JPH08218169A - Formation of tin film - Google Patents

Abstract

PURPOSE: To improve film quality such as barrier property without lowering step coverage property. CONSTITUTION: An organic metal gaseous starting material contg. Ti is fed into a chamber 101 from a storage vessel 108 through a valve 110, a mass flow controller 111, a vaporizer 112 and a shower head 117. NH3 as a gaseous nitrogen base starting material is also fed into the chamber through a valve 116, a mass flow controller 115 and a shower head 117. While halogen base gas such as Cl2 is fed by a small quantity from a gas introducing port 105, a TIN film is grown. Since the halogen base gas restrains the growth velocity, by adding the halogen base gas, step coverage is not deteriorated even when the temp. of the substrate is raised to improve the film quality.

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method of forming a barrier metal layer formed in a connection hole in a semiconductor device such as an LSI,
In particular, the present invention relates to a method of coating the bottom surface and the side surface of the connection hole with a titanium nitride (titanium nitride: TiN) film as a barrier metal layer by a chemical vapor deposition (CVD) method.

[0002]

2. Description of the Related Art In a semiconductor device such as an LSI, a heat treatment in a wiring process causes a metal such as aluminum (Al), which is a wiring material, to react with silicon (Si) of a substrate at a bottom portion of a connection hole, thereby breaking a bond. Occurs.
In order to avoid this problem, a TiN thin film is deposited between a metal such as Al or tungsten (W) and Si of the substrate.

This is because TiN does not react with Si even at a high temperature of 900 ° C. or higher, and further suppresses diffusion of impurities such as phosphorus (P) and boron (B) in Si, and further, Al This is because it is possible to suppress the diffusion of Si into Si.

Conventionally, a TiN thin film of this barrier layer has been deposited at the connection portion by a reactive sputtering method using a titanium (Ti) target and argon (Ar) + nitrogen (N ₂ ) mixed gas. However, with the miniaturization of semiconductor devices,
The diameter of the wiring connection hole becomes narrower than 0.5 micron, and the ratio of the depth of the connection hole to the diameter of the connection hole (aspect ratio)
As a result, the deterioration of the step coverage of the TiN film due to the reactive sputtering method has become a problem.

When the step coating property is deteriorated, TiN is mainly deposited on the upper part of the hole and is not deposited on the lower part of the fine hole for the electrode, so that a good electrode cannot be formed. For the purpose of avoiding this problem, a collimated sputtering method in which the directionality of sputtered particles is controlled has been developed. However, when the semiconductor device is further miniaturized, the stepped film is formed like the conventional sputtering method. May deteriorate.

In order to solve this problem, a TiN thin film deposition technique by the chemical vapor deposition (CVD) method has been developed. This is a method of growing a TiN thin film on the bottom of a contact hole by utilizing a chemical reaction in the vapor phase and on the substrate surface.
This CVD method is roughly classified into an organic metal CVD (MOCVD) method using an organic metal as a Ti source gas and a chloride method using a chloride. Generally, it is said that the film obtained by the latter chloride method has better step coverage,
For example, as a raw material of Ti, titanium tetrachloride (TiCl
₄ ) Ammonia (NH ₃ ) is used as a nitrogen source, and a TiN thin film is grown by utilizing thermal decomposition and reduction reaction of the source gas on the heated substrate.

However, conventional TiCl ₄ / NH ₃
When a TiN thin film is deposited by a CVD method using a gas system, there arises a problem that chlorine remains in the film. In particular, when TiN is deposited under conditions that allow good deposition on the bottoms of fine connection holes (film forming conditions with good step coverage), a large amount of chlorine of about 10% remains in the film. On the other hand, when the TiN film is deposited under the condition that the chlorine concentration in the film is low, the step coverage deteriorates, and TiN cannot be deposited well on the bottom of the connection hole.

That is, the residual chlorine concentration in the film and the quality of the step coverage are in a contradictory relationship, and it is difficult to satisfactorily deposit a TiN thin film having a low residual chlorine concentration on the bottom of a fine connection hole. The chlorine remaining in the film causes corrosion of the Al wiring after the semiconductor device is manufactured, which causes deterioration of the characteristics of the semiconductor device or deterioration of reliability. For the above reasons, studies have been conducted on the MOCVD method using, as a source gas, an organic metal that does not contain chlorine and does not leave chlorine in the film.

[0009]

However, the MOCVD method is a so-called thermal decomposition method, and in order to properly grow a TiN film on the bottom of a fine connection hole in a semiconductor device, the growth temperature should be lowered and the like. It is necessary to suppress the thermal decomposition of the source gas in the phase and reduce the reactivity of the film-forming species on the surface. This is because the film-forming species generated by the decomposition of the source gas in the gas phase are generally highly reactive and have a large sticking coefficient of the film-forming species to the surface. This is because the reaction probability of the source gas itself on the surface of the substrate increases, so that TiN is deposited only near the entrance of the connection hole.

Ti deposited in high aspect ratio contact holes
When the N film does not have a good surface coating shape, the electrical connection characteristics between the wiring material Al and the substrate or the lower layer wiring are deteriorated or broken after the wiring is formed, which deteriorates the characteristics of the semiconductor device or the device. Cause problems such as non-operation of. On the other hand, if the growth temperature is lowered to obtain good surface coverage, the quality of the formed TiN film deteriorates. in this case,
Even if the coating shape is good, contact resistance rises,
This causes deterioration of the device characteristics due to diffusion of aluminum, which is a wiring material, into the semiconductor substrate due to the deterioration of the barrier property. Therefore, it is strongly required to form a TiN film having a good film quality while realizing a good surface coverage in the contact hole so that a finer semiconductor device in the future can be manufactured.

Therefore, an object of the present invention is to provide a method for forming a barrier metal layer capable of forming a TiN thin layer having good contact hole surface coverage as a film having high barrier properties and low resistance. .

[0012]

To achieve the above object, according to the present invention, an organometallic gas containing Ti and N as constituent elements, or a source gas containing an organometallic gas containing Ti as constituent elements and N. In a method of growing a TiN film by chemical vapor deposition using the above method, a TiN film is formed by supplying a small amount of halogen-based gas at the same time as the supply of an organometallic gas. Provided.

[0013]

As described above, it is difficult for a TiN film deposited by MOCVD using an organic metal as a Ti raw material to have both good surface coverage and good film quality.
This is because the decrease in the reactivity (adhesion probability) of the film-forming species on the surface and the improvement in the film quality cannot be controlled only by the change in the substrate temperature.

In order to solve the above problems, in the present invention, a halogen-based gas such as Cl ₂ is supplied at the same time as the source gas. The supplied Cl ₂ or the like is Ti-- on the surface of the growth layer.
It forms a bond such as Cl and terminates the orbital of Ti that does not contribute to the bond existing on the surface during growth. As a result, the reactivity on the surface is lowered, and the adsorption of the source gas flying to the surface is hindered. Therefore, it becomes possible to effectively reduce the adhesion coefficient of the film-forming species to the surface even at a substrate temperature higher than the conventional one. As a result, it becomes possible to control the film quality and the adhesion coefficient independently, and the above problem is solved.

In the process according to the invention, it is important that chlorine acts only on the surface. This is so that a small amount of chlorine can provide a sufficient effect. As a result, although the halogen gas is added, a large amount of halogen that causes wiring corrosion is prevented from remaining in the film.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. [First Embodiment] FIG. 1 is a schematic diagram showing the structure of a TiN film forming apparatus for carrying out an embodiment of the present invention. As shown in FIG. 1, the substrate 1 is placed in a growth chamber 101.
02 is held by the substrate holding unit 103, and is heated by the substrate heating mechanism 104. A halogen-based gas such as Cl ₂ is supplied through the valve 107, the flow rate is controlled by the mass flow controller 106, and then is supplied onto the substrate 102 through the gas introduction port 105.

The organic metal raw material is the organic metal storage container 108.
Stored inside, this container is heated by the storage container heating mechanism 109. The organometallic raw material is introduced into the vaporizer 112 via the valve 110 and the mass flow controller 111. A carrier gas such as N _{2 is} also used for the valve 114,
It is supplied to the vaporizer 112 via the mass flow controller 113. For nitrogen-based source gases such as NH ₃ , use valve 1
16, and is supplied into the chamber 101 via the mass flow controller 115 and the shower head 117. The organometallic gas vaporized in the vaporizer 112 is also supplied into the chamber 101 via the shower head 117.
The pressure inside the chamber 101 is controlled by a pressure control valve 118 and a vacuum pump 119 that exhausts unnecessary gas.

Since the organometallic raw material for supplying Ti has a low vapor pressure, most of the raw material is liquid at room temperature. Therefore, in this embodiment, the vaporizer 112 using N ₂ as a carrier gas is used, and further, the chamber 101 and the exhaust system are heated by a heater in order to prevent liquefaction of the raw material gas inside the apparatus or in the gas supply system. . In this embodiment, tetradiethylaminotitanium (Ti (N (C ₂ H ₅ ) ₂ ) ₄ : TDEA is used as the TiN source gas.
Only T) was used as a source gas, and a nitrogen-based source gas such as N ₂ was not supplied. Further, HCl was used as the halogen-based gas.

FIG. 2 is a sectional view of the substrate used. A silicon oxide film 202 having a thickness of about 1 μm was deposited on the silicon substrate 201 by the CVD method. A photoresist is applied thereon, and a trench 203 having a width of 0.25 μm and a length of 1 μm is formed by ordinary mask exposure and dry etching.
Was formed. Then, the remaining resist was removed by ashing using oxygen gas.

The substrate 102 was held on the substrate holder 103, the inside of the chamber 101 was evacuated by the vacuum pump 119, and then the substrate temperature was raised to 350 ° C. by the substrate heating mechanism 104. After the substrate temperature became stable, the organic material container 108 was heated by the heating mechanism 109, and the organic material TDEAT was supplied to the substrate surface from the shower head 116 using the mass flow controller 111 and the vaporizer 112. In the present embodiment, the conditions of the mass flow controllers 111 and 113 and the vaporizer 112 are set so that the flow rate of N ₂ which is a carrier gas of TDEAT is 200 sccm and the amount of TDEAT carried thereby is 0.1 g / min. did.

On the other hand, the flow rate of HCl is set to 5 sccm by the mass flow controller 106, and the gas introduction port 105
From inside the chamber 101. Vacuum pump 119
The pressure inside the chamber was maintained at 10 Pa by the pressure control valve 118.

When the other growth conditions are the same and HCl is not added, the step coverage obtained from the surface coating shape is
It was about 0.6. On the other hand, when HCl was added, the step coverage was improved to 0.8. Here, step coverage is defined as the ratio of the film thickness at the bottom of the trench to the TiN film thickness on the surface. However, the growth rate was reduced to about 80% by the addition of HCl. The extent of the step coverage improvement and the growth rate decrease depended on the HCl flow rate and showed the same tendency with respect to the HCl flow rate. From this, the flow rate of HCl is appropriately selected according to the required growth rate and step coverage.

The residual chlorine concentration in the film is measured by SIMS (Seconda
ry Ion Mass Spectrometer (secondary ion mass spectrometer) quantitatively analyzed, but the amount was less than 10 ¹⁷ cm ^−3, which was a small amount, and residual chlorine did not cause wiring corrosion. Although HCl is used as the growth suppressing gas in this embodiment, the same effect can be obtained by using other halogen-based gas such as F ₂ . The point is that the orbital of Ti which is not involved in the bond existing on the growing TiN surface can be terminated by the halogen atom.

[Second Embodiment] In the present embodiment, T
Tetradimethylamino titanium (T
_{i (N (CH 3) 2} ) 4: TDMAT) and using NH ₃ gas. Cl ₂ was used as the halogen-based gas. The apparatus used and the substrate structure used are those in Example 1.
It is similar to that shown in FIGS. 1 and 2 shown in FIG. In this example, NH ₃ was supplied as a nitrogen source in addition to the Ti source.

The substrate 102 was set on the substrate holder 103, and the inside of the chamber 101 was evacuated by the vacuum pump 119. After that, the substrate is heated to 450 by the substrate heating mechanism 104.
Heated to ° C. After the substrate temperature is stabilized, NH ₃ is supplied by the mass flow controller 115, and the pressure inside the chamber 101 at that time is adjusted to 300 Pa which is a growth pressure by using the pressure adjusting valve 118 and the vacuum pump 119.
Maintained at. Then, TDMAT was supplied from the mass flow controller 111. In this example, the organometallic storage container 108 was heated by the storage container heating mechanism 109 to supply TDMAT, and the vaporizer 112 was not used.

However, in order to prevent the liquefaction of the organic raw material inside the piping and the inside of the apparatus, the chamber and the exhaust system were heated by the heater as in the case of the first embodiment. Each gas flow rate is TDMAT flow rate 20 scc
m, NH ₃ flow rate 300 sccm, Cl ₂ flow rate 5 sccm
And

As in the case of the first embodiment, the step coverage could be improved by about 30% by adding Cl ₂ gas. However, the growth rate is Cl
_It was reduced by about 20% by adding ₂ gases. However, by supplying NH ₃ , the improvement of the film quality, specifically the improvement of the barrier property and the stabilization of the quality of the TiN film after the film formation were realized.

The above-mentioned effect is obtained by using halogen atoms or molecules such as chlorine for the orbits which do not contribute to the bonding of Ti on the growth surface, regardless of the type of the organic metal which is the source gas of Ti and the type of the source gas of nitrogen. It is obtained by terminating. However, the terminated surface has a decreased reactivity, which causes a decrease in the growth rate. Therefore, it is necessary to appropriately determine the type and flow rate of the halogen-based gas according to the required step coverage, film quality, and growth rate.

The raw material gas has different reactivity on the surface depending on its type. Therefore, the type of gas and the flow rate of each gas are determined in accordance with the degree of permissible decrease in the growth rate and the required degree of step coverage.

[0030]

As described above, Ti according to the present invention
The method of forming the N film is to use a MOCVD method using an organic metal source gas containing Ti and supply a halogen-based gas such as Cl ₂ in addition to the source gas system, so that even if the substrate temperature is raised. The growth rate is suppressed low, and it becomes possible to control the growth mainly by the reaction rate on the surface. Therefore, according to the present invention, it is possible to form a TiN thin film having excellent step coverage in the connection hole and excellent film quality such as barrier property.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a metal-organic vapor phase epitaxy apparatus used in Examples of the present invention.

FIG. 2 is a sectional view of a substrate for explaining an embodiment of the present invention.

[Explanation of symbols]

101 Chamber 102 Substrate 103 Substrate Holding Unit 104 Substrate Heating Mechanism 105 Gas Inlet 106, 111, 113, 115 Mass Flow Controller 107, 110, 114, 116 Valve 108 Organic Metal Storage Container 109 Storage Container Heating Mechanism 112 Vaporizer 117 Showerhead 118 Pressure adjusting valve 119 Vacuum pump 201 Silicon substrate 202 Silicon oxide film 203 Trench

Claims (4)

[Claims] 1. A method of growing a TiN film by a chemical vapor deposition method using an organometallic gas containing Ti and N as constituent elements or an organometallic gas containing Ti as constituent elements and a source gas containing N. At the same time as the organometallic gas supply, a small amount of halogen-based gas
A method for forming a TiN film, which comprises depositing N. 2. The organometallic gas containing Ti and N as constituent elements or the organometallic gas containing Ti as constituent elements is Ti (N (CH ₃ ) ₂ ) ₄ , Ti (N
(C ₂ H ₅ ) ₂ ) ₄ , Ti (C ₂ H ₅ ) ₂ (N ₃ ) ₂ ,
The method for forming a TiN film according to claim 1, wherein the TiN film is a mixed gas of one or more kinds of Ti (C ₂ H ₅ ) ₂ (N (CH ₃ ) ₂ ) ₂ gas. 3. The source gas containing N is N ₂ , NH
_{3. The} method for forming a TiN film according to claim 1, wherein the mixed gas of one or a plurality of N ₃ and N ₂ H ₄ gases is used. 4. The halogen-based gas is Cl ₂ , HCl,
The method for forming a TiN film according to claim 1, wherein the TiN film is a mixed gas of one or more kinds of F ₂ and HF gas.