JPH06302507A - Pattern formation - Google Patents

Abstract

PURPOSE:To provide a method for pattern formation which improves adhesion to resist without any damage to wafers. CONSTITUTION:Resist to be patterned is applied to the previously cleaned surface of a wafer W, and a pattern is formed in the applied resist by lithography. For the surface cleaning, the wafer W is placed on the heater 2 installed in a chamber 1 with which a pipe 9 for feeding surface activation substance (a) communicates. The chamber 1 is then evacuated, and the wafer is heated by the temperature rise of the heater 2 and cleaned. While the chamber 1 is kept evacuated, it is fed with surface activation substance a through the feed pipe 9. The wafer W is thus exposed to the atmosphere of the surface activation substance (a) and activated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method for performing a surface cleaning treatment on a surface of a wafer before applying a resist to be patterned on the surface of the wafer in a lithography process for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In a lithographic process for manufacturing a semiconductor device, a wafer surface is cleaned before a resist to be patterned is applied to the surface of the wafer in order to improve the adhesion between the wafer surface and the resist. . It is known that the adhesiveness of the resist is deteriorated due to, for example, moisture adsorbed on the surface of the wafer. This is particularly because the SiO ₂ film formed on the surface of the wafer is coated with the resist. Remarkably appears when you do.

Therefore, in order to improve the adhesion between the wafer and the resist, the wafer is heated by a hot plate or the like, or the wafer is kept in a reduced pressure to remove adsorbed substances such as moisture adsorbed on the surface thereof. The wafer surface is separated to clean the wafer surface. Further, in order to perform more complete desorption of the adsorbed substance and improve the adhesion between the resist and the wafer surface, the wafer surface is activated by using the surface activating substance after the cleaning of the wafer surface as described above. In some cases.

[0004]

However, the above surface cleaning method has the following problems. That is, water molecules, which have a great influence on the adhesiveness of the resist, have a very strong adsorption force to the wafer surface. For this reason,
When the surface cleaning process is performed by heating the wafer,
It is necessary to heat at high temperature for a long time in order to desorb water molecules from the wafer surface. However, since the temperature of the entire wafer rises due to this heating, for example, the wafer expands or contracts due to the temperature difference due to heating, or the oxidation of the wafer surface is promoted so that the thickness of the oxide film is changed and the wafer itself is Damage occurs.

Further, when the surface cleaning step is performed by keeping the wafer in a reduced pressure atmosphere, desorption of the adsorbed substance removes heat of vaporization from the surface of the wafer to lower the wafer temperature. When the surface temperature of the wafer is lowered, the adsorbed substance hardly absorbs heat, and desorption is prevented. Further, since the heat of vaporization is larger for a substance having a stronger adsorption force such as water molecules, if a certain amount of the adsorbed substance is desorbed, the equilibrium state is maintained and the desorption does not proceed. Therefore, water molecules cannot be sufficiently desorbed from the surface of the wafer.

When the surface activating step is performed after the surface cleaning step, the wafer is first exposed to the atmosphere and then exposed to the atmosphere of the surface activating substance. Therefore, adsorbed substances such as water molecules in the atmosphere adhere to the once cleaned wafer surface again, and the cleaning of the wafer surface is impaired.

Therefore, since the activation process is performed on the surface of the wafer which has not been sufficiently cleaned or whose cleaning has been impaired as described above, the surface activating substance is not efficiently replaced by the wafer surface. However, the effect of the activation process could not be fully exerted.

[0008] Therefore, an object of the present invention is to provide a pattern forming method in which the adhesion between the wafer and the resist is improved without damaging the wafer.

[0009]

In order to solve the above-mentioned problems, the first pattern forming method of the present invention applies a resist for patterning to the surface of a wafer which has been subjected to a surface cleaning treatment in advance, and applies the resist. In the method of forming a pattern on a resist by a lithographic technique, the surface cleaning process is performed by placing a wafer on a sample table that can be heated in a chamber, reducing the pressure in the chamber, and raising the sample table. A cleaning step of heating the wafer by temperature is performed. In the second pattern forming method of the present invention, in the surface cleaning treatment, the wafer is placed on a sample table that can be heated and is installed in a chamber in which a supply pipe for a surface activating substance is connected. A cleaning step is performed in which the chamber is depressurized and the wafer is heated by raising the temperature of the sample stage. Then, an activation step is performed in which the inside of the chamber is kept under a reduced pressure and the surface activating substance is introduced into the chamber from the supply pipe to expose the wafer to the atmosphere of the surface activating substance.

[0010]

According to the first pattern forming method of the present invention, since the wafer is heated in the reduced pressure atmosphere, the adsorbed substances on the surface of the wafer are desorbed at a lower heating temperature. Damage is reduced. Further, even if heat of vaporization is taken from the surface of the wafer due to desorption of the adsorbed substance, the surface temperature of the wafer does not decrease. Therefore,
The heat of vaporization is continuously supplied to the adsorbent, and the adsorbent is sufficiently desorbed.

Next, according to the second pattern forming method of the present invention, since the wafer is heated in the reduced pressure atmosphere in the chamber and the surface activating substance is subsequently introduced into the same chamber, the wafer is exposed to the atmosphere. Instead, the cleaning process and the activation process are performed. Therefore, the activation step is performed on the clean surface from which the adsorbed substance is desorbed in the cleaning step.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example of an apparatus used for the surface cleaning treatment in the pattern forming method of the embodiment. As shown in the figure, the above apparatus has a chamber 1 formed by a box-shaped main body 1a having an open top and a lid 1b closing the top opening of the main body 1a. Inside the chamber 1, a heater is provided. Is installed on the bottom of the main body 1a, and this heater serves as the sample table 2 on which the wafer W is placed. And
A nozzle 3 for supplying the surface activating substance a into the chamber 1 is installed on the inner surface of the lid 1 b facing the wafer W mounting surface of the sample table 2.

An exhaust pipe 5 in which a vacuum exhaust system 4 is arranged and a gas introduction pipe 7 in which a control valve 6 is arranged communicate with the main body 1a of the chamber 1. From the gas introduction pipe 7, an inert gas such as nitrogen gas b and the atmosphere are introduced into the chamber 1. A temperature sensor 8 is arranged on the sample table 2 to detect the temperature of the sample table 2 and control the heating temperature. Further, the nozzle 3 has a shape in which a plurality of holes 3a, 3a ... Are formed in a surface having the same shape as the surface of the sample table 2 on which the wafer W is mounted. A supply pipe 9 penetrating the lid 1b from the outside of the chamber 1 communicates with the nozzle 3 so that the surface activating substance a is evenly supplied into the chamber 1 through the holes 3a, 3a.

Next, the case where the surface cleaning treatment in the pattern forming method of the present invention is performed by using the apparatus having the above-mentioned structure will be described. First, the wafer W to be processed is placed on the sample table 2 and the lid 1b is closed. Then, the gas in the chamber 1 is exhausted by the operation of the vacuum exhaust system 4, and the inside of the chamber 1 is
The pressure is reduced to Pa or less. Then, the wafer W is heated to, for example, 50 ° C. by the sample table 2.

Next, the nitrogen gas b is introduced into the chamber 1 through the gas introduction pipe 7 under the control of the control valve 6. When the partial pressure of the nitrogen gas b in the chamber 1 reaches about 100 Pa or more, the wafer W is held for 10 seconds or more, and the surface of the wafer W is cleaned. In this step, the heating temperature of the wafer W and the depressurized state in the chamber 1 are set so that the adsorbed molecules such as water molecules are sufficiently desorbed from the surface of the wafer W without damaging the wafer W. And

After that, the introduction of the nitrogen gas b from the gas introduction pipe 7 is stopped, and the inside of the chamber 1 is again set to 10000 Pa.
Exhaust to Then, the surface activating substance a such as HMDS (hexamethyldisilane) is supplied from the supply pipe 9 into the chamber 1 while continuing to exhaust the inside of the chamber 1. In this case, nitrogen gas or the like is supplied as carrier gas from the supply pipe 9 at the same time. Then, when the partial pressure of the surface activating substance a becomes 10 Pa or more in the chamber 1, the wafer W is held for 5 seconds or more, and the activation process of the surface of the wafer W is performed.

After the activation step, the supply of the surface activating substance a and the carrier gas from the supply pipe 9 is stopped, and the chamber 1 is evacuated to 10,000 Pa or less. Then, the exhaust of the chamber 1 is stopped, and the nitrogen gas from the gas introducing pipe 7
Dry air or atmospheric air is introduced into the chamber 1 to return the chamber 1 to normal pressure, and the surface cleaning process for the wafer W is completed.

Then, a resist is applied to the surface of the wafer W which has been cleaned as described above, and a pattern is formed on the resist.

In the above pattern forming method, since the wafer W is heated in the reduced pressure atmosphere in the cleaning process of the surface of the wafer W, water molecules and the like adsorbed on the surface of the wafer W are heated at a lower heating temperature than in the case of only heating. The adsorbed material is desorbed.
Therefore, damage to the wafer due to heating is reduced. Further, even if heat of vaporization is taken from the surface of the wafer due to desorption of the adsorbed substance, the surface temperature of the wafer does not decrease. Therefore, the heat of vaporization is continuously supplied to the adsorbed substance, and the adsorbed substance is sufficiently desorbed.

Further, in the step of activating the surface of the wafer W, the surface activating substance a is introduced into the chamber 1 which is kept in a reduced pressure state in the cleaning step. Therefore, the activation process is performed continuously with the cleaning process without exposing the wafer W to the atmosphere. Therefore, the adsorbed substance such as water is not adsorbed on the cleaned surface, and the wafer surface is efficiently replaced with the surface activating substance for activation.

The pressure in the chamber 1 and the heating temperature of the wafer W by the sample table 2 shown in the above embodiment are merely examples, and the surface is efficiently cleaned and activated depending on the material and surface condition of the wafer W. Will be set. Further, in the above embodiment, HMDS is used as an example of the surface activating substance a, but it goes without saying that the surface activating substance a is appropriately selected depending on the material of the wafer W.

[0022]

As described in detail in the above embodiments, according to the pattern forming method of the present invention, the surface cleaning process is performed without damaging the wafer. Therefore, pattern formation can be performed while maintaining a good wafer state. Further, since the adsorbed substances are sufficiently desorbed, the cleaning of the wafer surface is promoted. Therefore, the adhesion between the resist forming the pattern and the wafer surface is improved. Further, according to the other pattern forming method of the present invention, since the surface cleaning treatment of the wafer surface is performed without exposing it to the atmosphere, the wafer surface is efficiently activated. Therefore, the adhesion between the resist forming the pattern and the wafer surface is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an example of a device that implements the present invention.

[Explanation of symbols]

 1 chamber 2 sample stage 9 supply pipe a surface activating substance W wafer

Claims (2)

[Claims] 1. A method of applying a resist to be patterned onto a surface of a wafer which has been subjected to a surface cleaning treatment in advance and forming a pattern on the applied resist by a lithographic technique, wherein the surface cleaning treatment is set in a chamber. A pattern comprising performing a step of placing a wafer on the sample table capable of raising the temperature, and a cleaning step of heating the wafer by raising the temperature of the sample table while reducing the pressure in the chamber. Forming method. 2. A method of applying a resist to be patterned onto a surface of a wafer which has been subjected to a surface cleaning treatment in advance and forming a pattern on the applied resist by a lithographic technique, wherein the surface cleaning treatment is a surface activating substance. A step of placing a wafer on a temperature-adjustable sample stage installed in a chamber communicating with the supply pipe of, and heating the wafer by raising the temperature of the sample stage while reducing the pressure in the chamber. Performing a cleaning step and an activation step of continuously maintaining the depressurized state in the chamber and introducing a surface activating substance into the chamber from the supply pipe to expose the wafer to an atmosphere of the surface activating substance. And a pattern forming method.