JP2005340288A - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device for reforming the surface of the damage layer of an interlayer insulating film, which is formed by dry etching, especially removing moisture remaining in a low dielectric constant insulating film (Low-k film) being the interlayer insulating film and restoring damage by plasma. <P>SOLUTION: The manufacturing method of the semiconductor device has a process for patterning the interlayer insulating film 4 formed in the semiconductor substrate 2 by dry etching, a process for cleaning the semiconductor substrate 2 having the interlayer insulating film 4, a process for drying the semiconductor substrate 2 having the interlayer insulating film 4 under reduced pressure, and a process for reforming the surface of the damage layer 10 in the interlayer insulating film 4 by dry etching. Drying under reduced pressure and surface reforming are continuously performed without exposing to atmosphere. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device that performs surface modification of a damaged layer of an interlayer insulating film.

With the miniaturization of LSIs (Large Scale Semiconductor Integrated Circuits), the speed of elements and the reduction of power consumption are progressing. At that time, in the formation of wiring, in order to reduce wiring resistance and secure wiring capacity, a low-k film is generally used for wiring using copper (Cu) or an insulating film between wirings (hereinafter referred to as an interlayer insulating film). The use of an insulating film having a low dielectric constant, which is called, has been studied. In recent years, low-k films have been made to have a low dielectric constant, and the development of porous materials has been accelerated.
In this wiring formation using copper, a damascene method is used to first form a wiring-shaped groove in the low-k film, and the groove is filled with a barrier metal and copper plating, and then excess copper on the surface is CMPed. It is a general method to remove and form by (chemical mechanical polishing).
At this time, in order to remove processing residues remaining in the low-k film during dry etching, cleaning is performed in combination with a rinsing process such as a chemical solution and pure water. In the single wafer apparatus after the cleaning, the barrier metal and copper are embedded after drying by spin-off as a drying process.

In the cleaning process in the wiring formation process, moisture remaining on the surface of the Low-k film due to the porous structure of the Low-k film is removed by the drying process at the time of cleaning, but the moisture at the time of cleaning is absorbed inside the film. Once removed, it becomes difficult to remove. Since such moisture remains in the low-k film, the breakdown voltage characteristics of the insulating film are deteriorated and the dielectric constant is increased.
In addition, due to plasma damage of the low-k film at the time of processing by dry etching, damage to the film due to destruction of the molecular structure at the end of the low-k film causes an increase in the dielectric constant, and the device performance Has an adverse effect.

In recent years, as a substrate drying technique for a single wafer cleaning apparatus, a drying method for reducing the pressure has been devised. For example, as in Patent Document 1, the substrate surface is heated and vaporized as water vapor from the substrate to the outside, and then removed from the substrate by subjecting the vaporized water to a reduced pressure treatment. By using this reduced pressure drying method, it is possible to remove moisture remaining in the low-k film.
In order to suppress damage to the Low-k film due to dry etching, for example, in Patent Document 2, silylation is performed by performing a treatment with HMDS (hexamethyldisilazane) or the like on a damaged layer. Thus, a method for modifying the damaged layer has been proposed.

JP 2003-174007 A JP 2000-188331 A

However, these methods described above have the following problems.
(1) The moisture remaining in the low-k film can be removed only by using the reduced-pressure drying method. However, what is the change that restores the molecular structure of the damaged layer by the plasma of the low-k film? Is also impossible because Therefore, an increase in dielectric constant is inevitable.
(2) Since silylation by HMDS treatment to a damaged layer is generally easy to absorb moisture due to the hydrophilic nature of the damaged layer, moisture in the atmosphere is adsorbed from this hydrophilic damaged layer to Low-k It will be taken into the membrane. Therefore, when this method is used, the steps to be introduced are limited.
(3) When a damaged layer is present in the Low-k film and the damaged layer is silylated by HMDS treatment while retaining moisture taken into the Low-k film from the damaged layer, this damaged layer When the film properties are modified, it changes to hydrophobic. Therefore, it becomes difficult to desorb moisture remaining in the Low-k film to the outside.

  In view of the above points, the present invention is directed to surface modification of a damaged layer of an interlayer insulating film made by dry etching, in particular, moisture remaining in a low dielectric constant insulating film (Low-k film) that is an interlayer insulating film. The present invention provides a method of manufacturing a semiconductor device that recovers damage caused by removal and plasma.

  A method of manufacturing a semiconductor device according to the present invention includes a step of patterning an interlayer insulating film formed on a semiconductor substrate by dry etching, a step of cleaning a semiconductor substrate having an interlayer insulating film, and a pressure reduction of the semiconductor substrate having an interlayer insulating film. The method includes a drying step and a step of modifying the surface of the damaged layer of the interlayer insulating film by dry etching, and the reduced-pressure drying and the surface modification are continuously performed without being exposed to the atmosphere.

The reduced-pressure drying treatment and the surface modification treatment can be performed in the same apparatus.
Alternatively, the reduced-pressure drying process and the surface modification process can be performed by different apparatuses.

As a material used for the surface modification, it is preferable to use a silazane compound.
The silazane compound is preferably a compound composed of a Si-n bond and a CH3 bond.
As the interlayer insulating film, a low dielectric constant insulating film is preferably used.

  In the method of manufacturing a semiconductor device of the present invention, an interlayer insulating film formed on a semiconductor substrate is patterned by dry etching, washed, and then heat-treated under reduced pressure as substrate drying. Moisture absorbed inside is removed. After drying under reduced pressure, the surface of the damaged layer of the interlayer insulating film is continuously modified by dry etching without being exposed to the air, so that the surface of the damaged layer is modified without adsorbing moisture in the air. Is called.

By continuously performing the drying under reduced pressure and the surface modification in the same apparatus, the semiconductor substrate having the interlayer insulating film can be processed without being exposed to the atmosphere. Reabsorption of water does not occur.
When the drying under reduced pressure and the surface modification are successively performed by different apparatuses, a buffer unit that prevents the semiconductor substrate having an interlayer insulating film from being exposed to the atmosphere is provided between both apparatuses. Also in this case, reabsorption of moisture does not occur between substrate drying and surface modification.

  By using a silazane compound, preferably a compound composed of a Si-n bond and a CH3 bond, as the material used for the surface modification, the damaged layer of the interlayer insulating film is silylated.

  According to the method for manufacturing a semiconductor device of the present invention, after patterning and cleaning the interlayer insulating film by dry etching, the moisture in the interlayer insulating film is continuously removed by drying under reduced pressure without being exposed to the atmosphere, and the surface of the damaged layer Since the modification is performed, it is possible to suppress the breakdown voltage deterioration of the interlayer insulating film and the increase of the dielectric constant due to moisture. Therefore, the yield of the semiconductor device is improved, and the semiconductor device with improved reliability of the semiconductor device can be manufactured.

When continuously drying under reduced pressure and modifying the surface of a damaged layer in the same apparatus, these treatments can be performed without exposing the semiconductor substrate having an interlayer insulating film to the atmosphere. Therefore, it is possible to manufacture a semiconductor device with high yield and high reliability by suppressing the breakdown voltage degradation and the increase in dielectric constant of the interlayer insulating film.
Even when vacuum drying and surface modification of damaged layers are carried out continuously without exposing them to the atmosphere with different devices, it is possible to suppress deterioration of the dielectric breakdown voltage and increase of dielectric constant of the interlayer insulation film, and to improve the yield and reliability. The device can be manufactured.

When the damage layer of the interlayer insulating film is silylated with a silazane compound, preferably a compound composed of a Si—n bond and a CH 3 bond, the surface modification of the damage layer can be performed satisfactorily.
By using a low dielectric constant insulating film as the interlayer insulating film, the wiring capacitance can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  1a to 2h show an embodiment of a method for manufacturing a semiconductor device according to the present invention, that is, a manufacturing method for successively processing substrate drying by a reduced pressure drying method and silylation by HMDS processing in wiring formation.

  First, as shown in FIG. 1a, an etching stopper film 3 is formed on a silicon substrate 2 of a semiconductor substrate on which required semiconductor elements are formed. As the stopper film 3, a silicon nitride film system (bonding of Si and N) or an SiC film system (bonding of Si and C) is formed.

Next, as shown in FIG. 1B, an interlayer insulating film 4 is formed on the stopper film 3. In this example, a low-k film that is a low dielectric constant insulating film is formed as the interlayer insulating film 4 (hereinafter, the interlayer insulating film is referred to as a low-k film 4). In this example, the low-k film 4 is formed of a SiOC-based CVD film having a chemical structure.
The low-k film 4 is a low dielectric constant material mainly composed of silicon, such as xerogel (porous silica), silicon oxycarbide film (SiOC (H)), methyl silisisquioxane (MSQ), hydrosilisisquioxane (HSQ). ), The same polymer (HMSQ), and the like can be used.

  Next, as shown in FIG. 1 c, a silicon oxide film 5 serving as a pattern mask is formed on the low-k film 4, and a photoresist film 6 a is further applied on the silicon oxide film 5.

  Next, as shown in FIG. 1d, a photolithography process and an etching process are performed on the photoresist film 6a and the silicon oxide film 5 to form a pattern of the wiring groove (that is, a via hole for wiring connection). Opening 7a is formed. 6b is a resist layer after photolithography.

  Next, as shown in FIG. 1e, wiring grooves 7b are formed in the low-k film 4 by dry etching using the resist layer 6b and the silicon oxide film 5 as a mask. After the dry etching, the residue 9 adheres in the wiring groove 7b. In addition, a damaged layer 10 having a molecular structure changed due to plasma damage is formed near the surface layer of the low-k film 4 in the wiring trench 7b.

  Next, as shown in FIG. 2f, a cleaning process for removing the etching residue 9 by dry etching is performed. This cleaning process is performed by transporting the dry-etched silicon substrate 3 into, for example, a single wafer cleaning apparatus, and combining a rinsing process such as a chemical solution and pure water. At this time, moisture 11 is absorbed into the low-k film 4 through the damage layer 10. As shown in FIG. 3a, the chemical structure in the low-k film 4 is a state in which H2O which is moisture 11 is contained in the porous body. Note that FIG. 3 a corresponds to the region A that has absorbed moisture in the inner wall portion of the wiring groove 7 b in FIG. 2 f and shows the chemical structure of the damage layer 10 and the low-k film 4.

  At this time, only the resist layer 6b may be used as a pattern mask, and the resist layer 6b is removed by ashing after dry etching.

  Next, with respect to the semiconductor substrate 2 having the low-k film 4 after cleaning, the damage layer 10 is removed by removing moisture by drying under reduced pressure in the same apparatus, for example, a drying processing chamber (chamber) and processing with a silazane compound. Surface modification, so-called silylation, is performed.

  That is, as shown in FIG. 2g, the moisture 11 in the Low-k film 4 is passed through the damage layer 10 by drying under reduced pressure in the processing chamber of the single wafer cleaning apparatus, that is, by heat treatment in reduced pressure. To desorb. That is, as shown in FIG. 3B (corresponding to the region A in FIG. 2G), the chemical structure is obtained by removing H 2 O from the damaged layer 10 and the low-k film 4.

  Next, as shown in FIG. 2h, the treatment of the silazane compound, HMDS (hexamethyldisilazane), which is a compound composed of a Si—n bond and a CH3 bond in this example, continuously in the same processing chamber as the vacuum drying treatment. To recover the damaged layer 10 by silylation. As shown in FIG. 4, the bonded Si—OH (see the left figure in FIG. 4) of the damaged layer 10 is subjected to HMDS treatment, so that the damaged layer 10 becomes Si—O—Si— (CH 3) 3 (in FIG. 4). (See the figure on the right). The reaction formula is shown in Chemical Formula 1.

  In the surface modification treatment of the damaged layer 10, HMDS treatment is performed by introducing HMDS gas (a vaporized HMDS liquid) into the treatment chamber under reduced pressure after drying under reduced pressure. When HMDS processing cannot be performed under reduced pressure, the processing chamber is purged with an inert gas (for example, N 2 gas, Ar gas, etc.), and HMDS gas is introduced into the processing chamber using the inert gas as a carrier gas. Then, the damaged layer 10 is silylated by reacting the HMDS gas with the damaged layer 10. At this time, the ratio of carrier gas to HMDS gas, that is, carrier gas: HMDS gas, can be in the range of 20: 1 to 5: 1.

  Next, although not shown, after selectively removing the stopper layer 3 in the wiring groove 7b by etching, a conductive layer is formed so as to fill the wiring groove 7b and patterned to connect the wiring in the wiring groove 7b. And wiring are formed. For example, using a damascene method, a copper (Cu) barrier film is formed on the surface including the wiring groove, and patterned to form an upper layer wiring connected to the lower layer electrode (or wiring) through the wiring connecting portion in the wiring groove 7b. . In the case of forming a multilayer wiring, the steps of FIGS. 2b to 2h are repeated. In this way, a semiconductor device in which a target wiring is formed is obtained.

  In the semiconductor device manufacturing method according to the above-described embodiment, the reduced pressure drying and the surface modification are performed in the same processing chamber of the same apparatus. In addition, in the same apparatus, the reduced pressure adjacent to each other via the shutter unit. It is also possible to perform drying under reduced pressure and surface modification continuously in the drying treatment chamber and the surface modification treatment chamber without being exposed to the atmosphere. In this case, the HMDS liquid is supplied into the surface reforming chamber through the nozzle and the HMDS liquid and the damaged layer 10 are reacted, or the HMDS gas is supplied through the supply pipe to react the HMDS gas and the damaged layer 10. . Alternatively, in the same apparatus, it is possible to perform surface modification in the cleaning treatment chamber after drying under reduced pressure in the drying treatment chamber.

In the semiconductor device manufacturing method of the present embodiment described above, the cleaning process, the reduced-pressure drying process, and the HMDS process are continuously performed in the same apparatus, but each process may be performed in separate apparatuses.
When the vacuum drying process and the HMDS process are performed by separate processing apparatuses, a buffer unit capable of transporting between the apparatuses without exposing the semiconductor substrate to be processed to the atmosphere is provided between the vacuum drying process apparatus and the HMDS processing apparatus. To make. In this embodiment, after the Low-k film 4 in which the wiring trench is formed is subjected to a water cleaning process, the semiconductor substrate 2 having the Low-k film 4 is stored in an apparatus for performing a vacuum drying process and dried under a reduced pressure. Thereafter, the semiconductor substrate 2 is transported to an apparatus for performing a surface modification treatment through a buffer unit, and the damaged layer 10 of the Low-k film is recovered by HMDS treatment by introducing HMDS liquid or HMDS gas. By continuously processing in this manner, moisture is not reabsorbed into the low-k film via the damaged layer after drying under reduced pressure.

  According to the method for manufacturing a semiconductor device according to the present embodiment, low-pressure drying and HMDS processing are continuously performed on the semiconductor substrate 2 after being cleaned in the same device or in a different device without touching the atmosphere. The moisture layer absorbed by the HMDS treatment can be recovered by silylation without releasing the moisture absorbed in the −k film 4 and again absorbing the moisture in the low-k film 4. Therefore, it is possible to suppress an increase in the breakdown voltage and dielectric constant of the low-k film 4 due to water. Further, the plasma damage of the low-k film 4 during dry etching can be recovered by the HMDS process.

Next, the superiority of the manufacturing method of the semiconductor device according to the present embodiment will be described based on the measurement data of FIGS.
FIG. 5 is a graph showing the respective moisture-containing states when the low-k film is untreated, washed only, washed and dried under reduced pressure, washed and silylated. In FIG. 5, the vertical axis represents moisture content, and the horizontal axis represents heating temperature. It shows a state in which as the heating temperature is raised, the water evaporates and moisture contained in the film is released, and then the evaporation decreases.
According to the graph of FIG. 5, the moisture contained in the film is extremely small when the curve (a) is untreated. In the state of only the cleaning process of the curve (b), the film contains a large amount of moisture. In the case where the silylation treatment is performed after the cleaning of the curve (d), there is little separation of moisture, and much moisture remains in the film. When drying under reduced pressure after washing the curve (c), moisture in the film is released. As can be seen from this graph, moisture removal from the film cannot be sufficiently performed only by the silylation treatment after washing. On the other hand, when drying under reduced pressure after washing treatment, it is recognized that water in the film is sufficiently removed and the film is surely dried.

FIG. 6 is a graph obtained by measuring the dielectric constant of the interlayer insulating film of the substrate while changing the processing state of the substrate.
First, the dielectric constant f1 of the unprocessed semiconductor device is the lowest value.
Next, the dielectric constant f2 after the semiconductor device is subjected to the cleaning process is a value that is increased about three times as compared with the unprocessed state.
Next, the dielectric constant f3 after the semiconductor device is subjected to the HMDS process after the cleaning process is slightly decreased as compared with the dielectric constant f3 after the cleaning process.
Next, after the cleaning process, the substrate without drying under reduced pressure rises to the same dielectric constant f2 after the cleaning process and becomes a dielectric constant f4.
At this time, after the cleaning treatment, the substrate with reduced pressure drying has a low dielectric constant e5 which is equivalent to the dielectric constant f1 of the untreated substrate.

FIG. 7 is a graph obtained by measuring the dielectric constant of the interlayer insulating film of each substrate when the processing state of the substrate is changed and left in the air for 7 days thereafter. However, unprocessed substrates that are not left in the atmosphere for 7 days are used.
The unprocessed substrate has the lowest dielectric constant g1.
Next, the dielectric constant g2 of the substrate after the cleaning process becomes a high dielectric constant g2.
Next, the dielectric constant g3 of the substrate subjected to the HMDS process after the cleaning process is slightly lower than the dielectric constant g2 of the substrate after the cleaning process.
After the cleaning treatment, the dielectric constant g4, which is only dried under reduced pressure, increases by absorbing moisture while left in the atmosphere for 7 days.
After the cleaning process according to the present embodiment, the dielectric constant g5 of the substrate dried under reduced pressure and subjected to HMDS treatment can maintain a low dielectric constant equivalent to the dielectric constant g1 of the untreated substrate.

  From the above experimental results, it is possible to reduce the moisture content and, further, to reduce the dielectric constant, by continuously performing the drying under reduced pressure and the silylation by the HMDS treatment after the cleaning of the interlayer insulating film of the semiconductor substrate.

a to e are process diagrams showing an embodiment of a method of manufacturing a semiconductor device according to the present invention (part 1). f to h are process diagrams showing an embodiment of a method of manufacturing a semiconductor device according to the present invention (part 2). a is a chemical structural formula showing the structure in the Low-k film corresponding to FIG. b is a chemical structural formula showing the structure in the Low-k film corresponding to FIG. It is a chemical structural formula showing the structure in the Low-k film corresponding to FIG. 6 is a graph comparing the relationship between the heating temperature and the moisture content in the inter-wiring insulating film of the semiconductor device using the method for manufacturing a semiconductor device according to the present invention and a conventional semiconductor device. It is the graph which compared the dielectric constant in the insulating film between wiring of a semiconductor device. 7 is a graph comparing the dielectric constant in the inter-wiring insulating film of the semiconductor device using the semiconductor device manufacturing method according to the present invention and the conventional semiconductor device, which is left in the atmosphere for 7 days.

Explanation of symbols

2 .. Silicon substrate 3. Stopper film 4.. Interlayer insulating film (Low-k film) 5... Silicon oxide film 6 a .. Photoresist film 6 b .. Resist layer 7 a. 7b..Wiring groove, 9..Residue, 10..Damage layer, 11..Moisture,

Claims (6)

Patterning the interlayer insulating film formed on the semiconductor substrate by dry etching;
Cleaning the semiconductor substrate having the interlayer insulating film;
Drying the semiconductor substrate having the interlayer insulating film under reduced pressure;
Modifying the surface of the damaged layer of the interlayer insulating film by the dry etching,
The method of manufacturing a semiconductor device, wherein the drying under reduced pressure and the surface modification are continuously performed without being exposed to the atmosphere. The method of manufacturing a semiconductor substrate according to claim 1, wherein the drying under reduced pressure and the surface modification are performed in the same apparatus. The method for manufacturing a semiconductor substrate according to claim 1, wherein the reduced-pressure drying and the surface modification are performed by different apparatuses. The method for manufacturing a semiconductor substrate according to claim 1, wherein the material used for the surface modification is a silazane compound. The method of manufacturing a semiconductor substrate according to claim 4, wherein the silazane compound is a compound composed of a Si—n bond and a CH 3 bond. The method of manufacturing a semiconductor device according to claim 1, wherein the interlayer insulating film is a low dielectric constant insulating film.

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