JP2001062710A - Table for wafer polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a table for a wafer polishing device capable of coping with the trend toward larger bore and higher quality in a semiconductor wafer by making flatness of a polishing surface maintainable. SOLUTION: A wafer polishing device 1 is provided with a table 2 and a wafer hold plate 6. A semiconductor wafer 5 held to a hold surface 6a of the plate 6 is brought into slide contact with a polishing surface 2a provided in an upper part of the table 2. The table 2 is formed by using a material with Young's modulus 1.0 kg/cm2 (×106) or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a table for a wafer polishing apparatus.

[0002]

2. Description of the Related Art Generally, a mirror wafer having a mirror surface can be obtained by slicing a single crystal silicon ingot thinly and polishing it through a lapping step and a polishing step. In particular, when the epitaxial growth layer forming step is performed after the lapping step and before the polishing step, an epitaxial wafer can be obtained. Then, these bare wafers are oxidized,
Various processes such as etching and impurity diffusion are repeatedly performed, and finally a semiconductor device is manufactured.

In the above series of steps, it is necessary to polish the device formation surface of a semiconductor wafer by using some means. Therefore, various types of wafer polishing apparatuses (lapping machines, polishing machines, and the like) have been conventionally proposed.

A typical wafer polishing apparatus includes a table, a pusher plate, a cooling jacket, and the like. A table made of stainless steel or the like is fixed to an upper portion of the cooling jacket. Cooling water is circulated through a flow path provided in the cooling jacket. On the holding surface of the pusher plate,
A semiconductor wafer is applied using a thermoplastic wax. The semiconductor wafer held by the rotating pusher plate is pressed from above onto the polished surface of the table. As a result, the semiconductor wafer comes into sliding contact with the polishing surface, and one side surface of the wafer is uniformly polished. Then, the heat generated in the wafer at this time is conducted to the cooling jacket via the table, and is taken out of the apparatus by the cooling water circulating in the flow path.

[0005]

However, since the pressing force is applied to the polished surface of the table by the pusher plate during use, the table may be bent as a whole. Then, with the deterioration of the flatness of the polished surface, it becomes impossible to perform polishing with high accuracy, and the flatness of the wafer also decreases. In addition, it is expected that such a deflection becomes more remarkable as the table becomes larger. Therefore, in order to realize high quality and large diameter wafers,
It is essential to take some measures to prevent deflection.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to maintain the flatness of a polished surface. To provide a table for use.

[0007]

According to the first aspect of the present invention, a semiconductor wafer held on a holding surface of a wafer holding plate constituting a wafer polishing apparatus is slid. On a table having a polishing surface to be in contact with the upper portion thereof, the Young's modulus was 1.0 kg / cm ² (× 1
0 ⁶⁾ or more wafer polishing apparatus table which is formed by using a table forming material as its gist.

According to a second aspect of the present invention, in the first aspect, the table forming material is a ceramic. According to a third aspect of the present invention, in the first aspect, the table forming material is a silicon carbide sintered body.

According to a fourth aspect of the present invention, in the third aspect, the silicon carbide sintered body is a dense body. According to a fifth aspect of the present invention, in the fourth aspect, the silicon carbide sintered body has a Young's modulus of 1.0 to 5.0 kg / cm ² (× 10 ⁶ ).

[0010] In the invention according to claim 6, a plurality of ceramic base materials are stacked on each other, and are held on a holding surface of a wafer holding plate constituting a wafer polishing apparatus above the stacked structure. In a table having a polishing surface on which a semiconductor wafer slides, a table for a wafer polishing apparatus in which the ceramic base material has a Young's modulus of 1.0 kg / cm ² (× 10 ⁶ ) or more.

Hereinafter, the "action" of the present invention will be described. According to the first to sixth aspects of the present invention, a table formed using a material having a high Young's modulus has a suitable rigidity. For this reason, even if a pressing force is applied to the polishing surface during use, the table does not flex and deform as a whole. Therefore, as a result of maintaining the flatness of the polished surface, it becomes possible to polish with high accuracy,
The flatness of the obtained wafer is also improved.

In this case, the material for forming the table is preferably ceramics. Ceramics are generally superior in rigidity to metals and the like, and are also superior in heat resistance and wear resistance. Further, among ceramics, a silicon carbide sintered body, particularly a dense body of a silicon carbide sintered body, is preferably used as a material for forming a table. This is because such a silicon carbide sintered body is excellent in all of thermal conductivity, heat resistance, thermal shock resistance, wear resistance, rigidity and the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wafer polishing apparatus 1 according to one embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 shows a wafer polishing apparatus 1 according to this embodiment.
Is schematically shown. The table 2 constituting the wafer polishing apparatus 1 has a disk shape. The upper surface of the table 2 is a polishing surface 2a for polishing the semiconductor wafer 5. A polishing cloth (not shown) is attached to the polishing surface 2a. The table 2 according to the present embodiment is directly and horizontally fixed to the upper end surface of the cylindrical rotating shaft 4 without using a cooling jacket. Therefore, when the rotation shaft 4 is driven to rotate, the table 2 rotates integrally with the rotation shaft 4.

As shown in FIG. 1, the wafer polishing apparatus 1 includes a plurality (two in FIG. 1 for convenience of illustration) of wafer holding plates 6. As a material for forming the plate 6, for example, a glass, a ceramic material such as alumina, a metal material such as stainless steel, or the like is employed. A pusher bar 7 is fixed to the center of one side surface (non-holding surface 6b) of each wafer holding plate 6. Each pusher bar 7 is located above the table 2 and is connected to driving means (not shown). Each pusher bar 7 horizontally supports each wafer holding plate 6. At this time, the holding surface 6
a is in a state facing the polishing surface 2a of the table 2. Further, each pusher bar 7 can not only rotate with the wafer holding plate 6 but also move up and down within a predetermined range. Instead of the method of moving the plate 6 up and down, a structure of moving the table 2 up and down may be adopted. The semiconductor wafer 5 made of silicon is adhered to the holding surface 6a of the wafer holding plate 6 using, for example, thermoplastic wax. The semiconductor wafer 5 has a holding surface 6a
May be adsorbed by evacuation or electrostatically. At this time, the polished surface 5a of the semiconductor wafer 5
Must face the polishing surface 2a of the table 2.

When the apparatus 1 is a lapping machine, that is, an apparatus for polishing a wafer that has undergone a slicing step in a bare wafer process, the wafer holding plate 6 is preferably as follows. That is, it is preferable that the plate 6 slides the semiconductor wafer 5 in a state where a predetermined pressing force is applied to the polishing surface 2a. This is because, even if a pressing force is applied by such a wafer holding plate 6 (that is, a pusher plate), there is no need to worry about peeling of the epitaxial growth layer since the epitaxial growth layer is not formed. The same applies to a case where the apparatus 1 is a polishing machine for manufacturing a mirror wafer, that is, an apparatus that performs polishing without performing an epitaxial growth step on a wafer that has undergone the lapping step.

On the other hand, when the apparatus 1 is a polishing machine for manufacturing an epitaxial wafer, that is, an apparatus that performs an epitaxial growth step on a wafer that has undergone the lapping step and then performs polishing, the plate 6 is formed as follows. It is good to be something. That is, plate 6
It is preferable that the semiconductor wafer 5 is slid in contact with the polishing surface 2a with almost no pressing force applied. This is because the silicon epitaxial growth layer is easier to peel than single crystal silicon. This is basically the same when the apparatus 1 is a machine for performing chemical mechanical polishing (CMP) after various film forming steps.

Next, the configuration of the table 2 will be described in detail. As shown in FIGS. 1 and 2, the table 2 of the present embodiment has a plurality of (here, two) base materials 11A, 1A.
1B is a laminated ceramic structure obtained by laminating them as materials. On the bottom surface of the upper one (upper substrate 11A) of the two substrates 11A and 11B, grooves 13 forming a part of cooling water channel 12 as a fluid flow path are formed in a predetermined pattern. On the other hand, such a groove 13 is not particularly formed in the lower substrate 11B. The two substrates 11A and 11B are integrated by being joined to each other via a brazing material layer 14 as a metal-based adhesive layer. As a result, the water channel 12 is formed at the joint interface between the substrates 11A and 11B. A through hole 15 is formed at a substantially central portion of the lower substrate 11B. These through holes 1
5 is a flow path 4a provided in the rotating shaft 4 and the water channel 1
And 2 are communicated.

The ceramic material forming each of the bases 11A and 11B is preferably a silicide ceramic or a carbide ceramic. Particularly, in this embodiment, a dense body of a silicon carbide sintered body (SiC sintered body) using silicon carbide powder as a starting material is selected as the ceramic material. Therefore, in this embodiment, the same type of ceramic material is used for both of the two substrates 11A and 11B. In addition, the silicon carbide sintered body is preferable among the above ceramics because it is excellent in heat conductivity, heat resistance, thermal shock resistance, wear resistance, rigidity and the like.

The Young's modulus of both substrates 11A and 11B is 1.
0 kg / cm ² is required to be (× 10 ⁶⁾ above, it is desirable to specifically a ^{1.0~10.0kg / cm 2 (× 10 6} ), 1.0~5.0kg / Cm ² (× 10 ⁶ ) is particularly desirable. If the Young's modulus is smaller than the above value, sufficient rigidity cannot be given to the table 2. Conversely, the higher the Young's modulus, the better. On the other hand, if the Young's modulus exceeds 10.0 kg / cm ² (× 10 ⁶ ), it may be difficult to supply cheap and stable material.

The thickness of the upper substrate 11A is smaller than the thickness of the lower substrate 11B. This ensures that the thermal resistance of the upper substrate 11A is lower than the thermal resistance of the lower substrate 11B. In the present embodiment, the upper substrate 11
The thickness of A is set to 3 mm to 20 mm. The thickness of the lower substrate 11B is set to 10 mm to 50 mm.

As the silicon carbide powder, α-type silicon carbide powder, β-type silicon carbide powder, amorphous silicon carbide powder and the like are used. In this case, only one kind of powder may be used alone, or two or more kinds of powder may be combined (α type + β type,
α-type + amorphous, β-type + amorphous, or α-type + β-type + amorphous). Note that a sintered body manufactured using β-type silicon carbide powder contains more large plate-like crystals than a sintered body manufactured using other types of silicon carbide powder. Therefore, when it is desired to obtain a dense body, the grain boundaries of the crystal grains in the sintered body are reduced, and the sintered body can be particularly excellent in thermal conductivity.

The upper substrate 11A made of a silicon carbide sintered body preferably has a thermal conductivity of 40 W / mK or more.
It is desirable that it be 0 W / mK to 300 W / mK. If the thermal conductivity is too small, temperature variations are likely to occur in the sintered body, which may prevent the semiconductor wafer 5 from having a large diameter and high quality. Conversely, the higher the thermal conductivity is, the more preferable it is. On the other hand, if the thermal conductivity exceeds 300 W / mK, it is difficult to supply a low-cost and stable material. The thermal conductivity of the lower substrate 11B is preferably 5 W / mK or more, and more preferably 10 W / mK to 80 W / m.
K is desirable. The reason is that the cooling water channel 12
This is to prevent the heat radiation below the cooling section constituted by the above, thereby facilitating the temperature control of the polishing surface 2a.

The brazing material layer 14 is preferably formed using a brazing material containing titanium. When a silicon carbide sintered body is selected as the base materials 11A and 11B, by using a brazing material containing titanium, it is possible to obtain a high bonding strength while securing a high thermal conductivity in the brazing material layer 14. . Since titanium is easily diffused into pores of the sintered body at the time of brazing, at present, this property is considered to be a main factor for improving the bonding strength.

In this embodiment, a Ti-Ag-Cu (titanium-silver-copper) brazing material is used for joining the base materials 11A and 11B. The content of titanium in this brazing material is about 0.1% by weight to 10% by weight, and its melting temperature is about 850 ° C. Further, the thickness of the brazing material layer 14 is preferably set to about 10 μm to 50 μm.

The groove 13 forming a part of the water channel 12 is a grinding groove formed by grinding the bottom surface of the upper substrate 11A using a grindstone. The groove 13 is not limited to one formed by grinding, but may be one formed by injection processing such as sandblasting. Groove 13
Is preferably set to about 3 mm to 10 mm, and the width is set to about 5 mm to 20 mm.

Here, a procedure for manufacturing the table 2 will be briefly described. First, a mixture obtained by adding a small amount of a sintering aid to silicon carbide powder is uniformly mixed. As the sintering aid, boron and its compound, aluminum and its compound, carbon and the like are selected. This is because if a small amount of this kind of sintering aid is added, the crystal growth rate of silicon carbide increases, leading to densification and high thermal conductivity of the sintered body.

Next, the above mixture is used as a material to perform a die molding to produce a disk-shaped molded body.
Further, by firing this molded body in a temperature range of 1800 ° C. to 2400 ° C., the base material 1 made of a silicon carbide sintered body is fired.
Two 1A and 11B are manufactured. In this case, if the firing temperature is too low, not only is it difficult to increase the crystal grain size, but also many pores remain in the sintered body. Conversely, if the firing temperature is too high, the decomposition of silicon carbide starts, resulting in a reduction in the strength of the sintered body.

Subsequently, the bottom surface of the upper base material 11A is ground by using a grindstone, thereby forming a groove 13 having a predetermined width and a predetermined depth almost over the entire surface. Furthermore, two substrates 1
With the appropriate amount of brazing material placed between 1A and 11B, both 11A and 11B are laminated. In this state, the two substrates 11A and 11B are heated, and the substrates 11A and 11B are brazed together. Finally, the surface of the upper substrate 11A is polished to form a polished surface 2a having a surface roughness suitable for polishing the semiconductor wafer 5. Such a surface polishing step may be performed before the bonding step or the groove processing step. The table 2 of the present embodiment is completed through the above procedure. Hereinafter, an example that more specifically embodies the present embodiment will be introduced. [Example] As a silicon carbide powder containing 94.6% by weight of β-type crystal, “Beta Random (trade name)” manufactured by IBIDEN Corporation was used. The silicon carbide powder had an average crystal grain size of 1.3 μm and contained 1.5% by weight of boron and 3.6% by weight of free carbon.

First, 100 parts by weight of the silicon carbide powder was mixed with 5 parts by weight of polyvinyl alcohol and 300 parts by weight of water, and then mixed in a ball mill for 5 hours to obtain a uniform mixture. After drying the mixture for a predetermined time to remove a certain amount of water, an appropriate amount of the dried mixture was collected and granulated. Next, the granules of the mixture were molded using a metal mold under a pressing pressure of 50 kg / cm ² . The densities of the two obtained disk-shaped formed shapes were 1.
It was 2 g / cm ³ .

Next, the green compact was charged into a graphite crucible capable of shutting off outside air, and was fired using a tanman type firing furnace. The firing was performed in an argon gas atmosphere at 1 atm. Further, at the time of baking, heating was performed at a heating rate of 10 ° C./min to a maximum temperature of 2300 ° C., and thereafter, the temperature was maintained for 2 hours. Observation of the obtained two substrates 11A and 11B revealed that a very dense three-dimensional network structure in which plate-like crystals were entangled in multiple directions. Substrates 11A and 11B had a density of 3.1 g / cm ³ , a thermal conductivity of 150 W / mK, and a Young's modulus of 3.5 kg / cm ² (× 10 ⁶ ). The content of boron was 0.4% by weight, and the amount of free carbon was 1.8% by weight. Here, the dimensions of the substrates 11A and 11B are
The thickness was set to 00 mm and the thickness to 5 mm.

Subsequently, a groove 13 having a depth of 5 mm and a width of 10 mm is formed on the back surface of the upper substrate 11A by grinding.
The two substrates 11A and 11B were integrated by brazing. Here, a foil-like silver brazing material containing titanium was used, and the thickness of the brazing material layer 14 was set to 20 μm.

After the brazing step, the upper substrate 11A
The table 2 having a polished surface 2a having a surface roughness suitable for polishing the semiconductor wafer 5 was finally completed by subjecting the surface to polishing. The table 2 of the embodiment thus obtained was set in the above-mentioned various polishing apparatuses 1, and the cooling water W
Was constantly circulated while polishing semiconductor wafers (silicon wafers) 5 of various sizes. As a result, no bending was observed in the table 2 for any of the types, and the flatness of the polished surface 2a was surely maintained.

When the flatness of the wafer 5 obtained through polishing by various polishing apparatuses 1 was examined,
It was within 2 μm in mmφ. The flatness of the plate 6 at a temperature of 40 ° C. was within 5 μm. Of course, the wafer 5 was not damaged. That is, it was found that when the table 2 of the present embodiment was used, an extremely accurate and high quality semiconductor wafer 5 could be obtained.

Therefore, according to the embodiment of the present embodiment, the following effects can be obtained. (1) As described above, in the table 2 of the embodiment, two substrates 1 made of a dense silicon carbide sintered body having a high Young's modulus are used.
1A and 11B are formed as forming materials. Therefore, the table 2 is provided with a suitable rigidity. Therefore, even if a pressing force is applied to the polishing surface 2a during use, the table 2 does not bend and deform as a whole. Therefore, the flatness of the polished surface 2a is also reliably maintained. As a result, the wafer 5 can be polished with high accuracy, and the flatness of the obtained wafer 5 is surely improved. From the above, it is possible to provide the table 2 that can cope with an increase in diameter and quality of the semiconductor wafer 5.

(2) The base materials 11A and 11B made of a dense silicon carbide sintered body have very suitable properties as a table forming material as described above. Therefore, by using this, the flatness of the polishing surface 2a can be more reliably maintained. In addition, the table 2 can be provided with suitable thermal conductivity, heat resistance, thermal shock resistance, and wear resistance. Of course, this also contributes to increase in diameter and quality of the semiconductor wafer 5.

(3) Table 2 of this wafer polishing apparatus 1
In the example, the water channel 12 is formed at the joint interface between the silicon carbide substrates 11A and 11B. Therefore, the heat on the side of the polishing surface 2 a is conducted through the inside of the table 2 and the cooling water W flowing through the water passage 12 is formed.
Will be handed over. Therefore, heat can be directly and efficiently released from the table 2 as compared with a conventional apparatus in which the table 2 is placed on the cooling jacket to perform indirect cooling. Therefore, the temperature variation in the table 2 is also reduced. That is, the heat uniformity of the table 2 is improved, and this also enables high-precision processing of the wafer 5.

(4) In this table 2, two substrates 1
A laminated structure composed of 1A and 11B is employed. Therefore, after the structure (that is, the groove 13) that becomes the water channel 12 is formed in advance on the back surface of the upper base material 11A, the base materials 11A, 11
B can be joined together. Therefore, the base material 11A,
The water channel 12 can be formed relatively easily at the interface of 11B. Therefore, there is an advantage that there is no particular difficulty in manufacturing the table 2. Further, with this structure, it is not necessary to add a piping structure to the joint interface, so that the structure is not complicated and the cost is not increased.

(5) Two substrates 1 constituting the table 2
1A and 11B are firmly joined by brazing via a brazing material layer 14. Therefore, unlike the case where the layers are laminated without the brazing material layer 14 interposed therebetween, high bonding strength can be secured at the bonding interface. In addition, since the thermal stress is less likely to be generated on the table 2 as described above, crack breakage at the joining interface is reliably avoided. Therefore,
A high-strength table 2 that is difficult to break can be obtained.
In addition, as a result of avoiding breakage due to cracks, water leakage from the joint interface can be prevented beforehand.

The embodiment of the present invention may be modified as follows. -Instead of the table 2 of the embodiment having a two-layer structure, 3
It may be embodied in a table having a layer structure. Of course, a stacked structure of four or more layers may be used. In addition, since the water channel 12 is not an essential configuration, when this is omitted, the table may have a single-layer structure (that is, a non-laminated structure).

The groove 13 is formed on the upper substrate 1 as in the embodiment.
1A, and may be formed only on the lower substrate 11B.
May be formed on only the base material 11
A, 11B.

In the embodiment, the upper substrate 11A is formed using a dense silicon carbide sintered body, and the lower substrate 11B is formed using a porous silicon carbide sintered body. Was. Of course, the combination is not limited to such a combination.
1A and 11B may be formed, or both substrates 11A and 11B may be formed using a porous silicon carbide sintered body.

As silicide ceramics other than silicon carbide, for example, silicon nitride (Si ₃ N ₄ ) or sialon may be selected. As carbide ceramics other than silicon carbide, for example, boron carbide (B ₄ C) or the like may be used. You may choose.
Further, not only ceramics of this kind but also oxide ceramics represented by, for example, alumina or the like, or metal materials are allowed. However, even in these cases, the Young's modulus is 1.0 kg / cm ² (× 1
0 ⁶ ).

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments will be listed below together with their effects. (1) A polishing method using the table according to any one of claims 1 to 6, wherein the semiconductor wafer is polished against a polishing surface of the table while flowing a cooling fluid through the fluid flow path. A method for polishing a semiconductor wafer, wherein the semiconductor wafer is polished by rotating and sliding. Therefore, according to the invention described in the technical idea 1, the wafer is less likely to be adversely affected by heat during polishing, so that the wafer can be accurately polished, and a large-diameter and high-quality wafer can be obtained. it can.

(2) A manufacturing method using the table according to any one of claims 1 to 6, wherein the cooling fluid is caused to flow through the fluid flow path while the polishing surface of the table is polished. A method of manufacturing a semiconductor wafer, comprising at least a step of polishing the semiconductor wafer by bringing the semiconductor wafer into sliding contact with the semiconductor wafer while rotating the semiconductor wafer. Therefore, according to the invention described in the technical idea 2, the wafer is hardly affected by heat during polishing, and a large-diameter and high-quality wafer can be obtained.

[0046]

As described in detail above, according to the first to sixth aspects of the present invention, the flatness of the polished surface can be maintained.
It is possible to provide a table for a wafer polishing apparatus that can cope with an increase in diameter and quality of a semiconductor wafer.

According to the third, fourth, and fifth aspects of the present invention,
In addition to being able to more reliably maintain the flatness of the polished surface, it is possible to impart suitable thermal conductivity, heat resistance, thermal shock resistance, and wear resistance to the table.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a wafer polishing apparatus according to an embodiment of the invention.

FIG. 2 is an enlarged sectional view of a main part of a table used in the wafer polishing apparatus according to the embodiment.

[Explanation of symbols]

1. Wafer polishing device, 2. Table for wafer polishing device,
2a: polishing surface, 5: semiconductor wafer, 6: wafer holding plate, 6a: holding surface, 11A, 11B: base material.

Claims (6)

[Claims] 1. A table having a polished surface on which a semiconductor wafer held on a holding surface of a wafer holding plate constituting a wafer polishing apparatus is slidably contacted has a Young's modulus of 1.0 kg / cm ^2. (× 10 ⁶ ) A wafer polishing apparatus table formed using the above table forming materials. 2. A table for a wafer polishing apparatus according to claim 1, wherein said table forming material is ceramics. 3. The table for a wafer polishing apparatus according to claim 1, wherein said table forming material is a silicon carbide sintered body. 4. The table for a wafer polishing apparatus according to claim 3, wherein said silicon carbide sintered body is a dense body. 5. The silicon carbide sintered body has a Young's modulus of 1.0 to 1.0.
The table for a wafer polishing apparatus according to claim 4, wherein the weight of the table is 5.0 kg / cm ² (× 10 ⁶ ). 6. A semiconductor wafer held on a holding surface of a wafer holding plate constituting a wafer polishing apparatus is slidably contacted on an upper portion of a laminated structure formed by stacking a plurality of ceramic base materials. In a table having a polished surface, the ceramic substrate has a Young's modulus of 1.0 kg / cm ² (×
10 ⁶ ) The above table for a wafer polishing apparatus.