KR19990069109A - Silicon film formation method having hemispherical grain - Google Patents

Abstract

The present invention relates to a method for forming a silicon film having hemispherical grains, and discloses a method for forming an HSG silicon film using a vertical tube in which a wafer is loaded or unloaded through an opening in a lower part thereof. This method loads a plurality of wafers formed on the surface of an amorphous silicon film pattern in a vertical tube heated to an idle temperature of 500 ° C. or lower, while simultaneously raising the temperature of the vertical tube to a process temperature higher than the ambient temperature. And the silicon source gas is injected into the vertical tube heated to the process temperature to form a plurality of silicon nuclei on the surface of the amorphous silicon film pattern, and the plurality of silicon nuclei are grown while the silicon source gas is blocked. .

Description

Silicon film formation method having hemispherical grain

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of forming a hemi-spherical grain silicon layer (hereinafter referred to as an "HSG silicon film").

Among semiconductor devices, semiconductor memory devices such as DRAMs have a unit cell composed of one cell capacitor and one access transistor. DRAM cells show better characteristics as the capacity of the cell capacitor increases. Therefore, efforts have been made to fabricate cell capacitors having a large capacity within a limited area. There are various methods of increasing the capacity of the cell capacitor, and among them, a method of forming an HSG silicon film has been proposed as a method of increasing the surface area of an electrode. The HSG silicon film is a silicon film made of hemispherical grains, and the surface area of the storage electrode can be increased by forming the HSG silicon film on the surface of the storage electrode. There are two methods for forming such an HSG silicon film. One is a single sheet process which processes one wafer one by one, and the other is a batch process which processes several wafers at once. Batch-type process has the advantage of excellent productivity while the uniformity of each wafer and uniformity in the wafer is poor compared to the single sheet process.

A conventional HSG silicon film formation method for a batch process involves raising a boat containing several wafers in a vertical tube controlled at a temperature of about 565 ° C. to load the wafer into the tube and then placing the silicon in the tube loaded wafer. A seeding step of injecting a source gas to form a silicon nucleus on the wafer surface, an annealing step of growing the silicon nucleus, and lowering the boat to unload the wafer. In this case, the wafer loading step, seeding step, annealing step and unloading step are all performed at the same temperature, that is, 565 ° C. In addition, storage electrode patterns formed of an amorphous silicon layer exist on the wafer. Therefore, the silicon oxide is not uniformly formed because the natural oxide film is easily formed on the surface of the storage electrode pattern when loading the wafer. In addition, since the wafer is loaded into a tube adjusted to a high temperature of 565 ° C., crystallization of the storage electrode patterns formed of the amorphous silicon film is easily performed. Therefore, since silicon atoms are not supplied from the storage electrode pattern during the annealing step, there is a problem that the silicon nucleus is not grown. In addition, since the HSG silicon film is formed in a state where a plurality of wafers are loaded in one tube, a problem may occur in that the HSG silicon film is not locally formed according to the position of the tube. In particular, when the wafer is placed in the boat, the wafer is loaded in turn from the bottom of the boat. At this time, a thicker natural oxide film is formed on the wafer surface contained in the lower part of the boat than in the wafer surface contained in the upper part. This is because the wafer contained in the bottom of the boat heated to a high temperature of 565 ° C. is present at a high temperature for the longest time. On the other hand, when the wafer is contained in the boat from the upper portion of the boat, rather than the thickness uniformity of the natural oxide film formed on the surface of the wafer contained in the upper and lower portion of the boat is worse. This is because the tube and the top of the boat, which are kept at a high temperature of 565 ° C, are located close to each other. Therefore, it is difficult to form a uniform natural oxide film on all surfaces of the wafers loaded in the tube.

As described above, the conventional HSG silicon film forming method is not only difficult to form a uniform HSG silicon film for each wafer, but also has a problem in that the HSG silicon film is not locally formed.

It is an object of the present invention to provide a HSG silicon film formation method capable of minimizing defects not only on the surface of one storage electrode pattern, but also on one wafer as a whole and all wafers loaded in a tube.

1 is a schematic diagram of a deposition apparatus for a silicon film having hemispherical grains used in the present invention.

2 is a schematic diagram showing in detail the process module of FIG.

3 is a process recipe for forming a silicon film having hemispherical grains according to the present invention.

In order to achieve the above object, the present invention provides a method for forming an HSG silicon film using a vertical tube in which a wafer is loaded or unloaded through a lower portion, wherein the vertical type is heated to an idle temperature of 500 ° C. or less. Raising the temperature of the vertical tube to a process temperature higher than the ambient temperature while simultaneously loading a plurality of wafers formed on the surface with an amorphous silicon film pattern in the tube; and a silicon source in the vertical tube heated to the process temperature. And injecting a gas to form a plurality of silicon nuclei on the surface of the amorphous silicon film pattern, and growing the plurality of silicon nuclei while the silicon source gas is blocked.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a schematic diagram of the deposition equipment of the HSG silicon film used in the present invention.

Referring to FIG. 1, the HSG silicon film deposition apparatus includes a first cassette module CM1 in which a cassette containing a wafer to be subjected to a predetermined process is placed, and a second cassette module in which a cassette containing a wafer at which a predetermined process is completed is placed. And a transfer module TM for transferring the wafers of the first cassette module CM1 to the process module PM. The transfer module TM may also transfer wafers having a predetermined process from the process module PM to the second cassette module CM2.

FIG. 2 is a schematic view showing the process module PM of FIG. 1 in detail.

Referring to FIG. 2, the process module PM may include a plurality of vertical tubes TB having a lower opening and surrounding the outside of the side wall of the vertical tube TB and adjusting a temperature of the vertical tube TB. A coil C and a boat B for loading or unloading the plurality of wafers W through the opening of the vertical tube TB. The upper part of the vertical tube (TB) is provided with a gas injection tube (I) for injecting a predetermined gas, for example, silicon source gas, such as a silane gas, into the vertical tube (TB), the vertical tube The lower part of the TB is provided with a gas discharge tube O for discharging the silicon source gas injected into the vertical tube TB and the air in the vertical tube T. The plurality of wafers W contained in the boat B are loaded or unloaded into the vertical tube TB by moving the boat B up and down. The coils C are classified according to the position of the vertical tube TB. Preferably, the upper coils T, the upper middle coil MT, the lower middle coil MB, and the lower coil B are disposed. Separated by.

3 is a process recipe for explaining a method of forming an HSG silicon film according to the present invention.

A method of forming an HSG silicon film according to the present invention will be described with reference to FIGS. 1, 2, and 3. First, a storage electrode pattern made of an amorphous silicon film is formed on a semiconductor wafer, and a plurality of semiconductor wafers on which the storage electrode pattern is formed are contained in a wafer cassette. Next, the wafer cassette containing the plurality of semiconductor wafers on which the storage electrode pattern is formed is moved to the first cassette module CM1. Subsequently, the vertical tube TB of the process module PM is heated to an idle temperature (Ti) of 500 ° C. or less, for example, a temperature of 480 ° C., and a silicon source gas inside the vertical tube TB, For example, a precoating step of injecting a silane gas is performed (1). Then, the boat B in the vertical tube TB is lowered, and the semiconductor wafers W of the first cassette module CM1 are transferred to the slots of the boat B through the transfer module TM. (3). At this time, the semiconductor wafers W are transferred to be filled from the bottom slot of the boat B, which is the part located farthest from the vertical tube TB continuously being heated by the heating coil C. This is to minimize the phenomenon that a natural oxide film is formed on the surfaces of all the semiconductor wafers filled in each slot of the boat B. FIG.

When the plurality of semiconductor wafers W are mounted on the boat B, the boat B is raised to load the semiconductor wafers W into the vertical tube TB, and at the same time, the vertical tube TB ) Is raised to a process temperature Tp higher than the atmospheric temperature Ti (5). In this case, the process temperature (Tp) is preferably adjusted differently depending on the position of the vertical tube (TB). For example, the heating coil T surrounding the upper region of the vertical tube TB, the heating coil MT surrounding the upper middle region, the heating coil MB surrounding the lower middle region, and surrounding the lower region. By independently controlling the heating coil B, the upper region, the upper region, the lower region and the lower region of the vertical tube TB are heated to temperatures of 565 ° C, 565 ° C, 566 ° C and 568 ° C, respectively. It is preferable. The above temperature profile is set to be suitable for the structure of the process module PM shown in FIG. 2. Therefore, the temperature profile may be changed according to the structure of the vertical tube TB. In the temperature profile, the reason why the lower temperature of the vertical tube TB is set to be the highest is that the natural oxide film formed on the surface of the storage electrode pattern of the semiconductor wafer W positioned below the boat B is the boat B. This is because it is formed thicker than the natural oxide film formed on the surface of the storage electrode pattern of the semiconductor wafer (W) positioned on the upper side of). This transfers the semiconductor wafers W to be filled from the bottom slot of the boat B as described above, so that the semiconductor wafer W located below the boat B is brought to the atmospheric temperature Ti. This is because it is in contact with the heated boat B for the longest time. Thus, in subsequent seeding and annealing steps, more energy is applied to the semiconductor wafer W positioned below the boat B to form a uniform silicon nucleus on all the semiconductor wafers W in the boat B. And for the growth of the silicon nucleus.

By injecting a silicon source gas, for example, a silane gas, through the gas injection pipe I into the vertical tube TB controlled by the temperature profile, the surface of all the semiconductor wafers W, that is, all the storage electrode patterns. A seeding step is performed to form a uniform silicon nucleus on the surface of (7). Subsequently, an annealing step of growing the silicon nucleus is performed by blocking the silicon source gas (9). At this time, the silicon nucleus is grown by receiving silicon atoms from the inside of the storage electrode pattern, that is, the amorphous silicon film, thereby forming an HSG silicon film having hemispherical grains on the surface of the storage electrode pattern. After the HSG silicon film is formed, the boat B is lowered (11). Subsequently, the temperature of the vertical tube TB is lowered back to the atmospheric temperature Ti, and the semiconductor wafers W in the boat B are transferred to the second cassette module CM2 through the transfer module TM ( 13, 15).

The present invention is not limited to the above embodiments, and modifications and improvements are possible at the level of those skilled in the art.

As described above, according to the present invention, in a batch process of forming an HSG silicon film using a vertical tube, a natural oxide film is formed on a surface of a semiconductor wafer by loading semiconductor wafers at a low temperature of 500 ° C. or lower before forming a silicon nucleus. This phenomenon can be suppressed as much as possible. In addition, by performing a seeding step of forming a silicon nucleus and an annealing step of growing a silicon nucleus at a high temperature of 500 ° C. or higher, HSG having a uniform hemispherical grain and minimizing defects in which no HSG silicon film is locally formed on all semiconductor wafer surfaces. A silicon film can be formed.

Claims (5)

A method of forming an HSG silicon film using a vertical tube in which a wafer is loaded or unloaded through a lower portion, While loading a plurality of wafers having an amorphous silicon film pattern formed on a surface of the vertical tube heated to an idle temperature of 500 ° C. or lower, the temperature of the vertical tube is raised to a process temperature higher than the atmospheric temperature. Making a step; Injecting a silicon source gas into a vertical tube heated to the process temperature to form a plurality of silicon nuclei on the surface of the amorphous silicon film pattern; And Growing the plurality of silicon nuclei in a state in which the silicon source gas is blocked. The method of claim 1, wherein the atmospheric temperature is 480 ° C. The method of claim 1, wherein the process temperature is controlled to be different from each other depending on the position of the vertical tube. The process temperature of claim 3, wherein the process temperature is a temperature of an upper region of the vertical tube, a temperature of an upper middle region, a temperature of a middle lower region, and a temperature of a lower region of 565 ° C., 565 ° C., 566 ° C., and 568, respectively. HSG silicon film forming method characterized in that it is adjusted to be heated to ℃. The method of claim 1, wherein the silicon source gas is a silane gas.