JP2009082995A - Lapping polishing cloth, and method of lapping silicon electrode for plasma etching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lapping polishing cloth which can reduce occurrence of chipping. <P>SOLUTION: According to the lapping polishing cloth, a number of projections are regularly arranged on a substrate, and each projection is formed into a truncated conical shape having an angle θ formed by an upper surface and a side surface thereof set to the range of 105°<θ≤135°, or formed into an inverted truncated conical shape having the angle θ formed by the upper surface and the side surface set to the range of 45°≤θ<75°. Further provided that a total area of the upper surfaces of the projections is represented by S<SB>1</SB>, a polishing cloth surface area by S<SB>2</SB>, a height of each projection by H, a diameter of each upper surface by D<SB>1</SB>, and a diameter of a pore to be formed in a polishing object by D, respectively, the following relationships hold: 0.1S<SB>2</SB>≤S<SB>1</SB>≤0.9S<SB>2</SB>, 50 μm≤H≤1 mm, and D<SB>1</SB>≥2D. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lapping polishing cloth and a lapping method for a silicon electrode for a plasma etching apparatus using the lapping cloth, and more particularly to a lapping polishing cloth having an improved shape of a protrusion and a lapping method for a silicon electrode for a plasma etching apparatus using the lapping polishing cloth. About.

  Conventionally, a plasma etching apparatus has been widely used as an apparatus for etching a silicon wafer during the manufacture of a semiconductor integrated circuit. This plasma etching apparatus includes a large number of pores in a vacuum vessel 41 as shown in FIG. The electrode plate 42 having 42a and the wafer mounting table 43 are provided at an interval.

In the etching of the silicon wafer using this plasma etching apparatus, the silicon wafer W was mounted on the wafer mounting table 43, and an etching gas G containing CHF ₃ or CF _{3 in} addition to Ar was provided on the electrode plate 42. A high frequency voltage is applied between the electrode plate 42 and the wafer mounting table 43 by the high frequency power supply 45 while flowing toward the silicon wafer W through the through-hole 42a, and the supplied etching gas G is applied by applying this high frequency voltage. Becomes plasma P in the space between the electrode plate 42 and the wafer mounting table 43, and this plasma P hits the silicon wafer W to etch the surface of the silicon wafer W.

  The electrode plate 42 is usually made of carbon, glassy carbon, silicon carbide, silicon or the like.

  Among these materials, silicon electrodes using silicon are superior to carbon electrodes in terms of particle generation, wafer contamination, discharge of reactants, etching resistance of the electrodes themselves, and silicon electrodes are often used as electrode plates. ing.

  This silicon electrode is manufactured by cutting a silicon disk from a silicon ingot, drilling a large number of pores in the silicon disk with a drill, and wrapping the silicon disk provided with the pores.

  In this lapping, a double-sided or single-sided lapping machine is used, and a workpiece is pressed against a surface plate while supplying a slurry mixed with abrasive grains, and processing is performed while rotating.

  However, with the conventional lapping method, the larger the grain size of the abrasive grains, the larger the chipping size generated at the end of the pores during processing. Therefore, by selecting abrasive grains with a small grain size, the occurrence of chipping is suppressed. However, there is a problem that the processing efficiency deteriorates because the removal rate decreases as the grain size of the abrasive grains decreases.

  Of the chipping generated in the lapping process, additional polishing must be performed for the chipping that cannot be removed by a normal polishing amount in the subsequent polishing process, and the load of the polishing process has increased.

  In order to avoid such problems, there is a method of filling the inside of the pores with wax. However, the wax filled in the pores serves to suppress chipping during lapping, but the wax is removed after lapping. Cleaning is essential and complicates the manufacturing process.

  Therefore, there is a demand for means for suppressing the occurrence of chipping during lapping.

  As a result of studying means for suppressing the occurrence of chipping at the time of lapping, the present inventors have been able to suppress the occurrence of chipping by improving the shape of the protrusion provided on the lapping polishing cloth. And found the present invention.

In addition, a method of manufacturing a silicon electrode having a mirror surface by lapping the outer surface of a silicon disk after forming a plurality of gas flow pores in the silicon disk by ultrasonic machining, grinding, or the like is disclosed ( For example, see Patent Document 1).
JP-A-8-236505

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a lapping polishing cloth capable of suppressing the occurrence of chipping.

  It is another object of the present invention to provide a silicon electrode lapping method for a plasma etching apparatus with a simplified manufacturing process.

In order to achieve the above-described object, the lapping polishing cloth according to the present invention has a large number of protrusions regularly arranged on a substrate, and an angle θ formed by the upper surface and side surfaces of the protrusions is 105 ° <θ ≦ 135. Or a reverse frustoconical shape in which the angle θ between the upper surface and the side surface of the protrusion is 45 ° ≦ θ <75 °, and the total area of the upper surface of the protrusion is When S ₁ , the polishing cloth surface area is S ₂ , the height of the protrusion is H, the diameter of the upper surface is D ₁ , and the diameter of the pores provided in the wrapping material is D, 0.1 S ₂ ≦ S ₁ ≦ 0.9S ₂ , 50 μm ≦ H ≦ 1 mm, and D ₁ ≧ 2D.

  The method for lapping a silicon electrode for a plasma etching apparatus according to the present invention uses a step of cutting a silicon disk from a silicon ingot, a step of drilling a large number of pores in the silicon disk with a drill, and the lapping polishing cloth. And a step of wrapping the silicon disk provided with the pores.

  According to the lapping polishing cloth of the present invention, it is possible to provide a lapping polishing cloth capable of suppressing the occurrence of chipping.

  In addition, according to the silicon electrode lapping method for a plasma etching apparatus according to the present invention, it is possible to provide a silicon electrode lapping method for a plasma etching apparatus with a simplified manufacturing process.

  A lapping polishing cloth according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view of a lapping polishing cloth according to a first embodiment of the present invention, and FIG. 2 is a side view thereof.

  As shown in FIGS. 1 and 2, a lapping polishing cloth 1 according to a first embodiment of the present invention is used by being attached to a surface plate of a conventional lapping machine. A large number of protrusions 3 are regularly arranged, and the frustoconical shape is such that the angle θ formed between the upper surface 3a and the side surface 3b of the protrusion 3 is 105 ° <θ ≦ 135 °.

  By providing the polishing cloth projection edge with an inclination rather than a right angle, the processing resistance applied to the end of the pore during processing is dispersed to suppress the occurrence of chipping as much as possible. In this frustoconical shape, when the angle θ is 75 ° or more and 105 ° or less, the effect of suppressing chipping cannot be obtained, and when the angle θ is larger than 135 °, the amount of change in the area of the upper portion of the polishing cloth protrusion due to the wear of the polishing cloth is large. As a result, the polishing speed changes, and the processing speed decreases.

Furthermore, S ₁ to the total area of the upper surface _3a, when the polishing cloth surface area S _2, the height of the projections 3 H, D ₁ the diameter of the upper surface _3a, the diameter of the pores provided in the object to be polished is D, 0.1S ₂ ≦ S ₁ ≦ 0.9S ₂ , 50 μm ≦ H ≦ 1 mm, and D ₁ ≧ 2D.

  A three-dimensional structure of diamond abrasive grains (particle diameter: several μm to several tens μm) is formed on the protrusion (abrasive material layer) 3 by a resin binder (acrylic).

  The protrusions 3 are regularly arranged, for example, arranged at an equal pitch in one direction (X-axis direction), and the next row is arranged shifted by a half pitch.

S ₁ the total area of the upper surface 3a is the area of one of the upper surface 3a, sought by the product of the protrusion 3 number, the polishing cloth surface area S ₂ is the total area and S _1, the surrounding area of all protrusions 3 And the sum of the exposed area of the substrate 2. If S ₁ is out of the range of 0.1S ₂ ≦ S ₁ ≦ 0.9S ₂ , the chipping suppression effect cannot be obtained.

  The height H of the protrusion 3 is the distance between the surface of the base material 2 and the upper surface 3a.

  If the height H is greater than 1 mm, the protrusion may be deformed or dropped due to the load applied to the protrusion, and the polishing accuracy will be reduced. Further, when the height H is smaller than 50 μm, polishing scraps and the like generated by polishing are accumulated in the grooves between the protrusions, and the discharge of the polishing scraps is delayed, so that the polishing rate is changed and the polishing accuracy is lowered. There is a fear.

Further, a D ₁ is 2D smaller, easily protrusion enters the pores, it becomes easier to catch the pore edges, chipping suppressing effect can not be obtained, chipping.

  According to the lapping polishing cloth of the first embodiment, a lapping polishing cloth capable of suppressing the occurrence of chipping is realized.

  Next, a lapping polishing cloth according to a second embodiment of the present invention will be described.

  In the second embodiment, the protrusion of the first embodiment has a frustoconical shape, whereas the protrusion has an inverted frustoconical shape.

  For example, as shown in FIGS. 3 and 4, in the lapping polishing cloth 11 according to the second embodiment of the present invention, a large number of protrusions 13 are regularly arranged on the base material 2, and the upper surface 13 a of the protrusions 13. And the side surface 13b has an inverted truncated cone shape in which the angle θ is 45 ° ≦ θ <75 °.

  By making the angle θ an acute angle, the wear of the protrusion edge is promoted, and the tip angle is always rounded, thereby dispersing the processing resistance applied to the pore end during processing and generating chipping. Minimize as much as possible.

  In this inverted frustoconical shape, if the angle θ is not less than 75 ° and not more than 105 °, the chipping suppression effect cannot be obtained and chipping occurs. If the angle θ is smaller than 45 °, the amount of change in the area of the upper portion of the polishing cloth projection due to the use polishing of the polishing cloth increases, and the polishing speed changes, so that the processing accuracy decreases.

  Other configurations are not different from the lapping polishing cloth shown in FIG. 1 and FIG.

  A lapping polishing cloth according to a third embodiment of the present invention will be described.

  In the third embodiment, the frustoconical protrusions of the first embodiment and the inverted frustoconical protrusions of the second embodiment coexist.

  For example, as shown in FIGS. 5 and 6, the lapping polishing cloth 21 according to the third embodiment of the present invention has a large number of protrusions 3 and 13 regularly arranged on the base 2, The conical protrusions 3 and the inverted frustoconical protrusions 13 are alternately arranged in one direction.

  A silicon electrode manufacturing method using the silicon electrode lapping method for a plasma etching apparatus according to an embodiment of the present invention will be described with reference to a manufacturing flowchart shown in FIG.

  As shown in FIG. 7A, the silicon disk P is cut out from the silicon ingot (P1).

  As shown in FIG. 7B, a large number of pores p are formed in the silicon disk P with a diamond drill (P2).

  As shown in FIG. 7 (c), the lapping polishing cloth 1 of the first embodiment is attached to the upper surface plate L1 and lower surface plate L2 of the lapping machine, and the silicon disk P is sandwiched between the surface plates L1 and L2. The wrapping is performed while supplying water or water mixed with water-soluble oil for the purpose of lubrication and cooling (P3).

  In this lapping step, the protrusion 3 has a frustoconical shape in which the angle θ formed by the upper surface 3a and the side surface 3b is 105 ° <θ ≦ 135 °, so that occurrence of chipping is suppressed.

  This polishing cloth has a structure as shown in FIG. 2, and diamond abrasive grains (particle diameter: several μm to several tens μm) are formed on the frustoconical protrusions (abrasive layer) by a resin binder (acrylic). ), And these are regularly arranged on one side of the substrate. This frustoconical shape has the effect of reducing the risk of chipping occurring in the pore openings during lapping.

  As shown in FIG. 7D, the lapped silicon disk P is immersed in a mixed acid and etched (P4).

  As shown in FIG. 7E, the etched silicon disk P is polished by being sandwiched between upper and lower surface plates to which a polishing cloth is attached (P5).

  As shown in FIG. 7F, after the polishing is completed, the silicon disk P is taken out, and the silicon electrode is completed (P6).

  The completed silicon electrode has no chipping. All chipping that occurs in lapping is removed by the subsequent polishing process, so there is no need for additional polishing, and no method of filling the inside of the pores with wax is used. The process is simplified.

(Test 1)
In order to manufacture a silicon electrode having pores of about φ0.5 mm, lapping was performed using a double-sided lapping machine.

The polishing cloth of the first embodiment shown in FIG. 2 is used. For example, the protrusion height H is about 800 μm, the upper surface diameter D ₁ is about 3 mm, and the angle formed by the upper surface and the straight line on the side is 120 °. (Example 1).

  The wrapping result is shown in FIG. As can be seen from FIG. 8, by using the present invention, the removal rate is 1.7 times and the crushed layer depth is 0.16 times that of the conventional example (FO # 1000), and both the processing efficiency and quality are improved. .

(Test 2)
In the same manner as in Test 1, the angle θ formed between the upper surface and the side surface of the protrusion was changed (first and second embodiments), and the chipping occurrence state of the pore opening was examined.

  The results are shown in FIG. There is a correlation as shown in FIG. 9 between the angle θ and the chipping area ratio (%). It can be seen that selecting the optimum θ has the effect of suppressing the occurrence of chipping.

  It can be seen that 45 ° ≦ θ <75 ° and 105 ° <θ ≦ 135 ° are preferable. Outside this range, in the drilling process, there is a crushed layer on the inner wall of the pore, and when it comes into contact with the polishing cloth (projection part) in the lapping process, processing resistance is applied to the end of the pore. This causes chipping. By providing the polishing cloth protrusion edge with an inclination instead of a right angle, the polishing cloth of the first embodiment aims to disperse the processing resistance applied to the end of the pore during processing and suppress the occurrence of chipping as much as possible. The abrasive cloth of the second embodiment promotes the wear of the protrusion edge by making θ an acute angle, and has the same effect as the first embodiment by always having a rounded tip angle at 45 degrees. It is the target.

On the other hand, in consideration of pressure fluctuations within the life of the polishing pad (which leads to fluctuations in the removal rate), the larger θ is away from 90 °, the larger this fluctuation is, and the upper surface diameter D _{1 of the} protrusion is larger. It becomes more prominent as it gets smaller.

  As shown in FIG. 10, when both the chipping suppression effect and the stability of the processing conditions (removal rate) are taken into consideration, the values of the protrusions θ are contradictory.

  Therefore, a polishing cloth combining the protrusions of the first and second embodiments, such as the polishing cloth of the third embodiment, can be considered. By setting the values of the protrusions θ and θ ′ at this time as θ + θ ′ = 180 (45 ° ≦ θ <75 °), the contact area between the polishing cloth and the silicon electrode can always be kept constant. It is also possible to suppress chipping while stabilizing the machining conditions.

  In FIG. 10, as for the chipping suppression effect, the chipping area ratio (see FIG. 9) is “X” when the chipping area ratio is 2% or more, “Δ” when 1.5-2%, and 1.5% or less. The thing was made into "circle".

As for the stability of the processing conditions, by _{D 1} is about 3mm of the polishing pad projections about 4.5 mm (abrasive cloth of the first embodiment) (polishing cloth of the second embodiment), the height 800 [mu] m (polishing (○ mark) when the removal rate fluctuation rate is 15% or less when using from 50 μm (abrasion cloth life end) to the beginning of the cloth life, and “△ mark” when the removal rate fluctuation rate is 15 to 30%. Those with a removal rate fluctuation rate of 30% or more were designated as “x”.

“Removal rate fluctuation rate (%)
= (Maximum removal rate−minimum removal rate) / maximum removal rate × 100 ”

(Test 3)
Test 1 In the same manner as, the total area of the upper surface 3a with the polishing cloth surface area S ₁ by changing the relation of S _2, examine the chipping inhibiting effect.

The result shown in FIG. 11 was obtained. As can be seen from FIG. 11, in the range of 0.1S ₂ ≦ S ₁ ≦ 0.9S ₂ , the chipping suppression effect was obtained, and the occurrence of a large number of chippings was not recognized (the result is indicated by ○), When S ₁ = 0.01S ₂ and 1.1S ₂ outside this range, the chipping suppression effect was not obtained, and numerous chippings were observed (results are indicated by x).

(Test 4)
In the same manner as in Test 1, the chipping suppression effect is examined by changing the height H of the protrusions.

  The result shown in FIG. 12 was obtained. As can be seen from FIG. 12, when H is in the range of 50 μm ≦ H ≦ 1 mm, the chipping suppression effect is obtained, and the occurrence of a large number of chippings was not recognized, but outside this range, H = 40 μm, 1.2 mm However, the chipping suppression effect was not obtained, and many chippings were observed.

(Test 5)
Test 1 In the same manner as, the diameter of the upper surface of the protruding portion a diameter of D ₁ and pore alter the relationship and D, examine the chipping inhibiting effect.

The result shown in FIG. 13 was obtained. As can be seen from FIG. 13, the chipping suppression effect was obtained in the range of D ₁ ≧ 2D, and the occurrence of a large number of chippings was not recognized. However, when D ₁ = 1.8D outside this range, the chipping suppression was achieved. The effect was not obtained, and many chippings were observed.

The top view of the polishing cloth for lapping which concerns on 1st Embodiment of this invention. The side view of the lapping polishing cloth which concerns on 1st Embodiment of this invention. The top view of the polishing cloth for lapping which concerns on 2nd Embodiment of this invention. The side view of the polishing cloth for lapping which concerns on 2nd Embodiment of this invention. The top view of the polishing cloth for lapping which concerns on 3rd Embodiment of this invention. The side view of the polishing cloth for lapping which concerns on 3rd Embodiment of this invention. The manufacturing flow figure of the manufacturing method of the silicon electrode using the lapping method of the silicon electrode for plasma etching apparatuses of one Embodiment of this invention. The result figure which shows the processing state of the test using the polishing cloth for lapping of this invention. The result figure which shows the chipping generation | occurrence | production state of the test using the polishing cloth for lapping of this invention. The result figure which shows the effect of protrusion part angle (theta) of the test using the lapping abrasive cloth of this invention. The result figure which shows the effect of the correlation of the total area of the upper surface of the test using the polishing cloth for lapping of this invention, and a polishing cloth surface area. The result figure which shows the effect of the height of the protrusion part of the test using the polishing cloth for lapping of this invention. The result figure which shows the effect of the correlation of the diameter of the upper surface of the protrusion part of a test using the polishing cloth for lapping of this invention, and the diameter of a pore. The conceptual diagram of a general plasma etching apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing cloth for lapping 2 Base material 3 Protrusion part 3a Upper surface 3b Side surface

Claims (3)

A large number of protrusions are regularly arranged on the substrate, and a frustoconical shape in which an angle θ formed by the upper surface and the side surface of the protrusion is 105 ° <θ ≦ 135 ° is formed, or the upper surface and the side surface of the protrusion An inverted frustoconical shape with an angle θ between 45 ° ≦ θ <75 ° is formed,
When the total area of the upper surface of the protrusion is S ₁ , the surface area of the polishing cloth is S ₂ , the height of the protrusion is H, the diameter of the upper surface is D ₁ , and the diameter of the pores provided in the wrapping material is D ,
0.1 S ₂ ≦ S ₁ ≦ 0.9 S ₂ , 50 μm ≦ H ≦ 1 mm, D ₁ ≧ 2D
A lapping polishing cloth characterized by having the following relationship: The lapping abrasive cloth according to claim 1, wherein the frustoconical protrusions and the inverted frustoconical protrusions are alternately arranged in one direction. Cutting out a silicon disk from a silicon ingot;
Drilling a large number of pores in a silicon disk with a drill;
A method for lapping a silicon electrode for a plasma etching apparatus, comprising the step of lapping a silicon disk provided with pores using the lapping polishing cloth according to claim 1.

Images