JP2628448B2 - Mirror polishing method for semiconductor substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror polishing method for a semiconductor substrate, which is capable of polishing a required number of pieces in one lot at the same time by using a plurality of mirror polishing apparatuses, thereby enabling extremely high precision mirror polishing. The thickness of the substrate is measured, and those within a predetermined range are collected in the same buffer based on the thickness of the substrate initially unconditionally sorted, and a plurality of substrates having the same substrate thickness are simultaneously processed by the same mirror polishing apparatus. The present invention relates to a method for mirror-polishing a semiconductor substrate which is polished to realize highly accurate and highly efficient mirror-polishing.

[0002]

2. Description of the Related Art At present, mirror polishing of a semiconductor substrate such as silicon is most commonly performed by so-called single-side polishing in which only one side is polished. To explain a general mirror polishing apparatus, a polishing platen on which a plurality of semiconductor substrates are attached is pressed against a polishing cloth made of polyurethane resin or the like adhered to a rotary table with a predetermined pressure, and a particle size of about 5 to 300 nm, for example. the SiO ₂ abrasive grains with caustic soda, and about pH9~12 are suspended in an alkaline solution such as ammonia and ethanolamine, using a polishing solution comprising a so-called colloidal silica, it is relatively rotated, the machine according to the abrasive grains Polishing by a mechanochemical polishing method utilizing both the chemical action and the chemical action by etching of an alkaline solution.

There are various methods for fixing a semiconductor substrate to a polishing platen, and a wax mount method of attaching with a wax or the like is disclosed in JP-A-1-210.
No. 259, Japanese Unexamined Patent Publication No. 1-289657, etc., there are mirror polishing apparatuses, and as a waxless mount type adsorbing to a polishing platen, Japanese Patent Application Laid-Open Nos. 64-2858 and 64-45567. There is a mirror polishing device shown.

[0004]

In any of the mirror polishing apparatuses having the above-mentioned various structures, not only high flatness but also micro-scratch and haze can be removed to obtain a high-quality polished surface without processing distortion. On the other hand, there is also a demand for improvement in polishing efficiency, which is contrary to high quality. When the polishing rate is increased to improve the polishing efficiency, it becomes difficult to obtain a high-quality polished surface.Therefore, a plurality of mirror polishing apparatuses are used to improve productivity. Variations may occur, and it is difficult to simultaneously maintain the respective polishing conditions constant with a plurality of mirror polishing apparatuses.

[0005] In particular, when a plurality of semiconductor substrates are mounted on a mirror polishing apparatus to improve productivity by simultaneously polishing the semiconductor substrates, if the thickness of the plurality of semiconductor substrates to be simultaneously polished varies, even in the same apparatus. The polishing conditions and the polishing accuracy are greatly different, and the variation is further enlarged in a plurality of mirror polishing apparatuses. Therefore, the thickness of the semiconductor substrate is measured, and the thickness is selected so as to be uniform within a predetermined range, for example, a range of ± 2 μm, and the predetermined number of semiconductor substrates are mounted on the same mirror polishing apparatus and polished. Can be considered.

When the thicknesses of the semiconductor substrates are made uniform, as a distribution method, a standard thickness of the thickness of each substrate and a distribution thickness range are set in advance, and the absolute value of the substrate to be buffered is determined from the numerical values. Is measured and the substrate is stored in a predetermined buffer according to the measured value. However, all of the required quantity in one lot
In the case where a large number of semiconductor substrates are stored in a buffer and the thicknesses are made uniform, when the absolute value of the substrates is determined in advance as described above, the variation in the substrate thickness within one lot is 20 μm, 2 μm, ten buffers are required, and a number of buffers in which the number of buffers in each buffer does not reach the predetermined number occurs, which causes problems such as impairing productivity. Further, when it is necessary to grind with a few pieces because the maximum number of pieces to be mounted is not uniform, there is a problem that the polishing conditions are not the same as those of other apparatuses and the obtained polishing accuracy varies.

[0007] This invention provides a mirror polishing method for a semiconductor substrate to be polished by mechanochemical polishing method, the required sheets using a plurality of mirror-polishing apparatus in order to improve productivity
The present invention provides a mirror polishing method for a semiconductor substrate capable of efficiently polishing substrates having substantially the same thickness when simultaneously polishing all of the lots in one lot, improving the polishing efficiency, and enabling extremely high precision mirror polishing. The purpose is.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a polished surface without processing distortion, and simultaneously improve the productivity by simultaneously maintaining the respective polishing conditions evenly by a plurality of mirror polishing apparatuses. As a result of various examinations on the method of allocating the substrate and the polishing method, the thickness of the second substrate is set within a predetermined range from the thickness of the first substrate without any condition being set in advance in the first buffer unconditionally. If it is out of the predetermined range, it is allocated to the second buffer, and if it is out of the predetermined range, it is allocated to the second buffer, and thereafter, the substrate initially allocated to each buffer is allocated to the same buffer based on the thickness. A large number of buffers are not required for the distribution, and a single time can be allocated, and a large number of fractional buffers that do not reach the specified number are not generated. Matter can as uniformly as possible maintaining, and knowledge to be able to realize a mirror polishing of high efficiency with high accuracy, and have completed the present invention. In addition, in the above-mentioned sorting, when the semiconductor substrate in the buffer of a fraction that does not reach the maximum mounting is mirror-polished, the pressure applied to the semiconductor substrate is reduced from the maximum mounting according to the number of sheets to be applied, and the surface pressure applied to the substrate is reduced. It has been found that by maintaining the value within a predetermined range, a predetermined polishing accuracy similar to that at the time of maximum mounting can be obtained, and the present invention has been completed.

That is, according to the present invention, a polishing cloth platen having a polishing cloth adhered to a surface thereof and a work platen on which a plurality of semiconductor substrates are arranged are brought into contact with each other to form a solution on the semiconductor substrate and / or the polishing cloth surface. Using a plurality of mirror polishers to grind by rotating the upper and lower platen plates relative to each other while supplying a polishing liquid in which abrasive grains are suspended, the required number of sheets in a lot is simultaneously processed.
In the mirror polishing method for a semiconductor substrate to be polished, the thickness of the semiconductor substrate is measured, and an arbitrary first substrate is placed in a first buffer, and a substrate having a thickness within a predetermined range based on the thickness of the first substrate is placed in the same buffer. The first substrate out of the range of the first buffer is allocated to the second buffer, and thereafter, the substrates having a thickness within a predetermined range are allocated to the same buffer based on the thickness of the substrate initially allocated to each buffer. A mirror polishing method for a semiconductor substrate, characterized in that substrates in a buffer are simultaneously polished by the same mirror polishing apparatus.

In addition, the present invention uses a plurality of the above-described mirror polishing apparatuses at the same time to make the required number of pieces in one lot the same.
In the mirror polishing method for a semiconductor substrate that is sometimes polished, when a semiconductor substrate that is smaller than the maximum number that can be placed on the work surface plate is placed, the pressure applied to the semiconductor substrate is changed according to the number of placed surfaces. A mirror polishing method for a semiconductor substrate, wherein the internal pressure is adjusted to a predetermined in-plane pressure which is a condition for polishing a maximum number of wafers in one batch.

In the present invention, when allocating while measuring the thickness of the semiconductor substrate, the thickness measurement, allocating, transporting to the polishing apparatus, etc. can be automated using a known mechanical mechanism or a control device using a computer. Therefore, the first substrate is unconditionally put into the first buffer without setting a standard for the thickness, and thereafter, the first substrate is used as a reference or the first substrate is allocated to each buffer. Since the substrates having a thickness within a predetermined range are allocated to the same buffer based on the thickness, automation and control conditions can be easily set. Further, in the present invention, high-precision polishing can be realized if the variation in the thickness of the substrate in the same buffer is 5 μm or less, and even higher precision can be realized if the variation in the thickness is 4 μm or less in the embodiment. For polishing, the thickness is preferably 2 μm or less.

In the present invention, the mirror polishing apparatus for a semiconductor substrate may be any known mirror polishing apparatus used in a mechanochemical polishing method using a polishing liquid such as colloidal silica. A plurality of suction chucks are rotatably mounted on the upper surface of the work surface plate to rotate, and a predetermined polishing cloth is adhered to the lower surface of the polishing cloth surface plate to attach to a semiconductor substrate on the suction chuck. Various configurations can be appropriately selected, such as a configuration in which the substrate is brought into contact with or supported so as to be able to move up and down to a predetermined position when the substrate is attached or detached.

In the present invention, any known polishing suspension used in the mechanochemical polishing method such as colloidal silica can be used as the polishing liquid. Select the capacity of the discharge pump according to the shape and position of the polishing liquid, the concentration of the polishing liquid, the number of equipment and the supply amount, etc., and polish any polishing liquid of multiple polishing equipment supplied from the polishing liquid tank by the discharge pump By recovering this later and providing a polishing liquid circulation supply path that can be returned to the polishing liquid tank, the polishing liquid can be stably supplied to a plurality of polishing apparatuses, and high-precision polishing can be performed. Become. The polishing liquid tank includes a polishing liquid supply pipe,
In addition to the return pipe, a supply pipe for abrasive grains and / or a solution and a drain pipe are provided, and for a while, the abrasive grains and / or the solution are determined according to the concentration of the abrasive grains measured by a concentration measuring instrument such as a hydrometer. Is supplied and the concentration of the abrasive grains in the polishing liquid tank is maintained at a predetermined concentration.

[0014]

According to the present invention, a plurality of semiconductor substrates having a uniform thickness are distributed and placed on a plurality of mirror polishing apparatuses in which mirror polishing conditions are set so that extremely high precision mirror polishing can be performed on a semiconductor substrate. In polishing, the first substrate is put into the first buffer while measuring the thickness of the semiconductor substrate, and the second substrate is distributed to the second buffer if the thickness of the second substrate is outside a predetermined range from the thickness of the first substrate. If the third sheet is within a predetermined range from the thickness of the first sheet, the work of allocating to the first buffer is performed,
Thereafter, the first substrate or the substrate initially allocated to each buffer is allocated to the same buffer with a thickness within a predetermined range based on the thickness, so that a predetermined number of semiconductor substrates having a uniform thickness within a predetermined variation range can be shortened. It is possible to set several buffers in time , and the substrates in each buffer that has reached the specified number are transported to the same mirror polishing device, placed on the work surface plate and polished at the same time. Not only high-precision polishing in the equipment, but also the polishing conditions in each mirror-polishing device can be equalized, so that variations in the mirror surface precision between a large number of substrates polished at the same time are reduced, realizing high-precision and high-efficiency mirror polishing. it can.

Further, according to the present invention, when a semiconductor substrate in a fractional buffer generated by the above-mentioned sorting is polished by the same mirror polishing apparatus, the pressure for pressing the substrate by the apparatus is reduced to reduce the pressure on each substrate. By adjusting the in-plane pressure to a predetermined in-plane pressure, which is a condition for polishing the maximum number of sheets in one batch, under the mirror polishing conditions set in advance so that highly accurate mirror polishing is possible, Since the substrate can be mirror-polished, a polishing amount equivalent to that obtained by polishing the maximum number of substrates in one batch by another apparatus can be stably obtained, and highly accurate and highly efficient mirror polishing can be realized.

[0016]

FIG. 1 is a perspective view showing the construction of a mirror polishing apparatus to which the present invention is applied, showing the rotation of a polishing cloth platen, a work platen and a suction chuck. In the mirror polishing apparatus to which the present invention is applied, as shown in FIG. 1, a plurality of suction chucks 2 are rotatably mounted on a work surface plate 1 arranged below,
The upper surface of the polishing pad 3 and the surface of the platen 1 are opposed to each other with the rotation axis slightly eccentric, so that the semiconductor substrate vacuum-adsorbed on the upper surface of the suction chuck 2 can revolve the platen 1. The rotation of the suction chuck 2, the rotation of the polishing pad 3, and the eccentricity of the rotating shafts of the upper and lower bases 1, 3 can be applied to perform the mechanochemical polishing to obtain a polished surface free of processing distortion. At the same time, it is configured to obtain an extremely high quality polished surface while improving the polishing efficiency.

Although not shown, the semiconductor substrate sorting apparatus firstly supports the outer peripheral portion of the first semiconductor substrate conveyed by the conveyor, raises the outer peripheral portion, and then uses the contact type thickness measuring device to raise the substrate. After measuring the thickness, the first substrate is inserted into the first buffer, the thickness of the second substrate is measured in the same manner, and the thickness of the second substrate is within a predetermined range from the thickness of the first substrate. Here, if within ± 2 μm, the data is allocated to the first buffer, and if it is out of the predetermined range, the data is allocated to the second buffer. If the third data is within the permissible range of the first data, that is, to the first buffer. If they are not within the allowable range of the first buffer and the second buffer, they are put into the third buffer, and thereafter, the substrates having a thickness within a predetermined range are distributed to the same buffer based on the thickness of the substrate first distributed to each buffer. Yo As described above, the measuring device and the control device of the transport device are programmed.

When the variation of the substrate thickness of about 100 substrates per lot is ± 20 μm, each buffer has ± 2 μm.
Conventionally, ten buffers are required to make the thickness within the range, but if the above-described semiconductor substrate sorting apparatus used in the present invention is used, the sorting is completed with the number of buffers of four and the conventional three-fourth buffer is used. It was time. In addition, using the above-mentioned mirror polishing apparatus of 5 pieces per batch, before polishing,
The maximum thickness difference between the maximum thickness in the sheet minus the minimum thickness is 2
Assuming various variations of μm to 10 μm, mirror polishing was performed under the same polishing conditions, and the flatness (TTV) of each substrate after polishing was measured. FIG. 2 shows the average value in the same batch as the relationship with the above-mentioned variation. As is clear from FIG. 2, the substrate thickness before polishing is at least 4 μm.
It can be seen that when the mirror polishing is carried out within the range, the average flatness of five batches after polishing is within 1 μm, and extremely high-precision polishing can be realized.

In addition, if five pieces are polished in one batch, but the number of pieces is four or less in the buffer, the polishing cloth platen is set in accordance with the number of substrates placed on the suction chuck 2 of the work platen 1. 3, the in-plane pressure applied to the substrate was adjusted to 200 g / cm ² in any case, and the mirror polishing was performed under the same conditions as the previously set polishing conditions for five batches. As a result, it was confirmed that a flatness equivalent to polishing of five sheets per batch with a thickness variation within ± 2 μm in each buffer was obtained.

[0020]

The present invention relates to a method for mirror-polishing a semiconductor substrate, in which a plurality of mirror-polishing apparatuses are simultaneously used to simultaneously grind all of the required number of pieces in one lot, the thickness of the semiconductor substrate is measured first, Based on the thickness of the substrate distributed according to the conditions, those within a predetermined range are collected in the same buffer, and if the value is outside the predetermined range, distributed to another buffer, so that the substrate thickness can be easily adjusted to the predetermined range with a small number of buffers. The thickness of the substrate is within the specified range, especially the dispersion is ± 2 μm.
By simultaneously polishing a plurality of substrates within the same mirror polishing device, the flatness of the polished substrate can be improved, and highly accurate and highly efficient mirror polishing can be realized. The fractional buffer generated by adjusting the in-plane pressure of each substrate to a predetermined in-plane pressure which is a condition for polishing the maximum number of sheets in one batch, and polishing the maximum number of sheets in one batch by another apparatus The same amount of polishing can be stably obtained, and highly accurate and efficient mirror polishing can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view showing rotation of a polishing cloth platen, a work platen, and a suction chuck of a mirror polishing apparatus to which the present invention is applied.

FIG. 2 shows thickness variation and T.P. T. V. 6 is a graph showing a relationship with the graph.

[Explanation of symbols]

 1 Work surface plate 2 Suction chuck 3 Polishing cloth surface plate

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-129991 (JP, A) JP-A-57-1655 (JP, A) JP-A-49-93990 (JP, A) JP-A 64-64 40265 (JP, A)

Claims (3)

(57) [Claims] An abrasive is applied to a solution on a surface of a semiconductor substrate and / or a polishing cloth by bringing a polishing table having a polishing cloth adhered on a surface thereof into contact with a work surface plate on which a plurality of semiconductor substrates are arranged. Mirror polishing equipment required for simultaneous rotation of the upper and lower platens while supplying suspended polishing liquid by using multiple units.
In mirror polishing method for a semiconductor substrate to polish the total number in one lot number simultaneously, responsibility by measuring the thickness of the semiconductor substrate
The first first substrate is placed in a first buffer, and substrates having a thickness within a predetermined range are distributed to the same buffer based on the thickness of the first substrate, and the first substrate outside the range of the first buffer is placed in a second buffer. After that, substrates having a thickness within a predetermined range are allocated to the same buffer based on the thickness of the substrate initially allocated to each buffer, and the substrates in each buffer are simultaneously polished by the same mirror polishing apparatus. Mirror polishing method for a semiconductor substrate. 2. The method for polishing a mirror surface of a semiconductor substrate according to claim 1, wherein the variation in the thickness of the substrate in the same buffer is 5 μm or less. 3. The method according to claim 1, wherein the pressure applied to the semiconductor substrate is set according to the number of the semiconductor substrates when the number of the semiconductor substrates is smaller than the maximum number of the semiconductor substrates that can be mounted on the work surface plate. A mirror polishing method for a semiconductor substrate, comprising adjusting an in-plane pressure on a substrate to a predetermined in-plane pressure which is a condition for polishing a maximum number of wafers in one batch.