JPS6016416A - Vapor growth apparatus - Google Patents

Abstract

PURPOSE:To realize preprocessing of vapor growth process at a low temperature and avoid generation of thermal stress dislocation by intermittently irradiating the surface of base material with electromagnetic wave on the occasion of obtaining a growth layer by placing the base material to be processed in the reaction reservior. CONSTITUTION:A large diameter silicon base material 3 supported by a heating pedestal 2 is accommodated in a quartz reaction reservior 1 and the heating pedestal 2 heats such silicon base material with a high frequency coil 5 provided at the rear side thereof. The heating pedestal 2 is also rotated by the rotating axis 4, the hydrogen gas as the carrier gas is supplied to the reaction reservior 1 from the gas supply nozzle 6 which runs through the heating pedestal 2, and after the surface of base material 3 is purified, the gas is exhausted from the exhaust port 7. With such a structure, an intermittent lamp 81 which is used as the flash lamp is disposed at the external upper part of reservior 1 and the base material 3 is irradiated with the light having strong energy through the irradiation lens 82. Simultaneously, the heating pedestal 2 is also heated, temperature of base material 3 is set to about 950 deg.C which is lower than oridnary temperature and sufficient preprocessing is carried out even under such temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a vapor phase growth apparatus used for processing semiconductors and the like.

[Background of the invention]

The so-called vapor phase growth technology, in which a base material (mainly single crystal) is housed in a quartz reaction vessel and is heated to a high temperature while supplying raw material gas to further stack a single crystal layer on the substrate, is used in the manufacturing process of semiconductors such as LSI. It is an important technology that is widely applied in the world. Figure 1 shows a conventional vertical vapor phase growth apparatus. A silicon single crystal substrate 3 is placed on a BiC-coated graphite heating table 2 in a quartz reaction vessel 1, and while the heating table 2 is rotated by a shaft 4, the heating table is induction heated by a high-frequency heating coil 5.
Silicon single crystal substrate 3f: Maintained at a high temperature of about 1 zoor. Next, a silicon raw material (for example, 5 ict, etc.) is supplied from the raw material gas supply nozzle 6 using hydrogen as a carrier gas to form a single crystal layer on the silicon single crystal substrate 3 (epitaxial growth).

A vapor phase growth apparatus having such a configuration has the following problems. That is, in recent years, higher integration and faster operation of LSIs have been promoted, and the planar and vertical dimensions of semiconductor devices are required to have a general and fine structure (submicron). However, high-temperature heating processes such as conventional vapor phase growth methods (especially epitaxial growth) significantly change the dimensions and impurity concentration profiles of the PM and nm impurity layers formed before the process. There are problems. One way to solve the above problems is to lower the temperature of the vapor phase growth process.

Another problem with conventional methods is thermal stress dislocations introduced during the vapor growth process. In other words, the method of heating the substrate in vapor phase growth is to first heat the heating table and indirectly heat the substrate. The temperature difference (To>Tt
) f will occur.

For this reason, the substrate is curved as shown in the figure due to the difference in thermal expansion between the front and back surfaces, and this curvature further leads to non-uniform temperature distribution (Ts<Ti) in the periphery and center of the substrate surface.
- arise. Due to this in-plane temperature non-uniformity, a large number of thermal stress dislocations are introduced into the base crystal, which is a major cause of a decrease in the yield of semiconductor devices.

In recent years, the problem of thermal stress dislocation has become more and more prominent as the diameter of substrates has been increased (4 to 6 inches) with the aim of reducing process costs and improving yields of LSIs. That is, as the diameter of the base increases, the warpage bld due to curvature of the base becomes larger (see Figure 2), so the temperature gradient d'1',''ar in the radial direction within the plane of the base also increases.On the other hand, thermal stress Temperature gradient where dislocation occurs d'l'/dr
As shown in FIG. 3, the limit becomes smaller as the diameter of the substrate increases, so thermal stress dislocation is more likely to occur in large diameter substrates.

One of the measures to reduce the problem of introducing thermal stress dislocations is to lower the heating temperature of the substrate. As shown in FIG. 3, when the substrate heating temperature is lowered, the limit of the temperature gradient d'p/dr at which thermal stress dislocation occurs for a substrate of the same diameter is significantly relaxed.

As explained above, lowering the temperature is an important issue in solving the problems of conventional vapor phase growth methods. However, simply lowering the heating temperature causes new problems such as the introduction of crystal defects during the growth process and a decrease in the growth rate due to the reduction in the applied thermal energy.

As one solution to the new problems associated with lowering the temperature of the vapor phase growth process, there is a method shown in FIG. 4.

That is, the substrate 3 is placed on a heating table 2 made of graphite, and heated in a heating furnace 52 to a temperature below the normal reaction temperature (about 100 C lower). Next, the ultraviolet lamp 8 is turned on to irradiate the surface of the substrate 3 while supplying raw material gas from the inlet 6 to perform vapor phase growth. 7 is an exhaust port. In vapor phase growth, crystal constituent atoms decomposed in a vapor phase reaction receive thermal energy on the substrate surface and rearrange, resulting in growth with the same plane orientation as the substrate.
However, in the method shown in Figure 4, in order to keep the reaction temperature low, the insufficient thermal energy is supplemented by irradiation with electromagnetic waves such as ultraviolet light, and care is taken to maintain good crystallinity. ing. On the other hand, it is also known that irradiation with ultraviolet light has the effect of increasing the growth rate.

However, even with the method shown in FIG. 4, the effect of improving crystallinity or increasing the growth rate at the mass production level has not yet been obtained, and a significant reduction in the heating temperature has not been achieved. The main reason for this is thought to be a lack of energy in the irradiated light. One way to compensate for the energy shortage is to increase the light source output. However, simply increasing the output results in an increase in the energy obtained by the substrate itself, which causes a rise in temperature, which defeats the purpose of lowering the temperature. Furthermore, the output of conventional commercially available light bulbs is limited and is insufficient as a light source for vapor phase growth, but this is due to the tendency for the diameter of the substrate to become larger and larger, as mentioned above. This is a critical problem today.

Another reason why it is difficult to lower the temperature of the vapor phase growth process is the problem of cleaning the substrate surface. Usually, a substrate for vapor phase growth is placed in a reaction vessel after a pretreatment such as acid cleaning to remove surface contamination. Further, immediately before the vapor phase growth, a new gas phase etching is performed in the reaction vessel in which the surface is heated to a high temperature in a hydrogen atmosphere to decompose and remove natural oxide films, organic substances, etc. on the surface. In order to make gas phase etching more effective, a very small amount (~0.5%) of a gas such as hydrogen chloride that corrodes the substrate may be added to the hydrogen atmosphere.

By performing such vapor phase etching, the surface of the substrate is completely cleaned, making it possible to form a high quality vapor phase growth layer free from crystal defects and various contaminations. Generally, it is said that the cleaner the substrate surface, the lower the energy for rearrangement on the substrate surface, and the lower the substrate temperature at which a single crystal layer is formed. The effect of such vapor phase etching becomes greater as the temperature of the substrate increases during the etching process.

As a result, lowering the temperature of the vapor phase growth process using conventional methods makes it difficult to form a high quality vapor phase growth layer.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of conventional vapor phase growth equipment, and to
It is an object of the present invention to provide a vapor phase growth apparatus capable of significantly lowering the temperature of the vapor phase growth process including a substrate cleaning step immediately before growth even in vapor phase growth on a large diameter substrate having an inch diameter or more.

[Summary of the invention]

The vapor phase growth apparatus of the present invention is characterized by the provision of means for intermittently irradiating the surface of the substrate to be treated with electromagnetic waves. Thereby, the temperature of the vapor phase growth process and the pretreatment process for the vapor phase growth process can be lowered.

Another feature of the vapor phase growth @ snow of the present invention is that the interval of the intermittent irradiation mentioned above is maintained at less than the time required to form a vapor phase growth layer of at least several atomic layers during the vapor phase growth. That's what I did.

[Embodiments of the invention]

The present invention will be explained below by taking silicon vapor phase growth as an example.

FIG. 5 shows a schematic diagram of an exemplary embodiment of the invention. The main difference from the conventional device is that an intermittent light panel lamp (flash lamp) is used as the ultraviolet light source 81, and strong energy light is evenly irradiated onto the entire surface of the large diameter substrate 3. The point is that an irradiation lens 82 is provided for this purpose.

The operation during growth using the vapor phase growth apparatus having such a configuration will be described below using epitaxial growth of silicon as an example.

A silicon substrate 3 with a large diameter (4 inches) is placed on a heating table 2 in a quartz reaction vessel 1, and is rotated by a rotating shaft 4 in order to obtain a uniform thickness of the vapor-phase growth layer and to make the temperature distribution uniform. It is rotated (approximately 15 rP).

After the inside of the container 1 is replaced with nitrogen, hydrogen, which becomes a carrier gas for the reaction, is flowed from the gas supply nozzle 6 at a flow rate of about 80 t/m for 2 minutes to replace the inside of the container 1 with hydrogen. Then hydrogen flow tt-
The heating coil 5 reduces the amount to about 40t/-, and the heating stand 2 is heated by the heating coil 5.
and indirectly heats the base 3. In this case, the base 3
Since the substrate is heated to a predetermined temperature (approximately 950 C) lower than the conventional growth temperature (approximately 1200 C), no thermal stress dislocation is observed despite the large diameter of the substrate. In addition, deterioration of the impurity diffusion layer formed in the substrate due to heating is suppressed to a minimum.

When the substrate 3 reaches a predetermined temperature, it is maintained as it is for about 10 minutes and subjected to hydrogen treatment to remove natural oxide films, organic substances, etc. adhering to the surface. At this time, the ultraviolet lamp 81 is turned on to irradiate the surface of the substrate 3 with ultraviolet light (wavelength of about 400 nm or less). Since the 81 ultraviolet lamps according to the present invention are flash-type lamps that are turned on at intervals of about 1/100 seconds, the intensity of the irradiated light is several orders of magnitude higher than that of ordinary continuously lit lamps. Therefore, even if the large-diameter substrate 3 is uniformly irradiated with the irradiation lens 82, the intensity of the irradiated light on the substrate surface is two to three orders of magnitude higher than in the conventional method.

FIG. 6 schematically shows the relationship between the lighting intensity of the lamp and time. The total energy J of the light pulse reaches about several joules, but the irradiation time is very short.
(ns) Therefore, the irradiation intensity I (W/crl) of the large diameter substrate LO1i8(il) is several hundred W4 from the following equation (1).
− becomes.

If strong energy is irradiated onto the surface of the substrate, there is a concern that the temperature will rise. However, since the irradiation time is very short, the temperature rise remains at a minimum, and since the temperature rise is limited to an extremely thin portion on the surface side of the substrate, no deterioration of the substrate or generation of thermal stress dislocation occurs.

Strong ultraviolet energy'f is generated by intermittent irradiation during hydrogen treatment.
: By applying it to the substrate surface, the surface is activated, and surface cleaning is further promoted compared to when only hydrogen treatment is used.

Incidentally, since surface cleaning by vapor phase etching is performed in the same reaction vessel, electromagnetic wave irradiation may be performed in one pulse irradiation if instantaneous cleaning is achieved. For example, depending on the degree of alteration of the substrate surface, there is a method of instantly purifying the surface by actively heating or melting a portion near the surface using an infrared flash lamp, etc., which is different from the lamp used during growth. There is.

After cleaning the substrate surface for 5 minutes, while irradiating the substrate with ultraviolet light, approximately 1 mo 1% silicon raw material (for example, 5iCt4) and a doping gas to suppress the resistance of the growth layer are simultaneously supplied to perform vapor phase growth. Start. The growth rate in this case is about 1 μm/RiR, and the time it takes to form one atomic layer on the substrate 3 is calculated from this growth rate to be about 1/100 seconds, although it varies depending on the plane orientation of the substrate crystal. It will be about. From this, even if ultraviolet light is irradiated in an intermittent manner of about 1/100 seconds, strong energy is supplied to the substrate surface every time at least a few atoms of Mt are formed, and the rearrangement of the crystal constituent atoms is sufficiently achieved. be done. As a result, the lack of crystal growth energy due to lowering the temperature is compensated for, and it becomes possible to form a high quality vapor phase growth layer with few crystal defects. Further, even though the growth temperature is lowered by irradiation with ultraviolet light with high energy density, the growth rate can be maintained at a sufficient production level. Of course, even during the vapor phase growth process, since the growth temperature is low, thermal stress dislocations and deterioration of the substrate diffusion layer do not occur.

After forming a growth layer (epitaxial layer) of a predetermined thickness, the supply of source gas is stopped. After holding the kneading for 1 minute and purging the remaining raw material gas, the ultraviolet lamp 81 is turned off, and then the output of the heating device 5 is lowered to lower the temperature of the substrate.

After cooling with hydrogen gas for several minutes and replacing the inside of the reaction vessel 1 with nitrogen gas, the substrate 3 is taken out and the vapor phase growth process is completed. On the other hand,
This is an apparatus for forming a vapor phase growth layer.

This device is designed to reduce the temperature of large-diameter substrates and to solve the problem of reduced productivity as a result.

That is, in order to keep the temperature gradient d'l'/dr of the substrate 3 smaller than in the conventional method, the substrate heating device 51 has been improved to an infrared radiation type, and furthermore, this infrared lamp 51 is installed on the upper surface side of the substrate 3. are placed only. As a result, the substrate heating is
This is done directly from the front side, reducing the temperature difference between the front and back sides of the substrate. Therefore, the curvature of the base body 3 is reduced and the temperature gradient dT/dri can be kept small. On the other hand, arranging the infrared lamp 51 on the upper surface side of the base makes it difficult to uniformly irradiate ultraviolet light, but if the lamp is arranged in a conical or pyramidal shape,
The top part 83 of the cone is opened, and it is devised so that ultraviolet light can be irradiated through this part.

The method of batch processing by charging a large number of large-diameter substrates 3 into the reaction vessel 1 has many drawbacks in terms of uniformly forming a vapor-phase growth layer, uniform heating, and uniform ultraviolet light irradiation. uses a single-wafer processing method. In this case, in order to prevent a reduction in throughput, this device adopted a cassette-to-cassette method. Connecting members 100, 200 for loading and unloading substrates 3 are provided in the low-temperature portion of the reaction vessel 1, and substrate storage boxes 102, 202 for storing substrate storage cassettes (101, 201) are connected to the other end. Gates 103 and 203, which can be opened and closed, are provided in the central portions of the connecting members 100 and 200, so that the reaction container 1 and the substrate storage boxes 102 and 202 are separated from each other. In addition, the storage box 102
, 202, hydrogen gas is constantly introduced from gas supply ports 104, 204 and is discharged from exhaust ports 105, 205 provided in the connecting members 100, 200. The substrate 3, which has finished vapor phase growth and has been cooled in a hydrogen atmosphere, is connected to the heating table 2 by a broken line 21.
The connecting member is moved to the same position as the 100° and 200° positions. Next, storage box 2 for processed substrates
The gate 203 on the 02 side is opened, and the base 3 is transferred to the storage box 202 by the loader 206. At the same time as closing the gate 203, the gate 10 on the side of the storage box 102 for the substrate to be processed
3 is opened, and the next substrate 3 is set on the heating table 2 by the loader 106. Move the heating table 2 to a predetermined position,
The next vapor phase growth step is continued by starting heating with the heat lamp 51.

According to the single wafer processing method of the present apparatus described above, since the reaction vessel 1 is not opened and closed, the nitrogen purge step for explosion prevention can be omitted, reducing processing time and improving throughput. I can do it.

In this embodiment, the newly developed silicon homoepitaxial growth in which a silicon single crystal is formed on a silicon single crystal substrate has been described as an example, but the present invention can of course also be applied to heteroepitaxial growth.

Furthermore, when forming a polycrystalline layer or even an amorphous layer on a single-crystal substrate, there are concerns about the introduction of thermal stress dislocations into the substrate single crystal, and further problems such as alteration of the substrate structure during the heat treatment process. The present invention is effective when a reaction temperature as high as that required is required.

Furthermore, in the above description, the semiconductor substrate loading method was explained using water droplet loading as an example, but the present invention is not limited to this.

Further, in this embodiment, an example is given in which an ultraviolet lamp is used as a light source, but as the electromagnetic wave source, it is free to appropriately select a source that generates electromagnetic waves with an effective energy density, such as a laser light source.

Further, as described in the description of the embodiment, it is also possible to use electromagnetic wave sources with different wavelengths of irradiated electromagnetic waves in the substrate surface cleaning step immediately before vapor phase growth and during vapor phase growth.

Furthermore, it is of course possible to select electromagnetic wave irradiation for either the cleaning process of the substrate surface or the vapor phase growth reaction process.

〔Effect of the invention〕

By the apparatus of the present invention explained above, p j of 6 inch diameter
jl y nff1 of about 2 μm on the silicon substrate, resistivity 1
When the formation of a vapor phase growth layer of Ωm was repeated 20 times at a substrate temperature of 950C, no substrate was observed in which thermal stress dislocations had occurred. In addition, n-type impurity (Sb) formed within this substrate (10 μm x 10 μm x 1.8 μm depth,
At a surface concentration of about 2 x 10' m-3), the change in planar dimension was about 0.1 μm, which was significantly reduced compared to the conventional method. As described above, according to the present invention, it is possible to significantly reduce the vapor phase growth temperature without causing any inconvenience.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a conventional vapor phase growth apparatus, Figures 2 and 3
4 is a schematic diagram illustrating another example of the conventional vapor phase growth apparatus. FIG. 5 is a schematic cross-sectional view showing an embodiment of the vapor phase growth apparatus of the present invention. 6 is a waveform diagram of electromagnetic waves used in the present invention, FIG. 7 is a schematic sectional view of another embodiment of the vapor phase growth apparatus of the present invention, and FIG. 8 is a perspective view of FIG. 7. DESCRIPTION OF SYMBOLS 1... Reaction container, 2... Heating stand, 3... Substrate, 5
... Heating device, 8... Ultraviolet run 6 81-... Intermittent lighting type ultraviolet lamp. #I Figure Certain 3m 4th H $5fEJ 1

Claims (1)

[Scope of Claims] 1. A reaction vessel, a heating table placed in the reaction vessel on which a substrate to be treated is placed, and means for supplying a reaction gas into the reaction vessel and discharging the gas after the reaction. 1. A vapor phase growth apparatus comprising: , means for intermittently irradiating electromagnetic waves onto a basic surface within a reaction vessel; 2. A vapor phase growth apparatus according to claim 1, characterized in that electromagnetic waves having a wavelength of 400 nm or less are used. 3. Bi! 1. A vapor phase growth apparatus according to claim 1 or 2, characterized in that the irradiation interval of electromagnetic waves is in the range of 1 second to 11,500 seconds.