JPH1161451A - Focus ring of plasma etching equipment and plasma etching equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the blank discharge time required for reducing the amount of foreign matter that is formed in the initial discharge stage, (initial discharge foreign matter), and to improve the etching productivity by specifying the average surface roughness of each of the principal plane and the other surfaces, all of which are in contact with a plasma, of a focus ring placed in the equipment. SOLUTION: In the focus ring 1 of this equipment, the ten-point average surface roughness of a principal plane 2 in contact with a plasma is adjusted to <=5 μm and also the ten-point average surface roughness of each of a peripheral vertical surface 5 and the other surfaces other than the principal plane 2, all of which are in contact with the plasma, is adjusted to <=30 μm, wherein the adjustment of surface roughness is performed by subjecting such a surface to finish working in surface polishing. When the average surface roughness of the principal plane 2 is >5 μm, a large amount of initial discharge foreign matter is formed during the period from the beginning of the use of this focus ring 1 to the point of time, at which the principal plane 2 is worn by the plasma so as to sufficiently smooth the plane 2. When the average surface roughness of any of the surfaces in contact with the plasma, other than the principal plane 2, is >30 μm, formation of the initial discharge foreign matter is caused. Desirably, the material of the focus ring 1 is glassy carbon that is an amorphous carbon material obtained by baking and carbonizing a cured material of a thermosetting resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a focus ring used for a plasma etching apparatus in a semiconductor device manufacturing process and a plasma etching apparatus using the same.

[0002]

2. Description of the Related Art One of semiconductor device manufacturing processes includes an etching process for forming a circuit pattern on a semiconductor wafer. Among these, in a plasma etching apparatus called a parallel plate type, a semiconductor wafer is arranged on a lower electrode, and is provided in parallel with the upper electrode having a large number of through holes for flowing a reaction gas. A high frequency plasma is generated to etch the wafer.

In this apparatus, a ring-shaped member called a focus ring is arranged outside the lower electrode in order to prevent the diffusion of plasma around the wafer and effectively cause reactive ions to enter the wafer. The focus ring uses glassy carbon in addition to quartz, silicon, and the like. Glassy carbon is a carbon material obtained by carbonizing and sintering a thermosetting resin.
It has a dense structure. This material has not only characteristics such as conductivity, chemical stability, heat resistance, and high purity, which are the characteristics of general carbon materials, but also excellent characteristics such that constituent particles do not fall off. For this reason, it is said that glassy carbon is suitable for semiconductor manufacturing equipment members.

In a plasma etching process of a semiconductor wafer, a fall of a discharge foreign substance onto the wafer causes a decrease in the yield of devices. Therefore, members of the etching apparatus are required to have a small amount of discharge foreign substances. Normally, immediately after a new member in contact with the plasma is newly attached, a large amount of discharge foreign matter is generated. For this reason, it is common to perform an empty discharge immediately after mounting to reduce initial discharge foreign substances, and then to etch a product device. This empty discharge is one of the major factors that reduce the productivity of the device.

[0005]

SUMMARY OF THE INVENTION The first aspect of the present invention is to provide a focus ring for a plasma etching apparatus, which has a short idle discharge time for reducing the initial discharge foreign matter. A second aspect of the present invention is to provide a plasma etching apparatus in which the idle discharge time for reducing the initial discharge foreign matter after the focus ring replacement is short.

[0006]

According to the present invention, the 10-point average surface roughness of the principal plane contacting the plasma is 5 μm or less, and the 10-point average surface roughness of the plasma contact surface other than the principal plane is all 30 μm. The following relates to a focus ring of a plasma etching apparatus. Further, the present invention relates to a plasma etching apparatus having the focus ring.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a focus ring of a plasma etching apparatus is generally a ring-shaped member. FIG. 1 is a partial enlarged cross-sectional view of a focus ring and its surroundings in a state where a focus ring of an example is mounted on a plasma etching apparatus and a silicon wafer is placed thereon.
Another example is shown in FIG. The focus ring 1 shown in FIG. 1 and the focus ring 10 shown in FIG. 2 are arranged on a plane parallel to the semiconductor wafer on the apparatus, and are substantially the plane facing the plasma and having the largest area. FIG.
2 and 11) in FIG.

The surface other than the main plane, which is in contact with the plasma, includes the outer peripheral vertical surface (5 in FIG. 1 and 12 in FIG. 2), as well as the shape of the focus ring and the silicon wafer to be processed. Depends on the state at the time. As in the case of the focus ring 1 shown in FIG. 1, when there is a step on the inner periphery, and when the silicon wafer 8 is large enough to reach between the inner peripheral vertical surface 6 and the upper electrode (that is, the silicon wafer 8 Is larger than the inner diameter of the focus ring 1), the step horizontal surface 3 and the step vertical surface 4 are surfaces that come into contact with the plasma, and the inner peripheral vertical surface 6 is not the surface that comes into contact with the plasma. Also, as in the case of the focus ring 10 shown in FIG. 2, there is no step on the inner periphery, and the silicon wafer 15 is large enough to reach between the inner peripheral vertical surface 13 and the upper electrode (ie, In the case where the outer diameter of the silicon wafer 15 is larger than the inner diameter of the focus ring 10, there is no surface other than the outer peripheral vertical surface 12 that contacts the plasma. However, in FIG. 2, when the outer diameter of the silicon wafer 15 is smaller than the inner diameter of the focus ring, the inner peripheral vertical surface of the focus ring is a surface with which plasma contacts. The back of the focus ring (Fig. 1
7 and 14) in FIG. 2 do not form a surface where the plasma contacts.

The shape of the focus ring may be a ring shape having a circular inner periphery and an outer periphery (for example, the one shown in FIG. 2), a ring shape having a step on the inner periphery (for example, the one shown in FIG. 1), or a silicon wafer. In consideration of the orientation flat (orientation flat) formed on the wafer, the focus ring shape may be adapted to the outer diameter of the wafer with the orientation flat. The size of the focus ring differs depending on the mounted plasma etching apparatus and the size of the silicon wafer to be etched. The size of the silicon wafer is generally 6 inches, 8 inches, 12 inches, or the like. The inner diameter of the focus ring is preferably equal to or smaller than the outer diameter of these silicon wafers, and more preferably 0.1 to 10 mm smaller than the outer diameter of the silicon wafer. The width of the focus ring (ie, the difference between the inner diameter and the outer diameter) is 1
The thickness is preferably 0 to 100 mm, and the thickness is 1
It is preferably about 5 mm.

[0010] In the focus ring of the present invention, the principal plane has an average surface roughness of 10 points (hereinafter referred to as Rz).
Rz of 5 μm or less, and Rz of all other surfaces contacting the plasma is 30 μm. Here, if the surface roughness of the main plane is large and exceeds 5 μm in Rz, a large amount of discharge foreign matter is generated from the start of use until the surface is consumed and smoothed by plasma. The time required for the discharge foreign substances to decrease in the initial stage of use and for the number of foreign substances to stabilize is an empty discharge in which the product device is not processed. In order to make the air discharge time shorter, Rz should be 1 μm
Or less, more preferably 0.5 μm or less. Further, it is preferable that the main plane is completely smooth. If scratches, streaks, and the like remain even if the surface is almost smooth, discharge foreign matter tends to be generated from that portion. In addition, Rz can be measured according to JIS B0601.

[0011] Further, even if Rz of any surface other than the main plane, which is in contact with the plasma, exceeds 30 µm, it may cause discharge foreign matter. In order to make the air discharge time shorter, the Rz of the surface in contact with the plasma other than the main plane is
Is preferably 10 μm or less, more preferably 5 μm or less. The method of forming the surface state as described above is not particularly limited, but it is easy and uniform to perform a mirror polishing process of polishing with a buff cloth or the like using a polishing agent such as a diamond paste. This is preferable because a surface having a surface roughness can be formed.

In the present invention, each surface to be in contact with the plasma generally has substantially uniform surface roughness, and there is little variation in Rz. In order to confirm the uniformity of each surface, it is preferable to measure five points extracted at substantially equal intervals from the entire surface of each surface, and it is preferable that the maximum value be within the above range. The 10 points to be measured for Rz are distributed on a straight line, and the direction of the straight line in FIGS. 1 and 2 is the radial direction (that is, the ring plane) in the main planes 2 and 11 and the step horizontal plane 3. The vertical direction (ie, the thickness direction of the ring) is preferably the vertical direction of the step 4, the vertical surfaces 5 and 12, and the vertical surfaces 6 and 13 of the step.

Examples of the material of the focus ring of the present invention include glassy carbon, quartz, single crystal silicon, and polycrystalline silicon. A focus ring which does not generate metal impurities and easily exhibits good characteristics can be obtained. Therefore, glassy carbon is preferable. here,
The glassy carbon is an amorphous carbon material having a glassy property obtained by firing and carbonizing a cured product of a thermosetting resin. The thermosetting resin used is not particularly limited, and examples thereof include a phenol resin, an epoxy resin, an unsaturated polyester resin, a furan resin, a melamine resin, an alkyd resin, a xylene resin, and a mixture of these resins. Above all, furan resin, phenolic resin, or a mixed resin thereof is preferable because glassy carbon having good characteristics can be obtained.

A curing agent is used according to the type of the thermosetting resin. Examples of the curing agent include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; organic sulfonic acids such as p-toluenesulfonic acid and methanesulfonic acid; and carboxylic acids such as acetic acid, trichloroacetic acid, and trifluoroacetic acid. Examples of the alkali include ammonia, amine, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like. The curing agent is preferably used in an amount of 0.001 to 20% by weight based on the thermosetting resin.

The thermosetting resin is molded by various molding methods according to the desired shape after the addition of the curing agent as required, and then cured. This curing is 130-200
The heat treatment is preferably performed at a temperature of ° C. In order to obtain a stable resin plate, it is preferable that the molding and curing of the resin be performed under a heating condition and a heating rate in which the amount of catalyst for curing is set to an appropriate amount and condensed water or the like easily escapes to the outside.

Next, after performing a predetermined processing for forming a shape of the focus ring, a highly purified jig and a furnace are used in an inert atmosphere (usually, an inert gas such as helium, argon, nitrogen, hydrogen or the like). , An oxygen-free atmosphere composed of at least one kind of non-oxidizing gas such as halogen gas, under reduced pressure or vacuum),
It is calcined and carbonized at a temperature of 2500 ° C., particularly preferably about 1000 ° C. Then, heat treatment is preferably performed at a temperature of 1300 to 3500 ° C. to obtain glassy carbon. In addition,
In addition to the above method, a larger molded and cured product is carbonized and fired in the furnace in the atmosphere to form glassy carbon, and then processed into a focus ring shape by a known method such as drilling, electric discharge machining, or ultrasonic machining. May be. Then, the obtained focus ring can be subjected to the finish processing of the surface polishing in order to obtain the 10-point average surface roughness.

The plasma etching apparatus of the present invention has the above-mentioned focus ring, and the configuration of the other apparatuses is not particularly limited. An example of the device is shown in FIG. FIG. 3 is a schematic sectional view of a parallel plate type plasma etching apparatus. In FIG. 3, the plasma etching apparatus 17 includes an upper electrode 18 and a lower electrode 19.
Are provided, and a focus ring 20 is provided on the lower electrode. The silicon wafer 21 is etched by an etching process gas blown from the upper electrode. In the plasma etching apparatus according to the present invention, the idle discharge time for reducing the initial discharge foreign matter after the replacement of the focus ring is short.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Examples 1 to 9 and Comparative Examples 1 to 4 Furan resin precondensate (VF-30 manufactured by Hitachi Chemical Co., Ltd.)
2) To 100 parts by weight, 0.3 parts by weight of paratoluenesulfonic acid and 0.3 parts by weight of ethylene glycol were added, and after sufficient mixing, the resin was poured into a mold and heated at 50 ° C for 3 days at 70 ° C.
After drying and curing at 90 ° C. for 3 days, the temperature is raised to 160 ° C. at a rate of 5 ° C./hour, kept at 160 ° C. for 3 days, and cured to perform a 5 mm thick disk-shaped resin molded article having a diameter of 350 mm. I got Pre-sintering dimensional shrinkage (approximately 20% shrinkage)
After processing into a predetermined shape that allows for
The temperature was raised at a rate of ° C./hour, and a curing treatment was carried out at 160 ° C. for 3 days to obtain a disk-shaped resin molded product. The molded body is placed in an electric furnace and calcined and carbonized at a temperature of 1000 ° C. in a nitrogen stream, and then subjected to a high-temperature treatment at a temperature of 2000 ° C. in an inert atmosphere using a jig and an atmosphere furnace which have been treated with high purity. A carbon disk was obtained. The glassy carbon disk is processed by an ultrasonic processing machine, and has a ring shape of 260 mm in outer diameter, 198 mm in inner diameter, and 3.5 mm in thickness, and has a step of 3.5 mm in width and 0.5 mm in depth at the inner periphery. I made a focus ring. Further, the main plane of the focus ring was polished with a buff cloth using a polishing machine and a diamond paste as an abrasive. In addition, in order to obtain different surface roughness, polishing was performed by changing the size of the abrasive grains of the diamond paste. Also, the surfaces other than the main plane were polished with a diamond paste in the same manner to finish the surface to a uniform required surface roughness. After the polishing, ultrasonic cleaning with an organic solvent and pure water was performed.

Tables 1 and 2 show the 10-point average surface roughness (Rz) of each surface of the focus ring obtained in each of the examples and comparative examples. As a measuring device, a surface roughness profile measuring device Surfcom 503B manufactured by Tokyo Seimitsu Co., Ltd. was used. Note that Rz was measured for each surface at five points extracted at equal intervals from the entire surface, and Tables 1 and 2 show the maximum values among them. The reference length for the measurement of Rz was 0.8 mm, and the measurement was performed in the preferred direction described above.

Next, the focus ring was set in an 8-inch silicon wafer plasma etching apparatus. FIG. 1 is an enlarged cross-sectional view of the focus ring and its periphery. Next, empty discharge was performed while flowing a halogen-based reaction gas, and the time required until the number of discharged foreign substances on the wafer became 15 or less and the wafer became stable was evaluated. Tables 1 and 2 show the time required for the number of discharged foreign substances to stabilize as a blank discharge time.

[0021]

[Table 1]

[0022]

[Table 2]

Examples 10 to 14 and Comparative Examples 5 to 7 The same resin as in the above example and the glassy carbon disk obtained by the same steps were processed in the same manner to give an outer diameter of 290.
A ring-shaped focus ring having a diameter of 200 mm, an inner diameter of 200 mm and a thickness of 2.5 mm was manufactured. Further, each surface of the focus ring was processed by the same method using the same resin as in the above-described example and a glassy carbon disk obtained by the same process, and the outer diameter was 290 mm, the inner diameter was 200 mm, and the thickness was 2.5 mm. A focus ring with a ring shape was manufactured. Polishing was carried out in the same manner as in the above-mentioned embodiment with changing surface roughness, and washing was performed to finish. Next, the focus ring was evaluated for the free time until the number of foreign particles on the wafer was stabilized by the same method as described above. FIG.
FIG. 2 shows an enlarged cross-sectional view of the focus ring and its periphery. Also, Table 3 shows the roughness of each surface of the focus ring and the time until the number of discharge foreign substances is stabilized as an idle discharge time.

[0024]

[Table 3]

[0025]

The focus ring according to the first aspect of the present invention is very useful in industry because the idle discharge time for reducing the initial discharge foreign matter is short, and the productivity of etching can be improved. In the plasma etching apparatus according to the second aspect, the idle discharge time for reducing the initial discharge foreign matter after the replacement of the focus ring is short, and the etching productivity is high.

[Brief description of the drawings]

FIG. 1 is a partially enlarged sectional view showing an example of a state where a focus ring of the present invention is installed.

FIG. 2 is a partially enlarged sectional view showing an example of a state where a focus ring of the present invention is installed.

FIG. 3 is a schematic sectional view showing one example of a plasma etching apparatus of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 focus ring 2 main plane 3 step horizontal plane 4 step vertical plane 5 outer circumference vertical plane 6 inner circumference vertical plane 7 back surface 8 silicon wafer 9 lower electrode 10 focus ring 11 main plane 12 outer circumference vertical plane 13 inner circumference vertical plane 14 back surface 15 silicon wafer Reference Signs List 16 lower electrode 17 plasma etching apparatus 18 upper electrode 19 lower electrode 20 focus ring 21 silicon wafer

Claims (2)

[Claims] 1. A focus of a plasma etching apparatus in which a 10-point average surface roughness of a main plane contacting plasma is 5 μm or less, and a 10-point average surface roughness of a surface other than the main plane which is in contact with plasma is 30 μm or less. ring. 2. A plasma etching apparatus comprising the focus ring according to claim 1.