WO2001027988A1

WO2001027988A1 - Processing method

Info

Publication number: WO2001027988A1
Application number: PCT/JP2000/007082
Authority: WO
Inventors: Yasuo Kobayashi; Masao Yoshioka
Original assignee: Tokyo Electron Limited
Priority date: 1999-10-12
Filing date: 2000-10-12
Publication date: 2001-04-19
Also published as: JP2001110785A; TW563166B

Abstract

A processing method which comprises washing an organic material and particles adhered to an article to be processed with SC-1 solution, activating a mixture of N2 gas and H2 gas by a plasma to form an active gas species, introducing NF3 gas downstream from the active gas species to thereby activate the NF3 gas, exposing the surface of the article to be processed to the resultant active gas species of NF3 gas to react the active gas species with a film formed by natural oxidation on the article and form a formed film, and heating the article to a predetermined temperature to thereby vaporize the formed film. The method can be employed for reducing the contact resistance defined in the specification even in a fine hole or a narrow portion, while maintaining a good state after processing.

Description

TECHNICAL FIELD The present invention relates to a processing method for removing an oxide film formed on a surface of an object to be processed. Background art

Conventionally, as a method of effectively removing an oxide film in a fine hole formed on a wafer in a manufacturing process of a semiconductor device or the like, for example, the following processing methods are available.

First, a mixed gas of N 2 gas and H 2 gas is activated by plasma to form an active gas species, and NF 3 gas is added to the down flow of the active gas species to activate the NF 3 gas. The active gas species of the NF 3 gas reacts with the oxide film on the surface of the wafer to form a generated film, and then the wafer is heated to a predetermined temperature to vaporize and remove the generated film.

Such a processing method is capable of processing fine holes and narrow portions, and has a good condition after processing.

However, in this processing method, when the conductive material is buried in the hole after removing the oxide film at the bottom of the hole, the resistance of the contact portion between the hole bottom and the conductive material buried in the hole (hereinafter, referred to as “the resistance”) However, there was a problem that the contact resistance could not be reduced, and the yield was poor.

The present invention has been made in order to solve the above problems, and has as its object to provide a processing method capable of reducing contact resistance and thus improving yield. Disclosure of the invention

In the invention described in claim 1, the object to be treated contains ammonia and hydrogen peroxide. After cleaning with a cleaning solution, the mixed gas of N 2 gas and H 2 gas is activated by plasma to form an active gas species, and NF 3 gas is added to the down flow of the active gas species to add NF 3 gas. Activated, exposing the active gas species of NF 3 gas to the surface of the object to be processed, reacting it with the oxide film to form a formed film, and heating the object to a predetermined temperature to generate it. It is characterized in that the film is vaporized and the object to be processed is washed. The invention described in claim 2 is characterized in that the supply flow rate of the N 2 gas is not less than 300 SCCM and not more than 500 SCCM.

The invention described in claim 3 is characterized in that the supply flow rate of the H 2 gas is not less than 200 SCC M and not more than 400 SCC M.

The invention described in claim 4 is characterized in that the supply flow rate of the NF 3 gas is 20 SCCM or more and 80 SCCM or less.

The invention described in claim 5 is characterized in that the process pressure in the step of forming the formed film is not less than 399 Pa and not more than 665 Pa.

The invention described in claim 6 is characterized in that the power for generating plasma is not less than 250 W and not more than 350 W.

The invention described in claim 7 is characterized in that the heating temperature when heating the formed product film is 100 ° C. or higher. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram showing an example of a processing apparatus used in the processing method of the present invention. FIG. 2 is a diagram illustrating the effect of the present invention.

FIG. 3 is a diagram illustrating the effect of the present invention.

FIG. 4 is a diagram showing the relationship between the N 2 flow rate, the etching rate, and the uniformity. FIG. 5 is a diagram showing the relationship between the H 2 flow rate, the etching rate, and the uniformity. FIG. 6 is a diagram showing the relationship between the flow rate of NF 3 and the etching rate and uniformity. FIG. 7 is a diagram showing the relationship between the process pressure and the etching rate and uniformity. C FIG. 8 is a diagram showing the relationship between the microwave output and the etching rate and uniformity.

FIG. 9 is a diagram showing the relationship between the heating temperature after the process and the etching rate. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of a processing method according to the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram showing an example of a processing apparatus used in a natural oxide film removing step in the processing method according to the present invention. In this figure, a processing apparatus 12 is provided with an oxide film, particularly a natural gas, for a plasma forming tube 14 for activating a mixed gas of N 2 gas and H 2 gas by plasma and a semiconductor wafer W to be processed. A treatment container 16 for performing a predetermined surface treatment for removing an oxide film (an oxide film formed unintentionally by contact with oxygen in the atmosphere or a cleaning solution).

A mounting table 20 on which a wafer to be processed is mounted is provided inside the processing container 16, and an exhaust port 22 is provided at a peripheral edge at the bottom of the processing container 16. The inside of the processing vessel 16 can be evacuated. An irradiation port 26 is formed at the bottom of the processing container 16 below the mounting table 20, and the irradiation port 26 is provided with a transmission window 28. Below the transmission window 28, a number of heating lamps 36 are provided for heating the mounting table 20 from the lower surface side, and the heating light emitted from the heating lamps 36 is transmitted therethrough. The light passes through the window 28 and enters the back surface of the wafer W.

On the other hand, the plasma forming tube 14 is open at the ceiling of the processing vessel 16 and is attached to the processing vessel 16 in an upright state. An introduction nozzle 46 for introducing a plasma gas composed of N 2 gas and H 2 gas is provided at the upper end of the plasma forming tube 14, and a gas passage 48 is provided in the introduction nozzle 46. Consolidated. An N 2 gas source 52 and an H 2 gas source 54 are connected to the gas passages 48 via flow controllers 50, respectively.

In addition, the underneath of the introduction nozzle 4 6, _c the plasma forming section 5 6 plasma generation unit 5 6 is provided, 2. 4 5 GH z microwave source 5 8 for generating microwaves with A microwave generated by the microwave generation source 58 through the rectangular waveguide 62. 60. Then, plasma is generated in the plasma forming tube 14 by the supplied microwave, and H 2 gas and The N2 gas mixture is activated to form a downhole. An outlet 64 at the lower end of the plasma forming tube 14 is provided with a cover member 66 extending downward in an umbrella shape. The cover member 66 covers an upper portion of the mounting table 20 so that gas can be efficiently removed from the wafer. It is made to flow down to W. An NF 3 gas supply unit 68 for supplying NF 3 gas is provided immediately below the outlet 64. The NF 3 gas supply section 68 has a shower head 70, and the shower head 70 is connected to a NF 3 gas source 8 through a communication pipe 74, a gas passage 76, and a flow controller 78. Connected to 0.

Next, a processing method according to the present invention will be described.

First, a wafer to be processed is cleaned with a cleaning liquid generally called SC-1 solution or APM solution containing ammonia and hydrogen peroxide.

Next, the semiconductor wafer W washed with the SC-1 solution is mounted on the mounting table 20 of the processing apparatus 12 shown in FIG.

After the wafer W is mounted on the mounting table 20, the inside of the processing container 16 is sealed, and the inside is evacuated. Then, N 2 gas and H 2 gas are introduced from the N 2 gas source 52 and the H 2 gas source 54 at a predetermined flow rate into the plasma forming tube 14 from the introduction nozzle 46. At the same time, a microwave of 2.45 GHz is generated from the microwave generating source 58 of the microwave forming section 56 and guided to the Evenson-type waveguide 60, thereby forming the plasma forming tube. 1 Introduce into 4. As a result, the N 2 gas and the H 2 gas are turned into plasma and activated by the microwaves, and active gas species are formed. The active gas species forms a downflow by evacuation in the processing container 16 and flows down the plasma forming tube 14 toward the outlet 64.

On the other hand, the NF 3 gas supplied from the NF 3 gas source 80 is supplied from the NF 3 gas source 80 to the N 2 gas from the ring-shaped shower head 70 of the NF 3 gas supply unit 68 disposed outside the plasma forming tube 14. As a result, the added NF 3 gas is also activated by the down-flow active gas species. In this way, the NF 3 gas is also converted into an active gas, and reacts with the natural oxide film on the surface of the wafer W in combination with the above-mentioned active gas species in the downflow to form a mixed film of Si, N, H, and F. I do. This process promotes the reaction at low temperatures, so it can be produced at room temperature. A film is formed.

The process conditions at this time are as follows: gas supply flow rates of H2, NF3, and N2 are 300 S CCM, 60 SCCM, and 400 SCCM, respectively. Here, SCCM (standard cubic centimeters per minute) means cubic centimeters per minute (under standard conditions). The process pressure is 532 Pa, the plasma power is 350 W, and the process time is 1 minute. In this way, a formed film reacting with the natural oxide film is formed on the wafer surface. In this case, since the upper part of the mounting table 20 is covered with the umbrella-shaped covering member 66, the dispersion of the active gas species in the downflow is suppressed, and the active gas species flows down onto the wafer surface efficiently. A formation film can be formed on the substrate.

When the formation of the generated film is completed in this way, the supply of the gases H2, NF3, and N2 is stopped, the driving of the microwave generation source 58 is also stopped, and the processing chamber 16 is evacuated. To eliminate residual gas. Thereafter, the heating lamp 36 is turned on to heat the wafer W to a predetermined temperature, for example, 100 ° C. or higher. By this heating, the above-mentioned generated film is sublimated (vaporized). As a result, the natural oxide film on the wafer W is removed, and the Si surface appears on the wafer surface.

The process conditions at this time are a process pressure of 133 Pa and a process time of about 1 minute.

Fig. 2 shows the comparison of the contact resistance between the case where this treatment method is adopted and the case where the treatment with SC-1 solution (APM solution) is not performed in advance only in the natural oxide film removal step. It is. In this figure, graph 1 (graph indicated by “1〇—”) shows the case where the natural oxide film is removed after the treatment with SC-1 solution, and graph 2 (graph indicated by “1” —) Here, the case where only the natural oxide film removing step is not performed beforehand with the SC-1 solution is shown. As is clear from this figure, the contact resistance value when the native oxide film is removed after cleaning with SC-1 solution is significantly reduced compared to the case where only the native oxide film is removed.

Figure 3 shows the comparison of the contact resistance between the case where the natural oxide film is removed after the treatment with SC-1 solution and the case where the cleaning with the DHF solution is performed after the cleaning with SC-11 solution. is there. In this figure, the graph 1 (the graph indicated by “1〇1”) similarly shows the case where the natural oxide film is removed after the treatment with the SC-1 solution. Graph 3 (graph indicated by “1x—”) shows the case where washing with DHF solution was performed after treatment with SC-1 solution. As can be seen from this figure, when the natural oxide film is removed after cleaning with SC-1 solution, the resistance value is lower than when cleaning with DHF solution is performed after cleaning with SC-1 solution. Decrease.

As described above, in this processing method, the value of the contact resistance can be significantly reduced as compared with the case where only the natural oxide film is removed, and the yield can be improved.

By the way, in the above processing method, the etching rate and the uniformity of the etching are extremely important in the processing steps. Therefore, to improve the etching rate and uniformity, the optimum conditions of the process were investigated based on experiments. The result will be described below. Here, the etching rate is (amount of decrease in film thickness by the above-described processing method) / (time during which an active gas species reacts with an oxide film).

FIGS. 4 to 9 are graphs showing experimental results for the process conditions. In these figures, the graphs plotted with circles indicate the etching rate, and the graphs plotted with squares indicate the uniformity.

Figure 4 shows a flow of H2 of 300 SCCM, a flow of NF3 of 60 SCCM, a microphone output of 350 W, a process pressure of 532 Pa, a process time of 1 min, and post-process heating (140 ° C). The values of the etching rate (angstrom / min) and the uniformity (%) with respect to the flow rate of N2 are shown for 1 min. As can be seen from this graph, the N2 flow rate is appropriately 300 SCCM or more from the viewpoint of the etching rate, and considering uniformity, 300 to 500 SCCM is preferable.

Figure 5 shows a flow rate of NF 3 of 60 SCCM, a flow rate of N 2 of 400 SCCM, a microphone output of 350 W, a process pressure of 532 Pa, a process time of 1 min, and post-process heating (140 (° C) lmin, the values of etching rate (angstrom / min) and uniformity (%) with respect to the flow rate of H2 are shown. As can be seen from this graph, the appropriate H2 flow rate is 200-400 SCCM in terms of etching rate and 300-400 SCCM in terms of uniformity. Figure 6 shows a flow rate of H2 of 300 SCCM, a flow rate of N2 of 400 SCCM, a microphone output of 350 W, a process pressure of 532 Pa, a process time of 1 min, and post-process heating (140 (° C) lmin shows the values of the etching rate (angstrom / min) and the uniformity (%) with respect to the NF3 flow rate. As can be seen from this graph, the etching rate is not significantly affected by changing the NF3 flow rate. Therefore, from the viewpoint of uniformity, NF3 is practically 20 to 80 SCCM, and 20 to 60 SCCM is more preferable.

Figure 7 shows that the flow rate of H2 was 300 SCCM, the flow rate of NF 3 was 60 SCCM, the flow rate of N2 was 400 SCCM, the microwave output was 350 W, the process time was 2 min, and the post-process heating (140 ° C) was 1 min. In this case, the values of the etching rate (Angstrom Zmin) and the uniformity (%) are shown with respect to the process pressure (Pa). As can be seen from this graph, the process pressure (Pa) is suitably from 399 to 665 Pa, and more preferably 532 Pa, from the viewpoint of etching rate and uniformity.

Figure 8 shows a flow rate of H2 of 300 SCCM, a flow rate of NF3 of 60 SCCM, a flow rate of N2 of 400 SCCM, a process pressure of 532 Pa, a process time of 1 min, and post-process heating (140 ° C). The values of the etching rate (angstrom / min) and the uniformity (%) with respect to the microwave output (W) are shown when 1 min is used. As can be seen from this graph, a microwave output (W) of 250 W or more is appropriate from the viewpoint of the etching rate and uniformity. In addition, when the processing is performed with a microwave output of 350 W, charge-up damage occurs in one of several wafers, so that it is preferably 350 W or less.

FIG. 9 shows the value of the etching rate (angstrom / min) with respect to the heating temperature (° C) in the heating after the process of 1 min at 133 Pa. In this graph, at 80 ° C., it is shown that the formed film is not sufficiently vaporized. Therefore, the heating temperature should be 100 ° C or higher from the viewpoint of the etching rate.

In these figures, “max-min (%)” means that the maximum value of the etching rate at a plurality of points on the wafer is max and the minimum value is min. Shows the uniformity expressed as (max—min) / (max + min) × 100 (%). Thus, in this processing method, the H2 flow rate, NF3 flow rate, N2 flow rate, microphone mouth wave output, process pressure, and process time are set to predetermined values, and the etching rate and etching rate can be adjusted. Uniformity can be improved. Therefore, processing efficiency and uniformity can be improved.

As described above, according to the invention set forth in claim 1, after the object to be processed is washed with a cleaning solution containing ammonia and hydrogen peroxide, a natural oxide film removing step, that is, The mixed gas of N 2 gas and H 2 gas is activated by plasma to form an active gas species, and NF 3 gas is added to this active gas species to activate the NF 3 gas. The active gas species is exposed to the surface of the object to be processed, and is reacted with a natural oxide film to form a generated film. By heating the object to be processed to a predetermined temperature, the raw film is vaporized. Therefore, the contact resistance can be greatly reduced as compared with the case where only the natural oxide film removing step is performed, and the yield can be improved.

According to the invention described in claim 2, the processing efficiency and uniformity can be improved.

According to the invention set forth in claim 3, processing efficiency can be improved.

According to the invention set forth in claim 4, the uniformity of the treatment can be improved.

According to the invention set forth in claim 5, processing efficiency and uniformity can be improved.

According to the invention set forth in claim 6, processing efficiency and uniformity can be improved.

According to the invention set forth in claim 7, the processing efficiency can be improved.

Claims

The scope of the claims

1. After cleaning the object with a cleaning solution containing ammonia and hydrogen peroxide, a mixed gas of N2 gas and H2 gas is activated by plasma to form an active gas species, and NF3 The gas is added to activate the NF 3 gas, the active gas species of the formed NF 3 gas is exposed to the surface of the object to be processed, and this is reacted with an oxide film to form a generated film. A processing method, wherein the generated film is vaporized by heating to a predetermined temperature, and the object to be processed is washed.

2. The processing method according to claim 1, wherein the supply flow rate of the N 2 gas is not less than 300 SCM and not more than 500 SCM.

3. The processing method according to claim 1, wherein a supply flow rate of the H 2 gas is 200 S CCM or more and 400 S CCM or less.

4. The processing method according to claim 1, wherein a supply flow rate of the NF 3 gas is 20 S CCM or more and 80 S CCM or less.

5. The process pressure of the process of forming the formed film is 399? & More than 665? The processing method according to claim 1, wherein a is equal to or less than a.

6. The processing method according to claim 1, wherein the power for generating the plasma is 250 W or more and 350 W or less.

7. The processing method according to claim 1, wherein a heating temperature when heating the formed product film is 100 ° C. or higher.