JPS6064429A - Oxidizing and diffusing device - Google Patents

Abstract

PURPOSE:To prevent the intrusion of a contaminate, and to improve the controllability of the distribution of the thickness of a film by forming a cap section for a reaction tube in double tube structure and setting the pressure of the internal space of an external cap section at pressure higher than pressure in a reaction chamber for the reaction tube. CONSTITUTION:An external cap section 21 made of quartz glass is mounted in a shape that the outside section of a cap 14 section for a reaction tube 11 is covered under a sealed state through a proper space. The section 21 consists of a cap proper 22 and an external cap 23. The pressure PA' of an internal space 21a is kept at pressure slightly higher than atmospheric pressure PA. Pressure PR in a reaction chamber 11a is kept at pressure slightly lower than pressure PA' in the space 21a. Accordingly, an oxide film formed on a wafer 15 is not contaminated, and the excellent film is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field of the invention The present invention relates to a vaporization diffusion device, and particularly relates to a silicon IC (
This invention relates to the structure of an apparatus that forms a thin oxide film on the surface of a sample such as an integrated circuit (integrated circuit) substrate by branching or diffusion.

(b) Background of the technology For example, in the manufacturing process of silicon ICs, silicon (
The process of forming a thin oxide film (St(h) on the St) substrate has a large influence on the function of the IC, so it is a very expensive process. Oxidation diffusion devices are often used.

This type of oxide film is particularly notable for its good quality, non-contamination, and uniformity in thickness and depth. Nowadays,
As IC patterns tend to become increasingly finer, there is a need to make the thickness of the single wave film even thinner.

For example, the gate oxide film of a MOS-IC needs to be formed very thinly, and is particularly required to be uncontaminated, clean, and of good quality, and to have a uniform thickness and distribution. As for the thickness of this oxidation film, for example, a very thin oxide film of about 100A is required outside of VLSIs of about 1 megabit.

Therefore, as an oxidation diffusion device for this yuzu, we have created a structure that can minimize contamination and form a clean, high-quality oxide film with a uniform thickness distribution, even with a very thin oxide film such as a double layer. What we have is in demand.

(c) Prior Art and Problems FIG. 1 is a diagram for explaining a conventional oxidation diffusion device. In the figure, reference numeral 10 indicates the entire apparatus, 11 is a reaction tube made of quartz glass, 11a is a reaction chamber, and 12 is a quartz glass tube integrally connected to the reaction tube in communication with the reaction chamber 11a. 13 is an outflow boat for exhaust gas G2 formed in the same manner as inlet port 12, 14 is a cap made of quartz glass, and 15 is a disk-shaped wafer (a large number of ICs). (silicon substrate containing chips), 16 is a plurality of chips - 1
17 is a heater for heating the wafer 15, PA is atmospheric pressure (760xH5l), p
R represents the pressure inside the reaction chamber 11a. cap 1
4 has a common sliding joint 8 and is tightly fitted to the reaction tube 11 through the joint 18 in a removable manner. Then, the cap 14 is removed and the wafer 15 is taken in and taken out. The wafer 15 is heated to a high temperature of about 1000° C. to 1100° C. by the heater 17.

When a reaction gas Gt (for example, 02 gas) is fed into the reaction chamber 11a from the inflow port 12, a reaction occurs on the a-side of the wafer (silicon base &) 15 heated to a high temperature, and a Stow acclimation film is formed on the surface. is formed.

In this case, an oxide film is formed by so-called thermal oxidation. The exhaust gas G after the reaction is then exhausted into the atmosphere from the outflow boat 13. Therefore, in this case, the reaction chamber 11
The pressure inside a is slightly higher than the atmospheric pressure PA, or is almost at a value close to the rotational pressure, and is maintained in a state of PR≧PA. However, the pressure PR is often slightly higher than the atmospheric pressure PA by the output of the reservoir into which the reaction gas G is pumped. Although the joint portion 18 is formed by a co-sliding process, the reaction tube 11 and the cap 14 are almost tightly joined together, but there is a possibility that some leakage may occur due to the pressure difference between the inside and outside. Therefore, in this case, since there is a relationship of PR≧PA, intrusion of outside air from the joint portion 18 into the reaction chamber 11a is prevented, and a clean and high-quality oxide film can be formed.

However, the oxide film at this pole does not grow by reacting with the silicon itself, so when the film is thin, the oxidation reaction is fast (the film grows quickly), but as the film becomes thicker, it gradually slows down. It has characteristics. Also, on the other hand,
The speed of the oxidation reaction is determined by the temperature of the wafer 15 and the pressure PR in the reaction chamber 11a. That is, assuming that the temperature tube of the wafer 15 is constant, the film growth speed becomes slower as the pressure PR becomes lower. This conventional device 1
In the case of 0, the pressure PR in the reaction chamber 11a is almost the same as the atmospheric pressure PA and is relatively high, so that the film has a function of increasing the growth speed when the film is thin on the back. Therefore, when forming a normal oxide film, the conventional device 10 can obtain a good quality film, but the film is very thin (for example, the thickness is is 100
When forming a film with a thickness of about There is a problem of lack of controllability. Therefore, in order to solve this problem, in order to slow down the growth speed of the film, we set the state PR<PA, and this time, the atmosphere flows from the joint 18 to the reaction chamber 1.
1 a l'J, moisture, nitrogen, etc. in the atmosphere react with the reaction gas G1 and contaminate the oxide film, making it impossible to obtain a good quality I-containing film.

Further, in forming such a thin oxide film, it is conceivable to use a conventionally known reduced pressure vapor deposition apparatus (CVD apparatus). This CVD apparatus maintains the pressure (PR) inside the reaction tube at a pressure slightly lower than atmospheric pressure (PA) (for example, about 1 to 10 #711 (f)), so it has the advantage of slowing down the film growth speed. However, there is a metal (often stainless steel) cap part (a part for loading and unloading wafers) called a manifold connected to the reaction tube. When forming an oxide film with strict requirements, it is important that the pot metal in the cap part be exposed to high temperatures, and contamination from this gold AIts (proboscis) may contaminate the film and prevent a good oxide film from being formed. I can't.

B) Purpose of the Invention In view of the problems of the prior art described above, the purpose of the present invention is to slow down the reaction speed of the oxide film, easily prevent the intrusion of impurities, and reduce the thickness of even an extremely thin film. It is an object of the present invention to provide an oxidation diffusion device capable of uniformly distributing a predetermined value and forming a high-quality film that is not contaminated.

(E) Structure of the invention In order to achieve this object, according to the present invention,
In the oxidation diffusion apparatus, the reaction tube is provided with a reaction tube which forms a reaction chamber for accommodating a sample on which a film is to be formed on the bottom surface, and has a reaction gas inflow boat and a bleed gas outflow boat communicating with the reaction chamber. An outer cap part is integrally connected to the reaction tube and is formed in a shape that seals the outer part of the cap part of the tube through an appropriate space and connects an inflow boat and an outflow boat for the reaction gas. The oxidation method is characterized in that the cap portion of the reaction tube is formed into a 2M tube structure, and the pressure in the internal space of the outer cap portion is controlled to be higher than the pressure inside the reaction chamber. A diffusion device is provided.

(f) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

The second south is a diagram for explaining the oxidation diffusion device 4 of the present invention. In this figure, the same or equivalent parts as those in FIG. 1 mentioned above are designated by the same reference numerals. Therefore, code 1
1 is a reaction tube made of quartz glass, 11a is a reaction chamber, 12
1 is an inflow boat for a reaction gas (hanification agent) Gl, which is connected to the reaction chamber 11a and integrally connected to the reaction tube 11;
3 is an exhaust gas G formed in the same manner as the inflow boat 12.
2 an outflow boat, 14 a cap made of quartz crow;
15 is a wafer (silicon substrate containing a large number of IC chips), 16 is a holder that supports multiple wafers 15, and 17 is a wafer 15 (inside the reaction chamber 11a).
18 is a joint part (low joint part) where the cap 14 is commonly rubbed, and PA is atmospheric pressure (7
60-Hr), PR represents the pressure inside the reaction chamber 11a, G1 represents the reaction gas (for example, 0 gas), and G represents the exhaust gas after the reaction. Since each of these parts is formed in the same manner and functions in the same manner as in the case of FIG. 1, the explanation thereof will be omitted.

Now, in FIG. 2, reference numeral 20 indicates the entire oxidation diffusion device of the present invention. As shown, the cap 1 of the reaction tube 11
An outer cap portion 21 made of quartz glass is provided which is integrally connected to the reaction tube 11 and covers the outer portions of the four portions in a sealed manner with an appropriate space therebetween. The outer cap portion 21 is composed of a cap body 22 and an outer cap 23, and the cap 23 is removably attached to the cap body 22 in close contact with a joint portion 24 which is formed by a common sliding fit. Roughly outside (Ill cap part 21
An inflow boat 25 and an outflow boat 26 for the reaction gas G are integrally provided. In this way, in this embodiment, the cap 14 portion of the reaction tube 11 is formed into a double tube structure. The inflow boat 12 of the reaction tube 11 has a flow control valve 27.
A supply pipe 28 for reactant gas G formed in a bifurcated shape via
is connected to one branch path 28a. and evening k
The inflow boat 25 of the 9 (+1 cap portion) is connected to the other branch line 28b of the supply pipe 28 via a gas Jjl line hose (for example, a Teflon tube) 29 and a check valve 30. Boat 13 is a natural pump 3
1, and the vacuum pump 31 is driven by a drive motor 32. The vacuum pump 31 plays the role of forcibly exhausting the exhaust gas Gtt after the reaction in the reaction chamber 11a and maintaining the pressure PR in the reaction chamber 11a at a vacuum pressure as required. The flow rate control valve 27 plays a role of controlling the flow rate of the reaction gas G sent into the reaction chamber 11a. The check valve 30 controls the reaction gas G1 that has been force-fed into the supply pipe 28 if:l
The outer fi 11 is sent out toward the inner space 21a shaped like J by the cap part 21, and in case of an emergency, the reaction nonosu G from the bi 1 part space 21a is
It plays a role in preventing the backflow of I. Therefore, the internal space 21
The pressure P^ at a is normally maintained slightly higher than the atmospheric pressure PA, and at least does not become lower than the atmospheric pressure PA. As a result,
The relationship between PA and PA is such that the state of Pλ≧PA is always maintained, and the outside air flows through the joint 24 into the internal space 21a.
Intrusion into the interior is completely prevented. Therefore, the entire interior of the internal space 21a is occupied by the reaction gas G. On the other hand, since the pressure PR in the reaction chamber 11a is maintained at the desired vacuum pressure as described above, the internal space 21a
The relationship with the pressure PA in a is PR<PA. Therefore, the gas in the internal space 21a may slightly enter the reaction chamber 11a through the joint 18 of the cap 14, but the gas entering from within the internal space 2Ia is the reaction gas G1 itself as described above. Therefore, the oxide film formed on the wafer 15 can be formed as a clean and high-quality film without being contaminated.

Furthermore, by setting the pressure PR in the reaction chamber 11a to a desired low pressure (vacuum pressure) as described above, the growth speed of the oxide film can be slowed down, resulting in an extremely thin (
For example, even when forming an oxide film of about 100X, its thickness and depth can be sufficiently controlled, and the thickness distribution can be made uniform. Further, in this embodiment, an oxidation diffusion process for the purpose of impurity diffusion can be used, and a thin oxide film of good quality can be obtained for the same reason as explained above. Furthermore, this embodiment is extremely useful even when a toxic gas such as hydrochloric acid is used as the reaction gas.

Note that the present invention is not limited to the above embodiments,
For example, it can be applied not only to silicon substrates but also to substrates made of other materials.
The internal pressure PR is not limited to approximately atmospheric pressure and vacuum pressure, respectively, as illustrated above, but can be applied even when the pressure is high by maintaining the state PA>PR. Further, the material of the reaction tube is not limited to quartz glass, and it goes without saying that other materials such as SiC (silicon carbide) can also be used.

(G) Effects of the Invention As explained in detail above, the septic diffusion device of the present invention has a cap portion of a reaction tube formed into a double tube structure, and the pressure in the internal space of the outer cap portion is transferred to the reaction tube. By setting and controlling the pressure higher than the pressure inside the reaction chamber, it is possible to prevent the intrusion of contaminants and improve the controllability of the film thickness distribution. degree)
However, it has the great effect of being able to form an uncontaminated, clean, high-quality oxide film with a uniform thickness and depth distribution, which contributes to improved product functionality and reliability.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional oxidation diffusion device, and FIG. 2 is an explanatory diagram of an oxidation diffusion device of the present invention. DESCRIPTION OF SYMBOLS 11... Reaction tube made of quartz glass, 11a... Reaction chamber, 12.25... Inflow port for reaction gas (branching agent) Gl), 13... Outflow port for exhaust gas G2 after reaction , 14... Cap made of quartz glass, 18...
Joint part (fitting part) of the cap 14 processed by common finger fitting, 20... Oxidation diffusion device of the present invention, 21... Outer cap part, 21a... Internal space of the outer cap part 21, 22 ...Cap body, 23...Outer cap, 24...Outer 1111 Common 4fl of cap 23
D-matched joint (fitting part), 26... Outflow port for reaction gas GI, 27... Flow rate control valve, 28...
・Bifurcated supply pipe, 28a, 28b...branch path, 3o・
...Check valve, 31...Vacuum pump, PA...Atmospheric pressure (760+anr), p4...Pressure collar PR in internal space 21a...Pressure in reaction chamber 11a. Patent applicant Fujitsu Ltd. Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Yukio Uchida F.A. Akira Yamaguchi

Claims (1)

[Claims] 1. An oxidation diffusion device comprising a reaction tube which forms a reaction chamber for storing a sample on which an oxide film is to be formed, and which has a reaction gas inflow boat and an exhaust gas outflow boat communicating with the reaction chamber. An outer cap part is formed to cover the outer part of the cap part of the reaction tube in a sealed state through an appropriate space, and has an inflow boat and an outflow boat for reaction gas, and is integrally connected to the reaction vessel. Particularly, the cap portion of the reaction tube is formed into a double tube structure, and the pressure in the internal space of the outer camp portion is controlled to be higher than the pressure inside the reaction chamber. oxidation diffusion equipment.