JP3908333B2 - Electrostatic chuck and semiconductor processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic chuck, a semiconductor processing apparatus, and an insulating material suitable for them, and in particular, has an insulating layer on an electrode, and a voltage such as a semiconductor wafer is applied on the insulating layer by applying a voltage to the electrode. The present invention relates to an electrostatic chuck for electrostatically attracting a sample, a semiconductor processing apparatus incorporating the electrostatic chuck, and an insulating material suitable for them.
[0002]
[Prior art]
An electrostatic chuck that has an insulating layer on an electrode as a jig for fixing a sample such as a semiconductor wafer in a reduced-pressure atmosphere and electrostatically adsorbs the sample on the insulating layer by applying a voltage to the electrode It is known that the insulating layer is formed of a resin such as polyimide or a ferroelectric ceramic such as CaTiO ₃ .
[0003]
However, an electrostatic chuck having an insulating layer formed of a resin such as polyimide has problems in terms of durability and heat resistance, and an electrostatic chuck having an insulating layer formed of a ferroelectric ceramic such as CaTiO ₃ is insulated. Since the thermal conductivity of the layer is low, there is a problem that the temperature of the sample becomes non-uniform in a semiconductor manufacturing process such as an etching process.
[0004]
In view of this, an electrostatic chuck in which an insulating layer is formed of aluminum nitride, which has good durability, heat resistance, etc., and excellent thermal conductivity, has attracted attention.
[0005]
[Problems to be solved by the invention]
However, since aluminum nitride has a weak bond between particles, the aluminum nitride particles easily fall off from the surface of the insulating layer. Therefore, when a sample such as a semiconductor wafer is brought into contact with the electrostatic chuck, not only the back surface of the semiconductor wafer is easily contaminated by particles, but also the generated particles contaminate the chamber.
[0006]
The present invention has been made in view of the above circumstances, and an electrostatic chuck having an adsorption surface with low contamination of the adsorbed sample and excellent in thermal conductivity, a semiconductor processing apparatus incorporating the electrostatic chuck, and those One object is to provide an insulating material suitable for the above.
[0007]
[Means for Solving the Problems]
As a result of diligent research to achieve the above-mentioned object, the inventors of the present invention obtained a nitridation by dispersing 3.2 to 20% of titanium nitride or zirconium carbide particles in aluminum nitride substantially uniformly. The present invention was completed with the knowledge that the bonding between the aluminum particles was strengthened, thereby obtaining an insulating layer with less aluminum nitride particle dropout and excellent thermal conductivity.
[0008]
That is, the electrostatic chuck according to the present invention is an electrostatic chuck that has an insulating layer on an electrode and electrostatically adsorbs a sample on the insulating layer by applying a voltage to the electrode. Is characterized in that particles of titanium nitride or zirconium carbide of 3.2 to 20% by volume in aluminum nitride are dispersed substantially uniformly.
[0009]
In the above electrostatic chuck, the average particle diameter of the titanium nitride or zirconium carbide particles is preferably 3.0 μm or less.
[0016]
A semiconductor processing apparatus according to the present invention incorporates the electrostatic chuck described above.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic structure of an electrostatic chuck according to a preferred embodiment of the present invention.
[0019]
The insulating layer 1 is made of aluminum nitride as a main component, and conductive particles for strengthening the bond between the aluminum nitride particles are dispersed substantially uniformly in the aluminum nitride. As a result, the bonding between the aluminum nitride particles becomes strong, so that when the sample 10 such as a semiconductor wafer is adsorbed, the aluminum nitride particles are prevented from falling off due to friction or the like, and the contamination of the sample 10 or the like is reduced. can do.
[0020]
The constituent material (additive material) of particles dispersed in aluminum nitride (hereinafter referred to as additive particles) is preferably a nitride or carbide of a group 4a element, and among these, titanium nitride is more preferable. This is because titanium nitride hardly reacts with aluminum nitride, and thus the decrease in thermal conductivity of the insulating layer due to the addition of titanium nitride is small. Note that the additive substance is not limited to the nitride or carbide of the group 4a element, and may be another substance as long as it can strengthen the bond between the aluminum nitride particles.
[0021]
The addition amount of the additive substance is preferably 3.2 to 20% (5.1 to 29.1% by weight) in volume ratio. If the content is less than 3.2%, the bonding between the aluminum nitride particles is not sufficiently strengthened, so that the generation of particles cannot be effectively prevented. This is because, since the insulating property is lowered and an excessive leakage current flows to the semiconductor wafer (sample), the element formed on the wafer may be damaged.
[0022]
FIG. 2 shows the relationship between the amount of titanium nitride added and the quality of the insulating layer 1, and FIG. 3 is a graph of the numerical values shown in FIG. 2 and 3, the “number of particles” is the number of particles adhering to the back surface of the silicon wafer when an 8 inch diameter silicon wafer is adsorbed on the insulating layer 1 of the electrostatic chuck shown in FIG. It is the result counted by the particle counter. That is, the number of particles indirectly indicates the number of particles generated from the insulating layer 1. The “volume resistivity” is a result of measuring the volume resistivity of the insulating layer 1 at room temperature. In FIG. 3, the ▲ mark indicates the number of particles, and the ● mark indicates the volume resistivity.
[0023]
As shown in FIG. 2 and FIG. 3, it is understood that when the addition amount (volume ratio) of titanium nitride is less than 3.2%, the number of generated particles rapidly increases and deteriorates the quality of the electrostatic chuck. Is done. On the other hand, the volume resistivity of the insulating layer 1 decreases from the vicinity where titanium nitride (volume ratio) exceeds 19.0%, and when it exceeds 20%, the volume resistivity is finely adjusted by the amount of titanium nitride added. Becomes difficult. By the way, it is known that the desorption characteristic of the sample in the electrostatic chuck depends on the volume resistivity, and when the volume resistivity is reduced to about 10 ⁸ Ω · cm, the practicality as the electrostatic chuck is lost. From this experimental result, it is understood that the addition amount of titanium nitride is preferably 3.2 to 20% by volume.
[0024]
The size of the additive particles is not particularly limited, but the average diameter is preferably 3.0 μm or less. If the average diameter exceeds 3.0 μm, it will be difficult to uniformly disperse the additive particles, and the insulating properties will deteriorate due to contact between the additive particles.
[0025]
An electrode 2 is provided on the lower surface of the insulating layer 1, and the sample 10 can be electrostatically adsorbed to the adsorption surface of the insulating layer 1 by applying a voltage to the electrode 2.
[0026]
The structure of the electrostatic chuck may be, for example, a structure in which the insulating layer 1 is formed on a ceramic plate on which the electrode 2 is formed, for example, a structure in which the electrode 2 is directly formed on the insulating layer 1, or other It may be the structure.
[0027]
As a constituent material of the electrode 2, for example, tungsten, molybdenum, silver, nickel, or other metal materials can be adopted. In addition, the electrode 2 may be any of a monopolar type, a bipolar type, and a comb type.
[0028]
This electrostatic chuck is suitable for an etching apparatus, a CVD apparatus, and other semiconductor processing apparatuses, as well as a transfer apparatus, and the shape can be selected according to the application.
[0029]
As described above, conductive particles (particularly nitrides or carbides of group 4a elements) having a volume ratio of 3.2 to 20% in order to strengthen the bond between aluminum nitride particles, mainly composed of aluminum nitride. ) Is dispersed substantially uniformly in the aluminum nitride to form an insulating layer, whereby an electrostatic chuck having an insulating layer with less aluminum nitride particle dropout and excellent thermal conductivity can be obtained.
[0030]
By the way, the insulating layer described above is suitable not only for electrostatic chucks but also for components of semiconductor processing devices such as heaters and susceptors, because aluminum nitride particles are less dropped and excellent in thermal conductivity. .
[0031]
In addition, the semiconductor processing apparatus provided with the electrostatic chuck and the semiconductor processing apparatus partially adopting the insulating layer have the effect that the sample is less contaminated and the temperature of the sample can be easily controlled.
[0032]
Below, the suitable Example of the electrostatic chuck which concerns on this invention, and its comparative example are shown.
[0033]
[Example 1]
First, 90% by volume of aluminum nitride powder containing yttria and 10% by volume of titanium nitride powder are mixed, alumina beads having a diameter of about 2 mm are used as a grinding medium, and these raw materials are crushed by a ball mill for 100 hours. The titanium nitride powder was dispersed substantially uniformly in the aluminum nitride powder. At this time, the average particle diameter of the titanium nitride powder was about 0.5 μm.
[0034]
Next, in a nitrogen gas atmosphere, hot press sintering was performed for 1 hour under conditions of a temperature of 1800 ° C. and a pressure of 20 MPa, and a disc-shaped insulation having a diameter of 200 mm (8 inches) and a thickness of 1 mm as shown in FIG. Layer 1 was created. The volume resistivity of the insulating layer 1 was 4.2 × 10 ¹⁴ Ω · cm, and the thermal conductivity was 140 W / K · m.
[0035]
Next, as shown in FIG. 4B, a bipolar electrostatic chuck electrode 2 is formed on one surface of the insulating layer 1 by nickel plating, and the other surface (sample adsorption surface) is polished. The surface roughness Ra was 1.2 μm.
[0036]
Next, as shown in the sectional view of FIG. 4C, the surface of the aluminum pedestal 3 is anodized (oxidized) to form an alumina film 3a. As shown in the sectional view of FIG. The insulating layer 1 was stuck on the alumina film 3a with the adhesive 4 to complete the electrostatic chuck.
[0037]
[Examples 2-6, Comparative Examples 1-4]
The electrostatic chuck was prepared under the same conditions as in Example 1 except that the kind of additive substance, the average particle diameter, and the addition amount were changed and the other conditions were changed. FIG. 5 is a diagram illustrating manufacturing conditions for the electrostatic chucks of Examples 1 to 6 and Comparative Examples 1 to 4.
[0038]
[Evaluation of electrostatic chuck]
Each created electrostatic chuck is incorporated in a plasma etching apparatus, +300 V is applied to one electrode of the electrostatic chuck, −300 V is applied to the other electrode, and the silicon wafer is adsorbed to form a circuit element formed on the silicon wafer. Was investigated whether or not. The number of particles on the back surface of the silicon wafer adsorbed on the electrostatic chuck was counted using a particle counter.
[0039]
FIG. 6 is a diagram illustrating experimental results regarding Examples 1 to 6 and Comparative Examples 1 to 4. As shown in the figure, in Examples 1 to 6 and Comparative Examples 1 and 3, no damage was found in the circuit formed on the silicon wafer, but in Comparative Examples 2 and 4, there was a broken circuit. there were. Electrostatic chucks with damaged circuits are those with a large amount of additive (Comparative Example 2) and those with a large average particle size (Comparative Example 4). The cause of the damage is the conductive particles in the insulating layer. It is considered that the insulation (volume resistivity) is reduced due to a short circuit between them, that is, a leak current is generated.
[0040]
In Examples 1 to 6, the number of particles on the back surface of the silicon wafer was 50/8 inch wafer or less. On the other hand, in Comparative Examples 1 and 3, the number of particles on the back surface of the silicon wafer was 500/8 inch wafer or more.
[0041]
【The invention's effect】
According to the present invention, it is possible to obtain an electrostatic chuck having an adsorption surface with less contamination of the adsorbed sample and excellent thermal conductivity.
[0043]
Further, according to the present invention, it is possible to obtain a semiconductor processing apparatus with less sample contamination and easy sample temperature control.
[0044]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic structure of an electrostatic chuck according to a preferred embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between the amount of titanium nitride added and the quality of the insulating layer.
FIG. 3 is a graph showing the relationship between the amount of titanium nitride added and the quality of the insulating layer.
FIG. 4 is a diagram schematically showing a manufacturing process of an electrostatic chuck.
FIG. 5 is a diagram showing manufacturing conditions for the electrostatic chucks of Examples 1 to 6 and Comparative Examples 1 to 4;
6 is a diagram showing experimental results regarding the electrostatic chucks of Examples 1 to 6 and Comparative Examples 1 to 4. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Insulating layer 2 Electrode 3 Aluminum base 3a Alumina film 4 W Thermal conductive adhesive 10 Sample

Claims (3)

In an electrostatic chuck having an insulating layer on an electrode and electrostatically adsorbing a sample on the insulating layer by applying a voltage to the electrode, the insulating layer is 3.2 to 3.2 in volume ratio in aluminum nitride. An electrostatic chuck comprising 20% titanium nitride or zirconium carbide particles dispersed substantially uniformly. The electrostatic chuck according to claim 1, wherein an average particle size of the titanium nitride or zirconium carbide particles is 3.0 μm or less. Semiconductor processing apparatus comprising incorporating an electrostatic chuck according to claim 1 or 2.

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