JPH0927456A - Semiconductor processing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the controllability and repeatability of a process by installing a mechanism to keep monitoring the concentration of reactive gas in a chamber, and allowing the gas concentration to reach a value set by a mass flow controller before starting the process. SOLUTION: After a wafer 5 is placed in a chamber 4, nitrogen is introduced into the chamber 4 through a carrier gas pipe 2 to obtain a nitrogen atmosphere. Thereafter, hydrogen is introduced. When the interior of the chamber has been completely turned into a hydrogen atmosphere, diborane gas diluted with hydrogen is introduced through a reactive gas pipe 3. The concentration of the reactive gas is checked using a reactive gas concentration measuring instrument 20. When the concentration of the reactive gas reaches a specified value, a heating lamp 8 is turned on to heat the wafer and diffuse boron. This makes it possible to reduce deviations between batches, such as the sheet resistance and film thickness of wafers, to 1/3 or so.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing apparatus excellent in process controllability and reproducibility.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. This is a chemical vapor deposition apparatus for depositing polycrystalline silicon. In this apparatus, after the wafer 5 is installed in the chamber 4, a gas such as nitrogen is flown from the carrier gas line 2,
The inside of the chamber 4 is replaced. Next, the pressure inside the chamber is reduced by the vacuum pump 7, and a reactive gas such as monosilane is flown through the process gas line 3 and the bypass 14,
Thoroughly purge the inside of the piping. Then, a reactive gas is introduced into the chamber together with a carrier gas to deposit polycrystalline silicon. In addition, this technique is S. M. Sze, VLSI
Technology, McGraw Hill,
p. 236.

Another conventional example will be described with reference to FIG. This is an atmospheric pressure lamp annealer equipped with an oxygen concentration measuring device in order to grasp the replacement state of the process gas. In such an apparatus, since the door 12 is opened when the silicon wafer 5 is installed in the chamber 4, the air is always entrained in the chamber. Therefore, the oxygen concentration measuring device 10 is installed via the suction line 13, and the oxygen concentration is measured while the process gas is introduced from the mass flow controller 1. Then, when the residual oxygen concentration caught during the loading and unloading of the wafer is sufficiently lowered, the wafer is heated using the lamp 8 to perform a process, thereby suppressing undesired oxidation and performing a good annealing process. The present technology is described in Japanese Patent Laid-Open Publication No. 4-264734.

[0004]

In the conventional example shown in FIG. 1, the flow rate of the reactive gas is controlled by the mass flow controller 1. Especially, the concentration of the reactive gas in the chamber immediately after the start of deposition is controlled by the mass flow controller. It does not follow the flow rate. Further, the concentration thereof varies depending on the degree of purging in the pipe or the presence / absence of leak. In this case, there is a problem that the deposition time is short, it is difficult to control the film thickness when forming a thin semiconductor film, and reproducibility is poor. In order to avoid this problem, a sufficient amount of reaction gas is allowed to flow through the bypass line before the deposition, and the gas is introduced into the chamber when the concentration in the pipe becomes stable. Therefore, there is also a problem that it is difficult to reduce the process time. Further, in the conventional example shown in FIG. 2, it is possible to measure the oxygen concentration involved in the wafer installation, but it is impossible to monitor the gas concentration during the actual process. Therefore, as in the case of FIG. 1, the process gas is controlled only by the mass flow controller, which causes the above problem.

[0005]

In order to solve the above-mentioned problems, in the present invention, a mechanism for constantly monitoring the reaction gas concentration in the chamber is installed, and the process is performed after the gas concentration as set by the mass flow controller is reached. To do.

[0006]

With the reactive gas concentration monitor mechanism, the concentration of the reactive gas with respect to the carrier concentration can be accurately grasped. By starting the process after the reaction gas concentration reaches the flow rate ratio controlled by the mass flow controller, an extremely thin semiconductor film can be formed with good reproducibility.

[0007]

FIG. 3 shows an embodiment of the present invention described in claims 1 and 2. This device is an atmospheric pressure impurity diffusion device equipped with a reactive gas concentration measuring device 20. After placing the wafer 5 in the chamber 4 via the load lock chamber, nitrogen was introduced into the chamber via the carrier gas pipe 2. The nitrogen flow rate is 10 l / min. After the inside of the chamber became a nitrogen atmosphere, the gas was switched to hydrogen and the inside of the chamber was made a hydrogen atmosphere. The hydrogen flow rate is also 10 l / min. After confirming that the atmosphere was completely hydrogen by a reactive gas measuring instrument, diborane gas diluted with hydrogen to 0.1% was introduced through the reaction gas pipe 3 at 100 ml / min.
At this time, the flow rate ratio of the reactive gas (diborane) and the carrier gas (hydrogen) is 10 ppm, but the instruction of the reactive gas concentration measuring device 20 has not reached that value immediately after the introduction of diborane. After flowing hydrogen and diborane for 5 minutes, it was confirmed that the reactive gas concentration measuring instrument 20 indicated 10 ppm, and the heating lamp 8 was turned on to heat the wafer to 900 ° C. The heating rate is 50 ° C. per second. Wafer temperature is 9
After reaching 00 ° C., the temperature was kept for 10 seconds to diffuse boron. As a result, a boron diffusion layer having a surface boron concentration of 1 × 10 20 per cubic centimeter, a diffusion depth of 20 nm, and a sheet resistance of about 8 kOhm could be formed.
The sheet resistance measuring device at this time is shown in FIG. When the reaction gas concentration measuring device was not used, the sheet-to-batch deviation of the sheet resistance was 7.07%, but it could be reduced to 2.30% by using the reaction gas concentration measuring device. The reactive gas measuring system used at this time is shown in FIG. The gas in the device exhaust pipe is introduced into the sampling line through the filter 25. The sampling line is sucked by the suction pump 11. The sampling gas that has passed through the three-way valve 23 for introducing the measuring instrument calibration gas, the flow rate adjusting valve 21, and the flow meter 22 is introduced into the reactive gas concentration measuring instrument 20, where the reactive gas concentration in the carrier gas is measured. The exhaust gas of the suction pump 11 returns to the exhaust pipe again. A flame arrestor 24 is installed at the gas inlet and outlet of this sampling line so that the flame that may occur in the measuring instrument will not reach the chamber. FIG. 6 is an example of measurement of the diborane concentration in the chamber when the above process is performed. The time t1 elapses until the flow ratio of the diborane gas to the carrier gas controlled by the mass flow controller reaches 10 ppm. The lamp 8 is turned on from time t1 to heat the wafer. After diffusing for a predetermined time, diborane introduction and wafer heating were stopped at time t3. From the results of the diborane concentration measurement, by controlling the time t3 to t2 as the diffusion time, the batch-to-batch deviation of the sheet resistance was reduced as shown in FIG.

FIG. 7 shows another embodiment of the present invention as set forth in claims 1 and 2, and nitrogen or hydrogen as a carrier gas and monosilane as a raw material gas are flowed to form a silicon thin film. It is a vapor deposition apparatus. It is also possible to dope by simultaneously flowing diborane or phosphine gas. In this apparatus, a wafer is placed in a chamber, and when the wafer temperature stabilizes, introduction of a reactive gas is started to form a silicon-based thin film. The chamber is evacuated by the dry pump 27, and the chamber pressure during the process can be controlled to several tens to several hundred Torr by the automatic pressure control valve 31. 20 l / min of hydrogen and 1 ml / min of monosilane diluted with hydrogen to 2% as a material gas were flowed through the carrier gas pipe 2. At this time, the concentration of monosilane gas with respect to the carrier gas is 1 ppm. Pressure during growth is 40 Torr,
The substrate temperature was 650 ° C. The reproducibility was improved by monitoring the monosilane concentration at this time with the measuring device 30 and controlling the thin film growth time by the method shown in FIG. In addition,
The gas concentration measuring system shown in FIG. 7 can be installed between the mass flow controller 1 and the reaction chamber 4 as shown in FIG. Although the reaction gas concentration during thin film growth cannot be accurately measured by the method of FIG. 7, in FIG. 8, since the gas concentration immediately before the chamber flow is measured, it can be monitored during thin film growth.

FIG. 9 shows another embodiment of the present invention as set forth in claims 1 and 3, which is a lamp heating apparatus for oxidizing or nitriding silicon by flowing oxygen or ammonia with nitrogen as a carrier gas. . A wafer was placed in the chamber 4, the inside of the chamber was replaced with nitrogen, and then oxygen or ammonia was introduced. At this time, the flow rate of nitrogen is 1 l / min and the flow rate of oxygen or ammonia is 1 m.
It was from 1 / min to 10 ml / min. The oxygen or ammonia concentration with respect to nitrogen in the chamber is monitored by the oxygen concentration measuring device 32 or the ammonia concentration measuring device 33, and after reaching the flow rate ratio flowing through the mass flow controller, the heating lamp 8 is turned on to set the film thickness to 5 nanometers. An oxide film or a nitride film having a length of less than or equal to a meter was formed. By constantly monitoring the oxygen or ammonia concentration in the chamber, the variation in film thickness between batches could be reduced to 1/3 of the conventional one.

FIG. 10 shows another embodiment of the present invention described in claims 1 and 4, and is a principle diagram of a gas concentration measuring device by a potentiostatic electrolysis method. This measuring instrument is a method for measuring an electric current generated during an electrolytic reaction of a target component gas. When the reaction gas contacts the working electrode 46, an electrolytic reaction occurs on the electrode. Due to the hydrogen ions generated there, the counter electrode 43
The reaction also occurs on the top, and the electric current flows in the external circuit. The current is detected by the ammeter 42, converted into gas concentration and output.

FIG. 11 shows another embodiment of the present invention described in claims 1 and 4, and is a principle diagram of a gas concentration measuring device by the galvanic cell method. The reaction gas is the diaphragm 4
8 and is absorbed by the electrolyte thin film on the surface of the working electrode 49 to cause a redox reaction. An equivalent reaction occurs also in the reference electrode 50, and at that time, a current directly proportional to the reaction gas concentration is generated. By equipping the semiconductor manufacturing apparatus with the gas concentration measuring device as shown in FIGS. 10 and 11, an apparatus excellent in reproducibility and controllability could be realized.

[0012]

The reproducibility of the process is improved by constantly monitoring the gas concentration in the reaction chamber and carrying out the process after the gas concentration ratio reaches the flow rate flowing through the mass flow controller. Specifically, the batch-to-batch deviation such as the sheet resistance or the film thickness of the processed wafer can be reduced to about 1/3.

[0013]

[Brief description of drawings]

FIG. 1 is a schematic view of a conventional CVD apparatus.

FIG. 2 is a schematic view of a CVD apparatus equipped with a conventional oxygen detector.

FIG. 3 is a schematic diagram of a CVD apparatus showing an embodiment of the present invention.

FIG. 4 is a diagram showing a sheet resistance measurement result.

FIG. 5 is a gas sampling piping diagram showing an embodiment of the present invention.

FIG. 6 shows gas concentration measurement results showing an example of the present invention.

FIG. 7 is a schematic view of a CVD apparatus showing an embodiment of the present invention.

FIG. 8 is a schematic view of a CVD apparatus showing an embodiment of the present invention.

FIG. 9 is a schematic view of a CVD apparatus showing an embodiment of the present invention.

FIG. 10 is a schematic diagram of a gas detection method.

FIG. 11 is a schematic diagram of a gas detection method.

[Explanation of symbols]

1 ... Mass flow controller, 2 ... Carrier gas pipe, 3 ... Reactive gas pipe, 4 ... Chamber,
5 ... Wafer, 6 ... Heater, 7 ... Vacuum exhaust pump, 8 ... Heating lamp, 9 ... Exhaust pipe, 1
0 ... Oxygen sensor, 11 ... Suction pump, 12 ...
・ Chamber door, 13 ... Suction line, 14 ... Bypass, 15 ... Chamber exhaust pipe, 20 ... Reactive gas concentration measuring instrument, 21 ... Flow rate adjusting valve, 22 ...
..Flow meter, 23 ... 3-way valve, 24 ... Flame arrester, 25 ... Filter, 26 ... Automatic pressure control valve, 27 ... Dry pump, 28 ... Gas mixing line, 30 ... Monosilane concentration measuring device, 31
... Diborane concentration measuring device, 32 ... Oxygen concentration measuring device, 33 ... Ammonia concentration measuring device, 40 ... Reference battery for reference electrode, 41 ... Amplifier, 42 ... Ammeter, 43 ... Counter electrode, 44 ... Reference electrode, 45 ...
Electrode liquid phase, 46 ... Working electrode, 47 ... Electrolyte, 4
8 ... diaphragm, 49 ... working electrode, 50 ... reference electrode.

Claims (4)

[Claims] 1. A semiconductor manufacturing apparatus for heating a semiconductor substrate in a chamber to form a thin film on a semiconductor, diffuse impurities, or oxidize a reactive gas and a carrier gas. A semiconductor manufacturing apparatus equipped with a mechanism for sampling the gas and constantly monitoring the concentration of the reactive gas. 2. The carrier gas is nitrogen, hydrogen, argon, helium, or the like, the reactive gas has a function of depositing silicon, and silicon is N type,
2. The semiconductor manufacturing apparatus according to claim 1, wherein one or both of gases containing an element having an action of converting to P-type. 3. The carrier gas is nitrogen, hydrogen, argon, helium or the like, and the reactive gas is one or both of a gas having a function of depositing silicon and a gas containing oxygen or nitrogen. The semiconductor manufacturing apparatus according to claim 1, wherein: 4. A system for monitoring the concentration of the reaction gas, which detects a current associated with electrolysis of the reaction gas (potential potential electrolysis method) or a current associated with a redox reaction of the reaction gas passing through the diaphragm. 2. The semiconductor manufacturing apparatus according to claim 1, wherein the semiconductor manufacturing method is a method (galvanic cell method).