JP2000150415A - Formation of contact of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming the contact of a semiconductor device by which both a removing property and a bowing shape can be accomplished simultaneously, even when such a contact that is perpendicular to a substrate and has a high aspect ratio is formed. SOLUTION: A method for forming the contact of a semiconductor device includes a step of forming an oxide film on the surface of a semiconductor substrate 2, a first etching step of forming a contact 5 halfway by etching the area of the oxide film which is intended to be used for the formation of the contact 5 by photolithography, and a second etching step of forming the contact 5 by further etching the oxide film at a lower temperature than that used in the first etching step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a contact in a semiconductor device, and more particularly to a method for forming a contact in a semiconductor device for forming a contact having a high aspect ratio.

[0002]

2. Description of the Related Art Recently, with the increasing integration of devices,
The formation of contacts perpendicular to the semiconductor substrate surface and having a high aspect ratio has become an important issue.

Conventionally, contact etching is performed at a constant stage temperature. At this time, it is known from the experimental results that the deposition position for suppressing the progress of etching changes depending on the stage temperature to be employed, which has a strong influence on the final contact shape.
FIG. 2A is a cross-sectional view illustrating an initial state when a contact is etched at a stage temperature of −20 ° C.
FIG. 2B is a cross-sectional view showing a state where the etching of the contact in FIG. FIG. 3A shows that the stage temperature is 0.
It is sectional drawing which shows the initial state when a contact is etched at ° C, and (b) is sectional drawing which shows the completion state of the etching of the contact of (a).

[0004] As shown in FIG.
A case where a contact is formed at 0 will be described. First, an oxide film 102 is formed on a semiconductor substrate 101. Further, a photoresist film 103 is formed thereon. The photoresist film 103 is patterned by a photolithography method, openings are formed at positions where the contacts 104 are to be formed, and the contacts 104 are formed using the photoresist film 103 as a mask.

In order to open the contact 104,
A case where etching is performed at a stage temperature of −20 ° C. will be described. At this time, the semiconductor substrate 101 is about 4
5 ° C. When the temperature of the stage (not shown) on which the semiconductor substrate 101 is mounted is −20 ° C., which is relatively lower than room temperature, the probability of adhesion of the deposition 105 to the contact 104 increases, and the amount of adhesion increases. Therefore, the deposition 105 is easily deposited on the contact 104. On the other hand, the probability of adhesion of the deposition 105 to the side wall 104b of the contact 104 decreases, and the deposition 1
06 decreases. As shown in FIG. 2B, the contact 104 is opened up to the semiconductor substrate 101, but the side wall 104b is formed by ions entering from an oblique direction.
Is etched so that a part of the side wall 104b becomes a boring 106 in the final shape.

A case where a contact is formed in the semiconductor device 100 as shown in FIG. First, an oxide film 102 is formed on a semiconductor substrate 101. Further, a photoresist film 103 is formed thereon. The photoresist film 103 is patterned by a photolithography method, openings are formed at positions where the contacts 104 are to be formed, and the contacts 104 are formed using the photoresist film 103 as a mask.

Next, a description will be given of a case where etching is performed at a stage temperature of 0 ° C. in order to open the contact 104. At this time, the temperature of the semiconductor substrate 101 is about 65 ° C. When the temperature of the stage (not shown) on which the semiconductor substrate 101 is mounted is close to room temperature, the probability that the deposition 105 adheres to the contact 104 decreases,
The deposition 106 is relatively deposited on the bottom 104 a of the contact 104. Further, the amount of the deposition 106 deposited on the side wall 104b also increases. As a result, FIG.
As shown in (b), the side wall 1 is removed from the obliquely incident ions.
04b is protected and the etching of the side wall 104b does not proceed. However, since the amount of deposition 105 attached to the bottom 104a of the contact 104 also increases, FIG.
As shown in (b), the etching is stopped in the middle of the oxide film 102 before reaching the target depth, and the etching is stopped. That is, the vertical contact is finally stopped in the middle of the oxide film 102.

[0008]

However, when a contact perpendicular to the surface of the semiconductor substrate 101 and having a high aspect ratio is processed under a constant temperature condition as described above, the etching of the bottom 104a of the contact 104 is performed by the semiconductor. In the case where it easily advances in the direction of the substrate 101 (hereinafter referred to as good removability), there is a problem that the shape tends to become the boring 106.

If an attempt is made to form a contact perpendicular to the surface of the semiconductor substrate 101, the contact bottom 1
Because the deposition 105 on the 04a also increases,
As shown in FIG. 2B, the etching has a problem that the etching stops in the middle of the oxide film 102 before reaching the target depth.

Further, as described above, if the detachability and the vertical shape of the contact 104 are intended to satisfy the detachability, the contact 104 becomes the bowing 106 and the vertical shape cannot be obtained. There is a problem in that if the shape is made vertical, the removability deteriorates, and it is extremely difficult to achieve both.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and can achieve both the removability and the boring shape at the same time even when processing a contact which is perpendicular to the substrate and has a high aspect ratio. It is an object of the present invention to provide a method for forming a contact of a semiconductor device.

[0012]

According to a first aspect of the present invention, there is provided a method of forming a contact in a semiconductor device, comprising the steps of: forming an oxide film on a surface of a semiconductor substrate; and etching a contact formation region of the oxide film by photolithography. A first etching step of forming a contact halfway, and a second etching step of further etching the oxide film at a lower temperature than the first etching step to form a contact.

Further, in the present invention, in the first etching step, etching is performed while maintaining a temperature of a stage on which the semiconductor substrate is mounted at 0 ° C., and in the second etching step, the semiconductor substrate is mounted. The stage temperature to
It is preferable to perform etching while maintaining the temperature at 0 ° C.

According to a second aspect of the present invention, there is provided a method for forming a contact in a semiconductor device, comprising the steps of: forming an oxide film on a surface of a semiconductor substrate; A first etching step of forming; a second etching step of further etching the oxide film at a lower temperature than the first etching step to form a contact halfway;
A third etching step of forming a contact by further etching the oxide film at a lower temperature than the second etching step.

In the present invention, the first to third etching steps are preferably performed in separate etching chambers.

In the present invention, the temperature of the etching chamber is preferably controlled by a refrigerator.

In the present invention, since the amount and position of deposition deposited in the opening can be arbitrarily controlled by changing the etching temperature and performing etching, the shape perpendicular to the surface of the semiconductor substrate is formed. Can be formed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming a contact of a semiconductor device according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1A is a cross-sectional view illustrating a first etching step according to an embodiment of the present invention, and FIG.
FIG. 4 is a cross-sectional view showing a second etching step following the first etching step.

In the semiconductor device 1 having the contact according to the present embodiment, the contact 5 having a high aspect ratio is formed using two etching chambers (not shown).

First, an oxide film 3 is formed on a semiconductor substrate 2 as shown in FIG. Further, a photoresist film 4 is formed thereon. This photoresist film 4 is patterned by a photolithography method to form a contact 5
The contact 5 is formed using the photoresist film 4 as a mask. For example, the semiconductor substrate 2 is placed on a stage (not shown) and the stage temperature is set to zero.
The formation of the opening of the contact 5 is started using the etching chamber A (not shown) at a temperature of ° C. When the position to be the contact 5 starts to be etched, a deposition 6 is deposited on the inner peripheral surface of the contact 5. Further, the contact 5 is etched to a position deeper than a position where the obliquely incident ions which cause the boring shape reach by advancing the etching. Here, the etching is temporarily stopped. At this time, the deposition for suppressing the progress of the etching is deposited on the entire inner peripheral surface of the contact. The bottom 5a of the contact 5 is located in the middle of the oxide film 3 in the thickness direction.

Next, as shown in FIG. 1B, the semiconductor substrate 2 is moved to an etching chamber B (not shown). The temperature of a stage (not shown) on which the semiconductor substrate 2 is mounted is, for example, −20 ° C.
And lower than the etching chamber A. Contact 5 using this etching chamber B
The contact 5 is then etched as shown in FIG.
Is performed continuously from the state in which is formed halfway. At this time, a large amount of the deposition 6 is deposited on the side wall 5 b of the contact 5. For this reason, the amount of the deposition 6 attached to the bottom 5a of the contact 5 is reduced, so that the etching at the contact 5 proceeds easily. Then, a contact 5 having a high aspect ratio and penetrating the oxide film 3 and reaching the semiconductor substrate 2 is formed.

As described above, the semiconductor substrate 2 is moved to the etching chamber in which the stage is maintained at a different temperature in accordance with the opening state of the contact 5, and the etching temperature is changed stepwise, whereby the deposition 6 The deposition position and the deposition amount can be changed. Therefore, the etching can proceed while preventing the occurrence of bowing and etching stop, and the contact 5 having a high aspect ratio perpendicular to the semiconductor substrate 2 can be formed.
That is, the state is adjusted according to the progress of the opening of the contact 5.
By changing the temperature, the amount and position of the deposition 6 can be arbitrarily controlled, and a contact having a shape perpendicular to the semiconductor substrate 2 and having a high aspect ratio can be formed.

In the present embodiment, the etching is divided stepwise according to the first etching step, the second etching step, and the progress of the etching. However, the present invention is not particularly limited to this. Can be divided into a plurality of steps according to the progress. For example, 3
The etching can be divided into steps or more steps. Thereby, each stage temperature can be set more finely, and the shape of the contact 5 can be more reliably controlled. In this case, each process can be replaced with a different etching chamber.
Contamination and the like can be prevented.

In this embodiment, when performing etching, the same etching chamber is used to control the temperature of the stage.
The etching can also be performed by changing the temperature of the curator as the etching time progresses. This allows
Temperature control can be performed continuously, and reliable shape control can be performed.

Further, in this embodiment, the temperature of the stage for mounting the semiconductor substrate 2 provided in each etching chamber can be controlled, for example, a refrigerator or a chiller (circulator). Can be used to change the stage temperature as the etching time progresses. This allows for more flexible contact etching in accordance with the device structure. In addition, if the stage temperature is changed in the same chamber as described above, it is possible to avoid the risk of contamination or the like.

[0026]

As described in detail above, in the present invention,
By controlling the etching temperature, it is possible to arbitrarily control the deposition amount and the deposition position of the deposition formed on the contact, so that a contact perpendicular to the substrate and having a high aspect ratio can be easily formed.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing a first etching step according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view showing a second etching step following the first etching step.

FIG. 2A is a cross-sectional view showing an initial state when a contact is etched at a conventional stage temperature of −20 ° C., and FIG. 2B is a state in which the contact etching of FIG. FIG.

FIG. 3A is a cross-sectional view showing an initial state when a contact is etched at a conventional stage temperature of 0 ° C., and FIG. 3B is a state in which the contact etching of FIG. FIG.

[Explanation of symbols]

 1, 100; semiconductor device 2, 101; semiconductor substrate 3, 102; oxide film 4, 103; photoresist film 5, 104; contact 5a, 104a; bottom 5b, 104b;

Claims (7)

[Claims] A step of forming an oxide film on a surface of a semiconductor substrate; a first etching step of forming a contact halfway by etching a contact formation region of the oxide film by photolithography; A second etching step of forming a contact by further etching the oxide film at a lower temperature than the step. 2. The method according to claim 1, wherein the first and second etching steps are performed in the same etching chamber. 3. The method according to claim 1, wherein the first and second etching steps are performed in different etching chambers. 4. The first etching step includes etching while maintaining a temperature of a stage on which the semiconductor substrate is mounted at 0 ° C., and the second etching step includes reducing a temperature of a stage on which the semiconductor substrate is mounted. 4. The method for forming a contact of a semiconductor device according to claim 1, wherein etching is performed while maintaining the temperature at -20.degree. 5. A step of forming an oxide film on a surface of a semiconductor substrate, a first etching step of etching a contact formation planned region of the oxide film by photolithography to form a contact halfway, and the first etching A second etching step of further etching the oxide film at a lower temperature than the step to form a contact halfway;
A third etching step of forming a contact by further etching the oxide film at a lower temperature than the second etching step. 6. The method according to claim 5, wherein the first to third etching steps are performed in separate etching chambers. 7. The method for forming a contact of a semiconductor device according to claim 2, wherein the temperature of the etching chamber is controlled by a refrigerator.