JP2971714B2 - 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 capable of extremely high precision mirror polishing, provided with a circulation supply system for recovering and reusing a polishing liquid, and polishing in a polishing liquid tank. Measures the abrasive grain concentration and keeps the abrasive grain concentration constant
In addition, the polishing liquid temperature is maintained at a constant temperature, and in a non-operating device, the polishing liquid is sent back to the return path, and the discharge amount of the pump is increased or decreased according to a pressure loss or the like, so that the total supply amount is always constant. Multiple mirror polishing machines by holding and maintaining stable supply of polishing liquid without being affected by the number of operating units
The polishing rate of each semiconductor substrate in the constant and uniform,
The present invention relates to a mirror polishing method for a semiconductor substrate which realizes 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. Since the high-quality polished surface and raise the polishing rate in order to improve the polishing efficiency can not be obtained, for example, 1 to 100 or more sheets of predetermined number
When simultaneously polishing all the components in a lot, a plurality of mirror polishing apparatuses are used to improve productivity. In this case, there is a possibility that the polishing surface varies between the apparatuses. It is difficult for a plurality of mirror polishing apparatuses to simultaneously maintain the respective polishing rates uniformly and constantly. In addition, a plurality of mirror polishing apparatuses are used to improve productivity. However, depending on the situation, the number of operating apparatuses fluctuates. Therefore, in a configuration in which the polishing liquid is supplied to a plurality of apparatuses by one pump, the polishing liquid is used each time. The supply amount fluctuates, and it becomes difficult to simultaneously and uniformly maintain the respective polishing rates in a plurality of mirror polishing apparatuses,
There are problems that the flatness varies and the productivity becomes unstable. Therefore, a configuration in which a pump is individually provided for each device is conceivable, but it is difficult to control a plurality of pumps in order to equalize the polishing conditions among the above-described devices while the number of operating units fluctuates. There is a problem that the device becomes complicated.

According to the present invention , a plurality of mirror polishing apparatuses are used in a mechanochemical polishing method to improve productivity.
In the mirror polishing method of simultaneously polishing a plurality of semiconductor substrates , the number of processed, i.e. , regardless of the number of operating,
A number of sheets polished at the same time with the polishing speed between
It is an object of the present invention to provide a mirror polishing method for a semiconductor substrate capable of improving polishing efficiency by minimizing a variation in mirror surface accuracy between substrates and enabling highly accurate mirror polishing.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a polished surface with no processing distortion and to improve productivity by simultaneously and uniformly maintaining respective polishing rates by a plurality of mirror polishing apparatuses. As a result of various studies on the supply method of the polishing liquid for the purpose, a circulating supply system for recovering and reusing the polishing liquid is provided, and the concentration of the polishing abrasive grains is measured in the polishing liquid tank to maintain the concentration of the polishing abrasive grains constant. It has been found that the polishing rate can be made uniform and constant in a plurality of mirror polishing machines, and high precision and high efficiency mirror polishing can be realized. The polishing liquid is constantly supplied at a stable flow rate, and for non-operating devices, the valve is switched back to the return path to maintain the total supply at all times. Realize And it found that that can, and have completed the present invention.

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. A plurality of mirror polishing apparatuses for semiconductor substrates are used, in which a plurality of mirror polishing apparatuses for polishing by rotating the upper and lower platens relatively while supplying a polishing liquid in which abrasive grains are suspended are arranged .
A mirror polishing method for a semiconductor substrate, which simultaneously polishes a semiconductor substrate, wherein a polishing liquid can be supplied from a polishing liquid tank to a plurality of mirror polishing apparatuses by a pump of a variable discharge amount and a polishing liquid after polishing. A circulation and supply system for the polishing liquid to be collected and returned to the tank for reuse, so that the polishing liquid to the apparatus can be sent back to the return path when the apparatus is not in operation, and the pressure and / or flow rate arranged in the supply path By changing the discharge amount of the pump with the sensor, the total circulating supply amount of the polishing liquid in the circulating supply system is always kept constant, and the polishing abrasive grain concentration in the polishing liquid tank is measured,
Supplying new abrasive grains and / or solution to maintain the concentration of polishing abrasive grains constant, placing a heat exchanger on the downstream side of the pump from the pump to maintain the temperature of the polishing liquid to be fed at a constant temperature, and starting operation A mirror polishing method for a semiconductor substrate, characterized in that a polishing rate of each semiconductor substrate in a mirror polishing apparatus is maintained at a predetermined rate.

[0008]

In the present invention, the mirror polishing apparatus for a semiconductor substrate can 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, and silica, alumina or the like is suitably used as the abrasive grains. The capacity of the discharge pump is selected according to the shape and position of the polishing liquid, the concentration of the polishing liquid, the number of apparatuses and the supply amount, but any polishing liquid of a plurality of polishing apparatuses supplied from the polishing liquid tank by the discharge pump is used. It is characterized in that a polishing liquid circulating supply path is provided which can collect the polishing liquid after polishing and return it to the polishing liquid tank. Furthermore, the capacity and variable range of the discharge amount variable type pump are selected according to the shape and position of the polishing liquid nozzle, the concentration of the polishing liquid, the number of apparatuses and the total supply amount, etc. After polishing, all polishing liquids of the plurality of mirror polishing apparatuses are recovered after polishing, and a polishing liquid circulation supply system having a return path for returning the polishing liquid to the polishing liquid tank is provided, and further supplied to each mirror polishing apparatus. A three-way valve and the like for returning the used polishing liquid directly to the return path when not operating are arranged.

The polishing liquid tank is provided with a supply pipe for the polishing liquid, a return pipe, a supply pipe for abrasive grains and / or a solution, and a drain pipe, and is temporarily measured with a concentration meter such as a hydrometer. Any configuration can be appropriately selected as long as abrasive particles and / or a solution are replenished in accordance with the polishing abrasive particle concentration and the polishing abrasive particle concentration in the polishing liquid tank is maintained at a predetermined concentration.

In the present invention, an object of the present invention is to provide a polishing liquid filter which removes foreign substances and the like and supplies only abrasive grains having a predetermined particle size to each mirror polishing apparatus. By changing the discharge amount by about 30 to 150%, the flow rate can be stabilized. At this time, measure the pressure and / or flow rate in the supply pipe,
The pump may be controlled so as to change to a preset discharge amount according to the measured value.For example, as shown in the embodiment, the pump can be made a variable discharge amount via an inverter, and the variable discharge amount pump Any known configuration can be applied, and the control means may be control by an electric circuit in addition to program control using a computer.

In the present invention, the temperature of the recovered polishing liquid is increased with polishing in the heat exchanger, and the temperature of the raised polishing liquid is adjusted to a predetermined temperature. In the case of a plate fin type heat exchanger, in order to prevent clogging due to abrasive grains, for example, a normal serrate fin is used for the fin, the polishing liquid is vertically flowed down, and the rising cooling water and countercurrent flow are used. In addition to the configuration in which heat exchange is performed, a spiral heat exchanger that brings polishing liquid into contact with thin piping of cooling water and adjusts heat exchange efficiency based on the contact area can be used.

[0014]

According to the present invention , for example, the required number
The polishing liquid is collected and reused in a plurality of mirror-polishing devices that set the mirror-polishing conditions so that extremely high-precision mirror-polishing can be performed on a semiconductor substrate when polishing all of the lots in one lot simultaneously. Provide a circulating supply system that measures the concentration of polishing abrasive grains in a common polishing liquid tank, and replenishes the abrasive grains and / or the solution in accordance with the measured values to maintain the concentration of polishing abrasive grains constant Thereby, it becomes possible to make the polishing rate in a plurality of mirror polishing apparatuses constant, and since the polishing rate between the apparatuses can be made uniform, the dispersion of the mirror surface precision between a large number of substrates polished at the same time is reduced, and high precision is achieved. Highly efficient mirror polishing can be realized.

Further, the present invention provides the circulating supply system, which enables a constant flow rate of the polishing liquid to be always supplied by supplying a variable discharge pump for pressure loss of a filter or the like. For non-operating equipment, the valve is switched to return to the return path to maintain the total supply constant at all times. And a polishing liquid adjusted to a predetermined temperature by a plate fin type heat exchanger is supplied, so that a change in polishing temperature during polishing and clogging of the polishing cloth can be suppressed, and the apparatus Since the polishing rate can be made uniform, the variation in mirror surface accuracy between a large number of substrates polished at the same time is reduced, and highly accurate and highly efficient mirror polishing can be realized.

[0016]

FIG. 1 is a circuit diagram showing a polishing liquid circulating supply system according to the present invention. FIG. 2 is a perspective view showing the configuration 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. As shown in FIG. 2, a mirror-surface polishing apparatus to which the present invention is applied has a plurality of suction chucks 21 rotatably mounted on a work surface plate 20 disposed below, and a polishing cloth surface plate 22 disposed above and a work cloth plate 22 disposed above. The rotation of the work surface plate 20 and the suction chuck 2 are performed on the semiconductor substrate vacuum-adsorbed on the upper surface of the suction chuck 21 by arranging the plate 20 and the plate 20 to face each other with the rotation axis slightly eccentric.
1, the rotation of the polishing pad 22 and the upper and lower plates 20, 22
It is possible to perform the mechanochemical polishing by giving the four rotational actions of the eccentricity of the rotating shaft to obtain a polished surface without processing distortion, and to obtain a polished surface of extremely high quality while improving the polishing efficiency. . Although not shown, the work surface plate 20 having a rotating shaft vertically supported in a base of the polishing apparatus.
The surface plate surface is exposed on the base, and a polishing liquid scattering prevention cover is arranged around the base plate surface. A polishing liquid collecting plate (not shown) is provided between the outer peripheral portion of the work surface plate 20 and the scattering prevention cover. Is provided so that the polishing liquid can be collected.

The polishing solution having a predetermined concentration of the colloidal silica is supplied to the mirror-polishing device 1 _1, 1 _2, ... 1 _n which is pumped by the pump 3 from the polishing liquid tank 2 is disposed a plurality machine shown in FIG. 1 . The supply path will be described in detail. The polishing liquid pressure-fed by the pump 3 is adjusted to a predetermined temperature by the plate-fin type heat exchanger 6 and fed through the filter 7. Thus, the discharge capacity of the pump 3 is detected by the pressure / flow rate sensor 5 and variable by the inverter 4. In addition, each mirror polishing device ₁₁ ,
In 1 ₂ ,... 1 _n , as shown in FIG. 2, the pipe enters through the upper end of the pipe penetratingly arranged in the rotating shaft 23 of the polishing pad 22, and is arranged to face the work table 20 from the center of the polishing pad 22. The nozzle 24 is ejected in the outer peripheral direction. In addition, each mirror-polishing device 1 _1, 1 _2, ... 1 a polishing liquid that is pumped by the device not operating in _n three-way valve 8 _1, 8 _2, ... 8 polishing liquid tank is switched in _n feed into the return passage 9 2 Of course, in the operating apparatus, the polishing liquid collected in the polishing liquid recovery plate returns to the polishing liquid tank 2 from the return path 9 as described above. In addition, a stable flow rate can be ensured regardless of fluctuations in the number of operating units.

In the polishing liquid tank 2, the concentration of the abrasive grains is measured by a concentration measuring device 10 composed of a hydrometer. Here, the concentration is measured at regular intervals, and the abrasive grain supply pipe is measured in accordance with the measured value. The polishing liquid is constantly maintained at a predetermined polishing abrasive concentration by replenishing abrasive grains from the polishing slurry 11 or replenishing the solution from the solution supply pipe 12 as necessary. 2 is configured to replace a predetermined amount of the polishing liquid with a new polishing liquid.

In each of the mirror polishing apparatuses 1 ₁ , 1 ₂ ,... 1 _n , a plurality of suction chucks 21 are arranged on the work surface plate 20, and the semiconductor substrate vacuum-adsorbed on the upper surface of each suction chuck 21 revolves around the work surface 20. The rotation of the suction chuck 21, the rotation of the polishing pad 22, and the eccentricity of the rotating shafts of the upper and lower plates 20, 22 are applied to perform the mechanochemical polishing, and a plurality of semiconductor substrates are formed by one polishing. Polishing can be performed under the same conditions. In addition, since the polishing abrasive grain concentration is measured in the polishing liquid tank, and the abrasive grains and / or the solution are replenished in accordance with the measured value to maintain the polishing abrasive grain concentration constant, each mirror polishing apparatus 11 ₁ , 1 ₂ ,... 1 _n, the polishing rate is kept constant, and the polishing rate does not vary between the apparatuses. Thus, a polishing surface free from processing distortion while improving polishing efficiency can be obtained.

The polishing liquid is supplied by a variable discharge amount type pump so that the polishing liquid can be constantly supplied at a stable flow rate against the pressure loss of the filter and the like. By returning to the return path by switching, the total supply amount of polishing liquid is always kept constant, enabling the supply of polishing liquid at a stable flow rate regardless of the number of operating units, and a plate fin type heat exchanger polishing rate in at because it is providing adjusted polishing liquid to a predetermined temperature, polishing the temperature change and suppress the clogging of the polishing pad during polishing becomes possible, the mirror-polishing device _{1 1, 1 2, ... 1} n The polishing rate is kept constant and the polishing rate does not fluctuate among the apparatuses, so that a polished surface with no processing distortion can be obtained.

[0021]

According to the method for mirror-polishing a semiconductor substrate according to the present invention, a circulating supply system for collecting and reusing a polishing liquid is provided, and the concentration of the polishing abrasive is measured in a common polishing liquid tank. By keeping the concentration constant, it is possible to make the polishing rate of each semiconductor substrate constant in a plurality of mirror polishing apparatuses, thereby stabilizing the productivity and increasing the efficiency, and further, the mechanical action In addition, by making the chemical action constant, it is possible to suppress the change over time of the polishing material, and as a result, it is possible to obtain an extremely high-quality polished surface free from processing distortion and scratches.

In addition, by supplying a pump with a variable discharge rate type to a non-operating device, the valve is switched back to the return path to maintain the total supply amount of the polishing liquid at all times. Suppression of temperature change and clogging of the polishing cloth, and furthermore, it becomes possible to make the polishing rate in a plurality of mirror polishing apparatuses constant, and to make the polishing rate between the apparatuses uniform , for example, 100 or more required number of sheets. Within one lot
As in the case of polishing all of the substrates simultaneously, the dispersion of the mirror surface accuracy between many substrates polished at the same time is reduced, the polishing flatness is stable, the polishing flaw is reduced, the productivity is stable, and the mirror surface with high accuracy and high efficiency Polishing can be realized and the amount of polishing materials can be reduced because of efficient reuse.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a circulating supply system of a polishing liquid to a mirror polishing apparatus for carrying out a mirror polishing method according to the present invention.

FIG. 2 is a perspective explanatory 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;

[Explanation of symbols]

1 ₁ , 1 ₂ ,... 1 _n mirror polishing apparatus 2 polishing liquid tank 3 pump 4 inverter 5 pressure / flow rate sensor 6 plate fin type heat exchanger 7 filter 8 ₁ , 8 ₂ ,... 8 _n three-way valve 9 return path 10 concentration Measuring instrument 11 Abrasive supply pipe 12 Solution supply pipe 20 Work surface plate 21 Suction chuck 22 Polishing cloth surface plate 23 Rotation axis 24 Nozzle

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-66565 (JP, A) JP-A-51-2093 (JP, A) JP-A-5-57612 (JP, A) JP-A-63-1988 306881 (JP, A) JP-A-4-193453 (JP, A) JP-A-4-63660 (JP, A) JP-A-2-257627 (JP, A) JP-A-53-68493 (JP, A) JP-A-2-24059 (JP, A) JP-A-57-182810 (JP, A) JP-A-5-9847 (JP, U) JP-A-56-48461 (JP, U) JP-A 63-17649 (JP, Y2)

Claims (1)

(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. A large number of semiconductor substrates are simultaneously polished using a mirror polisher for semiconductor substrates, in which a plurality of mirror polishers are arranged for polishing by rotating the upper and lower platens relative to each other while supplying the suspended polishing liquid.
In the method for mirror polishing a semiconductor substrate to be polished , a polishing liquid can be supplied from a polishing liquid tank to a plurality of mirror polishing apparatuses by a pump of a variable discharge amount type, and the polishing liquid after polishing is collected and returned to the tank. A circulation supply system for the polishing liquid to be reused is provided so that the polishing liquid to the apparatus can be sent back to the return path when the apparatus is not in operation, and the discharge amount of the pump is measured by a pressure and / or flow rate sensor disposed in the supply path. By changing the polishing liquid circulating supply system to maintain the circulating total supply amount constant at all times, measuring the concentration of polishing abrasive grains in the polishing liquid tank, supplying new abrasive grains and / or a solution, and polishing Grain concentration is kept constant, a heat exchanger is arranged downstream of the pump from the pump and the temperature of the polishing liquid to be fed is kept at a constant temperature, and the polishing rate of each semiconductor substrate in the working mirror polishing apparatus is brought to a predetermined rate. Mirror for semiconductor substrate characterized by maintaining Polishing method.