JP3297571B2 - Electrostatic chuck - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck for processing and transporting a wafer by electrostatically attracting and holding it in a semiconductor manufacturing apparatus or the like, and more particularly to an electrostatic chuck excellent in durability.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing apparatus, in order to form and etch a semiconductor such as a silicon wafer, it is necessary to maintain the flatness of the silicon wafer while maintaining the flatness of the silicon wafer. A vacuum suction type and an electrostatic suction type have been proposed.

[0003] Among these holding means, an electrostatic chuck capable of electrostatically holding a silicon wafer can easily realize a flatness and a flatness of a processing surface required when processing the silicon wafer. In addition, the silicon wafer can be processed in a vacuum.

In recent years, as the degree of integration of integrated circuits of semiconductor devices has increased, the precision of electrostatic chucks has become higher, and ceramic electrostatic chucks having excellent corrosion resistance, wear resistance and thermal shock resistance have been demanded. It has become In particular, an electrostatic chuck whose surface condition is important can improve the surface characteristics by coating a desired material on the surface of the substrate. Therefore, an electrode plate having an insulating layer made of alumina, sapphire, or the like formed thereon (Japanese Patent Application Laid-Open No. Sho 60-2)
No. 61377), a device in which a conductive layer is formed on an insulating substrate and an insulating layer is formed thereon (JP-A-4-34953).
No., and a device in which a conductive layer is incorporated inside an insulating substrate (Japanese Patent Laid-Open No. 62-94953).

[0005]

However, the conventional electrostatic chuck has a problem that its durability in plasma is poor. Therefore, recently, an electrostatic chuck in which aluminum nitride is selected as a ceramic material having excellent plasma resistance and which is coated by a CVD method or the like is disclosed in Japanese Patent Publication No. 5-66919, Japanese Patent Laid-Open No. Sho 62-124735.
JP-A-3-183151, JP-A-3-12364
No. has been proposed.

However, since aluminum nitride is a highly anisotropic material whose coefficient of thermal expansion greatly differs between the a-axis and the c-axis, a difference in the coefficient of thermal expansion occurs between the substrate and the film, and residual stress is generated. . Accordingly, the aluminum nitride film is disclosed in
When the orientation as shown in No. 2364 is present, residual stress is generated at the interface between the film and the substrate, or the strength and toughness of the film itself are reduced, and as a result, warpage of the substrate, cracking of the film, or There has been a problem that peeling is likely to occur.

[0007]

Means for Solving the Problems The present inventors have repeatedly studied the above problems, particularly from the viewpoint of the material constituting the electrostatic chuck, and have found that the aluminum nitride insulating layer formed on the surface of the substrate has an X When the peak intensity of the (002) plane and the peak intensity of the (100) plane in the X-ray diffraction curve satisfy a predetermined relationship, it is found that the stress generated is small and a highly reliable one without cracks or peeling can be obtained. It was.

That is, the electrostatic chuck of the present invention has an insulating layer which is coated on the surface of a substrate by a vapor phase synthesis method and has aluminum nitride as a main component. The peak intensity of the plane is I (00
2) When the peak intensity of the (100) plane is I (100), the peak intensity ratio represented by I (002) / I (100) is 0.3 to 4.0. In particular, the aluminum nitride insulating layer has a non-columnar structure, and the insulating layer has a thickness of 0.01 to 1.0 mm.

[0009]

The aluminum nitride used as the insulating layer in the present invention has crystallographic anisotropy in which the coefficients of thermal expansion differ greatly between the a-axis and the c-axis. Therefore, a difference in thermal expansion coefficient occurs between the substrate and the substrate, and residual stress is likely to occur. In particular,
When the orientation is present in the aluminum nitride insulating layer, residual stress is generated at the interface between the film and the substrate, or the strength and toughness of the film itself are reduced, and as a result, warpage of the substrate, cracking of the film, or peeling is caused. Becomes Moreover, in the oriented film, crystals develop in a columnar shape, and the crystals grow perpendicular to the substrate. However, since the columnar structure has low toughness, cracks are easily propagated, particularly during polishing of a film, and are likely to cause cracks and peeling.

According to the present invention, the orientation of the aluminum nitride insulating layer is caused by the c-axis in the X-ray diffraction curve (00
2) The peak intensities of the (100) plane and the (100) plane caused by the a-axis are represented by I (002) and I (10).
0), the orientation of the film of the insulating layer is controlled by controlling the peak intensity ratio represented by (002) / (100) to be 0.3 to 4.0, and the non-columnar structure By doing so, the toughness of the insulating layer is increased and crack propagation is less likely to occur, so that the strength of the insulating layer is increased and cracking and peeling can be prevented. As described above, according to the present invention, it is not necessary to take a particularly complicated structure, and an insulating layer that is difficult to peel off can be formed, so that the reliability and long-term stability of the electrostatic chuck are guaranteed.

[0011]

FIG. 1 shows a typical structure of an electrostatic chuck according to the present invention. According to FIG. 1, the electrostatic chuck comprises:
It comprises a substrate 1 made of an insulator, electrodes 2 and an insulating layer 3 formed on the surface of the substrate 1. The insulating layer 3
Aluminum nitride is used as a main phase, and is formed on at least the mounting surface of the wafer 4 or the entire base surface exposed in the semiconductor manufacturing apparatus. FIG. 2 shows another structure, in which an electrode 2 is arranged in a base 1, and an insulating layer 3 is formed on the base 1. The insulating layer 3 has aluminum nitride as a main phase and is formed at least on the mounting surface of the wafer 4. In both cases of FIGS. 1 and 2,
A heater may be built in the base 1, or a coolant circulation path may be formed.

In the present invention, the aluminum nitride insulating layer 3 has a peak intensity on the (002) plane of I (002) and a peak intensity on the (100) plane of I (10) on the X-ray diffraction curve.
0), the peak intensity ratio represented by I (002) / I (100) is 0.3 to 4.0, particularly 0.45 to 2.0.
A great feature is that it is zero.

The peak intensity ratio I (002) / I (10
When 0) is smaller than 0.3, the aluminum nitride insulating layer is composed of a columnar film oriented in the a-axis, and when it exceeds 4.0, the aluminum nitride insulating layer is a columnar film oriented in the c-axis. . Therefore, when the peak intensity ratio is in the above range, the aluminum nitride insulating layer has a non-columnar structure, specifically, a granular structure, and the film strength is improved and the peeling resistance is increased. When the peak intensity ratio is 0.45 to 2.0, the non-columnar structure is further strengthened, and a film that is more resistant to peeling can be formed.

The insulating layer mainly composed of aluminum nitride is
It is produced by a gas phase synthesis method. The vapor phase synthesis method includes physical vapor phase synthesis (PVD) such as sputtering and ion plating, plasma CVD, photo CVD, MO
(Metal-organic) means a chemical vapor synthesis method (CVD method) such as CVD.
VD method is desirable.

In the present invention, as a method for controlling the peak intensity of the (002) plane and the (100) plane of the aluminum nitride insulating layer, for example, in the CVD method, the film forming temperature is set to 100 ° C. higher than the normal temperature. Specifically, the temperature is set to 800 to 1000 ° C., and the pressure in the reaction chamber is set to a relatively high value of 15 to 200 torr, or the reaction gas is introduced not intermittently but intermittently. The film may be formed while generating nuclei as needed to suppress crystal growth.

On the other hand, as the substrate 1 on which the insulating layer 3 is formed, any material can be used except that the outermost surface is an insulating layer made of the above-described aluminum nitride. Specifically, Al ₂ O ₃ , AlON, Si ₃ N ₄ , diamond,
Mullite, ZrO _{2 and the} like can be mentioned, and among these, a sintered body mainly composed of aluminum nitride is most preferable because of its excellent plasma resistance during semiconductor production.

Further, a well-known metal material can be applied to the electrode 2 to which a voltage is applied, and for example, an electrode containing at least one of W, Mo, and Mo-Mn can be used. Also,
Conductive ceramic materials such as TiN, SiC, W
C, carbon and Si semiconductor materials (n-type or p-type) can also be used as electrode materials. In addition, the electrode layer 3 is not formed as a substrate, and S
conductive ceramics mainly composed of iC, TiN, WC,
It is also possible to use a single metal such as W or Mo or an alloy thereof, in which case a voltage is directly applied to the conductive substrate itself.

[0018]

EXAMPLE After an electrode layer mainly composed of W was formed in a substrate made of an aluminum nitride sintered body, an insulating layer made of aluminum nitride (AlN) was formed on the surface of the electrode layer by a chemical vapor deposition method. To form the AlN insulating layer, the substrate was placed in a furnace heated to the temperature shown in Table 1 by an external heat method, and nitrogen was added for 8 hours.
(L / min), 1 (l / min) of ammonia, N ₂
O gas was flowed at a rate of 0 to 200 (cc / min), and the pressure in the furnace was set to the pressure shown in Table 1. Then, the reaction was started by flowing aluminum chloride at 0.3 (l / min).
Then, an insulating layer having a thickness of 2 was formed to obtain an electrostatic chuck. For sample No. 10, the film was formed while intermittently introducing aluminum chloride.

An X-ray diffraction measurement was performed on the obtained insulating layer, and the peak intensity on the (002) plane was determined to be I (002), (1).
When the peak intensity of the (00) plane is I (100), I (0)
Table 1 shows the peak intensity ratio represented by 02) / I (100). The structure of the insulating layer was observed by an electron micrograph.

Further, in the obtained electrostatic chuck, the warpage of the substrate after the formation of the aluminum nitride insulating layer was measured,
The occurrence of cracks or peeling of the film was observed. The results are shown in Table 1.

[0021]

[Table 1]

As is clear from the results shown in Table 1, Sample No. 9 having a peak intensity ratio of less than 0.3 was composed of a columnar structure having an a-axis orientation, and the substrate had a large warp of 17 μm. Further, the sample No. having a peak intensity ratio exceeding 4.0.
Samples Nos. 1, 3, and 4 were composed of a columnar structure with c-axis orientation, the substrate was extremely warped, and peeling and cracking were observed in a part of the insulating layer.

On the other hand, all of the samples of the present invention had a non-columnar structure, the warpage of the substrate after film formation was as small as 5 μm or less, and no cracking or peeling of the film was observed at all. In particular, when the peak intensity ratio was 0.45 to 2.0, the warpage could be suppressed to 3 μm or less.

[0024]

As described in detail above, the electrostatic chuck of the present invention improves the peeling resistance of the insulating layer by controlling the orientation of the aluminum nitride insulating layer, and has a high adhesion strength and excellent reliability. And the long-term stability can be obtained, and the manufacturing cost of the electrostatic chuck can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of an electrostatic chuck according to the present invention.

FIG. 2 is a sectional view showing another structure of the electrostatic chuck of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Electrode 3 Insulating layer 4 Silicon wafer

──────────────────────────────────────────────────続 き Continuing from the front page (72) Osamu Himeno Inventor 1-1, Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Inspector, Kagoshima Kokubu Plant Inspector Mikio Fukasawa (56) References JP-A 5-63062 ) Patent flat 6-177231 (JP, a) POWDER DIFFRACTIO N FILE Sets 25 to 26, the United States, JCPDS Interna tional Centre for Diffraction Data , 397,25-1133 (58) investigated the field (Int.Cl. ^7, DB (Name) H01L 21/68

Claims (3)

(57) [Claims] 1. An electrostatic chuck in which an insulating layer containing aluminum nitride as a main component is provided on the surface of a substrate, and the insulating layer is coated by a vapor phase synthesis method, the (002) plane in the X-ray diffraction curve of aluminum nitride. Of the peak intensity of I (00
2) When the peak intensity of the (100) plane is I (100), the peak intensity ratio represented by I (002) / I (100) is 0.3 to 4.0. Electrostatic chuck. 2. The electrostatic chuck according to claim 1, wherein said insulating layer has a non-columnar structure. 3. The electrostatic chuck according to claim 1, wherein said insulating layer has a thickness of 0.01 to 1.0 mm.