KR20050116492A - Method for manufacturing the aluminium oxide thin film of semiconductor devices using the atomic layer deposition - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an Al ₂ O ₃ thin film as a dielectric material constituting a capacitor for a memory in a DRAM by an atomic layer deposition method. The first step of introducing the amine-based compound for a predetermined time (T1), the second step of stopping the introduction of the aluminum source and the amine-based compound for a certain time (T2), oxygen source in the reactor, and non-covalent as a catalyst A third step of introducing an amine compound having an electron pair for a predetermined time (T3), and a fourth step of stopping the introduction of the oxygen source and the amine-based compound for a certain time (T4) Provided are a method for forming an Al ₂ O ₃ thin film of a semiconductor device. According to the present invention, low through-put can be improved innovatively, and the improvement can also reduce the cost of equipment investment.

Description

TECHNICAL FOR MANUFACTURING THE ALUMINIUM OXIDE THIN FILM OF SEMICONDUCTOR DEVICES USING THE ATOMIC LAYER DEPOSITION}

The present invention is Al ₂ O ₃ (aluminum oxide) as a dielectric material constituting the capacitor for memory in DRAM The present invention relates to a method for forming a thin film by an atomic layer deposition (ALD) method, and more particularly, to a method for forming an Al ₂ O ₃ thin film capable of further improving the deposition rate of an Al ₂ O ₃ thin film.

Although Al ₂ O ₃ has a relatively low dielectric constant (ε = 9), it has excellent thermal stability and low permeability to impurities such as alkali ions, so that it is a dielectric material of DRAM capacitors under 0.12um design rule. Has been used. In order to deposit such Al ₂ O ₃ , molecular beam epitaxy (MBE), chemical vapor deposition (CVD), plasma enhanced-metal organic chemical deposition (plasma enhanced-metal organic chemical deposition, PE-MOCVD), reactive sputtering, and atomic layer deposition methods can be selected, but among these, low temperature process and precise thickness control required to deposit thin films under 0.12um design rule are possible. The method of satisfying both the uniformity and coatability of the thin film is an atomic layer deposition method that follows a surface limited reacting mechanism.

A deposition step of a dielectric material by a general atomic layer deposition method is shown in FIG. As shown in FIG. 1, the atomic layer deposition method first supplies a source [in the case of Al ₂ O ₃ deposition, mainly TMA (trimethylaluminum, Al (CH ₃ ) ₃ )] to induce a surface reaction (source supplying step), After removing the unreacted source, the reaction adduct, etc. in the next purge step (first purge step), the reactant [mainly H ₂ O or O _{3 in} the case of Al ₂ O ₃ deposition] is supplied and adsorbed on the surface. React with the surface group of AlCH ₃ ^* , or AlCH ₂ ^* (reactant feed step), and remove unreacted reactants, reaction adducts, etc. in the next purge step (second purge step). Here, * denotes a surface state, and in general, a solid surface has an energy state different from that of a solid inside because there is no repeatability of a lattice unlike a solid inside, and this surface state is activated. Reaction occurs easily.

Since the atomic layer deposition method has a self-limiting reaction characteristic, it is possible to control the thickness of the thin film on an atomic layer basis, so that the deposition can be performed regardless of the topology of the underlying film, thereby realizing a conformal thin film. Importantly, in order to ensure the isotropy and uniformity of the thin film, the deposition rate must be saturated by supplying a sufficient flow rate (Q), that is, a flow rate (Qc) above a threshold value, so that the source and the reactants can react with the entire exposed surface. (See Figure 2). Here, the deposition rate means thickness / cycle deposited per cycle, and one cycle means a series of steps of a source supply step, a first purge step, a reactant supply step, and a second purge step (the 1 refers to the time it takes to pass once). Since Qc can be expressed as the product of flow rate and feed time, it can be achieved by increasing the flow rate or increasing the feed time of the source and reactants in order to supply the sources and reactants at a sufficient flow rate. However, the method of increasing the flow rate among them makes it difficult to form a uniform thin film throughout the substrate by causing the vortex of the gas, and thus a method of increasing the supply time of the source and the reactant is generally used. Accordingly, it is pointed out that the atomic layer deposition method is three times slower than the CVD method. In general, using ordinary atomic layer deposition equipment that takes 10 seconds per cycle, the deposition rate for depositing Al ₂ O ₃ with TMA and H ₂ O (or O ₃ ) is 0.06 to 0.08 μs / sec, i.e. 0.36 to 0.48 mW / min, which is largely different from the deposition rate of 100 mW / min (650 ° C.), which is the case of using the LP-CVD method.

In order to overcome the problem of the low deposition rate of the atomic layer deposition method, an effort to improve the deposition rate by reducing the number of steps per cycle compared to the general atomic layer deposition method (Korean Patent Publication No. 10-2001-110531 However, this method leaves the question of whether they can be supplied at a sufficient flow rate without vortexing when feeding the source and reactants to form an isotropic and uniform thin film.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for improving the deposition rate of a dielectric material using a catalyst in depositing an Al ₂ O ₃ thin film as a dielectric material on a semiconductor substrate using an atomic layer deposition method.

In the present invention, as a result of intensive research to achieve the above technical problem, when introducing the reaction source in the atomic layer deposition method, the amine-based compound having a lone pair as a catalyst is introduced at the same time as the reaction source As a result, the present inventors have found that the deposition rate of the dielectric material can be improved by promoting the reaction between the semiconductor substrate and the source, thus completing the present invention.

In the method of forming an Al ₂ O ₃ thin film using an atomic layer deposition method, an amine compound having an aluminum source and a non-covalent electron pair as a catalyst in a reactor into which a semiconductor substrate is introduced for a predetermined time (T1) The first step of introducing, the second step of stopping the introduction of the aluminum source and the amine compound for a predetermined time (T2), the oxygen source in the reactor, and the amine compound having a lone pair as a catalyst for a certain time (T3 A method for forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method comprising a third step of introducing during the step and a fourth step of stopping the introduction of the oxygen source and the amine compound for a predetermined time (T4). To provide. In the present invention, an amine compound having a non-covalent electron pair such as pyridine (C ₅ H ₅ N) and ammonia (NH ₃ ) as the catalyst, and TMA (trimethyl aluminum, Al (CH ₃ ) ₃ ) may be used as the aluminum source. not limited in this respect, is the source of oxygen as O ₃ or, preferably, in the vapor phase H ₂ O, it can be used in the vapor phase H ₂ O. The temperature in the reactor in the first step to the fourth step is preferably maintained at 300 ~ 700 ℃, the pressure is preferably maintained at 10mTorr ~ 10Torr, the T1 to T4 can be adjusted to 10msec ~ 10sec respectively. . In addition, the aluminum source, the catalyst, and the oxygen source introduced into the reactor are preferably introduced in amounts of 10 ⁹ to 10 ⁵ langmular (= 10 ^-6 Torr x sec), respectively.

In addition, the present invention is a method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method, the first step of introducing a semiconductor substrate into the reactor, the semiconductor substrate 10 seconds ~ 10 at 300 ℃ or more A second step of preheating for a minute, a third step of introducing Al (CH ₃ ) ₃ and C ₅ H ₅ N into the reactor in an amount of 10 ⁹ ~ 10 ⁵ langmular for 10 msec ~ 10 sec, the Al (CH ₃ ) ₃ And stopping the introduction of C ₅ H ₅ N for 10 msec to 10 sec, and then introducing or pumping purge with an inert gas selected from argon gas and nitrogen gas, and H ₂ O and C ₅ in the vapor state in the reactor. a H ₅ N in 10msec ~ 10 ⁹ ~ 10 ⁵ a fifth step of introducing an amount of langmular, after the introduction of the H ₂ O and C ₅ H ₅ N interrupted for 10msec ~ 10sec, argon gas and nitrogen gas for 10sec A sixth step of introducing, or pumping and purging the selected inert gas, and the third step Using the atomic layer deposition method, comprising the step 7 for repeating the sixth step provides the Al ₂ O ₃ thin film formation method of a semiconductor device. At this time, NH ₃ may be introduced as another amine compound having a lone pair instead of C ₅ H ₅ N, but is not limited thereto. In the second step, inert gas such as argon gas or nitrogen gas may be preheated to shorten the heating time of the substrate and to adjust the pressure in the reactor, and then, in the reactor in the third to sixth steps. The temperature is preferably maintained at 300 to 700 ° C., and the pressure in the reactor is preferably maintained at 10 mTorr to 10 Torr. In the present invention, the reaction taking place in the third step of introducing Al (CH ₃ ) ₃ and C ₅ H ₅ N into the reactor in an amount of 10 ⁹ ~ 10 ⁵ langmular for 10 msec ~ 10 sec is the following scheme 1a or 1b

Substrate-Al- (OH) ₂ ^* + Al (CH ₃ ) ₃ + C ₅ H ₅ N → Substrate-AlOH-O-Al (CH ₃ ) ₂ ^* + CH ₄ ↑ + C ₅ H ₅ N

Substrate-O-Al-OH ^* + Al (CH ₃ ) ₃ + C ₅ H ₅ N → Substrate-O-Al-O-Al- (CH ₃ ) ₂ ^* + CH ₄ ↑ + C ₅ H ₅ N

Where * indicates surface condition

The reaction takes place in the fifth step of introducing the steam H ₂ O and C ₅ H ₅ N in the reactor in the amount of 10 ⁹ ~ 10 ⁵ langmular for 10 msec ~ 10 sec is represented by the following scheme 2a or 2b

Substrate-AlOH-O-Al (CH ₃ ) ₂ ^* + H ₂ O + C ₅ H ₅ N → Substrate-Al-O-Al-OH ^* + CH ₄ ↑ + CH ₃ OH + C ₅ H ₅ N

Substrate-O-Al-O-Al- (CH ₃ ) ₂ ^* + H ₂ O + C ₅ H ₅ N-> Substrate-O-Al-O-AlCH ₃ -OH ^* + CH ₄ ↑ + C ₅ H ₅ N

Where * indicates surface condition

It can be represented by. As described above, by repeating the cycle until the desired thickness is secured using the third to sixth cycles, a semiconductor device in which an Al ₂ O ₃ thin film having a desired thickness is formed can be obtained.

Hereinafter, a method of forming an Al ₂ O ₃ thin film of a semiconductor device using a catalyst according to the present invention will be described in more detail with reference to the accompanying drawings showing an embodiment of the present invention. However, the following drawings and description are not intended to limit the invention, the invention may be appropriately modified and modified based on the matter described in the claims.

3A and 3B illustrate the formation of an Al ₂ O ₃ thin film on a semiconductor substrate in accordance with the present invention using TMA as an aluminum source, H ₂ O in the vapor state as an oxygen source, pyridine as a catalyst, and argon gas as an inert gas. The method is a simplified diagram of each step. The type of the semiconductor substrate suitable for applying the method according to the present invention is not limited, but is not limited to a undoped bare silicon substrate, a polycrystalline silicon substrate, a doped silicon substrate, a single metal substrate, a binary ) It can be applied to either a substrate which is a metal or a substrate which is a dielectric.

3A and 3B, the horizontal axis represents time for each step, and T1, T2, T3, and T4 represent about 10 msec to 10 sec, respectively, and the vertical axis describes gas introduced into the reactor by type, and is supplied at each corresponding time. The gas to be turned on was indicated as "on", and the gas not to be supplied was indicated as "off". As shown in Figures 3a and 3b, the present invention first introduces TMA into the reactor at the same time as pyridine during T1, and when T1 has elapsed, introduces and purges the argon gas while stopping its introduction for T2, and then steam for T3. H ₂ O in the state can be introduced into the reactor at the same time as the pyridine, and then, when T 3 elapses, argon gas is introduced and purged while the introduction thereof is stopped during T 4. In this case, the H ₂ O in the vapor state may be supplied by heating the water above the boiling point or by supplying H ₂ and O ₂ by flame reaction with each other in a WVG (water vapor generation) apparatus.

On the other hand, T1 and T3 during even as addition can be introduced into the inert gas such as argon gas in order to maintain the pressure, and, upon introduction of the reaction source (TMA, T3 H ₂ O while for T1) and pyridine carrier gas in the reactor It can also be introduced together using an inert gas. Such TMA, H ₂ O, pyridine and inert gas may be introduced by pre-heating immediately before introduction into the reactor. It is also possible to pump the inside of the reactor to facilitate the flow of gas in the reactor during T1 and T3 and to allow the inflow of the reaction source to continue.

The introduction of argon gas during T2 and T4 may include TMA, pyridine, reaction byproducts (CH _4, etc.) remaining in the reactor after T1, and H ₂ O, pyridine, reaction byproducts remaining in the reactor after T3. (CH ₄ etc.) and the like, respectively, may be purged by pumping the inside of the reactor using a pumping line connected to the reactor instead of purging with an inert gas such as argon gas. On the other hand, during T2 and T4, surface species adsorbed on the substrate by the reaction during T1 and T3, that is, (substrate) -AlOH-O-Al (CH), which is the surface species adsorbed on the substrate by the reaction during T1. ₃ ) ₂ ^* or (substrate) -O-Al-O-Al- (CH ₃ ) ₂ ^* and (substrate) -Al-O-Al-OH ^* which is the surface species adsorbed on the substrate by reaction during T3 or (Substrate) -O-Al-O-AlCH ₃ -OH ^* can be seeded by surface migration to reduce surface energy.

The chemical reaction between each compound introduced into the reactor, which occurs during T1 of FIG. 3A and T3 of FIG. 3B, may be illustrated as shown in FIGS. 4A and 4B, respectively. As shown in Fig. 4A, pyridine introduced into the reactor during T1 is H ⁺ ions of -OH groups, such as Al (OH) ₂ ^* , O-Al-OH ^* , in which a non-covalent electron pair of its N atoms is present in the underlying film. and it forms the hydrogen bond, such H ⁺ of activated by the hydrogen bonding group -OH ions [CH _3] of an aluminum source, TMA introduced into the reactor at the same time as the ^{pyridine-hydrogen} bond is formed transient. As described above, the oxygen atom of the -OH group activated by the hydrogen bond facilitates the reaction with the aluminum atom of the TMA, so that the reaction is promoted, and thus the time of T1 can be shortened. This reaction during T1 can be summarized in Scheme 1a or Scheme 1b as shown above, and CH ₄ is produced as a reaction by-product. This reaction principle is the same even when ammonia is used instead of pyridine as a catalyst, which can be seen in FIG. 4C.

Similarly, as shown in Fig. 4B, pyridine introduced into the reactor during T3 has a hydrogen bond with the H ⁺ ions of H ₂ O whose non-covalent electron pair of N atoms is an oxygen source introduced into the reactor at the same time as the pyridine. the forms, the active hydrogen bonds by such H ⁺ ions are formed by H ⁺ ions and also hydrogen bonding of the TMA coupled to the base film by a reaction for T1 -CH ₃ group. As described above, the aluminum atom of TMA bonded to the base film activated by hydrogen bonding facilitates the reaction with the oxygen atom of H ₂ O and promotes the reaction, so that the time of T 3 can be shortened, and as a result, the entire deposition Can improve speed. This reaction during T3 can be summarized in Scheme 2a or Scheme 2b as shown above, again with CH ₄ being produced as a reaction byproduct. This reaction principle is also true when ammonia is used instead of pyridine as a catalyst.

As described above, when the Al ₂ O ₃ thin film is formed as the dielectric material of the semiconductor device by the atomic layer deposition method, the reaction principle of the present invention which improves the deposition rate by using an amine-based compound having an unshared electron pair as a catalyst is described. HfO ₂ , ZrO ₂ thin films, etc., which are materials, may be applied and used when forming by atomic layer deposition.

A semiconductor device in which an Al ₂ O ₃ thin film having a desired thickness is formed by repeating the cycle until the desired thickness is secured using T1 to T4 shown in FIGS. 3A and 3B as one cycle includes carbon atoms or hydrogen remaining in the thin film. In order to remove the atoms, it may additionally be subjected to rapid thermal processing (RTP) or plasma treatment, in which O ₂ gas or N ₂ O gas may be used as the main gas. After all the steps have been completed, after obtaining a semiconductor substrate on which an Al ₂ O ₃ thin film is formed from the reactor, the temperature of the substrate can be lowered by introducing the substrate into another reactor and cooling it.

Since the amine-based compound having a lone pair of electrons used as a catalyst in the present invention only plays a role of reducing the reaction energy without participating in a direct reaction, the self-limiting reaction which is a feature of the atomic layer deposition method is maintained as it is. It is possible to deposit Al ₂ O ₃ thin films up to the atomic level on the semiconductor substrate. In addition, according to the present invention, by using the catalyst as described above, the reaction temperature can be lowered to 300 ° C., and the required flow rate of the reaction source such as TMA and H ₂ O can be reduced by 100% or more.

Therefore, when forming an Al ₂ O ₃ thin film by the atomic layer deposition method according to the present invention, by introducing an amine-based compound having a non-covalent electron pair as a catalyst, it is possible to innovatively improve low through-put, and through this improvement Cost savings on equipment investment can also be achieved.

1 is a view schematically showing a step of depositing an Al ₂ O ₃ thin film of a semiconductor device by a conventional atomic layer deposition method.

Figure 2 is a graph showing the deposition rate according to the supply time of TMA in the Al ₂ O ₃ thin film deposition of the semiconductor device using a conventional atomic layer deposition method.

3A and 3B schematically illustrate Al ₂ O ₃ thin film deposition steps of a semiconductor device by the atomic layer deposition method according to the present invention.

4A is a view showing a reaction when pyridine is introduced as a catalyst during TMA introduction according to the atomic layer deposition method of the present invention.

4B is a view showing a reaction when pyridine is introduced as a catalyst when H ₂ O is introduced in a vapor state according to the atomic layer deposition method of the present invention.

FIG. 4C is a view showing a reaction when ammonia is introduced as a catalyst during TMA introduction according to the atomic layer deposition method of the present invention. FIG.

Claims (11)

In the method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method, A first step of introducing an aluminum source into the reactor into which the semiconductor substrate is introduced, and an amine compound having an unshared electron pair as a catalyst for a predetermined time (T1); A second step of stopping the introduction of the aluminum source and the amine compound for a predetermined time (T2); A third step of introducing an amine compound having an oxygen source and an unshared electron pair as a catalyst for a predetermined time (T3) in the reactor; And A fourth step of stopping introduction of the oxygen source and the amine compound for a predetermined time (T4); Al ₂ O ₃ thin film formation method of a semiconductor device using an atomic layer deposition method comprising a. The method of claim 1, Pyridine (C ₅ H ₅ N) or ammonia (NH ₃ ) is used as the catalyst A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. The method of claim 1, TMA (Al (CH ₃ ) ₃ ) is used as the aluminum source. A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. The method of claim 1, It is characterized by using H ₂ O or O ₃ in the vapor state as the oxygen source A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. The method of claim 1, The temperature in the reactor in the first step to the fourth step is maintained at 300 ~ 700 ℃, the pressure in the reactor is maintained at 10mTorr ~ 10Torr, characterized in that the T1 to T4 are each 10msec ~ 10sec A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. The method of claim 1, The aluminum source, the catalyst, and the oxygen source introduced into the reactor are introduced in amounts of 10 ⁹ to 10 ⁵ langmular, respectively. A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. In the method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method, Introducing a semiconductor substrate into the reactor; A second step of preheating the semiconductor substrate at 300 ° C. for 10 seconds to 10 minutes; A third step of introducing Al (CH ₃ ) ₃ and C ₅ H ₅ N into the reactor in an amount of 10 ⁹ to 10 ⁵ langmular for 10 msec to 10 sec; A fourth step of stopping introduction of Al (CH ₃ ) ₃ and C ₅ H ₅ N for 10 msec to 10 sec, and then introducing or pumping an inert gas selected from argon gas and nitrogen gas; A fifth step of introducing H ₂ O and C ₅ H ₅ N in a vapor state into the reactor in an amount of 10 ⁹ to 10 ⁵ langmular for 10 msec to 10 sec; Stopping the introduction of the H ₂ O and C ₅ H ₅ N in the vapor state for 10 msec to 10 sec, and then introducing or pumping purge with an inert gas selected from argon gas and nitrogen gas; And A seventh step of repeating the third and sixth steps; Al ₂ O ₃ thin film formation method of a semiconductor device using an atomic layer deposition method comprising a. The method of claim 7, wherein Introducing NH ₃ instead of C ₅ H ₅ N A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. The method of claim 7, wherein The temperature in the reactor in the third to sixth step is maintained at 300 ~ 700 ℃, the pressure in the reactor is characterized in that it is maintained at 10mTorr ~ 10Torr A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. The method of claim 7, wherein The reaction of the third step is the following scheme 1a or 1b     (Scheme 1a) Substrate-Al- (OH) ₂ ^* + Al (CH ₃ ) ₃ + C ₅ H ₅ N → Substrate-AlOH-O-Al (CH ₃ ) ₂ ^* + CH ₄ ↑ + C ₅ H ₅ N     (Scheme 1b) Substrate-O-Al-OH ^* + Al (CH ₃ ) ₃ + C ₅ H ₅ N → Substrate-O-Al-O-Al- (CH ₃ ) ₂ ^* + CH ₄ ↑ + C ₅ H ₅ N Where * indicates surface condition Characterized in that A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method. The method of claim 7, wherein The reaction of the fifth step is shown in Scheme 2a or 2b     (Scheme 2a) Substrate-AlOH-O-Al (CH ₃ ) ₂ ^* + H ₂ O + C ₅ H ₅ N → Substrate-Al-O-Al-OH ^* + CH ₄ ↑ + CH ₃ OH + C ₅ H ₅ N     (Scheme 2b) Substrate-O-Al-O-Al- (CH ₃ ) ₂ ^* + H ₂ O + C ₅ H ₅ N-> Substrate-O-Al-O-AlCH ₃ -OH ^* + CH ₄ ↑ + C ₅ H ₅ N Where * indicates surface condition Characterized in that A method of forming an Al ₂ O ₃ thin film of a semiconductor device using an atomic layer deposition method.