JPH0729832A - Method and system for depositing film - Google Patents

Abstract

PURPOSE:To remove particles generated during the filming process using a general purpose method. CONSTITUTION:A laser light source 8 and a rotary polygon mirror 6 for directing a laser beam into a filming chamber 1 in a CVD system while varying the optical path thereof periodically are disposed on the outside of the filming chamber 1. A laser beam introduced into the filming chamber 1 through a silicon window 5 scans on a plane in parallel with the main plane of a wafer W in the vicinity thereof and imparts optical pressure to particles having size larger than the wavelength thereof thus shifting the particles in the advancing direction of light. This process is substantially independent from the chemical composition of particle. A high output CO2 laser light source is suitable employed as the light source 8. Since the deposition substance pertaining to the filming has particle size significantly smaller than the wavelength, the particles can be removed simultaneously without causing any trouble in the filming process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus and method for forming a thin film on a substrate by using a thin film forming technique such as CVD (Chemical Vapor Deposition), sputtering, vapor deposition, etc. The present invention relates to a technique for improving yield and reliability of devices by removing particles generated in the process of film in real time.

[0002]

2. Description of the Related Art The design rules of VLSI are becoming more and more miniaturized, and in the quarter micron process required for processing of 64M DRAM class, physical and chemical limits are beginning to be seen in the process technology itself. Under such circumstances, the product yield and reliability of the VLSI will largely depend on the cleanliness of the semiconductor manufacturing process. In fact, it is estimated that 80 to 90% of the cause of device failure of 64M to 256M DRAM will be caused by particle adhesion and metal contamination on the wafer.

Among all the processes included in the semiconductor manufacturing process, in a film forming process using a film forming device such as a CVD device, a sputtering device, or a vapor deposition device, chemical / physical phenomena occurring in the film forming chamber generate particles and wafers. Since it is closely related to the adhesion to the surface, it is the most difficult area to prevent particles. That is, because of the principle of the process, there is always a possibility that a film-forming substance or an intermediate product will be deposited as particles on the wafer at the same time as film formation.

As a countermeasure against particles, it goes without saying that adopting a process that does not generate particles itself is the best. However, in practice, this is not always easy, and in practice, there is often adopted a policy in which generated particles are not attached.
As one of the in-situ cleaning methods according to this policy, for example, a method of constantly removing particles generated in the film forming chamber of the CVD apparatus from the film forming chamber by performing plasma cleaning between the film forming steps. Promising.

[0005]

However, since the above-mentioned plasma cleaning is, so to speak, a process of removing deposits in the film forming chamber using an etching gas, it is necessary to introduce a new chemical reaction into the manufacturing process. become. For this reason, the chemical reaction must be thoroughly considered so as not to introduce new pollution. In fact, when performing plasma cleaning using flon gas after deposition of the SiO ₂ film, cases in which F atoms are incorporated have been reported in the SiO ₂ film.

It is possible to maintain high cleanliness by inserting plasma cleaning between each film formation, but this naturally lowers the throughput.
The frequency of cleaning must be decided in consideration of economical efficiency. Further, in a film forming apparatus in which the plasma generation region is originally limited to the vicinity of the wafer from the viewpoint of particle contamination reduction, it is necessary to change the discharge condition in order to remove particles adhering to the region other than the wafer. , It is difficult to optimize the conditions.

Particles are also generated by chipping of the wafer itself or its supporting member, or abrasion of the movable portion of the wafer transfer mechanism. Particles of various compositions like this are
It cannot be removed by cleaning. Moreover, it should be appreciated that plasma cleaning can only be employed in devices capable of generating plasma. That is, it cannot be applied to atmospheric pressure CVD equipment, vapor deposition equipment, and sputtering equipment.

Therefore, the present invention proposes a film forming apparatus and a film forming method which have excellent versatility and can be applied to all film forming processes and can effectively remove particles without lowering the throughput. With the goal.

[0009]

The film forming apparatus of the present invention is proposed in order to achieve the above-mentioned object, and a film forming chamber and a deposition material which is a constituent material of a thin film in the film forming chamber. In a plane in the vicinity of and parallel to the main surface of the substrate placed on the stage, and a stage for placing the substrate on which the depositable substance is deposited. And a light beam scanning means for scanning the light beam.

The film forming chamber does not necessarily have to be evacuated to a high vacuum, and may not necessarily generate plasma.

The light beam can be appropriately selected from those which do not substantially interact with the film forming atmosphere. This is because the light energy is not attenuated and the source gas for film formation is not decomposed or changed. In particular, a CO ₂ laser beam or a YAG (yttrium-aluminum-garnet) laser beam is preferable from the viewpoint that a high power type is available. The CO ₂ laser can continuously oscillate in a wide output range from less than 1 W to several hundreds of thousands W. 10.4 μ
m and 9.4 μm infrared wavelengths have important oscillations. Similarly, the YAG laser can continuously oscillate in the output range up to several hundred W, and the oscillation wavelength is 1.0 of Nd atom.
It is 6 μm. These lasers are also capable of pulsing at higher power levels.

Further, when a film is formed using this film forming apparatus, the particles generated in the film forming chamber are scanned with a light beam in a plane in the vicinity of the main surface of the substrate and parallel to the main surface. While being removed by doing so, the depositable substance is deposited on the substrate to form a thin film.

[0013]

The principle of particle removal in the present invention is to move particles by the pressure of light. Here, the particles that can be removed by the pressure of light are particles having a particle size larger than the wavelength of light.
Particles with a particle size smaller than the wavelength of light do not scatter light and therefore do not move. That is, the particle removal efficiency in the present invention is determined by the relationship between the wavelength of the light beam used and the particle size of the particles and the mass of the particles, and does not substantially depend on the chemical composition of the particles. Therefore, the present invention can be widely applied to a film forming process or a film forming apparatus that requires particle removal.

By the way, the particle size of which particles can be removed depends on the wavelength of the light beam used. Therefore, if attention is paid only to this point, the smaller the particle size, the smaller the particles that can be removed. . However, since the pressure of light includes the term of energy density, it is necessary to use a light beam that can obtain a high output to some extent. Further, when a short-wavelength beam such as in the ultraviolet region is used, there is a risk of decomposing and deteriorating the raw material gas and the depositable substances involved in film formation in the vapor phase. The CO ₂ laser beam and the YAG laser beam are selected from such a viewpoint, and each can remove particles up to about 1 μm in diameter. On the other hand, the depositable substances such as atoms, molecules and clusters involved in film formation in a normal film formation process are particles having a particle size much smaller than this,
Even if the light beam irradiation is performed during film formation,
There is no fear that the depositable substance will be removed from the vicinity of the substrate, and the film can be formed as usual.

Based on such a principle, according to the film forming method of the present invention, it is possible to perform particle removal by light beam scanning simultaneously with the progress of the film forming process. Therefore, particles generated by a chemical factor or a hardware factor during film formation are laterally displaced in the vicinity of the main surface of the substrate and do not adhere to the substrate. As a result, it is possible to perform the real-time particle removal at the forefront of film formation more efficiently than the conventional in-situ cleaning in which plasma cleaning is performed at any time during the film forming process.

[0016]

EXAMPLES Specific examples of the present invention will be described below. First, FIG. 1 shows a structural example of a CVD apparatus to which the present invention is applied. In the figure, (a) is a schematic sectional view, and (b) is a top view in the vicinity of the wafer W. This CVD apparatus includes a shower head type gas supply pipe 2 for introducing a gas in the direction of arrow A and a stage 4 for mounting a wafer W inside a film forming chamber 1 usually made of stainless steel or aluminum. Are vertically opposed to each other. The inside of the film forming chamber 1 is exhausted in the direction of arrow B through the exhaust hole 3 in order to maintain a predetermined gas pressure and to discharge unreacted gas and byproducts. A heater (not shown) may be built in the stage 4 so that the wafer W can be heated if necessary. Further, this apparatus can be used as an atmospheric pressure CVD apparatus with the configuration shown in the drawing, but the film forming apparatus of the present invention is not limited to this, and for example, the inside of the film forming chamber 1 is evacuated to a high vacuum, Gas supply pipe 2
CV by applying RF electric field between the stage and the stage 4
The configuration may be such that D is performed.

A quartz window 5 is provided on the side wall surface of the film forming chamber 1. Further, outside the film forming chamber 1, a laser light source 8 and a rotating shaft 7 corresponding to the positions where the quartz window 5 is arranged.
A polygon mirror 6 (a hexagonal prism in the illustrated example) that rotates in the direction of the arrow D around is arranged. The laser light from the laser light source 8 is reflected by the polygon mirror 6 and is irradiated into the film forming chamber 1 through the quartz window 5. At this time, the laser light in the film forming chamber 1 travels parallel to the main surface of the wafer W in the direction of arrow C shown by a solid line as an example. However, the optical path at this time is the polygon mirror 6
The laser beam scans the entire area of the wafer W and is scanned with laser light as shown by the broken line arrow in the figure.

In such a structure, the raw material gas for film formation is supplied from the gas supply pipe 2 to perform a predetermined film formation on the wafer W, while the vicinity of the wafer W is two-dimensionally scanned by the laser beam. Remove particles. This laser light does not hinder the movement of the particles of the deposition material involved in film formation, and moves only the particles having the particle diameter equal to or larger than the wavelength thereof to the outside of the wafer W. The moved particles are carried on the exhaust flow in the film forming chamber 1 and discharged from the exhaust holes 3 to the outside, so that they do not adhere to the wafer W.

Since the laser beam heats the wall material of the film forming chamber 1, a cooling mechanism suitable for the wall material of the film forming chamber 1 or a reflecting mirror for letting the laser light escape to the outside of the film forming chamber 1. Is preferably provided.

Next, assuming that the particles are spheres, the acceleration of the particles when the particles are removed using a laser beam will be calculated. Now the laser output E = 1 × 10
³ (W), beam diameter d = 1 × 10 ⁻³ (m), scan width w = 200
Assuming × 10 ⁻³ (m), the energy density I of light is expressed by the following equation (i).

I = E / w · d = 1 × 10 ³ (W) / 200 × 10 ⁻³ (m) × 1 × 10 ⁻³ (m) = 5 × 10 ⁶ (W / m ² ) ... (i )

Then, the pressure p of light is calculated by the following equation (ii) using the energy density I and the speed of light c [= 3 × 10 ⁸ (m / s)].
It is represented by. p = a · I / c = a × 5 × 10 ⁶ (W / m ² ) / 3 × 10 ⁸ (m / s) = a × 1.67 × 10 ^-2 (Pa) (ii) where a Is a constant determined by the light reflectance of the object and has a value of 1 ≦ a ≦ 2. black body when a = 1, a =
The case of 2 corresponds to a perfect reflector, and an ordinary object has an intermediate value. Therefore, the range of the value of the light pressure p is expressed by the following equation (iii).

1.67 × 10 ^-2 (Pa) <p <3.33 × 10 ^-2 (Pa) (iii)

The acceleration α received by a spherical body (particle) having a radius r and a density ρ due to the light pressure p is expressed by the following equation (iv). α = F / M = pπR ² / ρπR ³ = p / ρR (iv) where F is the force (N) and M is the mass of the sphere (kg).

Here, the spherical body is made of SiO 2.₂Dense assuming particles
Degree ρ = 2.2 g / cm³[= 2.2 x 10 ³(Kg / m³)〕When
Every 1 μm particle diameter [ie radius R = 0.5 x 10^-6(M)
 ] And a particle size of 10 μm [that is, radius R = 5 × 10
^-6(M)] based on the above equation (iv)
Calculated as follows:When the particle size is 1 μm 15.2 (m / s²) <Α <30.4 (m / s²)When the particle size is 10 μm 0.15 (m / s²) <Α <3.04 (m / s²) From this result, if the particle diameter is several μm,
It is known that the pressure of
Light The effect of light pressure is greater for fine particles.

Here, using the CVD apparatus shown in FIG.
CO having the above output value and beam diameter₂Laser beam
S while scanning above the wafer W with the above scanning width
iO ₂When the film was formed, particles caused
We were able to significantly reduce vice defects.

The present invention is not limited to the above-described embodiments, but can be similarly applied to the apparatus and method used for sputtering or vapor deposition. Further, although the description so far has been made only for the film forming apparatus, the reduction of particles is an important issue in the field of dry etching. If a mechanism for laser beam irradiation and scanning as described above is also mounted in a dry etching apparatus, it is possible to perform dry etching while performing extremely sophisticated particle control.

[0028]

As is apparent from the above description, according to the present invention, it is possible to perform film formation by a method with extremely high versatility while removing particles in real time. Since the structure of the film forming apparatus is not so complicated, it is highly economical. Therefore, the present invention is extremely useful, for example, in improving the yield and reliability of semiconductor devices.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a CVD apparatus to which the present invention is applied, in which (a) is a schematic sectional view and (b) is a top view in the vicinity of a wafer.

[Explanation of symbols]

 1 ... Film forming chamber 2 ... Gas supply pipe 3 ... Exhaust hole 4 ... Stage 5 ... Quartz window 6 ... Polygon mirror 8 ... Laser light source W ... Wafer

Claims (3)

[Claims] 1. A film forming chamber, a film forming means for generating a depositable substance that is a constituent material of a thin film in the film forming chamber, a stage for mounting a substrate on which the depositable substance is deposited, A film forming apparatus comprising a light beam scanning means for scanning a light beam in a plane in the vicinity of the main surface of a substrate placed on the stage and parallel to the main surface. 2. The film forming apparatus according to claim 1, wherein the light beam is either a CO ₂ laser beam or a YAG laser beam. 3. The film forming apparatus according to claim 1, wherein particles generated in the film forming chamber are provided with a light beam in a plane in the vicinity of and parallel to the main surface of the substrate. A film forming method, comprising depositing the depositable substance on a substrate to form a thin film while removing the depositable substance by scanning.