JPH05251334A - Method and apparatus for ashing - Google Patents

Abstract

PURPOSE:To control an ashing rate by a method wherein, in order to enhance the uniformity of the ashing rate of a wafer by using an ashing gas, the temperature of each part of the wafer can be adjusted. CONSTITUTION:The following are installed at an ashing apparatus: photodetector arrays 5 which measure light emitted by CO in the ashing operation of a wafer and which have been installed at the outer circumferential part of the wafer; a heating device 8 which heats the wafer; and a control device 20 which outputs a signal indicating a heating part and a heating degree to the heating device 8 on the basis of signals of the photodetector arrays 5. The temperature of each part of the wafer is adjusted according to the light-emitting intensity of the CO.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and an ashing method for ashing a resist applied on a wafer, particularly for a batch type asher.

[0002]

2. Description of the Related Art In order to form a fine pattern in a semiconductor manufacturing process, a step of removing a resist, which is an unnecessary etching mask, is required following the etching step. In wet processing using chemicals,
(1) It is difficult to always keep these chemicals clean,
There are problems that (2) the work is dangerous, (3) the waste liquid treatment is difficult, and (4) the process is complicated and labor-intensive. As a countermeasure against these problems, a dry process has been promoted in the resist removing process.

The ashing by the Doran process is
For example, '90 latest semiconductor process technology, monthly Semi
In the Conductor World special edition press journal 1989, p208,209, it is shown as follows. The reaction mechanism of ashing by oxygen plasma is
It is considered as follows. That is, a chemical reaction between oxygen radicals (excited oxygen atoms) generated in oxygen plasma and an organic substance causes oxidative decomposition, and finally CO
It becomes ₂ (carbon dioxide) and H ₂ O (water). If indicated by the chemical reaction formula, the _{C x H y + (2x +} y / 2) O * → xCO 2 ↑ + y / 2H 2 O ↑. That is, the solid resist is an oxygen radical O *.
It is converted into carbon dioxide and water vapor and removed.

Therefore, the ashing performance (speed, uniformity, etc.) is determined by the parameters that influence the reaction speed in the above equation, such as the method of generating oxygen radicals, the method of supplying oxygen radicals to the wafer, and the wafer temperature. The reaction of the above formula has a large temperature dependency, and in the case of a batch type device, the wafer is heated by a hot plate, a lamp or the like to increase the ashing speed.

A conventional apparatus of this type is shown in FIG. 7, in which a plurality of wafers 42 are arranged in a direction in which they overlap with each other and placed in a quartz chamber 41, and an ashing gas is introduced from a gas inlet 50 to exhaust the gas. Exhaust from the mouth 52. As a result, the components on the wafer are ashed. An electrode 46 for applying RF is placed on the inner circumference of the quartz chamber, and a heater 48 for keeping or heating the system at a constant temperature is provided on the outer circumference. Note that 43 is an RF power source and 44 is a quartz port.

[0006]

However, in the apparatus having the above structure, even if the gas flow rate, the chamber internal pressure, and the temperature are changed, it is difficult to make the distribution of the reactive species of the ashing gas uniform, so that the ashing between the wafers is performed. There is a problem that the rate uniformity is not improved. The present invention eliminates the above-mentioned problem that the uniformity of the ashing rate is not improved,
An excellent ashing method for improving the uniformity of the ashing rate by providing a light-receiving element that monitors the emission of CO emitted from each wafer during ashing and a heating device that can adjust the temperature of each portion according to the amount of emitted light. And its device.

[0007]

In order to achieve the above object, the present invention provides an ashing apparatus for removing a resist applied to a wafer with an ashing gas, in which a plurality of wafers are arranged in an overlapping direction and Holding means, a light receiving means installed on the outer peripheral part of the wafer for measuring the emission intensity of light emitted during ashing, and a heating part installed on the outer peripheral part of the wafer for selecting a heating location and a heating degree. Means, and a control means for controlling the heating location of the heating means and the degree of heating so that the ashing rate of the wafer is made uniform by the signal of the light receiving means.

[0008]

According to the present invention, as described above, the emission intensity of CO generated on the wafer during ashing is monitored by the light receiving element, a portion having a small emission intensity of CO is detected, and the portion having a low ashing rate is detected. When it is determined that the portion is a portion, the portion is heated according to the amount of emitted light, and the temperature is raised, thereby increasing the ashing speed and making the ashing of the wafer uniform.

[0009]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 is a sectional view of an apparatus showing an embodiment of the present invention, and FIG. 2 is a plan view thereof. As shown in the figure,
Wafers 2 to be ashed are arranged in a direction in which they are overlapped by a quartz port 4, and are arranged in a quartz chamber 1. A certain amount of ashing gas is introduced from the gas inlet 10,
The gas is exhausted from the gas exhaust port 12 so that the pressure can be kept constant. Two electrodes 6 capable of applying RF are provided on the inner circumference of the quartz chamber 1, and a light receiving element array 5 is arranged on the outer circumference of the chamber. The light-receiving element array 5 monitors the light emission of CO generated in, for example, the upper, middle, and lower stages of the wafer, and the monitor signal amplifies the signal corresponding to the light emission amount of CO, and a photomultiplier (photoelectron multiplier tube) 7 Through
It is input to the control device 20 that controls the heating of each part according to the amount of the current. The controller 20 is connected to the heating device 8 installed on the outer circumference of the quartz chamber and controls the temperature of the wafer 2.

The main component of the resist coated and hardened on the wafer 2 is represented by C _x H _y , and the following chemical reaction occurs in the chamber due to oxygen radicals O * excited by the high frequency discharge. C _x H _y + (2x + y / 2) O * → xCO ₂ ↑ + y / 2H ₂ O ↑ That is, the solid resist is converted into carbon dioxide and water vapor by the oxygen radical O * and removed.
Ashing by oxygen radicals is an oxidation chemical reaction, and becomes faster as the temperature rises. Further, CO and OH are also generated during this reaction, and when the ashing of the resist is completed, the generation of CO ₂ , H ₂ O, CO and OH disappears. During the above reaction, CO or OH emits light. The emission by CO is λ = 483 nm, and OH
The light emission by λ = 306-316 nm. When Freon gas CF ₄ is mixed with oxygen as ashing gas, it is ashed by fluorine radicals together with oxygen radicals, and emission λ = 704 nm due to fluorine radicals is also observed.

The case of light emission by CO will be described below. It is also possible to measure the light emission by OH and F other than CO. When light emission from a plurality of species is present at the same time, it is possible to use an appropriate filter that passes the wavelength of the light emission that is the object of photometry or use a light receiving element having an appropriate wavelength characteristic. Upon ashing, as described above, CO light is emitted from the reaction product, and this is monitored by the light receiving element array 5. The light emission amount is proportional to the CO generation amount, and the CO generation amount is proportional to the ashing rate.
The ashing rate can be monitored.

If there is a difference in the ashing rate between the wafers, there is a difference in the emission intensity of CO. The emission intensity received by each light receiving element is analyzed by the control device 20, and the weak intensity part is heated at the part corresponding to the heating controller of the heating device 8 to increase the ashing rate and improve the uniformity. .. The positional relationship between the light receiving element array 5 and the heating device 8 with respect to the wafer 2 will be described with reference to FIG.

The wafer 2 is arranged at the center of the quartz chamber 1 by the quartz port 4, and the RF electrodes 6 are concentrically arranged on the outer peripheral position of the wafer 2. A plurality of light-receiving element arrays 5 each having a plurality of light-receiving elements arranged at equal distances from the center of the wafer 2 are provided at positions where the light emitted from the wafer 2 reaches through the divided gaps of the RF electrode 6. To be done. Further, a plurality of heating devices 8 are installed at the same distance from the center of the wafer 2. FIG. 2 shows a schematic view in which the light receiving element array 5 and the heating device 8 are separately installed on both sides.

The light receiving element array 5 and the heating device 8 are connected via the photomultiplier 7 and the control device 20. The light emitted by the ashing on the wafer 2 is detected by the light receiving elements of the light receiving element array 5,
After being amplified by the photomultiplier 7, the control device 20
At, the light emission state and its position are calculated, and for the portion with weak emission intensity, the corresponding portion of the heating controller of the heating device 8 is heated. When the temperature of the wafer 2 rises due to this heating, the ashing rate rises, and the amount of CO light emission increases, the light emission intensity of the portion where the previous light emission intensity is weak rises, the heating device 8 is controlled, and the heating device 8 is heated. Decrease or stop. This makes the ashing rate of the wafer 2 uniform.

FIG. 3 shows a circuit block diagram of the embodiment shown in FIGS. In FIG. 3, the chamber 1, the wafer 2, the quartz port 4, the RF electrode 6 and the like are omitted. A plurality of light receiving element arrays 5 and heating devices 8 are prepared. The light receiving element array 5 is the light receiving element array 5 _1
2 , ... Comprised of light receiving element array 5 _n , which are installed at equal distances from the center of wafer 2 at equal angular positions, as in FIG. As a result, the CO emission state in the circumferential direction of the wafer 2 can be observed. The light-receiving element array 5 is divided into, for example, an upper stage, a middle stage, and a lower stage, and the CO emission state in the height direction of the wafers 2 stacked above can be observed. In the figure, H _n , M _n , L _n
It is displayed by. The arrangement method of the light receiving element array 5 may be other than the above. For example, the number of divisions in the height direction and the division method can be changed depending on the observation of the emission state of CO.

The photodetector array 5 _1, 5 _2, optical signals from _{··· 5 n h 1, m 1} , l 1, ··· h n, m n, l n
Is input to the photomultiplier 7, and the control device 20
Entered in. The controller 20 controls the heating element 8 and valves. The heating element 8 is controlled by the control device 2
This is performed by the heating drive control circuit 28 in 0.

The optical signal input to the photomultiplier 7 is current-amplified, signal-amplified by the amplifier (AMP) 22, and input to the average value circuit 24 and the arithmetic circuit 26. The average value circuit 24 calculates the average value of the detection signals amplified by the amplifier 22, and measures the overall emission state of CO at that time. By taking the average value, it is possible to smooth the variation in the emission state of CO. The output of the average value circuit 24 is input to the arithmetic circuit 26 together with the output of the amplifier 22. It is input to the heating drive control circuit 28 of the arithmetic circuit 26.

In one embodiment, the arithmetic circuit 26 calculates the difference between the output of the amplifier 22 and the output of the average value circuit 24, and the total emission of CO in the emission state of CO at each location. The deviation from the state can be calculated. The control of the heating drive control circuit 28 by this difference output is
With respect to the heating element in the portion of the CO light emission amount larger than the output of the average value circuit 24, the temperature is lowered, and for the heating element in the portion of the CO light emission amount smaller than the output of the average value circuit 24. To raise the temperature.

Alternatively, in the second embodiment of the arithmetic circuit 26, the ratio between the output of the amplifier 22 and the output of the average value circuit 24 is calculated, and as in the first embodiment, each of them is calculated. It is possible to calculate the deviation of the emission state of CO in a place from the overall emission state of CO. The control of the heating drive control circuit 28 based on this specific output is performed so as to lower the temperature of the heating elements in the portion where the ratio is greater than 1, and the CO emission amount is smaller than 1. For some heating elements, the temperature is raised.

Further, in the third embodiment of the arithmetic circuit 26, the maximum value of the output of the amplifier 22 is selected without inputting the output of the average value circuit 24 to the arithmetic circuit 26, and the maximum value becomes the reference. Thus, the maximum value and the output of the amplifier 22 are calculated, and the heating element is heated by the difference. further,
In the fourth embodiment of the arithmetic circuit 26, in accordance with the maximum ratio of the output of the amplifier 22 and the output of the average value circuit 24 of the second embodiment, the portion of the CO emission amount having the small ratio is calculated. For the heating element, the temperature is raised according to the ratio.

In the fifth embodiment of the arithmetic circuit 26, a preset reference pattern may be used instead of the average value. This reference pattern is used to store the CO emission intensity or the time change of the heating control of the heating element in a memory or the like.
The heating element 8 includes, for example, the heating element 8 ₁ , the heating element 8 ₂ ,
... A plurality of heating elements 8 _n are provided, and the light receiving element array 5 _{1 is a} light receiving element array 5 ₂ , ...
It is arranged so as to correspond to _n . The heating element 8 and the light-receiving element array 5 do not necessarily have to correspond to each other on a one-to-one basis. The heating elements 8 _n are, for example, divided in the height direction of the upper, middle, and lower stages of HH _n , HM _n , and HL _n , and are also divided in the circumferential direction at the positions at the same distance from the center of the wafer 2. Installed at equiangular positions.

These heating elements 8 ₁ , heating elements 8 ₂ , ...
The heating elements 8 _n are individually driven by the signals of the heating drive control circuit 28. Therefore, the heating drive control is
The location and degree of heating for which heating element and how much heating is performed are selected. The control circuit 20 includes the valve control device 2
Contains 1. The valve control device 21 includes a vacuum gauge 31,
Electromagnetic valves 32, 34, 36, flow control valves 35, 3
It is connected to 7.

The chamber 1 is evacuated by a vacuum pump (not shown), and oxygen gas is supplied into the chamber when a predetermined vacuum degree is reached. The degree of vacuum is fed back to the valve control device 21 by the vacuum gauge, and the flow rate control valve 35 is controlled so that the pressure in the chamber is maintained constant. The other electromagnetic valve 36 and flow rate control valve 37 are for purging gas.

The ashing is finished as follows. The first example of the end of ashing is performed by utilizing the fact that CO emission is limited at the end of ashing. This is performed by inputting the output of the average value circuit 24 to the valve control device 21 via the switching circuit 27 and monitoring the change in the value. As a monitor, the average value circuit 2
It is also possible to use the derivative of the output of 4. Alternatively, the output of the average value circuit 24 may be compared with a set value.

A second embodiment of ashing termination is CO
Other than the light emission of, for example, OH light emission is detected in the same manner as in the first embodiment. The third embodiment of the end of ashing is performed by utilizing the fact that the integrated light intensity value is substantially proportional to the amount of ashing. This is performed by inputting the output of the average value circuit 24 into the integrating circuit 25 to calculate the light intensity integrated value, inputting it into the valve control device 21 via the switching circuit 27, and monitoring the change in the value. The monitoring is performed by comparing the light intensity integrated value and the set value.

An embodiment of the heating element 8 will be described with reference to FIGS. In FIG. 4, the wafers 2 and the heating elements 8 are alternately stacked in a laminated shape. In FIG. 4A,
A heating element HL, a heating element HM, and a heating element HH are sequentially inserted in layers between the wafer 2 in layers. 4 (b), (c) and (d) of FIG. 4 show examples of the heating element. The heating element is formed by a heat pipe, and its shape is spiral in (b) and divided in the circumferential direction in (c) and (d). By dividing as shown in (c) and (d), finer heating control is possible.

The embodiment of the heating element 8 shown in FIG. 5 is an example arranged on the outer peripheral portion of the wafer 2. As shown in FIG. 5A, the light receiving element array 5 and the heating elements 8 are concentrically arranged on the outer periphery of the wafer 2. In (b), an example using a hot plate 81 as the heating element 8 is shown. The hot plates divided into arcs in the circumferential direction are HH _1, HH _{2 ,}
HH _3, HH ₄ , HM _1, HM _2, HM _3, HM ₄ , H
It is composed of L _1, HL _2, HL _{3 and} HL ₄ . The number of divisions in the circumferential direction and the height direction can be changed. In (c), an example is shown in which the lamp 82 is used as the heating element 8. The arrangement of the lamp 82 is performed in the same manner as in (b). Further, in (d), an example in which the heating wire 83 is used as the heating element 8 is shown. The heating wire 83 is arranged in the same manner as in (b).

The embodiment of the heating element 8 shown in FIG. 6 is an example arranged on the outer peripheral portion of the wafer 2 similarly to FIG. The heat generating element 8 in FIG. 6 has the same shape as a set of a light receiving element 15 and a heat generating element, and the heat generating element surrounding the wafer and the light receiving element are integrated with these as a structural unit.
The heat generating element 8 in (a) is an element in which the light receiving element 15 is incorporated in the hot plate 81, and this element is configured in a substantially cylindrical shape and surrounds the wafer 2. The heating element 8 in (b) is an element in which the heating wire 83 and the light receiving element 15 are incorporated in the heating element holder 85, and this element is configured in a substantially cylindrical shape to surround the wafer 2. The heating element 8 in (c) is an element in which the heat pipe 84 and the light receiving element 15 are incorporated in the heating element holder 85, and this element is configured in a substantially cylindrical shape to surround the wafer 2.

In (e), (f) and (g), the constitutional unit of the heating element 8 and the constitutional unit of the light receiving element 15 are prepared separately. (E) is the hot plate 81 and the light receiving element 15
And a light receiving holder 16 in which is incorporated. The hot plate 81 and the light receiving holder 16 have substantially the same shape. (F) shows the heating element holder 85 with the heating wire 83 incorporated therein and the light receiving holder 16 with the light receiving element 15 incorporated therein.
Composed of and. The heating element holder and the light receiving holder 16 have substantially the same shape. (G) is composed of a heating element holder 85 in which the heat pipe 84 is incorporated and a light receiving holder 16 in which the light receiving element 15 is incorporated. The heating element holder and the light receiving holder 16 have substantially the same shape.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention.

[0031]

As described above, according to the present invention,
Since the light receiving element array detects a portion where the emission intensity of CO is low during ashing and increases the ashing rate by heating the portion, an effect of improving the ashing rate uniformity in the batch type ashing device can be expected.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus showing an embodiment of the present invention.

FIG. 2 is a plan view of an apparatus showing an embodiment of the present invention.

FIG. 3 is a circuit block diagram showing an embodiment of the present invention.

FIG. 4 is a configuration diagram of a heating element showing an embodiment of the present invention.

FIG. 5 is a schematic view of a heating element showing an embodiment of the present invention.

FIG. 6 is a configuration diagram of a heating element showing another embodiment of the present invention.

FIG. 7 is a cross-sectional view of a conventional device.

[Explanation of symbols]

 1 Quartz Chamber 2 Wafer 3 RF Power Source 4 Quartz Port 5 Photoreceptor Array 6 RF Electrode 7 Photomultiplier 8 Heating Device 10 Gas Inlet 12 Gas Exhaust Port 15 Photoreceptor 16 Photoreceptive Holder 20 Controller 21 Valve Control 22 Amplifier (AMP) 24 Average Value Circuit 25 Integrating Circuit 26 Computing Circuit 27 Switching Circuit 28 Heating Drive Control Circuit 31 Vacuum Gauge 32, 34, 36 Electromagnetic Valve 35, 37 Flow Control Valve 81 Hot Plate 82 Lamp 83 Heating Wire 84 Heat Pipe 85 Heating Element Holder

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/66 X 8406-4M

Claims (10)

[Claims] 1. An ashing apparatus for removing a resist applied to a wafer by an ashing gas, wherein (a) a means for arranging a plurality of wafers in an overlapping direction and holding the wafer in a chamber, and (b) an outer periphery of the wafer. (C) a heating means installed on the outer surface of the wafer and capable of selecting a heating location and a heating degree; An ashing apparatus comprising: a control unit that controls a heating location and a heating degree of the heating unit so that the ashing rate of the wafer becomes uniform according to a signal of the light receiving unit. 2. The light receiving means comprises light receiving elements arranged in an array, and the length direction of the array is the arrangement direction of the plurality of wafers, and the light receiving elements are arranged concentrically on the outer periphery of the wafer. The ashing device according to claim 1, wherein: 3. The light receiving means and the heating means are provided with a plurality of one component formed by combining a light receiving element forming the light receiving means and a heating element forming the heating means on the outer periphery of the wafer. The ashing device according to claim 1, wherein 4. The ashing apparatus according to claim 1, wherein the heating means is inserted between the adjacent wafers with a space therebetween, and the heating means and the wafer are laminated. 5. The control means selects the heating location and the degree of heating based on the difference or ratio between the signal of the light receiving means and a reference value, drives the heating means, and changes the emission intensity. The ashing apparatus according to claim 1, wherein the ashing rate of the wafer is made uniform. 6. The ashing device according to claim 5, wherein the reference value is an average value of signals of the light receiving means. 7. The ashing device according to claim 5, wherein the reference value is a maximum value of a signal of the light receiving means. 8. The ashing device according to claim 5, wherein the reference value is a preset value. 9. The ashing device according to claim 1, wherein the emitted light is emitted by carbon monoxide. 10. An ashing method for removing a resist applied to a wafer by an ashing gas, comprising the steps of: (a) measuring the emission intensity of emitted light during ashing; and (b) detecting the ashing rate from the emission intensity. And (c) calculating the degree of nonuniformity of the ashing rate on at least one wafer from the ashing rate, and (d) reducing the degree of nonuniformity of the ashing rate on at least one wafer. And a step of partially heating the wafer.