JP3134942B2 - Wafer stage pretreatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing apparatus used for forming a thin film such as an insulating film on a substrate or for plasma etching, wherein an electrostatic chuck is attached to a holding mechanism of a wafer stage for holding the substrate. The present invention relates to a pretreatment method for an electrostatic chuck surface for cleaning a flat surface of an electrostatic chuck prior to adsorption and holding of a substrate to be processed on the surface in an ECR plasma CVD apparatus used.

[0002]

2. Description of the Related Art First, an outline of an ECR plasma CVD apparatus to which a wafer stage pretreatment method according to the present invention is applied will be described.

[0003] An ECR plasma CVD apparatus employs an ECR plasma CVD method, that is, a method in which a gas is introduced into a magnetic field having a predetermined intensity, and a microwave having a frequency corresponding to the magnetic field intensity is incident on the gas, thereby converting the energy of the microwave into the gas. A film formation method for forming a film by conducting resonance absorption, thereby guiding a plasma generated at high density on a substrate together with a reaction gas,
FIG. 3 shows a configuration example of the device. A plasma generation chamber 5 formed as a semi-open microwave resonator having a microwave introduction window 2 and a plasma extraction window 7 at both ends is coaxially surrounded by a main magnetic coil 4, and a current flowing through the coil 4 is formed. Is adjusted, a magnetic field region that satisfies the electron cyclotron resonance (hereinafter, referred to as ECR) condition is formed near the microwave introduction window in the plasma generation chamber 5 . A reaction chamber 6, which is adjacent to the plasma generation chamber 5 and whose internal space communicates with the internal space of the plasma generation chamber 5 through a plasma extraction window 7, is provided. As a wafer stage for holding a substrate in the reaction chamber, a holding mechanism is provided. Although not shown here, a wafer stage 11 using an electrostatic chuck 10 is capable of moving in an axial direction in a reaction chamber.
6 is arranged on the upper surface side. An auxiliary magnetic coil 12 is arranged outside the reaction chamber 6 on the upper side of the reaction chamber, and forms a mirror magnetic field or a cusp magnetic field in the apparatus in combination with the main magnetic coil 4 depending on the operation purpose of the apparatus. When an SiO ₂ film is formed on the substrate as an insulating film, for example, an ECR magnetic field region is formed in the plasma generation chamber 5 and microwaves are introduced, and then N ₂ O is introduced from the first gas introduction system 3 into the plasma generation chamber 5 . Or O ₂
The gas is introduced, and a plurality of gas outlets having the same diameter formed at equal intervals in the circumferential direction are formed in the reaction chamber 6 from the second gas introduction system 8 on the inner diameter side of the annular gas nozzle 8a at equal intervals in the circumferential direction. When the SiH ₄ gas is introduced in a gas amount, the N ₂ O or O ₂ gas plasmatized in the plasma generation chamber 5 moves into the reaction chamber 6 along the lines of magnetic force of the diverging magnetic field formed by the main magnetic coil and reacts. The SiH ₄ gas in the chamber 6 is decomposed and activated, and an SiO ₂ film having a uniform thickness is formed on the surface of the substrate 9 in a cusp magnetic field formed in the reaction chamber 6 .

[0004] In this film formation by the ECR plasma CVD method, high-activity, high-density plasma generated in a plasma generation chamber is used, so that low-temperature film formation is possible.
At the time of forming the SiO ₂ film, a high-frequency power supply is connected to a suction internal electrode constituting the electrostatic chuck 10 via a capacitor, although not shown in the figure, and a negative bias potential is generated on the surface of the substrate 9. , The ions in the plasma are accelerated,
Densification of the film due to ion bombardment, improvement in film coverage at the stepped portion due to sputtering, or flattening of a film in a recess between wirings by simultaneous progress of sputtering and film formation are possible.

By the way, in the ECR plasma CVD apparatus configured as described above, by repeatedly forming a film on a substrate, a reaction product is deposited on the inner wall surface of the apparatus in a film form, and the film thickness exceeds a certain thickness. When peeling occurs, particles generated at the time of peeling adhere to the thin film on the substrate surface and contaminate the thin film.Thus, after repeating film formation a certain number of times, the inside of the device is opened to the atmosphere to take out the internal structure, The inner wall surface and the removed structure are cleaned. At this time, the electrostatic chuck is cleaned again by wiping off the adhered substance on the surface with alcohol or the like, or by cleaning with a cleaning liquid, and re-introduced into the apparatus in a state where the holding power of the surface is restored.

[0006]

However, the electrostatic chuck has a weak holding power for the substrate, and does not adsorb the substrate even if the surface is cleaned as described above, or the substrate drops after the adsorption. When the SiO ₂ film is formed, there has been a problem that the film forming speed greatly varies for each film formation.
Conventionally, in order to recover the attraction force of the electrostatic chuck and reduce the variation in the film forming speed, after the electrostatic chuck has been incorporated into the apparatus, vacuuming has been performed for several hours. For this reason,
There is a problem that the improvement of the operation rate of the apparatus is restricted.

An object of the present invention is to provide a pretreatment method for an electrostatic chuck which shortens the evacuation time (time left in vacuum) or does not require the evacuation time.

[0008]

According to the present invention, a microwave introduction window and a plasma extraction window are provided on both end surfaces to generate electron cyclotron resonance with microwaves. A reaction in which a plasma generation chamber in which a magnetic field region to be formed is formed, gas supply means communicating with the plasma generation chamber through a plasma extraction window to blow out a reaction gas into the inside, and a wafer stage holding a substrate to be processed are arranged. And an electrostatic chuck is used for the substrate holding mechanism of the wafer stage.
A wafer stage pretreatment method for cleaning a flat surface of said electrostatic chuck of a CR plasma CVD apparatus prior to adsorption and holding of a substrate to be treated on said surface, wherein said apparatus is an apparatus formed and deposited in a plasma processing step. Dirt on the inner wall surface and internal structures is cleaned by opening the inside of the apparatus to the atmosphere, and dirt on the surface of the electrostatic chuck is placed in a plasma generation chamber in a vacuum prior to adsorption and holding of the substrate to be processed on the surface. Ar, He
Plasma is generated by introducing an inert gas such as H ₂ , O ₂ , N ₂ , or the like, or a simple gas of diatomic molecules that does not generate a reaction product with the surface material of the electrostatic chuck, such as H ₂ , O ₂ , N _2. The surface of the chuck is irradiated for cleaning.

In this case, it is preferable to irradiate the surface of the electrostatic chuck with plasma while applying a high frequency bias to the electrostatic chuck.

[0010] It is also possible to irradiate the surface of the electrostatic chuck with plasma while simultaneously introducing a gas to be converted into plasma in the plasma generation chamber into the plasma generation chamber and the reaction chamber.

The cleaning of the surface of the electrostatic chuck by each of the above methods is carried out by maintaining the gas pressure in the plasma generation chamber and the reaction chamber at a high vacuum of 1 × 10 ^{−4 to} 5 × 10 ⁻³ Torr, It is more preferable that an axial mirror magnetic field is formed in the room.

[0012]

[Function] As described above, an inert gas such as Ar, He, or a single gas of diatomic molecules that does not generate a reaction product with an electrostatic chuck surface material, such as H ₂ , O ₂ , N ₂ , in the plasma generation chamber. Is introduced to generate plasma, and this plasma is irradiated to the surface of the electrostatic chuck for cleaning.If the plasma generated in the plasma generation chamber is generated by the gradient of the divergent magnetic flux density generated by the main magnetic coil, The surface is irradiated onto the surface of the electrostatic chuck holding the substrate to irradiate the surface, and not only moisture on the surface but also dust is removed by sputtering, so that the surface can be completely cleaned in a short time.

In this case, if the plasma irradiation is performed in a state where an RF bias is applied to the electrostatic chuck, the plasma is uniformly distributed due to an electric field distribution formed by a negative bias potential appearing on the surface of the electrostatic chuck. And reaches the surface of the electrostatic chuck, the ions in the plasma are accelerated, and the sputtering action is strengthened, and the surface is cleaned more uniformly and in a shorter time.

Further, if the surface of the electrostatic chuck is irradiated with plasma while simultaneously introducing the gas to be converted into plasma in the plasma generation chamber into the plasma generation chamber and the reaction chamber, the magnetic field lines of the divergent magnetic field formed by the main magnetic coil can be obtained. The plasma which is about to spread along the gas is blown from gas supply means which is arranged in the reaction chamber and blows out the reaction gas radially inward in a circumferentially uniform amount, so that the direction is directed toward the electrostatic chuck surface. Corrected, the plasma density around the electrostatic chuck surface is increased, the plasma reaches the electrostatic chuck surface uniformly and in large amount, and the surface cleaning is performed in a shorter time.

The cleaning of the surface of the electrostatic chuck by each of the above methods is performed by maintaining the gas pressure in the plasma generation chamber and the reaction chamber at a high vacuum of 1 × 10 ^{−4 to} 5 × 10 ⁻³ Torr, If an axial mirror magnetic field is formed in the chamber, the plasma generated in the plasma generation chamber becomes highly active and dense, and the plasma flowing out of the plasma extraction window does not spread in the reaction chamber without spreading. The cleaning is concentrated on the surface of the electro-chuck, and the cleaning is completed in a shorter time.

[0016]

FIG. 1 shows an ECR for applying the method of the present invention.
1 shows an embodiment of a plasma CVD apparatus configuration. This configuration is different from the configuration of FIG.
13 is connected via a variable capacitor 14. Note that among the constituent members of the apparatus, the same members as those in FIG. 3 are denoted by the same reference numerals.

The cleaning of the electrostatic chuck surface is performed as follows. First, after the inside of the apparatus is evacuated, the current flowing through the main magnetic coil 4 is adjusted to form a magnetic flux density region satisfying the ECR condition in the vicinity of the microwave introduction window 2 in the plasma generation chamber 5 and the auxiliary magnetic field. The coil is also energized to form a mirror magnetic field in the reaction chamber 6 to introduce microwaves.
Thereafter, two atoms that do not generate a reaction product between the first gas introduction system 3 and an inert gas such as Ar or He or an electrostatic chuck surface layer such as H ₂ , O ₂ or N _{2 which is} usually made of ceramics. When the gas pressure in the apparatus is 1 × 10 ^{-4 to} 5
Introduce at a flow rate that keeps it at × 10 ⁻³ Torr. Therefore,
Since the gas introduced into the plasma generation chamber 5 is efficiently converted into plasma in a high vacuum state and in a magnetic flux density region satisfying the ECR condition, the gas is generated with high activity and high density.
Due to the gradient of the divergent magnetic flux density created by the main magnetic coil 4, the magnetic flux flows out of the plasma extraction window 7 into the reaction chamber 6 . On the other hand, in the reaction chamber 6 , a mirror magnetic field is formed by the main magnetic coil 4 and the auxiliary magnetic coil 12, and once divergent plasma is generated by the mirror magnetic field that refocuses toward the inside of the auxiliary magnetic coil 12. The magnetic flux reaches the electrostatic chuck surface.

On the other hand, the electrostatic chuck 10 has a frequency of 400 k
Since a high-frequency power source 13 such as Hz or 13.56 MHz is connected via a capacitor 14, a negative bias potential appears on the surface of the electrostatic chuck. The distribution of the plasma reaching the surface in the radial direction is made uniform, and the ions in the plasma are accelerated by the negative bias potential, so that the electrostatic chuck surface is sputtered uniformly and effectively. As a result, moisture and dust adsorbed on the surface of the electrostatic chuck are effectively and quickly removed, and the surface of the electrostatic chuck is scraped with a small amount to recover the attraction force.

FIG. 2 shows a case where an SiO ₂ film is formed on a substrate surface using an electrostatic chuck whose surface has been cleaned by the conventional method and an electrostatic chuck whose surface has been cleaned by the method of the present invention. This shows the difference in how the film forming speed varies for each film forming.

When a substrate is sucked and held by an electrostatic chuck whose surface has been cleaned by a conventional method, the film forming speed of each film greatly varies, whereas the method of the present invention cleans the surface. When the electrostatic chuck is sucked and held, there is almost no variation between film formations. This is because, when the surface is cleaned by a conventional method, the substrate is not adsorbed in a close contact state over the entire surface, and the close contact state fluctuates for each film formation, and a non-contact area where heat transfer to the wafer stage is poor is formed. On the other hand, in the case where the surface is cleaned by the method of the present invention, the substrate is adsorbed in a state of being in close contact with the entire surface, and thus the adsorption state is not changed for each film formation.

[0021] Incidentally, the gas introduced into the plasma generating chamber 5 and also plasma irradiation the electrostatic chuck surface while introducing at the same time as the plasma generation chamber 5 into the reaction chamber 6 through the second gas introducing system 8, an annular gas nozzle The gas blown radially inward in the circumferential direction by a uniform amount from 8a suppresses the spread of the plasma flowing out from the plasma extraction window 7, and the plasma reaches the electrostatic chuck surface more uniformly and in a large amount. Cleaning of the chuck surface can be completed in a shorter time.

[0022]

According to the present invention, the cleaning of the electrostatic chuck surface before the substrate is attracted and held on the electrostatic chuck surface is performed by the above-described method. Can be.

According to the first aspect of the present invention, since the surface of the electrostatic chuck is irradiated with the plasma generated in the plasma generating chamber, moisture and dust on the surface of the electrostatic chuck are completely removed in a short time by the sputtering action. In addition, since the surface of the electrostatic chuck is shaved by a small amount, the chucking force of the electrostatic chuck is completely recovered in a short time, and the operation rate of the apparatus can be increased. Further, since the substrate is always adsorbed and held in a state of being in close contact with the entire surface, the film forming speed for each film forming is always stably kept constant, and the quality of the formed film is made uniform to a high level.

According to the second aspect of the present invention, a negative bias potential appears on the surface of the electrostatic chuck, and the electric field distribution formed by this potential causes the plasma to uniformly distribute and reach the electrostatic chuck. The sputtering action for accelerating the ions therein is strengthened, and the surface is cleaned more uniformly and in a shorter time.

According to the third aspect of the present invention, the spread of the plasma flow flowing out of the plasma extraction window of the plasma generation chamber is suppressed by the gas from the gas supply means which blows the gas radially inward in a uniform amount in the circumferential direction. Radial distribution of plasma density toward the electric chuck is made uniform,
More plasma reaches the electrostatic chuck surface and the surface is cleaned more uniformly and in a shorter time than when no gas is introduced into the reaction chamber.

According to the method of the present invention, the plasma generated in the plasma generation chamber has high activity and high density, and the plasma flowing out of the plasma extraction window concentrates on the surface of the electrostatic chuck without spreading in the reaction chamber. Cleaning is completed in a shorter time.

[Brief description of the drawings]

FIG. 1 shows an ECR plasma C when applying the method of the present invention.
Device cross-sectional view showing one embodiment of a VD device configuration

FIG. 2 shows a variation in film formation yield when an SiO ₂ film is formed on a substrate surface by adsorbing and holding a substrate on an electrostatic chuck whose surface has been cleaned by the method of the present invention and the conventional method, respectively. Diagram showing the differences

FIG. 3 is a cross-sectional view of a configuration example of a conventional ECR plasma CVD apparatus.

[Explanation of symbols]

2 Microwave introduction window 4 Main magnetic coil 5 Plasma generation chamber 6 Reaction chamber 7 Plasma extraction window 9 Substrate (substrate to be processed) 10 Electrostatic chuck 11 Wafer stage 12 Auxiliary magnetic coil 13 High frequency power supply

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-14223 (JP, A) JP-A-2-42724 (JP, A) JP-A-2-142126 (JP, A) JP-A-1- 98218 (JP, A) JP-A-62-92444 (JP, A) JP-A-2-211626 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/68 H01L 21 / 205 H01L 21/302

Claims (4)

(57) [Claims] 1. A plasma generation chamber having a microwave introduction window and a plasma extraction window on both end surfaces, respectively, and a magnetic field region for generating electron cyclotron resonance with microwaves is formed therein. A reaction chamber in which a gas supply means communicating with the generation chamber and blowing out a reaction gas into the inside thereof; and a reaction chamber in which a wafer stage for holding the substrate to be processed is arranged, and wherein the substrate holding mechanism of the wafer stage has an electrostatic chuck. A wafer stage pretreatment method for cleaning a flat surface of the electrostatic chuck of an ECR plasma CVD apparatus in which is used prior to adsorption and holding of a substrate to be treated on the surface, wherein the plasma processing step comprises: Dirt on the inner walls and internal structures of the generated equipment is cleaned by opening the inside of the equipment to the atmosphere, and dirt on the surface of the electrostatic chuck is removed from the surface. Adsorption of the substrate, prior to the holding, in a vacuum, no Ar, inert gas such as He or H _2, O _2, N _2, etc., the reaction product of the electrostatic chuck surface material into the plasma generation chamber A wafer stage pretreatment method, wherein plasma is generated by introducing a single gas of diatomic molecules, and the plasma is irradiated to the surface of the electrostatic chuck for cleaning. 2. The wafer stage pretreatment method according to claim 1, wherein plasma irradiation on the surface of the electrostatic chuck is performed while applying a high-frequency bias to the electrostatic chuck. 3. A method according to claim 1, wherein the surface of the electrostatic chuck is irradiated with plasma while simultaneously introducing a gas to be plasmatized in the plasma generation chamber into the plasma generation chamber and the reaction chamber. Wafer stage pretreatment method. 4. The method according to claim 1, wherein the gas pressure in the plasma generating chamber and the reaction chamber is set to a high vacuum in a range of 1 × 10 ^{−4 to} 5 × 10 ⁻³ Torr. A wafer stage pretreatment method, comprising: forming a mirror magnetic field in an axial direction in a reaction chamber while irradiating the surface of an electrostatic chuck with plasma;