JP2009081179A - Insulating film of bcn system, its manufacturing method, semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device, which can form a BCN film having a stable low dielectric constant and a high hardness (Young's modulus). <P>SOLUTION: The BCN film is formed by using organic amino boron gas without corrosivity, which is replaced as conventional BCl<SB>3</SB>gas. An insulator material film of the low dielectric constant of a BCN system whose specific inductive capacity is 2.5 or below and whose elastic modulus (Young's modulus) is 8 GPa or above is obtained by forming the film with plasma CVD by using tris(dimethylamino)boron, as an example. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

 The present invention relates to a BCN-based insulating film, a manufacturing method thereof, a semiconductor device, and a manufacturing method thereof, and more particularly to a BCN-based insulating film having a low dielectric constant, a manufacturing method thereof, a semiconductor device, and a manufacturing method thereof.

In silicon semiconductor integrated circuits, 65-nm generation system LSIs and 1-Gbit memories have already been produced, and further finer devices are being developed from 45 nm to 32 nm generation. This device development has progressed with the advantage that high-speed operation can be improved by reducing the size of the transistor, but in recent years, the wiring within the device has become longer due to the increased degree of integration and the wiring resistance and wiring are separated. An electrical signal delay phenomenon due to the capacitance of the insulating layer that has been encountered has encountered the problem of degrading the high-speed operation of the device.
In order to solve this problem, wiring metal (aluminum) and wiring interlayer insulating film (SiO2 (relative dielectric constant k to 4)), which has been conventionally used, are made into a metal having a lower electric resistivity and an insulator material having a lower dielectric constant. Research and development is underway to make changes. The wiring metal was changed from aluminum to copper. On the other hand, the dielectric constant of the interlayer insulating film research SiOF or SiOC and SiC was added fluorine and carbon SiO ₂ is focused is made, currently, the k~2.5 as a wiring interlayer insulating film SiOC is mainly used.

  The development of a low dielectric constant film having k <2.2 is eagerly desired for the development of next-generation silicon integrated devices. Due to the trend of practical years for low dielectric constant film (Low-K film) of system LSI using Cu wiring, development of Low-K film for 45 nm generation was promoted in FY2006. It has been studied by forming pores in the insulating film of the system to reduce the dielectric constant. However, such a porous Low-K film has various problems to be solved with respect to introduction into a silicon integrated device as well as development of a film forming method.

The problems with porous low-k films are 1) low mechanical strength, 2) high water absorption, 3) low thermal conductivity, and 4) higher thermal expansion coefficient than other insulating films. Can be mentioned. Each problem is described in detail below.
1) Due to the low mechanical strength, in the CMP (Chemical Mechanical Polishing) process used when forming the Cu wiring, the Low-K film is deformed without being able to withstand the load, and the adhesion with the base film is poor. This causes problems such as peeling.
2) Since it becomes easy to absorb water by making it porous, the dielectric constant increases. This is because the dielectric constant of water is as high as about 80. In addition, when the Cu wiring is formed, there also arises a problem that the Cu plating solution penetrates into the porous film through a portion not sufficiently covered with the barrier film.
3) Since the current density is about 105 A / cm ² inside the high-performance CPU, a highly heat-conductive material is desired for the wiring interlayer film to also serve as a heat sink. However, the porous material may reduce the thermal conductivity of the material to about 1/10.
4) In an annealing process when manufacturing an LSI, a void (gap) is generated around the Cu wiring due to a difference in thermal expansion coefficient between the interlayer insulating film and the wiring material Cu. When a multilayer wiring is formed, heat treatment is applied to each layer, so that expansion and contraction are repeated and wiring stress migration is likely to occur.
In addition, there are many problems with the current porous film such that the low-k film on the processed surface is altered by a dry etching gas at the time of groove processing or a chemical solution for polymer removal.
Under such circumstances, the BCN film material is a promising material having excellent physical properties with respect to the above-mentioned four items which are problems in porous low-k. In particular, a BN film containing boron (B) is hard and widely used as a cutting material, and it has been reported that a BCN film containing C also has a Young's modulus of 100 GPa or more (Non-Patent Document 1).
When considering the dielectric constant of the BCN-based material, the molecular polarizability volume is also a reference, as in the case of the SiOC-based Low-k film. In order to reduce the dielectric constant, it is necessary to reduce the component of orientation polarization. For example, a single bond of C—C has a smaller polarizability than a double bond of C═C, and is suitable for a low dielectric constant material. Will be. Therefore, it is desirable to form a film with a single bond in order to reduce the dielectric constant.

C. Morant, D.M. Caseres, J .; M.M. Sanz and E.M. Elizalde, Diamond and Relat. Mater. 16 (2007) 1441. Japanese Patent Laying-Open No. 2005-210136

  So far, SiOC-based porous LowK films have been studied. However, since the mechanical strength and hardness are low, there is a problem that the mechanical strength of CMP and mechanical damage during wire bonding cannot be tolerated. Therefore, a low-k material having a dielectric constant of 2.3 or less while maintaining hardness (10 Gpa or more in Young's modulus) is desired.

In the preparation of a BCN film, conventionally, BCl ₃ gas has been used to introduce boron (B) (for example, Patent Document 1). However, when used as an interlayer insulating film for LSI wiring, the contained chlorine (Cl) component may corrode Cu wiring or the like. Further, in the conventional mixed gas system, in addition to the BN single bond, depending on the film forming conditions, a CC double bond or a BN triple bond (the dielectric constant increases because the polarization volume ratio is high) occurs. It is difficult to stably form a film having a low dielectric constant.

  An object of the present invention is to provide an insulating film capable of maintaining the reliability of wiring without corroding wiring (for example, Cu wiring) and a method for manufacturing the same.

  An object of this invention is to provide the insulating film which can maintain a low dielectric constant stably, and its manufacturing method.

  An object of this invention is to provide the insulating film which has high mechanical strength, and its manufacturing method.

The present invention is characterized in that a BCN film is formed using an organic aminoboron-based gas that does not corrode instead of BCl ₃ gas. Examples of the organic aminoboron gas include trisdimethylaminoboron (TMAB) and dimethylaminoboron. TMAB is preferable because the methyl group of CH ₃ can be relatively stably incorporated into the film.

  As a film formation method, for example, film formation may be performed by plasma CVD.

The chemical formula of trisdimethylaminoboron (TMAB) is B [N (CH ₃ ) ₂ ] ₃ , and the bond energy between the atoms constituting the gas is BN <CN <CH Strong in order. Therefore, when decomposed by plasma, the BN and CN bond portions are first cut, and CH3 (methyl group) remains, and is taken into the BCN film. Thereby, a space is created in the vicinity of CH3 in the film, and the dielectric constant can be stably reduced.

  The invention according to claim 1 is an insulating film manufacturing method for forming a boron nitride carbon (BCN) insulating film using an organic aminoboron gas.

  The invention according to claim 2 is the method for producing an insulating film according to claim 1, wherein the organic aminoboron gas is trisdimethylaminoboron.

The invention according to claim 3 is a step of forming a first insulating film on a lower wiring formed on a semiconductor substrate;
Forming a second insulating film on the first insulating film;
Dry etching the second insulating film and the first insulating film to form an opening reaching the lower layer wiring;
Forming a barrier metal film on the inner surface of the opening and the second insulating film;
Forming a conductive layer on the barrier metal film so as to embed the opening;
Except for the inside of the opening, a part of the conductive layer, the barrier metal film, and the second insulating film is removed by a chemical mechanical polishing method, and an upper layer wiring electrically connected to the lower layer wiring is formed. Having a process of forming,
The step of forming the second insulating film is a method for manufacturing a semiconductor device, which is a step of forming a film by a CVD method using at least an organic aminoboron-based gas.

  The invention according to claim 4 is the method for manufacturing a semiconductor device according to claim 3, wherein the RF power in the CVD method is 40 W or less.

  The invention according to claim 5 is the method for manufacturing a semiconductor device according to claim 3 or 4, wherein the organic aminoboron gas is trisdimethylaminoboron.

  The invention according to claim 6 is the method for manufacturing a semiconductor device according to any one of claims 3 to 5, wherein the dry etching is performed using a fluorocarbon gas.

  The invention according to claim 7 is a BCN-based insulating film manufactured by the method according to claim 1 or 2.

  The invention according to claim 8 is a BCN-based insulating film having a relative dielectric constant of 2.5 or less and an elastic modulus (Young's modulus) of 8 GPa or more.

  The invention according to claim 9 is a semiconductor device having the insulating film according to claim 7 or 8 as an insulating film between wiring layers.

  According to a tenth aspect of the present invention, a conductive layer is filled in the wiring groove provided in the insulating film according to the seventh or eighth aspect and the via hole provided in the BCN insulating film corresponding to the wiring groove. A semiconductor device having a structure.

  The invention according to claim 11 is the semiconductor device according to claim 10, wherein the via hole is formed by dry etching using a fluorocarbon gas.

According to the present invention, residual Cl caused by BCl3 gas does not exist in the interlayer insulating film, so that the Cu wiring is not corroded and the reliability of the wiring can be maintained. Moreover, since CH3 is structurally taken into the BCN film, a low dielectric constant can be stably maintained.

  The BCN film was formed by using a PACVD (Plasma-Assisted Chemical Vapor Deposition) method. The flow rate of trisdimethylaminoboron (TMAB) gas is 0.5-5 sccm, the flow rate of N2 gas is 0.5-5 sccm, the deposition temperature is 300 ° C.-400 ° C., the deposition pressure is 0.1-0.5 Torr, RF The experiment was conducted in a power range of 10 to 100W. In order to prevent the TMAB gas from being liquefied inside the pipe, it is desirable to supply the gas by heating the gas cylinder, the gas pipe and the mass flow controller to 50 ° C. or higher.

In the experiment, N ₂ was deposited at ₂ ccm, TMAB at 1 ccm, the growth pressure was 0.2 Torr, the deposition temperature was 350 ° C., and the RF power was 10 to 1000 W. The composition ratio is 35 to 40% for B, 20 to 25% for C, and 30 to 40% for N (% is% by weight). In atomic%, B is 33 to 47%, C is 13 to 28%, and N is 14 to 32%.

The flow rate ratio between N ₂ and TMAB is preferably 2: 1 to 1: 1. By setting it within this range, there is an advantage that the plasma can be stably formed and the target film composition can be obtained more reliably.
Also, it is preferable to introduce TMAB after introducing N2 gas first and plasma is stabilized (about 30 to 60 sec) in order to obtain a desired film composition more reliably.

  From the experiments, the relative permittivity (k value) of the BCN film tended to be smaller as the RF power was lower. FIG. 1 shows a relative dielectric constant (k value) formed using a conventional BCl 3 gas and a TMAB gas (RF power: 20 W) of the present invention. The film formation using the TMAB gas was performed at 20 W, and there was only a change of about ± 0.5 around k = 2.08. On the other hand, the conventional BCl3 film has k = 1.9 units at the minimum value, but as a whole, there is a variation of about ± 2.0 around k = 2.14, and the k value varies. Yes.

  The preferred range of RF power is 20W-60W. In this range, there are merits that CHAB of TMAB is easily taken into the film without being decomposed, and that double and triple bonds having a large polarization volume fraction are difficult to be formed. More preferably, it is 40 W or less, More preferably, it is 30 W or less.

Further, by performing annealing at 350 ° C. for 30 minutes in an N ₂ gas atmosphere, the k value of the BCN film made of TMAB gas was reduced to the central value k = 1.94 with little variation.

The conventional BCN film growth conditions were N ₂ (1.0 sccm), CH ₄ (0.5 sccm), BCl ₃ (0.8 sccm), H ₂ (1.0 sccm), RF power (80 W), The film temperature was 390 ° C.

The analysis reveals that the elemental composition ratio in the BCN film by the TMAB gas decreases as the RF power decreases and the ratio of B and N decreases and C increases. The reason why the C ratio increases with low RF power is presumed that when the RF power is low, the C—H bond is not decomposed and is incorporated into the film in the form of a methyl group (CH 3). Therefore, FIG. 2 shows the results of measurement of a conventional BCN film formed with BCl ₃ gas and a BCN film formed with TMAB gas by FT-IR (Fourier transform Infrared Spectrometer).

A peak is observed in the TMAB gas in the vicinity of 2962 cm −1 indicating the C—H stretching mode of the methyl group (due to the methyl group CH ₃ ), but this peak is not observed when the BCl ₃ gas is used. The presence of this peak suggests that the methyl group of the C—H bond has been incorporated into the film without being decomposed, and it is assumed that the structure is relatively stable with a large amount of space. Is done. On the other hand, when BCl3 gas is used, there is no methyl group, and conversely, a C—C double bond or a BN triple bond may be formed in the film. In the film formation of the BCl3 gas system, such multiple bonds are often observed by FT-IR depending on conditions.

In preparation of the BCN film, CH ₄ gas may be mixed in addition to the TMAB gas and the N ₂ gas in order to control the C concentration in the film. Further, H ₂ gas may be used for the annealing treatment.

  Next, the strength of the BCN film was measured using a nanoindenter. FIG. 3 shows the relationship with the relative dielectric constant on the vertical axis and the Young's modulus on the horizontal axis. Currently used SiOC-based porous films and organic films have Young's modulus of 10 Gpa or less, but the BCN films created this time have Young's modulus of 26.5 Gpa and 32.1 Gpa, and the film forming conditions are changed. Is also in the range of approximately 20-40 Gpa. Therefore, this BCN film can sufficiently maintain a k value of 2.5 or less and a Young's modulus of 10 Gpa or more. However, if it is too high (too hard), too much stress is applied to the Cu wiring and stress migration occurs in the wiring. 100 Gpa or less is preferable, and 80 Gpa or less is more preferable.

  FIG. 4 shows a wiring structure formed by the dual damascene method using the interlayer insulating film according to the embodiment of the present invention. The dual damascene method is a method in which the via 11 and the trench wiring 12 are simultaneously opened, and the conductive material is buried in the via 11 and the trench wiring 12 at the same time, so that the planarization process is completed once.

First, an insulating layer 14 to be a layer in which the via 11 and the trench wiring 12 are embedded is prepared. The insulating layer 14 uses the BCN film of the present invention as a low dielectric constant material (Low-k material).
Next, resist patterning for opening the via portion is performed on the insulating layer 14 by photolithography, and CF _x -based gas (C _n F _m gas: n and m are integers), for example, C ₄ F ₈ gas The insulating layer 14 is dry etched. In addition, an etching gas such as CF ₄ , CHF ₃ , CH ₂ F ₂ , or CH ₃ F may be used. Further, the trench wiring 12 is also subjected to resist patterning, and the insulating layer 14 is dry-etched with a CF _x gas. In this case, etching is performed up to the depth of the groove, and the etching is stopped halfway. After the via 11 and the wiring groove 12 are formed, the residue is removed by a cleaning process using a chemical solution.

  A TaN film, a Ru film, or a TaN / Ta laminated film is deposited as a via metal 13 on the entire surface where the insulating layer 14 is exposed by sputtering or CVD. A Cu film to be a seed is deposited by sputtering, and the plated Cu film 12 is embedded in the via and the trench wiring. For planarization, the surplus plated Cu film is polished and removed by a chemical mechanical polishing method (hereinafter referred to as CMP method) to form the structure shown in FIG. The metal to be embedded may be a Cu—Al alloy, a Cu—Mg alloy, Ag, or an Ag alloy.

  When the planarizing process using CMP is soft against frictional force, shearing force, etc., a so-called “dishing” indentation is formed in a portion having a wide wiring pattern. Further, “erosion” is caused in a densely packed region. For this reason, in order for the flattening process to be performed satisfactorily, the insulating layer 14 must have an appropriate mechanical strength.

  In the case of the CMP process, the mechanical properties required for the surface film exposed to the flattening process are estimated to have a Young's modulus of about 10 GPa or more, but the BCN film according to the embodiment of the present invention has a Young's modulus of 25 GPa or more. It has mechanical strength and has sufficient resistance. In addition, the dielectric constant is about 2.2, which is sufficiently smaller than that of a normal porous Low K film and the like, and can be expected to exhibit sufficient electrical characteristics as a part of the device.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications and improvements of the damascene method for forming a wiring within the scope of the present invention are within the scope of the present invention. Needless to say, it can be done.

It is a figure which shows the difference in the dielectric constant of the BCN film | membrane by a conventional method and this invention. It is a diagram illustrating the difference in FT-IR spectra of the BCN film according to Example (TMAB) conventional method (BCl ₃₎ and the present invention. It is a figure which shows the Young's modulus and relative dielectric constant of various low dielectric constant films. It is a schematic diagram explaining the wiring structure which concerns on the Example of this invention.

Explanation of symbols

11: Metal embedded in via (Cu film)
12: Metal embedded in wiring trench (Cu film)
13: Barrier metal film (TaN film)
14: Wiring interlayer insulating film (BCN film)
15: Barrier insulating film (SiCN film)
16: Wiring interlayer insulating film (BCN film)
17: Wiring part (Cu film)

Claims (11)

An insulating film manufacturing method for forming a boron nitride carbon (BCN) insulating film using an organic aminoboron gas. The method of manufacturing an insulating film according to claim 1, wherein the organic aminoboron gas is trisdimethylaminoboron. Forming a first insulating film on the lower wiring formed on the semiconductor substrate;
Forming a second insulating film on the first insulating film;
Dry etching the second insulating film and the first insulating film to form an opening reaching the lower layer wiring;
Forming a barrier metal film on the inner surface of the opening and the second insulating film;
Forming a conductive layer on the barrier metal film so as to embed the opening;
Except for the inside of the opening, a part of the conductive layer, the barrier metal film, and the second insulating film is removed by a chemical mechanical polishing method, and an upper layer wiring electrically connected to the lower layer wiring is formed. Having a process of forming,
The method of manufacturing a semiconductor device, wherein the step of forming the second insulating film is a step of forming a film by a CVD method using at least an organic aminoboron-based gas. 4. The method of manufacturing a semiconductor device according to claim 3, wherein RF power in the CVD method is 40 W or less. 5. The method of manufacturing a semiconductor device according to claim 3, wherein the organic aminoboron gas is trisdimethylaminoboron. 6. The method of manufacturing a semiconductor device according to claim 3, wherein the dry etching is performed using a fluorocarbon gas. A BCN-based insulating film manufactured by the method according to claim 1. A BCN-based insulating film having a relative dielectric constant of 2.5 or less and an elastic modulus (Young's modulus) of 8 GPa or more. 9. A semiconductor device comprising the insulating film according to claim 7 as an insulating film between wiring layers. 9. A semiconductor device having a structure in which a conductive layer is filled in a wiring groove provided in an insulating film according to claim 7 or 8 and a via hole provided in the BCN insulating film corresponding to the wiring groove. The semiconductor device according to claim 10, wherein the via hole is formed by dry etching using a fluorocarbon gas.

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