JPH07150359A - Cvd device using liquid starting material - Google Patents

Abstract

PURPOSE:To rapidly form a homogeneous thin film by vaporizing the liquid starting material into a gaseous starting material in the vaporizer, accumulating the gaseous starting material in the gaseous starting material reserving section in an amount required for performing at least one vapor deposition and transferring the gaseous starting material from the reserving section to the vapor deposition chamber at the time of performing the vapor deposition. CONSTITUTION:A carrier gas is bubbled into the liquid starting material 14 by drawing back the piston 19 of the gaseous starting material diffusion pump 17 in the thermostatic bath 16 through using the motor 20. Thus the gaseous starting material obtained by vaporizing the liquid starting material 14 is accumulated in the pumping chamber 18 of the gaseous starting material diffusion pump 17. The amount to be accumulated of the gaseous starting material is adjusted to that larger than the required amount for performing one vapor deposition. When the prescribed amount of the gaseous starting material is accumulated, the motor 20 is stopped and the gaseous starting material is maintained in the state for about several minutes to diffuse it in the pumping chamber 18 and to homogenize it. Thereafter, at the end of this prescribed maintaining time of the starting material, the valve 1 is opened, and the accumulated gaseous starting material is transferred at a constant flow rate to the vapor deposition chamber 21, that is evacuated to a high vacuum beforehand, by using the piston 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CVD apparatus (chemical vapor deposition apparatus) using a liquid substance as a raw material.

[0002]

2. Description of the Related Art A CVD apparatus is widely used for forming a thin film of a semiconductor or the like, but a liquid source CVD (liquid source CVD) apparatus which uses a liquid as a raw material instead of a conventional gas raw material has recently been drawing attention. The reason is as follows. In DRAMs that are becoming more highly integrated, increasing the charge storage capacitance in the circuit is an essential element. As a measure against this,
Since there is a limit only in the method of complicating the capacitor structure to increase the effective area, it is necessary to switch the capacitor dielectric itself to a material having a higher dielectric constant. Therefore, a high dielectric film such as tantalum pentoxide (Ta2O5) or lead zirconate titanate (PZ) having a larger dielectric constant is used.
T), the use of ferroelectric films such as barium strontium titanate (BST) has been demanded. In addition, TEOS (Tetra-Ethyl Ortho Silicate) oxide film has good step coverage (adhesion) and adhesion which is not obtained by the conventional film formed by using monosilane or dichlorosilane. It is considered to be indispensable for flattening the interlayer insulating film in a process involving a severe step such as DRAM after the bit. Of these film raw materials, Ta2O5 and TEOS-SiO2 are both liquids, so that it is suitable to use a liquid raw material CVD apparatus. Further, although the raw materials for forming a thin film such as PZT and BST are solids, they can be made into solutions by using appropriate solvents, respectively, and these are also used as vapor deposition materials by using a liquid raw material CVD apparatus. be able to. Further, since the liquid source CVD apparatus does not use a special high pressure gas, it has a feature that the process safety can be ensured.

In the liquid source CVD apparatus, three methods shown in FIG. 5 are mainly used as a method for generating a vapor deposition gas to be fed into the vapor deposition chamber. 5A and 5B are both called a bubbling method, which is a method of ejecting a carrier gas (Ar, N2, etc.) inside the liquid raw material 62 to promote vaporization. 5A, the mass flow controller (MFC) 61 controls the flow rate of the carrier gas, and the method of FIG. 5B controls the flow rate of the raw material gas. FIG. 5C is called a baking method, and the liquid raw material is heated to obtain vapor.

[0004]

For example, in the case of pentaethoxytantalum (Ta (OC2H5) 5), its vapor pressure is low, so it is necessary to raise the temperature to some extent in order to vaporize it, but only by heating. If the temperature is raised until an appropriate film formation rate is obtained, thermal decomposition will occur. In such a case, the bubbling method must be used. Atmospheric pressure TEO
The same applies to S-O3. On the other hand, the bubbling method is inferior to the baking method in terms of reproducibility of film formation because it is necessary to accurately control each parameter of the raw material temperature, the flow rate of the carrier, and the total pressure of the raw material tank 63. Also, MFC6
The flow rate of the carrier gas or the raw material gas containing the carrier gas is controlled by 1 and the amount of the raw material gas itself introduced into the vapor deposition chamber is not controlled. Therefore, there is a drawback that the characteristics of the vapor deposition film formed on the surface of the object to be processed (sample) become nonuniform in the thickness direction. In particular, when a plurality of liquid raw materials are mixed and sent to the vapor deposition chamber to form a composite film on the sample surface, there arises a problem that the mixing ratio of each raw material changes in the film thickness direction.

The present invention has been made to solve the above problems, and an object thereof is to provide a liquid raw material C capable of forming a uniform film rapidly.
It is to provide a VD device.

[0006]

A liquid source CVD apparatus according to the present invention made to solve the above problems is produced by a) a source vaporizing means for vaporizing a liquid source and b) a source vaporizing means. At least 1 source gas
An amount of raw material gas holding means for holding for a predetermined time by an amount necessary for vapor deposition of a single time, and c) a raw material gas feeding means for feeding the raw material gas held in the raw material gas holding means to the vapor deposition chamber at a predetermined speed, It is characterized by including.

Further, in the case of producing a mixed vapor deposition film of a plurality of liquid raw materials, a) a plurality of raw material vaporizing means for individually vaporizing a plurality of liquid raw materials and b) a plurality of raw material vaporizing means The source gas mixture holding means for collecting the source gas of (1) and holding it for a predetermined time at least in an amount necessary for at least one vapor deposition, and c) depositing the source gas held by the source gas mixture holding means at a predetermined rate. And a means for feeding the raw material gas to the chamber.

[0008]

The raw material vaporizing means vaporizes the liquid raw material by blowing (bubbling) or heating (baking) the carrier gas into the liquid raw material to generate the raw material gas.
Of course, the raw material vaporizing means may be vaporized by other methods. The raw material gas holding means holds the raw material gas in an amount necessary for at least one vapor deposition for a predetermined time. Generally, when a liquid material is vaporized, its vaporization rate is often not constant in time. The raw material gas holding means collectively holds the raw material gas generated inhomogeneously in time as described above in an amount necessary for at least one vapor deposition, thereby giving a sufficient diffusion time to the raw material gas to make it uniform. Produces raw material gas. Therefore, the raw material gas feeding means feeds the raw material gas held in the raw material gas holding means to the vapor deposition chamber at a constant rate, for example, to perform vapor deposition at a constant rate, and the characteristics of the deposited film in the thickness direction are improved. It will be constant. Further, by controlling the feed rate of the raw material gas by a predetermined program, it is possible to obtain a vapor deposition film having desired inclination characteristics in the thickness direction.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of a liquid source CVD apparatus which is an embodiment of the present invention will be described with reference to FIG. The liquid source CVD apparatus of this embodiment is characterized in that a pump 17 for diffusing a source gas is provided between the liquid source vaporizer and the vapor deposition chamber. First, while the motor 20 pulls the piston 19 of the raw material gas diffusion pump 17, the carrier gas 13 (Ar, N2, etc.) is bubbled through the liquid raw material 14 in the raw material tank. As a result, the vaporized liquid raw material 14 is accumulated in the pump chamber 18 of the raw material gas diffusion pump 17. Depending on the type of liquid raw material, heating may be performed during bubbling. The amount of the source gas accumulated in the source gas diffusion pump 17 is calculated by the amount necessary for one vapor deposition performed in the vapor deposition chamber 21 (that is, calculated from the vapor deposition conditions such as the volume, pressure, vapor deposition time of the vapor deposition chamber 21). The total flow rate of the raw material gas). For example, assuming that the flow rate of the raw material gas introduced into the vapor deposition chamber 21 is about several tens of ml / min and the processing time is about several minutes to several tens of minutes, the raw material gas diffusion pump 17 has a maximum of It is sufficient to prepare one with a volume of several hundred ml to several liters.

The motor 20 is stopped when more than the amount of raw material gas required for one vapor deposition is accumulated in the pump chamber 18, and the raw material gas is kept in the pump chamber 18 for a few minutes as it is. deep. When vaporized by bubbling in the raw material tank, the vaporization rate of the liquid raw material 14 is not always constant in time, and the concentration of the generated raw material gas varies. However, as in the present embodiment, once the pump chamber 18
By keeping the inside of the pump for a predetermined time, the raw material molecules in the raw material gas are sufficiently diffused in the pump chamber 18 and the pump chamber 1
The raw material gas in 8 is homogenized.

The vapor deposition chamber 21 includes a rotary pump (RP) 2
3 and a turbo molecular pump (TMP) 24 are evacuated to a high vacuum in advance. When the holding in the pump chamber 18 for a predetermined time is completed, the valve V1 between the source gas diffusion pump 17 and the vapor deposition chamber 21 is opened, and the motor 20 moves the piston 19 at a constant speed. As a result, the raw material gas in the pump chamber 18 is supplied into the vapor deposition chamber 21 at a constant flow rate.

Details of the vapor deposition chamber 21 are shown in FIG. The source gas introduction path 49 is provided in the upper electrode 48, and the source gas is discharged into the vapor deposition chamber container 47 from a large number of small holes 51 provided in the lower portion of the upper electrode 48. The pressure inside the vapor deposition chamber container 47 is constantly detected by the pressure gauge 22, and the rotary pump 23 exhausts air from the exhaust port 56 so as to maintain a predetermined pressure. The sample 53 is placed on the lower electrode 54 and is heated to a predetermined temperature (500 to 800 ° C.) by the heater 55.
To be heated. As a result, the source gas is deposited on the surface of the sample 53. When plasma assist is required, high frequency power is supplied from the high frequency power supply 45 to the upper electrode 48 via the matching circuit 46 in this state. Incidentally, 50 is an insulator for insulating the upper electrode 48 from the container 47, and 52 is an auxiliary ring for making the flow of the source gas in the container 47 uniform.

The pump chamber 18 for holding the raw material gas and the passage, valve, etc. from the pump chamber 18 to the vapor deposition chamber 21 are put in a constant temperature bath 16 and kept at a temperature of about 100 to 250 ° C. This prevents the raw material gas from condensing and prevents the concentration change of the raw material gas introduced into the vapor deposition chamber 21 and the clogging of valves and the like.

Reference numeral 12 is a diluent gas supply source, which is prepared to dilute the raw material gas in the pump chamber 18 with Ar, N 2 or the like as needed. Further, 11 is a purge line for releasing the old source gas when changing the type of source.

As the vaporizer of the liquid raw material, a bubbling system shown in FIG. 1 and a baking system shown in FIG. 2 can be used. In the apparatus of FIG. 2, the carrier gas is supplied from the carrier gas source 32 to the vaporization chamber 35.
While being introduced into the inside, the liquid raw material is injected into the vaporization chamber 35 by the microsyringe 33 and heated by the heater 36. Also in this case, the vaporized raw material is accumulated in the pump chamber 18 until it reaches a predetermined amount (more than the amount required for one vapor deposition) and is held for a predetermined time.

In the apparatus shown in FIG. 1, the raw material tank containing the first liquid raw material is connected to 17, the raw material gas is accumulated in the pump chamber 18, and then the raw material tank containing the second liquid raw material is connected to 17. Then, similarly, by feeding the raw material gas into the pump chamber 18, a mixed raw material gas can be obtained.
In the liquid source CVD apparatus according to the present embodiment, the raw material gases thus separately generated are once accumulated in the pump chamber 18 and are held for a predetermined time, so that both raw material gases are sufficiently diffused and mixed with each other. It Therefore, the source gas supplied to the vapor deposition chamber 21 becomes homogeneous and a homogeneous vapor deposition film can be obtained.

Further, as shown in FIG. 3, a plurality of vaporizers 41, 42 may be provided in parallel so that the source gases are fed into the pump chamber 18 at the same time.

[0018]

In the liquid source CVD apparatus according to the present invention,
In order to hold the vaporized raw material once and give it a diffusion time,
The raw material gas is sufficiently homogenized beforehand. And then
Since the homogenized source gas is sent to the vapor deposition chamber in a self-sustaining manner, a uniform vapor deposition film can be obtained or the configuration of the vapor deposition film can be precisely controlled. In particular, when a plurality of raw materials are used, the mixing ratio can be made constant over time, so that a mixed vapor deposition film without composition unevenness can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire liquid source CVD apparatus that is an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a liquid source vaporizer portion of a liquid source CVD apparatus according to an embodiment.

FIG. 3 is a schematic configuration diagram of a liquid source vaporizer portion of a multiple source liquid source CVD apparatus which is another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a vapor deposition chamber portion of the liquid source CVD apparatus according to the embodiment.

FIG. 5 is an explanatory diagram of a method of vaporizing a liquid source material in a conventional liquid source CVD apparatus.

[Explanation of symbols]

11 ... Purge line 12 ... Diluting gas source 13 ... Carrier gas source 14 ... Liquid raw material 16 ... Constant temperature bath 17 ... Raw material gas diffusion pump 18 ... Pump chamber 19 ... Piston 20 ... Motor 21 ... Deposition chamber 22 ... Pressure gauge 23 ... Rotary Pump 32 ... Carrier gas source 33 ... Micro syringe 35 ... Vaporization chamber 36 ... Heater 41, 42 ... Vaporizer 43, 44 ... Mass flow controller

Claims (2)

[Claims] 1. At least one of a) a raw material vaporizing means for vaporizing a liquid raw material, and b) a raw material gas produced by the raw material vaporizing means.
An amount of raw material gas holding means for holding for a predetermined time by an amount necessary for vapor deposition of a single time, and c) a raw material gas feeding means for feeding the raw material gas held in the raw material gas holding means to the vapor deposition chamber at a predetermined speed, A liquid source CVD apparatus comprising: 2. An amount required for at least one vapor deposition, comprising: a) a plurality of raw material vaporizing means for individually vaporizing a plurality of liquid raw materials, and b) a plurality of raw material gases generated by the plurality of raw material vaporizing means. And a raw material gas feed means for feeding the raw material gas held in the raw material gas mixture holding means to the vapor deposition chamber at a predetermined speed. A liquid raw material CVD apparatus.