JP2002134471A - Etching method and etching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress dispersion of the line width in etching of a multilayer film. SOLUTION: In an etching method, which is so arranged as to perform the etching treatment of a multilayer film by repeating the etching treatment plural number of times, next etching treatment is performed under the condition, that a last reference position θ1 with respect to a chamber of a semiconductor substrate which was used in the last etching, be readjusted to the next reference position θ2. When the worker is to perform etching treatment for two or more times, the position to the chamber of the wafer being the semiconductor substrate is changed. To be concrete, it is adjusted in the range of 180 deg.±30 deg. to the first position. Rotating the wafer 180 deg. and performing the next etching treatment can roughly offset the influence (the difference of etching rate within the chamber, or the difference in the line width by micro-loading effect) specific to the chamber being etched immediately prior. Accordingly, this can realize etching treatment which enables uniform line widths.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an etching method and an etching apparatus for etching a multilayer film without exposing a semiconductor substrate to the atmosphere. Specifically, when performing different etching processes, the position of the semiconductor substrate in the chamber is made different from that in the immediately preceding etching process, thereby avoiding the influence of the inherent etching rate and microloading of the chamber. Thus, a uniform etching process is realized.

[0002]

2. Description of the Related Art An etching apparatus for etching a multilayer film formed on a wafer surface without exposing a semiconductor substrate (wafer) to the atmosphere, particularly a dry etching apparatus is known. When performing an etching process, a wafer to be processed is housed in a chamber. At this time, the reference surface (or reference point) provided on the wafer is aligned with the reference surface (or reference point) in the alignment apparatus. And stored in the chamber.

When dry etching a multilayer film,
There are a case where the etching is performed using the same chamber and a case where the etching is performed using two or more chambers and the chamber is changed for each different etching process. Aside from the case where etching is performed a plurality of times using the same chamber, when performing a different etching process using a plurality of chambers, the wafer is returned to the alignment apparatus and alignment is performed again, and then the etching process is performed.

A specific example will be described. FIG. 8 shows chamber A
The relative positional relationship between the wafer and the wafer 14 is shown.
The wafer 14 is provided with an orientation flat (orientation flat) 16 which is a reference surface. The wafer 14 having the orientation flat 16 is aligned with a reference plane of the apparatus, for example, an x, y reference axis (axial plane) in an alignment apparatus (not shown).

Reference axis of alignment apparatus and chamber A
If the relationship with the reference axis is the same, the orientation flat 16 is carried into the chamber A in a state where the orientation flat 16 is aligned so as to be parallel to the yy axis as shown in the figure. In this state, the first etching process is performed, for example, the film located at the uppermost layer is etched.

Next, when the second etching process is performed using another chamber B, the wafer 14 is once returned to the alignment apparatus and the reference plane is readjusted. Also in this case, as shown in FIG. 9, the reference plane is adjusted so that the orientation flat 16 is parallel to the yy axis. Therefore, the relationship with the wafer 14 in another chamber B is as shown in FIG. In another chamber B, subsequent to the uppermost layer, an etching process is performed on a film existing thereunder.

[0007]

In the above-mentioned dry etching apparatus, one of the chambers A as shown in FIG.
In this example, a predetermined reaction gas is introduced (inhaled) into the chamber A from the left side 12a, and a by-product (gas) generated by the etching process is exhausted from one side, in this example, the right side 12b. I am trying to.

[0008] This dry etching apparatus, particularly a reactive ion etching apparatus (RIE: Reactive Ion Etching).
In this case, the reaction gas sent into the chamber A reacts with negative electrons that fly out of a counter electrode (not shown) provided in the chamber A, and the reaction gas becomes positive ions. Then, an etching process (sputter etching process) is performed by colliding the positive ions with the surface of the wafer on the lower electrode where a self-bias is generated by applying a high frequency power supply.

In this etching process, it is known that the line width formed by the etching process becomes uneven due to the problem of the etching rate (etch rate) and the microloading inherent to the chamber. One reason for uneven line width is the problem of etching rate. As shown in FIG. 8, the reaction speed is slow on the intake side (upstream side) of the reaction gas and on the exhaust side (downstream side). Generally, the etching rate is higher on the exhaust side and becomes slower toward the intake side. Tend to be. As a result, unevenness (variation) occurs in the line width after etching, the exhaust side is too narrower than the standard value, and the intake side tends to be thicker.

[0010] In addition, the microloading effect, which indicates the extent to which by-products (so-called residues) after the etching process adhere to the side walls of the etched film, varies depending on the size of the etching area. Due to the exhaust flow, the exhaust side generally has less microloading effect and the intake side has more. As a result, even if the etching process is performed to have the same line width, the line width on the intake side tends to be wider than the line width on the exhaust side.

Such an etching rate and a microloading effect inherent to the chamber have a strong influence particularly when a multilayer film is etched. This will be described with reference to FIG.

FIG. 10 shows an example of a multilayer film (for example, for a gate electrode) formed on a wafer when polysilicon (Poly) is used as an electrode layer. FIG.
In A, a SiO2 film 22 as an oxide film is formed on the entire surface of the substrate 20, and a polysilicon (polySi) film 24 and a tungsten silicide WSi film 26 as an electrode layer are formed on the upper surface thereof. Have been. The tungsten silicide film 26 is for making the polysilicon film 24 a low resistance layer. On the upper surface of the tungsten silicide film 26, an antireflection film (BARC) 28 for forming a photoresist film 30 by photography is formed.

In the case of such a multilayer structure, since the multilayer film cannot be etched at once, the etching process is performed at least twice. The first etching process is for etching the BARC film 28, and the second etching process is for simultaneously etching the tungsten silicide film 26, which is the electrode layer 23, and the polysilicon film 24.

When the width of the resist film 30 is W, the first etching process is performed as shown in FIG. 10B. At this time, due to the influence of the etching rate and the effect of the microloading effect, when the line width after the etching process at the center of the wafer is the standard line width W, the line width Wb on the exhaust side becomes smaller than W by 2ΔW, for example. On the contrary, the line width Wa on the intake side is wider than W by, for example, 2ΔW. As a result of the adhesion of the by-products due to the microloading effect, the line width on the intake side is increased by 2ΔW. Since the width is almost the same,
B results.

In a second etching process, a resist film 30 (not shown) and an etched BARC film 28 are formed.
Each act as a resist film, the electrode layer 23 is etched on the exhaust side with reference to the BARC film 28 having the line width Wb, and the electrode layer 23 is formed on the intake side with reference to the BARC film 28 having the line width Wa. Etched.

As a result, on the exhaust side, etching is performed with reference to a line width Wb smaller than the standard line width W, so that the line width Wd of the electrode layer 23 when finally etched is:
It becomes smaller by 4ΔW than the standard line width W.

On the other hand, on the suction side, the etching is performed based on the line width Wa wider than the standard line width W, so that the line width Wc of the electrode layer 23 finally etched is smaller than the standard line width W. It becomes thicker by 4ΔW than the line width W.

By the way, when the variation of the line width is measured, when the standard line width is 0.23 μm, the minimum line width is 0.2
24 μm, and the maximum line width was 0.236 μm.

As described above, in the case of a wafer having a multilayer structure, it can be seen that as the number of times of etching increases, the line width becomes uneven. This is because the alignment of the wafer 14 in the first etching process is exactly the same as the alignment of the wafer 14 in the second etching process, as shown in FIG. This is because the influence will appear strongly.

Therefore, the present invention solves such a conventional problem. In particular, when the number of times of etching is two or more, the angle of the etching process is adjusted to a different angle from the alignment adjustment of the immediately preceding wafer. By doing so, a dry etching method and a dry etching apparatus which avoid the influence peculiar to the chamber are proposed, whereby a substantially uniform line width can be obtained even in a multilayer film configuration.

[0021]

In order to solve the above-mentioned problem, in the etching method according to the present invention, the etching process of the multilayer film is performed by repeating the etching process a plurality of times. In the etching method, the next etching process is performed in a state where the immediately preceding reference position θ1 with respect to the chamber of the semiconductor substrate used at the time of the immediately preceding etching is readjusted to the next reference position θ2. .

According to an eighth aspect of the present invention, there is provided an etching apparatus for transporting a semiconductor substrate, an alignment chamber which is set to a reference of the apparatus based on a reference position provided on the semiconductor substrate, and A chamber for carrying in the etching process by loading the semiconductor substrate aligned in the chamber, and performing the etching process more than once, the reference position of the semiconductor substrate in the alignment chamber is different from the immediately preceding reference position. It is characterized in that the etching process is performed in a state where it has been readjusted to the reference position.

In the present invention, when the etching process is performed twice or more, the position of the semiconductor substrate wafer relative to the chamber is changed. Specifically, readjustment is performed within a range of 180 ° ± 30 ° with respect to the initial position. 1 wafer
When the next etching process is performed by rotating the film by 80 °, the influence inherent in the chamber that has been etched immediately before (difference in etching speed in the chamber and difference in line width due to the microloading effect) can be almost offset. Therefore, an etching process having a uniform line width can be realized.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an etching method and an etching apparatus according to the present invention will be described in detail with reference to the drawings. In the present invention, dry etching will be particularly described as an example. Among them, reactive ion etching will be described as an embodiment.

FIG. 1 shows a dry etching apparatus to which the present invention can be applied, in particular, a single-chamber dry etching apparatus 40 having only one chamber. The dry etching apparatus 40 includes a cassette chamber 42 in which a wafer is stored, an alignment chamber 48 for aligning a reference position of the wafer at a desired position, and a chamber (chamber A) 50 for performing an etching process.

A plurality of wafers are accommodated in the cassette chamber 42, and a transfer means (transfer arm) 46 is provided in the load lock chamber 44. The wafers in the cassette chamber 42 are loaded by the load arm into the load lock chamber. After being drawn out into 44, it is carried into an alignment chamber 48 provided adjacent to the load lock chamber 44.

In the alignment chamber 48, the reference position provided on the wafer is changed to the reference position (X,
(Y axis). Details will be described later. The wafer whose reference position has been adjusted (the reference position relative to the adjusted alignment chamber at this time is assumed to be θ1) is again unloaded from the alignment chamber 48 to the load lock chamber 44 by the transfer arm 46, and the unloaded wafer is loaded into this load chamber. Via the lock chamber 44, this load lock chamber 44
Is carried into the chamber 50 connected to the chamber 50.

Electrodes (not shown) are arranged above and below the chamber 50, and a wafer is placed on the lower electrode side. High frequency power is applied to the lower electrode, and a negative self-bias is generated. The chamber 50 is provided with an intake port and an exhaust port, respectively. A reaction gas is injected from the intake port, and residues after sputtering are exhausted from the exhaust port.

If the reference axes (X, Y axes) of the chamber 50 are the same as the reference axes of the alignment chamber 48,
The wafer carried into the chamber 50 is stored in the state of the first reference position θ1. Then, the etching process is performed in the state of the first reference position θ1.

When the etching process is performed a plurality of times, when the etching process is completed, the wafer is once carried into the alignment chamber 48 and the reference position of the wafer is readjusted. The reference position of the wafer used at the time of the next etching process is the immediately preceding reference position θ1.
Is readjusted to a different position θ2.

The wafer whose reference position has been readjusted is sent again into the chamber 50 to prepare for the next etching process. When the last etching process is completed, the wafer is stored again in the cassette chamber 42 by using the transfer arm 46. Therefore, the cassette chamber 42 accommodates both the wafer before the etching process and the wafer after the etching process.

FIG. 2 shows an example of a multi-chamber type etching apparatus 60 having a plurality of chambers. In this example, three chambers 70, 72, 74 are provided so as to be connected to the load lock chamber 44, respectively. Then, the first etching process is performed in the first chamber 70, the second etching process is performed in the adjacent second chamber 72, and the third etching process is performed in the last chamber 74. I have.

In the embodiment shown in FIG. 2, there are two cassette chambers 62 and 76 for accommodating wafers.
One wafer can be etched. Alignment room 68
Has only one room.

Even in the multi-chamber type etching apparatus 60, each of the chambers 70, 72, 7
When a wafer is loaded into the wafer 4, the reference position of the previously adjusted wafer with respect to the chamber in the alignment chamber 68 is readjusted, that is, adjusted to a reference position different from that immediately before the transfer.

In the present invention, as shown in FIG. 3, the orientation flat 116 or the notch 17 shown in FIG. 4 is used as the reference position of the wafer. The orientation flat 16 functions as a reference line (reference plane), and the notch 17 functions as a reference point.

The X-axis and Y-axis shown in the chamber 50 indicate a reference axis in the chamber 50, and this reference axis is also the reference axis (X,
Y axis).

In this example, at the time of the first etching process (first etching process), it is assumed that the reference position of the wafer 14 carried into the chamber 50 is adjusted so as to be parallel to the Y axis. That is, the first reference position θ1 is θ1 = 0. At the first reference position θ1, the orientation flat 16 is assumed to be in a state of facing the intake side of the reaction gas.

Next, the reference position (second reference position θ2) to be readjusted in the second etching process is selected as follows: θ2 = θ1 + (180 ° ± 30 °). In the embodiment, θ2 = θ1 + 180 ° is selected, and the relationship between the chamber 50 and the wafer 14 at that time is shown in FIG. That is, the wafer 14 is loaded and installed while being rotated by 180 ° with respect to the chamber 50. As a result, the orientation flat 16 now faces the exhaust side.

Now, the etching process when the reference position of the wafer with respect to the chamber 50 is changed for each etching process will be described in detail with reference to FIG.

First, as a target multilayer film, a multilayer film for a gate electrode as shown in FIG. 6A is exemplified. Therefore,
As described with reference to FIG. 10A, the structure of the multilayer film is a three-layer structure (polysilicon film 24, tungsten silicide film 2).
6, BARC film 28). The right side is the exhaust side as shown in FIG. 6A.

The first etching process is the same as the conventional one. When a dry etching apparatus, particularly a reactive ion etching apparatus, is used as the etching apparatus, an O 2 gas is used as a reaction gas, and the O 2 gas is injected into the chamber 50. Then, CO2 gas is exhausted as a by-product after the reaction.

Since this first etching process is the same as the conventional one, the line width Wb on the exhaust side is smaller than the standard line width W, and the line width Wa on the intake side is wider than the standard line width W. Tend to be. Therefore, the result is as shown in FIG. 6B, and the respective line widths are as follows: Wb <W <Wa, and Wa ≒ W + 2ΔW Wb ≒ W−2ΔW. Therefore, in the first etching process, the line width is uneven.

Next, the process proceeds to the second etching process.
In this case, the wafer 14 is loaded into the chamber 50 after the reference position of the wafer 14 is readjusted from θ1 to θ2 as described above. Therefore, as shown in FIG. 7A, the wafer 14 is rearranged so that the resist film 30 having the line width Wa is positioned on the exhaust side.

In this state, a second etching process is performed. The reaction gas used in this case is Cl gas and H
It is only Br gas or CF4 gas. The by-product at that time is SiFx gas, which is exhausted from the exhaust port.

The electrode layer 23 is etched as shown in FIG. 7B by the second etching process. That is, due to the inherent etching rate in the chamber 50 and the effect of the microloading effect,
The line width Wf on the exhaust side is etched so as to be narrower than the immediately preceding line width Wa, and the line width We on the intake side is etched to be wider than the immediately preceding line width Wb.

As a result, the line width We of the electrode layer 23 near the intake side is We ≒ Wb + 2ΔW = (W−2ΔW) + 2ΔW = W, and the line width Wf of the electrode layer 23 near the exhaust side is Wf ≒ Wa− 2ΔW = (W + 2ΔW) −2ΔW = W As a result, the resist film 30 and the BARC film 2
By ashing each of the wafers 8, it is possible to obtain a wafer 14 having a substantially uniform line width as shown in FIG. 7C. Incidentally, when the variation of the line width was measured, it was found that when the standard line width was 0.23 μm, the minimum line width and the maximum line width were almost close to the standard line width.

As described above, the chamber 50 of the wafer 14
By re-adjusting the reference position with respect to each time as desired each time the etching process is performed, the unevenness of the line width can be eliminated and the etching process having a substantially uniform line width can be realized over the entire wafer.

In the above description, the relationship between the reference positions θ1 and θ2 is θ2 = θ1 + 180 °, but the wafer need not be completely inverted. According to the experiment, the line width variation was negligible even when etching was performed in an inclined state up to about ± 30 ° such as θ2 = θ1 + (180 ° ± 30 °).

In the above-described embodiment, the present invention is applied to the single-chamber type etching apparatus shown in FIG. 1. However, when the present invention is applied to the multi-chamber type etching apparatus shown in FIG. Uses the first chamber 70, and the second etching process uses the second chamber 72.

In the above embodiment, a reactive ion etching apparatus (RIE) is exemplified as an etching apparatus. However, the present invention can be applied to a reactive ion etching apparatus such as a high-density plasma etching apparatus. The present invention can also be applied to another type of etching apparatus (such as a sputter etching apparatus).

[0051]

As described above, in the present invention, the position of the semiconductor substrate relative to the chamber is changed every time etching is performed.

According to this, since the influence on the line width due to the etching rate and the microloading effect inherent to the chamber can be offset, the line width after etching can be made uniform over the entire surface of the semiconductor substrate. .

[Brief description of the drawings]

FIG. 1 is an explanatory view of an etching apparatus (single chamber type) according to the present invention.

FIG. 2 is an explanatory view of an etching apparatus (multi-chamber type) according to the present invention.

FIG. 3 is a diagram (part 1) illustrating a relative positional relationship (reference position) between a chamber and a wafer.

FIG. 4 is a plan view showing another example of the wafer.

FIG. 5 is a diagram (part 2) illustrating a relative positional relationship (reference position) between a chamber and a wafer.

FIG. 6 is a process diagram (part 1) illustrating an example of an etching process;

FIG. 7 is a process diagram (part 2) illustrating an example of an etching process.

FIG. 8 is a diagram (part 1) illustrating a relative positional relationship (reference position) between a chamber and a wafer.

FIG. 9 is a diagram (part 2) illustrating a relative positional relationship (reference position) between the chamber and the wafer. It is.

FIG. 10 is a process chart showing an example of an etching process.

[Explanation of symbols]

40, 60 ... etching device, 42, 62, 76
..Cassette chamber, 48, 68... Alignment chamber, 5
0, 70, 72, 74 ... chamber, 14 ... wafer, 16 ... orientation flat, 17 ... notch

Claims (12)

[Claims] 1. An etching method in which a multilayer film is etched by repeating an etching process a plurality of times, wherein a reference position θ1 immediately before the semiconductor substrate used in the immediately preceding etching with respect to the chamber of the semiconductor substrate is set as follows. Reference position θ
An etching method characterized in that the next etching process is performed in a state where it has been readjusted to 2. 2. The etching method according to claim 1, wherein the multilayer film is a film for forming an electrode. 3. The method according to claim 1, wherein the etching process is performed at a reference position .theta.2 obtained by rotating the semiconductor substrate by a predetermined angle with respect to the reference position .theta.1 during the next etching process. Item 4. The etching method according to Item 1. 4. The etching method according to claim 3, wherein the reference angle θ2 to be used next is selected as follows: θ2 = θ1 + (180 ° ± 30 °). 5. The etching method according to claim 1, wherein the multilayer film has a three-layer structure, and the multilayer film is etched by two etching processes. 6. The etching method according to claim 1, wherein the etching is performed using one or more chambers. 7. The etching method according to claim 1, wherein said etching is dry etching. 8. A transport means for transporting a semiconductor substrate, an alignment chamber for setting a reference of an apparatus based on a reference position provided on the semiconductor substrate, and a semiconductor substrate aligned in the alignment chamber. When performing two or more etching processes, the etching process is performed in a state where the reference position of the semiconductor substrate is readjusted to a reference position different from the immediately preceding reference position in the alignment chamber. An etching apparatus characterized in that: 9. The immediately preceding reference position θ1 with respect to the chamber of the semiconductor substrate used at the time of etching immediately before
9. The etching apparatus according to claim 8, wherein when readjusting to the next reference position θ2, the reference angle θ2 to be used next is selected as follows: θ2 = θ1 + (180 ° ± 30 °). 10. The etching apparatus according to claim 8, wherein when the etching target film is a multilayer film, the etching process is performed two or more times. 11. The etching apparatus according to claim 8, wherein the chamber is a single-chamber type or a multi-chamber type. 12. The etching apparatus according to claim 8, wherein said etching is dry etching.