JPH0464223A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce contact resistance by supplying both a reaction gas and a carrier gas, chemically vapor-growing a second W layer on the surface of a first W layer, stopping the supply of the reaction gas so as to externally diffuse fluorine and continuing the feed of the carrier gas. CONSTITUTION:A reaction gas mixed with a carrier gas, WF6 and SiH4, in the growth process of W are fed intermittently. F contained in a first W layer grown at a first supply timing before a first stopping timing is diffused externally and washed away by the carrier gas not stopped at the first stopping timing when WF6 and SiH4 are not supplied. A novel second W layer is laminated and grown on the first W layer, from which F is removed, at a second supply timing, and F contained in the anew grown second W layer is diffused externally and washed away by the carrier gas and taken off. The process of growth and F removal is repeated, thus forming a buried W layer having specified thickness.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Field of Application Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems Action Embodiment 1 Process configuration diagram of the embodiment (Fig. 1) Process sectional view of application example 1 (Fig. 2) Process sectional view of second application example (Fig. 3) Effects of the invention [Summary] A method for manufacturing a semiconductor device, especially in a contact hole or a through hole of an insulating film. Regarding the chemical vapor deposition method when embedding a tungsten layer in a tungsten layer, the tungsten layer is embedded in a high aspect ratio opening exposing a conductive substrate at the bottom by a chemical vapor deposition method using a ridge and SiH4 as a reactive gas. When forming the layer, the purpose of reducing the concentration (content) of F contained in the buried W layer and reducing the contact resistance of the buried W layer to the conductive substrate is to reduce the concentration (content) of F contained in the buried W layer. When a tungsten layer is grown in a chemical vapor phase on a conductive substrate to be produced in a mixed gas of tungsten hexafluoride and monosilane, which are reactive gases, and a carrier gas, the reactive gas is grown in the process of growing the tungsten layer. A tungsten layer of a predetermined thickness is formed by alternately repeating the supply of a growth gas consisting of a mixed gas of tungsten hexafluoride and monosilane, which are reactive gases, and a carrier gas, and evacuation. It has a structure that allows it to grow.

[Industrial Field of Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a chemical vapor deposition method for embedding a tungsten layer in a contact hole or a through hole of an insulating film.

As semiconductor devices become more highly integrated, the diameters of contact holes and through holes formed in insulating films have become extremely fine, and their aspect ratios have also increased to 1 or more. In such a situation, when forming a metal wiring layer, the thickness of the metal wiring layer at the stepped portion of the contact hole or through hole becomes extremely thick due to poor step coverage of the metal layer formed by PVD method such as sputtering. There is a problem in that the wire becomes thinner and more likely to break due to electromigration or stress migration that occurs in that portion. In addition, in a structure in which an ordinary aluminum (Af) wiring layer is in direct contact with the Si surface, there is a problem of junction breakdown due to Si wicking during heat treatment, and in order to prevent this, S
In the A2 wiring layer to which a small amount of i is added, there is a problem in that the contact resistance increases due to the precipitation of P-type Si on the contact surface.

Therefore, as a means to reduce the level difference in the contact hole and prevent disconnection of the wiring layer, as well as to prevent the junction breakdown and increase in contact resistance, A.
A method of embedding a thick tungsten (W) layer interposed between the f-wiring layer and the f-wiring layer is attracting attention.

[Prior Art] A method for easily embedding a thick W layer in the contact hole is, for example, a selective vapor phase growth method of W.

In the conventional selective chemical vapor deposition (cVD) method of W,
A substrate to be grown that has been heated to a predetermined growth temperature by heating with a lamp or the like is placed in a sealed container that is evacuated to a vacuum, and a reactive gas such as tungsten hexafluoride (WF
6) 5SCCM and monosilane (SiH4) 3
SCCM is mixed with carrier gas hydrogen (H,) 100 ~
1000 SCCM, and while maintaining the inside of the sealed container at a predetermined pressure of Q, 3 Torr, for example, S is exposed in the contact hole of the insulating film on the substrate to be grown.
A W layer was selectively grown on the i-plane, and during the growth process, the reactant gases -F6 and SiH4 were supplied at the above-mentioned flow rates, and the growth was continued to a predetermined thickness.

[Problem to be solved by the invention]

However, with this method, as mentioned above, in the current situation where semiconductor devices have become highly integrated and the aspect ratio of contact holes has increased, a large amount of fluorine (F) is mixed into the W layer that grows in the contact holes. exists near the interface between the W layer and the substrate Si, causing a problem of increasing contact resistance between the buried W layer and the substrate St.

Therefore, the present invention aims at reducing the F concentration (content) in the buried W layer when chemically vapor-depositing the buried W layer in the opening with a high aspect ratio using -F6 and 5iHa as the reaction gas. The purpose is to reduce the contact resistance to the conductive substrate exposed at the bottom of the opening in the W layer.

[Means to solve the problem]

The above-mentioned problems are as follows: (1) selectively chemically vaporize the tungsten layer on the conductive substrate exposed in the openings of the insulating film in a mixed gas of tungsten hexafluoride and monosilane, which are reactive gases, and a carrier gas; Upon phase growth, (a)
supplying the reaction gas and the carrier gas together,
a step of chemical vapor deposition of a first tungsten layer on the surface of the conductive substrate, and then (b) fluorine incorporated into the first tungsten layer from the reaction gas in step (a); stopping the supply of the reaction gas and continuing the supply of the carrier gas so as to diffuse outward from the first tungsten layer, and then (c) the reaction gas;
and a carrier gas to chemically vapor-deposit a second tungsten layer on the surface of the first tungsten layer; so that fluorine taken into the second tungsten layer diffuses outward from the second tungsten layer,
and a step of stopping the supply of the reaction gas and continuing the supply of the carrier gas, and in the step (a), the thickness of the first tungsten layer is adjusted to the fluorine contained in the first tungsten layer. is formed to a thickness that substantially completely outdiffuses in the step (b), and in the step (c), the thickness of the second tungsten layer is reduced to a thickness that is included in the second tungsten layer. A method for manufacturing a semiconductor device according to the present invention, in which fluorine is formed to a thickness such that fluorine is almost completely diffused out in the step (d);
Alternatively, on the conductive substrate exposed in the opening of the insulating film,
When a tungsten layer is selectively grown in a chemical vapor phase in a mixed gas of tungsten hexafluoride and monosilane, which are reactive gases, and a carrier gas, (a) the reactive gas and the carrier gas are both supplied; a step of chemical vapor deposition of a first tungsten layer on the surface of the conductive substrate; (c) supplying both the reaction gas and the carrier gas so as to diffuse outward from the first tungsten layer, stopping the supply of the reaction gas and the carrier gas and performing vacuum evacuation; (d) depositing a second tungsten layer on the surface of the first tungsten layer in a chemical vapor phase;
stopping the supply of the reaction gas and carrier gas and performing vacuum evacuation so that the fluorine incorporated into the second tungsten layer diffuses outward from the second tungsten layer; In (a), the first tungsten layer is formed to a thickness such that fluorine contained in the first tungsten layer is almost completely out-diffused in the step (b), and In the step (c), the second tungsten layer is formed to a thickness such that fluorine contained in the second tungsten layer is almost completely out-diffused in the step (d). The problem is solved by a method of manufacturing a semiconductor device according to the present invention.

[For production]

In the buried W layer, the concentration of F contained in the W layer is 2 to 3.
It has been confirmed that if the contact resistance increases by a factor of 2 to 3, the contact resistance also increases by 2 to 3 times.

Therefore, in order to reduce the F concentration in the buried W layer, in the first method according to the present invention, a reactive gas, i.e., -
By intermittently supplying F and SiH4, WF and S
At the first stop timing when iH4 is not supplied, the first W grown at the previous first supply timing
After the F contained in the layer is diffused outward and washed away by a carrier gas that is not stopped, a new second W layer is grown on top of the first W layer from which the F has been removed at the next second supply timing. Then, at the next second stop timing, the newly grown second supply timing mainly occurs at the previous second supply timing.
The F contained in the W layer is diffused outward and washed away with a carrier gas. Then, the above-mentioned growth and F removal steps are repeated to form a buried W layer having a predetermined thickness by the sum of multiple W layers that are grown at multiple supply timings and the OF in the grown layers is removed at the next stop timing. is formed.

Furthermore, in the second method according to the present invention, during the W growth process, the timing of supplying a growth gas consisting of a carrier gas and the reaction gas, and the timing of stopping the growth gas to create a vacuum atmosphere around the substrate to be grown are determined. Evacuation timing is provided alternately, and after the F contained in the first W layer grown at the first supply timing is suctioned and removed at the next first evacuation timing, at the next second supply timing. A second W layer is laminated and grown on the first W layer, and a buried W layer having a predetermined thickness is formed by the sum of the W layers grown at multiple reaction gas supply timings.

As described above, according to the method of the present invention, the F concentration in the buried W layer can be reduced to about 1/2 compared to the conventional method.

〔Example〕

The present invention will be specifically explained below with reference to illustrated embodiments.

FIG. 1 is a process configuration diagram of an embodiment of the selective vapor phase growth method for W according to the present invention, in which (a) is a temperature profile diagram; (a) is a temperature profile diagram;
b) is a flow sequence diagram of the reaction gas, FIG. 2 is a process cross-sectional view of the first application example of the W selective vapor phase growth method according to the present invention, and the third is a process cross-sectional view of the second application example. It is.

Identical objects are indicated by the same reference numerals throughout the figures.

In one embodiment of the first selective chemical vapor deposition method for a W layer according to the present invention, the growth temperature was set at 360°C, as shown in FIG. 1(a).

In addition, the flow rate of 1Fh, which is a reactive gas, is 20 SCCM,
The flow rate of SiH4 was 15 SCCM, the flow rate of Hz as carrier gas was 1000 SCCM, and the growth pressure was 0.
It was set at 1 to 0.3 Torr.

As shown in (b) of the same figure, growth started one minute after the temperature of the growth substrate reached 360°C, and the carrier gas H2 was kept flowing at the above flow rate. The supply of the reaction gas at the above flow rate of ridge and 5in4 is divided into four supply timings A+-Az, A3, and A4 of 15 seconds each, and is intermittent. and during each supply timing, each 30
Growth was performed by setting stop timings Bls Bz and B3 for stopping only the supply of the reaction gas for 2 seconds, and the total thickness was 2.
000 buried W layers were grown.

Table 1 Table 1 shows the F concentration in the embedded W layer formed by intermittent supply of reactive gas in the above embodiment and in the embedded W layer formed by the conventional method in which reactive gas was continuously supplied using SIMS (secondary ion mass). This shows the results of a qualitative comparison using This result shows that the selective chemical vapor deposition according to the present invention was able to reduce the F concentration in the buried W layer to nearly 1/2 compared to the conventional method.

Further, in an embodiment of the second selective chemical vapor deposition method for a W layer according to the present invention, the growth temperature is set at 360°C, and the flow rate of F6, which is a reactant gas, is set at 20 SC.
The flow rates of CM and Sign were set to 15 SCCM, the flow rate of H2 as a carrier gas was set to 1000 SCCM, and the growth pressure was set to 0.1 to 0.3 Torr.

Although not shown, growth starts one minute after the temperature of the growth substrate reaches 360°C, and the reaction gas WF
The growth gas containing & and SiH4 and H2 as a carrier gas is supplied at the above flow rate at the first, second, third, and fourth supply timings of several seconds to one minute each, for example, 15 seconds. This is done intermittently by dividing into 30 seconds to 1 minute between each supply timing, for example, stopping the supply of growth gas for 30 seconds and evacuating the inside of the growth container to a vacuum of about 10-'Torr. Growth was performed by setting evacuation timing and alternately combining growth gas supply and evacuation to grow a buried W layer with a total thickness of 2000 layers as in the previous example.

The F concentration in the buried W layer grown by this method also shows approximately the same value as in the previous example.

The selective chemical vapor deposition method for a buried W layer according to the present invention is applied to, for example, phosphosilicate glass (PSG) provided on a Si substrate 1, as shown in the process cross-sectional view of FIG. 2, when manufacturing a semiconductor device. ) is formed in the glabella insulating film 2 with a thickness of about 0.3 μm, for example, in a contact hole 3 with a diameter of about 0.3 μm (aspect ratio=1), and in contact with the surface of the Si substrate exposed at the bottom of the contact hole 3. In addition, a buried W layer 4 is formed to reduce the step difference in the contact hole 3, thereby improving the coverage of, for example, an Affi wiring layer 5 that will be formed on the contact hole 3 later as shown by a chain line, and improving the coverage of the Affi wiring layer 5, which will be formed later on the contact hole 3. This is used to prevent disconnections in the wiring layer due to differences in level.

Furthermore, the method of selective chemical vapor deposition of a buried W layer according to the present invention, as shown in the cross-sectional view of the process in FIG. Lower layer AI exposed on the bottom surface of the through hole 8 in the deep through hole (interlayer contact hole) 8 with an aspect ratio of about 1! , a buried W layer 4 is formed which contacts the wiring layer 6 and reduces the level difference formed in the through hole 8, and as shown by the chain line, the upper layer A1 wiring layer 9 formed over the through hole 8 is formed. It is also applied to improve coverage and prevent disconnections in upper wiring layers due to differences in level in through holes.

Note that the selective chemical vapor deposition method for W according to the present invention can of course be applied to growing a buried W layer in a contact hole or through hole on a conductive substrate other than Si or A1 as shown in the application example above. be done.

Although the present invention has been described above with reference to an embodiment of selective vapor phase growth, the W vapor phase growth method according to the present invention can also be applied to a normal non-selective chemical vapor growth method, and the same effects will be produced.

[Effects of the Invention] As explained above, according to the present invention, a step is formed in the contact hole or through hole in order to reduce the level difference in the contact hole or through hole and prevent disconnection of the upper wiring layer at that part. The concentration of fluorine in the buried tungsten layer formed can be reduced to about 1/2 compared to the conventional method, and the contact resistance to the underlying conductive substrate can be reduced to about 1/2 compared to the conventional method. .

Therefore, the present invention has a great effect on improving the performance and reliability of highly integrated semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a process configuration diagram of an embodiment of the W vapor phase growth method according to the present invention, in which (a) is a temperature profile diagram, (b) is a flow sequence diagram of a reaction gas, and FIG. 2 is a process diagram according to an embodiment of the present invention. FIG. 3 is a process cross-sectional view of a first application example of the W vapor phase growth method. FIG. 3 is a process cross-sectional view of a second application example of the W vapor phase growth method according to the present invention. In the figure, A8, A2, A3, and A4 are the reaction gas supply timings,
B1, B2, B3 are reaction gas stop timings, 1 is S
An i-substrate, 2.7 is an interlayer insulating film, 3 is a contact hole, 4 is a buried W layer, 5 is an A1 wiring layer, 6 is a lower Al wiring layer, 8 is a through hole, and 9 is an upper A2 wiring layer. Me 2 Figure Atsushi Hayabusa 3 Figure

Claims (2)

[Claims] (1) When selectively chemical vapor growing a tungsten layer on the conductive substrate exposed in the opening of the insulating film in a mixed gas of tungsten hexafluoride as a reactive gas and monosilane and a carrier gas. (a) supplying the reactive gas and the carrier gas together to chemically vapor deposit a first tungsten layer on the surface of the conductive substrate; and (b) depositing the first tungsten layer in step (a). The supply of the reaction gas is stopped and the supply of the carrier gas is continued so that fluorine taken into the first tungsten layer from the reaction gas diffuses outward from the first tungsten layer. (c) supplying both the reaction gas and the carrier gas to chemically vapor deposit a second tungsten layer on the surface of the first tungsten layer; and (d) the step of The supply of the reactive gas is stopped, and the carrier is and a step of continuing to supply the gas, and in the step (a), the thickness of the first tungsten layer is
The fluorine contained in the first tungsten layer is
In step (b), the second tungsten layer is formed to a thickness that is almost completely out-diffused, and in the step (c), the thickness of the second tungsten layer is increased so that the fluorine contained in the second tungsten layer is A method for manufacturing a semiconductor device, characterized in that (d) is formed to a thickness that causes almost complete out-diffusion. (2) When selectively chemical vapor-depositing a tungsten layer on the conductive substrate exposed in the opening of the insulating film in a mixed gas of tungsten hexafluoride and monosilane as a reactive gas and a carrier gas. (a) supplying the reactive gas and the carrier gas together to chemically vapor deposit a first tungsten layer on the surface of the conductive substrate; and (b) depositing the first tungsten layer in step (a). A step of stopping the supply of the reaction gas and carrier gas and performing vacuum evacuation so that fluorine taken into the first tungsten layer from the reaction gas diffuses outward from the first tungsten layer. and (c) supplying both the reaction gas and the carrier gas to chemically vapor deposit a second tungsten layer on the surface of the first tungsten layer, and (d) the step (c) stopping the supply of the reaction gas and carrier gas so that the fluorine taken into the second tungsten layer from the reaction gas diffuses outward from the second tungsten layer; In the step (a), the thickness of the first tungsten layer is reduced so that fluorine contained in the first tungsten layer is almost completely removed in the step (b). In step (c), the thickness of the second tungsten layer is reduced so that the fluorine contained in the second tungsten layer is almost completely removed in step (d). 1. A method for manufacturing a semiconductor device, characterized in that the semiconductor device is formed to a thickness that causes outward diffusion.