JPH06242001A - In situ semiconductor process observing system employing laser raman spectroscopy - Google Patents

Abstract

PURPOSE:To provide a system for observing the characteristics of a semiconductor under processing in real time using laser Raman spectroscopy. CONSTITUTION:An electric furnace 1 contains a heater 2 and is inserted with a silicon reaction tube 4 containing a semiconductor 3 to be processed. The silicon reaction tube 4 is provided with a flat window 5 at the tip thereof and the semiconductor 3 is held while standing in the vicinity of the tip of the silicon reaction tube 4 with the surface thereof opposing the window 5. A gas introduction pipe 7 has an ejection end extending to the tip part of the silicon reaction tube 4. An alumina tube 9 surrounds the silicon reaction tube 4. A laser light source 11 and a spectrometer 12 are disposed on the window 5 side. The semiconductor 3 is irradiated with a laser light L emitted from the laser light source 11 and Raman light emitted from the semiconductor is introduced to the spectrometer through a connection optical system 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for in-situ observation of a semiconductor being processed by laser Raman spectroscopy.

[0002]

2. Description of the Related Art Various analysis techniques are used for evaluating the characteristics of semiconductors, and it is known that the following characteristics can be evaluated by laser Raman spectroscopy. 1) Disorder of crystal structure and its recovery 2) Crystal plane orientation 3) Stress in material 4) Carrier density in crystal 5) Impurity in crystal 6) Identification of substance For example, regarding the above 1), when ion implantation is performed The crystal structure of the semiconductor is disturbed and becomes amorphous, or a peak due to TO phonon, which is originally forbidden on the (100) plane of a semiconductor having a zincblende crystal structure, is observed in the Raman spectrum. When such a semiconductor is annealed, the structure is recovered, and a crystalline peak appears in the Raman spectrum or a forbidden mode peak disappears, whereby the recovered state can be confirmed. However, if it is annealed excessively, the structure may be disturbed, and such a state can be determined from the Raman spectrum.

[0003]

By the way, in the laser Raman spectroscopy capable of evaluating various characteristics of the semiconductor as described above, it has been difficult to observe the state during processing in real time in situ. In other words, most of the semiconductor processes are accompanied by heating, and most of them are in the environment of 500 to 600 ° C or higher, and often in an atmosphere other than vacuum.
This is because it was technically difficult to perform Raman measurement in such an environment. Therefore, there has been no report that Raman spectroscopy performed in-situ observation of the semiconductor being processed.

The present invention has been made in view of the above points, and an object thereof is to provide an apparatus capable of observing the characteristics of a semiconductor being processed in real time by laser Raman spectroscopy.

[0005]

In order to achieve this object, an apparatus for in-situ observation of a semiconductor process by laser Raman spectroscopy according to the present invention is provided with a heating furnace and a semiconductor to be processed, which is arranged in the heating furnace. A reaction vessel, a gas introduction means for introducing a processing gas into the reaction vessel, a laser light source, and a semiconductor in the reaction vessel irradiated with laser light from the laser light source from outside and Raman light from the semiconductor. A window provided in the heating furnace for taking out to the outside, and a spectrometer into which the Raman light taken out to the outside through the window is introduced, and the reaction vessel is a laser introduced through the window. It is characterized in that it has a laser light transmitting portion for allowing light to reach an internal semiconductor, and the semiconductor is arranged in a portion facing the window in the reaction container.

[0006]

In the present invention, the laser light from the laser light source is applied to the semiconductor in the reaction vessel through the window provided in the heating furnace and the laser light transmitting portion provided in the reaction vessel, and The Raman light from is taken out of the heating furnace following the reverse path, introduced into the spectrometer, and detected. The gas introducing means introduces the gas into the reaction container so that the gas flows from the laser light transmitting part side in the reaction container to the opposite side, so that the laser light transmitting part is contaminated by the products generated by the gas introduction. Raman measurement can be performed while preventing. An embodiment of the present invention will be described below in detail with reference to the drawings.

[0007]

1 shows an embodiment of the present invention. In the figure, reference numeral 1 denotes an electric furnace, which has a heating element 2 therein. A quartz reaction tube 4 accommodating a semiconductor 3 to be processed is inserted inside the electric furnace 1. The tip of the quartz reaction tube 4 is formed as a flat window 5 so that light can easily pass therethrough, and the semiconductor 3 is held upright near the tip of the quartz reaction tube 4 so that its surface faces the window 5. ing. The electric furnace 1 is also provided with a window 6 through which the window 5 of the quartz reaction tube 4 can be seen from the outside of the furnace.

Reference numeral 7 is an introduction tube for introducing gas into the quartz reaction tube 4, and its jet end extends to the tip of the quartz reaction tube 4. Reference numeral 8 is a discharge tube for discharging gas from the end of the quartz reaction tube 4, 9 is an alumina tube interposed between the quartz reaction tube 4 and the heating element 2, and 10 is not shown because it detects the temperature in the vicinity of the semiconductor. It is a thermocouple that sends a detection signal to the electric furnace heating control device.

The laser light source 11 and the spectrometer 12 constituting the Raman spectrometer are arranged on the side of the window 5 and the semiconductor laser is irradiated with the laser light L from the laser light source 11 to emit the Raman light from the semiconductor to the spectrometer 12. Optical system 13 for guiding to
Has been added. The connection optical system 13 includes lenses 14 and 15 for converging the Raman light R extracted from the semiconductor surface toward the spectrometer 12, and the laser light source 11.
It is composed of a lens 18 and a reflecting mirror 19 for irradiating the laser light L generated from the laser beam L and guided through the interference filter 16 and the reflecting mirror 17 onto the semiconductor surface through the window 5 while being converged.

In the above-mentioned structure, the connection optical system 13 is set so as to efficiently extract the Raman light R from the semiconductor surface in a direction substantially perpendicular to the semiconductor surface and guide it to the spectrometer 12, and directly. The laser light L is set to enter the semiconductor with a small incident angle so as not to be introduced into the spectrometer. A semiconductor is processed by introducing gas into the quartz reaction tube 4 under heating by an electric furnace while performing Raman spectroscopy measurement based on such a configuration. At this time, it is inevitable that a reaction product is generated and adheres to the inner wall surface of the quartz reaction tube 4. However, since the gas flows in the quartz reaction tube 4 from the end window 5 side to the end side, the reaction product Is significantly suppressed from adhering to the window 5. For this reason,
It is possible to efficiently introduce the laser light L and take out the Raman light R through the window 5 for a long time, and it is possible to significantly reduce the frequency of the work for removing the adhered matter.

Further, since the heating element 2 emits light having a wide wavelength in an incandescent state in a normal use state, if the alumina tube 9 is not provided, the light from the heating element 2 is reflected on the semiconductor surface. Then, the present inventor has confirmed that it reaches the spectrometer 12 and appears as noise in the Raman spectrum acquired by the spectrometer. In this embodiment, since the outer circumference of the quartz reaction tube 4 is surrounded by a tube made of alumina that hardly emits light even at high temperatures, it is possible to prevent the light from the heating element 2 from reaching the spectrometer. It is possible to prevent noise from entering the spectrum. Although alumina is used as the material in this embodiment, another substance that does not easily emit light at high temperature may be used, and the surface of the heating element may be covered with a substance that does not easily emit light even at high temperature.

GaP / Si in FIGS. 2 and 3 are Raman spectra (G) from GaP grown on a silicon substrate.
a P TO phonon). Figure 2 is growing 70
It was measured at 0 ° C., and FIG. 3 is measured at room temperature after cooling after growth. In FIG. 2 and FIG. 3, “Ga P bulk” indicates a spectrum when Ga P alone is used as a reference. It can be seen that even during growth, a good-quality spectrum comparable to that measured at room temperature was obtained.

The TO phonon of growing Ga P is
Ga P is on the higher wave number side than that of Ga P alone and is growing.
It can be seen that there is compressive stress. On the other hand, the TO phonon of Ga P cooled to room temperature is on the lower wave number side than the case of Ga P alone, and it can be seen that Ga P after cooling has a tensile stress. Such a change in stress was clarified for the first time by measurement using the device of the present invention.

As described above, according to the present invention, the in-situ observation of the semiconductor process by the Raman spectroscopy is possible. An application example using the in-situ observation will be illustrated below. 1) In-situ observation of the recovery process of the crystal structure by annealing makes it possible to determine the optimum annealing time that does not lead to excessive annealing. 2) In order to form polycrystalline silicon, there is a method of depositing amorphous silicon and then heating, but an appropriate heating condition can be determined by observing the progress of crystallization in situ. 3) When growing a crystal on a substrate having a step or a groove, it has not been clarified what the plane orientation of the grown surface is. If the growth process is observed in-situ, it is possible to stop the growth at the time when a deviation of the plane orientation of a certain amount or more occurs, if necessary. 4) When a heterogeneous semiconductor is grown on a semiconductor substrate (heteroepitaxial growth) or a silicon oxide film or a silicon nitride film is formed on the semiconductor, stress is generated in the semiconductor due to the difference in lattice constant and thermal expansion coefficient. However, since a defect may occur in the semiconductor in order to relax the stress, it is impossible to accurately calculate the resulting stress in advance. If in-situ observation confirms the occurrence of stress up to the allowable limit, it is possible to stop further deposition. 5) When ions are implanted into a semiconductor, ions work electrically and carriers are generated, so that annealing is necessary. By in-situ observation, measurement of carrier density,
If impurities entering the lattice position can be observed, the annealing can be stopped and the deterioration of the semiconductor due to excessive annealing can be prevented.

[0015]

As described in detail above, according to the present invention, an apparatus capable of observing the characteristics of a semiconductor being processed in situ by laser Raman spectroscopy is realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a Raman spectrum of Ga P during growth at 700 ° C.

FIG. 3 is a diagram showing a Raman spectrum of Ga P at room temperature after growth.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Heating element 3 Semiconductor 4 Quartz reaction tube 5 Window 6 Window 7 Introduction tube 8 Discharge tube 9 Alumina tube 10 Thermocouple 11 Laser light source 12 Spectrometer 13 Connection optical system

Claims (3)

[Claims] 1. A heating furnace, a reaction container that accommodates a semiconductor to be processed and is arranged in the heating furnace, a gas introduction unit for introducing a processing gas into the reaction container, and a laser light source. A window provided in a heating furnace for irradiating the semiconductor light in the reaction container with laser light from the laser light source from the outside and taking out Raman light from the semiconductor to the outside, and Raman taken out to the outside through the window And a spectrometer into which light is introduced, wherein the reaction vessel has a laser light transmitting portion for making laser light introduced through the window reach an internal semiconductor, and the semiconductor is the reaction vessel inside the reaction vessel. Semiconductor process in-situ observation apparatus by laser Raman spectroscopy characterized in that it is arranged at a portion facing a window 2. A laser Raman spectroscopic method according to claim 1, further comprising: a shield formed between the outer peripheral surface of the reaction container and the inner surface of the heating furnace, the shield being made of a material that hardly emits light even at high temperatures. Semiconductor process in-situ observation equipment. 3. The gas introducing means is configured to introduce the gas into the reaction container so that the gas flows from the laser light transmitting portion side to the opposite side in the reaction container. In-situ observation system for semiconductor processes by laser Raman spectroscopy.