JPH04356919A - Selective metal formation - Google Patents

Abstract

PURPOSE:To provide a method of selectively forming a metal layer which ensures excellent selectivity, flatness and enables reduction of process. CONSTITUTION:A method of selectively forming a metal layer comprises steps for removing an oxide film formed on a substrate 2a with radiation of a short frequency pulse laser 5a and hydrogen as a means for heating a local area within a short period of time, forming selectively at least one atom layer of metal with good flatness by predetermined laser radiation of the raw material gas of a metal to be grown and selectively forming a metal layer using at least one atom layer of the metal as a nucleus.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a selective metal, and particularly to a method for forming a selective metal such as tungsten, which can be buried in contact holes or through holes with excellent selectivity and flatness.

0002

[Prior Art] Selective CVD (chemical vapor deposition) of tungsten (W), which is a typical example of a selective metal forming method, is a method for converting tungsten hexafluoride (WF6) gas into silicon (Si).
This is a method (selective tungsten CVD method) in which W is deposited on a specific region of the substrate by reduction on the surface of the substrate.

[0003] CVD selective growth of W occurs because the time required to start growth differs depending on the substrate surface, that is, the underlying material.

For example, silicon (Si) is used as the base material.
On conductive materials such as or aluminum (Al), the C of W
VD growth starts early and CVD growth slows on insulating materials such as SiO2. Such a difference in the growth rate of W is determined by whether or not there are free electrons in the underlying layer.

[0005]

[Problem to be solved by the invention] However, even on the diffusion layer (n+/P, P+/n) where nuclei are likely to occur,
Where a natural oxide film (SiOx) is formed and remains on the Si surface, nuclei are difficult to generate, and W is not formed uniformly on the surface and lacks flatness, and on W wiring that lacks flatness. There has been a problem that wiring made of, for example, aluminum (Al) deposited on the substrate is likely to be disconnected.

[0006] Since the growth of W is nucleation as mentioned above,
It is known that W nucleation is delayed on P+/n, resulting in a difference in growth rate.

An object of the present invention is to provide a selective metal CVD method that has excellent selectivity and flatness and can shorten the process.

[0008]

[Means for Solving the Problems] According to the present invention, the above-mentioned problems are solved by: (i) removing the native oxide film formed on the substrate by local, short-time heating means using short-wavelength pulsed laser irradiation and hydrogen; (b) A step of selectively forming at least one atomic layer of the metal with good flatness by locally heating the raw material gas of the metal to be grown by short-wavelength pulsed laser irradiation. The problem is solved by a selective metal forming method characterized by comprising the step of: c) selectively forming the metal using at least one atomic layer of the metal as a core.

According to the present invention, it is preferable to carry out at least the steps (b) and (c) continuously.

0010

[Operation] In the present invention, since the natural oxide film (SiOx) 22 in a predetermined metal growth region is first removed in step (a), nuclei of, for example, tungsten are likely to be generated.

The above-mentioned predetermined laser irradiation is capable of locally heating and high-temperature processing, which is particularly useful for processing only the buried portion as in the present invention.

[0012] In step b), at least one atomic layer, preferably 2 to 4 several atomic layers (CVD of W in the next step)
After forming the tungsten layer 24 (which will serve as a growth nucleus) with good flatness, normal selective metal formation is performed in step c), making it easy to form W and improving selectivity and flatness.

When XeCl with a short wavelength of 308 nm is used as the excimer lasers 5a and 5b as the predetermined lasers, the Si surface 20 becomes high in temperature due to local and pulsed light absorption, and the SiO2 film 21 has no light absorption. Not heated. Therefore, temperature control is also possible by using an excimer laser. Furthermore, since laser irradiation through the glass window becomes possible, a step-and-repeat mechanism of the laser irradiation unit becomes possible.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 shows a selection W for explaining the method of the invention.
It is a schematic diagram of a CVD apparatus. This device basically employs a three-chamber system, which is one of the multi-chamber systems.

As shown in FIG. 1, the present selective W CVD
The apparatus has three chambers, a first vacuum chamber 1a, a second vacuum chamber 1b, and a third vacuum chamber 1c, arranged to enable continuous processing.

First vacuum chamber 1a for natural oxide film
and a second vacuum chamber for tungsten nucleus generation.
eCl (wavelength 308 nm) excimer laser 5a, 5b
are provided for each.

[0017] Wafers 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a, 2a and 2 wafers are placed in each vacuum chamber 1a, 1b, and 1c as substrates to be processed, respectively.
Wafer support stands 3a, 3b and 3c on which wafers 2b and 2c are mounted are provided, and a first vacuum chamber 1a is further provided.
H2 gas supply pipe 4 on the side wall of , and tungsten hexafluoride (WF6) supply pipes 6b, 6c on the respective side walls of the second vacuum chamber 1b and the third vacuum chamber 1c,
Further, silane (SiH4) supply pipes 7b and 7c are provided.

Using the above-mentioned selected W CVD apparatus, this example was carried out as follows.

The first vacuum chamber 1a in FIG. 1 is a vacuum chamber for removing a native oxide film (SiOx), and as shown in an enlarged view in FIG. Si, which is an insulating film formed on
The Si substrate 2 is exposed as an n+ or P+ diffusion layer 23 at the bottom of an opening (contact hole) provided in the O2 film 21.
The SiOx (natural oxidation) film 22, which is formed when the surface of the wafer 2a (wafer 2a) is naturally oxidized by oxygen in the atmosphere and reduces the selectivity and flatness of selective WCVD, is transferred to the H2 gas supply pipe 4 in FIG. Hydrogen (H2) gas and xenon chloride (XeCl: wavelength 308
clean S without the SiOx film 22 is removed using thermal energy irradiated with an excimer laser 5a using
An i-substrate 20 is obtained (FIG. 2(b)).

Excimer laser irradiation is effective for firing because it allows local heating (in this embodiment, the contact hole portion) and high-temperature treatment. After cleaning the surface of the Si substrate (wafer) in the first vacuum chamber 1a as described above, the wafer 2a is transferred to the second vacuum chamber 1b as a wafer 2b via the valve 10. In this second vacuum chamber 1b, tungsten (W) growth source gases WF6 and SiH4 are supplied via the WF6 supply pipe 6b and the SiH4 supply pipe 7b, respectively.
reacts during the step of FIG. 2C showing the step of irradiating the contact hole with the excimer laser 5b, forming a tungsten atomic layer 24 selectively and with good flatness as shown in FIG. 3A.

In the process shown in FIG. 2(c), the excimer laser uses XeCl (wavelength 308
Since only the very surface is heated, re-diffusion in the deeper diffusion layer is small. The tungsten atomic layer 24 formed in this step acts as a nucleus for the so-called normal selective W CVD growth in the next step.

The tungsten atomic layer 24 is n+ or P
+ After being formed on the diffusion layer 23, the wafer 2b is placed into the third vacuum chamber 1c via the valve 11.
Transfer as c. In this third vacuum chamber 1c, WF6 and SiH4 are supplied via the WF6 supply pipe 6c and the SiH4 supply pipe 7c, respectively.
Perform CVD.

When entering the third vacuum chamber 1c, a W atomic layer serving as a nucleus is uniformly grown by CVD on the diffusion layer as shown in FIG. 3(a). (b
) and FIG. 3(c), a tungsten buried layer 25 with better selectivity and flatness than before is formed. In addition, when forming this buried layer 25, heating of the Si substrate 20 was carried out at about 240-320 degreeC.

As described above, in this embodiment, SiOx as a natural oxide film is removed in the first vacuum chamber 1a, and W for nucleation is selectively grown in the second vacuum chamber 1b. Finally, the third vacuum chamber 1c
A normal selection WCVD is made within. These processes are
Preferably, it is carried out continuously. Note that raw material gas and the like are exhausted from the bottom of each chamber.

In the above embodiment, W growth for nucleation and normal selective W CVD are carried out in the second vacuum chamber 1b and the third vacuum chamber 1b.
The vacuum chamber 1c and the vacuum chamber 1c may be used separately in a common chamber.

In this embodiment, the selective CVD of W is explained, but it is possible to use a CVD process of other metals such as aluminum (Al) and not limited to W (tungsten) by changing the raw material.

[0027]

[Effects of the Invention] As explained above, according to the present invention,
Metals such as tungsten can be formed with good selectivity and flatness in contact holes, through holes, etc.

[Brief explanation of drawings]

FIG. 1: Selection W CV for illustrating the method of the invention.
It is a schematic diagram of D apparatus.

FIG. 2 is a cross-sectional view of the first half process of an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the second half process of an embodiment of the present invention.

[Explanation of symbols]

1a First vacuum chamber 1b Second vacuum chamber 1c Third vacuum chamber 2a, 2b, 2c Wafer 3a, 3b, 3c Wafer support stand 4 H2 gas supply pipes 5a, 5b Excimer laser 6b, 6c WF6 supply pipe 7b, 7c SiH4 supply pipe 20 Silicon (Si) substrate (wafer) 21 S
iO2 film 22 SiOx (natural oxidation) film 23 n+ or P+ diffusion layer 24 Tungsten (W) several atomic layers (for nuclear generation) 25
tungsten buried layer

Claims (2)

[Claims] Claim 1: a) A step of removing the natural oxide film formed on the substrate using short-wavelength pulsed laser irradiation and hydrogen, which is a means of local and short-time heating; a step of selectively forming at least one atomic layer of the metal with good flatness by means of local, short-time heating and irradiation with a short wavelength pulsed laser, and then c) at least one atomic layer of the metal. A selective metal forming method comprising the step of selectively forming the metal using as a core. 2. The selective metal forming method according to claim 1, wherein at least the steps (b) and (c) are performed continuously.