JP5544997B2 - Semiconductor device manufacturing method and semiconductor device manufacturing apparatus. - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device having a trench and a semiconductor device manufacturing apparatus.

  In a semiconductor device having a concave groove such as a pressure sensor or a semiconductor device in which a part of an isolation region at the end of a reverse blocking IGBT (insulated gate bipolar transistor) is formed using a groove, the groove is formed by wet anisotropy. In some cases, etching is used to form a silicon wafer.

  FIG. 8 is a schematic diagram of wet anisotropic etching of silicon with an alkaline solution. An aqueous solution of KOH (potassium hydroxide), hydrazine, ethylenediamine, ammonia or the like is used for the wet anisotropic etching solution of silicon. When these alkali solutions are used, anisotropy (plane orientation dependence of the etching rate of silicon) is exhibited.

  Specifically, the etching rate when using the KOH solution is (111) :( 110) :( 100) to 1: 600: 400, and etching is performed on the crystal plane {111} equivalent to the (111) plane. Will stop in effect.

  Therefore, it is known that a V-shaped groove, pyramid-type pit, and pyramid-type cavity structure can be formed if an etching mask is previously formed on the (100) wafer along the {110} direction and etching is performed. It has been. The etching depth is determined by the size of the opening to be etched (etching opening).

The dissolution reaction of silicon by this alkaline solution (intermediate reaction is omitted) is expressed as Si + 2OH ⁻ + 2H ₂ O → Si (OH) ₂ (O ⁻ ) ₂ + 2H ₂ ↑. As can be seen from this reaction equation, it can be seen that the amount of Si etching (etching depth) and the amount of hydrogen gas (bubbles) generated are in a proportional relationship.

  (100) An etching opening is formed on the wafer along the [110] direction and the equivalent <110> direction. When etching is performed with the width of the etching opening larger than the thickness of the silicon wafer multiplied by √2, a trapezoidal trench or a V-shaped groove penetrating the silicon wafer can be formed.

  In this case, the etching rate is determined by the concentration of the aqueous solution, the temperature of the solution, the type of additive, the amount of additive added, and the like. There is a method in which an etching time for obtaining a desired etching depth is set based on this etching rate, and processing is performed as time etching.

FIG. 9 is a diagram showing a method for detecting an etching end point by forming a monitor groove in a silicon wafer and penetrating the monitor groove. This is disclosed in Patent Document 1.
Anisotropic etching is performed with an alkaline solution from both sides of the silicon wafer 65. A groove 66 for forming a diaphragm of the pressure sensor is formed on one etched surface (back surface). Further, three types (67a, 67b, 67c) of monitor grooves 67 for detecting the depth of the grooves 66 are formed on the other surface (front surface). The opening widths 68a, 68b, 68c of the monitor grooves 67a, 67, 67c are increased in this order. As shown in FIG. 9, the wider the opening, the deeper the etching depth, and the etching depth increases in the order of the monitor grooves 67a, 67b, 67c. The monitor groove 67c is connected to and penetrates the groove 66 formed from the back surface. Further, the etching operation is stopped where the monitor groove 67a is not connected to the groove 66. The monitor groove 67b is a monitoring groove. In this way, the variation in the thickness T (diaphragm region) of the remaining film at the bottom of the groove 66 is determined by the difference between the remaining film thickness T of the groove 66 and the depth T1 of the monitor groove 67c (T−T1). It can be:

  FIG. 10 is a diagram showing a method for detecting the end point of etching when the monitor chip penetrates. This is the method disclosed in Patent Document 2. A monitor chip 80 for detecting the end point of etching is prepared. The thickness L1 of the monitor chip 80 is the same as the depth d of the groove 72 formed in the silicon wafer 71. The silicon wafer 71 and the monitor chip 80 are etched simultaneously. By completing the etching operation when the concave groove 82 of the monitor chip 80 passes, a groove 72 having a desired depth is formed in the silicon wafer 71. In the figure, reference numerals 73 and 81 denote mask materials for forming the grooves 72 and 82.

Japanese Patent Application Laid-Open No. 64-67976 (FIG. 1E) Japanese Patent Laid-Open No. 3-6824 (FIG. 1 (b))

  However, in the anisotropic etching with an alkaline solution as shown in FIG. 8, the etching rate is always constant due to the change in the concentration of the aqueous solution due to the evaporation of moisture, the consumption of additives, etc. due to the etching in a heated state. Not change. Therefore, when the time etching based on the etching rate data acquired in advance is performed, the depth of the groove varies and a highly accurate groove cannot be formed.

  In the method shown in FIG. 9 (Patent Document 1), if the difference (T−T1) between the depth T1 of the monitor groove 67a and the thickness T of the remaining film in the groove 66 is made small, it becomes difficult to determine the etching end point. In order to avoid this, when the difference is increased, the depth of the groove 66 formed in the silicon wafer 65 varies greatly.

  FIG. 10 (Patent Document 2) shows a method of simultaneously etching the silicon wafer 71 and the etching end detection chip 80 and stopping the etching operation when the concave groove 82 of the etching end detection chip 80 penetrates. It is shown. In this method, since the time of penetration is judged and then the etching operation is stopped, a time lag is likely to occur between the penetration time and the etching operation stop time. Therefore, the groove 72 formed in the silicon wafer 71 is likely to be over-etched.

  Further, Patent Document 1 and Patent Document 2 describe that the etching operation is stopped at the time of penetration of the monitor and a groove having a desired depth is formed in the silicon wafer. However, as in the present invention, the etching rate is calculated from the penetration time of the monitor, and the additional etching time is calculated from this etching rate. A method for controlling the depth of the groove with high accuracy by performing this additional etching is not described.

  An object of the present invention is to provide a semiconductor device manufacturing method and a semiconductor device manufacturing apparatus capable of controlling the depth of a groove formed in a silicon wafer with high accuracy by solving the above-described problems.

In order to achieve the above object, according to the first aspect of the present invention, a silicon wafer and a monitor wafer made of silicon are simultaneously immersed in an etching solution to form a groove in the silicon wafer. Etching the first location and the second location forming the groove of the monitor wafer, penetrating the second location, calculating the etching rate from the penetration time of the second location, and the etching rate A step of calculating an additional etching time for setting the depth of the first portion of the silicon wafer to a predetermined depth using the method, and etching the first portion of the silicon wafer with the additional etching time. Making the first location a predetermined depth;
The manufacturing method of the semiconductor device containing this.

  Further, according to the invention of claim 2, the thickness of the monitor wafer is the same as the thickness of the silicon wafer, and the monitor wafer is etched from both sides. Good to be done.

  According to the invention described in claim 3, the monitor wafer is half the thickness of the silicon wafer, and the monitor wafer is etched from one side. Good.

According to the invention described in claim 4, a monitor chip may be used instead of the monitor wafer in the invention described in claim 1.
According to the invention described in claim 5 of the claims, in the invention described in claim 1, the monitor wafer is abolished and is the same as the monitor wafer in a place other than the chip utilization area of the silicon wafer. A monitor unit that works may be provided.

According to the invention described in claim 6, the etching treatment tank for storing an etching solution for etching the silicon wafer and the monitor wafer made of silicon, and the vertical movement of the silicon wafer and the monitor wafer are supported. A support / movable part, a laser light projecting part composed of fibers disposed on both sides of the monitor wafer, a groove penetration detecting part having a light receiving part, a light transmitting / receiving part for emitting / receiving the laser light, A monitor penetrating time monitoring unit that receives a signal from the groove penetrating detection unit and measures the time that the groove of the monitor wafer penetrates, and an etching that receives a signal from the monitor penetrating time monitoring unit and calculates an etching rate from the penetrating time of the monitor wafer When performing additional etching in response to a signal from the rate calculation unit and the etching rate calculation unit An etching time counting unit for calculating the function, a function for operating the support / movable unit in response to a signal from the etching time counting unit, a function for transmitting a series of operation start signals to the support / movable unit, and the light transmitting / receiving unit And a control unit having a function of transmitting an operation start signal and an operation end signal to the semiconductor device manufacturing apparatus.
[Action]
A monitor wafer that penetrates in a time shorter than the time for forming the groove in the silicon wafer is prepared. Subsequently, the monitor wafer is etched with an alkaline solution simultaneously with the silicon wafer for forming the groove. An etching rate is obtained from the penetration time of the monitor wafer and the thickness before etching, and additional etching is performed using the etching rate.

  According to the present invention, the depth of the groove formed in the silicon wafer is controlled by the penetration time of the monitor wafer and the additional etching time. First, a monitor wafer that penetrates in a time shorter than the time for forming a groove having a desired depth in a silicon wafer is prepared, and this monitor wafer is etched simultaneously with the silicon wafer. Subsequently, the etching rate is calculated from the time (penetration time) through which the monitor wafer penetrates. Subsequently, an additional etching time is determined from this etching rate. Furthermore, by etching the silicon wafer with this additional etching time, it is possible to accurately form a groove having a desired depth in the silicon wafer by real etching without relying on prior data regarding an experimental etching rate.

  Further, since this etching is anisotropic etching with an alkaline solution, the silicon wafer can be batch-processed (multiple batch processing).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a method of manufacturing a semiconductor device according to a first embodiment of the present invention, and FIGS. It is principal part sectional drawing with which the masking material which has an opening part was coat | covered on both surfaces of the monitor wafer. It is a figure which shows a mode that a groove | channel is formed in a silicon wafer and a monitor wafer. It is principal part process sectional drawing of the semiconductor device of 2nd Example of this invention. It is a figure which shows a mode that a groove | channel is formed in a silicon wafer and a monitor wafer. It is a principal part block diagram of the manufacturing apparatus of the semiconductor device of 3rd Example of this invention. It is a block diagram of the manufacturing apparatus of the semiconductor device of 3rd Example of this invention. It is a schematic diagram of wet anisotropic etching of silicon with an alkaline solution. It is a figure which shows the conventional method which forms the monitor groove | channel in a silicon wafer and detects the end point of an etching by this monitor groove | channel penetrating. It is the figure which showed the conventional method of detecting the end point of an etching because a monitor chip penetrates.

  Next, the embodiment will be specifically described in the following examples.

  FIG. 1 shows a method of manufacturing a semiconductor device according to a first embodiment of the present invention. FIGS. 1A to 1C are cross-sectional views of essential parts shown in the order of steps. This is an example where the groove (second portion 24) of the monitor wafer 22 is formed from both sides and penetrates. The monitor wafer 22 may be a silicon chip (silicon piece).

  First, in FIG. 1A, a plurality of silicon wafers 21 and a monitor wafer 22 housed in a groove penetration detection unit 3 and a cassette (not shown) are moved together in an etching processing tank 1 by a support / movable unit 2 to produce an etching solution. 11 soak. The etching treatment tank 1 contains an alkaline solution. The monitor wafer 22 is sandwiched between the light projecting end and the light receiving end of the groove penetration detecting unit 3.

  The etching tank 1 is an alkali-resistant etching tank such as polytetrafluoroethylene or polypropylene. The groove penetration detection unit 3 is a light projecting end of the fiber 9a for projecting laser light and a light receiving end of the fiber 9b for receiving light, and is arranged so as to sandwich the monitor wafer 22 from both sides. Further, the support / movable unit 2 has a function of supporting the wafers 21 and 22 and moving up and down. In this embodiment, the groove penetration detection unit 3 is also moved up and down at the same time.

  Next, in FIG. 1B, the first portion 23 of the silicon wafer 21 and the second portion 24 of the monitor wafer 22 are etched. The first place 23 and the second place 24 are places where grooves are formed. Subsequently, the light transmission / reception unit 4 operates in response to a command from the control unit 8, and laser light is incident from the light transmission / reception unit 4 to the light projecting side fiber 9 a. The incident laser light is sent to the groove penetration detection unit 3 through the fiber 9a, and is projected from the projection end of the groove penetration detection unit 3 to the second location 24 (groove) of the monitor wafer 22. The projected laser light passes through the second portion 24 of the monitor wafer 22 and is sent to the light transmission / reception unit 4 through the light receiving side fiber 9b. 4 is input. An output signal from the light transmitting / receiving unit 4 is input to the monitor penetration time monitoring unit 5.

  The monitor wafer 22 penetrates the second portion 24 by double-sided etching. The presence or absence of this penetration is determined by whether or not the output signal intensity (the intensity of the received laser beam) has reached 100%. The time required for this penetration (penetration time) is measured by the monitor penetration time monitoring unit 5. The etching rate calculation unit 6 calculates the etching rate from the measured penetration time and half the thickness of the monitor wafer 22 before etching (the etching is performed from both sides). Subsequently, an additional etching time for setting the depth of the groove of the first portion 23 of the silicon wafer 21 to a predetermined depth using the etching rate calculated by the etching rate calculation unit 6 is counted as an etching time. Calculated in part 7. In this additional etching time, the first portion 23 of the silicon wafer 21 is etched to a predetermined depth.

  Next, in FIG. 1C, the support / movable unit 2 is operated by a signal from the control unit 8 when the additional etching time ends. With this operation, the silicon wafer 21, the monitor wafer 22, and the groove penetration detection unit 3 are pulled up from the etching solution 11, and the etching is completed. At this time, it is possible to prevent the first portion 23 from being over-etched by calculating the additional etching time including the time until the silicon wafer 21 is completely lifted from the etching solution 11. In FIG. 1, reference numeral 10 denotes an etching time control unit.

FIG. 2 is a cross-sectional view of a main part in which both sides of the monitor wafer are covered with a masking material having openings.
The thickness of the monitor wafer 22 used here is the same as the thickness of the silicon wafer 21. The monitor wafer 22 is covered on both sides with a masking material 25 (insulating film), and etching is performed from both sides. The masking material 25 is opened at the second location 24. The masking material 25 may be made of any material as long as it has resistance to the etching time required to obtain a desired etching depth, such as an organic film such as a resist, silicone, polyimide, or epoxy, an oxide film, a nitride film, or the like. For example, a metal film.

FIG. 3 is a diagram showing how grooves are formed in the silicon wafer and the monitor wafer.
The diagram on the left is a diagram of the monitor wafer 22, the center is a diagram showing the relationship between etching time and output signal intensity, and the diagram on the right is a diagram of the silicon wafer 21. It shows a state in which etching proceeds from FIG. Etching is started in FIG. 6A, etching proceeds in FIG. 4B, the monitor wafer penetrates through etching in FIG. 4C, and additional etching is performed in FIG. Grooves are formed in the silicon wafer 21.

  As shown in FIG. 3C, the output signal intensity increases as etching progresses, and the output signal intensity reaches 100% when the monitor wafer 22 penetrates. The point in time when the output signal intensity reaches 100% indicates that the etched portion (first portion 23) of the silicon wafer 21 has penetrated.

  In addition, when the 1st location 23 which forms a groove | channel in the silicon wafer 21 is a non-diffusion area | region, it is good to use a non-diffusion wafer as the monitor wafer 22 in order to make an etching rate the same.

  As described above, since the etching is performed with an alkaline solution, the crystallinity of the etched surface of the groove sidewall is good. Moreover, since it is wet etching, a large number of silicon wafers can be accommodated in a cassette and simultaneously etched (batch processing).

  Further, the penetration time can be extended by bringing the etching depth that the monitor wafer 22 penetrates closer to the depth of the groove formed in the silicon wafer 21. The calculation accuracy of the etching rate can be increased by increasing the penetration time. As a result, the groove of the silicon wafer 21 can be formed with an accurate depth.

  Here, the method using the monitor wafer 22 has been described. However, the monitor wafer may be abolished, and a monitor portion having the same function as that of the monitor wafer 22 may be formed at a place where the silicon wafer 21 becomes unnecessary. The unnecessary portions are, for example, a scribe line region and a peripheral region where a regular chip of a wafer is not formed.

  FIG. 4 is a cross-sectional view showing the principal part of the semiconductor device according to the second embodiment of the invention. The difference from the first embodiment is that the thickness of the monitor wafer 30 is half of the thickness of the silicon wafer 21, and the monitor wafer 30 is further etched from one side to penetrate the groove.

A method for producing the monitor wafer 30 having a thickness half that of the silicon wafer 21 will be described. Here, a general back wrap device was used as an example.
In the method using the back wrap, a protective tape is attached to the surface opposite to the surface to be polished, and then the polishing surface is formed with a back wrap apparatus so that the wafer thickness is half the thickness of the silicon wafer 21. Grind.

  After polishing, either the polished surface or the non-polished surface may be used, so that the monitor wafer 30 is covered with a masking material 25 having an opening so that only the second portion 24 penetrating through the photoetching technique is selectively etched. Coating. The material of the masking material 25 used is the same as that described in the first embodiment.

FIG. 5 is a diagram illustrating a state in which grooves are formed in the silicon wafer and the monitor wafer.
In FIG. 5, the left side is a diagram of the monitor wafer 30, the center is a diagram showing the relationship between the etching time and the output signal intensity, and the right side is a diagram of the silicon wafer 21. It shows a state in which etching proceeds from FIG. Etching is started in FIG. 4A, etching proceeds in FIG. 2B, the monitor wafer 30 penetrates through etching in FIG. 2C, and a desired depth is obtained by additional etching in FIG. Are formed in the silicon wafer 21.

6 and 7 are a block diagram and a main part configuration diagram of a semiconductor device manufacturing apparatus according to a third embodiment of the present invention.
The manufacturing apparatus 100 is disposed so as to sandwich the etching wafer 1 between the etching treatment tank 1 into which an etching solution is put, the silicon wafer 21, the monitor wafer 22, and the groove penetration detection unit 3 to be moved up and down, and the monitor wafer 22. And a groove penetration detecting unit 3. The groove penetration detection unit 3 emits laser light to the light projecting side fiber 9a and receives the laser light from the light receiving side fiber 9b.

Further, it comprises a light transmitting / receiving unit 4 that emits and receives laser light to the light projecting side fiber 9a and the light receiving side fiber 9b of the groove penetration detecting unit 3.
In addition, it includes a monitor penetrating time monitoring unit 5 that receives a signal from the light transmitting / receiving unit 4 and measures a penetrating time at the second location 24 of the monitor wafer 22.

  In addition, the etching rate calculation unit 6 that receives the signal from the monitor penetration time monitoring unit 5 and calculates the etching rate from the thickness (or half the thickness) of the monitor wafer 22 before etching and the penetration time of the second portion 24. Consists of. The light transmitting / receiving unit 4 is composed of, for example, a laser diode and a light receiving diode. However, the laser diode may be a light emitting diode (LED) or a visible light diode.

  Also, from the etching time counting unit 7 that receives the signal from the etching rate calculating unit 6 and calculates the additional etching time, and the control unit 8 that transmits the signal from the etching time counting unit 7 to the support / movable unit 2. Become.

The etching time control unit 10 includes a light transmission / reception unit 4, a monitor penetration time monitoring unit 5, an etching rate calculation unit 6, an etching time counting unit 7, and a control unit 8.
The control unit 8 instructs the support / movable unit 2 to move up and down, and instructs the emission of the laser light from the light transmitting / receiving unit 4.

In FIG. 6, the groove penetration detection unit 3 moves up and down simultaneously with the wafers 21 and 22, but there are cases where only the wafers 21 and 22 are moved up and down by being fixed to the etching processing tank 1.
6 includes a light projecting end portion and a light receiving end portion of the fibers 9a and 9b. The light emitting element and the light receiving side fiber 9b are disposed at the light projecting end portion of the light emitting side fiber 9a. A light receiving element may be arranged at the light receiving end of the light transmitting / receiving section 4.

  In FIG. 7, the numbers in the circles indicate signals and the order of operations when the manufacturing apparatus 100 operates.

DESCRIPTION OF SYMBOLS 1 Etching processing tank 2 Supporting / movable part 3 Groove penetration detection part 4 Transmitting / receiving light part 5 Monitor penetration time monitoring part 6 Etching rate calculation part 7 Etching time counting part 8 Control part 9a Light emitting side fiber 9b Light receiving side fiber 10 Etching Time control unit 11 Etching solution 21 Silicon wafer 22, 30 Monitor wafer 23 First location 24 Second location 25 Masking material 100 Manufacturing apparatus

Claims (6)

A silicon wafer and a monitor wafer made of silicon are immersed in an etching solution at the same time, and a first portion for forming the groove of the silicon wafer and a second portion for forming the groove of the monitor wafer are etched, and the second portion is etched. A step of penetrating;
Calculating an etching rate from the penetration time of the second location;
Calculating an additional etching time for making the depth of the first portion of the silicon wafer a predetermined depth using the etching rate;
Etching the first portion of the silicon wafer with the additional etching time to bring the first portion to a predetermined depth;
A method for manufacturing a semiconductor device, comprising: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the thickness of the monitor wafer is the same as the thickness of the silicon wafer, and the monitor wafer is etched from both sides. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the thickness of the monitor wafer is half that of the silicon wafer, and the monitor wafer is etched from one side thereof. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a monitor chip is used instead of the monitor wafer. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the monitor wafer is abolished and a monitor unit that functions in the same manner as the monitor wafer is provided at a place other than the chip utilization area of the silicon wafer. An etching tank for containing an etching solution for etching a silicon wafer and silicon monitor wafer, a support / movable part for supporting and moving the silicon wafer and the monitor wafer up and down, and fibers disposed on both sides of the monitor wafer A groove penetrating detection unit having a laser light projecting unit and a light receiving unit, a light transmitting / receiving unit emitting and receiving the laser light, and a time for the groove of the monitor wafer to pass through the signal of the groove penetrating detection unit. Monitor penetrating time monitoring unit for measuring, etching rate calculating unit for calculating an etching rate from the penetrating time of the monitor wafer in response to a signal from the monitor penetrating time monitoring unit, and additional etching in response to a signal from the etching rate calculating unit Etching time counting unit for calculating time and the etching A function for operating the support / movable unit upon receiving a signal from the inter-counter unit, a function for transmitting a series of operation start signals to the support / movable unit, and an operation start signal and an operation end signal for the light transmitting / receiving unit. And a control unit having a function.