JP4145457B2 - Electrode plate for plasma etching equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode plate for a plasma etching apparatus, and more particularly to an electrode plate for a plasma etching apparatus that is suitably used for manufacturing a semiconductor device.
[0002]
[Prior art]
As one of semiconductor device manufacturing apparatuses, a plasma etching apparatus that etches a semiconductor wafer using active gas plasma under reduced pressure is known. FIG. 4 is a schematic view showing an example of such a plasma etching apparatus. The apparatus 20 includes a lower electrode plate 23 on which a silicon wafer 27 as a processing object is placed in a reaction chamber 29, and an electrode plate for a plasma etching apparatus that is an upper electrode at a position facing the lower electrode 23. 21 is provided, and a number of gas rectifying holes 22 are formed in the upper electrode plate 21.
[0003]
At the time of etching, a high frequency voltage is applied to the plasma device electrode plate 21 and the lower electrode plate 23 from a high frequency power source 26, and an etching gas is supplied from the gas supply system 24 to the internal gas container 28. The etching gas is rectified by the gas rectifying hole 22 of the upper electrode plate 21 and is jetted toward the silicon wafer 27 to generate plasma between the upper electrode plate 21 and the silicon wafer 27 to perform a desired dry etching process. It has come to be. In addition, surplus gas in the reaction chamber is discharged by a gas discharge system 25.
[0004]
By the way, with the recent high integration and miniaturization of semiconductor devices, the performance required for electrode plates has become more severe, and in order to reduce the generation of particles and contamination, for example, conventional carbon and aluminum electrodes are used. Instead, an electrode plate made of silicon, which is the same material as the wafer, has been developed.
[0005]
Since the plasma etching apparatus 20 performs the etching process by generating plasma between the wafer 27 and the upper electrode plate 21 as described above, not only the wafer but also the upper electrode plate 21 is gradually etched in principle. End up. Therefore, if the electrode plate is made of silicon as described above, contamination does not occur even if the electrode plate is etched, so that the electrode plate itself does not adversely affect the device, and productivity and yield are improved. Plays a big role.
[0006]
However, even when the electrode plate is made of silicon, the reaction product adheres to the inner wall of the rectifying hole or the gas introduction side surface due to the plasma flowing into the gas rectifying hole, and the reaction product is charged up. Due to the problem of abnormal discharge, frequent cleaning was necessary.
[0007]
In Japanese Patent Laid-Open No. 10-270418, the opening diameter of the gas rectifying hole of the gas head (upper electrode plate) has a maximum diameter at one opening end so that this cleaning can be efficiently performed, The method of making it the shape reduced by this is disclosed. By adopting such a shape of the rectifying hole, when the reaction product adhering to the inside of the rectifying hole is wet-cleaned, if the cleaning liquid is injected into the rectifying hole from the opening end having the maximum diameter, it flows to the smaller opening diameter. As the pressure increases and the flow rate is increased, the reaction product can be removed efficiently.
[0008]
[Problems to be solved by the invention]
However, when performing actual cleaning, it is necessary to detach the electrode plate from the apparatus in wet cleaning. Therefore, the loss associated with opening the reaction chamber or making fine adjustments to the apparatus is better than removing the reaction products. Is big. Therefore, it is important to reduce not only the efficiency but also the number of cleanings as much as possible.
[0009]
In JP-A-10-270418, when dry cleaning is performed with plasma while the upper electrode is mounted on the apparatus, if the opening end having the maximum diameter is mounted toward the reaction chamber, the incident angle of the radical is increased. Thus, the cleaning efficiency is improved. However, if the opening end having the maximum diameter is attached to the reaction chamber side, it becomes easier for plasma to enter the rectifying hole even in the actual process, and the adhesion of reaction products increases, so the frequency of cleaning is also high. There was a problem that productivity could not be improved. Furthermore, if the opening end having the maximum diameter is increased excessively, there is a problem that the mechanical strength of the electrode plate cannot be maintained.
[0010]
In addition, in a conventional general plasma etching apparatus electrode plate in which rectifying holes of the same diameter are formed, as the electrode plate itself is consumed, the diameter increases on the gas ejection side to become a tapered shape, and plasma gradually enters. There was a problem that the amount of the reaction product deposited was increased. Therefore, the electrode plate having the rectifying holes having the same diameter also has a problem that the life is shortened as a result.
[0011]
The present invention has been made in view of the above problems, and during the etching process, the invasion of plasma into the gas rectifying hole is suppressed, the reaction product hardly adheres in the hole, and the number of cleanings is reduced. An object of the present invention is to provide an electrode plate for a plasma etching apparatus that can be used for a long period of time and has sufficient mechanical strength.
[0012]
[Means for Solving the Problems]
As a result of studying to solve the above problem, the present inventors are an electrode plate provided with a plurality of gas rectifying holes used as an upper electrode of a plasma etching apparatus, wherein the diameter of the gas rectifying holes is a gas It is characterized in that d2 <d1 <L / 2 where d1 is a hole diameter on the introduction side, d2 is a hole diameter on the gas ejection side, and L is a distance between centers of adjacent gas rectifying holes. An electrode plate for plasma etching equipment was developed .
[0013]
Since the diameter (d2) on the gas ejection side of the gas rectifying hole is smaller than the diameter (d1) on the gas introduction side (d2 <d1), the pressure is higher on the gas ejection side than on the gas introduction side. Intrusion of plasma can be suppressed, and the amount of reaction product attached to the inner wall of the gas rectifying hole is also reduced.
[0014]
Further, in the electrode plate for a plasma etching apparatus of the present invention, the gas rectifying holes are formed such that the distance (pitch) L between the centers of the adjacent gas rectifying holes satisfies d1 <L / 2. A sufficient gap is provided between the holes and the mechanical strength is maintained. Therefore, even if the surface of the electrode plate is consumed by etching, adjacent rectifying holes do not come into contact with each other or are not connected by a part of them, and the gas ejection amount in each rectifying hole is kept constant and long. Can be used for a period.
[0015]
The diameter of the gas rectifying hole on the ejection side is preferably 0.1 to 1.5 mm .
When the rectifying hole smaller than 0.1 mm is formed, it is difficult to form and costs, and the reaction product is likely to adhere to the hole and close the hole, but is difficult to clean. Moreover, when the rectifying hole exceeding 1.5 mm is formed, the original gas rectifying action may be weakened.
[0016]
The electrode plate is preferably made of silicon , and the specific resistance is preferably 0.001 to 50 Ω · cm .
By using the electrode plate made of silicon in this way, when the object to be processed is a silicon wafer, contamination does not occur. Moreover, since the thing with a specific resistance in the said range is also used as a wafer, it is easy to acquire and there also exists an advantage that cost can be restrained low.
[0017]
Furthermore, the thickness of the electrode plate according to the present invention is preferably 2 to 20 mm .
If the thickness of the electrode plate is less than 2 mm, the strength of the electrode plate is weak. Conversely, if the thickness exceeds 20 mm, the formation of rectifying holes may be difficult, and the material cost will increase, so it is within the above range. Is preferred.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, but the present invention is not limited thereto.
[0019]
A plurality of gas rectifying holes are formed in the electrode plate according to the present invention at predetermined intervals. The present invention is characterized by the shape of the rectifying holes and the interval between the rectifying holes. That is, in the electrode plate for a plasma etching apparatus of the present invention, the gas rectifying hole has a hole diameter of d1, a gas introduction side hole diameter of d1, a gas ejection side hole diameter of d2, and a center distance between adjacent gas rectification holes of L2. Then, d2 <d1 <L / 2 is formed.
[0020]
FIG. 1 schematically shows a partial cross section of an example of an electrode plate for a plasma etching apparatus according to the present invention. In the illustrated electrode plate 1, a tapered gas rectifying hole 2 having a maximum diameter (d1) on the gas introduction side and a minimum diameter (d2) on the gas ejection side is formed. The gas supplied from the internal gas supply system is jetted into the reaction chamber from a number of gas rectifying holes 2 provided in the electrode plate 1.
[0021]
In each gas rectifying hole 2, gas flows from the introduction side of the maximum diameter (d1) to the injection side of the minimum diameter (d2), so that it is ejected at a pressure higher than the pressure at which the gas enters on the introduction side. become. Therefore, since the plasma generated in the reaction chamber can be prevented from entering from the ejection side of the gas rectifying hole 2, the reaction product can be prevented from adhering in the hole, and the original rectifying action can be maintained for a long time. Accordingly, the number of cleanings of the electrode plate 1 can be reduced. In addition, if the gas ejection side diameter is reduced in this way, the ejection side diameter does not easily increase even when used for a long period of time, so that there is an advantage that the life of the electrode plate 1 is extended.
[0022]
In the electrode plate for a plasma etching apparatus according to the present invention, a plurality of gas rectifying holes are formed with sufficient intervals so as to satisfy the relationship (d1 <L / 2). More specifically, in the electrode plate 1 shown in FIG. 1, the distance L between the centers of the adjacent rectifying holes 2a and 2b is represented by L = S + d1. Therefore, the relationship of d1 <L / 2 is equal to the relationship of d1 <S, that is, the rectifying holes 2a and 2b are formed with a gap S larger than the introduction-side diameter d1. If the rectifying holes are formed with sufficient intervals as described above, the mechanical strength is sufficiently maintained even if a large number of rectifying holes are provided. In addition, even if the electrode plate itself is somewhat etched after using for a long time, the rectifying holes do not touch each other or are not connected by a part of them, and the rectifying action is stable over a long period of time in each rectifying hole, The gas ejection amount is also kept uniform.
[0023]
FIG. 2 schematically shows a partial cross section of another example of the electrode plate for a plasma etching apparatus according to the present invention.
In the electrode plate 11 of FIG. 2, a plurality of gas rectifying holes 12 are formed so as to satisfy the relationship d2 <d1 <L / 2, as in the electrode plate 1 shown in FIG. Two-stage cylindrical rectifying holes 12 having different diameters are formed on the ejection side and the ejection side. Even in such an embodiment, since the gas is ejected at a high pressure from the introduction side to the ejection side, the plasma in the reaction chamber is suppressed from entering the gas rectifying hole 12. Therefore, it is possible to prevent the reaction product from adhering in the holes, the number of cleanings is reduced, and the life of the electrode plate is also long.
[0024]
In addition, as with the embodiment shown in FIG. 1, the interval between adjacent gas rectifying holes is formed with a sufficient interval so as to satisfy the relationship d2 <d1 <L / 2. Therefore, the mechanical strength is sufficiently maintained, the rectifying action is stable even when used for a long time, and the gas ejection amount is also kept uniform.
Note that the shape of the gas rectifying holes and the interval between the adjacent rectifying holes are not limited to those shown in FIGS. 1 and 2, and may be, for example, a combination of a tapered shape and a cylindrical shape.
[0025]
Regarding the specific size of the gas rectifying hole of the electrode plate according to the present invention as exemplified in FIGS. 1 and 2, the hole diameter on the ejection side is preferably 0.1 to 1.5 mm. As described above, if the rectifying hole smaller than 0.1 mm is formed, it is expensive and difficult to form, and the reaction product adheres to the hole and the hole is easily blocked. On the other hand, if the rectifying hole exceeding 1.5 mm is formed, the original gas rectifying action may be diminished.
[0026]
The material of the electrode plate is not particularly limited, but if the electrode plate is made of the same material as the material to be processed, even if particles generated by etching the electrode plate adhere to the material to be processed, the material is the same as the material to be processed. Therefore, contamination can be effectively prevented. Therefore, for example, when etching a silicon wafer, it is preferable to use a silicon electrode plate.
[0027]
Moreover, when it is set as a silicon electrode plate in this way, it is preferable that the specific resistance is 0.001-50 ohm * cm, and it is especially preferable that it is 0.001-10 ohm * cm. Since silicon wafers to be processed often have a specific resistance within the above range, the electrode plate and the wafer to be processed are very close in terms of electrical properties as well as the material, and the electrode plate itself Contamination is more effectively suppressed even when etched.
The wafer to be processed is usually obtained by slicing a silicon ingot. By cutting such an ingot into a thickness for the electrode plate, an electrode plate having the same properties as the wafer can be easily obtained at low cost. be able to.
[0028]
The thickness of the electrode plate is preferably 2 to 20 mm. If the plate thickness is less than 2 mm, the mechanical strength becomes insufficient, and there is a possibility that it cannot be used for a long time. Further, if the plate thickness exceeds 20 mm, the formation of the rectifying hole becomes difficult and the cost of forming the rectifying hole becomes high, and there is no advantage of improving the rectifying action even if it is thicker than this, so it is simply a material. Expense is wasted.
[0029]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Examples and Comparative Examples)
The semiconductor ingot was cut to obtain a 6 mm thick silicon disk. After peripheral grinding, a gas rectifying hole with a taper as shown in FIG. 1 was formed by a diamond drill, and surface polishing was further performed to produce an electrode plate having a diameter of 280 mm and a plate thickness of 5 mm. The gas rectifying holes formed by the diamond drill had a pitch of 7 mm, an opening diameter on the gas introduction side of 1 mm, and an opening diameter on the ejection side of 0.5 mm (Example 1).
[0030]
In the same manner, a total of three types of electrode plates were prepared with only the opening diameter on the gas introduction side being 1.5 mm (Example 2) and 0.8 mm (Example 3), respectively.
On the other hand, as a comparative example, a conventional electrode plate having straight straightening holes (diameter 0.5 mm, pitch 7 mm) having the same opening diameter on the gas introduction side and ejection side was used.
[0031]
These electrode plates were attached to a plasma etching apparatus to etch a silicon wafer, and the number of particles generated by reaction products adhering to and peeling from the rectifying holes and the apparatus operating time were compared. The results are shown in FIG. 3 (note that the particle specification is limited to 16).
[0032]
As is apparent from the results of FIG. 3, when an electrode plate (comparative example) having the same opening diameter on the gas introduction side and the ejection side is used, the number of particles increases and falls outside the specifications. Whereas after 35 hours, when the electrode plates of Examples 1 to 3 were used, the lengths were longer after 60, 50, and 70 hours, respectively. From this result, it can be seen that in the electrode plates of Examples 1 to 3, the operation time until the electrode plate needs to be cleaned can be long.
[0033]
The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0034]
As described above, the electrode plate for a plasma etching apparatus according to the present invention suppresses the adhesion of reaction products due to the features of the shape and the distance between the electrode plates, thereby preventing contamination. Therefore, for example, even when a silicon wafer is etched, the material of the electrode plate is not particularly limited, and conventionally used carbon, aluminum, silicon carbide, and the like can also be used.
[0035]
【The invention's effect】
As described above, the electrode plate according to the present invention is characterized by the shape of the rectifying holes and the distance between the rectifying holes, and the gas rectifying holes have a hole diameter (d1) on the gas introduction side and a gas blowing side. The relationship between the hole diameter (d2) and the center distance (L) between adjacent gas rectifying holes is formed so that d2 <d1 <L / 2. By forming the gas rectifying hole in this way, it is possible to suppress the plasma from entering the gas rectifying hole, effectively preventing the reaction product from adhering to the hole, and the mechanical strength of the electrode plate, etc. It is kept for a long time.
[0036]
Therefore, if the electrode plate according to the present invention is used in a plasma etching apparatus, the number of cleanings of the electrode plate is greatly reduced, and the electrode plate itself can be used for a long time even if it is gradually etched and consumed. Furthermore, since the diameter is large on the gas introduction side of the electrode plate, it is difficult to increase the diameter on the gas ejection side, the rectification action is stable over a long period of time, the gas ejection amount is kept uniform, and thus productivity is improved. You can also.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional schematic view of an example of an electrode plate for a plasma etching apparatus according to the present invention.
FIG. 2 is a partial cross-sectional schematic view of another example of an electrode plate for a plasma etching apparatus according to the present invention.
FIG. 3 is a graph showing the relationship between the apparatus operating time and the number of generated particles.
FIG. 4 is a schematic view showing an example of a plasma etching apparatus.
[Explanation of symbols]
1,11,21 ... Plasma device electrode plate (upper electrode plate),
2, 2a, 2b, 12, 22 ... gas rectifying holes, 20 ... plasma etching apparatus,
23 ... Lower electrode plate, 24 ... Gas supply system, 25 ... Gas discharge system,
26 ... high frequency voltage source, 27 ... silicon wafer, 28 ... internal gas container,
29 ... Reaction room.

Claims (4)

An electrode plate made of a single silicon plate provided with a plurality of gas rectifying holes used as an upper electrode of a plasma etching apparatus, wherein the diameter of the gas rectifying holes is d1 as a gas introducing side diameter. An electrode plate for a plasma etching apparatus, wherein d2 <d1 <L / 2, where d2 is a hole diameter on the side and L is a distance between centers of adjacent gas rectifying holes.   2. The electrode plate for a plasma etching apparatus according to claim 1, wherein a hole diameter on the ejection side of the gas rectifying hole is 0.1 to 1.5 mm. The electrode plate for a plasma etching apparatus according to claim 1 or 2 , wherein a specific resistance of the electrode plate is 0.001 to 50 Ω · cm. The thickness of the said electrode plate is 2-20 mm, The electrode plate for plasma etching apparatuses of any one of Claim 1 thru | or 3 characterized by the above-mentioned.

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