JP2832991B2 - Multilayer wiring forming method and continuous processing apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a multilayer wiring in a semiconductor device manufacturing process and a continuous processing apparatus.

[Summary of the Invention]

The present invention relates to a method for forming a multilayer wiring and a continuous processing apparatus in a manufacturing process of a semiconductor device, and more specifically, to irradiate ultraviolet rays to a bottom of a connection hole in a reducing atmosphere,
Next, the present invention relates to a multilayer wiring forming method for continuously embedding a conductive material inside the connection, and a continuous processing apparatus for enabling the multilayer wiring forming method.

[Conventional technology]

With the increase in the degree of integration and speed of semiconductor devices such as LSIs, the importance of multilayer wiring formation technology is increasing. In particular, the aspect ratio of the connection hole, that is, the ratio of the depth to the diameter is increasing to, for example, 1 or more, and the technique of reliably embedding a conductive material into the connection hole is increasing in importance.

Conventionally, as a method of embedding a conductive material inside a connection hole opened in an interlayer insulating film on a substrate such as a semiconductor, a selective CV
D, blanket CVD, a method by sputtering, and the like are used. Further, as the conductive material used for embedding, aluminum (A1) or an alloy thereof, a high melting point metal such as tungsten (W), a silicide thereof, and polysilicon (p-Si) are used.

When embedding these conductive materials into connection holes opened in an interlayer insulating film on a semiconductor substrate such as Si, it is extremely important to effectively clean the surface of the substrate exposed at the bottom of the connection holes. The main reason is that Si is a substance that is very easily oxidized, so it is difficult to remove the natural oxide film on the substrate surface. A new natural oxide film is formed as soon as the substrate is exposed to the air. If a conductive material is buried inside the connection while the removal of the natural oxide film is incomplete, the contact resistance may increase, or an ohmic contact may not be obtained, which may adversely affect device characteristics.
Further, in the embedding by the selective CVD, the self-aligned selective growth is incomplete, and in some cases, the selective growth is not performed at all.

Therefore, conventionally, a natural oxide film has been removed by performing plasma cleaning with argon (Ar) or the like on a substrate in a deposition chamber of a conductive material, or by performing high-temperature high-vacuum baking, and thereafter, a continuous conductive film is formed. Methods of embedding conductive materials have been performed. Further, in the method by selective CVD, there is known a conventional technique of irradiating a substrate with light having a wavelength of 200 to 1000 nm in a reactive gas atmosphere to form an intermediate product having good adhesion and solving the above problem. (See JP-A-61-274345).

[Problems to be solved by the invention]

In the above-described conventional method of forming a multilayer wiring, there are practical problems such as damage to the substrate by plasma, contamination from metal in the furnace, and high-temperature baking at, for example, 800 ° C. or more. In addition, even if an intermediate product having good adhesion is formed, satisfactory results cannot always be obtained from the viewpoint of removing a natural oxide film.

Accordingly, an object of the present invention is to form a multilayer wiring by embedding a conductive material in a connection hole opened in an interlayer insulating film on a substrate such as a semiconductor, and to effect a natural oxide film on the substrate surface exposed at the bottom of the connection hole. It is an object of the present invention to provide a method and an apparatus for forming a multilayer wiring having a low and ohmic contact resistance by removing the conductive material and continuously burying a conductive material therein. In addition, it is another object of the present invention to provide a method and an apparatus for forming a multi-layer wiring capable of performing good selective growth when the conductive material is buried by selective CVD.

[Means for solving the problem]

In order to achieve the above-mentioned object, the method for forming a multilayer wiring according to the present invention, when embedding a conductive material inside a connection hole opened in an interlayer insulating film on a substrate such as a semiconductor, firstly, in a reducing atmosphere, at the bottom of the connection hole. UV irradiation,
Then, a conductive material is continuously embedded in the inside of the connection hole. The term continuous, as used herein, means that the substrate is not exposed to the atmosphere. The term “reducing atmosphere” refers to hydrogen (H ₂ ) or deuterium (D ₂ ) gas, and ultraviolet irradiation refers to irradiation of light having a wavelength of 400 nm or less. It doesn't matter. The light source is not particularly limited, and has a function of reducing a natural oxide film on a substrate, such as a low-pressure mercury lamp, a deuterium lamp, and an excimer laser such as ArF.
It is possible to arbitrarily select a light source within a range that can achieve the object of the present invention. The conductive material deposition method for embedding the conductive material inside the connection hole is not particularly limited, and any method such as selective CVD, blanket CVD, or sputtering may be used for the purpose.

Further, the continuous processing apparatus according to the present invention is an apparatus that includes an ultraviolet irradiation device and a conductive material deposition device that enable the above-described multilayer wiring forming method. Here, the ultraviolet irradiation device has a function of irradiating the substrate with the light source and has an explosion-proof chamber capable of using the reducing atmosphere. The conductive material deposition apparatus is not particularly limited, and any apparatus that can achieve the object of the present invention, such as selective CVD, blanket CVD, and sputtering, can be used. When the chamber of the ultraviolet irradiation device and the chamber of the conductive material deposition device are provided separately, the two devices are connected by, for example, a gate valve that can move between the two devices without exposing the substrate to the atmosphere. To be configured. Of course, it is also possible to adopt a configuration in which one chamber has the functions of both devices.

[Operation] The natural oxide film formed on the surface of the semiconductor substrate such as silicon exposed at the bottom of the connection hole is reduced and removed by performing ultraviolet irradiation in a reducing atmosphere, for example, as in the following formula. Has improved selectivity and enables reliable selective growth.

SiO ₂ + 2H ₂ → Si + 2H ₂ O SiO ₂ + H ₂ → SiO + H ₂ O SiO + H ₂ → Si + H ₂ O At the same time, only the outermost surface of the semiconductor substrate such as silicon exposed at the bottom of the connection hole is heated, effectively activating the dopant. As the process proceeds, a multilayer wiring having a small contact resistance value and an ohmic contact can be obtained in addition to the effect of removing the natural oxide film.

The multilayer wiring forming apparatus according to the present invention is configured such that the chamber of the ultraviolet irradiation apparatus and the chamber of the conductive material deposition apparatus are connected by, for example, a gate valve,
Alternatively, both devices are integrally formed, and a conductive material is deposited without exposing a substrate such as a semiconductor to the atmosphere, in other words, without forming a natural oxide film on the surface of the substrate appearing at the bottom of the connection hole. To make things possible.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic sectional view of a continuous processing apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an ultraviolet irradiation device, and a semiconductor substrate 2 such as Si is mounted on a first susceptor 3 in a chamber of the ultraviolet irradiation device 1. The ultraviolet light of 193 nm from the ArF excimer laser 4 is arranged to irradiate the substrate 2 through an ultraviolet irradiation window 5 made of, for example, synthetic quartz. H ₂ gas is introduced from the reducing gas introduction hole 6 and exhausted from the first exhaust hole 7 by a vacuum pump (not shown), and the inside of the chamber of the ultraviolet irradiation device 1 is kept at a reduced reducing atmosphere of a constant pressure. With this configuration, an explosion-proof ultraviolet irradiation device can be constructed.

Reference numeral 11 denotes a conductive material deposition apparatus, which is an apparatus for performing selective CVD in this embodiment. The base 2 is configured to be able to be transferred between the two devices by a transfer means (not shown) through, for example, a gate valve 10 without being exposed to the atmosphere. The substrate 2 transferred from the ultraviolet irradiation device 1 is placed on the second susceptor 12, and the reaction gas introduced from the reaction gas introduction hole 13 is supplied from the second exhaust hole 14 by a vacuum pump (not shown). The inside of the chamber of the conductive material deposition apparatus 11 is evacuated and kept at a reduced pressure and a constant pressure of a reaction gas atmosphere.

The base 2 includes a first susceptor 3 and a second susceptor 12.
It is possible to raise the temperature to an arbitrary temperature as needed by a heating means such as a heater inside.

In the continuous processing apparatus configured as described above, in the present embodiment, a method of forming a multilayer wiring in which connection holes are buried by selective CVD of tungsten (W) will be described.

3 (a) to 3 (c) are process diagrams showing a method for forming a multilayer wiring according to an embodiment of the present invention. In FIG.
A connection hole 23 is opened in an insulating film 21 such as SiO ₂ on the base 2 which is a p ⁺ -Si semiconductor into which boron (B) is implanted as a dopant. Usually, when the substrate 2 is pretreated by wet etching with hydrogen fluoride (HF) water or the like and then washed with pure water, or when the substrate 2 is exposed to the atmosphere, the substrate appearing at the bottom of the connection hole 23 is exposed. On the two surfaces, a natural oxide film 22 grows slightly. Therefore, the substrate 2 is placed on the first susceptor 3 of the ultraviolet irradiation device 1, H ₂ gas is introduced through the reducing gas introduction hole 6, and the H ₂ gas is exhausted under reduced pressure through the first exhaust hole 7. The inside of the first chamber is kept in a reducing atmosphere reduced to, for example, 10 Torr. Then ArF
193 nm ultraviolet rays 24 from the excimer laser 4 are applied stepwise to the entire surface of the substrate 2 through the ultraviolet radiation window 5 as shown in FIG. The irradiation conditions at this time were a pulse energy of 50 mJ / pulse, a repetition frequency of 10 Hz, and a pulse width of 10 ns.

By the irradiation of the ultraviolet rays, the natural oxide film 22 is reduced and removed, and the temperature of only the outermost surface of the base 2 is increased to activate the dopant. Activation of the dopant in this case, the carrier concentration of the surface is achieved 10 ²⁰ cm ^-3 or more, this value is larger than the value obtained in an electric furnace annealing at about 900 ° C., of W to p ⁺ -Si This sufficiently cleared the barrier height φ _Bp = 0.67 eV.

Next, the substrate 2 which has been irradiated with the ultraviolet rays is not exposed to the atmosphere, and is exposed through the gate valve 10 to a conductive material deposition apparatus.
11 and is placed on the second susceptor 12. Tungsten hexafluoride (WF)
₆₎ The 10 _sccm, silane _{(SiH 4) 6S SCCm, H} 2 to 1000 _SCCM
And the pressure in the chamber of the conductive material deposition apparatus 11 is maintained at 0.2 Torr. Next, the base 2 is heated to, for example, 260 ° C. by a heater in the susceptor 12. As described above, as shown in FIG. 3 (c), the conductive material 25 made of W was selectively grown and embedded in the connection hole 23. By embedding the conductive material 25, it was possible to form a multilayer wiring having a small contact resistance value and excellent ohmic properties.

Embodiment 2 FIG. 2 is a schematic sectional view of a continuous processing apparatus according to a second embodiment of the present invention. In this figure, parts having the same functions as those in the first embodiment are given the same names and numbers as those used in FIG. In this embodiment, a case where the ultraviolet irradiation device 1 and the conductive material deposition device 11 share the same chamber will be described.

Reference numeral 15 denotes a deuterium lamp which emits continuous spectrum ultraviolet light having a wavelength of 400 nm or less, for example, an ultraviolet irradiation window 5 made of synthetic quartz.
Are arranged so as to irradiate the substrate 2 on the third susceptor 9 via the. The base 2 is, for example, a third susceptor 9
It is configured such that the temperature can be raised to an arbitrary temperature by a heater built in the device. The pressure in the chamber is maintained at a constant value reduced by a vacuum pump (not shown) through the third exhaust hole 8. With this configuration, an explosion-proof ultraviolet irradiation device can be constructed.

In the present embodiment, a method for forming a multilayer wiring in which connection holes are buried by selective CVD of polysilicon (p-Si) in the continuous processing apparatus configured as described above will be described with reference to FIG.

In FIG. 1A, a substrate 2 made of a semiconductor such as Si
A connection hole 23 is opened in the insulating film 21 such as SiO ₂ . The natural oxide film 22 is slightly left on the surface of the base 2 appearing at the bottom of the connection hole 23. The substrate 2 is placed on the third susceptor 9 in the chamber, and while the temperature is raised to, for example, 600 ° C., deuterium (D ₂ ) gas is introduced from the reducing gas introduction hole 6, and the third exhaust hole 8 is formed. The chamber is further evacuated to a reduced pressure, and the inside of the chamber is kept in a reducing atmosphere reduced to, for example, 50 Torr. Next, the ultraviolet light 24 of the deuterium lamp 15 is applied through the ultraviolet irradiation window 5 to the substrate 2.
The entire surface is uniformly irradiated as shown in FIG. 3 (b). The output of the deuterium lamp 15 was, for example, 150 W. By this irradiation, deuterium in the chamber is excited, and the natural oxide film 22 on the surface of the base 2 which appears at the bottom of the connection hole 23 is reduced and removed as in the following equation.

SiO ₂ + 2D ₂ → Si + 2D ₂ O SiO ₂ + D ₂ → SiO + D ₂ O SiO + D ₂ → Si + D ₂ O Next, the substrate 2 which has been irradiated with ultraviolet rays is placed on the susceptor 9 in the same chamber and kept at 600 ° C. The dichlorosilane (SiH ₂ Cl ₂ ) 100
_sccm and introducing a mixed gas of hydrogen chloride (HCl) 10 _sccm and H ₂ 1000 _sccm, maintaining the pressure in the chamber to 100Torr to evacuated by the third vacuum pump unshown the exhaust hole of the.
As described above, the p-
The conductive material 25 of Si was selectively grown in a self-aligned manner, and was buried. Thereafter, depending on the purpose, N-type or P-type impurity ions such as boron difluoride ion (BF ₂ ⁺ ) or phosphorus ion (P ⁺ ) are implanted, and an activation heat treatment is further applied to reduce the contact resistance value. This makes it possible to form a multilayer wiring that is small and has excellent ohmic properties.

Although the detailed description of the embodiment of the present invention has been added,
The purpose of the present invention is to embed a conductive material inside a connection hole opened in an interlayer insulating film on a substrate such as a semiconductor, first irradiate the bottom of the connection hole with ultraviolet rays in a reducing atmosphere, and then continuously. It is characterized in that a conductive material is embedded inside the connection. Therefore, the light source for ultraviolet irradiation is KrF (248n) in addition to the above.
m), 400 nm, excimer laser using gaseous medium such as XeCl (308 nm), low-pressure mercury lamp, xenon arc lamp, etc.
Irradiation with light having the following wavelengths, which can exert the effects of the present invention, can be arbitrarily used.

As the conductive material deposition apparatus, the selective CVD described above is used.
The device is the most effective because it can improve the self-selective selectivity. However, the present invention is not limited to this apparatus, and an apparatus for performing blanket CVD, a sputtering apparatus, a vapor deposition apparatus, and the like can be used. When these non-selective deposition devices are used, it goes without saying that the wiring pattern near the connection hole is left by using etch-back together.

In the above two embodiments, the heater incorporated in the susceptor was used as a method for raising the temperature of the base 2, but this is not particularly limited, and a halogen lamp, high-frequency heating, or the like can be used.

For the conductive material embedded in the connection hole, W
And p-Si, as well as refractory metals such as Mo and aluminum (A
l), Al alloy, copper (Cu) and the like can be used according to the purpose, and it is possible to form a multilayer wiring having low and ohmic contact resistance with all of these materials.

〔The invention's effect〕

As described above in detail, the method for forming a multilayer wiring according to the present invention, when burying a conductive material in a connection hole opened in an interlayer insulating film on a substrate such as a semiconductor, firstly places an ultraviolet ray on the bottom of the connection hole in a reducing atmosphere. By irradiating and then continuously burying a conductive material inside the connection hole, a multilayer wiring having a small contact resistance and an ohmic contact becomes possible, and the device characteristics of the semiconductor device are improved and stabilized. . Further, according to the continuous processing apparatus of the present invention, since the ultraviolet irradiation and the deposition of the conductive material can be continuously performed, the multilayer wiring having the above-mentioned characteristics can be implemented reliably and with good reproducibility. In particular, if a selective CVD apparatus is used as the conductive material deposition apparatus, the self-aligned selectivity can be improved, which is more effective. As described above, in embedding the conductive material in the connection hole,
Multilayer wiring with excellent reliability, which has not been solved by the conventional method and apparatus, becomes possible, and the contribution to the semiconductor device manufacturing process is great.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a continuous processing apparatus according to a first embodiment of the present invention, FIG. 2 is a schematic sectional view of a continuous processing apparatus according to a second embodiment of the present invention, and FIGS. (C) is a view showing a step of the method for forming a multilayer wiring according to the embodiment of the present invention; DESCRIPTION OF SYMBOLS 1 ... Ultraviolet irradiation apparatus 2 ... Substrate 4 ... Excimer laser 5 ... Ultraviolet irradiation window 10 ... Gate valve 11 ... Conductive material deposition apparatus 15 ... Deuterium lamp 21 ... Interlayer insulating film 22 ... Natural Oxide film 23 Connection hole 24 UV 25 Conductive material

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 21/28-21/288 H01L 21/3205 H01L 21/3213 H01L 21/44-21/445 H01L 21/768 H01L 29 / 40-29/51

Claims (4)

(57) [Claims] An ultraviolet irradiation is performed in a reducing atmosphere on a bottom of a connection hole on a semiconductor substrate into which an impurity has been ion-implanted, thereby removing a natural oxide film on the bottom of the connection hole and activating the impurity. Wherein a conductive material is embedded in the connection hole. 2. A chamber for accommodating a substrate to be processed, reducing gas introducing means for reducing the inside of the chamber to a reducing atmosphere,
An explosion-proof type having an ultraviolet irradiation window made of synthetic quartz formed on the wall surface of the chamber, and an ultraviolet light source disposed outside the chamber and irradiating the substrate to be processed with ultraviolet light through the ultraviolet irradiation window. 2. A continuous processing apparatus for performing the multilayer wiring forming method according to claim 1, further comprising: an ultraviolet irradiation apparatus according to claim 1; and a conductive material deposition apparatus. 3. A bottom portion of the connection hole on the substrate is irradiated with deuterium lamp light in a deuterium atmosphere to excite the deuterium, thereby removing a natural oxide film at the bottom portion of the connection hole. A method for forming a multilayer wiring, comprising: burying a conductive material in the connection hole. 4. A chamber for accommodating a substrate to be processed, a deuterium gas introducing means for setting a deuterium atmosphere in the chamber,
An explosion-proof having an ultraviolet irradiation window made of synthetic quartz formed on a wall surface of the chamber, and a deuterium lamp disposed outside the chamber and irradiating the substrate to be processed with ultraviolet light through the ultraviolet irradiation window. 4. A continuous processing apparatus for performing the multilayer wiring forming method according to claim 3, further comprising a mold type ultraviolet irradiation apparatus and a conductive material deposition apparatus.