JPH10189491A - Formation of insulation protective barrier for ti-si-n and ti-b-n base having low defect density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the defect density of an insulation protective film by providing a porous barrier layer containing titanium and nitrogen, performing post- treatment and introducing silicon into at least the uppermost face of the porous layer. SOLUTION: TDMAT and [(CH3 )2 N]4 Ti are thermally decomposed (104) and a wafer is heated while being exposed to a precursor substance thus decomposing the precursor substance thermally and bonding the decomposed precursor substance onto the wafer in the form of a film. The film is composed of Ti-N-C which is a porous material absorbing O2 easily. Subsequently, it is heated (106) preferably in pure silane atmosphere, diluted silane atmosphere, disilane atmosphere or any other atmosphere for forming silicon in a film. Thereafter, the wafer is further processed or exposed to oxygen atmosphere (108) before being processed furthermore. According to the method, oxygen is absorbed into the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an integrated circuit structure and a manufacturing method.

[0002]

BACKGROUND OF THE INVENTION Titanium nitride (TiN) is commonly used as a diffusion barrier in contacts, vias, trenches and interconnect stacks. Titanium nitride is also used as an adhesion layer for chemical vapor deposition (CVD) tungsten.
VD tungsten and CVD aluminum can also serve as nucleation layers. A good barrier layer has good step coverage, achieves void-free plug formation, achieves a sufficient barrier thickness at the bottom of the contacts / bias / trench, has good diffusion barrier properties, Prevent diffusion and prevent WF ₆ attack on underlying metal or silicon. Inert to adjacent materials during thermal cycling, low reactivity, and acceptable electrical properties. For example, low contact / bias resistance and low junction leakage are required. In addition, the barrier layers need to be as thin as possible to reduce the thickness of the interconnect stack.

[0003] Reactive sputter Tix and TiN formed by rapid thermal nitridation of titanium have traditionally been used as diffusion barriers. Recently, there has been a tendency to replace the PVD TiN with the CVD TiN to satisfy the requirement of step coverage for contacts, trenches and biases of 0.35 μm or less. CVD
TiN overcomes metal reliability issues and the joint leakage issues associated with PVD TiN, while CVD TiN can withstand thermal stress at 550 ° C. while maintaining low contact resistance and leakage. Further, CVDTiN is a potentially cleaner method than collimated PVD TiN.

CV deposited by reaction between TiC ₄ and NH ₃
Although DTiN has been used, there are several problems. Some of the problems are high deposition temperatures, Ti
Incorporation of chlorine like Nl, NH ₄ C
1 particles are produced. Although chlorine contamination can be reduced, such methods cannot eliminate it. When the film is deposited at temperatures below 400 ° C., the TiC
_{The 4} / NH ₃ method is not available, but metal-organic precursors can be used. Two commonly used metal-organic precursors are tetrakismethylaminotitanium (TDMA)
T) and tetrakisdiethylaminotitanium (TDEAT)
It is. The deposition of CVD TiN based on the thermal decomposition of TDMAT forms a layer with good step coverage and low particle count, but results in an unstable film with high resistivity. The resistivity can be improved by reacting the metal-organic precursor with ammonia, but the reaction of TDMAT and NH ₃ results in a film with poor step coverage and potential problems associated with the gas phase reaction, such as particle formation. is there.

[0005] TDMAT or TD without ammonia
The possibility of depositing TiN using EAT has been discussed in the literature, but does not teach the following. That is,
Films deposited from TDEAT or TDMAT without the use of ammonia are said to have very poor properties. For example, Sun and Tsai: "Characteristics of low pressure chemical vapor deposited titanium nitride from metal organic sources" [(ESSDERC '9
4 Bulletin, pp. 291-4). This document is incorporated herein by reference].

[0006] Ti-Si-N compounds are attractive for modern metallization applications because they provide a better diffusion barrier than TiN. Currently, Ti-Si-N
Two major methods of membrane production are under investigation, both with significant limitations. (Reactive sputtering of Ti-Si target in N ₂ atmosphere was performed at California Institute of Technology (C
al Tech), is the most established method, as represented by the extensive direction of sputtering, but due to the orientation of the sputtering method, the step coverage of the deposited film can be reduced for high aspect ratio contacts, vias and trenches. Very poor.

A chemical vapor deposition method using a mixture of silane, ammonia and TDEAT is under study at Sandia National Laboratories. This method can provide a film with better step coverage, but has the disadvantage of combining TDEAT with NH _3. In the phase reaction, particles are formed, and the defect density of the resulting film is high.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an innovative method for producing an insulating and protective Ti-Si-N film having a low defect density and solving the above two problems.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method according to the invention in which a porous barrier layer containing titanium and nitrogen is first deposited and then a post-deposition treatment is carried out so that at least the top surface of the porous layer is This is achieved by introducing silicon to provide a silicon-rich surface. (In another embodiment, the post-deposition treatment introduces boron instead of or in addition to silicon). The porous barrier layer also preferably contains a significant proportion of carbon and, if necessary, a significant proportion of silicon before processing after deposition.

An advantage of the method and structure of the present invention is that T
Since the surface of the i-Si-N film is rich in Si (or Ti-B-
Since the N film surface is rich in B), the absorption of oxygen into the film is minimized, and the formed film is stabilized. In addition, the fact that the surface is rich in Si or B is useful for improving the wetting of Al and the adsorption to Cu, and is therefore useful for the application of the latest metallization. Compared with the sputter method, the present invention provides a method for adhering a film, in which the step coverage is extremely good and the control of the Si / Ti ratio is easy. Compared with the TDEAT + NH ₃ + SiH ₄ method, the present invention eliminates the gas phase reaction between the Ti source and NH ₃ and can provide an insulating protective film having a low defect density.
The method of the present invention is flexible in controlling chemical composition, including surface composition. The method of the present invention can be carried out in a commercial CVD reactor and is easy to carry out.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described with reference to the accompanying drawings, which show important representative embodiments of the invention, and are incorporated herein by reference.

While a number of innovative features of the present invention will be described with particular reference to the presently preferred embodiments, these embodiments set forth herein illustrate some of the many useful applications of the innovative features. It is only an example shown. In general, the disclosure herein does not necessarily limit any scope of the various claimed inventions. In addition, some disclosures are for some features of the invention and not for others.

FIG. 1 is a flowchart showing the flow of the process according to one embodiment of the present invention. The starting point for manufacturing a device using the present invention is the same as for processing many devices. In fact, standard processing applies to all steps from the formation of intermediate level dielectrics to the formation of trenches or holes for bias / contact. Furthermore, standard processing can be additionally used after the formation of the TiN-based layer and after the inventive annealing step of the present invention. The method of the present invention starts with a metal-organic chemical vapor deposition (MOCVD) process to form a titanium nitride film (step 104). This film may be on an intermediate level dielectric, on the sidewalls of the trench or hole, on the bottom of the trench or hole, in a conventional TiN
Are formed at other locations where they have been used. Preferably,
Step 104 is performed by thermal decomposition of TDMAT and [(CH ₃ ) ₂ N] ₄ Ti. TDMAT is a liquid, preferably introduced into the reactor using a carrier gas such as He or N _2. This decomposition is preferably carried out at temperatures between 300 ° and
The process is performed at a temperature of 500 ° C. and a pressure of 0.1 to 50 torr. The decomposition time varies depending on the desired film thickness. In another embodiment, the C ₂ H ₅ the precursors used in place of CH ₃ [(C
₂ H ₅ ) ₂ N] ₄ Ti. In yet another embodiment, the precursor is preferably [[CH ₃ ) (C ₂ H
₅ ) N] ₄ Ti.

In step 104, the wafer is heated while being exposed to the precursor to thermally decompose the precursor and deposit the film on the wafer. The formed film is made of Ti—N—C, is a porous material, and easily absorbs O ₂ . Due to the absorption of O ₂ , this film has a high resistance and becomes extremely unstable. In particular, the resistivity of this film increases significantly as the film is exposed to oxygen-containing air (curve 20 in FIG. 2).
2).

Next, a heating step is performed (step 106).
This step is carried out preferably pure silane atmosphere or diluted silane atmosphere, disilane atmosphere, B ₂ H ₆ atmosphere or silicon or boron can be formed in the film in any other atmosphere. Preferably, this step is carried out at a temperature of about 350 ° -500 ° C.
This is performed under a pressure of 0.1 to 50 torr for about 15 to 240 seconds. Annealing step 106 may be performed in the same reactor as deposition step 104, or may be performed in another similar reactor. If performed in the same reactor, the temperatures used in both MOCVD step 104 and annealing step 106 are preferably substantially the same. If both steps are performed in separate and similar reactors, the film formed in step 104 must not be exposed to oxygen prior to step 102. After step 106 is completed, the film has the following structure: T when using a Si-containing gas.
When using i-NC-Si and B-containing gas, Ti-NC-
B. The incorporation of Si into the film can be seen from curve 302 in FIG. 3b.

After performing step 106, the wafer is further processed or exposed to an oxygen atmosphere (step 108) and then further processed. After performing step 108, oxygen is absorbed into the film and the film assumes the following configuration: Ti-NC-Si-O when using a Si-containing gas, and Ti- when using a B-containing gas.
NCBO. However, oxygen is not absorbed unless the wafer is exposed to an oxygen atmosphere.

Although the above is particularly concerned with the formation of a titanium-based barrier film, other transition metals may be used in place of titanium. In particular, tungsten, tantalum or molybdenum can be used instead of titanium for forming the barrier layer of the present invention.

FIG. 2 shows the sheet resistance R _S of two different films. The X-axis in FIG. 2 represents the amount of air exposure time (minutes) of the film, and the Y-axis represents the sheet resistance (ohm / square) of the film. The film not subjected to the step 106 has a high sheet resistance. This is Figure 2
The curve 202 of FIG. Further, as can be seen from curve 202, the sheet resistance of the film without step 106 increases significantly after exposing the film to oxygen, but after performing step 106, the sheet resistance becomes (compared to curve 202). T) Small size and extremely good stability in air. This is shown by curve 204.

Further, Table 1 shows a comparison of the sheet resistance of the 20 nm film as experimental data. The variables in these three tests are the silane treatment time, the presence or absence of rapid thermal annealing (RTA), and the various operating temperatures.

[0020]

[Table 1]

FIGS. 3a and 3b are XPS depth graphs showing the concentration of carbon, oxygen, nitrogen, titanium and silicon at various depths. The X axis in each figure corresponds to each depth.
The length of the sputter time represents the depth distance. The Y-axis in both figures represents the total total reference atomic concentration (AC%). It can be seen from the curve 302 in FIG. 3B that the film treated in the step 106 contains silicon, but the film not treated in the step 106 does not contain silicon (in the curve 301 in FIG. 3A, the top surface of the film is 0 second). And the bottom is displayed in about 16 minutes).
Silicon uptake is important for reducing the uptake of oxygen from the air, which reduces resistivity and increases stability. The incorporation of silicon or boron is advantageous in the subsequent metallization of Cu or Al.

The curve 304 in FIG.
It shows that oxygen absorption is limited in the film after treatment.

FIG. 4 is a transmission electron diffraction (TEM) pattern. FIG. 4 shows that the process 106 (0 and 108) processing film is amorphous. Amorphous films are preferred for use as barriers (as opposed to polycrystalline films). This is because in a polycrystalline structure, metal diffusion proceeds rapidly at grain boundaries.

FIG. 5 is a flow chart of a second embodiment of the method of the present invention. This method is the same as the method of FIG. 1 except that silane gas is added in the MOCVD step. This allows more silicon to be incorporated into the layer and facilitates better tuning of the Si / Ti ratio.

FIG. 8 is a graph showing the relationship between the sheet resistance of the Ti—Si—N deposited film and the silane annealing time after deposition. Resistance was measured after two days of exposure to air. It clearly shows that the sheet resistance drops sharply after annealing for about 30 seconds in silane.

FIG. 9 is a graph showing the relationship between the sheet resistance of the Ti-Si-N deposited film and the flow rate of silane during the deposition of Ti-Si-N. The measurement was performed after air leakage for two days. As can be seen, as the silane flow rate increases, the sheet resistance of the film increases, so the increase in barrier as a result of silicon incorporation must be balanced with the high resistance of silicon.

FIG. 10 is an electron micrograph showing the cross-sectional structure of the layer of the present invention, and shows that the method retains the insulating protection of the layer.

Another Exemplary Deposition Method Embodiment In this embodiment, in a first step, TDMAT is pyrolyzed in the presence of nitrogen to form a TiN layer. Immediately after deposition, the layer is exposed to a silane atmosphere and the silane reacts with the layer to incorporate silicon into the layer to form a silicon-rich surface layer. Oxygen absorption that causes layer deterioration due to the presence of silicon is suppressed.

Further, when TDMAT is used as a precursor, carbon can be taken into the layer in a high percentage, and it is thought that the carbon in the layer is not a problem. It does not affect the circuit life.

[0030]

[Table 2]

Embodiment 2 of Deposition Method In this embodiment, in the first step, a barrier layer is formed by combining SiH ₄ , TDMAT and N ₂ (a diluent is used. When the depth becomes sufficient, the flow of TDMAT and N ₂ Is stopped, but Si
H ₄ flows continuously during the measurement time. The described embodiment is the presently preferred embodiment.

[0032]

[Table 3]

Embodiment 3 of the Deposition Method SiH ₄ can be replaced by another Si source compound, for example, Si ₂ H ₆ . In the present embodiment, in the first step, Si ₂ H
₆ and TDMAT are flowed together with the inert N ₂ , the flow of TDMAT and N ₂ is stopped in a second step, and Si ₂ H ₆ is flowed to allow extra silicon to be incorporated into the layer surface.

Embodiment 4 of Deposition Method TDMAT was converted to TMEAT, ie, Ti (NCH ₃ C
₂ H ₅₎ is replaced with _4, this embodiment, flow silane in the first step, TMEAT, the N ₂ together. In the second step, pure silane is flown to additionally incorporate silicon into the surface layer.

Embodiment 5 of Deposition Method TDMAT is converted to TDEAT, that is, Ti (N (C ₂ H ₅ )
₂ ) Substitute ₄ In this case, TDEAT, flowing silane with N ₂ or other inert diluent Si-N
Depositing a Ti layer and increasing the silicon concentration in the upper surface using only silane in the next step.

Embodiment 6 of Deposition Method In this embodiment, a Ti _x B _y N film is formed using a boron source. Therefore, the boron source component (for example, B ₂ H ₆ )
Used when depositing a porous TiN film instead of the source component. This embodiment is adhered with Ti-B-N layer by flowing a TDEAT and diborane together with N ₂ or other diluent, to increase the boron concentration in the upper surface by using only diborane in the next step.

Exemplary Metallization Embodiments The methods described herein apply metallization,
In particular, it can be used in copper (Cu) metallization. For example, in the application shown in FIG.
A semi-finished structure including a transistor (not shown) under a conductive layer 510 (typically an aluminum alloy) surrounded by 5 is provided. Then, the top intermediate level dielectric 520 (eg, BPS on TEOS deposited SiO ₂ )
G) is deposited and planarized by conventional methods (eg, chemical-mechanical polishing or CMP). Next, (Damasc
ene) The intermediate level dielectric 520 is patterned and etched (in a manner of the type) to form the slots 530 where metallization lines are desired, and bias is desired (i.e., electrical connection to the lower conductive layer). (A contact is desired) to form a deeper hole 540. Next, a diffusion barrier layer 530 is deposited using one of the methods described above. A highly conductive metal 550 (e.g., copper) is deposited over the entire surface in a conventional manner, and the entire surface is etched (e.g., using CMP) to remove the flat surface of the intermediate level dielectric 520 to metal 5
It is exposed at a position where 50 does not exist.

In this embodiment, the barrier layer of the present invention is formed all over the exposed portion of the intermediate level dielectric 520. That is, there is no point where the metal 550 directly contacts the intermediate level dielectric 520. This reduces the likelihood of copper atoms (or lifetime shortening agent, eg, gold) diffusing into the semiconductor substrate through the intermediate level dielectric.

Representative Metallization Embodiment 2 Another metallization embodiment shown in FIG. 7 is for forming a transistor having a polycide (polysilicon / silicide) gate 560 arranged in the direction of source / drain diffusion 562. Including, then, forming a first intermediate level dielectric layer 564 (if necessary, a plurality of additional layers, not shown but having a corresponding plurality of additional intermediate level dielectric layers, Patterning is often performed). The contact locations 566 are patterned and etched prior to depositing the barrier layer 570 using the inventive method disclosed herein. Next, the metal layer 580
And patterning is performed. In the present exemplary embodiment, the metal layer 580 is an aluminum alloy, which is (in this preferred embodiment, Forcefill ^™ ).
Fill ^TM ) method is forcibly injected into the contact hole under high pressure.

The disclosed innovative embodiments include (a) providing a substrate containing at least one substantially monolithic object of semiconductor material; and (b) isolating by CVD in a titanium and nitrogen containing atmosphere. Attaching a conductive layer;
(C) exposing the insulating protective layer to an atmosphere containing silicon or boron after attaching the insulating protective layer, wherein the step (c) comprises the steps of: A thin film forming method is provided for forming a silicon or boron rich surface on a layer.

Another innovative embodiment disclosed is an integrated circuit comprising a barrier thin film layer containing titanium and nitrogen, wherein the thin film has a gradual change in the composition of silicon or boron,
An integrated circuit having a higher silicon or boron concentration on the first surface is provided.

Modifications and Variations As will be appreciated by those skilled in the art, the innovative concepts described herein can be modified and varied over a wide range of applications, and the scope of the present subject matter is not limited to the particulars herein. Is not limited to the teachings of the embodiment.

The general background of CVD and metallization is described in the following publications, which help show the knowledge of those skilled in the art in their modification and implementation: metallization and metal-semiconductors Interface (Batra edition 198)
9); VLSI Metallization: Physics and Technology (Siena, 1991); Muralka, "Metallization Theory and Practice for VLSI and ULSI (1993)"; Multilevel Metallization Handbook for Integrated Circuits (Wilson et al. 1993); Lao, "Multi-level
Interconnect Technology (1993) "; Chemical Vapor Deposition (M.L.Hitchmann, 1993); Report of the semiannual meeting of the Institute of Electrical Chemistry on Plasma Processing; (all of these publications are incorporated herein by reference).

With respect to the above description, the following items are further disclosed. (1) (a) providing a substrate including at least one substantially monolithic object of a semiconductor material; (b)
Depositing an insulating protective layer by CVD in an atmosphere containing titanium and nitrogen, and (c) exposing the insulating protective layer to an atmosphere containing silicon or boron after depositing the insulating protective layer. And a step of forming a thin film,
A thin film forming method for forming a surface rich in silicon or boron on the insulating protective layer in the step (c). (2) The forming method according to (1), wherein the step (c) is performed immediately after the step (b) without an intermediate step. (3) The method according to (1), wherein the step (b) uses an atmosphere containing silicon or boron. (4) The method according to (3), wherein the step (b) uses an atmosphere containing SiH ₄ . (5) Step (b) includes TDMAT, TMEAT, and TDEA.
2. The forming method according to claim 1, wherein an atmosphere containing a titanium source component selected from the group consisting of T is used. (6) The forming method according to (1), further comprising rapid thermal annealing as a next step. (7) An integrated circuit comprising a barrier thin film layer containing titanium and nitrogen, wherein the thin film has a composition of silicon or boron gradually changed, and a silicon or boron concentration on a first surface thereof is higher than that of the other. High integrated circuit. (8) The integrated circuit according to (7), wherein the thin film contains at least 10% of carbon. (9) The integrated circuit according to (7), wherein the thin film is made of amorphous SiN _x and TiN _x . (10) The integrated circuit according to (7), wherein the thin film is an amorphous combination of TiN _x and boron. (11) The integrated circuit according to (7), wherein the richness of silicon or boron decreases the absorption of oxygen into the thin film. (12) In a method of forming a barrier layer on a substrate and joining contacts / bias, a step of preparing a lower structure, a step of forming a dielectric layer on the substrate, and an opening in the substrate. Exposing at least a part of the lower structure (the opening has a side wall); and forming a film using a metal-organic precursor (the film is formed on the dielectric layer and the opening is formed on the dielectric layer). Forming on the side wall and the exposed portion of the lower structure), and performing a heating step in an active gas atmosphere to incorporate silicon or boron into the film. (13) The metal-organic precursor is [(CH ₃ ) ₂ N] ₄ T
i, [(C ₂ H ₅ ) ₂ N] ₄ Ti, [(CH ₃ ) (C ₂
H ₅₎ N] consisting of a material selected from the group consisting of ₄ Ti, method of paragraph 12, wherein. 14. The method of claim 12, wherein the active gas comprises any gas that incorporates silicon or boron into said metal-organic film. (15) The method according to item 12, wherein the active gas is selected from the group consisting of silane, disilane, diborane or any combination thereof. (16) The method according to (12), which is a substrate of a lower structure. (17) The method according to (12), wherein the lower structure is a conductive layer. (18) A CVD method for Ti-Si-N or Ti-BN, wherein a single supply gas (preferably TDMAT) serves as a titanium and nitrogen source and another supply gas is silicon or boron. Use as a source. This avoids gas phase particle nucleation, while providing good insulation protection. When the predetermined layer thickness has been deposited, the flow of the titanium / nitrogen or titanium / boron source is stopped and then the silicon or boron feed gas is flowed continuously for a period of time. Thereby, a Ti—N film having a low defect density and rich in Si or B and having an insulating protection property is formed. In a second embodiment, a single feed gas, such as TDMAT, is pyrolyzed to form a Ti-N layer. Annealing after deposition is performed in a gas that supplies silicon or boron to incorporate these substances into the layer. Incorporation of silicon or boron into this layer minimizes oxygen absorption into the film and thus stabilizes the formed film. Surfaces rich in Si or B also help improve Al wetting and adhesion to Cu, and are therefore useful for modern metallization applications. Compared with the sputter method, the present invention provides a method for depositing a film having excellent step coverage and easy control of the Si / Ti ratio. TDEAT + NH ₃ +
Compared to the SiH ₄ method, the present invention eliminates the gas phase reaction between the Ti source and NH ₃ .

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating one embodiment of the present invention.

FIG. 2 is a graph showing sheet resistance (as a function of air exposure) of a film formed using a prior art film forming method and a film formed using one embodiment of the present invention.

FIGS. 3a and 3b are X-ray photoelectron spectroscopy (XP
S) is a graph showing data obtained from a cross-sectional analysis in a depth direction, where a is carbon in a film formed using a method of the related art,
B represents the atomic concentration of oxygen, nitrogen, titanium, and silicon, and b represents the atomic concentration of carbon, oxygen, nitrogen, titanium, and silicon in the film formed using the method of the present invention.

FIG. 4 is a transmission electron diffraction diagram of a film formed using the method of the present invention.

FIG. 5 is a flowchart showing a second embodiment of the present invention.

FIG. 6 shows an example of metallization on a barrier film layer deposited by the innovative method of the present invention.

FIG. 7 shows an example of metallization on a barrier film layer deposited by the innovative method of the present invention.

FIG. 8 is a graph showing the relationship between the sheet resistance of deposited Ti—Si—N and the silane annealing time after deposition.

FIG. 9 shows the sheet resistance of deposited Ti—Si—N and Ti
4 is a graph showing a relationship with the flow rate of silane during the deposition of -Si-N.

FIG. 10 is a photomicrograph showing the cross-sectional structure of the innovative layer of the present invention (showing that the method of the present invention retains the insulating properties of the layer).

Claims (2)

[Claims] 1. A method comprising: (a) providing a substrate comprising at least one substantially monolithic object of a semiconductor material; and (b) depositing a conformal layer by CVD in an atmosphere comprising titanium and nitrogen. And (c) exposing the insulating protective layer to an atmosphere containing silicon or boron after depositing the insulating protective layer, the method comprising: A thin film forming method for forming a surface having a high silicon or boron concentration on the insulating protective layer. 2. An integrated circuit comprising a barrier thin film layer containing titanium and nitrogen, wherein the thin film has a composition of silicon or boron that changes gradually, and the first surface has a silicon or boron concentration other than that of silicon or boron. Higher integrated circuit than.