JP2516040B2 - Thin film forming method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for selectively forming a thin film on the surface of a substrate such as a semiconductor substrate.

(Prior Art) FIG. 5 shows an example of a conventional thin film forming apparatus, and raw material gases for forming a thin film are monosilane (SiH ₄ ) and nitrous oxide (N ₂ O). Argon (Ar) is used as the carrier gas. Nitrous oxide is introduced into the reaction chamber 10 through the valve 30, and monosilane and argon are introduced into the reaction chamber 10 through the valve 32 and the blowing ring 6 and sprayed onto the surface of the substrate 1. The substrate 1 is placed on the substrate holder 3 having the temperature control mechanism 50. The temperature control mechanism 50 is composed of the heater 2, a thermocouple (not shown), a PID control device and a heater power supply, and has a function of keeping the temperature of the substrate 1 constant at a desired temperature.

The gas in the reaction chamber 10 is exhausted through the valve 34 in the direction of arrow 44 by a vacuum pump (not shown).

When monosilane and nitrous oxide are introduced into the reaction chamber while the temperature of the substrate 1 is kept constant, a silicon dioxide film is formed on the surface of the substrate 1.

FIG. 4 is a cross-sectional view of the surface of a substrate showing the process of forming a silicon dioxide film by a conventional method such as a semiconductor device. Fourth
In FIG. A, a silicon dioxide film 2 as an insulating film is formed on the Si substrate 100.
Form 00. Then, on the silicon dioxide film 200, FIG.
As shown in, an aluminum film 300 is formed as a wiring layer. Then, patterning is performed to form aluminum wirings 310 and 320 as shown in FIG. 4c. Next, as shown in FIG. 4d, a second silicon dioxide film 400 is formed on the entire surface of the substrate.

In this case, a silicon-based gas such as mosilane or disila and an oxidizing gas such as oxygen or nitrous oxide are used as a source gas, and the silicon dioxide film 400 is formed by a thermal CVD method, an ECR plasma CVD method, or an optical CVD method. . Formation by a sputtering method using a target of solid silicon dioxide is also often performed. As shown in FIG. 4d, the formed silicon dioxide film 400 has an uneven surface reflecting the shape of the underlying layer, so that it is difficult to achieve high-density integration of semiconductor devices as it is.
Therefore, conventionally, a polyimide resin 500 is applied as shown in FIG. 4e, and a dry etching process 600 (illustrated by an arrow) is performed.
Is added to flatten the surface.

(Problems to be Solved by the Invention) In the above-mentioned conventional method, the silicon dioxide film 400 is only formed on the entire surface of the substrate 1, and in the case of the substrate as shown in FIG. As described above, there is a problem that the silicon dioxide film cannot be formed only in the concave portion. As a technique for forming a thin film in a recess, there are planarization techniques such as a bias sputtering method and a bias plasma CVD method, and it is possible to form a thin film in the recess by using these planarization techniques, but the semiconductor produced There are new problems such as plasma damage to devices.

Further, in the conventional method of applying the polyimide described above, the polyimide has a poor film quality and causes contamination,
Further, there is a problem that the step 600 for flattening the substrate 1 is required.

(Object of the Invention) An object of the present invention is to provide a method and an apparatus for selectively forming a desired thin film on a desired portion of a substrate surface and planarizing the substrate surface.

(Means for Solving the Problem) In order to achieve the above object, the method of the first invention of the present application is used. That is, a raw material gas for forming a thin film and an etching gas for etching the formed thin film are introduced into the reaction chamber, and a desired pattern having different absorption efficiency for a predetermined electromagnetic wave is formed on the surface of the substrate. In addition, a method is used in which the surface of the substrate is irradiated with an electromagnetic wave so as to have a high and low temperature difference according to the pattern, and the thin film is selectively deposited according to the pattern.

The other uses the device of the second invention of the present application. A reaction chamber; a source gas introduction mechanism for introducing a source gas for forming a thin film into the reaction chamber; an etching gas introduction mechanism for introducing an etching gas for etching the formed thin film into the reaction chamber; An exhaust mechanism for exhausting the gas in the chamber; a substrate installed in the reaction chamber; a substrate holder for holding the substrate and controlling the temperature; and providing the substrate surface with a high and low temperature difference in accordance with a desired pattern. An apparatus adopting a configuration including a heating means for heating is used.

(Function) A raw material gas for forming a thin film and an etching gas for etching the formed thin film are introduced, and the conditions such as the pressure in the reaction chamber, the temperature of the substrate, and the flow rate ratio of the raw material gas and the etching gas are appropriately set. "Threshold" that balances thin film formation and thin film etching on the substrate surface
Since the temperature Tth exists, for example, the temperature of the entire substrate is maintained at a constant value of its equilibrium temperature. In this state, when the portion of the desired pattern on the substrate is partially heated and only the temperature of that portion is raised, that portion deviates from the equilibrium state and either thin film formation or thin film etching proceeds. Will be done.

In the case of the present application, when the temperature of the substrate is lower than the “threshold” temperature, the formation of the thin film proceeds, and when the temperature of the substrate is higher than the “threshold” temperature, the etching of the thin film proceeds.

Therefore, the temperature of the substrate surface may be kept at a constant value equal to or lower than the "threshold" temperature Tth.

Thus, by locally controlling the temperature of the surface of the substrate, a thin film can be selectively formed, for example, only in the recesses on the surface of the substrate.

(Example) First, the inventor of the present application conducted an experiment of forming a silicon dioxide film on the same substrate 1 as in FIG. 4a using monosilane and oxygen active species. 2 straight lines
As shown in DR, the deposition rate of the silicon dioxide film decreased linearly as the reciprocal value of the temperature T increased. This indicates that the thermal equilibrium reaction is proceeding on the surface. In this case, the apparent activation energy Ed (the slope of the straight line reveals it) was about 1.4 kcal / moi.

Next, the silicon dioxide film was etched using fluorine active species, and in this case as well, the etching rate decreased linearly as the reciprocal value of the temperature T increased as shown by the line ER in FIG. Apparent activation energy Ee in this case
Was about 3.7 kcal / mol.

Furthermore, when both monosilane and oxygen active species, which are the raw material gases for forming the thin film, and fluorine active species, which is the etching gas for the thin film, are used together, the film forming temperature region for forming the thin film and the thin film are etched. The existence of each of the etching temperature regions and the boundary temperature (hereinafter, "threshold" temperature) Tth at which the film formation temperature region and the etching temperature region intersect were found.

It has been known that these two straight lines DR and ER both significantly move up and down in equilibrium depending on the pressure and the flow rate ratio.For example, the flow rate of monosilane is 10 sccm, the flow rate of argon is 100 sccm, and the flow rate of nitrous oxide is When 120sccm, the flow rate of fluorine is 30sccm and the pressure is 0.7Torr,
The "threshold" temperature Tth was 300 ° C. The apparent activation energy Ed in the formation of the silicon dioxide film is the apparent activation energy Ee in the etching of the silicon dioxide film.
Is smaller than the “threshold” temperature Tth, the silicon dioxide film is etched when the temperature is higher than the “threshold” temperature Tth, and the film formation temperature region is lower when the temperature is lower than the “threshold” temperature Tth. Then, a silicon dioxide film was formed. No silicon dioxide was formed or etched when the temperature was just the "threshold" temperature Tth.

Then, when the conditions are changed over a wide range, DR and E in Fig. 2 are
It has been found that each R generally curves. The film formation temperature curve DR with respect to the temperature and the etching curve ER have a plurality of intersections, and therefore, there may be a plurality of film formation temperature regions, etching temperature regions and “threshold” temperatures Tth. The above was established without any problems in the individual Tths and their vicinity.

FIG. 3 shows the process of forming a silicon dioxide film by the method of the first invention of the present application, and the same members as those in FIG. 4 are designated by the same reference numerals.

In FIG. 3a, 5000 is placed on a silicon substrate (Si substrate) 100.
Å silicon dioxide film (SiO ₂ ) 200 is deposited by thermal CVD, sputtering,
An aluminum (Al) film 300 is formed as a wiring material on a film formed by a method such as plasma CVD method or plasma ECR method,
Patterned aluminum wiring (Al wiring) 310, 320
Is being made. Then, the base body 1 is placed on a base body holder, the temperature of the base body 1 is kept constant by heating the base body holder, and the entire temperature of the base body 1 is set to 3 above the equilibrium temperature Tth.
Set it to 290 °, which is slightly lower than 00 ° C.

Then, the aluminum wirings 310 and 320 of the substrate 1 are partially heated by an infrared lamp.

In this state, by introducing the raw material gas for forming the thin film and the etching gas for etching the formed thin film and setting the above film forming conditions, only the silicon dioxide 200 on the silicon dioxide 200 as shown in FIG. The silicon dioxide 410 could be selectively formed.

Generally, the absorption efficiency of the infrared rays 7 emitted from the infrared lamp differs depending on the substance, and is high in the case of metal such as aluminum, but is considerably small in the case of silicon or silicon dioxide because it is transparent.

Therefore, by utilizing this difference in absorption efficiency, a desired portion can be partially heated. Already, a technique utilizing this method includes a selective tungsten growth method, and partial heating of a pattern is a well-known technique. It has been established.

Although an infrared lamp is used for partial heating of the substrate surface here, electromagnetic waves such as microwave heating and high frequency heating may be used as long as they can partially heat a desired portion of the substrate surface. In that case, as the pattern material, for example, a polymer film that easily absorbs them is used. That is, the heating means is not limited to the above.

The material used for partial heating in this embodiment was aluminum, but the material is not limited to the material of this embodiment as long as the material has a significantly different absorption efficiency compared to silicon dioxide.

Further, in the above embodiment, the raw material gas for forming the silicon dioxide film and the etching gas for etching the silicon dioxide film were introduced at the same time. However, for the substrate whose temperature condition is as described above, Similar results could be obtained by the method of introducing these alternately.

Further, in the above embodiment, the film formation of silicon dioxide was described, but the same work was possible for the film formation of alumina, silicon nitride and the like.

In order to effectively implement the method of the first invention of the present application described above, the apparatus of the second invention of the present application was used. FIG. 1 shows a sectional view of the apparatus of this embodiment. 1 is a substrate, 2 is a heater, 3 is a substrate holder, 4 is an infrared lamp, 5 is an optical window, 6 is a blowing ring, 7 is infrared, 10 is a reaction chamber, 20
Is an oxygen activated species generator, 21 is a fluorine activated species generator, 30 to 34
Is a valve, 40 to 44 are respective gas flows, and 50 is a temperature control mechanism.

The gas shown by the arrow 44 includes the gas generated by the reaction in the reaction chamber 10.

The substrate 1 is placed on a substrate holder 3 having a temperature control mechanism 50. The temperature control mechanism 50 includes a heater 2, a thermocouple (not shown), a PID control device, and a heater power source (not shown), and keeps the temperature of the substrate 1 constant at a desired temperature.

The configuration of the temperature control mechanism 50 is not limited to the above as long as it is a mechanism capable of maintaining the temperature of the base body 1 at a desired temperature.

Partial heating of the desired pattern on the substrate 1 is performed by the infrared lamp 4.

Argon is blown to the optical window 5 through the bulb 33 so that a thin film is not formed on the surface of the optical window 5 which transmits and introduces the infrared rays 7 emitted from the infrared lamp 4.

In this embodiment, monosilane and nitrous oxide are used as the source gas for forming the thin film.

Monosilane as a silicon-based gas and argon as a carrier gas are sprayed onto the substrate 1 through the valve 32 and the blowing ring 6.

Nitrous oxide as an oxidizing gas is first introduced into the oxygen activated species generator 20. The oxygen active species generator 20 generates oxygen active species by turning nitrous oxide into a plasma state, and applies power from a high frequency power source (not shown) to the oxygen active species generator 20 by inductive coupling. By doing so, oxygen active species such as oxygen atoms are generated from nitrous oxide and introduced into the reaction chamber 10 through the valve 30.

A mesh, a mirror magnetic field or the like may be used between the oxygen active species generator 20 and the valve 30 so that the plasma in the oxygen active species generator 20 does not leak into the reaction chamber 10.

Fluorine is used as the etching gas for etching the thin film.
Introduced into the fluorine activated species generator 21 with the same function as
Fluorine active species such as fluorine atoms are generated and introduced into the reaction chamber 10 through the valve 31.

The gas in the reaction chamber 10 is exhausted through the valve 34.

The two active species generators 20 and 21 may be of any type as long as they can generate the active species, and the generation method is not limited. Depending on conditions such as the type of gas used, the temperature of the substrate, the pressure in the reaction chamber 10 and the flow rate ratio of the gas, any one or all of the active species generators may not be necessary, and the active species generators may also be used. It is not essential to the invention.

(Effects of the Invention) As described above, with the method and apparatus of the present invention, it is possible to selectively form a thin film on the bottom portion or the concave portion of a substrate having a step or a concave portion to planarize the substrate.

[Brief description of drawings]

FIG. 1 is a sectional view of an apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the film formation rate and the etching rate and the reciprocal of temperature in this example. FIG. 3 is a substrate cross-sectional view showing the process of forming a silicon dioxide film according to the present invention. FIG. 4 is a sectional view of a substrate showing an example of a conventional process for forming a silicon dioxide film. FIG. 5 is a sectional view of a conventional thin film forming apparatus. 1 ... Base, 2 ... Heater, 3 ... Base holder, 4
...... Infrared lamp, 5 ... Optical window, 6 ... Blowout ring, 7 ... Infrared, 10 ... Reaction chamber, 20 ... Activated species generator A for generating oxygen activated species, 21 ... Fluorine activated Seed active species generator B, 30, 31, 32, 33 ... Valve, 50 is temperature control mechanism, 100 ... Silicon substrate, 200 ... First layer silicon dioxide film, 300, 310, 320 ... Aluminum Membrane, 400, 410 ...
… Second layer of silicon dioxide film, 500 …… Polyimide, 600 ……
Dry etching.

Claims (4)

(57) [Claims] 1. A thin film is formed by keeping a constant temperature of a substrate by a temperature control mechanism of a substrate holder in a reaction chamber into which a source gas is introduced and depositing a part of constituent elements of the source gas on the surface of the substrate. In the method for forming a thin film to be formed, an etching gas for etching the formed thin film is introduced into the reaction chamber, and a desired pattern having a different absorption efficiency for a predetermined electromagnetic wave is formed on the surface of the substrate, A method for forming a thin film, characterized in that the surface of the substrate is irradiated with electromagnetic waves so that the pattern has a temperature difference of high and low, and the thin film is selectively deposited according to the pattern. 2. The apparent activation energy Ed of the raw material gas for forming a thin film is smaller than the apparent activation energy Ee of the etching gas for thin film etching in terms of thermal equilibrium reaction. A method for forming a thin film as set forth in claim 1. 3. The raw material gas is monosilane and nitrous oxide,
3. The etching gas is fluorine, the pattern is an aluminum film patterned on silicon dioxide, and the silicon dioxide film is selectively formed on the silicon dioxide. 3. Thin film forming method. 4. A reaction chamber; a source gas introduction mechanism for introducing a source gas into the reaction chamber; an exhaust mechanism for exhausting gas in the reaction chamber; a substrate installed in the reaction chamber; In a thin film forming apparatus for forming a thin film by depositing a part of the constituent elements of the source gas on the surface of the substrate, the etching gas for etching the formed thin film is included. A thin film forming apparatus, comprising: an etching gas introducing mechanism for introducing the reaction gas into the reaction chamber; and a heating unit for heating the surface of the substrate with a high and low temperature difference according to a desired pattern.