JPS59161825A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To obtain the wafers having a constant threshold voltage by a method wherein, when the photosensitive resin film formed on the surface of a semiconductor wafer is to be removed, a plurality of wafers are brought into a reactor in such a manner that their surface will be headed in one direction in a uniform and paralleled manner, and an oxygen-plasma processing is performed only on one sheet located at the endmost part in the reverse direction. CONSTITUTION:A plurality of wafers 3 are arranged on a wafer pedestal 2, and the photosensitive resin film provided on the surface of each wafer 3 is removed by performing an oxygen-plasma processing. According to this constitution, the wafers 3 are arranged on the pedestal 2 in parallel with each other heading in one direction leaving the prescribed intervals between them, and only one sheet located at the endmost part is headed in the reverse direction, thereby enabling to have the surface facing inward. Accordingly, the threshold voltage, which is the representative characteristics of the semiconductor element using the wafers 3 can be brought to the same degree as that of the other wafers, thereby enabling to reduce the physical damage of the wafer 3.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention provides a method for preventing physical damage to wafers inserted into a reactor in a wafer process in which photosensitive resin is removed using oxygen gas plasma. The present invention relates to a method for manufacturing a semiconductor device.

[Tracking technology]

Recent semiconductor devices: There has been dramatic progress in improving the performance of integrated circuits, and due to the need for process technologies such as dry etching or ion implantation, oxygen gas is used in the wafer process to remove photosensitive resin. A method using plasma has become established as an essential method. In a wafer process for removing this type of photosensitive resin, a batch method is used in which a plurality of wafers are processed simultaneously for the purpose of processing capacity or simply for the purpose of removing the resin. FIG. 1 is a cross-sectional view showing a conventional method for manufacturing a semiconductor device, particularly a wafer process in which photosensitive resin is removed.

In the figure, (1) is a quartz reaction tube, (2) is a quartz glass wafer stand that supports multiple wafers (3), (4) is an oxygen gas inlet, and (5) is an oxygen gas inlet. This is a gas exhaust port.

Note that the arrow shown on the wafer (3) indicates the direction of the wafer surface, and all the wafers (3) are arranged facing in a certain direction.

Next, in the wafer process for removing the photosensitive resin with the above configuration, the frequency is, for example, 13.56 Mn2.

It is operated under the conditions of discharge output IKW and oxygen gas pressure 2 Torr.

However, in the conventional semiconductor device manufacturing method, there is extremely non-uniform plasma discharge, and the impact of excited molecules or electrons becomes non-uniform between wafers. Physical damage to the wafers caused by this impact changes the electrical characteristics of the semiconductor elements, resulting in nonuniform electrical characteristics among wafers.

In particular, in semiconductor devices using MO8 type transistors, the effect on the silicon oxide film on the silicon wafer substrate causes
The energy level of the silicon oxide film is changed to change the threshold voltage (VTH), which is a characteristic of a typical device. That is, in FIG. 2, for example, the frequency is 13.56 MHz,
The threshold voltage (vTa) when exposed to plasma discharge for 60 minutes after forming a silicon oxide film for the gate during the manufacturing process of an MO8 type transistor under the conditions of discharge output IKW, oxygen, /l/s pressure 2 Torr. ), wafer stand (2)
It is plotted according to the position of the upper wafer (3). In this FIG. 2, the horizontal axis indicates the order of the wafers (3) on the wafer stand (2), and the vertical axis indicates the threshold voltage (VTR), and (4) indicates the N-channel MO8.
) shows the case of transistor, (B) shows P channel MO8
) Indicates the case of a transistor. From FIG. 2, it can be seen that the characteristics of the Nn1 wafer located at the farthest end on the wafer stand (2) are abnormal, and moreover, it is found that it is located at one end.

As described above, the conventional method has a drawback that the threshold voltage (VTH) of the wafer located at the end of the wafer on the wafer stand (2) changes.

[Summary of the invention]

Therefore, an object of the present invention is to ensure that all wafers have a constant threshold voltage (VTR) regardless of the position of the wafers, without physically damaging the multiple wafers inserted into the reactor. The present invention provides a method for manufacturing a semiconductor element that can be formed as described above.

In order to achieve such an object, the present invention aims to place a plurality of wafers in a reactor evenly and in parallel in the process of removing photosensitive resin using oxygen gas plasma during the manufacturing process of semiconductor devices. The wear 1 is arranged so that its surface faces in one direction, and only one piece of clothing at the extreme end is arranged so that its surface faces inward.

Furthermore, a shielding plate is placed opposite the unino surface at the extreme end. This will be explained in detail below using examples.

[Embodiments of the invention]

FIG. 3 is a schematic cross-sectional view showing an embodiment of the method for manufacturing a semiconductor device according to the present invention. In particular, during the manufacturing process of an MO8 type transistor, a plurality of wafers (
3) shows the wafer process for placing and removing the photosensitive resin. In this embodiment, a plurality of wafers (3) are arranged evenly in parallel on a wafer stand (2) with their wafer surfaces facing in one direction, and only one wafer at the end is Place the garment so that the surface of the garment 1 faces inward. This causes the surfaces of the wafers at both ends to face inward.

When removing the photosensitive resin, for example, a frequency of 13
．． 56 Mn2, discharge output IKW, oxygen gas pressure 2To
During the manufacturing process of MO8 type transistor under the condition of rr,
Figure 4 shows the threshold voltage (VTR) when exposed to plasma discharge for 60 minutes after the formation of the silicon oxide film for the gate, plotted by the position of Unino (3) on the wafer stand (2). . In this Figure 4, positive 1 to 1 on the horizontal axis
Symbol 25 indicates the order of the wafers (3) on the wafer stand (2), the vertical axis indicates the threshold voltage (VTR), (4) indicates the case of an N-channel MO8) transistor, and (B) indicates the P The case of channel MO8) transistor is shown. According to FIG. 4, it is possible to remove the photosensitive resin from a plurality of wafers (3) placed on the wafer stand (2), and to make the threshold voltage (VTR) almost uniform. can.

FIG. 5 is a schematic sectional view showing another embodiment.

In the figure, (6a) and (6b) are shielding plates installed at both ends of the wafer pedestal (2), each having a thickness of, for example, about 1stx, and approximately the same shape as the wafer (3).

Note that this shielding plate (6) and (6b) are attached to the wafer (3).
This shows the case where they are installed at approximately the same spacing as .

By arranging the shielding plates (6a) and (6b) in this way, for example, under the conditions of frequency 13.56 MHz, discharge output IKW, and oxygen gas pressure 2 Torr, MO8
During the manufacturing process of type transistors, when exposed to plasma discharge for 60 minutes after forming a silicon oxide film for the gate,
Characteristics similar to those shown in FIG. 4 were obtained. In this way, it is possible to remove the photosensitive resin from a plurality of wafers (3) placed on the wafer stand (2), and moreover, the threshold voltage (V
TH) can be made uniform.

In addition, although the above-mentioned example showed the case where two shielding plates were provided, when the sea urchins are arranged so that their surfaces always face in a certain direction, for example, when they are arranged in the direction shown in the figure, the shielding plates ( 6b) is not necessarily required, and similarly, it goes without saying that the shielding plate (6a) is not necessarily required when arranged in the opposite direction to the direction shown. Further, the shielding plates (6a) and (6b) may be provided removably or may be provided fixedly.

〔Effect of the invention〕

As explained in detail above, according to the semiconductor device manufacturing process according to the present invention, the characteristics of multiple wafers can be made uniform in the wafer process that uses oxygen gas plasma to remove photosensitive resin. It is particularly effective in processes that are susceptible to plasma damage, such as thinning gate oxide films for highly integrated, high-performance devices.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a conventional method for manufacturing a semiconductor device, FIG. 2 is a diagram showing the threshold voltage (VTR) of each wafer at each wafer position in FIG. 1, and FIG. 3 is a diagram showing a semiconductor device according to the present invention. FIG. 4 is a schematic cross-sectional view showing an example of the manufacturing method of
FIG. 5 is a schematic sectional view showing another embodiment. +1)...Reaction tube, (2)...Wafer stand, (
3)...Wafer, (4j...Inlet, (5)...
...exhaust port, (6a), (6b)...shielding plate.

Claims (2)

[Claims] (1) During the manufacturing process of semiconductor devices, in the step of removing the photosensitive resin formed on the surface of the semiconductor wafer using oxygen gas plasma, a plurality of semiconductor wafers are placed evenly in parallel in a reactor, The semiconductor wafers are arranged so that their surfaces face in one direction, and only one semiconductor wafer at the end is placed so that its semiconductor wafer faces inward, and the semiconductor wafers are exposed to oxygen gas plasma as described above. A method for manufacturing a semiconductor device, which comprises removing a photosensitive resin. (2) During the manufacturing process of semiconductor devices, in the step of removing the photosensitive resin formed on the surface of the semiconductor wafer using oxygen gas plasma, a plurality of semiconductor wafers are placed evenly in parallel in a reactor, In addition, the semiconductor wafer surface is arranged so as to face in one direction, and a shielding plate is arranged opposite to the surface of the semiconductor wafer located at the end, and the photosensitive resin is removed using oxygen gas plasma. Features: A method for manufacturing semiconductor devices.