JP3846678B2 - Low slip wafer manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
Method of manufacturing of the present invention is low slip degree wafers, details on standing in a vacuum heating furnace, a method for producing a low slip of the wafer difficult to skid even if a predetermined heat treatment.
[0002]
[Prior art]
During the device manufacturing process, there are various reduced-pressure heating processes for heating a silicon wafer placed in a vacuum chamber in a reduced pressure state. For example, it is a process of growing an epitaxial layer on the surface of a silicon wafer by a low pressure CVD method using a low pressure CVD furnace.
In addition, among the silicon wafers processed here, there is a silicon wafer in which the back surface of the wafer is covered with a low-temperature silicon oxide film (LTO film) or a polysilicon film.
[0003]
Next, a wafer manufacturing method according to the conventional means will be described with reference to the flow sheet of FIG. This manufacturing method is for a silicon wafer whose back surface is covered with a low-temperature silicon oxide film.
First, in the slicing step (S301), the silicon wafer is sliced from the ingot. Next, in the chamfering step (S302), the outer peripheral portion of the silicon wafer is chamfered. In the subsequent lapping step (S303), lapping is performed on both the front and back surfaces of the silicon wafer using a lapping machine. Further, in the next etching step (S304), the wrapped wafer is immersed in a predetermined etching solution (mixed acid or alkali) to remove distortion during lapping, distortion during chamfering, and the like.
[0004]
Thereafter, the silicon wafer at a temperature of 420 ° C. to CVD process, to form a low-temperature silicon oxide film on the wafer back surface (S305). Next, the silicon wafer is bonded to the carrier plate using wax, and the surface of the wafer is mirror-polished (S307). Then, after removing the wax and the like adhering to the back surface of the wafer, a final finish cleaning (S308) is performed. The mirror polishing may be performed without wax.
[0005]
[Problems to be solved by the invention]
However, as described above, when the wafer to be heated under reduced pressure is a silicon wafer with a low-temperature silicon oxide film, if the silicon wafer is left on the stationary stage in the vacuum chamber and then heat-treated, the stationary stage is The wafer may move naturally.
This phenomenon occurs when gas (water vapor) is generated from the back surface of the low-temperature silicon oxide film due to heat during reduced pressure heating. In other words, the generation of this gas creates a gap between the silicon wafer and the wafer stationary stage. As a result, the wafer becomes easy to move, and the heat generated in the furnace is added to the wafer, causing the wafer to slip. It will be done.
The cause of water vapor from the surface of the low temperature silicon oxide film is
SiH ₄ + 2O ₂ → SiO ₂ + 2H ₂ O
This is due to desorption of H ₂ O taken into the film when the reaction occurs.
[0006]
Also in the case of a silicon wafer with a polysilicon film, gas is generated from the surface of the polysilicon film due to heat during heat treatment. In this case, hydrogen gas is used. For this reason, the silicon wafer is likely to slide sideways as well.
In this case, the cause of hydrogen generation is
SiH ₄ → Si + 2H ₂
This is due to the desorption of H ₂ taken into the film when it reacts with.
[0007]
Therefore, the inventor forms a low-temperature silicon oxide film or a polysilicon film and then degasses (removes water vapor or hydrogen) by heating the silicon wafer at a predetermined temperature in advance. In this device process, etc., it was found that even if a silicon wafer was placed on a stationary stage in a reduced pressure heating furnace and heat treatment was performed, it was difficult to cause skidding, and the present invention was completed.
[0008]
OBJECT OF THE INVENTION
An object of the present invention is to provide a method for producing a low-slip wafer that hardly causes a side slip even if it is left in a reduced pressure heating furnace and subjected to a predetermined heat treatment after the wafer is produced .
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a step of forming a gas generating film in which gas is generated by heat at the time of heat treatment of the semiconductor wafer on the back surface of the semiconductor wafer; It is a method for producing a low-slipping wafer comprising a step of performing a degassing process of heating for more than a minute, and a step of polishing the degassed semiconductor wafer surface by 5 to 15 μm .
Examples of the semiconductor wafer include a silicon wafer and a gallium arsenide wafer.
The surface of the semiconductor wafer on which the gas generating film is formed is not limited. However, it is usually the back side of the wafer.
[0010]
The kind of gas generating film is not limited. For example, a low-temperature silicon oxide film, a polysilicon film, a TEOS film, and the like can be given.
The degassing process may be performed at any time after the gas generating film is formed on the semiconductor wafer. It may be before surface polishing, after surface polishing, or after device formation.
The temperature of the degassing process varies depending on the atmospheric pressure in the furnace. If it is less than 100 degreeC, degassing is inadequate and the gas taken in in the film | membrane cannot escape.
[0011]
A preferable time for the degassing treatment is 2 to 10 minutes. If it is less than 2 minutes, degassing is insufficient, and the gas taken into the film cannot be completely removed.
[0012]
The invention according to claim 2 is the method for producing a low slip wafer according to claim 1, wherein the heating temperature during the degassing process is set to 450 ° C. or higher when the degassing process is performed under reduced pressure .
Here, the reduced pressure refers to several / 1000 to several Torr. The preferable heating temperature at the time of this reduced pressure heating is 450-700 degreeC.
When the semiconductor wafer is left in the vacuum chamber and heated under reduced pressure, the type of the reduced pressure heating furnace is not limited.
[0013]
Invention of Claim 3 is a manufacturing method of the low-slipness wafer of Claim 1 which made the heating temperature at the time of a degassing process 700 degreeC or more, when the said degassing process is a normal pressure heating. .
A preferable heating temperature at the normal pressure heating is 700 to 1000 ° C.
[0014]
The invention described in claim 4 is the method for producing a low slip wafer according to any one of claims 1 to 3, wherein the gas generating film is a low temperature silicon oxide film .
[0015]
The invention according to claim 5 is the method for producing a low slip wafer according to any one of claims 1 to 3, wherein the gas generating film is a polysilicon film .
[0016]
[Action]
According to the present invention, a semiconductor wafer is placed on a stationary stage installed in a vacuum chamber of a reduced pressure heating furnace with the surface on the gas generating film side as a mounting surface, and then a predetermined reduced pressure heat treatment is performed. At this time, since the gas generating film has been degassed in advance, almost no gas is generated from the exposed surface of the gas generating film during heating under reduced pressure. As a result, the semiconductor wafer is kept in close contact with the stationary stage. Therefore, even if the semiconductor wafer is beaten by heat during heating in the furnace, the wafer is unlikely to slip.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a flow sheet showing a method for manufacturing a low slip wafer according to one embodiment of the present invention. FIG. 2 is a sectional view of a low slip wafer according to an embodiment of the present invention.
As shown in FIG. 1, in one embodiment of the present invention, the process is roughly performed through slicing, chamfering, lapping, etching, LTO film (low temperature silicon oxide film) formation, degassing treatment, polishing, and cleaning. A low-slip wafer is produced. Hereinafter, each process will be described in detail.
[0018]
The silicon ingot pulled up by the CZ method is sliced into an 8-inch silicon wafer having a thickness of about 860 μm in the slicing step (S101).
Next, in the chamfering step (S102), the peripheral edge of the sliced wafer is chamfered into a predetermined shape using a chamfering grindstone. As a result, the peripheral edge of the silicon wafer is formed into a predetermined rounded shape (for example, a MOS type chamfered shape).
Next, the chamfered silicon wafer is lapped in a lapping step (S103). In this lapping process, a silicon wafer is placed between lap surface plates kept parallel to each other, and a wrap liquid, which is a mixture of alumina abrasive grains, a dispersant and water, is placed between the lap surface plate and the silicon wafer. Pour. Then, both surfaces of the wafer are mechanically wrapped by rotating and sliding under pressure. The wrap amount of the silicon wafer is about 40 to 80 μm in total on both the front and back surfaces of the wafer.
[0019]
Next, this wrapped wafer is etched (S104). Specifically, the silicon wafer is immersed in a mixed acid solution (normal temperature to 50 ° C.) in which hydrofluoric acid and nitric acid are mixed.
Then, this etched wafer is inserted into a thermal oxidation furnace and heated at a low temperature of 420 ° C. for 15 to 60 minutes to form a low-temperature silicon oxide film having a thickness of about 0.3 to 1.0 μm on the entire surface of the wafer. Form (S105).
Thereafter, the silicon wafer covered with the low-temperature silicon oxide film is heated at a predetermined temperature to be degassed (S106). This degassing process is performed by inserting the silicon wafer with the low-temperature silicon oxide film into a reduced pressure heating furnace, and then heat-treating the furnace in the furnace at a heating temperature of 450 ° C. for a heating time of 5 minutes.
Then, the surface of the degassed silicon wafer is polished (S107). The amount of polishing at this time is 5 to 15 μm which can remove the low-temperature silicon oxide film on the wafer surface and the waviness on the wafer surface during etching.
Thereafter, a cleaning step (S108) is performed. Specifically, RCA cleaning is performed.
Through such a manufacturing process, a silicon wafer (low slipperiness wafer) W from which the low temperature silicon oxide film Wa has been degassed is manufactured (see FIG. 2).
[0020]
As described above, since the gas component in the low-temperature silicon oxide film Wa is previously removed from the silicon wafer W, for example, when an epitaxial layer is grown on the surface of the silicon wafer W by the low pressure CVD method at the time of device fabrication, the temperature is low. Little gas (water vapor) is generated from the surface of the silicon oxide film Wa. As a result, even if the low-slip wafer W is beaten by the heat in the low-pressure CVD furnace, it does not easily skid on the stationary stage in the vacuum chamber installed in the furnace.
[0021]
【The invention's effect】
According to the present invention, since the semiconductor wafer is degassed in advance during the wafer manufacture, the gas generating film is degassed. Almost no gas is generated. As a result, even if the wafer is rolled by the heat during the heat treatment, the semiconductor wafer is less likely to cause skidding.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing a method for manufacturing a low slip wafer according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a low slip wafer according to an embodiment of the present invention.
FIG. 3 is a flow sheet showing a method of manufacturing a semiconductor wafer according to conventional means.
[Explanation of symbols]
W Silicon wafer (low slip wafer),
Wa Low temperature silicon oxide film (gas generating film).

Claims (5)

Forming a gas generating film in which gas is generated by heat at the time of heat treatment of the wafer on the back surface of the semiconductor wafer;
After the formation of the gas generating film, a step of degassing the semiconductor wafer by heating at 100 ° C. or higher for 2 minutes or more ;
A method for producing a low-slipping wafer comprising a step of polishing the degassed semiconductor wafer surface by 5 to 15 μm . The method for producing a low-slipping wafer according to claim 1, wherein when the degassing process is performed under reduced pressure heating, the heating temperature during the degassing process is set to 450 ° C or higher. The method for producing a low-slipping wafer according to claim 1, wherein when the degassing process is performed under normal pressure heating, the heating temperature during the degassing process is set to 700 ° C or higher. The method for producing a low slip wafer according to any one of claims 1 to 3 , wherein the gas generating film is a low-temperature silicon oxide film. Method for producing a low slip of a wafer according to any one of claims 1 to claim 3 sac Chi said gas generating film is polysilicon film.

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