JPH0258214A - Manufacture of semiconductor - Google Patents

Abstract

PURPOSE:To prevent the deposition of a harmful material on an optical-pumping entrance window when an silicon film is deposited through an optical CVD method by independently heating the optical-pumping entrance window at a temperature higher than a substrate heating temperature while forming a thin- film onto a substrate by using a specific mixed gas. CONSTITUTION:In an optical CVD method in which an silicon thin-film is deposited onto a substrate 1 in a reaction vessel 3 through a photochemical reaction, an optical-pumping entrance window 4a of the reaction vessel 3 is heated independently at a temperature higher than the heater temperature of the substrate 1 while the mixed gas of a gas being photochemical-pumped only under the heated state of the entrance window 4a and function as the etching gas of silicon and an silicon supply gas photochemical-pumped without heating as a reaction gas is introduced into the reaction vessel 3 and the silicon thin-film is deposited onto the substrate 1. A low-pressure mercury lamp is used as a light source 2. The optical-pumping entrance window 4a is heated at the high temperature by an entrance window heater 12 while the substrate 1 is heated by a substrate heater 6, and the silicon film is deposited through the optical CVD method by employing the mixed gas of Si2H6 and HCl.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor manufacturing method, and in particular to a method for manufacturing a semiconductor, in which a silicon thin film is deposited on a substrate by a photochemical reaction of a reactive gas.
This relates to the VDR method. .

[Prior Art] FIGS. 3 and 4 are diagrams showing the most basic configuration of a conventional optical CVD apparatus. Figure 3 is an example of an apparatus using an incoherent light source such as an ultraviolet lamp. In other words, in Figure 3, 1 is a substrate on which a silicon thin film is formed, 2 is a light source such as an ultraviolet lamp, and 3 is a light source such as an ultraviolet lamp. The reaction vessel is provided with an excitation light entrance window 4a through which excitation light from the light source 2 enters, and a substrate 1 is placed and housed therein on a substrate support f=35. A substrate heater 6 is provided to heat the substrate. 7 is a reflecting mirror that reflects the excitation light from the light source 2; 1o is a reaction gas inlet; 11
is an exhaust port for exhausting gas after the reaction.

Since the output light of the light source 2 is diverging, in order to increase the utilization efficiency of the emitted output light, a reflecting mirror 7 of an appropriate shape and an excitation light entrance window 4 with a certain large area are used.
A is needed.

FIG. 4 shows an example of a device using a coherent light source 8 such as a laser. The output light 9 of the light source 8 has strong directivity and is in the form of a beam, so the excitation light entrance window 4a only needs to have an area equal to the beam cross section. Can be made smaller. Note that 4b is a laser beam exit window, and other symbols indicate the same components as in FIG. 3.

[Problem to be solved by the invention]

The equipment-related problems of the photo-CVD method as described above are 1. The film to be deposited on the substrate 1 by the photo-CVD apparatus is transparent to the excitation light. There is no problem if it is present, but if the film is opaque or absorbs excitation light, it will be a fatal problem for production equipment.

For example, when a silicon oxide film is deposited on the substrate 1 using ultraviolet rays (mainly wavelengths of 1849 and 2537) emitted from a low-pressure mercury lamp as excitation light, the silicon oxide film is simultaneously deposited on the excitation light entrance window 4a. 3. does not inhibit film deposition on the substrate 1; However, jfI of board 1
When the Ml151i species is a silicon film, even if the film is extremely thinly deposited on the excitation light incidence window 4a, it prevents the excitation light from entering the reaction vessel 3 and prevents the silicon film from being deposited on the substrate 1. If the deposition is stopped at the back of the initial stage, a silicon film with a practical thickness of 1 μm cannot be obtained. In conventional optical CV l) devices, in order to solve problem (B), for example, the vicinity of the excitation light incidence window 4a is purged with an inert gas such as Contact with the surface of the window 4a is suppressed, but in many cases the effect is insufficient.

This invention was made in order to solve the above-mentioned problems, and in particular, when depositing a silicon film by the optical CVL method, unnecessary and harmful substances are removed from the excitation light entrance window.
Semiconductor that does not have L-shape! +! ! Hiroshi method aims to complete the method. 1 [Means for Solving the Problems] The semiconductor manufacturing method according to the present invention achieves photochemical excitation only in the heated state (1) and (2) when the excitation light entrance window is independently heated to a higher temperature than the substrate heating humidity. A T8 film is formed on a substrate using a gas mixture of a gas that is etched and acts as an etching gas for silicon, and a silicon supply gas that is photochemically excited even without heating as a reaction gas.

[Effect]

In this invention, while heating the substrate, a gas mixture of a gas that is photochemically excited only in a heated state and acts as a silicon etching gas and a silicon supply gas that is photochemically excited even without heating is used as a reaction gas. Therefore, if the -fj gas in the mixed gas is exposed to ultraviolet rays at a temperature above a certain temperature, it is assumed that the silicon
Under suitable conditions, it is deposited on the excitation light entrance window, and 1. The etching/soching rate is superior to the deposition rate of the silicon to be etched, and the excitation light entrance window is always kept transparent.On the other hand, at low temperatures near room temperature, it does not act as an etching gas even when irradiated with ultraviolet rays, but is simply an inert gas. Therefore, only photochemical decomposition of the silicon supply gas occurs on the substrate heated at a low temperature, and silicon is deposited.

〔Example〕

An embodiment of the present invention has been described above with reference to FIG.

In FIG. 1, the same reference numerals as in FIGS. 3 and 4 indicate the same elements, and reference numeral 12 is an entrance window heating heater that heats the excitation light input: aaa independently of substrate heating.

In this embodiment, a low-pressure mercury lamp is used as the light source 2.
A gas that is photochemically excited only when heated and acts as an etching gas, such as Maruba 100% L.
(Figure 1 shows the relationship between the etching rate of the silicon substrate and the substrate temperature when the silicon substrate (p-type (100) substrate) placed in CI is heated and irradiated with ultraviolet rays. , At the same time, the etching rate is also plotted when only the substrate is heated without UV irradiation. This can be called thermally assisted photochemical etching only when the etching is heated to about 200° C. or higher and irradiated with ultraviolet rays.

This emitter 1 utilizes the characteristics of to prevent the #8 product of silicon from entering the excitation light incidence window 4R, and the following two points are important. .

(+) The excitation light entrance window 4a is heated independently of substrate heating; 1. The reaction gas is a mixture of silicon supply gas such as Si2H6 or SiH4 and 11 CI; 1. A low-pressure mercury lamp. Ultraviolet rays (wavelengths are mainly 1849
When depositing silicon using the optical CV l) method, the silicon supply gas is usually 5i2H, which absorbs the above wavelengths and can be photochemically decomposed even at room temperature. Heating does not affect the photochemical decomposition of Si2H6 itself, but merely controls the film quality (electrical properties, optical properties, etc.) of the deposited silicon film. Therefore, for example, with a device as shown in FIG. If the substrate 1 is heated to the substrate heating peak 6 (lower temperature), then II CI, one of the gases in the mixture introduced into the reaction vessel 3, will become substantially inert (because the temperature is too low) on the substrate 1. acts as a gas, 5i21
1. On the other hand, on the excitation light entrance window dn, the S
Not only 1□H6 but also II e l is photochemically decomposed,
Since it has an esotinog action of silicon, if the mixing ratio etc. are set appropriately, the deposition speed of silicon will increase on the excitation light entrance window 4a, and the excitation speed will always be -hh<e. 4a can be kept transparent. .

One important point in this invention is that at low temperatures near the room temperature, photochemical excitation does not occur, but when thermally assisted at high temperatures, there is a combination of reactive gas and excitation light that causes photochemical excitation. By doing so, )l CI and purple light from a low-pressure mercury wrap (the combination of lines is an example of this)1.Furthermore, such a temperature-sensitive photochemical gas and a temperature-insensitive gas, i.e., at room temperature, This is an important point when mixing the silicon supply gas, which has already absorbed excitation light and photochemically decomposes, to create a reaction gas.
However, depending on the temperature, the reaction gas is controlled to have either a deposition property or an etching property.

[Effects of the Invention] As explained above, the present invention raises the temperature at the excitation light incident window where silicon deposition is undesirable to make the reaction gas non-etching, and conversely, when the excitation light entrance window is undesirable for silicon deposition, the reaction gas is made non-etching. Raise the temperature on the substrate where it is desired to release the reactant gas.
It is possible to keep the excitation light entrance window of the device transparent at all times and to form a continuous silicon film without slowing down the deposition rate on the substrate. Moreover, it is effective because it can be deposited stably.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the schematic configuration of an optical Cvl) device showing an embodiment of the invention of B, Fig. 2 is a diagram showing the relationship between substrate humidity and etching rate, and Figs. 3 and 4 are conventional etching methods. optical CVD
FIG. 1 is a cross-sectional view showing a schematic configuration of the device. In the figure, 1 is a substrate, 2 is a light source, 3 is a reaction container, 4u
4b is the excitation light entrance window, 4b is the beam exit window, 5 is the substrate support, 6 is the substrate heating peak, 7 is the reflection tQ, and 12 is the entrance window heating. . Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Masuo Oiwa (2 others) Figure Vapor deposition temperature (0C) 1. Indication of the case Japanese Patent Application No. 1983 208963 2. Name of the invention Semiconductor manufacturing method 3. Person making the amendment Relationship to the case Patent applicant Address: 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative: Moriya Shiki 4, Acting address: Within Mitsubishi Electric Corporation, 2-2-3 Marunouchi, Chiyoda-ku, Tokyo (7375) Patent attorney Masuo Oiwa (contact number 03 (2) 3) 3421 Patent Department) 5,
71n In column 6 of the Detailed Description of the Invention in the correct subject specification, amend the following on page 9, line 5 of the description of the contents of the amendment to read ``without'' and ``with''.

Claims (1)

[Claims] In an optical CVD method in which a silicon thin film is deposited on a substrate in a reaction vessel by a photochemical reaction, the excitation light entrance window of the reaction vessel is independently heated to a temperature higher than the substrate heating temperature, and the photochemical reaction is performed only in this heated state. A silicon thin film is deposited on the substrate by introducing into the reaction vessel a gas mixture of a gas that is excited and acts as an etching gas for silicon and a silicon supply gas that is photochemically excited even without heating as a reaction gas. A semiconductor manufacturing method.