plasma source is used to form a liquid crystal on a substrate to be processed. It is possible to surely fill the steps, recesses, and grooves having a large aspect ratio with an insulating film having a good film quality to obtain a flat surface.

Since there are no residual organic substances, hydrogen, bubbles, etc. in the formed flattening insulating film, a dense and highly reliable flattening insulating film can be obtained. Further, since the secondary flattening process such as etch back or CMP is not required after the film formation, the throughput of the whole process can be improved.

Further, by controlling the ON / OFF of the solenoid coil, the above effect can be thoroughly achieved by adopting a constitution in which the liquefaction of the deposited species and the oxidation reaction by the reactive species are alternately repeated.

Due to the above effects, it is possible to improve the reliability of the flattening insulating film and the like of the semiconductor device having a high step due to the heavy use of the multi-layer wiring, and it is applied to the manufacturing process of the high performance semiconductor device based on the fine design rule. The effect of the invention is extremely large.

[Brief description of drawings]

FIG. 1 is a helicon wave plasma CVD according to a first embodiment of the present invention.
It is a schematic sectional drawing which shows the structural example of an apparatus.

FIG. 2 is a helicon wave plasma CVD according to a second embodiment of the present invention.
It is a schematic sectional drawing which shows the structural example of an apparatus.

3A and 3B are schematic cross-sectional views illustrating a plasma CVD method according to a first embodiment of the present invention, in which FIG. 3A is a state in which a trench is formed in a semiconductor substrate, and FIG. 3B is a state in which the trench is filled with a planarization insulating film. It is in a state.

4A and 4B are schematic cross-sectional views illustrating a plasma CVD method according to a second embodiment of the present invention, in which FIG. 4A is a state in which Al-based metal wiring is formed on a lower insulating film, and FIG. 4B is Al-based metal wiring. This is a state in which a flattening insulating film is formed on the upper surface.

[Explanation of symbols]

 1 substrate to be processed 2 substrate stage 3 substrate stage cooling means 4 substrate bias power supply 5 bell jar 6 helicon wave antenna 7 helicon wave plasma power supply 8 matching network 9 solenoid coil assembly 10 solenoid coil power supply 11 intermittent interruption means 12 multi-pole magnet 13 1st Gas shower ring 14 Second gas shower ring 15 CVD chamber 21 Semiconductor substrate 22 Trench 23 Flattening insulating film 24 Lower insulating film 25 Al-based metal wiring

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/3205 21/768 H01L 21/90 K

Claims (4)

[Claims] 1. A substrate stage cooling means capable of cooling a substrate to be processed in a plasma CVD chamber to a temperature equal to or lower than a dew point of a deposition species, and a helicon wave plasma generation source connected to the plasma CVD chamber. , Plasma CVD
apparatus. 2. The plasma CVD apparatus according to claim 1, further comprising an intermittent interrupting means for the solenoid coil current of the helicon wave plasma generation source. 3. The substrate to be processed is irradiated with the reactive species generated by a helicon wave plasma generation source while liquefying and condensing the substrate to be processed cooled below the dew point of the deposition species. Plasma CVD method. 4. The step of liquefying and condensing the deposition species on the substrate to be processed cooled below the dew point of the deposition species and the step of irradiating the substrate with the reactive species generated by the helicon wave plasma generation source are alternately performed. A plasma CVD method characterized by applying.