JPH04336422A - Wiring forming method and ecr etching apparatus used for the same - Google Patents

Abstract

PURPOSE:To easily form tungsten plug wiring only within a contact hole by forming a reaction seed film which will become a reaction seed for tungsten only within a contact hole on a semiconductor substrate. CONSTITUTION:A tungsten silicide (WSix) film 6, which will become a reaction seed film for CVD growth of selected tungsten, is formed in the thickness of 50nm. Next, the WSix film 6 is anisotropically etched to form a reaction seed (WSix) film 6a by leaving a part in the height of 0.4mum within a contact hole 4. In this case, a wafer (Si substrate 1) is inclined by about 45 degrees. Next, a tungsten plug wiring 7 is selectively grown by the CVD method under the reduced pressure condition on the reaction seed (WSix) film 6a and only within the contact hole 4.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a wiring forming method and an E
Regarding CR etching equipment, a wiring formation method in which a heat-resistant tungsten (W) plug is formed using a selective tungsten CVD method, and an EC used in the method.
This relates to an R etching device.

0002

2. Description of the Related Art When electrode wiring is formed in a contact hole provided in an insulating film on a semiconductor substrate, a method has conventionally been used in which a metal such as aluminum (Al) is deposited by sputtering. However, as the contact hole diameter becomes finer and the aspect ratio becomes larger, it has become difficult to fill the contact hole with Al using the sputtering method.

[0003] Therefore, selective CVD (chemical vapor deposition) is attracting attention as one of the new techniques for burying fine contact holes. Among them, selective tungsten CV
D is promising as a technology that is close to practical application. However, there is a problem in that tungsten tends to react particularly with underlying materials such as Si, and the reaction occurs when heated to about 600°C.

0004

As a countermeasure to this problem, a method is known in which a barrier metal layer is formed between the tungsten and the underlying material. However, this countermeasure also applies to Ti
On the barrier metal such as N, the raw material gas WF6 etc. is applied to TiN.
Tungsten does not grow selectively because it is adsorbed onto the surface and difficult to dissociate.

Japanese Patent Application Laid-Open No. 62-243324 discloses a selective growth method for tungsten in which polycrystalline silicon (poly-Si) is grown only on the side and bottom surfaces of the contact hole.
A method is disclosed in which a film is formed as a reactive species and then reacted with a source gas WF6 to grow tungsten (W) only in the contact hole.

However, since this method uses a resist etch-back step, the number of steps is increased, and throughput becomes a problem. In addition, in places where the contact hole has a steep step difference, there may be differences in the remaining film thickness after resist etchback, or in fine contact holes, the resist may not fully penetrate into the hole, or the resist may be selectively grown in the final resist removal process. This causes problems such as the reactive species (poly-Si) being oxidized and selective growth being inhibited. Furthermore, the method disclosed in the above-mentioned publication forms only reactive species before forming W in the contact hole, and does not simultaneously form barrier metal at the bottom of the contact hole. It has a heat resistance of only about 300°C.

[0007] Proceedings of the Japan Society of Applied Physics, Spring 1991 (presented on March 28, 1991), page 691, 30P-W-6
discloses a technical summary titled "Interlayer wiring of tertiary elements using selective CVD-W". W disclosed here
Of the three-layer wiring of /TiN/TiSix, W formed by selective CVD is formed not only in the contact hole but also above the contact hole, and voids are also observed in the contact hole.

The present invention provides a wiring forming method for easily forming a tungsten (W) plug wiring having heat resistance at a temperature of approximately 900°C, and an ECR (Electrometer) used in the method.
Cyclotron Resonance) etching apparatus.

[0009]

[Means for Solving the Problems] According to the present invention, the above-mentioned problems are achieved by a step of forming an insulating film on a semiconductor substrate, a step of forming a contact hole in the insulating film, and a step of preventing the semiconductor substrate from reacting with the lower wiring. a step of forming a barrier metal layer on the entire surface including the inner wall surface of the contact hole, a step of forming a metal thin film or a semiconductor thin film that becomes a reactive species of selective tungsten by CVD method on the entire surface of the barrier metal layer, EC the thin film so as to leave at least the bottom part inside the contact hole.
The problem is solved by a wiring forming method characterized by including a step of R etching and a step of selectively forming a tungsten wiring only in the contact hole.

[0010]Furthermore, the above-mentioned problem is solved according to the present invention, which includes an ECR generation device comprising a microwave introduction tube and a magnetic field generation coil, and an introduction tube for etching gas to be plasma ionized using the ECR generation device. The method comprises a plasma reaction chamber and an ion accelerator for accelerating plasma ions of the etching gas, and a substrate to be etched placed in the plasma reaction chamber is arranged to be tiltable and rotatable. This problem is solved by the characteristic ECR etching equipment.

[0011]

[Function] According to the present invention, a reactive species film 6 such as a tungsten silicide film, which becomes a reactive species with tungsten, is formed only in the contact hole 4 on the semiconductor substrate of the silicon substrate 1. The tungsten (W) plug wiring 7 can be easily formed only within the wafer 4. Moreover, in the ECR etching apparatus according to the present invention, since the substrate to be etched (wafer) 15 can be tilted and rotated, directional ECR plasma ions can be used for etching the inner wall of the contact hole. In combination with this, only the upper inner wall of the contact hole can be etched. Therefore, a reactive species film (eg, poly-Si, WSix, etc.) with tungsten can be formed only at least at the bottom of the contact hole.

0012

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

FIGS. 1 to 4 are process cross-sectional views showing one embodiment of the wiring forming method according to the present invention. First, as shown in FIG. 1, an insulating film 3 made of, for example, SiO2 and having a thickness of about 800 nm is formed on a silicon substrate 1 as a semiconductor substrate on which a highly concentrated diffusion layer 2 is formed. A contact hole 4 is formed. The opening width of the contact hole 4 was approximately 0.4 μm.

Next, as shown in FIG.
Alternatively, as a barrier metal layer 5 to prevent reaction with lower layer wiring, a 70 nm thick TiO film is coated on the entire surface of the silicon substrate 1.
A N film and a 30 nm thick Ti film are sequentially formed by sputtering. The barrier metal layer 5 may be formed by a CVD method, and is not limited to TiON/Ti, but may be made of Ti/TiN, TiN/TiW, or the like as long as it has barrier properties.

Next, as shown in FIG. 3, a tungsten silicide (WSix) film 6 to be a reactive seed film for selective tungsten CVD growth is formed to a thickness of 50 nm. WS
The formation (CVD) conditions for ix were a temperature of 360°C and a pressure of 5T.
orr, WF6/SiH4/H2=10/1000/3
It was set to 60 sccm. As a seed for growth, the above WSix
Instead of polycrystalline silicon (poly-Si) under reduced pressure C
It may be deposited to a thickness of about 30 nm using the VD method. In addition, tungsten (W), molybdenum (Mo), molybdenum silicide (MoSi), etc. can be used.

Next, as shown in FIG. 4, the WSix film 6 is anisotropically etched using an ECR etching apparatus according to the present invention, which will be described later.
A reactive species (WSix) film 6a is formed leaving only a portion with a height of μm. At this time, the wafer (Si substrate 1) was tilted at about 45 degrees. Note that at this time, the wafer 15 is rotated via two shafts 20 and 21, which will be described later. ECR etching conditions are SF6 gas = 10 sccm, μ wave power = 1K.
W, acceleration voltage=100 V, and pressure 10 −4 Torr.

Next, as shown in FIG. 5, a W plug wiring 7 is grown on the reactive species (WSix) film 6a and only within the contact hole 4 by selective CVD under reduced pressure.

[0018] The selected CVD conditions at this time are a temperature of 260°C.
, pressure 0.2 Torr, WF6/SiH4/H2=10
/7/1000 sccm. The height of W in the contact hole may be such that voids are not created in the next wiring process.

In this example, only WSix was ECR etched in FIG. 4, but TiON was etched at the same time as WSix.
/Ti barrier metal layer 5 may also be removed by etching. The ECR etching conditions at that time were Cl2/SF6=
10/10sccm, μ wave power = 1KW, acceleration voltage =
The voltage was 100V and the pressure was 1×10 −4 Torr. In this way, the W plug wiring 7 having the barrier metal layer 5 as the lower layer can be formed in the contact hole 4 on the semiconductor silicon substrate 1. After this, a high melting point metal, such as W, is further added.
, Mo, etc. are deposited on the entire surface to form wiring.

FIG. 6 is a schematic diagram of the ECR etching apparatus according to the present invention. The ECR etching apparatus 25 shown in FIG. 6 includes coils 10 and 11, an ECR position 12,
In a known configuration consisting of an ion accelerator 13, a sample stage 14, and a wafer 15, the sample stage (susceptor) 14 that supports the wafer 15 is a semiconductor silicon substrate (wafer).
The central axis of is the rotation axis a with respect to the incident direction of plasma ions.
It is possible to tilt about 30 to 80 degrees through 20,
Moreover, they are rotated at 10 to 60 rpm and 10 to 60 rpm via the rotating shaft b21 and the rotating shaft c22, respectively.

FIGS. 7 and 8 are a side view and a top view of the sample stage tilting rotation support according to the present invention. 7 and 8 show a state in which the wafer is placed flat on the sample stage.

FIG. 9 is a side view showing the sample stage tilted by an angle α.

In the sample stage inclined rotation support according to the present invention, the sample stage (susceptor) 14 is rotated by the rotation axis a by the motor a16.
20 as a support and is rotated and tilted by the predetermined angle (30 to 80 degrees). If the angle is less than 30 degrees, the bottom of the contact hole will also be etched depending on the aspect ratio, and if it exceeds 80 degrees, the etching will be weak. Further, the susceptor 14 is rotated by the motor a16 while being tilted at a predetermined angle about the rotation axis b21, and further rotated by the motor b17 about the rotation axis c22. In the figure, 18 is a rotary table for fixing the motor a16, 23 is a cradle for the rotating shaft a20, and 19 is a fixing table for the motor b21.

[0024]

[Effects of the Invention] As explained above, the EC according to the present invention
Since selective etching is easily performed using an R etching device, a heat-resistant tungsten (W) plug wiring can be formed. Therefore, after the W plug is formed, a TFT (thin film transistor) or the like is formed. Furthermore, the method of the present invention does not require an etch-back process, simplifying the process.

[Brief explanation of drawings]

FIG. 1 is a process sectional view showing an embodiment of the method of the present invention.

FIG. 2 is a process sectional view showing an embodiment of the method of the present invention.

FIG. 3 is a process sectional view showing an embodiment of the method of the present invention.

FIG. 4 is a process sectional view showing an embodiment of the method of the present invention.

FIG. 5 is a process sectional view showing an embodiment of the method of the present invention.

FIG. 6 is a schematic diagram of an ECR etching apparatus according to the present invention.

FIG. 7 is a side view of the sample stage tilting rotation support according to the present invention.

FIG. 8 is a top view of the sample stage inclined rotation support according to the present invention.

FIG. 9 is a side view showing a state in which the sample stage is tilted by an angle α.

[Explanation of symbols]

1 Silicon substrate 2 Diffusion layer 3 Insulating film 4 Contact hole 5 Barrier metal layer 6 Tungsten silicide (WSix) film 6a
Reactive species WSix film 7 Tungsten (W) plug wiring 9 Waveguides 10, 11 Coils 12 ECR position 13 Ion accelerator 14 Sample stage 15 Wafer 16 Motor a 17 Motor b 18 Rotating table/motor a fixed table 19 Motor b fixed table 20 rotating shaft a 21 rotating shaft b 22 rotating shaft c 23 holder for rotating shaft a 25 ECR etching device

Claims (2)

[Claims] 1. A step of forming an insulating film on a semiconductor substrate, a step of forming a contact hole in the insulating film, and a barrier metal layer for preventing reaction between the semiconductor substrate and lower wiring, including the inner wall surface of the contact hole. a step of forming a metal thin film or a semiconductor thin film that becomes a reactive species of selective tungsten on the entire surface of the barrier metal layer by a CVD method; a step of forming the metal thin film or semiconductor thin film on the entire surface of the barrier metal layer, leaving at least only the bottom portion of the metal thin film or the semiconductor thin film inside the contact hole; 1. A method for forming a wiring, comprising the steps of performing ECR etching as described above, and selectively forming a tungsten wiring only in the contact hole. 2. A plasma reaction chamber comprising: an ECR generator including a microwave introduction pipe and a magnetic field generating coil; an etching gas introduction pipe to be plasma ionized using the ECR generator; An ECR etching apparatus comprising: an ion accelerator for accelerating plasma ions; and a substrate to be etched placed in the plasma reaction chamber is arranged to be tiltable and rotatable.