JP3474238B2 - Heat treatment equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat treatment apparatus .

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, there is a step of obtaining a thin film in which a doping component is diffused. Such a process is performed by a heat treatment device called a diffusion furnace,
Solid sources, liquid sources, gas sources, etc. are used according to the difference in the diffusion source of impurities. For example, a liquid diffusion source of phosphorus oxychloride (POCl3) is used when phosphorus is diffused in a high concentration in a silicon film, and this process is performed as follows when a vertical furnace is used.

That is, a large number of wafers are placed in a wafer boat made of quartz at intervals with a shelf shape, and the wafer boat is loaded into a reaction tube made of quartz by a loading / unloading mechanism. Then, in the reaction tube, for example, 900 to 1200
The atmosphere is heated to ℃ and phosphorus oxychloride (POC
l3) The solution is bubbled with nitrogen (N2) gas, and a processing gas mixed with oxygen gas is supplied into the reaction tube to thermally diffuse phosphorus in the silicon film on the wafer, and then the reaction tube is filled with an inert gas. It is replaced and the wafer boat is unloaded.

[0004]

By the way, when the above-mentioned phosphorus diffusion process is carried out, there is a problem that a considerable amount of particles are generated when the wafer is unloaded (when the wafer boat is carried out from the reaction tube after the heat treatment). . This particle has been confirmed by a particle counter,
It is said to be a reaction product containing phosphorus, but the substance of this reaction product is unknown. However, if no measures are taken, the substance containing phosphorus scatters in the clean room, causing contamination of the wafer and adversely affecting the human body. In addition to loading and unloading the wafer boat, which is called a loading chamber below the reaction tube, Metal corrosion is also a concern in the area where wafers are transferred to the wafer boat.

Therefore, for example, a system is used in which a loading chamber is partitioned and exhausted locally. However, since not all the particles described above can be exhausted, the amount of particles is reduced as compared with the case where exhaust is not performed, but exhaust is performed. The same problem still remains because the unretained residue scatters in the clean room. Since the pattern width of the device has become finer and the allowable amount of particles has become more severe, measures against particle scattering due to the phosphorus diffusion process are required, but a definitive solution has been found. The current situation is not.

The present invention has been made under such circumstances, and an object thereof is to reduce generation of particles in a heat treatment process using phosphorus.
To provide a heat treatment apparatus .

[0007]

The invention according to claim 1 is a vertical type
Reaction tube and the lid that opens and closes the opening of this reaction tube.
A holder mounted on the lid of the device via a heat insulating member,
, A large number of objects to be processed are held vertically by a holder and carried into the reaction tube through an opening and the opening is closed by a lid, and a processing gas containing phosphorus and oxygen is heated in the reaction tube under a heating atmosphere. In the apparatus for supplying and performing heat treatment, the lid portion
To measure the temperature of the lid and the heating means provided in the
For detecting the temperature and the value detected by the temperature detecting means.
Exposed in the reaction tube in the lid during heat treatment.
The sublimation point of phosphorus pentoxide is below the
Control unit that controls the heating means to heat to the temperature above
And are provided.

According to a second aspect of the present invention, a large number of objects to be processed are held by a holder and carried into the reaction tube through an opening, and the opening is closed by a lid, so that phosphorus and oxygen are introduced into the reaction tube under a heating atmosphere. An apparatus for performing a heat treatment by supplying a processing gas including and includes a cooling unit for cooling the lid after the heat treatment.

[0009]

According to the experiments conducted by the present inventor, for example, when phosphorus oxychloride (POCl3) and oxygen are introduced into the reaction tube, they react with each other to form P2 O5 and precipitate as a solid. It was found that when carried out, it reacts with moisture in the atmosphere to generate phosphoric acid, and this phosphoric acid becomes a mist and scatters. Therefore, the portion exposed to the atmosphere of the reaction tube during the heat treatment can be prevented from generating mist by preventing the temperature at which P2 O5 is precipitated as a solid, that is, the sublimation point of P2 O5 from being not higher than 360 ° C. as in, located away from the heating unit, the inner surface of at least the lid more to the above stated temperature, lid
By providing a heating means in the part , the generation of particles can be significantly reduced.

Even if the temperature of the lid is 360 ° C. or higher, the amount of P 2 O 5 deposited on the lid is reduced by providing the exhaust port at a position distant from the lid, so that the generation of particles can be suppressed. . In addition to such means, it is precipitated as P2 O5 solid to the lid, if cooling the lid to cool to a temperature below that does not scatter becomes mist during unloading of the object to be processed, also Generation of particles can be suppressed.

[0011]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows a vertical heat treatment apparatus for carrying out phosphorus diffusion according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a cylindrically formed quartz glass whose axial direction is vertical. Is a reaction tube constituting a vertical heat treatment section. At the lower end of the reaction tube 1, a lid 2 is detachably provided via an O-ring 11 so as to keep the inside of the container airtight.

In the reaction tube 1, a heat insulating tube 4 is provided on the lid portion 2 via a rotary shaft 51, and on the heat insulating tube 4, a heat resistant material such as quartz is held. A wafer boat 3, which is a tool, is placed, and a plurality of, for example, 150 objects to be processed, such as semiconductor wafers W, are accommodated in the wafer boat 3 at predetermined intervals.

As shown in the enlarged view of FIG. 2, the lid portion 2 has a heating means 21 for heating the lid portion 2 therein, for example, a resistance heating element, and a temperature of the lid portion 2 is measured. For this purpose, a temperature detecting means 22 including, for example, a thermocouple is provided, and these are electrically connected to the control section 23.

A rotating mechanism 5 connected to the rotating shaft 51 for rotating the wafer boat 3 is provided under the lid portion 2.
2 and a boat elevator for moving the wafer boat 3 in the vertical direction.

On the lower side wall of the reaction tube 1, there is integrally formed a projecting tubular portion 6a which projects outward from the container wall, and a thin tubular injector 6 made of quartz glass is inserted into the projecting tubular portion 6a. There is. One end side of the injector 6 (inner end side of the reaction tube 1) is bent in an L shape and extends vertically to a little above the upper end of the wafer boat 3 and further U there.
It bends in a letter shape and extends straight to the vicinity of the lower end of the wafer boat 3, and a large number of gas ejection holes (not shown) are provided at predetermined intervals in the vertical direction in the pipe line portion extending downward. Further, it is formed at a position corresponding to the installation position of each wafer W. That is, the injector 6 injects gas in the direction along the wafer process surface.

At the other end of the injector 6, a first gas introducing pipe 7a and a second gas introducing pipe 7b for introducing a carrier gas such as nitrogen (N2) gas and oxygen (O2) gas, respectively, Third gas introducing pipes 7c for introducing phosphorus oxychloride (POCl3) are branched and connected, respectively, and POCl3 is stored in a liquid state in a container 7d, and N2 gas is passed through this. As a result, it becomes steam and is introduced into the third gas introducing pipe 7c together with the N2 gas.

Around the reaction tube 1 is usually 700 to 12
A heater 10 such as a resistance heater is provided to heat the container to about 00 ° C. to perform phosphorus diffusion, and an exhaust pipe 12 is provided below the reaction tube 1.
The processing gas introduced into the reaction tube 1 is exhausted from the position 2.

Next, the operation of the above embodiment will be described.
First, the region to be treated in the reaction tube 1 is brought into a uniform heating state of, for example, 900 ° C. by the heater 10. Then for example 150
A wafer boat 3 loaded with a number of semiconductor wafers W is loaded into the reaction tube 1 by the boat elevator 53, and the lid 2 is heated by the heating means 21 at a temperature at which phosphorus pentoxide (P2 O5) does not precipitate, for example, at the sublimation point of P2 O5. It is heated to a certain temperature of 360 ° C or higher. Here, the temperature detecting means 22 detects the temperature of the lid portion 2, guides the detected temperature to the control portion 23, and controls the heating means 21 by the control portion 23 so that the temperature of the lid portion 2 becomes a preset temperature. Then, after the inside of the reaction tube 1 is evacuated to a predetermined vacuum degree, N2 gas is supplied from the first gas introduction pipe 7a at a flow rate of, for example, 10 SLM, and the second gas introduction pipe 7
O2 gas from b is introduced into the injector 6 at a flow rate of, for example, 1 SLM, and N2 gas is passed through the container 7d at a flow rate of, for example, 1 SLM to produce a doping gas mixture containing the vapor of POCl3 in the N2 gas as the third gas. By supplying POCl3 to the injector 6 at a rate of, for example, 300 mg / min by supplying it to the introduction pipe 7c, the processing gas containing N2 gas and O2 gas, which are carrier gases, and the mixed gas for doping is injected into the injection hole of the injector 6. Is supplied to, for example, a polysilicon layer of each semiconductor wafer W, and phosphorus is diffused in the polysilicon layer. After that, for example, the semiconductor wafer W is annealed while the region to be processed is kept in a uniform heating state of 900 ° C., for example.

Next, the circumstances that led to the adoption of the structure of the above-described embodiment will be described. That is, the present inventor conducted various experiments as described below, and when phosphorus diffusion was performed using POCl3, it was found that the main source of particles at the time of unloading the wafer was the lid, and For the mechanism of occurrence, see P
OCl3 and oxygen react with each other to produce P2 O5.
At a point below the sublimation point of 2 O5, P2 O5 precipitates as a solid, and when the wafer is unloaded, this P2 O5 reacts with moisture in the atmosphere to become H3 PO4, which becomes a mist before H3 PO4 cools below its boiling point. It came to the conclusion that it would be scattered.

Therefore, as described above, the lid is provided with the heating means, and the lid is kept at 360 ° C. while the processing gas is being supplied.
When heated to the above temperature, the precipitation of P2 O5 in the lid does not occur theoretically, and therefore, even if it actually occurs, the amount of precipitation is considered to be extremely small. Even if there is a point where the temperature is lower than 360 ° C because it is far from the heater near the lower end of the heat insulating cylinder, the area is very small as can be seen from the experimental results described later, and as a result, the mist of H3PO4 is reduced. Since the source is extremely small, the generation of particles during unloading can be suppressed as much as possible.

Next, a description will be given of a test conducted to clarify the generation source and generation mechanism of particles when the wafer is unloaded. First, in order to understand the phenomenon of particle generation, the relationship between the amount of phosphorus mist generated, the unload temperature, and the number of treatments was investigated.

That is, the furnace temperature is 900 ° C. and the N 2 gas flow rate is 1
8 SLM, O2 gas flow rate 500 SCCM, POCl3 flow rate 200 mg / min, diffusion time under the conditions of treatment time of 30 minutes and unloading at a speed of 100 mm / min, the unloading temperature is 900 ° C.,
The amount of phosphorus mist generated when the temperature was set to 800 ° C and 700 ° C was measured. As shown in FIG. 3, the measurement is performed on the wafer boat 3
Also, a tubular body 81 is arranged around the outer periphery of the heat retaining tube 4 to collect phosphorus mist, and the amount of mist is counted for 1 minute by a laser particle counter 82 connected to several points of the tubular body, and this is taken for 15 seconds. The measurement was performed 15 times at intervals (hereinafter, this measurement method is referred to as a multipoint monitoring system).

The relationship between the time in the reaction tube and the temperature at this time is shown in FIG. 4, in which the loading step, the heating step, the temperature stabilizing step, the phosphorus diffusion step, the annealing step, and The temperature lowering step indicates the step of measuring the amount of phosphorus mist generated. Also, the diffusion process was performed three times with the wafers exchanged, and the fourth diffusion condition was set to 18 N2 gas only.
The flow rate of the SLM was changed (hereinafter referred to as N2 sequence), and the amount of phosphorus mist generated in each case was measured. The result is shown in FIG.

From these results, it was confirmed that the amount of phosphorus mist generated increased as the number of treatments was repeated, and that the lower the unload temperature, the smaller the amount. Further, since the diffusion process was performed by exchanging the wafer and the amount of phosphorus mist generated increased in proportion to the number of times of processing, it is presumed that the source of phosphorus mist is not the wafer.

Next, in order to reconfirm the above-mentioned result, N2 sequence treatment was continuously carried out while changing the unloading temperature, and the change in the amount of phosphorus mist generated was investigated. The relationship between time and temperature in the reaction tube at this time is shown in FIG. In the figure, a diffusion processing step performed on a non-wafer, an unloading step, a wafer diffusion processing step, and N 2
Sequence step is a step for measuring the amount of phosphorus mist at an unloading temperature of 900 ° C. is a step for measuring an amount of phosphorus mist at an unloading temperature of 800 ° C. is a step for measuring a phosphorus mist amount at an unloading temperature of 700 ° C. is an unloading temperature of 90 again.
The process of measuring the amount of phosphorus mist when the temperature is 0 ° C. is shown. The measurement was performed by a multipoint monitoring system. This result is shown in FIG. 7. From this, it was confirmed that the amount of phosphorus mist generated depends on the unloading temperature, as in the case of the above-described experimental result.

Next, the following experiment was conducted to confirm the source of phosphorus mist. That is, after performing the diffusion treatment three times under the conditions of the furnace temperature of 900 ° C. and the treatment time of 30 minutes, the quartz parts including the wafer boat, the heat insulating cylinder, and the lid are cleaned for each part according to the flowchart shown in FIG. It was replaced or replaced with a cleaned part (cleaned product), and after N2 sequence treatment, the amount of phosphorus mist generated was measured by a multipoint monitoring system. The unloading temperature was set to 900 ° C., which is a large amount, in order to confirm the increasing / decreasing tendency of the amount of phosphorus mist generated. In the flow chart, the contaminated product is a component that has been used for diffusion processing and has not been cleaned. The result is shown in FIG. From these results, it was confirmed that the source of phosphorus mist was the lid, because the amount of phosphorus mist generated when the lid was replaced with a washed product was extremely small. The above experimental results, that is, the amount of phosphorus mist generation depends on the temperature, from the result that the source of phosphorus mist is the lid, the present inventors presume that the generation of phosphorus mist is related to the temperature in the reaction tube, The mechanism of phosphorus mist generation was assumed as follows. POCl3 and O in the reaction tube
2 reacts with each other to form P2 O5 as shown in the following formula. 4POCl3 + 3O2 → 2P2 O5 + 6Cl2 (1) Since the sublimation point of P2O5 is 360 ° C, it precipitates as a solid at a place below 360 ° C in the reaction tube, that is, at the lid. P2 O5 (g) → P2 O5 (s) (2) P2 O5 reacts with moisture in the atmosphere during unloading to produce orthophosphoric acid (H3 PO4). P2 O5 + 3H2 O → 2H3 PO4 (3) Since the boiling point of H3 PO4 is 261 ° C., when the temperature of the lid is lowered to 261 ° C., nuclear condensation occurs and the mist scatters. H3 PO4 (g) → H3 PO4 (l) (4) In order to support this mechanism, as shown in FIG. 10, the temperatures of the top portion A, the center portion B, the bottom portion C, and the lid portion D of the heat retaining cylinder are shown. The furnace temperature is 700 ° C, 800 ° C, 900
The measurement was performed when the diffusion treatment was performed at 1000C and 1000C. The results are shown in Fig. 11. In the figure, ○ is the furnace temperature 700
C, Δ indicates 800 ° C., □ indicates 900 ° C., and ● indicates 1000 ° C.

From this result, when the diffusion treatment was carried out at the furnace temperature of 900 ° C., only the measurement point D, that is, the lid portion was P2 O.
It was confirmed to be within the range below the sublimation point of 5 and above the boiling point of H3 PO4, confirming the justification of the above-mentioned mechanism of phosphorus mist generation.

From the above-mentioned experiment, phosphorus mist is the P in the reaction tube.
It was confirmed that it was generated from the place below the sublimation point of 2 O5, that is, from the lid. Next, Fig. 4 shows the relationship between the temperature stabilization time and the amount of phosphorus mist generated when diffusion treatment is performed at a furnace temperature of 900 ° C. It was confirmed by measuring the temperature change of the lid portion with respect to the temperature stabilization time () after the temperature raising step () shown and measuring the amount of phosphorus mist generation with respect to the temperature stabilization time.

FIG. 12 is a diagram showing the relationship between the temperature stabilization time and the lid temperature, and FIG. 13 is a diagram showing the relationship between the temperature stabilization time and the amount of phosphorus mist generation. From this result, in the temperature stabilization time of 15 minutes set by the conventional diffusion process, the diffusion process started at the temperature of the lid portion around 300 ° C., and the amount of phosphorus mist generated was large during this temperature stabilization time. It was confirmed that it was necessary to stabilize the temperature for about 50 minutes to reduce the amount of phosphorus mist generated. In addition, P2 O5 on the lid
Even if the temperature of the lid part after adsorbing is heated to 360 ° C or higher, P
No release of 2 O5 was observed, and it was confirmed that the time difference from the diffusion treatment to 360 ° C. affects the amount of P2 O5 adsorbed and determines the amount of phosphorus mist generation.

Next, the change in the amount of phosphorus mist generated when the temperature in the furnace during the diffusion process was changed was also measured.
Here, the temperature stabilization time was set to 50 minutes, and the amount of phosphorus mist generation was measured after the diffusion treatment was performed three times in succession. FIG. 14 shows the relationship between the furnace temperature and the lid temperature, and FIG. 15 shows the relationship between the furnace temperature and the phosphorus mist generation amount. Figure 1
In Table 4, Δ indicates the case of temperature stabilization time of 50 minutes, and ○ indicates the case of 80 minutes. From this result, when the temperature stabilization time is 50 minutes, the temperature of the lid becomes 360 ° C or higher, the furnace temperature is 890 ° C or higher, and when the furnace temperature is 880 ° C, the amount of phosphorus mist generated increases to 890 ° C. Was confirmed to be extremely decreased, and it was confirmed that the amount of phosphorus mist generation was suppressed when the temperature of the lid portion was 360 ° C. or higher.

Finally, when the conventional diffusion treatment condition, that is, the temperature stabilization time is set to 15 minutes, and the diffusion treatment is performed at a lid temperature of 360 ° C. or lower (A), the temperature stabilization time is set to 50 minutes and the lid portion temperature is set to 50 minutes. When the diffusion treatment was performed at a temperature of 360 ° C. or higher (B), the atmosphere in the reaction tube at the time of unloading was collected in an impinger and dissolved in pure water, and the ions contained in each atmosphere were analyzed by ion chromatography. Was analyzed.

This result is shown in FIG.
PO4 seen near tention Time 15 minutes
It was confirmed that the 3-peak was not seen in B, and the PO4 3-content was 121.23 ng in A, while it was 7.060 ng in B, which was extremely small.

Based on the above-mentioned experimental process, the present inventors have elucidated the mechanism of phosphorus mist generation and established P2O5 in the reaction tube.
The structure of the above-described embodiment was adopted, paying attention to the fact that the occurrence of phosphorus mist can be suppressed unless there is a sublimation point, that is, a place at 360 ° C. or lower.

Therefore, in the heat treatment apparatus of this embodiment, the lid portion is provided with the heating means and the lid portion is heated to a temperature higher than the sublimation point of P2 O5 during the diffusion treatment, so that the precipitation of P2 O5 is suppressed, and therefore the precipitation is suppressed. Since the amount of H3 PO4 produced is extremely small, the generation of particles can be reduced.

Next, a second embodiment of the present invention will be described. In this embodiment, instead of providing the heating means 21 on the lid portion 2 in the first embodiment described above, as shown in FIG. 17, an exhaust port 91 connected to an exhaust pump 92 is provided above the reaction tube 1.
To form a heat treatment apparatus.

In the heat treatment apparatus having such a structure, after the heat treatment, the carrier gas composed of N2 gas and O2 gas,
The dope gas containing POCl3 vapor in N2 gas is supplied to the reaction tube 1 through the exhaust port 91 by the exhaust pump 92.
Although the gas is exhausted to the outside, the exhaust port 91 is provided at a position apart from the lid portion 2, so that the concentration of POCl3 near the lid portion 2 becomes low. Therefore, even if the temperature of the lid portion 2 is 360 ° C. or less, the amount of P2 O5 deposited on the lid portion 2 is small, and as a result, generation of particles can be suppressed.

Next, a third embodiment of the present invention will be described. In this embodiment, instead of providing the heating means 21 on the lid 2 in the first embodiment, as shown in FIG. 18, in order to cool the lid 2 below the reaction tube 1, for example, an inert gas is used. It is characterized in that a cooling means 93 composed of a cooling gas spraying tube for spraying the cooling water onto the lid portion 2 is provided.

In such a structure, after the heat treatment, for example, before opening the lid portion 2, the lid portion 2 is cooled by the cooling means 93.
Here, the lid portion 2 is changed to H which is a reaction product of P2 O5 and water.
By quickly lowering the boiling point of 3 PO4 to 261 ° C. or less, even if P2 O5 is deposited on the lid portion 2, it quickly passes through the temperature range where H3 PO4 becomes mist and scatters, so that the generation of particles is suppressed.

In the above, in the present invention, the first to third embodiments may be combined. The gas containing phosphorus is not limited to POCl3, and the object to be processed is not limited to a wafer and may be an LCD substrate.

[0041]

According to the present invention, when heat-treating an object to be processed using a processing gas containing phosphorus and oxygen, the components of particles generated when the object to be processed is carried out are clarified, and the heating unit Since the temperature of the lid portion away from the heat treatment is set to a temperature higher than the temperature at which the precipitation of phosphorus pentoxide is suppressed, the generation of particles is suppressed.

Since the lid is cooled after the heat treatment in another invention , the lid can be quickly lowered to a temperature below the temperature at which phosphoric acid, which is a reaction product of phosphorus pentoxide and water, scatters, so that particles are not generated. It can be suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a heat treatment apparatus of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a part of the heat treatment apparatus of the present invention.

FIG. 3 is a perspective view showing an apparatus used in an experiment conducted to guide the present invention.

FIG. 4 is an explanatory diagram illustrating an experimental method.

FIG. 5 is a graph showing experimental results.

FIG. 6 is an explanatory diagram illustrating an experimental method.

FIG. 7 is a graph showing experimental results.

FIG. 8 is a flowchart illustrating an experimental method.

FIG. 9 is a graph showing experimental results.

FIG. 10 is an explanatory diagram illustrating an experimental method.

FIG. 11 is a graph showing experimental results.

FIG. 12 is a graph showing experimental results.

FIG. 13 is a graph showing experimental results.

FIG. 14 is a graph showing experimental results.

FIG. 15 is a graph showing experimental results.

FIG. 16 is a graph showing experimental results.

FIG. 17 is a sectional view showing another example of the heat treatment apparatus of the present invention.

FIG. 18 is a sectional view showing a part of another example of the heat treatment apparatus of the present invention.

[Explanation of symbols]

1 reaction tube 2 lid 21 heating means 3 wafer boat 4 heat insulation tower 6 injectors 91 Exhaust port 92 Exhaust pump 93 Cooling means

Continuation of the front page (56) Reference JP-A-2-306619 (JP, A) JP-A-3-268422 (JP, A) JP-A-5-291158 (JP, A) Actual development Sho-63-95234 (JP , U) Actual development Sho 62-152432 (JP, U) Actual development 3-25229 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/22

Claims (2)

(57) [Claims] 1. A vertical reaction tube and an opening of the reaction tube
A lid that opens and closes, and is placed on this lid via a heat insulating member.
And holding a large number of objects to be processed up and down by the holding tool and carrying it into the reaction tube through the opening, and closing the opening with the lid, phosphorus and oxygen in the reaction tube under a heating atmosphere. In a device for performing a heat treatment by supplying a processing gas containing, a heating means provided in the lid portion, a temperature detecting means for measuring the temperature of the lid portion, and a temperature detecting means based on a detection value of the temperature detecting means. During heat treatment
Any part of the surface of the lid that is exposed in the reaction tube
Is also heated to a temperature above the sublimation point of phosphorus pentoxide
And a control unit for controlling the heating means.
And heat treatment equipment. 2. A processing gas containing a large number of objects to be processed held by a holder and carried into the reaction tube through an opening and the opening is closed by a lid so that the reaction gas contains phosphorus and oxygen in a heating atmosphere. An apparatus for supplying heat to perform a heat treatment, comprising a cooling means for cooling the lid portion after the heat treatment.