JP3880096B2 - Vapor growth method - Google Patents

Description

なお、希釈ガスの流量バランスは、８０００ｓｃｃｍ／１２０００ｓｃｃｍ＝０．６７である。また、ｓｃｃｍは、「Ｓｔａｎｄａｒｄ Ｃｕｂｉｃ Ｃｅｎｔｉｍｅｔｅｒ／ｍｉｎ」の略記である。
【００３９】
【発明の効果】
以上説明したように、本発明によれば、二成分系以上の化合物半導体薄膜を効率よく生産することができ、複雑な多層構造のデバイス用薄膜の最適化も容易となる。また、有害堆積物の減少により反応管の清掃頻度が減少して生産性が向上する。
【図面の簡単な説明】
【図１】 本発明の方法に用いる気相成長装置の一例を示す正面断面図である。
【図２】 同じく側面断面図である。
【図３】 希釈ガス流量バランスと、縦軸が膜厚均一性及びドーピング均一性を示す図である。
【図４】 従来の気相成長装置の一例を示す正面断面図である。
【符号の説明】
１１…ガス導入部、１２…ガス排出管、１３…反応管、１４…基板、１５…サセプタ、１６…フローチャンネル、１７，１８…仕切板、１９…成長促進台、２０…ＲＦコイル、２１…第一流路、２２…第二流路、２３…第三流路、２４…第一気相成長ガス導入管、２５…第二気相成長ガス導入管、２６…成長促進ガス導入管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vapor phase rectangular method, particularly, in parallel with the heated substrate surface flowed vapor phase growth gas, the horizontal to obtain a deposition substrate formed with the compound semiconductor thin film of two or more component to the substrate surface vapor-phase rectangular Law on.
[0002]
[Prior art]
For example, an apparatus described in Japanese Patent Publication No. 7-27868 is known as a horizontal vapor phase growth apparatus that introduces a source gas into a reaction tube provided with a substrate to form a compound semiconductor thin film on the substrate surface.
[0003]
As shown in FIG. 4, the vapor phase growth apparatus described in the above publication is provided with a holding table (susceptor) 3 that holds a substrate 2 inside a cylindrical reaction tube 1 installed with an axis line in a horizontal direction. A gas introduction part 4 is provided at one end, and a gas discharge pipe 5 is provided at the other end, and a partition plate 6 parallel to the substrate surface is installed upstream from the substrate 2, and two parallel flow paths, that is, substrates, are provided above and below the partition plate 6. The lower flow path 7 on the side and the upper flow path 8 on the side opposite to the substrate are partitioned, and a flow channel 9 is provided on the upstream side of the susceptor 3 for smooth gas flow. An RF coil 10 for heating is arranged in the above.
[0004]
The vapor phase growth apparatus introduces a vapor phase growth gas obtained by diluting a raw material gas with a dilution gas into the upper flow path 8 while the substrate 2 is placed on the susceptor 3 and heated by the RF coil 10. Vapor growth is performed by introducing an intervening gas that does not contain source gas into the lower flow path 7. As the intervening gas, the same gas as the dilution gas in the vapor phase growth gas or a gas in which a small amount of volatilization suppression gas is added is used.
[0005]
The vapor phase growth gas and the intervening gas separately flow in the upper flow path 8 and the lower flow path 7 in parallel with each other, flow toward the substrate 2 after passing the substrate side end of the partition plate 6, and gas Due to the mutual diffusion action, the source gas in the vapor phase growth gas diffuses into the intervening gas, and approaches the surface of the substrate 2 while gradually increasing the concentration of the source gas in the intervening gas. The source gas in the intervening gas is thermally decomposed at a high temperature portion near the substrate 2 and deposited on the substrate surface to form a growth film.
[0006]
At this time, by appropriately adjusting the flow rates of the intervening gas and the vapor phase growth gas and the source gas concentration in the vapor phase growth gas, the amount of the source gas diffused from the vapor phase growth gas into the intervening gas and the substrate surface The amount of source gas that disappears from the intervening gas due to the deposition can be balanced per unit time, and the concentration of the source gas in the intervening gas when passing through the substrate surface is a uniform growth distribution with a uniform thickness distribution in the flow direction. Can be formed.
[0007]
In this way, the horizontal vapor phase growth apparatus is provided with the partition plate 6 and separately introduces the vapor growth gas and the intervening gas as a two-layer flow, and diffuses the source gas in the vapor growth gas into the intervening gas. By reaching the substrate surface, a film-formed substrate with a uniform film thickness can be obtained, and the presence of the intervening gas reduces the amount of harmful deposits on the substrate other than the substrate because it flows over the substrate surface with a low source gas concentration. Can be made.
[0008]
[Problems to be solved by the invention]
However, when a growth film of two or more components is formed by the conventional horizontal vapor phase growth apparatus, a highly volatile element out of a plurality of types of component elements may evaporate from the growth film and cause a defect in the growth film. is there. In order to prevent the occurrence of this defect, conventionally, measures have been taken such as supplying a source gas (volatile gas) containing a highly volatile element in excess of the equilibrium partial pressure of the volatile gas. The cost has increased due to a decrease in the utilization efficiency of raw materials.
[0009]
In addition, in order to deposit a desired reaction product on the substrate surface, it is necessary to adjust the gas flow rate to an optimum state. However, the gas flow rate adjustment is necessary for the raw material utilization efficiency and the device manufacturing process. Subtle adjustments including the point of impurity doping etc. are necessary, and the conventional horizontal type vapor phase growth apparatus manufactures a thin film for a device having a complicated structure while simultaneously satisfying the film thickness, composition and uniformity of doping. It was difficult.
[0010]
In other words, conventionally, the raw material gas concentration was adjusted to prevent volatilization of volatile components, or the gas flow rate was adjusted to match the reaction product deposition zone on the substrate surface. There are cases where the conditions for obtaining the optimum conditions for the source gas concentration do not necessarily match the conditions for obtaining good film forming characteristics. In addition, since the optimum conditions for the gas flow rate at which film thickness uniformity and doping uniformity are obtained may not match, the method of adjusting the gas flow rate is suitable for thin film growth of complex multilayer structures such as for devices. It wasn't.
[0011]
Furthermore, in the conventional apparatus, since the thermal decomposition products and the like are deposited around the substrate, it is necessary to frequently clean the reaction tube.
[0012]
The present invention can form a less favorable two-component systems or more of the compound semiconductor multilayer film defects, the utilization efficiency of the raw material gas is high, provides a rectangular method Phase Ingredients feel can enhance productivity The purpose is that.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the vapor phase growth method of the present invention includes two partition plates arranged in parallel to the substrate surface upstream of the substrate in a reaction tube in which the substrate is installed. The upstream portion in the reaction tube up to the vicinity of the substrate is partitioned from the substrate side into three layers of parallel flow channels, a first flow channel, a second flow channel, and a third flow channel, and the first gas phase is formed in the first flow channel. A growth gas introduction pipe, a second vapor phase growth gas introduction pipe in the second flow path, and a growth promoting gas introduction pipe in the third flow path are connected to each other, and at least two kinds of source gases are supplied from the gas introduction portion to the substrate. forming said raw material gas is heated reaction the reaction product is deposited on the substrate surface, the compound semiconductor thin film of two or more component on the substrate surface on introducing the substrate surface in a direction parallel to the plane in the vapor phase growth method using a vapor deposition apparatus for the compartment formed on the upstream side of the substrate Of the flow path of the substrate surface and parallel to three layers, the first vapor deposition gas diluted by the dilution gas volatile material gas to the first channels of the substrate, sparingly volatile material gas follows the second flow path When introducing the second vapor phase growth gas diluted with the dilution gas and the growth promoting gas not containing the source gas into the third flow path farthest from the substrate, the entire flow rate of the dilution gas is kept constant. The flow rate ratio between the dilution gas in the first vapor phase growth gas and the dilution gas in the second vapor phase growth gas is adjusted.
[0014]
Further, vapor deposition method of the present invention, before Symbol growth promoting gas, the diffusion coefficient for the raw material gas may be used less gas than diluent gas.
[0015]
The compound semiconductor thin film of two or more components in the present invention is a III-V group compound semiconductor, a II-VI group compound semiconductor thin film, etc., for example, a two-component film formation such as GaAs (gallium arsenide), Ga In addition, a ternary film formation of GaInAs or the like in which a part of is replaced with In (indium), and a multicomponent film formation including P (phosphorus) or the like can be given.
[0016]
The vapor phase growth gas is a gas obtained by diluting a source gas with a diluent gas composed of an inert gas such as hydrogen, helium, argon, nitrogen, etc., and the source gas is an individual component gas that contributes to the vapor phase growth reaction. For example, it is a kind of silane, arsine, phosphine, trimethylgallium (TMG) vapor, or a mixture thereof. For example, when the GaAs film is formed on a GaAs substrate, vapor phase growth gas is used in which TMG vapor is used as the gallium source gas, arsine is used as the As source material, and these source materials are diluted with hydrogen.
[0017]
In addition, the source gas can be classified into a volatile source gas that is easily volatilized by heat and a hardly volatile source gas that is less likely to volatilize by heat. Steam becomes a hardly volatile source gas.
[0018]
On the other hand, the growth promoting gas is an inert gas that does not contribute to the vapor phase growth reaction. For example, hydrogen, helium, argon, nitrogen, or the like can be used, and the same gas as the dilution gas is used. However, it is preferable to use a gas whose diffusion coefficient with respect to the source gas is smaller than that of the dilution gas, or to supply in a state in which it is difficult to diffuse by adjusting the flow rate, etc., and requires hydrogen, argon, nitrogen, etc. Depending on the situation, a mixture of two or more may be used.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings. 1 and 2 show an example of a vapor phase growth apparatus used in the method of the present invention, which has a gas introduction part 11 at one end and a gas discharge pipe 12 at the other end, and the axis is in a horizontal direction. Inside the installed cylindrical reaction tube 13, a susceptor 15 that holds the substrate 14, a flow channel 16 on the upstream side of the susceptor 15, and two partition plates 17 on the gas introduction section 11 side upstream of the susceptor 15. , 18 and a growth promoting table 19 facing the susceptor 15. An RF coil 20 for heating the substrate 14 via a susceptor 15 is provided on the outer periphery of the reaction tube 13.
[0020]
The two partition plates 17 and 18 are in the form of a thin plate installed in parallel with the substrate surface, and the upstream portion in the reaction tube 13 from the gas introduction part 11 to the vicinity of the substrate 14 is disposed on the substrate side. The first flow path 21, the intermediate second flow path 22, and the third flow path 23 on the opposite side of the substrate 14 are partitioned, and three parallel flow paths are defined in the reaction tube 13. .
[0021]
In the gas introduction part 11, each of the flow paths has a first vapor phase growth gas introduction pipe 24 in the first flow path 21, a second vapor growth gas introduction pipe 25 in the second flow path 22, and a third flow path 23. A growth promoting gas introduction pipe 26 is connected to each of the first flow path 21, the first vapor growth gas in the first flow path 21, the second vapor growth gas in the second flow path 22, and the third flow path 23. The growth promoting gas is introduced respectively.
[0022]
The growth promoting base 19 is provided to reduce the cross-sectional area of the gas flow path in the reaction tube 13 in the substrate 14 portion, and is provided in a portion facing the substrate 14 in the reaction tube 13. The upstream side is formed as an inclined surface that gradually increases in height, and the surface facing the substrate 14 is formed in parallel with the substrate surface.
[0023]
In order to form a compound semiconductor thin film of two or more components with the vapor phase growth apparatus formed in this way, first, the substrate 14 is held by the susceptor 15 and heated to a predetermined temperature by the RF coil 20, and then the first flow path is formed. A first vapor growth gas is introduced into 21, a second vapor growth gas is introduced into the second flow path 22, and a growth promoting gas is introduced into the third flow path 23.
[0024]
The first vapor phase growth gas, the second vapor phase growth gas, and the growth promoting gas introduced into the reaction tube 13 separately flow through the respective flow paths, past the end portions of the partition plates 17 and 18. Thereafter, the source gases in the first vapor phase growth gas and the second vapor phase growth gas flow toward the substrate 14 while diffusing each other.
[0025]
At this time, the raw material gas in the first vapor phase growth gas flowing through the first flow path 21 close to the substrate surface is used as a volatile raw material gas, and the raw material gas in the second vapor phase growth gas in the second flow path 22 is hardly volatile. By using the source gas, the concentration of the volatile source gas in the gas in the vicinity of the substrate can be increased, so that the source gas can be efficiently decomposed and deposited on the substrate surface, and its utilization efficiency is greatly increased. In addition, it is possible to prevent volatilization of volatile elements from the growth film, so that a growth film with a low defect rate can be obtained. Furthermore, compared with the case where volatile source gas is introduced into the entire reaction tube, the concentration in the vicinity of the substrate can be made the same or higher with a small amount, so that the amount of source gas used can be greatly reduced.
[0026]
In addition, the hardly volatile source gas in the second vapor growth gas flowing through the second flow path 22 approaches the substrate surface while gradually diffusing into the first vapor growth gas, and passes through the substrate surface. Due to the interdiffusion action, the hardly volatile source gas in the second vapor phase growth gas subsequently diffuses and penetrates into the first vapor phase growth gas, and the hardly volatile source gas in the first vapor phase growth gas becomes the reaction product. Then, one after another is deposited on the substrate surface.
[0027]
Then, by optimally balancing the amount of diffusion of the hardly volatile source gas into the first vapor phase growth gas and the amount lost from the first vapor phase growth gas as a reaction product, Not only can the source gas concentration when passing through the surface be a uniform concentration distribution in the flow direction to obtain a good deposition substrate with a uniform thickness, but also the hardly volatile source gas gradually enters the first vapor phase growth gas. The distance of the complete mixing area (diffusion mixing area) so that it can be diffused and decomposed and deposited can be adjusted, so the deposition position of the reaction product can be controlled, and harmful deposits other than the substrate can be greatly reduced. It becomes possible.
[0028]
The adjustment of the diffusion and mixing region of the hardly volatile source gas can be performed by adjusting the flow rate balance between the dilution gas in the first vapor phase growth gas and the dilution gas in the second vapor phase growth gas. For example, as is apparent from FIG. 3 showing the experimental results described later, in the first vapor phase growth gas with respect to the flow rate of the dilution gas in the second vapor phase growth gas, the entire amount of the dilution gas flowing through the reaction tube 13 is made constant. When the flow rate of the dilution gas is changed, film thickness uniformity (indicated by white circles in the figure) and doping uniformity (indicated by black circles in the figure) change. That is, in this case, it can be understood that the film thickness uniformity is lowered even if the flow rate balance of the dilution gas is reduced or increased from a specific range, and an optimum flow rate balance exists.
[0029]
Furthermore, in adjusting the flow rate balance, it is possible to change the flow rate of one dilution gas while changing the flow rate of the other dilution gas, but in this case, the total gas flow rate of the substrate portion in the reaction tube Since the (flow velocity) changes, complicated adjustment operations are required. Thus, without changing the total amount of the dilution gas, i.e., without changing the overall gas flow in the reaction tube, adjust the flow rate of both the diluent gas. For example, the ratio of the case where the entire diluted gas flow rate is 20, the flow rate of the dilution gas in the first vapor deposition in a gas (A) and the dilution gas flow rate of the second vapor deposition gas (B), A: B = 9: 11 (flow rate balance = 0.82), 10:10 (equal amount), or 11: 9 may be changed.
[0030]
Note that the optimum flow rate balance is the cross-sectional area of each flow path, the distance between each partition plate end and the substrate, the size of the reaction tube, which is related to the concentration and flow rate of the hardly volatile source gas in the second vapor phase growth gas. What is necessary is just to set suitably according to the whole gas amount.
[0031]
Furthermore, even when the optimum conditions for the gas flow rate at which the film thickness uniformity and doping uniformity on the substrate surface are obtained are different, the reaction on the substrate surface can be achieved at a constant optimum gas flow rate by adjusting the flow rate balance of the dilution gas. The product can be deposited uniformly, and optimization of a thin film for a device having a multilayer structure having a complicated structure is facilitated.
[0032]
On the other hand, as the growth promoting gas introduced into the third flow path 23, a gas having a smaller diffusion coefficient with respect to the source gas than the dilution gas used for both vapor phase growth gases is used. Can be prevented from diffusing into the growth promoting gas and reducing the concentration of the raw material gas in the vapor phase growth gas, the amount of the raw material gas discharged together with the growth promoting gas can be reduced, and the utilization efficiency of the raw material is greatly increased. be able to.
[0033]
Further, even when the hardly volatile source gas in the second flow path 22 diffuses into the growth promoting gas in the third flow path 23, the diffusion coefficient is adjusted using the growth promoting gas as a mixed gas, or the flow rate of the growth promoting gas It is possible to suppress the diffusion of the raw material gas into the growth promoting gas and to control the deposition zone of the hardly volatile raw material gas.
[0034]
Further, by providing a growth promoting base 19 in the reaction tube 13 to reduce the gas flow path cross-sectional area in the vicinity of the substrate surface, the gas flowing in the reaction tube 13 is pressed against the substrate surface, and the gas flow rate in this portion is increased. Therefore, the thickness of the velocity boundary layer in the gas flowing on the substrate surface and the temperature boundary layer having a large temperature gradient in the vicinity of the substrate can be reduced by appropriately setting the shape of the growth promotion table 19. It is possible to control the volatile source gas, which was difficult to crystallize, to be optimally decomposed and crystallized, and to increase the effective source concentration in the vicinity of the substrate. Therefore, the film can be efficiently formed in a better state. Instead of providing the growth promotion table 19, the shape of the reaction tube 13 itself may be formed in the same shape as the growth promotion table 19 is provided. Further, in this example, the apparatus having a structure for holding the substrate 14 toward the film formation surface above the reaction tube 13 is illustrated, but the substrate may be installed below the reaction tube as in the conventional case. Good.
[0035]
【Example】
Next, examples of the present invention will be described.
An experiment for forming a GaAs film on a GaAs substrate using the apparatus having the structure shown in FIGS. 1 and 2 was performed under the following conditions. A gas obtained by diluting arsine as a volatile source gas and silane as a doping gas with hydrogen is introduced into the first channel, and trimethylgallium (TMG) as a hardly volatile gas is hydrogenated into the second channel. The gas diluted with 1 was introduced, and hydrogen was introduced into the third channel as a growth promoting gas. The concentration of silane in the doping gas was 10 ppm.
[0036]
FIG. 3 shows the relationship between the dilution gas flow rate balance when the GaAs film is formed on the 3-inch GaAs substrate, the film thickness uniformity within the substrate surface, and the Si doping uniformity, and the horizontal axis represents the dilution gas flow rate balance. [-], The vertical axis represents film thickness uniformity [%] and Si doping uniformity [%]. The film thickness is a result of spectroscopic ellipsometry, and the Si doping amount is a result of measuring the carrier concentration with a profile plotter.
[0037]
From this result, the film thickness uniformity decreases as the dilution gas flow rate balance is increased, that is, the dilution gas flow rate in the first vapor phase growth gas of the first flow path is increased. Can be seen to grow again. In addition, it can be seen that the doping uniformity is consistent with the optimal dilution gas flow rate balance condition that provides film thickness uniformity. Therefore, when film formation was performed under the following conditions, a uniform and good GaAs film could be obtained.
[0038]

The flow rate balance of the dilution gas is 8000 sccm / 12000 sccm = 0.67. Also, sccm is an abbreviation for “Standard Cubic Centimeter / min”.
[0039]
【The invention's effect】
As described above, according to the present invention, a compound semiconductor thin film having two or more components can be efficiently produced, and optimization of a thin film for a device having a complex multilayer structure is facilitated. In addition, the frequency of cleaning the reaction tube is reduced due to the reduction of harmful deposits, thereby improving productivity.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing an example of a vapor phase growth apparatus used in a method of the present invention.
FIG. 2 is a side sectional view of the same.
FIG. 3 is a diagram showing a dilution gas flow rate balance and a vertical axis showing film thickness uniformity and doping uniformity.
FIG. 4 is a front sectional view showing an example of a conventional vapor phase growth apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Gas introduction part, 12 ... Gas exhaust pipe, 13 ... Reaction tube, 14 ... Substrate, 15 ... Susceptor, 16 ... Flow channel, 17, 18 ... Partition plate, 19 ... Growth promotion stand, 20 ... RF coil, 21 ... 1st flow path, 22 ... 2nd flow path, 23 ... 3rd flow path, 24 ... 1st vapor phase growth gas introduction pipe, 25 ... 2nd vapor growth gas introduction pipe, 26 ... growth promotion gas introduction pipe

Claims (2)

In the reaction tube in which the substrate is installed , two partition plates are arranged upstream of the substrate in parallel with the substrate surface, and the upstream portion in the reaction tube from the gas introduction part to the vicinity of the substrate is arranged from the substrate side. The flow path is divided into three parallel flow paths, one flow path, a second flow path, and a third flow path, and the first vapor growth gas introduction pipe is provided in the first flow path, and the second vapor growth is performed in the second flow path. the gas inlet tube, respectively continuously arranged a growth promoting gas introduction pipe to the third flow path, at least two kinds of the raw material gas on the substrate surface is introduced into a direction parallel to the substrate surface from the gas inlet portion In the vapor phase growth method using the vapor phase growth apparatus, wherein the source gas is heated and reacted to deposit a reaction product on the substrate surface, and a compound semiconductor thin film of two or more components is formed on the substrate surface. of the more upstream parallel to the substrate surface 3 layer was partitioned and formed on the side of the flow channel, first flow on the substrate side The first vapor phase growth gas obtained by diluting the volatile source gas with the dilution gas is separated from the substrate by the second vapor phase growth gas obtained by diluting the non-volatile source gas with the dilution gas in the next second flow path. When introducing the growth promoting gas that does not contain the source gas into the third flow path, the entire flow rate of the dilution gas is kept constant, the dilution gas in the first vapor phase growth gas, and the second gas A vapor phase growth method characterized by adjusting a flow rate ratio with a dilution gas in a phase growth gas. 2. The vapor phase growth method according to claim 1 , wherein the growth promoting gas is a gas having a diffusion coefficient smaller than that of the dilution gas with respect to the source gas .

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