JP2869300B2 - Semiconductor wafer heat treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer heat treatment apparatus for performing a donor killer heat treatment on a silicon wafer, for example.

[0002]

2. Description of the Related Art As a method for producing a silicon single crystal, a CZ (Czochralski) method for growing a single crystal from dissolved silicon in a quartz crucible is widely used. However, when the silicon single crystal is pulled, the quartz crucible is slightly melted, and oxygen is mixed into the dissolved silicon. Oxygen dissolved in the dissolved silicon enters the crystal as the single crystal silicon grows, and remains as a thermal donor due to the thermal history of the subsequent pulling process. As a result, the grown single crystal is doped with the thermal donor, which makes it difficult to obtain a pure silicon single crystal.

When a silicon wafer doped with a thermal donor is used for manufacturing a semiconductor device, the resistivity of the silicon wafer becomes non-uniform due to the thermal donor, so that the quality of the semiconductor device becomes inconsistent.
That is, the thermal donor negates a small amount of impurities in the acceptor, and makes the silicon wafer N-type. Alternatively, even if the silicon wafer is of the P type, the silicon wafer exhibits a lower resistivity though it is not intended. Therefore, in order to keep the quality of the semiconductor device constant, it is necessary to reduce the number of thermal donors before the manufacturing process of the semiconductor device.

[0004] As one method of this donor erasure, the following heat treatment has been conventionally performed. That is, the grown silicon single crystal rod is sliced into multiple wafers,
Lapping and etching processes are performed by a skilled person. After etching, heat treatment at 500 ° C or higher to reduce thermal donors (donor killer heat treatment)
I do. FIG. 6 shows the relationship between the time required for the heat treatment and the temperature. As can be understood from the straight line A in this figure, the heat treatment time decreases as the temperature of the heat treatment of the silicon wafer increases.

[0005] However, such a conventional donor killer heat treatment process is susceptible to fluctuations in thermal energy. For example, unless the silicon wafer after the heat treatment is rapidly cooled at around 450 ° C., the thermal donors are regenerated rather than reduced.
Such a problem occurs remarkably in a silicon wafer having a large heat capacity such as 8 inches and a large size. Further, when the silicon wafer is heated at about 700 ° C. for a long time, another donor called a new donor due to oxygen is generated. Therefore, accurate temperature control is required for a semiconductor wafer heat treatment apparatus.

In recent years, as the degree of integration of semiconductor integrated circuits has increased, the size of circuit elements has decreased,
Larger silicon wafers are used. A large number of semiconductor devices are formed on a single large silicon wafer, and the quality thereof is required to be uniform. Therefore, when manufacturing semiconductor devices, it is required that large silicon wafers have uniform characteristics. For this purpose, the heat treatment process of the silicon wafer must be precisely controlled. Such heat treatment also needs to be precisely controlled because it is involved in the formation of oxygen precipitation nuclei in intrinsic gettering.

FIG. 7 shows an example of a conventional heat treatment system. The first heat treatment system generally has a wafer loading zone 1, a heating zone 2, and a cooling zone 3. This wafer loading zone 1
, A plurality of silicon wafers 5 are transferred from the cassette 4 onto the horizontal boat 1a. In the heating zone 2, the boat 1a is carried into the tubular horizontal heating furnace 2a, and according to the temperature profile predetermined by the control unit 2b, the silicon wafer 5 in the horizontal heating furnace 2a.
Heat. At this time, the boat 1a is stationary in the horizontal heating furnace 2a.

After the heat treatment, the boat 1a is connected to the horizontal heating furnace 2
a and taken into the cooling zone 3. The cooling zone 3 includes a plurality of cooling fans 3a, and cool air is blown onto the silicon wafers 5 on the boat 1a by the cooling fans 3a. The cool air rapidly cools the silicon wafer 5,
The temperature is reduced at an accelerated rate near ℃. At this time, the boat 1a remains stationary in the cooling zone 3.

FIG. 8 shows another example of the conventional heat treatment system. This second heat treatment system is provided with a vertical heating furnace 6a that is vertically erected. The silicon wafers 7 are loaded from a cassette in a loading section 9 to a vertical boat 9a. Then, the boat 9a is charged from the bottom of the vertical heating furnace 6a on which the boat 9a is erected. The boat 9a is settled in the vertical heating furnace 6a. Then, according to a predetermined temperature profile, the temperature of the vertical heating furnace 6a is controlled by the control unit 6b to perform heat treatment. After the heat treatment, the boat 9a is taken out of the vertical heating furnace 6a, and the silicon wafer 7 is rapidly cooled by the above-described cooling fan 3a. This vertical heating furnace 6a is suitable for heat treatment of a large-sized thing such as an 8-inch silicon wafer.

FIG. 9 shows a third conventional heat treatment system using a rapid heating furnace. This heat treatment system
A heating furnace 10a surrounded by a radiator 10b and a tungsten halogen lamp group 10c are provided. The inlet of the heating furnace 10a is covered with a furnace port flange 10d, and the gas purge nozzle 10e is inserted into the heating furnace 10a. The radiation thermometer 10f measures the temperature in the heating furnace 10a, and the quartz susceptor 10g is disposed in the heating furnace 10a.

The heating furnace 10a is irradiated with infrared rays from the tungsten halogen lamp group 10c to heat the silicon wafer 11 mounted on the quartz susceptor 10g. The heating furnace 10a can be set at a temperature of 500 ° C. to 700 ° C., and has a higher temperature than the heat treatment system described above. Even in this heat treatment system, the silicon wafer 11 is heated in a state where it is left in the heating furnace 10a.

[0012]

The above-described first and second conventional heat treatment systems take a silicon wafer at a temperature of 600.degree.
The heating is performed at 50 ° C. for 30 to 60 minutes. Oxygen donors tend to increase at such relatively low temperatures, but the heat treatment is stable. However, in the first and second conventional heat treatment systems, problems such as poor operability, occurrence of erroneous heat treatment, low productivity, adhesion of undesired dust, and non-uniformity of heat treatment have occurred. Was. Specifically, a plurality of silicon wafers placed on a boat are heated simultaneously in a heating furnace. However, if the boat is not filled with silicon wafers, a dummy wafer needs to be mounted on the boat together with the silicon wafer to be heat-treated in order to make the heat capacity uniform. For this reason, in the first and second conventional heat treatment systems, it is necessary to determine whether or not a dummy wafer is mounted on each boat, which is inferior in operability.

Furthermore, if the heating furnace is long enough to store a plurality of boats, it is possible to mount the plurality of boats and simultaneously heat silicon wafers of the same size. However, if different sizes of silicon wafers are placed on any of the boats, the heat treatment system becomes unsuitable for these silicon wafers. Therefore, as a problem inherent to the first and second conventional heat treatment systems, the fact that there is a high possibility that erroneous heat treatment is performed can be raised as a second problem.

The third problem is caused by batch processing. Since the boat is heat-treated in a stationary state in the heating furnace, when performing heat treatment on a large number of silicon wafers, the operator needs to replace the boat. As a result, the temperature of the heating furnace fluctuated for each treatment,
Temperature adjustment is required for each process. Therefore, the first and second conventional heat treatment systems have a problem of low productivity.

As described above, after heating, the silicon wafer is rapidly cooled by the cooling fan. At this time, the silicon wafer is easily contaminated by minute dust contained in the air. Such fine dusts cause the deterioration of the quality of the silicon wafer and also lead to the problem of defective manufacturing of the semiconductor device.

A fourth problem in the first and second prior arts relates to non-uniform heat treatment. This is because the boat holds the silicon wafer, so that the temperature of the portion where the two are in contact tends to decrease. As a result, the in-plane resistivity of the silicon wafer becomes non-uniform, and a semiconductor device failure occurs.
Thus, the conventional first and second heat treatment systems have various problems.

Further, in the third conventional heat treatment system provided with a rapid heating furnace, since one silicon wafer is mounted on the quartz susceptor, the above first and second prior arts are used. Does not cause a problem. However,
In this heating furnace, there is a problem that productivity is low. Further, when the surface state is different between the silicon wafers, the variation in the thermal reflectance becomes large depending on the surface state in the middle temperature region of 500 ° C. to 700 ° C. If the surface condition of the silicon wafer is not uniform, a non-uniform temperature distribution occurs in one silicon wafer. As a result, the in-plane resistivity of the silicon wafer processed by the third heat treatment system tends to be unevenly distributed.

[0018]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor wafer heat treatment apparatus capable of improving operability, preventing erroneous processing, improving productivity, preventing undesired dust from being mixed, and performing uniform heat treatment. , Its purpose.

[0019]

According to a first aspect of the present invention, there is provided a wafer supply unit for supplying a semiconductor wafer, a heat treatment unit for performing donor killer heat treatment on the supplied semiconductor wafer, and a donor supply heat treatment unit for performing donor killer heat treatment. A semiconductor wafer heat treatment apparatus comprising: a wafer discharge unit that discharges a semiconductor wafer, wherein the heat treatment unit has a transfer path extending from the wafer supply unit to the wafer discharge unit, and via the transfer path. Transfer means for transferring the semiconductor wafers one by one from the wafer supply unit to the wafer discharge unit at a predetermined speed; heating means provided in the middle of the transfer path for heating the semiconductor wafer being transferred by the transfer means; Cooling means for cooling the semiconductor wafer being transferred, provided on the transfer path and downstream of the heating means; A heat treatment apparatus of a semiconductor wafer that includes a quartz heating tube surrounding the transport path, a heater disposed outside the heating tubes.

According to a second aspect of the present invention, there is provided the apparatus for heat treating a semiconductor wafer according to the first aspect, wherein the semiconductor wafer is a silicon wafer.

According to a third aspect of the present invention, the length of the heating means in the direction of the transport path of the portion capable of heating the semiconductor wafer to a constant temperature is lx (mm) and the constant temperature is T (° C.). The transfer speed of the semiconductor wafer by the transfer means is V (mm / sec), and the thickness of the semiconductor wafer is tx
(Μm), and when the constant is a (a = 180 to 200), these are the semiconductor wafer heat treatment apparatuses according to claim 2 satisfying the following expression. V = (0.3T-a) · (lx / 900) · (650 / tx)

According to a fourth aspect of the present invention, when the transfer speed (V) and the heating temperature (T) are represented by a graph arranged on both vertical and horizontal axes of orthogonal coordinates, the first coordinate (PT1) is obtained.
(5 mm / sec, 650 ° C.), second coordinate (PT2) (2
1 mm / sec, 695 ° C.), third coordinate (PT3) (2,
5 mm / sec, 655 ° C.), fourth coordinate (PT4) (8 m
m / sec, 680 ° C.), fifth coordinate (PT5) (13 mm /
Second, 695 ° C.), and the sixth coordinate (PT6) (21 m
m / sec, 710 ° C.), based on the conditions of the transport speed (V) and the heating temperature (T) in the region (R3) surrounded by the approximate straight line connecting the respective coordinates, the transport means transports the semiconductor wafer and 4. The apparatus according to claim 3, wherein the heating means heats the semiconductor wafer.

According to a fifth aspect of the present invention, there is provided a blowing nozzle for blowing an inert gas into the quartz heating tube,
2. The heat treatment apparatus for a semiconductor wafer according to claim 1, further comprising a suction nozzle for discharging the blown inert gas out of the tube.

According to a sixth aspect of the present invention, in the heat treatment apparatus for a semiconductor wafer according to the first aspect, the heating means has a plurality of heating sections, and each of the heating sections has a heating member and a temperature detecting member. is there.

According to a seventh aspect of the present invention, the transfer by the transfer means is controlled, and the heat generation of the heat generating member is independently controlled for each of the plurality of heating sections based on the temperature detected by the temperature detecting member. 7. The heat treatment apparatus for a semiconductor wafer according to claim 6, further comprising control means for performing the control.

[0026]

In the semiconductor wafer heat treatment apparatus according to the present invention, the semiconductor wafer supplied to the wafer supply unit is 1
Each wafer is transferred by a wafer transfer mechanism from the wafer supply unit to the wafer discharge unit via a transfer path. The semiconductor wafer is heated by the heating means in the heat treatment section and then cooled by the cooling means in the middle of the transfer path.

That is, the donor killer heat treatment can be continuously performed for each semiconductor wafer.
Further, the donor killer heat treatment of many semiconductor wafers can be performed under the same conditions.

Further, according to the present invention, since the heating temperature and the transport speed (heating time) are controlled by the control means, the optimum conditions are set so as to preferably satisfy both the erasure of the thermal donor and the oxygen deposition characteristics. be able to. As a result, according to the heat treatment apparatus, it is possible to obtain a silicon wafer having a suitable resistivity distribution in a plane and uniform oxygen precipitation characteristics with high productivity.

Further, according to the present invention, the semiconductor wafers are automatically transferred one by one from the heating means to the cooling means by the transfer means. Therefore, the following effects can be obtained as compared with a conventional heat treatment apparatus that performs heat treatment for each boat on which a plurality of semiconductor wafers are mounted.
That is, it is not necessary to use a dummy semiconductor wafer in order to equalize the heat capacity of each boat. Also,
Since the semiconductor wafers are heat-treated one by one, heat treatment can be easily performed even for semiconductor wafers having different sizes.

Further, according to the present invention, by independently controlling the plurality of heating sections, it is possible to precisely perform a donor killer heat treatment or the like on a semiconductor wafer.

[0031]

1 to 6 are views for explaining a heat treatment apparatus according to one embodiment of the present invention. As shown in FIG. 1, this heat treatment apparatus generally includes a cassette loader 21, a heating zone 22, a cassette unloader 23, and a control unit 24. The heat treatment apparatus is provided in a clean room 25 having a fan 25a and an air purifier 25b. The clean room 25, the fan 25a, and the air purifier 25b form a circulation path of air, and are configured to remove dust, dirt, and the like in the air.

The cassette loader 21 is provided with the turntable 2
1a, robot hand 21b, bridge table 21c
It has. The cassette 26 holding the silicon wafer W is configured to move on the turntable 21a. Each cassette 26 holds a plurality of silicon wafers W in an upright position, and is transported intermittently toward a supply position in front of the bridge table 21c.

The robot hand 21b sequentially takes out the silicon wafers W from the cassette 26 at the supply position and places them on the bridge table 21c. The empty cassette 26 from which all the silicon wafers W have been taken out moves away from the front of the bridge table 21c, and the next cassette 26 moves to this supply position. The empty cassette 26 is removed from the turntable 21a, and the other cassette 2 holding the silicon wafer W is removed.
Replaced with 6.

The heating zone 22 is roughly composed of a transport mechanism 22
a, a heating unit 22b and a cooling unit 22c. The transport mechanism 22 a extends in the heating zone 22 and has an entrance near the cassette loader 21 and an exit leading to the cassette unloader 23. The transport mechanism 22a
The heating unit 22b and the cooling unit 22c arranged in a line communicate with the outlet to the cassette unloader 23. When passing through the heating unit 22b and the cooling unit 22c, each silicon wafer W is cooled after being heated, and the thermal donor is effectively reduced by the heat treatment.

FIGS. 2 and 3 show a part of the transport mechanism 22a in the heating unit 22b. The transport mechanism 22a is constituted by a walking beam transport mechanism, and five stages of walking beams are allocated to the heating unit 22b. Each walking beam section assigned to the heating unit 22b has six walking beams 27a, 27b, 27c, 27d, 27e, 27.
f. These walking beams 27a to 27f are disposed in a quartz tube 28. That is, the walking beams 27a to 27f are accommodated in the quartz tube 28 in parallel with the longitudinal direction. The hollow quartz tube 28 has a substantially rectangular cross section. A silicon wafer W is mounted on the walking beams 27a to 27f provided in the quartz tube 28, and the silicon wafer W is transported to the next walking beam.

Although not shown, a gas nozzle is provided at one end of the quartz tube 28 so that an inert gas (for example, nitrogen gas) flows into the hollow quartz tube 28. As shown in FIG. 3, the nitrogen gas is sucked by a suction nozzle 30 disposed at the other end of the quartz tube 28. Therefore, the heating unit 22
When passing through b, the silicon wafer W is confined in nitrogen gas and does not come into contact with the atmosphere.

The heating unit 22b has a quartz tube 2
Along 8, upper and lower heaters 29 a and 29 b having a predetermined length are provided. These heaters 2
Instead of 9a and 29b, an infrared lamp can be used. The length of the heaters 29a and 29b is 1500 millimeters, and can heat the silicon wafer W at 600 ° C. or higher. The five walking beam sections correspond to the heater blocks 22ba, 22bb, 22bc, 22bd, 22be of the heating unit 22b in FIG.
It corresponds to. Five heater blocks 22ba to 22
be can be controlled independently of each other. In this case, the five heater blocks 22ba to 22be are each set to a predetermined temperature as described later. That is, even if the silicon wafers W are sliced from the same silicon single crystal bar, the silicon wafers W do not have exactly the same quality and characteristics. In this case, according to the optimal temperature profile set for each silicon wafer W, the thermal donor of the silicon wafer W can be effectively reduced.

A test silicon wafer is cut out from the upper (top) and lower (bottom) portions of the columnar silicon single crystal rod, and an optimum temperature profile for heat treatment is found for each silicon wafer by experiment. That is, a thermocouple (not shown) is attached to each test silicon wafer, and its temperature fluctuation is monitored. Further, the resistivity of the silicon wafer after the heat treatment and the deposited oxygen are measured. The thermal energy supplied to the test silicon wafer is, for example, 700 ° C. for 21 seconds, 685 ° C. for 31 seconds, 590 ° C. for 100 seconds,
This corresponds to heating at 5 ° C. for 1440 seconds (24 minutes) (FIG. 6). With this method, a heat treatment simulation is performed on the test silicon wafer. The temperature profile for each silicon wafer cut from the same silicon single crystal rod can be further optimized by using a test silicon wafer, and the transport speed corresponds to this temperature profile. It is determined.

FIG. 4 shows a control range in which the thermal donor and oxygen do not precipitate. A straight line P1 in this drawing indicates a boundary condition for the thermal donor of the silicon wafer W cut out from the bottom of the silicon single crystal rod. According to the conditions shown in the area on the left side of the straight line P1 indicating the relationship between the conveying speed of the quartz tube 28 and the heating temperature, a considerable amount of thermal power is applied to the silicon wafer W cut from the bottom of the silicon single crystal rod. The donor remains, and it is almost impossible to satisfy the specifications of the semiconductor device. On the other hand, in the case of the condition on the right side of the straight line P1 in the figure, the thermal donor in the silicon wafer W cut out from the bottom of the silicon single crystal rod can be sufficiently reduced, and the thermal donor and the like are the standard values of the design standard It becomes below.

The straight line P2 in the figure shows the relationship between the temperature and the transfer speed of the silicon wafer W cut out from the top of the silicon single crystal rod. That is, according to the condition of the region on the left side of the straight line P2, the silicon wafer W cut out from the top portion of the silicon single crystal rod
Contains significant amounts of thermal donors, making it almost impossible to meet the specifications for semiconductor devices.
However, according to the condition of the area on the right side of the straight line P2 in the figure,
The thermal donor in the silicon wafer W can be sufficiently reduced, and the silicon wafer W becomes acceptable.

The curve P3 in the figure represents the boundary condition for the oxygen precipitation characteristic, and is applied to the silicon wafer W cut out from both the top and bottom portions of the silicon single crystal rod. According to the conditions in the region on the right side of the curve P3, excessive oxygen precipitates on the silicon wafer W, and the silicon wafer W becomes unsuitable for manufacturing integrated circuits. On the other hand, according to the conditions in the region on the left side of the curve P3, the amount of precipitated oxygen decreases, and the silicon wafer W becomes suitable for manufacturing a semiconductor integrated circuit.

As a result, as long as the conditions represented by the region R3 surrounded by the lines P2 and P3 are satisfied, regardless of the position of the silicon single crystal rod, the silicon wafer W is designed in consideration of the controllability of the resistivity. It satisfies the standard. The region R3 is approximately represented by first, second, and third approximate straight lines, and the first approximate straight line is composed of a first coordinate PT1 (5 mm / sec, 650 ° C.) and a second coordinate PT2 (21
Millimeters per second, 695 ° C.). Second
Is approximated by the third coordinate PT3 (2.5 mm /
Second, 655 ° C.), the fourth coordinate PT4 (8 mm /
Second, 680 ° C.). The third approximate straight line is a fifth coordinate PT5 (13 mm / sec, 695 ° C.),
Sixth coordinate PT5 (21 mm / sec, 710 ° C.)
Is determined by

Region R2 surrounded by lines P1 and P2
Is applied only to the silicon wafer W cut out from the top of the silicon single crystal rod. The region R1 cannot be applied to all silicon wafers. The silicon wafer W cut out from the top portion of the silicon single crystal rod requires high temperature and long time heating, and the more the transport speed is slow over a relatively wide temperature range, the more oxygen is precipitated in the silicon wafer W. . These tendencies are observed irrespective of whether the silicon wafer W is P-type or N-type. Curve P3 shows applicable conditions irrespective of the position of the silicon single crystal rod, but the decrease in the amount of precipitated oxygen was caused by heating the silicon wafer cut from the bottom of the silicon single crystal at a high temperature. Appears prominently in cases. Furthermore, this oxygen is likely to precipitate at the center of the surface of the silicon wafer.

In the heat treatment, not only the thermal donor and the amount of precipitated oxygen, but also BMD (bulk mi
It also has an effect on cro defect). FIG. 5 shows that the oxygen concentration is low (1.1 to 1.3 × 10 ¹⁷ atoms / c).
m ³ ) shows the relationship between the amount of BMD for the crystal, the temperature of the quartz tube 28, and the transfer speed of the silicon wafer. A thin solid line, a broken line, and a thick solid line indicate that the transport speed is 14 mm / sec, 20 mm / sec, and 2 mm, respectively.
4 mm / sec. The BMD of a silicon wafer having a low oxygen concentration is reduced as far as a silicon wafer subjected to a high-temperature heat treatment is concerned.
This means that the conveying speed and heating of the quartz tube 28,
It is taken into account when controlling the temperature for cooling.

Information on the optimum transport speed and temperature is stored in the data storage unit of the control unit 24 constituted by a computer system. The control unit 24 according to this information
Controls each walking beam section. Each of the plurality of thermometers 31 has a heater block 22ba-2ba.
2be, and the temperature of each heater block is indicated by a thermometer 3
1 is measured. The temperature information of each heater block is sent to the control unit 24, and the heaters 29a and 29b are controlled according to the temperature profile stored in the data storage unit. Since the heat capacity of the heating unit 22b is much larger than that of the silicon wafer W, the heating capacity is 3 inches to 8 inches.
Heat treatment under almost the same conditions is possible up to a silicon wafer with a large diameter up to inches.

The five walking beam sections are provided corresponding to the cooling unit 22c, and each walking beam section is constituted by six quartz walking beams. When the heat-treated silicon wafer W reaches the outlet of the transfer mechanism 22a, the silicon wafer W is sequentially supplied from the heating unit 22b to the cooling unit 22c. The silicon wafer W proceeds in the tunnel of the cooling unit 22c and is exposed to a cooling gas. The cooling gas is supplied by a circulation system or a non-circulation system. Although not shown, a thermometer is provided in the cooling unit 22c to control the temperature in the tunnel by the control unit 24.
Is input. The control unit 24 controls the amount of gas blown to the silicon wafer W and the walking beam section, and controls the silicon wafer W
The silicon wafer W is rapidly cooled at around 450 ° C. in order to prevent a thermal donor from being generated.

The cassette unloader 23 is provided with a turntable 23a, a robot hand 23b, and a bridge table 23c. The empty cassette 32 patrols over the turntable 23a and the bridge table 23
c reaches the front position. Silicon wafer W
Are sequentially transferred to the cooling unit 22c, and the robot hand 2
3b inserts the silicon wafer W into the empty wafer cassette 32 at the unloading position. When a predetermined number of silicon wafers are mounted on the cassette 32, the cassette 32 moves intermittently.

As a result, the cassette 32 filled with the silicon wafer W leaves the unloading position, and a newly empty cassette 32 reaches the unloading position. As described later, the cassette 26 holding the silicon wafer Wx moves to the loading position, and the robot hand 21b supplies the silicon wafer Wx from the wafer cassette 26 to the transfer mechanism 22a via the bridge table 21c.

The silicon wafer Wx is sent to the walking beam section and passes at a speed of 20 mm / sec through the quartz tube 28 provided with the heaters 29a and 29b. For example, the final heater block 22be is 6
The temperature is adjusted to 85 ° C., and the silicon wafer Wx passes through the final heater block 22be in 15 seconds. Also,
Assuming that the thickness of the silicon wafer W is 625 μm,
The transport speed V is as follows. That is, V = (0.
3T-a) · (lx / 900) · (650 / tx) =
9.5 to 44.3 mm / sec.

Here, T is 685 ° C., Lx is 1500 mm, and a is 180 to 200. The constant a is determined in advance based on the silicon wafer Wx cut out from the top of the silicon single crystal rod. what if,
When the silicon wafer Wx is cut from the top of the silicon single crystal rod, the range of the constant a is 18
From 7 to 193, the silicon wafer Wx is heated for a relatively long time. This is because it is difficult to remove the thermal donor at the top of the silicon single crystal rod. Therefore, the transport mechanism 22a is 21.7.
The speed is controlled to ３32.1 mm / sec, and the thermal donor in the silicon wafer Wx is removed.

The silicon wafer Wx is supplied to the heating unit 2
From 2b, it goes to the cooling unit 22c and is continuously transported by the walking beam section. While the silicon wafer Wx passes through the cooling unit 22c, the silicon wafer Wx is rapidly cooled so that thermal donors do not regenerate, and the temperature of the silicon wafer Wx reaches 60 ° C. at the outlet of the transfer mechanism 22a. Since the thermal donor tends to increase at about 450 ° C., the silicon wafer Wx needs to be cooled rapidly around 450 ° C.
It may be slightly lower than ° C. For example, even if the temperature of the silicon wafer Wx is 440 ° C., there is no problem in the heat treatment process.

When the silicon wafer Wx reaches the exit of the transport mechanism 22a, the silicon wafer Wx proceeds to the bridge table 23c, and the robot hand 23b inserts the same into the empty cassette 32. When the cassette 32 is filled with the silicon wafer, the cassette 32 separates from the turntable 23a and stops at a predetermined position.

Therefore, according to the heat treatment apparatus for a semiconductor wafer according to the present embodiment, any dummy silicon wafer is not required, so that complicated operations can be avoided. A predetermined number of silicon wafers W are taken out of the cassette and transferred to an empty cassette. This means that all silicon wafers have the same size. Further, the quartz tube 28
Since many silicon wafers are simultaneously heated at a high temperature, heat treatment can be efficiently performed. Further, since the heat treatment system according to the present embodiment is provided in a clean room, it is possible to prevent dust and the like from being mixed and adhered to the silicon wafer. In addition, while the silicon wafer W is being conveyed by the walking beam system, high-temperature air is blown over the entire surface thereof. As a result, a uniform heat treatment can be performed on the entire silicon wafer.

That is, it has both advantages of stability in heat treatment of a batch type heat treatment furnace and operability of a rapid heating furnace, regardless of the number of lots, and only replacement of a cassette for semiconductor wafers of different diameters. And a flexible donor killer heat treatment of the semiconductor wafer and the reliability thereof can be improved. In addition, a uniform heat treatment can be performed on the entire surface of the semiconductor wafer, the resistivity of the entire surface of the wafer can be accurately evaluated, and a wafer having oxygen precipitation characteristics suitable for device manufacturing conditions can be manufactured. it can.

It should be noted that modifications may be made to the above-described embodiment without departing from the spirit of the present invention. For example, the semiconductor wafer heat treatment apparatus according to the present embodiment can be applied to each wafer of a germanium semiconductor, a compound semiconductor, and the like. Further, the robot hand may be configured by using a means utilizing a suction force.
Further, the heat treatment apparatus for a semiconductor wafer according to the present embodiment may be applied to natural intrinsic gettering and annealing after ion implantation. In addition, a plurality of quartz rollers may be provided every 20 to 30 millimeters instead of the walking beam to convey the silicon wafer at a predetermined speed.

If this heating means is constituted by, for example, a heat treatment furnace, and this heat treatment furnace has a considerable heat capacity and is maintained at a constant temperature, semiconductor wafers are loaded one by one into this. This semiconductor wafer is uniformly heated at a constant speed during the transfer process. Further, if the cooling means is constituted by, for example, a cooling furnace having a fixed size, the wafer is similarly cooled at a fixed speed. As a result, the stability of the heat treatment can be dramatically improved. In addition, each of the wafer supply section and the wafer discharge section is described in
No. 59906, a cassette loader is provided,
When a semiconductor wafer is moved into and out of the heat treatment furnace from the cassette loader and from the cooling furnace to the cassette loader by the robot, the semiconductor wafer can be accommodated in the same cassette before and after the heat treatment. Identification becomes easy.

Further, as shown in FIG. 6, for example, the time required for the donor killer heat treatment is 24 minutes at 565 ° C., and 5 minutes.
It takes 100 seconds at 90 ° C., 31 seconds at 685 ° C., and 21 seconds at 700 ° C. Further, the time required to maintain the temperature at 685 ° C. can be further shortened since the donor disappearance is performed before the temperature is reached. When rapid heating is performed in this manner, there is no risk of contamination of the silicon wafer.

[0058]

Therefore, in the semiconductor wafer heat treatment apparatus according to the present invention, the following effects can be obtained.

(1) According to the present invention, semiconductor wafers are automatically transferred one by one from a heating unit to a cooling unit by a transfer mechanism. Therefore, the following effects can be obtained as compared with the conventional heat treatment apparatus that performs the donor killer heat treatment for each boat having a plurality of semiconductor wafers. There is no need to use dummy semiconductor wafers to equalize the heat capacity of each boat. Since the donor killer heat treatment is performed for each semiconductor wafer, the donor killer heat treatment can be easily performed even for semiconductor wafers having different sizes. Since the donor wafer is subjected to the donor killer heat treatment for each semiconductor wafer, the temperature fluctuation of the heating furnace can be reduced as compared with the case where the heat treatment is performed for each boat on which a plurality of semiconductor wafers are mounted. Compared to the case of the batch processing, the donor killer heat treatment can be performed continuously and automatically for each semiconductor wafer, so that the productivity can be improved. Since the semiconductor wafer is exposed without being stored in the boat, a uniform donor killer heat treatment can be performed over the entire surface of the semiconductor wafer. (2) According to the heat treatment apparatus for a semiconductor wafer according to the present invention, the optimal temperature control can be automatically performed by the control unit, so that a uniform donor killer heat treatment can be performed while suppressing temperature variations. (3) Since the semiconductor wafer heat treatment apparatus according to the present invention can perform rapid heating, the donor killer heat treatment can be completed in a short time. Further, since this heat treatment apparatus is provided in a clean room, dust and the like can be prevented from adhering to the wafer.

That is, according to the semiconductor wafer heat treatment apparatus of the present invention, operability can be improved. Also, incorrect donor killer heat treatment can be prevented. Further, the productivity can be improved. Also,
Adhesion of dust to the semiconductor wafer can be prevented. Further, a uniform donor killer heat treatment can be performed on the entire surface of the wafer.

[Brief description of the drawings]

FIG. 1 is a front view showing a heat treatment apparatus for a semiconductor wafer according to one embodiment of the present invention.

FIG. 2 is a perspective view showing a part of a heating furnace of the semiconductor wafer heat treatment apparatus according to one embodiment of the present invention.

FIG. 3 is a sectional view showing a heating furnace of the semiconductor wafer heat treatment apparatus according to one embodiment of the present invention.

FIG. 4 is a graph showing a range of a furnace temperature / transport speed satisfying oxygen precipitation characteristics and donor elimination by a heat treatment apparatus according to one embodiment of the present invention.

FIG. 5 is a graph showing a generation state of BMD in an oxygen precipitation treatment by a heat treatment apparatus according to one embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a donor disappearance time and a holding temperature in a donor killer heat treatment according to the present invention.

FIG. 7 is a perspective view schematically showing a heat treatment step of a semiconductor wafer using a conventional horizontal furnace.

FIG. 8 is a perspective view schematically showing a heat treatment step of a semiconductor wafer using a conventional vertical furnace.

FIG. 9 is a sectional view schematically showing a conventional heat treatment apparatus.

[Explanation of symbols]

 21 cassette loader 22 heating zone 22c cooling unit 23 cassette unloader 24 control unit W silicon wafer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/324 H01L 21/26

Claims (7)

(57) [Claims] 1. A semiconductor device comprising: a wafer supply unit that supplies a semiconductor wafer; a heat treatment unit that performs a donor killer heat treatment on the supplied semiconductor wafer; and a wafer discharge unit that discharges the semiconductor wafer that has been subjected to the donor killer heat treatment. A heat treatment unit for a semiconductor wafer, wherein the heat treatment unit has a transfer path extending from the wafer supply unit to the wafer discharge unit, and through the transfer path, one semiconductor wafer at a time from the wafer supply unit to the wafer discharge unit. Transport means for transporting the semiconductor wafer at a predetermined speed, heating means provided in the middle of the transport path for heating the semiconductor wafer being transported by the transport means, and provided on the transport path downstream of the heating means. , and a cooling means for cooling the semiconductor wafer during transport, on
The heating means is a quartz heating tube surrounding the transport path.
And a heater located outside the heating tube.
Heat treatment apparatus of the non-semiconductor wafer. 2. The apparatus according to claim 1, wherein the semiconductor wafer is a silicon wafer. 3. The length of the heating means in the direction of the transport path of a portion capable of heating the semiconductor wafer to a constant temperature is l.
x (mm), the constant temperature T (° C.), the transfer speed of the semiconductor wafer by the transfer means is V (mm / sec), the thickness of the semiconductor wafer is tx (μm), and the constant a (a = 18)
3. The heat treatment apparatus for a semiconductor wafer according to claim 2, wherein, when 0 to 200), these satisfy the following expression. V = (0.3T-a) · (lx / 900) · (650 / tx) 4. The transfer speed (V) and the heating temperature.
When (T) is represented by a graph arranged on both the vertical and horizontal axes of the rectangular coordinates, the first coordinate (PT1) (5 mm / sec, 650 ° C.)
A second coordinate (PT2) (21 mm / sec, 695 ° C.), a third coordinate (PT3) (2.5 mm / sec, 655 ° C.), a fourth coordinate (PT4) (8 mm / sec, 680 ° C.), The transport speed in a region (R3) surrounded by an approximate straight line connecting the fifth coordinate (PT5) (13 mm / sec, 695 ° C.) and the sixth coordinate (PT6) (21 mm / sec, 710 ° C.) (V) and heating temperature (T),
The transport means transports the semiconductor wafer,
Claims the heating means for heating the semiconductor wafer 3
A heat treatment apparatus for a semiconductor wafer as described in the above . 5. An inert gas in the quartz heating tube.
Nozzle and the inert gas blown
And a suction nozzle for discharging air out of the tube.
The apparatus for heat treating a semiconductor wafer according to claim 1 . 6. The semiconductor wafer heat treatment apparatus according to claim 1, wherein said heating means has a plurality of heating sections, and each of said heating sections has a heating member and a temperature detection member. 7. The semiconductor wafer heat treatment apparatus according to claim 6, further comprising control means for controlling conveyance by said conveyance means and independently controlling heat generation of said temperature detecting member for each of said plurality of heating units.