JPH04211116A - Semiconductor fabricating apparatus - Google Patents

Abstract

PURPOSE:To form a uniform semiconductor layer on a substrate by controlling the concentration profile of material gas. CONSTITUTION:A reaction chamber is defined by an inner vessel 33 and an outer vessel 32. The reaction chamber is formed such that gas is introduced from the top thereof and fed, substantially in unilateral, toward a base 31. A susceptor 34 holds a substrate 35 so that the surface thereof will be substantially in parallel with the gas flow in the reaction chamber. A plurality of ring type lamps 36 are disposed, substantially in parallel with the main surface of the base, at different positions in vertical direction on the inside of the inner vessel 33. The plurality of ring type lamps are controlled individually.

Description

[Detailed description of the invention]

[00011

FIELD OF INDUSTRIAL APPLICATION The present invention generally relates to an apparatus for forming a semiconductor layer, and more particularly to an MOCVD apparatus for forming a semiconductor layer on a substrate by metal organic vapor phase epitaxy. [0002] Metalorganic chemical vapor deposition (hereinafter referred to as MOCVD) is one of the main methods for forming a compound semiconductor layer with a complex composition on a substrate. This method is
It is essential for manufacturing ultra-high speed semiconductor devices using V group bioconductor materials. [0003] In the MOCVD method, a semiconductor layer is formed by thermally decomposing an organic or hydride source gas containing a group III element such as aluminum, gallium, and indium, and a group II element such as arsenic and phosphide. Then, the raw material gas is guided into a reaction tube holding a semiconductor substrate, and subjected to thermal decomposition treatment by a resistance heating section, an induction heating section, or a radiation heating section using a high power lamp. As a result of the decomposition, the group III and group II elements in the source gas are decomposed and deposited on the substrate in the form of a desired group III-V compound semiconductor layer. [0004] In this MOCVD method, the properties of the compound semiconductor layer vary greatly depending on the temperature on the substrate. For example, when forming a compound semiconductor layer consisting of three or four atoms while controlling attributes such as stoichiometry, composition, and thickness, it is necessary to keep the semiconductor layer forming temperature as uniform as possible. Otherwise, the properties of the obtained semiconductor layer are
varies from place to place on the surface of the substrate. Even in the case of forming a compound semiconductor device made of simple two elements such as GaAs, if the semiconductor layer is doped and there is non-uniformity in the formation temperature of the compound semiconductor layer along the substrate surface, the carrier concentration of the obtained semiconductor layer will be The level may vary depending on location on the substrate surface. Even if the dopant element is introduced at a given concentration, activation must occur by introducing the dopant into a crystal lattice location in the compound semiconductor material, but such activation will occur at a temperature in the tube in which the formation takes place. It should be noted that this will be strongly affected. [00051 In order to control the attributes of a compound semiconductor layer formed by MOCVD, it is necessary to adjust the temperature of the substrate itself and the gas as uniformly as possible, rather than the temperature of the susceptor that holds the substrate. In other words, the temperature of the gas in contact with the substrate must be controlled as constant as possible. When the gas is first introduced into the reaction tube, the gas is at a low temperature, typically around room temperature, and is heated while flowing through the reaction tube. Therefore, uniform heating of the substrate susceptor or holder is not sufficient to obtain uniform quality in the formed compound semiconductor device, and complex temperature control capabilities of the heating section are required to obtain the desired uniform quality. required. [0006] Radiant heating configurations using high power lamps are advantageous in this regard because they can provide easily controlled temperature profiles by using several lamps and controlling each lamp individually. On the other hand, conventional resistance heating configurations or induction heating configurations have different temperature profiles,
It lacks flexibility in adapting to gas flow rate, gas composition, etc. BACKGROUND OF THE INVENTION FIG. 4 shows a prior art MOCVD apparatus that uses multiple lamps for heating. This device is a device disclosed by Fr1jlink (Fri
link, P, M, , ”A New Vers
at ile, Large 5ize MOVPE
React. r, “J, Crystal Growth vol.
93. pp 207-215.1988) q With reference to FIG. 4, the apparatus consists of a reactor 10 with a reaction chamber 10a into which a gas or gas mixture is introduced via a tube 11. The tube 11 has a conical nozzle lla for distributing gas into the reaction chamber 10a, and the reaction chamber 10a has a circular configuration when viewed in plan view, and the gas guided through the nozzle lla is radially distributed in the horizontal direction. It is designed to flow. After thermal decomposition, the gas is discharged through the exhaust gas outlet 12 installed on the side wall of the reaction chamber 10a. In the reaction chamber 10a,
Several substrates 14 are mounted on a disc-like platform 13 which rotates about an axis that substantially coincides with the tube 11 so as to be able to rotate about each axis of rotation. [0008] In order to thermally decompose the gas, several rod-shaped tungsten lamps 15 are installed under the platform 13 so as to extend in parallel to each other. The rod-shaped tungsten lamp extends perpendicularly to the plane of the drawing of FIG. In use, the rod-shaped tungsten lamps 15 are driven independently, thereby creating a uniform temperature distribution within the reaction tube. [0009] L lamp, this conventional configuration is a rod lamp 1
There is a problem in that the temperature profile in the extension direction of 5 is not controlled. That is, even if the lamps are independently controlled, it is not possible with the apparatus of FIG. 1 to create a uniform temperature along the flow of gas in the reaction tube. [00101 Therefore, in order to equalize the temperature on the substrate, a complex configuration is used so that the table 13 rotates around the central axis and each substrate rotates around its own axis at the same time. Furthermore, the MOCVD apparatus shown in FIG. 4 has a problem in that when a disk-shaped table is used, the substrate 14 is placed laterally on the table, resulting in an increase in the size of the apparatus. In particular, this structure poses a serious problem when a large number of substrates 14 are desired to be placed on the stand 13 or when the size of the substrates 14 is large. That is, in this case, it is inevitable to increase the diameter of the pedestal 13, but if the diameter of the pedestal is increased, the dimensions of the MOCVD apparatus will become excessively large. [00111 FIG. 5 shows another prior art MOCVD apparatus 20 that uses a lamp heating fixture. This device is disclosed in Japanese Patent Application Laid-Open No. 59-36927. [0012] According to FIG. 5, this MOCVD apparatus consists of a Pelger-shaped container having a base 21 and a bell-shaped outer wall 22. Inside the outer wall 22, inner walls 23 are formed at regular intervals, and a plurality of ring-shaped tungsten lamps 29 are provided in the space between them. Each ring-shaped lamp 29 defines a substantially horizontally extending plane. The inner wall 23 defines a reaction chamber 23a, and the reaction chamber 23a
Gas is introduced therein via a tube 24 passing through the base 21. After the gas introduced in this way is thermally decomposed,
The exhaust gas is discharged via the exhaust gas outlet pipe 25. Further, the rotating shaft 26 extends to the reaction tube 23a via the base 21, and a disc-shaped stage 27 is installed at the tip of the shaft 26. Furthermore, the substrate 28
is fixed on the stand 27, and a compound semiconductor layer is formed thereon. [0013] During operation, the raw material gas of the reactant is guided to the reaction tube via the tube 24, and the tungsten lamp 2
9 is driven. At this time, each lamp 29 is controlled so that the internal lamp output on the radiation is small, while the output of the lamp located on the outside on the radiation is large, in order to compensate for the difference in heat dissipation rate in the substrate. Uniform heating of the substrate is thus achieved. [0014] However, with this conventional device, control of the gas temperature to obtain a uniform decomposition temperature and furthermore to form uniform crystals is not achieved. Since the cold gas guided into the Pelger-type chamber 23a flows along a complicated pattern,
It is extremely difficult to obtain a uniform gas temperature on the surface of the substrate 28 by controlling the tungsten lamp 29. [0015]Furthermore, similar to the problem in FIG. 4, in the apparatus of FIG. However, there is a problem in that the size of the device also increases. [0016] A compact MOCVD apparatus is desired that has the ability to control the temperature of the source gas flowing within the reaction tube along the substrate. [0017]

A more specific object of the present invention is to provide an MOCVD apparatus that forms a uniform semiconductor layer on a substrate by flowing a source gas in a reactor with a precisely controlled temperature profile. Another object of the present invention is to provide a compact MOCVD apparatus that forms a uniform semiconductor layer on a substrate by flowing source gases through a reactor at precisely controlled temperatures. [0018]

Means for Solving the Problems The present invention provides a base defined by an upper main surface; and an outer side extending upwardly from the base and forming a closed first space between the base and a container; formed to extend upward from the base to form a closed second space in the first space, having a shape corresponding to the outer container, and having a reaction space between the container and the outer container; an inner container defining a chamber; a gas inlet formed at the top of the outer container for introducing gas into the reaction chamber; a gas outlet corresponding to the reaction chamber formed in the base for evacuating the reaction chamber; A semiconductor manufacturing apparatus for growing a semiconductor layer on the substrate, which includes a susceptor provided on a container and holding a substrate, and the outer container and the inner container are configured to allow gas introduced from a gas inlet to reach the base. The susceptor holds the substrate surface substantially parallel to the gas flow in the reaction chamber, and a plurality of ring-shaped lamps are arranged in the second space. The lamps on the side closer to the gas inlet heat the upper part of the susceptor, but in a concentric relationship with each other and approximately parallel to the main surface of the base, but at different levels in the vertical direction. The lamps closer to the susceptor are arranged to heat the lower part of the susceptor, and the lamps in the middle are arranged to heat the middle part of the base. The above-mentioned problem is solved by a device characterized in that a control means is provided for independently controlling the lamps closer to the lamp to produce a larger output than the lamps in the middle. [0019]

In accordance with the present invention, the desired temperature profile necessary to produce a uniform substrate temperature is obtained by independently controlling each lamp. Furthermore, the size or number of substrates on which compound semiconductor devices are epitaxially grown can be more easily increased by increasing the height of the MOCVD apparatus. Therefore, an undesirable increase in the device size in the lateral direction can be avoided. Other objects and features of the invention will become apparent from the detailed description below. [00201

[Embodiment] FIG. 1 shows an embodiment of the MOCVD apparatus according to the present invention. [0021] In the figures, an MO designated generally as apparatus 30
The CVD apparatus has a base 31 of quartz or stainless steel and a Pelger type outer container 32. The outer container 32 is 50
It has a height H of 60 cm and a circular cross section when viewed in plan. The outer container 32 is provided with an inner container 33 having a shape corresponding to the outer container 32 and made of quartz and having a Pelger shape. [0022] A reaction chamber is formed between the inner chamber 32 and the outer chamber 31, and a source gas is introduced from the top of the outer chamber 31. The gas thus introduced into the reaction chamber flows downward along the side of the inner container 32 and is discharged from the waste gas outlet 39. [0023] A plurality of carbon susceptors 34 are installed on the surface of the inner container 33 on the side facing the reaction chamber so as to surround the container 33 in a circular shape on a horizontal plane, and each susceptor 34
A substrate 35 on which a semiconductor layer is to be formed by CVD is held. The diameter of the inner container 33 gradually increases from the top to the bottom, and the diameter is about 40 to 50 cm at the bottom.
becomes the size of [0024] The susceptor 35 is typically 3 inches in size and holds the semiconductor substrate so that its surface is substantially parallel to the general direction of gas flow within the reaction tube. Preventing the generation of vortices in the reaction tube and connecting the base 31 from the inlet.
In order to further ensure a stable unidirectional flow of gas to the outlet 39, the spacing d between the outer chamber 32 and the inner vessel 33 is preferably set to about 5 cm or less. In the space formed inside the inner container 33, a plurality of ring-shaped tungsten lamps 36 are placed so that each lamp is positioned on a horizontal plane, and one lamp is positioned above the other lamp, and a susceptor is placed on top of the susceptor. 34. That is, the bottom lamp heats the bottom of the susceptor 34, while the top lamp heats the top of the susceptor 34. Further, each lamp 36 is independently controlled by a temperature controller. [0025] A thermocouple TC is embedded in the susceptor 34 to monitor the temperature within the susceptor. [0026] Next, an example of epitaxial growth of a semiconductor layer on the substrate 23 will be described. In the example below, AlG
An aAs layer is formed on a GaAs substrate 35 with a controlled doping level. [0027] In this example, the hydrogen carrier gas flows from the top of the outer vessel to the outer vessel 32 for 10 minutes.
It flows downward at a flow rate of 0.01/min. Furthermore, arsine gas containing 18% arsine in hydrogen is 21/m
in, flow rate. In addition to arsine, 100cc each of trimethylgallium and trimethylaluminum
It is supplied at a flow rate of 30 cc/min and 30 cc/min. The capacity of trimethylaluminum is transferred to 20°C, whereas the capacity of trimethylgallium is maintained at 0°C. Furthermore, diluted silane gas contained in hydrogen at a concentration of 20 ppm is introduced as a dopant at a flow rate of 20 cc/min. The growth temperature is 64°C at the center of the susceptor 34.
The temperature was set at 0°C. The susceptor 34 is 25c in the gas flow direction.
m size, and fixes a 3-inch board. Each ring lamp 36 is rated at 200 Bordeaux 12 amperes, and eight lamps are arranged vertically at 25 mm intervals. The tube diameter of the lamp is 1-2 cm. Each lamp 36 heats the GaAs substrate 35 on the carbon susceptor 34 under the control of a controller (not shown), and in response to the heating, the raw material gas is thermally decomposed on the substrate surface to achieve the desired deposition of the AlGaAs layer. . Board 3
The temperature of 5 is controlled by the output voltage of a thermoelectric body embedded in the substrate 34, and a uniform temperature distribution on the substrate is achieved by independently controlling the power of the lamps 36. FIG. 2 shows a control system of the MOCVD apparatus of FIG. According to FIG. 2, the susceptor 34 is similar to the thermoelectric body TC.
A plurality of thermoelectric bodies TC1, TC2, ..., embedded in
The output of is supplied to the control unit 41. The thermoelectric body corresponds to the output, and the control unit 41
A lamp drive profile E stored in the memory 42 is read out in correspondence with a desired combination of temperature and flow rate of each raw material gas. The profile E is defined such that the gas is heated more intensively upstream than corresponding to the central portion of the substrate 35 such that epitaxial layer growth is achieved on the substrate 35 at a substantially uniform temperature. be done. Of course, such non-uniform heating may result in non-uniform temperature supply in the susceptor 34, but the purpose of the present invention is to provide a uniform temperature for epitaxial crystal growth.
A uniform susceptor temperature profile is not intended. [0028] FIG. 3(A) shows Al grown on the substrate 35.
It shows the uniformity of the properties of the GaAs layer and the power control of the lamps used. In this experiment, the properties of the epitaxial layer were evaluated by measuring the electron concentration that corresponds to the proportion of activated dopants in the semiconductor layer. Such activation occurs through the incorporation of dopant atoms into the crystal lattice locations of the epitaxial layer and is strongly influenced by temperature. For example, when AlGaAs layers are grown at low temperatures, the majority of dopant atoms remain interstitial, and only a relatively small percentage of dopant atoms enter a given crystal lattice position. Such inert dopants do not release carriers and therefore the AlGaAs layer does not exhibit desirable electrical properties. [0029] Such a problem of insufficient activation of dopant atoms tends to occur upstream of the substrate 35 where the gas temperature is relatively low. As shown in FIG. 3A, the present invention solves this problem by controlling the output of the lamps in the upstream portion to be higher than the lamps that heat the central portion of the substrate 35. In Figure 3(A), the right vertical axis indicates the output power of the lamp. It has also been shown that satisfactory results can be obtained if the output power of the lamp is increased downstream. [00301 Figure 3(A) shows the electron concentration on the left vertical axis. This shows that a uniform electron concentration can be obtained by controlling the lamp output profile in this way. As can be seen from this figure, the AIGaA grown in this way
The electron concentration of the S layer is substantially uniform throughout the surface of the substrate. Changes in electron concentration on the wafer 35 are suppressed to ±2% or less. [0031] On the other hand, FIG. 3(B) shows a case in which the output power of the lamp 36 is uniformly controlled in a negative manner. [0032] This case corresponds to conventional MOCVD equipment that does not have the ability to independently control lamp output. As can be seen from the drawing, the electron concentration is low on the upstream side, and gradually increases toward the downstream side as the gas temperature rises. The change in electron concentration reaches approximately ±8%. Therefore, unsatisfactory results are obtained from such devices. [0033] [Effects of the Invention] According to the present invention, a plurality of ring-shaped heaters are provided along the gas flow that spreads radially from the top to the bottom, and each heater is placed on the outside, and the heater on the upstream side is placed on the outside. By controlling the heating to be strong, the concentration of the introduced gas can be made uniform, and it becomes possible to grow a semiconductor layer with similar characteristics on the substrate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of MOCVD and an apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a control system of the MOCVD apparatus of FIG. 1;

[Figure 31 (A) and (B) show the present invention (7) MOC
2 is a graph showing a comparison of temperature profiles and electron concentration levels obtained in semiconductor layer formation using a VD device and a conventional MOCVD device. FIG. 4 is a cross-sectional view showing the structure of a conventional MOCVD apparatus.

FIG. 5 is a sectional view showing another conventional MOCVD apparatus.

[Explanation of symbols]

10 Reactor 10a Reaction chamber 11 tubes 12 Exhaust gas outlet 13 units 14 Board 15 Lamp 20 MOCVD equipment 21 Base 22 Exterior wall 23 Exterior wall 23a Reaction chamber 24 tubes 25 Exit 26 axes 27 units 28 Substrate 29 Lamp 30 MOCVD equipment 31 Base 32 Outer container 33 Inner container 34 Susceptor 35 Board 36 Lamp 39 Exit TC thermocouple

[Figure 4]

[Figure 5]

[Figure 1]

[Figure 2]

[Figure 3] Continuation of front page

Claims (1)

[Claims] 1. A base (31) having an upper main surface; an outer container (32) extending upward from the base and forming a closed first space between it and the base; An inner side is formed to extend upward from the base to form a closed second space in the first space, has a shape corresponding to the outer container, and defines a reaction chamber between the outer container and the second space. a container (33); a gas inlet formed at the top of the outer container to introduce gas into the reaction chamber; a gas outlet formed in the base corresponding to the reaction chamber to exhaust gas from the reaction chamber; A semiconductor manufacturing apparatus for growing a semiconductor layer on the substrate, which includes a susceptor (34) provided on an inner container and holding a substrate, and the outer container and the inner container are connected to a susceptor (34) that holds a substrate. The susceptor is configured such that the gas flows in approximately one direction toward the base, the susceptor holds the substrate surface so that it is approximately parallel to the gas flow in the reaction chamber, and the second space has a plurality of ring-shaped lamps are provided in a concentric relationship with each other and substantially parallel to the main surface of the base, and at different levels in the vertical direction, and each of the plurality of ring-shaped lamps is provided independently. 1. A device characterized in that it is provided with a control means for controlling.