JPH01244615A - Film formation process - Google Patents

Abstract

PURPOSE:To prevent increase of electrical contact resistance and to enable a metallic thin film to be formed uniformly and stably, by completely removing a naturally oxidized film before formation of the film. CONSTITUTION:When mounting of a semiconductor wafer 2 on a mounting board 3 is finished, a hand arm 17 is retracted into a transportation preliminary chamber 20 and a gate valve 16 is closed. Under these conditions, cleaning of the wafer is carried out by etching off a naturally oxidized film formed on the wafer 2. After the etching, a metallic thin film is formed on the surface to be treated of the semiconductor wafer 2 by means of CVD process. The mounting board 3 carrying the semiconductor wafer 2 is formed of a quartz glass plate having a light-transmitting conductive film 4 thereon, so that, during the cleaning process, electric power can be applied to the light-transmitting conductive film 4 for converting treating gas uniformly into plasma and for realizing stable etching operation. Further, according to such arrangement, stable and uniform film formation can be obtained since the CVD can be performed while infrared rays as heating light is applied to the wafer from the side of the mounting board 3.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a film forming method.

(Prior Art) In general, physical vapor deposition (PVD) methods such as vapor deposition and sputtering have been used for many years as a technique for depositing metal thin films on semiconductor integrated circuits for wiring and the like.

However, as integrated circuits such as VLSIs become more highly integrated, faster, and more densely packed, the resistance of W, which is more than an order of magnitude lower than that of polycrystalline Si, is required to form gate electrodes, contact holes, through holes, etc. Techniques for depositing metal thin films of high melting point metals such as (tungsten) are becoming important.

As a means for forming the metal thin film as described above.

A metal thin film is formed using a metal CVD apparatus that grows a film growth gas on the processing surface of a processing target substrate.

Recently, in order to form a more uniform film thickness, the substrate to be processed is fixed to a quartz plate and heated by irradiating heating light such as infrared light from the quartz plate side. While performing CVD treatment in this heated state, when forming a metal thin film using the above-mentioned CVD apparatus, this carbon
When a substrate to be processed, such as a semiconductor wafer, is transferred from a pre-processing device for VD processing to a CVD device, a natural oxide film of, for example, about several dozen is formed on the surface of the semiconductor wafer.
Even if a metal thin film is formed on this oxide film, there is a problem in that the electrical contact resistance between silicon and metal increases, leading to a decrease in quality.

Also, for example, it is possible to form a gold FMR thin film after turning the processing gas into plasma and etching the natural oxide film formed on the semiconductor wafer, but in order to make the film thickness uniform during film formation, infrared light is When irradiating semiconductor wafers, the semiconductor wafer is fixed to transparent, insulating quartz, etc., so even if a reactive gas is supplied, it may not turn into plasma, or the plasma generation area is limited, making it difficult to uniformly etch the natural oxide film. The problem was that it couldn't be done.

This invention was made in response to the above points, and metal: 4
The object of the present invention is to provide a film forming method that completely removes a natural oxide film before forming a film, thereby preventing an increase in electrical contact resistance and making it possible to uniformly form a stable film.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a means for removing an unnecessary film formed on at least a surface to be processed of a substrate to be processed installed in a processing container, and a method for removing an unnecessary film formed on at least a surface to be processed of a substrate to be processed installed in a processing container, and The method is characterized by comprising means for forming a desired film on at least the surface to be processed of the substrate to be processed using a film growth gas in the processing container.

(Operation and Effect) A means for removing unnecessary particles formed on at least a surface to be processed of a substrate to be processed installed in a processing container; By comprising a means for forming a desired film on the surface using a film growth gas, it becomes possible to form a stable film on the processing surface of the processing target substrate.

In particular, if a metal thin film is formed after completely etching the native oxide film formed on a semiconductor wafer, it is possible to prevent an increase in electrical contact resistance that may occur between the silicon and metal thin film, thereby improving quality. can.

(Example) Hereinafter, an example will be described with reference to the drawings in which the method of the present invention is applied to the formation of a high-melting-point, full-reflection thin film by single-wafer processing in a thin tube formation process by chemical vapor deposition in a semiconductor manufacturing process. .

As shown in Figure 1, there is a cylindrical Al1 (aluminum) reaction chamber whose walls can be cooled with cooling water, etc.
Above, the substrate to be processed, for example, the surface to be processed, SL and 5un.
A semiconductor wafer ■ with a pattern structure of 2.

An installation plate (2) is provided that can be installed so that the surface to be treated faces downward and is made of a material such as quartz glass that can be rapidly heated (rapid thermal) using heating light, which will be described later. This installation board■
As shown in Figure 2, a transparent conductive film (
b) For example, SnO or ITO is coated to a thickness of, for example, several thousand. Further, above the installation plate (2), a conductive, cylindrical support body (2) made of AQ, for example, is provided in contact with the above-mentioned transparent conductive film (@), and supports the peripheral edge of the installation plate (2). This support body 0 is connected to an RF power source (not shown).

For example, a semiconductor wafer ■ is placed near the installation plate ■.
A support body (2) equipped with a lifting mechanism (0) such as an air cylinder, for example, is provided so as to fix the semiconductor wafer (2) to the installation plate (2) using the outer edge of the support body (2). Also.

Above the installation plate ■ is a quartz glass window (8) that allows the installation plate ■ to be heated to, for example, 300°C to 1000°C.
An infrared ray lamp is provided. Then, the reaction chamber near the installation plate■
For example, two exhaust ports (10) are provided on the upper wall,
This exhaust port (10) is connected to a vacuum pump (11
) For example, a turbo molecular pump or the like is connected.

Then, below the reaction chamber (2), two systems of annular gas inlet ports (12) each having a large number of minute outlet ports for flowing out film growth gas, carrier gas, etching gas, etc. are provided independently. There is. These gas inlets (12) are connected to a gas supply source via a flow rate control mechanism (13) such as a mass flow controller. Further, between the installation plate (■) and the gas inlet (12), there is a disc-shaped control plate (15) equipped with a linear movement mechanism (14) such as a stepping motor for controlling the flow of gas. It is provided.

Then, in order to carry the semiconductor wafer (■) into and out of the reaction chamber (■) via a gate valve (16) that can be opened and closed by lifting and lowering, for example, on one side of the reaction chamber (■), a hand that holds and conveys the wafer (■) in a telescopically rotatable manner is provided. Arm (17)
A confidential transport preliminary chamber (20) is provided with a built-in mounting table (19) that can be moved up and down on which cassettes (18) containing, for example, 25 wafers (25 wafers) are placed at predetermined intervals. It is.

Further, the operation of the film forming apparatus having the above configuration is controlled by a control section (21).

Next, a method of forming a film on a semiconductor wafer (1) using the above-mentioned film forming apparatus will be explained according to the flowchart shown in FIG.

A cassette (18) containing, for example, about 25 semiconductor wafers to be processed is placed on a lifting table (work 9) through an opening/closing opening (not shown) of the preliminary chamber (20) using a robot hand or a human hand. (A) At this time, the gate valve (
16) is in a closed state, and the pressure inside the reaction chamber ω has already been reduced to a desired low pressure state by the action of the vacuum pump (11). After setting the cassette (18), the opening/closing port (not shown) of the preliminary transport chamber (20) is closed to keep it confidential, and a vacuum pump (not shown) is used to open the reaction chamber α.
) to the same extent as (B).

Next, the gate valve (16) is opened (C), the desired low pressure state is maintained, and the height of the mounting table (19) is adjusted to hold the semiconductor wafer (■) on the extendable hand arm (17).
), a desired one is taken out from the cassette (18) and carried into the reaction chamber ω (D). At this time, the support (2) is being lowered by the lifting mechanism (2), and the wafer (2) is placed on the support (2) with the surface to be processed facing downward.

Then, the support body (2) is raised by the elevating mechanism 0, and the wafer (2) is placed between the installation plate (2) and the support body (2) (E).

When the installation of this semiconductor wafer ■ on the installation board ■ is completed,
The hand arm (17) is stored in the transfer preliminary chamber (20) and the gate valve (16) is closed (F).

Next, processing of the semiconductor wafer's surface to be processed is started.

First, a cleaning process is performed to etch and remove the native oxide film formed on the semiconductor wafer (2).

In this process, a vacuum pump (11) is used to maintain the inside of the reaction chamber ω at a desired low pressure state, for example, several tens to hundreds of mTorr.
The gas inlet (12) is opened while the exhaust is controlled by the flow rate adjustment mechanism (13), and the processing gas, such as Ar or NF, is uniformly diffused and supplied onto the wafer (2) while adjusting the flow rate to w4 with the flow rate adjustment mechanism (13). Then, an electric power of, for example, 400 (
W) is applied. Then, electric power is applied to the translucent conductive film formed on the surface of the quartz glass installation plate (■) connected to the conductor support (■), and since the reaction chamber ω is conductive, the transparent conductive film is A discharge occurs between the photoconductive rfA) and the processing gas supplied onto the semiconductor wafer (2) is turned into plasma. Etches at a rate of about 1 person/min. At this time, by applying the above power,
Since the support (2) is at a high temperature, the support (2) is controlled to be cooled to, for example, about 20° C. by a cooling mechanism (not shown).

After completing the etching process as described above, the semiconductor wafer is
A thin metal film is formed on the surface to be treated by chemical vapor deposition (H).

In this process, a vacuum pump (1
While controlling the exhaust in step 1), the quartz glass installation body (2) is irradiated with infrared light, which is heating light, from the IR lamp (2). As a result, since the quartz glass and the transparent conductive film coated on the quartz glass are transparent, the semiconductor wafer (2) placed on this installation body (3) is rapidly heated.

At this time, the temperature of the surface to be processed of the semiconductor wafer (2) is controlled using a pyrometer to control the infrared rays emitted from the wafer (2) to a temperature of, for example, 40 to 530 degrees Celsius using an R lamp (2), or a high-sensitivity thermocouple (2) is used. directly detects and controls the temperature of the wafer. Then, the gas inlet (12) is opened, and a film growth gas such as IIF, which constitutes a reaction gas, and a carrier gas such as H2 and Ar, which constitute a reaction gas, flow out using a flow rate control mechanism (13) to perform chemical vapor phase growth. . During this process, if the wafer 1 contact surface of the support 0 is made of ceramic or the like having low thermal conductivity, the heat distribution of the wafer 2 will be uniform and uneven processing can be prevented.

When chemical vapor phase growth is performed as described above, metal such as W
(Tungsten) film can be selectively deposited.

When the desired film formation is completed, the outflow of the reaction gas is stopped, the support body (2) is lowered with the wafer (2) supported by the lifting mechanism (2), and the gate valve (16) is opened (1).
Then, the semiconductor wafer (1) is carried out from the reaction chamber (2) by the extendable and rotatable hand arm (17) (J), and the gate valve (16) is closed (K) to complete the process. After this process is completed, check whether there are any unprocessed wafers in the cassette (18), and if there are any unprocessed wafers, perform the above etching process and chemical vapor deposition process again,
If there are no unprocessed wafers, the process ends.

As mentioned above, by using a quartz glass plate with a transparent conductive film formed thereon as a mounting plate on which a substrate to be processed, such as a semiconductor wafer, is placed, the transparent conductive film can be coated during the etching process for cleaning. By applying electric power, it is possible to uniformly transform the processing gas into plasma and perform etching processing stably. Also, during film formation, CVD processing can be performed without irradiating infrared light, which is heating light, from the installation plate side. This makes it possible to form a uniform and stable film.

The present invention is not limited to the embodiments described above, and for example, the surface on which the light-transmitting electrical film is formed on the quartz glass installation plate on which the semiconductor wafer is placed in the reaction chamber is formed on the surface on which the semiconductor wafer is placed. Alternatively, it may be formed on both sides, and in either case, the same effects as in the above embodiment can be obtained. Furthermore, the installation plate is not limited to one made of quartz glass with a transparent conductive film formed thereon, and any installation plate may be used as long as it is conductive and transparent. Furthermore, the material to be etched does not have to be a natural oxide film, and plasma etching may be performed as a pre-process of the CVD treatment to be performed later.
Furthermore, by adjusting the position of the disc-shaped control plate (15) provided between the installation plate ■ and the gas inlet (12) using the moving mechanism (14), the processing surface of the installed semiconductor wafer ■ The flow of the reaction gas can be controlled so that the reaction gas comes in contact with the reactor gas uniformly.

Further, unnecessary films need not be removed by plasma etching, but any means that can remove unnecessary films may be used.
Furthermore, it goes without saying that any kind of treatment may be used for film formation by CVD treatment, such as plasma (-CVD treatment).

Furthermore, when forming a thin film such as a W (tungsten) film by chemical vapor deposition on the processing surface of a substrate to be processed, such as a semiconductor wafer Although it is a small amount, the W film may adhere and accumulate.

It is also possible to self-clean the W film deposited on the wall surface of the reaction chamber (2) by plasma etching. Next, this self-cleaning process will be explained.

With no substrate to be processed, such as a semiconductor wafer (2), placed on the installation plate (2), the interior of the reaction chamber (ω) is maintained at a desired low pressure, for example, several tens to hundreds of mmT. Vacuum pump (11) to keep it at rr
Exhaust control is performed at the gas inlet (12) in this exhaust state.
) is opened and a processing gas, for example, NF3, is supplied into the reaction chamber ω while adjusting the flow rate with a flow rate regulator (13). Then, a power of 400 (W), for example, is applied from an RF main power source (not shown) to the conductor support body (2) connected to the installation plate (2). As a result, electric power is applied to the transparent conductive film (2) formed on the surface of the quartz glass installation plate (2) connected to the support 0 of the conductor, and the reaction chamber (2) becomes conductive. Therefore, a discharge occurs between the translucent conductive film (A) and the N, which is the processing gas supplied into the reaction chamber ω.
F is turned into plasma, and the plasma-formed gas plasma-etches W [attached and deposited on the wall surface of the reaction chamber (2).

The self-cleaning process of the reaction chamber by plasma etching as described above is performed every time a certain amount of W film is deposited in the reaction chamber. For example, it is set in advance to be performed every time a predetermined number of substrates are subjected to CVD processing. Furthermore, since the amount deposited on the wall surface of the reaction chamber varies depending on the type of gas used in the CVD process, it goes without saying that the self-cleaning timing may be selectively determined as appropriate.

By performing self-cleaning at predetermined intervals as described above, the interior of the reaction chamber can be kept clean at all times, and the W film etc. deposited in the reaction chamber can be prevented from turning into dust and having an adverse effect on the CVD process. It can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a film forming apparatus for explaining an embodiment of the method of the present invention, FIG. 2 is an enlarged view of an installation plate on which a substrate to be processed is placed in the apparatus of FIG. 1, and FIG. FIG. 3 is a flow diagram for explaining film formation by the apparatus shown in the figure. 1... Reaction chamber 2... Semiconductor wafer 3.
... Installation board 4 ... Transparent conductive film 5 ...
Support 9...IR clamp applicant Tokyo Electron Ltd. Figure 1 Figure 2

Claims (1)

[Claims] a means for removing an unnecessary film formed on at least the to-be-processed surface of the to-be-processed substrate placed in the processing container; and a method for growing a film on at least the to-be-processed surface of the to-be-processed substrate in the processing container after this means. 1. A film forming method comprising means for forming a desired film using a gas.